etailed Design Plain for the construction of Khan Younis ... - UNDP

UNDP/PAPP 

PROVISIONS OF CONSULTANCY SERVICE FOR THE 

DETAILED DESIGN FOR THE CONSTRUCTION OF KHAN 

YOUNIS WASTEWATER TREATMENT PLANT IN GAZA STRIP 

DETAILED DESIGN 

JUNE, 2010 

FINAL 

N° 1 31 0076 – R4 – FINAL – V3

UNDP / PAPP 

DETAILED DESIGN FOR THE CONSTRUCTION OF KHAN YOUNIS WASTEWATER TREATMENT PLANT IN GAZA STRIP 


CONTENTS 

0. ADDENDUM.................................................................................................................2 

0.1. Answers to the UNDP’s comments dated 12th april 2010 ..............................................2 

0.1.1. Sheet 1- Details Design Report...........................................................................................................2 

0.1.2. Sheet 2 – Drawings............................................................................................................................16 

0.1.3. Sheet 3- Comments of PWA and CWMU..........................................................................................32 

0.2. Answers to the UNDP’s comments dated 12th june 2010 ............................................43 

0.2.1. Sheet 1- Details Design Report.........................................................................................................43 

0.2.2. Sheet 2 – Drawings............................................................................................................................46 

1. GENERAL..................................................................................................................59 

1.1. Reminder...........................................................................................................................59 

1.1.1. Background to the Project................................................................................................................59 

1.1.2. Project Scope and Expected Output................................................................................................60 

1.2. Treatment objectives .......................................................................................................61 

1.2.1. Inlet flows and loads .........................................................................................................................61 

1.2.2. Treated effluent quality requirements .............................................................................................63 

1.3. Project components.........................................................................................................64 

2. WWTP PROCESS JUSTIFICATION..........................................................................66 

2.1. Raw effluent flow measurement and inlet structure .....................................................66 

2.2. Pretreatment of effluents.................................................................................................66 

2.2.1. Fine screening ...................................................................................................................................66 

2.2.2. Degreasing and degritting ................................................................................................................68 

2.3. Secondary effluent treatment..........................................................................................72 

2.3.1. Treatment principles and design loads and flows .........................................................................72 

2.3.2. Aeration tanks....................................................................................................................................73 

2.3.3. Air production ....................................................................................................................................78 

2.3.4. Degassing and distribution ..............................................................................................................80 

2.3.5. Clarifiers .............................................................................................................................................81 

2.4. Tertiary treatment.............................................................................................................82 

2.4.1. Intermediate pumping station ..........................................................................................................82 

2.4.2. Sand filters .........................................................................................................................................82 

2.4.3. UV disinfection...................................................................................................................................88 

2.4.4. Treated effluent outlet pumping station..........................................................................................88 

2.4.5. Industrial water ..................................................................................................................................89 

2.4.6. Treated effluent metering..................................................................................................................90 

2.5. Sludge treatment..............................................................................................................90 

2.5.1. Sludge pit ...........................................................................................................................................90 

2.5.2. Thickeners..........................................................................................................................................91 

2.5.3. Drying beds ........................................................................................................................................93 

2.5.4. Composting area ...............................................................................................................................94 

2.6. Odour treatment ...............................................................................................................96 

2.6.1. Moisture..............................................................................................................................................96 

2.6.2. Air........................................................................................................................................................97 

SOGREAH / UG GAZA - N°1 31 0076_R4/JLA_PEN/ JUNE 2010 

PAGE A




2.6.3. Temperature .......................................................................................................................................97 

2.6.4. Biofilter design parameters ..............................................................................................................97 

3. PLANT DESCRIPTION ..............................................................................................99 

3.1. General..............................................................................................................................99 

3.2. Connection pipes .............................................................................................................99 

3.2.1. Laying conditions............................................................................................................................100 

3.2.2. Connections to structures ..............................................................................................................100 

3.3. Preliminary treatment ....................................................................................................101 

3.3.1. Flow metering ..................................................................................................................................101 

3.3.2. Screening..........................................................................................................................................101 

3.3.3. Grit/grease removal .........................................................................................................................102 

3.4. Aeration tanks ................................................................................................................103 

3.4.1. Anoxic zone......................................................................................................................................103 

3.4.2. Aerated zone ....................................................................................................................................103 

3.4.3. Air production plant ........................................................................................................................104 

3.5. Clarification ....................................................................................................................105 

3.5.1. Distributor DW2................................................................................................................................105 

3.5.2. Degazing structure ..........................................................................................................................105 

3.5.3. Clarifiers ...........................................................................................................................................105 

3.5.4. Sludge sump ....................................................................................................................................106 

3.5.5. Scum pit............................................................................................................................................106 

3.6. Tertiary treatement.........................................................................................................106 

3.6.1. General..............................................................................................................................................106 

3.6.2. Intermediate lifting station..............................................................................................................107 

3.6.3. Sand filters .......................................................................................................................................107 

3.6.4. Disinfection ......................................................................................................................................107 

3.6.5. Filter washing...................................................................................................................................107 

3.6.6. Treated effluent pumping station...................................................................................................108 

3.6.7. Industrial water ................................................................................................................................108 

3.6.8. Gravity Thickeners...........................................................................................................................108 

3.6.9. Sludge drying...................................................................................................................................109 

3.6.10. Sludge composting .........................................................................................................................110 

3.7. Biological fitter – Odour treatment ...............................................................................111 

3.8. Remote control and supervision...................................................................................111 

3.8.1. Introduction......................................................................................................................................111 

3.8.2. SCADA System features .................................................................................................................113 

3.8.3. General overview control philosophy............................................................................................117 

3.9. Electrical equipment ......................................................................................................141 

3.9.1. Power supply....................................................................................................................................141 

3.9.2. Required power for KYWWTP.........................................................................................................142 

3.9.3. Main Power Substations and switchgears ....................................................................................146 

3.9.4. Electrical Generators:......................................................................................................................149 

3.9.5. Lightening: .......................................................................................................................................149 

3.9.6. Earthing: ...........................................................................................................................................149 

3.10. Civil works ......................................................................................................................149 

3.10.1. General principles and design criteria...........................................................................................150 

3.10.2. Workshop .........................................................................................................................................158 

3.10.3. Offices building................................................................................................................................159 

3.10.4. Process structures ..........................................................................................................................166 

3.10.5. Roads and fencing...........................................................................................................................168 


PAGE B




3.11. Pressure pipes and others structures..........................................................................170 

3.11.1. Effluent pressure line ......................................................................................................................170 

3.11.2. Pressure line from WWTP to infiltrations basins and sea outfall ...............................................174 

3.11.3. Infiltrations basins...........................................................................................................................177 

3.11.4. Sea outfall.........................................................................................................................................183 

4. INVESTMENT COSTS EVALUATION.....................................................................185 

4.1. WWTP..............................................................................................................................185 

4.1.1. General principles............................................................................................................................185 

4.1.2. Dayworks..........................................................................................................................................185 

4.1.3. Origin of Unit prices ........................................................................................................................186 

4.1.4. Summary...........................................................................................................................................186 

4.2. Treated effluent pressure line .......................................................................................188 

4.3. Infiltration basins ...........................................................................................................188 

4.4. Global projet costs.........................................................................................................189 

5. RUNNING COSTS ...................................................................................................191 

5.1. WWTP..............................................................................................................................191 

5.1.1. Energy cost ......................................................................................................................................191 

5.1.2. Waste disposal cost ........................................................................................................................191 

5.1.3. Personnel cost .................................................................................................................................192 

5.1.4. Maintenance cost.............................................................................................................................192 

5.1.5. Total operating cost KY WWTP ......................................................................................................193 

5.2. Treated effluent pumping and discharge .....................................................................193 

5.2.1. Energy cost ......................................................................................................................................193 

5.2.2. Maintenance cost.............................................................................................................................194 

5.2.3. Personnel cost .................................................................................................................................194 

5.3. Overall running cost ......................................................................................................195 

6. PROJECT IMPLEMENTATION ...............................................................................196 

6.1. Biddings procedure .......................................................................................................196 

6.2. Contract packaging........................................................................................................198 

6.3. Planning ..........................................................................................................................200 

6.3.1. Pipes to laid......................................................................................................................................200 

6.3.2. General implementation schedule .................................................................................................201 


PAGE C




LIST OF FIGURES 

FIG. 1.GENERAL PROJECT LAYOUT .................................................................................................................................65 

FIG. 2.ANNUAL MASS BALANCE FOR SLUDGE COMPOSTING AT KY WWTP .......................................................................95 

FIG. 3.POWER SUPPLY TO KY WWTP SITE-POINT OF ELECTRICITY CONNECTION.............................................................141 

FIG. 4.TYPICAL SECTION IN FOR THE HEAVY ROADS........................................................................................................169 

FIG. 5.TYPICAL SECTION IN FOR THE LIGHT ROADS.........................................................................................................170 

FIG. 6.SECTIONS OF THE EFFLUENT PRESSURE LINE.......................................................................................................172 

FIG. 7.SYSTEM CURVES OF THE EFFLUENT PIPE TO THE INFILTRATION BASIN AND TO THE SEA..........................................174 

FIG. 8.SEA OUTFALL.....................................................................................................................................................184 

LIST OF APPENDICES 

APPENDIX 1 

APPENDIX 2 

APPENDIX 3 

APPENDIX 4 

APPENDIX 5 

APPENDIX 6 

APPENDIX 7 

APPENDIX 8 

APPENDIX 9 

DESIGN FLOWS AND LOADS 

WWTP HYDRAULIC CALCULATIONS 

PIPES HYDRAULIC CALCULATIONS 

CIVIL STRUCTURES CALCULATIONS 

ELECTRICAL CALCULATIONS 

BILL OF QUANTITIES 

EQUIPMENT LISTS 

SITE INVESTIGATIION REPORTS 

DRAWINGS 

oOo 


PAGE D

PROJECT GENERAL INFORMATION 

Consultancy services for the detailed design for the 

Project Name 

construction of Khan Younis wastewater treatment plant 

in Gaza strip 

Project code PAL10 - 00047395 

The United Nations Development Programme/ 

Client 

Programme of Assistance to the Palestinian People 

(UNDP/PAPP) 

Funded By 

Government of Japan 

Beneficiary 

Khan Younis Municipality – CMWU - PWA 

Consultant 

Joint venture consultant : 

SOGREAH Consultants & Universal Group Gaza 

Starting date 02/11/2008 

SOGREAH / UG GAZA - N°1 31 0076_R4/JLA_PEN/ JUNE 2010 PAGE 1

0. 

ADDENDUM 

0.1. ANSWERS TO THE UNDP’S COMMENTS DATED 12TH APRIL 2010 

0.1.1. SHEET 1- DETAILS DESIGN REPORT 

1. Page A to c, 1.2. Correcting “Treatment Objectifs” to “Treatment Objectives” revising and correcting 

similar phrases. Modifications taken into account in the DD report 

Chapter 1 

2. Page 1, clause1.1.1, background to the project, second paragraph, According to information 

gathered from Khan Younis Municipality, 83%....” The reference of these information and figures 

shall be checked if it is according to PWA or CMWU as they are the sector regulator and service 

provider not Kahn Younis Municipality. Please check the KY WWTP’s preliminary design done by 

Plancenter consultant for the PWA. Information gathered form Khan Younis Municipality and 

stipulated in final and approved Inception Report and Initial Design Report. 

3. Page 1, clause1.1.1, background to the project, third paragraph, check and redraft as the waste 

water is transported to the storm water lagoon and then to the western temporary lagoons and the 

waste water has been already discharged to the sea, not planned. Modification taken into 

account in the DD report 

4. Page 2, clause 1.1.2., Project scope and expected output, first paragraph, to avoid misinterpretation 

redrafting “A joint Venture Consortium …. “Assigned” to “Contracted by UNDP/PAPP for the 

assignment of ……” as it was a competition bid not assignment. Take into account in the DD 

report. 

5. Page 3, clause 1.2.1, Inlet Flow and loads, 1st paragraph; the terminology of effluent and influent 

need to be distinguished for more clarity. And the same in clause 2.1 in page 8 and different places 

in the text. Influent is used to define the wastewater enters into the wastewater treatment 

plant or into a works (for example: aeration tank, grit and grease removal tank). Effluent is 

used to define wastewater. 

6. Page 3, clause 1.2.1, Inlet Flows and loads, third paragraph, exact length of the pressure line “about 

4750 m” is now required reference to the done survey. Modifications taken into account in the 

DD report 

7. Page 3, clause 1.2.1, revising the last comment concerning the pump station and the pressure line 

reference to Task 1 , item 3, of the TOR. Reference to the TOR, Task 1, item 3, the Consultant 


shall only review and assess the design of the existing PS#8 and its effluent pressure line 

towards the proposed WWTPand make the necessary design modification to handle 

hydraulic flow for Phase 1 and 2. The detailed design of the pumping stations and pressure 

line is not included into the Task 3. 

8. Page 4, clause 1.2.1., Inlet Flows and Loads, page 4, 1st paragraph, Septage flow rate of 2,24 

m3/capita/year, Documented Reference of Khan Younis Municipality should be attached for 

documentation. The Head of wastewater department of Khan Younis contacted by UG, gave 

us the following information: 1) the average number of septage trucks evacuated monthly by 

the Municipality owned trucks is 2000; 2) the privately owned vacuum trucks evacuate one 

fourth of the quantity evacuated by the Municipality owned trucks (i.e. 500 trucks/month); 3) 

the volume of the tank is 6 m3. So the volume of septage is 15000 m3/month, thus 180 000 

m”/day. The unconnected population of Khan Younis city in 2008 is 74 878 persons. The 

septage flow rate is 2,4 m”/cap/year. 

9. Page 4, Inlet Flow, is the rainwater load that might be expected during the rainy season inside the 

plant included. Inlet flow is based on domestic water consumption rate and the return rate to 

sewer plus the industrial water consumption and the return rate to sewer as described in the 

Appendix 1. These calculations were approved in the Initial Design Report, some 

modification was taken into account in the Detailed design indicated in the Appendix 1 

10. Chapter 1, mentioning the selected treatment process in the report. Modification taken into 



Chapter 2 

11. Page 8, chapter 2, a paragraph may be included to clarify in the design report why there is only 

sand screening and does not include coarse screening. Take into account into the DD report 

12. Page 8, clause 2.1, raw effluent flow measurement.., comparing the peak flow velocity of 2610 and 

950 m3/hr with peak flow velocity of phase 2 in the table of page 15. In table of page 15, peak 

flow velocity take into account the backflows not in page 8. 

13. Page 9, clause 2.2.1. Fine screening, screening and mesh spacing of 10 mm to be revised for more 

fine spacing as discussed in the DD presentation. The mesh spacing of 10 mm is usually used 

for fine screening on wastewater treatment plant, reduce the mesh spacing will increase 

difficulties during operation and maintenance. We propose to install mesh spacing of 8 mm. 

Modifications taken into account in the DD report. 

14. Page 10, clause 2.2.1. Fine screening, comparing and checking the compacting rate of 35% with 

the initial design report of inclination degree of 35. In the detailed design the fine screens are 

installed vertically, not inclination. Moreover, the screenings are conveyed by a shaft less 

spiral conveyor towards a screenings compacting device (compacting rate 35%) and then 

deposited into a 15 m3 skip. 

15. Page 10,11, clause 2.2.2 Degreasing and Regretting, is the longitudinal tank and parallel line are 

symmetrical, with similar volume of 214.5 m3, as in initial design report the volume of phase I and 

phase 2 have different volumes of 390 and 585 m3. The inlet flow has been adjusted between 

the initial design report and the detailed design and then the volume of tank. 

16. Page 12, clause 2.2.2 Degreasing and Regretting, revising the specific grit quantity from tanks, 100 

kg /1000m3 raw effluent, to be checked and verified for SAND availability in the raw sewage as 

discussed in the DD presentation. In the Final initial design report the grit quantity specific 

was 15l/PE/year. Based in this data (approved in the initial design report) the grit quantity is 

similar to the quantity defined in the detailed design page 13 with the rate 100 kg/1000 m3 

raw effluent. So the grit quantity from the tanks is correct. 

17. Page 16, clause 2.3.2.2 Elimination of Nitrogen, last paragraph verifying the sequence and the 

location of anoxic zone in front of the aerated zone. The anoxic zone is situated in front of the 

aerated zone to achieve the required Nitrate Nitrogen effluent discharge quality by 

denitrification. 

18. Page 17, clause 2.3.2.2 Elimination of Nitrogen, in the table, in rows no. 5, no. 6, and no. 9, correct 

the numbering sequence of N4 = N1-N2-N3-N4, to be N5 = N1-….., etc.. check the figures of N6, 

N8 as well. Modifications take into account into the DD Report 

19. Page 18, clause 2.3.2.2 Elimination of Nitrogen, verify the accuracy of the equation of item 12, and 

the No.10 is repeated twice. Verify the multiplication of item 13. Modifications take into account 

into the DD Report 

20. Page 19, clause 2.3.2.6, The capacity of the aeration tank pump is 320m3/h. 4Pumps x 320= 

1280m3/h. If the pumps will work in parallel a correction factor shall be taken into consideration to 

balance between the required total capacity and the capacity of each pump. The choice of the 

capacity of the pump take into account the work in parallel 

21. Page 22, clause 2.3.3.3, compressors, is the compressor required discharge pressure of 880 mbar 

is the same as the head loss only. Yes, the head loss calculation tank into account singular 


and linear head loss on each component of the “air network” (feeders, branch pipes, trunk 

line, diffusers at 7.75m immersion height) as described in the table page 22. 

22. Page 22, clause 2.3.4 degassing and distribution, the surface are of the degassing tank specified, 

what is the depth of the tank? The water depth in the clarification tank is 3.5m, the depth of the 

clarification tank is 3.71m 

23. Page 23, clause 2.3.5, clarifiers, correct the total provided clarification surface area (3420 m) from m 

to m2. Modifications taken into account into the DD report 

24. Page 24, clause 2.4.1, intermediate pumping station, in the table, check the capacity of the pump 

unit flow of 1306 m3/h in comparison to the pumps total peak flow of 2231 m3/h and 3919 m3/h, 

i.e. the multiplication of the flow of 2 or3 pumps taking into consideration the adjustable flow factor 

for pumps working on parallel. The choice of the capacity of the pump take into account the 

work in parallel 

25. Page 26, clause, 2.4.2.1, dimensional design of sand filter, in the table; check the scour air inlet 

flow, 3030 Nm3/h, is it the same for phase 1 and Phase 2. In phase 1 and phase 2, only one 

sand filters is washed in the same time. The air scour rate during washing is 50 m3/h/m², so 

for one filter in washing the air scour capacity is 3030 Nm3/h. 

26. Page 26, clause 2.4.2.2, filter packing, second paragraph, check and clarify the filter medium height 

of 1.4 m is it the total height, in comparison to gravel height of 0.1 m and sand height of 1.4 m. the 

total height could be more than 1.4m; The gravel does not any effect on the filtration propose, 

its purpose is to distribute scour air and wash water across the entire surface of the filters 

and hence prevent stack effect. In the calculation note, the total filtration height taken into 

account is 1.4 m of sand. 

27. Page 27, clause 2.4.2.3, filtering cycles, first paragraph, the height of 1.3 m filtering material, check 

with the previous comment. The height of filtering material is 1.4m, correction taken into 

account in the DD report. 

28. Page 29, clause 2.4.2.5, backwashing pumping station, in the table check the unit capacity of the 

backwash pumps of 455m3/h and is the same capacity will be used for phase1 and phase 2. In 

phase 1 and phase 2, only one sand filters is washed in the same time. The rinsing water 

rate is 15m3/m²/h, so for one filter in washing the rinsing water capacity is 910 m3/h, 

whatever the phase. 

29. Page 30, clause 2.4.3, UV disinfection, fourth paragraph, second line, number of UV modules - 

phase 2 , correct (2 in parallel + 3 in series) to (3 in parallel + 3 in series) for total of 6. There is no 


error in the DD report, please check the scheme hereafter. 

30. Page 31, clause 2.4.4, treated effluent outlet pumping station, in the table check and clarify the unit 

pump capacity, for phase I and phase 2, and when pumping to the infiltration and the sea the 

capacity is different . I.e. make it clear which pumps will be installed actually for phase I, is it two 

different pumps with different capacity for the two modes. At the same time, it is noticed that the 

capacity of each unit for phase 2 is different than the capacity of the units of phase 1. I.e. are the 

pumps of phase I will be replaced in phase 2, or the pumps number will be expanded?. This clause 

need to be precisely clarified and classified as the data enclosed is a Bit confusing for the reader. 

Modifications are taken into account in the DD report 

31. Page 32, clause 2.4.5, Industrial water, in the table, is the capacity of the pumps include the flow 

capacity needed for irrigation for agricultural purposes inside KY WWTP is included. The irrigation 

network needed for agricultural of landscaping shall be included in the detailed design. The 

irrigation system in the TP site is designed to be into 3 zones, so that the 3 zones will be 

irrigated separately (one zone only in the same time) The irrigation will be once a day , 1 

hour for each zone , the pumping capacity needed is 40 m3 / hour , with a pressure =4 bar. 

The industrial water pumping station as indicated in the DD report is 75 m3/hour at a 

pressure of 5 bar. This mean that during irrigation the industrial water pumps is sufficient 

for irrigation. The pumps will be also used for the fire fittings in addition to their ordinary 

works (cleaning/ flashing. .... etc). Of course, during fire fighting the other usages will be 

stopped. 

32. Page 32, clause 2.4.6, Treated effluent metering, the effluent peak flow in phase 2 is 3684 m3/h, 

while in the table in page 31, it is 3558 m3/hr, please verify. The effluent peak flow in phase 2 is 

3 558 m3/h. 

33. Page 33, clause 2.5.1.2., excess sludge extraction, again pleas check the capacity of pumps of 80 

m3/h when working in parallel, taking into consideration flow factor when two or three pumps are 

working in parallel. The choice of the capacity of the pump take into account the work in 

parallel 

34. Page 34, clause 2.5.2, thickeners, delete the number 227 m2 in front of the phrase “Total Surface” 

as 227 m2 is for the unit surface only. Modification is taken into account in the DD report 

35. Page 35, clause 2.5.2, paragraph under the table, please verify that the pumps capacity for the 

thickened sludge of 80 m3/hr is distinguished that the pumps capacity for excess sludge of 80 

m3/hr in page 33. The excess sludge extraction pumps are a unit capacity of 80 m3/h. These 

pumps will allow transferring the excess sludge from sludge pits to gravity thickeners. The 

thickened sludge pumps are a unit capacity of 80 m3/h. these pumps will allow conveying 

the thickened sludge to the drying beds. 

36. Page 35, clause 2.5.3, drying beds, the drying area per unit is 450 m2 check and correct with page 

100, in clause 3.9.4.6, as it is mentioned that the drying pits each with area of around 600 m2. 

Modification taken into account in the DD report 


Chapter 3 

37. Page 38, clause 3.1. General, please redraft the first paragraph, especially “ most of which is 

occupied today by old solid waste dump cells” the solid waste is adjacent to KY WWTP site , but 

actually located outside the KY WWTP site. Please check and update the figures (171mx680 m) as 

survey and drawings. Modification taken into account in the DD report 

38. Page 39, clause 3.2, connection pipes, second paragraph, “a set of cast iron pipes of various 

diameters for all pressure pipes from the outlet of distributor DW1 as far as the clarifies” aeration 

tanks and thickeners; please check and verify the use of the cast iron pipes, their applicability and 

the method of connection. The same for concrete pipes. Please justify the choice of different 

materials for these pipes. Cast iron pipes are very adapted to wastewater and delivery 

pressure. Concrete pipes are very adapted to treated effluent and without pressure. Steel 

networks are not adapted due to corrosive problems and stainless steel is very expensive. 

39. Page 39, clause 3.2.1, laying conditions, third paragraph, small quantity of compacted fill above the 

soffit, the fill material shall be specified, and the 40 cm thick shall be compacted in two layers. The 

Fill materials is "clean sand " and the 40 cm can be filled in two layers 

40. Page 39, clause 3.2.2, connection to structures, second point “ … all pipes will be blocked in mass 

concrete through the slabs”, please elaborate, specify and make it more clear. Comment taken 

into account in the DD report 

41. Page 40, clause 3.3.2 screening, in the table check and verify the screen opening of 10 mm, verify 

concerning catching the excess sand in the waste water inflow as discussed in the meeting of 9 

Feb.2010 in the PWA. According to the comment 13, the mesh spacing of fine screening is 

reduced to 8 mm. concerning the sand please refer you to comment 16. 

42. Page 40, clause 3.3.2. screening, paragraph 4 “ All essential parts ( frame, shafts. Slide plates, side 

plats, clip, embedded parts) are made of 304L stainless steel or aluminum, check for the possibility 

of corrosion, stainless steel 316 shall be used to prevent corrosion. All essential parts (frame, 

shafts, slide plates, side plats, clip, embedded parts) are usually made of 304L stainless 

steel in wastewater treatment plant. The stainless steel 316 is very expensive compared to 

304L. We take into account your comment (304L to 316) and modify the BoQ accordingly. 

43. Page 41, clause 3.3.2, under the table, automatic screw compactor system, the casing are of 

special 250 HB steel and the support and flanges of 304 L stainless steel, check for the same 

above comment, and 316 stainless steel to be used to prevent corrosion. The casing are and the 

support and flanges are usually made of special 250 HB steel and 304L stainless steel 

respectively in wastewater treatment plant. The stainless steel 316 is very expensive 

compared to 304L We take into account your comment (304L to 316) and modify the BoQ 

accordingly. 

44. Page 41, clause 3.3.3, Grit /Grease Removal, automatic alternating scraper made of 304 L stainless 

steel, check for the same above comment, and 316 stainless steel to be used to prevent corrosion. 

Automatic alternating scraper is usually made of 304L stainless steel in wastewater 

treatment plant. The stainless steel 316 is very expensive compared to 304L. We take into 

account your comment (304L to 316) and modify the BoQ accordingly. 


45. Page 42, cluase3.4.1 anoxic zone, second paragraph. ”… two mixers with three 304L stainless 


Mixers are usually made of 304L stainless steel in wastewater treatment plant. The stainless 

steel 316 is very expensive compared to 304L. We take into account your comment (304L to 

316) and modify the BoQ accordingly. 

46. Page 43, clause 3.4.2, aerated zone, paragraph 1 and 2 under the tale the diffusers installed on 16 

304l stainless steel frames, and a quick coupling with the 16 plunging ND 160 304 L stainless steel 

pipes,… , check for the same above comment, and 316 stainless steel to be used to prevent 

corrosion. Diffusers are usually made of 304L stainless steel in wastewater treatment plant. 

The stainless steel 316 is very expensive compared to 304L. We take into account your 

comment (304L to 316) and modify the BoQ accordingly. 

47. Page 43, clause 3.4.3. air production plant, paragraph no 2, 3, check the” turbo-compressors” 

capacity of 19,000 Nm3/h. verify it with the nominal air flow of 18,000 Nm3/h in page 21 and the 

table in page 22. The nominal capacity of each turbo compressor is 18,000 Nm3/h. The 

modifications taken into account in the DD report. For the ND 600 304 L stainless steel pipes 

and other related pipes in contact with the waste water, check for the same above comment, and 

316 stainless steel to be used to prevent corrosion whereas appropriate. Pipes are usually made 

of 304L stainless steel in wastewater treatment plant. The stainless steel 316 is very 

expensive compared to 304L. We take into account your comment (304L to 316) and modify 

the BoQ accordingly. 

48. Page 43, clause 3.4.3. air production plant, 3rd paragraph, the number of compressors for phase 2 

is not mentioned. In phase 1, the number of compressors is 2 + 1 stand-by. In phase 2, the number 

of compressor is 3 + 1 stand-by. Modification taken into account in the DD report 

49. Is the air blowers in clause 2.4.2.7 page 29 are similar and can be classified as turbo- compressors 

or different, if so, pleas unify the title description. The air blowers described in the clause 2.4.2.7 

are not similar to the turbo compressors installed to air production in the aeration tank. These air 

blowers are installed in the tertiary treatment in order to provide scour air during filter 

washing. In phase 1 and 2, roots type blowers (1 + 1 stand-by) will be installed. 

50. Page 44, air production plant, first paragraph, hoods for conveying hot air from the motors outdoors 

can be installed in this project but not as an option. Please include. Modification taken into 


51. Page 45. Clause 3.5.4, sludge sump, first paragraph, check the diameter ND 300 valve for the sump 

pipe is compatible with the diameter of the pipe ND 600. The discharge pipes ND 300, are 

connected to the ND600 pipe as indicated in the drawing DD-CLA-M-003_B Plan View. 

52. Page 45. Clause 3.5.4, sludge sump, second paragraph, check and specify the pump capacity of 80 

m3/h is for each pumping unit. The excess sludge pumps (1 + 1 stand-by) are centrifugal pumps 

with a discharge unit of 80 m3/h. Modification taken into account in the DD report 

53. Page 45, clause3.6.1 Tertiary treatment, General, the last sentence, please re-draft the “infiltration 

tanks” to the “infiltration basins”. Modification taken into account in the DD report 


54. Page 46. Clause 3.6.2, Intermediate lifting station, second paragraph, check and specify the pump 

capacity of 1306 m3/h is for each pumping unit, as per the table of page 24. The unit capacity of 

the intermediate pumps is 1306 m3/h. Modification taken into account in the DD report 

55. Page 46, clause 3.6.3, sand filters, please check the depth and dimensions with comment no.22 

and page 26. The sand filter depth is 1.40 m, and the gravel depth is 0.1 m 

56. Page 47, clause 3.6.5, filter washing, third paragraph, For the ND 200 304 L stainless steel pipes 

and other related pipes in contact with the waste water, check for the same above similar comment, 

and 316 stainless steel to be used to prevent corrosion whereas appropriate. . Pipes are usually 

made of 304L stainless steel in wastewater treatment plant. The stainless steel 316 is very 



57. Page 47, clause 3.6.7, gravity thickeners, 1st paragraph, check the capacity of the recovery pumps 

45 m3/h in phase 1 and 73 m3/h in phase 2, and as set in page 35 of pump capacity of 80 m3/h. 

please verify and redraft for more clarity and to avoid confusion in the selection of the pump 

capacity. The same for the pump capacity of 132 m3/h in the second paragraph, and comparing it 

with pumps capacity of 80 m3/h as in page 33. The recovery pumps (1 + 1 standby sized for the 

final phase) with a variable discharge (45 m3/h in phase 1, 73 m3/h in phase 2). Clarification 

taken into account in the DD report. The pump capacity of 132 m3/h allow to transfer the 

water of the back flow pumping station to the head of the treatment process while the 

excess sludge pumps (unit capacity : 80 m3/h due to extraction duration : 10h/d) will pump 

from sludge pits to gravity thickeners. 

58. Page 48, cluase3.6.8, sludge drying, the last sentence…” sand layers in the drying beds need to be 

replaced regularly”, what is the time duration needed for the replacement? Please specify. The 

replacement of sand layers depends of operation and maintenance (sludge quality, …). 

59. Page 48, clause 3.6.9, sludge composting, second paragraph, a mixture of sludge …. will be 

composed using a front loader… is the loaders needed and similar equipment include in the 

summary cost estimates to be taken into consideration for resource mobilization. The same for the 

two front end loaders as set in the fourth paragraph of page 49. The same as for the vacuum trucks 

for grease removal. Modification taken into account in the BoQ 

60. Page 49, no details are mentioned in chapter 3 after clause 3.6 concerning the effluent pumping 

station 3 for more data and elaboration. Modification taken into account in the DD report. 

61. Page 50, clause 3.7.1.1. scope of works, 5th paragraph, please correct “instrumentation” to 

“instrumentation”. Modification taken into account in the DD report 

62. Page 51, clause 3.7.1.4, dispatch system hardware, last sentence, …“An outline drawing of the 

proposed SCADA system is provided attached”. Pleas attached here as it is not included. Drawing 

of proposed SCADA system is now included into the set of drawings. 

63. Page 54, clause 3.7.2.5 SCADA system database configuration, second paragraph, the following 

shall be displayed to disc for display on the SCAD system. “ the integrated hourly, daily, weekly, 

monthly and yearly total outlet flow to treatment.. please re-draft for more clarity, is it including the 


effluent from the treatment plant as well. The SCADA system will display to disc the treated 

effluent flow hourly, daily, weekly, monthly and yearly. Redrafting taken into account in the 

DD report. 

64. Page 55, clause 3.7.3.1 General overview control philosophy, General. Is the effluent pumping 

station is included in the PLCS of the tertiary treatment. Yes 

65. Page 58, clause C, fine screening” 3 paragraph, “ stop on low level into each inlet channel “Arret sur 

niveau bas dans chaque canal d’arrivee”. Pleas clarify in English if it is not duplicated in French. 


66. Page 61, clause H, grease pit, third paragraph, is their any rang of the seconds recommended by 

the consultant to automatically shut the valves for the execution phase. Modification taken into 


67. Page 63, clause C. blower room, last sentence, fresh air injection fan (optional). Can be considered 

in this stage not as an option. The same as set (optional) as mentioned under in paragraph no. 3. 


68. Page 63, clause C, blower room, third paragraph, Automatic Functioning, please verify the number 

of 3 blowers (1 per aeration tank) the fourth is standby. Please check the numbers with page 43, 

where it is 2 +1 standby if it meant the same. The number of blowers is 1 per aeration tank plus 1 in 

stand-by. This modification has been taken into account in the DD report, page 43. 

69. Page 67, Clause 3.7.3.9.3, tertiary treatment, intermediated pumping station, electro pumps sets 

(3+1S); check the pumps number and is for the final stage, check with the number set in clause 

3.6.2 in page 45, 46. The number of intermediate pumps is 2 (phase 1) + 1 (phase2) + 1 stand-by. 

Modification taken into account in the DD report. 

70. Page 68, clause c., sand and filtration –washing; 7th row, please verify or correct the word “ to 

rincing water”. The same as for “Automatic filter washing gestion” and “eletropump” in the fourth 

paragraph. Corrections taken into account in the DD report 

71. Page 70, Clause F, Treated effluent pumping station, electro pumps sets (3+1S); check the pumps 

number and is for the final stage, check with the number set in clause 2.4.4 in page 31. The 

number of treated effluent pumps is 2 (phase 1) + 1 (phase 2) ° 1 stand-by. Corrections taken 

into account in the DD report. 

72. Page 73, in the table, clause 3, grit and grease removal, check the number of the submerged 

turbine aerators for phase 1 and 2. The number of submerged turbine aerators is 3 per grit and 

grease removal tank, so 6 phase 1 and 9 phase 2. 

73. Page 74, in the table, clause 2, blower room; check the number of the air blowers for phase 1 and 2. 

The same for the sludge recirculation pumps and the submersible pumps in clause no. 3 of the 

degazing and distribution well. The number of air blowers for phase 1 and 2 is correct ( 2+1, 

phase 1 and 3+1, phase 2), the number of sludge recirculation pumps is (2 per aeration tank 

(so 4, phase 1 and 6, phase 2) + 1 stand-by in stock). The number of scum pit is 2, phase 1 

and 3, phase 2, in each scum pit the number of submersible pumps is 2 (1 + 1 stand-by). So 


in phase 1, the total number of submersible pumps is 2+2 stand-by (phase1), and 3+3 (phase 

2). 

74. Page 76, in the table, clause 5, treated effluent pumping station; check the number of the 

submersible pumps for phase 1 and 2. The same for the submersible pumps in clause no. 2 and 3. 

The numbers of submersible pumps are correct 

75. Page 76, in the table, PLC3 or PLC4, is the pumping unit of the industrial water is included. If not 

shall it be included in the system. The industrial water has been included in the PLC3, 

modification taken into account in the DD report. 

76. Page 78, shall the HVAC be included in the PLCs system or not recommended. Not recommended 

77. Page 79, clause 3.8.1, power supply; please specify the exact length of the electrical line to the KY 

WWTP, as about 2500 m is sound not accurate. The exact length is 2500 m. Modification taken 


78. Page 79, clause 3.8.1, or where appropriate, mentioning the main electrical grid required to connect 

the waste water treatment plant with the electrical source ( package 4 agreed upon on the meeting 

conducted on the PWA on 10 Feb. 2010). Modification taken into account in the DD report 

79. Page 82, clause 3.8.3., B. substation No., second paragraph; please distinguish between MDB1 and 

MBB2 clearly. And redraft the paragraph clearly to identify “the secondary distribution board or 

“boards” that were located inside or beside each building”. As it sound confusing paragraph 

between the MDB1&2 and the secondary boards. Modification taken into account in the DD 

report 

80. Page 82, clause 3.8.4, Electrical Generators; re-draft the relevant paragraph to clearly specify the 

rating power of the two generators. As the capacity of 1500 KVA is meant for the first one. The 

capacity of the fuel tank of 30 m3 shall be justified based on the fuel consumption rate of the two 

generators. Modification taken into account in the DD report 

81. Page 83, clause 3.9, civil works, second paragraph, floors of the facilities for the process units will 

be painted with epoxy paint. This shall include the interior walls in addition to floors as well. The 

type of epoxy shall be specified and shall be resistant and sustainable angst the waste water. 


82. Page 83, clause 3.9, civil works, second paragraph, the metallic structures (grating, handrails, 

covers and stairs, will be from aluminum or hot galvanized iron for heavy pieces. Please check 

against corrosion and may stainless steel to be used to prevent corrosion whereas appropriate. 

Modifications taken into account in the DD report according Mr Aude recommendation on 

20.01.2010. 

83. Page 83, clause 3.9, civil works, third paragraph, excavated area below foundation in KYWWTP 

shall re- backfilled by one layer 0.40 m thick of a coarse gravelly calcareous sand (kurkar)…. 

Please specify the re- backfilling layers, please re-draft to clearly specify that the re-backfilling shall 

be implemented into two compacted layers at least. Modification taken into account in the DD 

report 

84. Page 86, clause 3.9.1.3.3, concrete design, General requirements, second paragraph, walls have 

at least 10”[250mm] thick and footings have at least 12”[300mm] thick; pleas check and verify this 

condition in comparison to drawings, especially for walls. Ckecked 


85. Page 87, clause 3.9.1.3.4, design strengths, second paragraph, check and verify the strength of 

B300 and cement content with the strength of 25 Mpa as set in the table for the main applications. 


86. Page 90, clause 3.9.1.7.6, foundation protection, concerning the paving the adjoining ground away 

from the building edges and providing drainage ditches to take the water to lower ground (street). 

Please redraft to be more specific for KY WWTP case, and take it into consideration in the detailed 

design and the relevant quantities and the whole drainage system shall be designed and included 

in the drawings and the BOQs. A complete storm water drainage system for KY WWTP has 

been designed and included in the drawings and the BoQs . 

87. Page 90, clause 3.9.1.8, slab on grade design requirements, second paragraph, concerning the 

water penetrating the slab that can cured by proper drainage and use of vapour barriers. Please 

redraft to be more specific for KY WWTP case, and take it into consideration in the detailed design 

and the relevant quantities and the whole drainage system shall be designed and included in the 

drawings and the BOQs. Modification taken into account in the DD report 

88. Page 91, clause 3.9.1.9, structural materials specifications, stainless steel, type 304 architectural 

and common uses and anaerobic conditions. And type 316 submerged or corrosive areas. Please 

verify this specification with the materials usage as set in chapter 2 and 3 for the different treatment 

components and as per the above mentioned relevant comments. Stainless steel 316 shall be used 

whereas appropriate to prevent corrosion and for sustainability. Modification taken into account 

in the DD report 

89. Page 93, clause 3.9.3, offices building, in the table, steel protection shall be taken into consideration 

and designed for the aluminum windows for security measures as the site is located in a remote 

area. Required quantities shall be taken into consideration in the BOQs. Modification taken into 


90. Page 98, clause 3.9.4.1.2 Grit removal basins. Check the dimensions of length 16.85m, width 4 m 

and depth of 3.6 m with the figures mentioned in page 11, clause 2.2.2 for discrepancy. As 

indicated in Appendix 7.1, E3; the tank dimensions are as follows: Length: 16.25 m; Width: 4.00 m; 

Total height: 4.20 m. Comments taken into account in the DD report. 

91. Page 99, clause 3.9.4.5, sand filters, check the figures again with what set out in page 24 and page 

46. The number of nozzles in each filter is 50 unit/m², the long stem nozzles (220 mm) 

92. Page 100, clause 3.9.4.6, sludge drying beds, check the are of 600 m2 of each drying bed with the 

figure of 450m2 set in page 35, clause 2.5.3, drying beds. Modifications taken into account in 

the DD report. 

93. Page 100, clause 3.9.5, roads and fencing, last paragraph, more details and specific description 

shall be set concerning the fencing, the supporting columns or the steel angles used, ect.. 


94. Page 104, clause 3.10.2.1, valves installed on the effluent pressure line, concerning the drainage 

valves; check and specify the mechanism to evacuate the pipes, and is applicable to drain the 

water in the adjacent lands, i.e. will it be private land, what is the environmental effects, etc.. 


95. Page 105, clause c, cleaning access connections (blow off connections). Please check and specify 

the applicability of using blind flanges in case it is located in paved roads, or in the future when 

roads paved. The bolts will be hidden to avoid traffic. 


Chapter 4 

96. Revising the Investment costs based on the meeting conducted in the PWA on 10 Feb. 2010, and 

the comments raised on the detailed design report and the relevant rectifications/amendments to 

be done on the detailed design. Modification taken into account in the DD report 

97. Do the investment costs include the cost of the machinery needed to be purchased to operate the 

plant, such as trucks, loaders, etc… which mentioned in the report. Separate clause can be done 

for that needed costs. Modification taken into account in the DD report 

Chapter 5 

98. Revising the running costs based on the meeting conducted in the PWA on 10 Feb. 2010, and the 

comments raised on the detailed design report and the relevant rectifications/amendments to be 

done on the detailed design. Modification taken into account in the DD report 

99. Do the running costs include the running costs of the machinery needed to operate the plant, such 

as trucks, loaders, etc… which mentioned in the report; fuel and maintenance, fuel for stand-by 

generators, etc... Separate clause can be done for that needed costs. Modification taken into 


Chapter 6 

100. Page 123- 125, clause 6.1; Bidding Procedures; elaborated justification is needed concerning the 

selection of the FIDIC Red Book as per the relevant correspondence with UNDP. After relevant 

correspondence between the Mr Asraf Shamala and Mr Aude concerning the use of FIDIC 

Red Book as form of contract, Mr Asraf Shamala confirm the use of FIDIC in an email dated 

of 28 February 2010. 

101. Page 125-126, clause 6.2, Contract Packaging, elaborate the four contracts packages as agreed 

upon on the meeting conducted on the PWA on 10 Feb. 2010. Modification taken into account in 

the DD report 

102. Page 128, clause 6.3.1.1, concrete to cast, second paragraph, check and adjust the figure 30m 

3/j to m3/day. Modification taken into account in the DD report 

103. Page 128, clause 6.3.1.2. Earth work, check the amount of excavation and backfilling of the 

infiltration basins based on the last surface geotechnical investigations done on Al Fukhari 

infiltration site. Total excavation amount = 700,000 m3, modified in the final version of BoQ. 

Total Back filling amount = 400,000 m3 ,modified in the final version of BoQ 

104. Page 128, concerning the 8 months duration for supply equipment and pipes, clarify the 0.5 

months clearance for administration clearance in Ashkelon, if it is mean a harbor it could be 

Ashdod or Haifa harbor not Ashkelon. Modification taken into account in the DD report 


105. Page 127-130, clause 6.3, Planning, elaborate the planning of the four contract packages as 

agreed upon on the meeting conducted on the PWA on 10 Feb. 2010, The implementation 

schedule need to be amended and fit for these four packages. 

Appendix 4 

Civil Structure Calculations 

106. Please insert page numbers for the appendices. Comment taken into account in the DD 

report 

107. According to the codes there is an allowable margin for accepting the concrete strength after 

testing and variance in the strength is allowable to a certain extent. Accordingly, B250 is 

considered too low to be accepted for such important facility; pleas check. The design took this 

factor into consideration and this value (B250) is suitable value in Gaza. 

108. In clause 1.1.1 & 1.1.2, ribbed slab design and Beams design, etc… Shear factor is 0.75 

sometimes and 0.85 in other places. Kindly justify. Modification taken into account in the DD 

report, 0.75 is considered 

109. In order to replace the sulfate resistant cement crack width calculation was identified to be 

needed by the consultant. Kindly include it in the report. The check has been done, for example 

see page 15 in annex 4 (Z value) 

110. The dimensions of the walls are huge and need construction joints because of the quantities 

needed in castings process. In addition it is not recommended to add the dead loads on fresh 

concrete the minute it is cast as the loads are huge and may cause segregation and cracks. Please 

check. This problem may occur in the aeration tank 

111. Did the design take into consideration horizontal loads due to earthquake or may be nearby air 

raids bombing that Gaza is susceptible to. Actually for such huge vessels any breakdown in the 

structure may cause disaster. It is a point for discussion. Most of the project buildings are of low 

height or located under ground level , do not have soft stories and include relatively rigid 

concrete block exterior and interior walls. In addition the beam column and frame structural 

systems will provide adequate resistance to moderate earthquakes. Regarding the air raids 

bombing, it is very difficult to calculate it because of it has a lot of variables (distance, 

explosion intensity, etc…). Note: it is expected that factor of safety can cover this point 

112. The design report is very impressive. However, in areas like raft under circular columns there is 

no check displayed for punching shear, clause 2.8 and other relevant clauses. Please check. 

Comment taken into account in the DD report 

113. Was the wall of gravity thickener designed for applied moment that is induced by the cantilever 

steps. Please check. Checked, the stairs have a very low effect on the gravity thickener walls 

due to the fact that bending moment produced from it is very low (0.44 t.m) 

114. Kindly review the effective depth of the beam in the workshop frame. Reviewed 


115. The columns supported on the walls: the effective width of the wall is needed to be investigated 

to sustain the concentrated loads in terms of the provided steel reinforcement. In addition there is a 

need to verify the bearing capacity at the contact area since it is only hinge. Checked 

Drawings 

116. The comments on drawings set will be succeeded in a separate sheet; sheet 2. 


0.1.2. SHEET 2 – DRAWINGS 

Civil Works 

Plan Name Plan No. Comments 

A - General Comments 

1 There is no base map drawing available or contour line and site plan level was not 

shown. 

Comment taken into account on the set of drawings. contour map has been 

provided 

2 A general site layout drawing should be added to show the Treatment plant at its 

location and the surrounding facilities 

UG contacts the responsible municipality (Khan Younis Municipality) and asked 

for general site lay out, and they promised to provide us the drawing through the 

land authority. But till now we are still waiting… 

3 The drawings have to be arranged in accordance with the numbers shown on the layout 

drawing. 

It is difficult to arrange the drawing as in the general layout since some treatment 

unit has many numbers (for example, in the sand filter there is a number for the 

sand filter and for the UV and for the outlet pump station…etc which are included 

under one title). The arrangement was in accordance with treatment process 

sequences. 

4 The expansion joints details has to be clearly shown. 

Comment taken into account on the set of drawings 

5 The types of crops and irrigation system have to be included clearly in the treatment 

plant. 

Comment taken into account on the set of drawings, refer to dwg. DD - PIP - 

002_C 

6 The boundary walls and main entrance details are not shown. 

The guard room does not exist in any drawing. 

It is not permissible to construct boundary walls due to security (beside the 

boarders), the consultant use the fence which is shown in drawing DD - DET - C - 

001_A. 

The guard room exist in the administration building as shown in DD - BUI - A - 


001_A drawing. 

7 Check and correct some plans name to be fit with the contents of plans. 

There are two Drawing with the same Dwg. No. DD-GD-006-B (Hydraulic profile). Give 

different Number. 


8 Missing general buildings setting out layout with clear dimensions and distances with 

respect to specific bench mark 

It is not the consultant responsibility setting out the building, it is DETAILED 

DESIGN DRAWINGS not SHOP DRAWINGS. 

9 Missing design of generator foundations 

Comment taken into account on the set of drawings, refer to dwg. DD - DET - 005 

_ A 

10 Missing design of fuel tank and it's foundation 

Comment taken into account on the set of drawings, refer to dwg. DD - DET - 005 

_ A 

11 Missing typical detail of steel grating and steel handrails 

Comment taken into account on the set of drawings, refer to drawing DD - DET - 

A - 004 _ B 

12 Missing design of land scalping elements i.e walk ways , edge beam, curbstone …etc. 

throughout the site of plan 

Comment taken into account on the set of drawings, shoulders without curbstone 

or edge beams. 

13 Missing design of access road to the plant 

Out of the consultant scope of work. 

14 Missing sheet # DD-PRE-A-005_B 

There are only four drawings. It was amended 

15 To think about raising the strength of concrete in order to suit the aggressive 

environment and specify the strength for walls and other elements in the side notes 


16 Quantities measurement report should be provided 

Out of the consultant scope of work. 

17 Missing sheet # DD-THI-A-002_B 


18 Sheet # DD-Layout-E-004_B is repeated with different contents 


19 Expansion joint details and justify usage of 10 cm wide expansion joint. 



B - Comments on the 

Drawings 

20 Pretreatment Building DD-PRE-C-003 _ c The reinforcement in the rib is one bar on the plan but in section a-a is 2 


21 Pretreatment Building DD-PRE-C-005 _ c Detail for intersection of reinforcement in walls should reflect the correct position of the 

steel reinforcement with special details outlining the proper arrangement of steel bars 


22 Pretreatment Building DD-PRE-C-006 _ c Specify for what element the frame section FF is. It's not clear in drawing DD-C002. 

Detail D in the footing drawings is not displayed in the relevant detail drawing. 


23 Pretreatment Building DD-PRE-A-001_B Revise the hand railing layout at drawing 

Revised 

24 Pretreatment Building DD-PRE-A-001_B There is no access for the Storage area at level 58.00 

There is a door at the left of the stair, refer to drawings DD-PRE- A-001 _ B and 

section cc in drawing DD-PRE- A-003 _ B 

25 Pretreatment Building DD-Pre-C-001-B Revise F1,F2 &F3 bottom foundation (should be notified by B –bottom- not T top) 


26 Pretreatment Building DD-PRE-M-001_B The storage area is named as Electrical equipments room, revise and correct. 


27 Pretreatment Building Electrical Equipment room is located under the screening channel, it is expected to 

be perfect, but through supervising all the pump stations at Gaza strip all the 

electrical equipment below the screening were flooded, it is preferable if all the 

electrical equipment are above the ground, better if it is at first floor level. 

Comment taken into account on the set of drawings, the internal door has been 

closed and the first bottom 0.5 m is changed to reinforced concrete to prevent 

water from seepage. Refer to dwgs. DD-PRE- A-001 _ B & Section bb in DD-PRE- 

A-003 _ B 

More details are required for screening skid and the railing shown at some plans. 


It is not clear how the screens will be lifted from the top of the building, (crane or 

What?) 

The screens will be lifted by External winch. 


28 Aeration Tank DD-AER-C-002_B Missing details of steel reinforcement at the intersections 

Specify the embedded steel length of the circular wall into the 90 cm wall at the 

intersection. 

Comment taken into account on the set of drawings, refer to drawing No, DD – 

AER – C – 002 _B 

The anchorage Length of steel into the 90cm wall refer to drawing No, DD – AER – 

C – 004 _ B 

29 Aeration Tank DD-AER-C-003_B revision of the number of reinforcement bars in section 2-2 

Revised 

30 Aeration Tank DD-AER-C-004_B More detail is needed for the weir in detail 1 


The name of sections to be revised 

Revised 

Check the level at Section C-C 

Checked 

Check the reinforcement detail around the opening in Section C-C 

Checked 

Correct the dimensions scale 

Corrected 

Correct the no. of rebars per meter length in the detail of W11 and W3 

Why not to apply the steel distribution for the other walls 

About the no. of rebar’s per meter length in the detail of W11 and W3 the load 

distribution with triangular load max load at the bottom and approach to zero 

at the top , the wall include direct tensile stress refer to DD – AER – C – 004 _ 

B. 

31 Aeration Tank DD-AER-C-005_B There is discrepancy in the reinforcement steel in section A-A and Detail 1. It’s repeated 

in Dwgs. 


Review the hidden and intersected walls in Section A-A 


The main steel is usually the vertical ones, so the main steel shall be external. Review 

the position of steel in many of the Dwgs. 

The longitudinal wall designed in the same time to resist the axial tension and 

resist the vertical loads like bending moment, we checked the tensile stress 

applied on concrete due to heavy stress so we embed the vertical reinforcement 


in concrete to avoid corrosion at the large scale time, because this building is 

very sensitive and herbier load level and case of loading. 

32 Aeration Tank DD-AER-C-010_B Review the water stop & expansion joint in the walls and foundation 

The work will dictate intermediate construction joint in the walls. Details in this regard to 

be considered. 

Comment taken into account on the set of drawings, refer to Detail 1 drawing 

No DD – AER – C – 002 _B and detail 4 drawing No DD – AER – C – 010 _ B. 

Check the number of steel bars in Detail 3. 

Comment taken into account on the set of drawings, the number of steel bars 

in Detail 3, refer to DD – AER – C – 010 _ B. 

33 Aeration Tank DD-AER-C-014_B Specify the thickness of the landing above the column 


34 Aeration Tank DD-AER-C-018_B Show the dimensions and steel detail for the trenches 

Comment taken into account on the set of drawings, new details for the 

trenches refer to DD – AER – C – 018 _ B, Detail No 2. 

35 Aeration Tank DD-AER-C-020_B Show the reinforcement for middle foundation in frame 

Shown 

36 Aeration Tank DD-AER-C-004-B Revise section name AA to be BB. 

Revised 

37 Aeration Tank DD-AER-M-001_B It show 62 air nozzles while at the section in DWG DD-AER-M-003_B show 31 nozzles, 

please check 


38 Aeration Tank Provide details for the expansion joint at walls. Comment taken into account 

on the set of drawings 

 

While you are using tie beams at the top of the walls at the tank, it looks like the 

external walls are designed as a cantilever walls with a thickness of 900 mm, if 

another alternative of design with consideration for these tie beams and walls as 

a simply supported slab, the thickness of the external walls will be reduced 40%. 

The design philosophy for this wall depends on. 

DD- Wall fixed at the Bottom and pin support at the top so we have a tie 

beam every 4.8m center to center. 

We applied a horizontal beam with adequate stiffness, the service 

bending moment reaches to 41 m.t. 


efer to aeration tank design section 2.1.1 and 2.1.2 

DD- But if we don’t have a tie beam at the top the structural system 

change to fixed at the bottom and free at the top, the service bending 

moment reaches to 85 m.t that need 140cm wall thickness 

 

Ribbed slabs for the platforms are not preferable as the block will be in direct 

contact with the apour of the wastewater. 

The bottom of the slab should be plastered and painted by epoxy 

 

 

There is no stair or ladder to enter inside the tank for maintenance works. 


The tank should have a low level pipe or sump pit to empty it at the case of 

maintenance, the lowest pipe level is 51.04 which is 2.41 meter above the floor 

will remain full of water. 

The internal recycle pumps are lowered and will be used for emptying the tank in 

case of maintenance. 

 

There is no details for the nozzles also no details to show the support of the 

nozzles at the ground. Comment taken into account on the set of drawings 

39 Clarification Tanks DD-CLA-A-001_B Review the required diameter for effluent line 

The diameter of the effluent line is correct Show the detail of the components of the 

handrail 

Comment taken into account on the set of drawings, refer to dwg. DD – DET – A – 

004 _ B 

40 Clarification Tanks DD-CLA-A-002_B There are many discrepancies in dimensions and scales 


Check the radii in Plan FF with that in plan DD-CLA-A-001_B 


Add detail for SS plate fixation with the concrete in Section FF 

Added 

Provide enough cover for the underground pipe in Section E-E 

Provided 

Show more detailed dimensions to section E-E and D-D 


Show more detailed dimensions for the weir and cylindrical barrier 



Show the benching at the bottom of the well in section F-F 


41 Clarification Tanks DD-CLA-C-002_B Review the dimensions to be fit with other sections and other plans 

Revised 

Clarify the steel reinforcement in section C-C 


Show the pipe openings in section C-C 


42 Clarification Tanks DD-CLA-C-003_B Check radii with previous drawings 

Checked 

43 Clarification Tanks DD-CLA-C-004_B Show the pipe openings penetrating the pit walls 


Specify the depth of beam under the stair landing 


Check the reinforcement at the bottom corners in section CC and DD 

Checked 

44 Clarification Tanks DD-CLA-C-005_B Show the pipe inlet in section EE 


Check the dimensions of scum tank with CLA-A-001B 

Checked 

Show the stair width between degazing and scum tanks 

Shown 

45 Clarification Tanks DD-CLA-M-022-B The top level of the front Metallic weir at section EE DWG DD-CLA-M-022-B is not 

shown, it looks like it is 54.69 which may allow scum to move to the clarified effluent, 

please check. 


46 Clarification Tanks DD-CLA-A-002-B Revise section F-F at Drawing DD-CLA-A-002-B, the thickness of the wall show 2.22 

while it should be 0.55, please revise. 

Revised 

47 Clarification Tanks DD-CLA-A-003-B Clarifier Effluent collection well at DWG DD-CLA-A-003-B the raft level show 52.12 and 

at DWG DD-GD-006-B the WL is 51.68, please check. 

Checked 

48 Clarification Tanks DD-CLA -C-006-B Revise section AA to be Section BB. 

Revised 


49 Clarification Tanks It is not clear how the sludge is collected in the middle of the clarifier, if the sludge 

floating by bubbles, how to direct it to the center pier. And the sludge close to the 

external wall will float close to the clarified water exit. 

The sludge will be collected using vertical vacuum pipes and the flow will be 

directed to the central will of the clarifier. From there the sludge will be 

transferred by a vertical pipe in the center of the pier. The sludge closed to the 

external walls will be collected by the vertical vacuum pipes and will not escape 

with the effluent water. 

Also the concrete top level of DW3 show 54.00 while the water level at the clarifier 

54.69, at the case of water balance at the manhole and the clarifier the water will 

start flooding out of the well, check to raise the concrete level to 54.90 

There is no flow at static condition, in this case there will be no water in the outlet 

manhole of the clarifier. 

50 Sand Filter DD-TER-C-001_B The walls separating the two phases should not be permanently closed. Identify the 

mechanism to connect the two phases in the future. 

In general the sections presented didn't illustrate well the structural details in the filter 

rooms. Some of the sections can be deleted and new ones added 


51 Sand Filter DD-TER-C-002_B Show the inlet opening 


Specify the stirrups reinforcement in detail 1 


52 Sand Filter DD-TER-C-003_B Show the columns and walls location on the background 


Show the reinforcement around the openings 

Comment taken into account on the set of drawings, refer to section K-K Drawing 

No, DD-TER-C-011 _ B 

53 Sand Filter DD-TER-C-004_B Specify the stirrups reinforcement in detail 1 


Show the reinforcement details at the intersections 


54 Sand Filter DD-TER-C-005_B All sections should be presented architecturally with full dimensions in separate sections 


Specify the diameter of spiral reinforcement in circular columns 


55 Sand Filter DD-TER-C-006_B Review the dimensions 

Reviewed, 


56 Sand Filter DD-TER-C-008_B There are duplicated details. They consume space. 

There are no duplication details, but these details used to show the reinforcement 

57 Sand Filter DD-TER-C-009_B All sections should be presented architecturally with full dimensions in separate sections 


58 Sand Filter DD-TER-C-010_B Only small difference between the two frames. Avoid duplication of details 

The previous two frame just to discuss the reinforcement detailing through 

the frame and sand filter walls 

Specify the stirrups reinforcement in section 1-1 


59 Sand Filter DD-TER-C-011_B Check the stirrup spacing at max. shear (adjacent to the columns) 

Check the bottom reinforcement of B5 with that in section 1-1 

Checked, 

60 Sand Filter DD-TER-C-012_B Check stirrup at max shear 

Details in this sheet could be integrated with the previous sheet 

Checked, 

61 Sand Filter In general there are no close details for the materials under the sand, and how to 

protect sand from going down. 

The main function of the gravel support layer is the support the filter sand. The 

filter gravel layer is graded from coarse gravel at the bottom to fine gravel at 

the top. The layer is laid below the filter sand to support it and to prevent 

flowing out of the sand during filtration. 

Why it is chosen to pump the dirty water up to the sand filter, as we are building 

the structure under the ground we can go down another 3 meters and let the 

water flow by gravity from the clarifiers to the sand filter without pumping. 

It will be difficult to maintain the sand filters if it below the ground level. 

Moreover the intermediate pumps power consumption is relatively low. In 

addition the pumping head of the effluent pump station and the dirty water 

pump station will increased by 3 meter which will add more power to the recent 

design . 

 

The location of sections EE, FF, GG non of them show the sand filter and the 

layers of sand, Why? 

Comment taken into account on the set of drawings, all of these sections show 

the details of pumps area, other sections (AA, BB, CC, DD) show the sand filter 

details. Sand layers are shown in DD-TER-M-003_ B. 

Section EE should show pipes at the left hand side, where is the pipe please 


show. Comment taken into account on the set of drawings 

In plan A-A and section DD at DWG DD-TER-M-001-B the longitudinal channel 

beside the sand filter will be filled with dirty water without passing to the sand 

filter. 


62 Air Blowers DD-TER-C-014_B Where's Reinforcement of the columns 


Check the Reinforcement in the cantilever 

Comment taken into account on the set of drawings, minimum reinforcement 

Add detail of the joint between the back wash room and sand filter building 

Show the filler (polystyrene board 2.5 cm thick) in the expansion joint sec D-D 


63 Air Blowers DD-TER-C-015_B Check the details of B1 

In B1 check the stirrup spacing at max shear (adjacent to the column) 

Correct the name of sections and B4 dimension By engineering sense the 

reinforcement of the two spans of B4 is not the same. Check the design. 


64 Sand Filter DD-TER-M-002_B Think about connecting phase II to the operating system in the future. Clarify details of 

that connections required for future expansion without disturbing the sand filters 

operations 


65 Gravity Thickeners DD-THI-A-003_B More detail for S.S basin is needed 


Correct the scale in section AA and FF 


66 Gravity Thickeners DD-THI-C-002_B Steel compensation around the opening is required? 


In section AA there is unclear steel 


67 Gravity Thickeners DD-THI-C-003_B There is no difference between GB2 and GB3? No need for duplication 


Clarify the expansion joint Detail 


68 Gravity Thickeners DD-THI-M-001_B Add Details for supernatant return basin 


69 Gravity Thickeners DD-THI-M-003_B Correct the Scale 



70 Sludge Drying Beds DD-DEW-C-002_B Correct the dimension of concrete splash Slap 

Comment taken into account on the set of drawings, it is correct 

This detail is not compatible with location of section B-B 

Variable because the bottom of the channel is sloped but how much? 

The comment not clear 

71 Sludge Drying Beds DD-DEW-C-003_B Is the joint is totally filled with mastic or using other material? 

Done, no, it has modified 

Where is the joint on the plan and every how much should be repeated? 

Explained 

Determine what holding the pipe in section CC. 

Concrete support already exist. 

Show the excavation level of wall foundation 

Shown 

The depth of the channel is variable because the bottom of the channel is sloped, but 

how much is the slope? 


Check the dimensions on section DD. 


72 Sludge Drying Beds DD-DEW-C-004_B No need for detail B beside the drainage pipe since the detail above is sufficient and 

slightly different. Duplication of drawing? 

It is clarify the openings 

73 Sludge Drying Beds DD-DEW-M-001_B This sheet does not differ from DD-DEW-C-001_B. Avoid duplication. 

Comment taken into account on the set of drawings, duplicated drawings has 

been omitted, and the rest moved to the civil drawings. 

74 Sludge Drying Beds DD-DEW-M-002_B This sheet does not differ from sheet DD-DEW-C-002_B except section B_B which is 

shown in D-D DEW-C-003_B. Duplication? 

Comment taken into account on the set of drawings, duplicated drawings has 

been omitted, and the rest moved to the civil drawings. 

75 Sludge Drying Beds DD-DEW-M-003_B Show more detail about pipe support. 


76 Sludge Drying Beds DD-DEW-M-004_B How by what mean sludge is to be collected from down stream and goes to pump well? 

In the drying beds, the solids in the sludge remains on the surface of the bed and 

the water percolate vertically and enters the perforated pipes. The perforated 

pipes transfer the water to the open channel in the middle of the sludge drying 

beds. At the end of the open channel a manhole is constructed from which a 

gravity pipe transfers the water to the back flow pump station. 

Show the perforation spacing and diameter in detail 1. 

Comment taken into account on the set of drawings, refer to dwg. DD - DEW - C - 


005 _ B. 

77 Sludge Drying Beds DD-DEW-M-005_B It’s enough to present levels at different sections in a small table or determination of 

slope. No need for this sheet. 

Using this drawing it is easier in construction rather than using a table, moreover, 

it is shows the levels in more accuracy and clarity 

78 Sludge Drying Beds Detail B DWG DD-DEW-C-004-B the perforated pipes appears not to be 

continuous while at the plan at DWG M004 all the pipes are connected through T, 

please revise. 

All of pipes are continuous, but the place of the section is beside the drainage 

pipe, so it shows the pipes in the transverse direction and the compacted clay 

 

The perforated pipes if covered with Geo textile fabric will be better. 

The geo-textile will not be necessary in this case and will be very expensive 

 

Extend the concrete splash slap another 50cm. 

No need for adding 50 cm to the splash box 

 

Through the cleaning of the dried sludge by machines part of the graded soil will 

be loosed and the loader will destroy the layers, it would be better if the slab is 

constructed by strips of reinforced concrete and empty places filled with the same 

layers in the drawings and keep the width of the empty spaces less than the width 

of the loader wheels. 

The loader will not destroy the layers 

79 Compositing Area DD-COM-A-001_A Missing detail for ramp and channel details? 


80 Compositing Area DD-COM-A-002_B Check the slopes 


81 Compositing Area DD-COM-A-003_B Check the slopes 


82 Compositing Area DD-COM-C-001_B Check the slopes 


Ramp should sustain heavy load trucks and loaders. Clear the design. 


83 Compositing Area DD-COM-C-002_B Concrete ground slab reinforcement details are not clear. Need to be illustrated? 


More details needed in detail A 



Unify the unit of dimensions otherwise to determine whether in m, cm or mm?? 


84 Compositing Area DD-COM-C-003_B In detail D, is it filled totally with kalkal or mastic sealant is to be used at the faces? 


85 WWTP Administration Building DD-BUI-A-001_A Show the North direction as long as the elevations are in terms of geographic directions. 


86 WWTP Administration Building DD-BUI-A-004_A Complete the layers of roofing in the finishing table 

Is Tyrolean suitable for entrance finishing? 


87 WWTP Administration Building DD-BUI-M-003_A Compare the AC capacity with spaces especially in the 1st floor. 

The server room requires 2(A/C) to work alternatively 

88 WWTP Administration Building DD-BUI-C-002_A Study the supporting system in such square staircase and study also the openings so 

that they don't interrupt the supporting beams. 

The supporting system does not interrupted with the openings . 

89 WWTP Administration Building DD-BUI-C-003_A Correct the name of the drawing 

Correct the name of sec 1-1 (Contraction joint detail) 

Revise the dimensions in Ground beams plan 

Comments taken into account on the set of drawings 

90 WWTP Administration Building DD-BUI-C-004_A Correct the discrepancy in the reinforcement steel between plan and sections 

It is better to unify the size of haurdy blocks throughout the project as long as the slab 

thickness is the same. 

Corrected 

91 WWTP Administration Building DD-BUI-C-005_A Check dimensions in detail of GB1 and compare with building layout in sheet DD-BUI-C- 

003_A 

Correct the discrepancy in the reinforcement steel between frames and sections 

Comments taken into account on the set of drawings 

92 Details DD-DET-C-001_A Add more detail for drainage channel 

Comment taken into account on the set of drawings, Refer to dwg. DD - DET - 003 

_ C 

93 Details DD-DET-C-002_A Missing dimensions and structure design of transformer base. 

Dimensions, design? 

Comment taken into account on the set of drawings, the transformers will be 

directly on the ground slab 

Where is the design of the distribution manhole? 


Correct the discrepancy in the reinforcement steel in B1 and ground slab. 



94 General Layout DD-Layout-E-004_B Specify for which building this foundation belongs and correct its dimensions? 


95 Infiltration Basins DD-INF-A-004_A Sections should show excavation levels as indicated in previous sheet. 


96 Infiltration Basins DD-INF-A-012_A Determine stripping thickness? 


97 Infiltration Basins DD-INF-A-013_A Add detail for the apron? 


98 Infiltration Basins DD-INF-A-015_A Show the structural Design of the platform around vertical pipe 


99 Infiltration Basins DD-INF-A-017_A Where is the boundary of the fence on the plan? 

The boundary of the fence on the plan is presented with the drawing scale 

100 Infiltration Basins DD-INF-A-018_A Specify the Finishing of the building? 


Check the dia ф 920 mm in the lower plan E.P? 


101 Infiltration Basins DD-INF-A-020_A Add the Finishing Table? 


Specify the external finishing? 


102 Infiltration Basins _ Intel 

Rooms 

103 Infiltration Basins _ 

Administration Building 

DD-INF-C-001_A 


What's about column reinforcement? 


Specify the dimensions and the reinforcement of the inverted beam in section SE 1-1? 


Add detail of circular column and its footing 


Correct the discrepancies in scales 


Add supporting footings under the intersections of ground beam 


104 Infiltration Basins Add details for the irrigation networks for agricultural purposes of plantations and details 

of the plantations 


105 Pressure Line Survey DD-P-001_A Where are R1, R2, and R3 on the plan? 


106 Emergency & Effluent pipe Line DD-P-005_A Check the size of diffuser and compare with the pipe going to the infiltration 

The size of the diffuser is right since the pipe which going to the infiltration 

basins still with diameter of 920 mm but the pipe going to the Energy Breaker 1 


increased to be 1030 mm in diameter. 

107 Emergency & Effluent Pressure 

Line 


Line 


Line 


Line 


Line 

Electrical Works 

DD-P-023_A 

DD-P-025_A 

DD-P-026_A 

DD-P-027_A 

Correct the discrepancies in scales? 


Check the items in the table of contents? 


Reconsider the size of rocks and indicate the total depth of respective rocks layers 


Specify the diameter of vertical pipe in Blow-Off Connection 


Indicate the degree of angle in Thrust Block Type (B) 


Add details for check and washing manholes 


1 The availability of sufficient power source at the area: This item is considered as 

high risk factor, the estimated power demand for operating the plant is approximately 

2800 KW, it is worth motioning to highlight and discuss this issue with all respective 

parties at the beginning of the project to assess any financial implications that may arise 

during the implementation of the project. 

Done, UG discussed this issue with GDECO and they told that they can 

provide 3 transformers 1250 KVA + Transformer 630 KVA= 4380 KVA = 3500 

KW 

2 Connection works with GDECO grids: this point is directly linked to the previous item; 

the BOQ does not include the cost of electrical connection works with GDECO medium 

voltage lines. 

Comment taken into account on the set of drawings, BOQ was included 

3 Capacity of stand-by generators: There are discrepancies between the layouts 

regarding the capacity of the stand-by generators, this issue should be raised and 

discussed with consultant in order to avoid any financial implications in the future. 

Comment taken into account on the set of drawings, refer to the dwg. DD-layout – 

E006_C and annex 5 (electrical calculation sheet) 


4 Capacity of stand-by generators: The emergency power source (Generators 

capacities) doesn’t consider the future growth of the plant, at minimum 20% should be 

considered on top of the essential demand power. 


E006_C and annex 5 (electrical calculation sheet) 

5 Distribution boards (External Pillars) layouts and BOQ’s are missing. 


E008_B 

6 Emergency UPS power source layouts and BOQ’s are not available. 

Comments taken into account in the DD report 

7 Emergency UPS power source layouts and BOQ’s for the plant facilities are not 

available. 


8 Ensure that all loads stipulated under the design report took the proper demand 

factor (detailed calculations are needed for the consultant). 


9 Calculation sheets for the quantities are needed to verify the submitted BOQ’s. 

Comment taken into account on the set of drawings, calculations based on the 

drawings 


0.1.3. SHEET 3- COMMENTS OF PWA AND CWMU 

1. Civil Works: 

1. There is no base map drawing available or contour line and site plan level was not shown. 

Refer to comment No.1 in sheet 2 

2. The guard room does not exist in any drawing. 


3. The expansion joints details has to be clearly shown. 


4. The types of crops and irrigation system have to be included clearly in the treatment plant. 


5. The boundary walls and main entrance details are not shown. 


6. The drawings have to be arranged in accordance with the numbers shown on the layout drawing. 


2. Mechanical Works: 

2.1) General:- 

7. T he Odor treatment system for pretreatment building has to be considered. The odour treatment 

system has been included in the DD report 

8. The Energy recovery system for biogas utilization has to be proposed at least for phase 2. The 

selected and approved sludge treatment won’t produce biogas. So the energy recovery 

system can not be proposed. 

9. Materials specification for equipment is stainless steel grade 304L, it is preferable to use grade 316 

in WWTP conditions. Equipments in stainless steel grade 304L are usually installed in 

wastewater treatment plant. The stainless steel 316 is very expensive compared to 304L. We 

take into account your comment (304L to 316) and modify the BoQ accordingly. 

10. The Surge tank material is preferable to be stainless steel. Surge tank in stainless steel grade 

304L are usually installed in wastewater treatment plant. The stainless steel 316 is very 



11. The Spare parts and special tools list for electromechanical equipment has to be added. Comments 

taken into account in the DD report 

12. The Laboratory equipment has to be added. Comments taken into account in the DD report 

13. The Work shop tools and equipment are necessary to be included for O&M. Comments taken into 



14. The Machinery (loader, tipper truck, plough tractor) are necessary to be included for infiltration basins 

periodic maintenance. No need for these machinery in the infiltration site since it is costly and rarely 

used. The machinery in the WWTP may be used for the maintenance works in. The infiltration site ( 

the two site are close from each other) or it can be rented. 

15. Hand rails materials for aeration tanks is galvanized steel in the BoQ , but in drawing DD-AER-A- 

008-B states it is stainless steel , it is preferable to be stainless steel 316. Equipments in stainless 

steel grade 304L are usually installed in wastewater treatment plant. The stainless steel 316 is 

very expensive compared to 304L. We take into account your comment (304L to 316) and 

modify the BoQ accordingly. 

16. The hand rails in other buildings BoQ are galvanized steel, but there is no detail drawings and it is 

preferable to be stainless steel. Comments taken into account in the DD report 

17. Item no. 11101 of the BoQ, 2 stop logs to be changed to 4 stop logs as per related drawing. 


18. Item no. 11301 of the BoQ, penstocks to be with electric actuator. Comments taken into account in 


19. The Stainless steel Pipes grade 304L; it is preferable to be changed to 316L in WWTP environment. 

Equipments in stainless steel grade 304L are usually installed in wastewater treatment plant. 

The stainless steel 316 is very expensive compared to 304L. We take into account your 

comment (304L to 316) and modify the BoQ accordingly. 

20. The hoists in all buildings are not clear if it is manually or electrically operated and there is no detail 

drawings and dimensions for the hoist steel structure. All hoist in KYWWTP are electrical hoists, 

we have add that on the relevant drawings, please reflect this in the BoQ items since you 

prepared it. 

2.2) HVAC: 

21. The Ventilation fans have to be considered for pretreatment building, blowers, generators, 

administration and workshop. Done, ventilation vans added to administration, other buildings 

are naturally ventilated. 

22. The Air conditioning units are not included in the admin. Building BoQ. Comments taken into 


23. The Water fire fighting system have to be added for the plant includes (pumps set, piping net work, 

hose reel cabinets, fire hydrant), and fir extinguishers to be shown on the drawings. Comments 

taken into account in the DD report, refer to dwg. DD - PIP - 002_A and BoQ, Bill 15.4 Fire 

Fighting System 

24. Ditto, but for water supply. Done, after contacting A Fukhari municipality, the nearest 

connection point for municipal water supply is located at 1850 m far from the location of KY 

WWTP. Refer to dwg DD - PIP- 003 _ A , and BoQ Bill 15.3 Municipal Water Supply. 

25. The Main water tank of at least 30000L is necessary to be added (for fire + water supply). Done, for 

fire fighting, the clean water tank in the sand filter (more than 120000 liter). Meanwhile, roof 

storage tank will be used for domestic usages where required to provide 2 days storage 

capacity. 

26. The Main drainage manholes and connections for administration building have to be added. 

Comments taken into account in the DD report, refer to dwg. DD-BUI-M-01-A. 


27. The Detail drawings for fuel tank and connections with generators have to be added. 

Comments taken into account in the DD report, refer to comment No.10 in sheet 2 

2.3) Infiltration Basins: 

28. A flow meter is needed to be installed in case both out let to IB and to the sea outlet are used at the 

same time, 

At the outlet of effluent pump station in the treatment plant, a flow meter is included in the 

design. This flow meter will measure the flow going to the infiltration basins or to the sea outfall. 

On the other hand, there is no pumping mode in which the water will be pumped to both 

infiltration basins & sea outfall. 

29. Irrigation net work for plantation and pumping units from effluent has to be added. Comments taken 


30. There is no detail drawing for effluent distribution vertical risers inside the basins. Comments taken 


31. The I beam dimension for the hoist in side service rooms to be shown on sheet DD-INF-M-001- 

A.Comments taken into account in the DD report 

32. The metal doors location of the service room is preferable to be installed at the road sides which is 

easer for O&M.Comments taken into account in the DD report 2.4) Pressure Pipe Line: 

33. The design criteria for selecting and sizing the air release valve have to be included. Comments 


34. Two gate valves complete with manholes and necessary fittings have to be installed at the branch of 

the IB pipe and at the sea outlet branch. Comments taken into account in the DD report 

35. On drawing DD-P-023-A (table content for drain valve manhole), the diameter of 820mm to be 

changed to 920mm. and the Gate Valve component has to be checked/deleted. Comments taken 


36. Ditto, but for table content of air valve table of contents. Comments taken into account in the DD 

report 

37. Concerning the pipe size 1030 mm, there is no detail drawings for valve and fittings in side drain and 

air valve manholes. Comments taken into account in the DD report 

38. On drawing DD-P-026-A, the outlet manhole gravity pipe has to be steel instead of concrete. 


3. Electrical Works: 

39. The automation drawings are not included in the submitted set of drawing; the one sheet of 

automation.GD-009 is not enough for review or evaluation. Documents added in the set of 

drawings 

40. More details for the electrical rooms, trenches, cable trays and ladders, has to be included. 


41. The electrical loads calculation and lighting illumination level charts has to be attached. Comments 



42. The External lighting plan to be verified in regards to the distances, number of fittings and cable 

sizes. Comments taken into account in the DD report, refer to drawing 

(№DD_Layout_E_002_B) 

43. The number of cables feeding the generator #1 to be reviewed, the cable to be 3(4x300) 

+2x300mm2.Comments taken into account in the DD report refer to drawing (№ 

DD_Layout_E_003_C) 

44. The main C.B locations in the main panels to be justified/ reviewed. The main circuit breaker in the 

main is (4(3X300) + (2X300) mm2) refer to drawing (№ DD_Layout_E_006_C) 

45. Use digital multi meter unit for measuring the power, P.f, Volt, Ampere, Rather than the conventional 

one type. Comments taken into account in the DD report 

46. Where are the voltage surge protection and UV phase sequence and phase failure relays in the main 

panels? Comments taken into account in the DD report 

47. The Main Distr. Boards shall be equipped with ventilation system. We used Air condition unit 

30000 BTU at the room of MDB. See plan (№ DD_ARE_E005_C)&(№ DD_TER_E002_C). 

48. The rating of the SIRCOVER VE/3150A compared to the incoming C.B 2000A is not logic, need to be 

revised. Please refer to drawing (№ DD_Layout_E005_C) modified according to the incoming 

circuit breakers. 

49. Using cable 4x70mm2 for main circuit breaker 100/90A is not common, similar cable were used with 

C.B 200A 

4x70mm2 for clarifies group 2 

Where I = 80A, L = 140m, ∆U (admissible) = 1.5% 

50. In MDB2 – why using the same cable size for both transformers 1600 and 2000KVA, check and 

correct where necessary. 

Please refer to drawing (№ DD_layout_E005_C) and (DD_layout_E005_C) where the transformers 

are 3(1250 KVA) +630 KV. 

51. The a.m remark is applicable to the generators 1250 and 1500KVA. 

Please refer to drawing (№ DD_layout_E005_C) and(DD_layout_E005_C) where the generators are 

P1375E/(1100 KW), and P1875E/(1500 KW). 

52. The Ratings of Ampere meter 1500A while the max current 2500A? Check and correct, in general it 

is prefer to have digital meters. 

Please refer to drawing at the item 50 

53. Revise the cable ratings of the blowers. 

The cable rating of the blower are 2(3x300 mm2)+150 mm2 represent (3 phase + Earthing). 

54. The RCD is 4x40A but not 3x40A in one panel board. 

The RCD is 4x40A but not 3x40A. 

55. The panel board in substation No.1 has no name. 

It’s name LP/SS1 (Lighting panel of substation № 1).(DD_Layout_E_004_C) 

56. All directly buried cables or pipes needs mechanical protection by suitable way. 

We can use the mechanical protection. See drawing (№ DD_layout_E001_C) &(№ 

DD_layout_E002_C). 


57. The cable tray and power outlets on Dwg E-002 is not shown clearly compared to the layout, these 

items should be viewed while the layout is faint or shaded. Comments taken into account in the 

DD report 

58. The Panel board D.P/CLAR-G2, it is already notified that the cable size 4X70mm2 is not matched 

with C.B 63A, these panels to be reviewed and corrected. 

MCCB (NZMB1_A100) for DP/Clar_G2. 

Where L = 140m, ∆U (admissible) = 1.5% 

59. The Isolating Switch is using m.c.b but not to disconnect power only, please verify if it is for protection 

or isolating. 

MCB is using isolation switch 

60. The Panel DP/B.W-C.V, the rating of the main C.B is 100/90A while there are bigger loads, check 

and correct. 

Valves used have small power 

61. The panel boards shall include signal lamps for operation indication beside the On/Off switches. 

See plan (№ DD_TER_E_003_C). We used double actuators with indicator light 

62. The Panel SDB/S.F, L.P/S.F check the C.B and Cable ratings and Text size.. 

The checking is made at the SDB/S.F. see drawing (№ DD_TER_E004_C). LP/SF is checked on 

rating of C.B and size of cable. 

63. The Panel L.P/ADM.F How using cable 5x25mm2 with C.B 40A? Main C.B should not be equal to 

branch one despite difference in the short circuit current capacity. 

Section of cable 5x25 mm2 determined according the voltage drop.∆U (admissible) = 1.5%. 

64. Why using High Bay Light Fittings 250W into the prayer room- Ground floor. 

Modified at the drawing (№DD_B41_E001_C) by luminaries 2x36 W fluorescent lamp. 

65. Lightning system drawings is not included. 

Please refer to drawing (№DD_Layout_E004_B)and(№DD_Layout_E010_B) 

66. No security, perimeter security, access control, .etc. Are foreseen. Comments taken into account 


67. Why using two locations for the M.V substations? The detailed layout to be included as well. 

We used 2 substations at the site 

a) Near the consumption of power aeration tanks. 

b) It is difficult to find area for 2 substations and generators, fuel tank. 

See plan (№DD_Layout_E001_C) 

68. Layout for the route of M.V O.H.T.L to be included showing all details. 


Please refer to drawing (№DD_Layout_E007_C) site plan and to route of overhead line from the 

line between (Khanyouns - Rafah) 

69. Where is the feeding power line from generator No.2 to substation No.2 on the layout? 

Please refer to drawing (№DD_Layout_E003_C) 

70. The Extra Low Voltages installations such as: computer and data, Telephone and sound, etc. are not 

shown? The main telephone cable route and details to be shown. 

Computers, telephone installed at the administration building, for main telephone cable route see 

(PALTEL № DD_Layout_E007_C) and administration plan (№DD_B41_E001_C). 

71. Propose recommended spare parts list for specific electrical items ( if any) 

Refer to the BOQ, section 15.6 

General Electrical Notes: 

72. All cables and circuit breakers to be revised and corrected accordingly. Comments taken into 


73. Missing cable sizes for some panels has to be determined. Comments taken into account in the 

DD report 

74. Load schedule for main and branch panels to be included. Comments taken into account in the 

DD report 

75. The TEXT in single line diagram drawings to be revised and corrected where needed to look more 

legible. Comments taken into account in the DD report 

76. The electrical layout should be clear compared to the plan and remove or shaded the unnecessary 

lines. Comments taken into account in the DD report 

77. There should be general legend for the electrical symbols used in the drawings. Comments taken 


Comments of CMWU 

1. General & Civil 

1. A general site layout drawing should be added to show the TP at its location and the surrounding 

facilities. 


2. There are two Drawing with the same Dwg No. DD-GD-006-B (Hydraulic profile). Give different 

Number. 


3. It is not clear wither the cement used in the design is sulfate resistance cement or not, in the case of 

ordinary Portland cement there should be a clear statement for the internal walls coating type ( Epoxy 

paint). 

Refer to the civil drawings head, and to the DD report. 


4. Too many civil details are not available: 

 

 

Pipe trenches, supports, crossings, entering walls, Comments taken into account in the DD 

report 

Thrust blocks 

Comments taken into account in the DD report, refer to drawing DD - P - 028- A & DD - P - 029- A 

 

Curb stones 

Tthere is no curb stone in the project 

 

General layout with storm water collection system. 

Comments taken into account in the DD report, refer to drawing DD - DET - 003 _ C 

 

Concrete lintels 

Comments taken into account in the DD report, refer to drawing DD - DET - A - 004 _ B 

 

Machines fixation to concrete basis. 

Comments taken into account in the DD report, where required 

 

Water stopper. 

Comments taken into account in the DD report, where required 

2. Pretreatment 

5. Revise the hand railing layout at drawing No DD-PRE-A-001_B. 


6. Electrical Equipment room is located under the screening channel, it is expected to be perfect, but 

through supervising all the pump stations at Gaza strip all the electrical equipment below the 

screening were flooded, it is preferable if all the electrical equipments are above the ground, better if 

it is at first floor level. 


7. Drawing No. DD-PRE-A-001_B. there is no access for the Storage area at level 58.00. 


8. More details are required for screening skid and the railing shown at some plans. 


9. It is not clear how the screens will be lifted from the top of the building, (crane or What?). 


10. DWG, DD-Pre-C-001-B, revise F1,F2,F3 bottom foundation (should be notified by B –bottom- not T 

top). 


11. DWG. DD-PRE-M-001_B the storage area is named as Electrical equipments room, revise and 

correct. 



3. Aeration Tanks: 

12. Provide details for the expansion joint at walls. 


13. While you are using tie beams at the top of the walls at the tank, it looks like the external walls are 

designed as a cantilever walls with a thickness of 900 mm, if another alternative of design with 

consideration for these tie beams and walls as a simply supported slab, the thickness of the external 

walls will be reduced 40%. 


14. Ribbed slabs for the platforms are not preferable as the block will be in direct contact with the vapor 

of the wastewater. 


15. DWG No. DD-Aer-C-004-B revise section name AA to be BB. Comments taken into account in the 

DD report 

16. There is no stair or ladder to enter inside the tank for maintenance works. 


17. The tank should have a low level pipe or sump pit to empty it at the case of maintenance, the lowest 

pipe level is 51.04 which is 2.41 meter above the floor will remain full of water. 


18. In the plan at DWG DD-AER-M-001_B it show 62 air nozzles while at the section at DWG DD-AER- 

M-003_B show 31 nozzles, please check. 


19. There is no details for the nozzles also no details to show the support of the nozzles at the ground. 


4. Clarification Tanks: 

20. It is not clear how the sludge is collected in the middle of the clarifier, if the sludge floating by 

bubbles, how to direct it to the center pier. And the sludge close to the external wall will float close to 

the clarified water exit. 


21. The top level of the front Metallic weir at section EE DWG DD-CLA-M-022-B is not shown, it looks 

like it is 54.69 which may allow scum to move to the clarified effluent, please check. 


22. Revise section F-F at Drawing DD-CLA-A-002-B, the thickness of the wall show 2.22 while it should 

be 0.55, please revise. 


23. Clarifier Effluent collection well at DWG DD-Cla-A-003-B the raft level show 52.12 and at DWG DD- 

GD-006-B the WL is 51.68, please check. 



24. Also the concrete top level of DW3 show 54.00 while the water level at the clarifier 54.69, at the case 

of water balance at the manhole and the clarifier the water will start flooding out of the well, check to 

raise the concrete level to 54.90. 


25. DWG DD-Cla-C-006-B revise section AA to be Section BB. 


5. Sand Filter: 

26. In general there are no close details for the materials under the sand, and how to protect sand from 

going down. 


27. Why it is chosen to pump the dirty water up to the sand filter, as we are building the structure under 

the ground we can go down another 3 meters and let the water flow by gravity from the clarifiers to 

the sand filter without pumping. 


28. The location of sections EE, FF, GG non of them show the sand filter and the layers of sand, Why? 


29. Section EE should show pipes at the left hand side, where is the pipe please show. 


30. In plan A-A and section DD at DWG DD-TER-M-001-B the longitudinal channel beside the sand filter 

will be filled with dirty water without passing to the sand filter. 


6. Sludge Drying Beds: 

31. Detail B DWG DD-DEW-C-004-B the perforated pipes appears not to be continuous while at the plan 

at DWG M004 all the pipes are connected through T, please revise. 


32. The perforated pipes if covered with Geo-textile fabric will be better. 


33. Extend the concrete splash slap another 50cm. 


34. Through the cleaning of the dried sludge by machines part of the graded soil will be loosed and the 

loader will destroy the layers, it would be better if the slab is constructed by strips of reinforced 

concrete and empty places filled with the same layers in the drawings and keep the width of the 

empty spaces less than the width of the loader wheels. 



7. Mechanical Works: 

35. The sand filter back wash water should return back to bass through the grit chamber to remove the 

sand come out from the back wash process. 

It is exactly the case in the design, refer to dwg. DD-PRE-M-002_B and dwg. DD-TER-M-001_B 

36. It is not clear what is the final destination and treatment for the collected grease and the scum that 

will be collected from the grit chamber and final settling tanks. 

As indicated in the Initial Design report and in the Detailed Design report, the grease quantities 

are evacuated by vacuum tanks to land fill. 

37. The supernatant should return back to bass through the secondary treatment 

It is exactly the case in the design, refer to dwg. DD-PRE-M-002_B and dwg. DD-THI-M-002_B. 

except that the supernatant will be pumped to the entrance of the grit removal channel. 

38. Aeration system used (Diffuser) is complex system, and it is costly in operation and maintenance 

(many mechanical equipments) it is better if used as a rotary surface, which need less operational 

and maintenance costs (Can be clarified; selection had based on the Initial Design Report). 

Aeration system used (diffusers) has been justified, clarified and apporved on the Inital design 

report. This sytem is very efficient and allow good aeration in the aeration tank. 

39. Blower room needs ventilation, check adding Exhaust fans. 


40. To reduce the noise of the blowers it should be in a canopy and underground. Comment taken into 


41. There is no slope between the screen chamber and the grit removal as both are having a water level 

of 57.47. 

There is a slight drop in the water elevation. In the bar screen water level 57.47 and water level in 

the grit removal channel is 57.46. 

42. It is not clear how the designer is going to control the velocity after the screens, It may is exceeds 1 

meter /sec. 

An electronic load limiter is installed in each channel 

43. There should be a manual bar screen at the bypass channel. 

No bar screen at the bypass channel 

44. Regarding the washout valves (Drain valves) it is clear that the quantity of the water is so large, there 

should be a certain technique to open the valves in order to save the operator life. 

No need for that 


8. Electrical Works : 

45. Check the rating of the power factor improvement. 

Automatic power factor system different caliber of KVAR from 20KVAR to 50, 60 KVAR will be 

supply the network P.F. (0.9 to 0.93). 

46. Is there a load calculation sheet. 

Refer to annex 5 

47. The required power is high and shall be checked with the GEDCO. 

GEDCO proposed the system with 2 transformers at each substation, where the responsible of 

drawing at GEDCO says that they can give us 3 transformers 1250KVA and 630KVA. 

48. Where is the detailed drawing the high tension side. 

See plan (№ DD_Layout_E007_C). 

49. The short circuit rating of the Main Bus bar in MDB1 is 85KA but in MDB2 it is only 55KA, why???? 

The switching capacity of main bus bar from generators and transformers is (80 to 85 KA) see 

plan (№ DD_Layout_E005_C)and(№ DD_Layout_E006_C). 

50. There are no current meters for several pumps (each blower for example) why?? 

See plan (№ DD_Layout_E005_C) for blowers (Aeration tanks) and plan (№ DD_TER_E004_C) for 

sand filters. 


0.2. ANSWERS TO THE UNDP’S COMMENTS DATED 12TH JUNE 2010 

0.2.1. SHEET 1- DETAILS DESIGN REPORT 

Chapter 2 

1. Page 17, clause 2.3.2.2 Elimination of Nitrogen, in the table, in rows no. 5, no. 6, and no. 9, correct 

the numbering sequence of N4 = N1-N2-N3-N4, to be N5 = N1-….., etc... (Re-check the equation 

of N7, (N6 = N3+N4+N6) in the table in page 59 of the RDD Report). Comment taken into 


2. Page 34, clause 2.5.2, thickeners, delete the number 227 m2 in front of the phrase “Total Surface” as 

227 m2 is for the unit surface only. (Not modified in page 76 of the RDD Report). Comment taken 


Chapter 3 

3. Page 40, clause 3.3.2 screening, in the table check and verify the screen opening of 10 mm, verify 

concerning catching the excess sand in the waste water inflow as discussed in the meeting of 9 

Feb.2010 in the PWA. (Not modified in the table in page 85 of the RDD Report). Comment taken 


4. Page 41, clause 3.3.3, Grit /Grease Removal, automatic alternating scraper made of 304 L stainless 


(Not modified in page 86 of the RDD Report, third paragraph). Comment taken into account in 


5. Page 43, clause 3.4.3. air production plant, paragraph no 2, 3, check the” turbo-compressors” 

capacity of 19,000 Nm3/h. verify it with the nominal air flow of 18,000 Nm3/h in page 21 and the table 

in page 22. For the ND 600 304 L stainless steel pipes and other related pipes in contact with the 

waste water, check for the same above comment, and 316 stainless steel to be used to prevent 

corrosion whereas appropriate. (304 SS, not modified in page 88 of the RDD Report). Comment 


6. Page 47, clause 3.6.7, gravity thickeners, 1st paragraph, check the capacity of the recovery pumps 

45 m3/h in phase 1 and 73 m3/h in phase 2, and as set in page 35 of pump capacity of 80 m3/h. 

please verify and redraft for more clarity and to avoid confusion in the selection of the pump capacity. 

The same for the pump capacity of 132 m3/h in the second paragraph, and comparing it with pumps 

capacity of 80 m3/h as in page 33. (Check if clarification done in page 92 of the RDD report). 


7. Page 48, clause 3.6.9, sludge composting, second paragraph, a mixture of sludge …. will be 

composed using a front loader… is the loaders needed and similar equipment include in the 

summary cost estimates to be taken into consideration for resource mobilization. The same for the 

two front end loaders as set in the fourth paragraph of page 49. The same as for the vacuum trucks 

for grease removal. ( Check BOQ). Included in the BoQ, Bill 1 

8. Page 50, clause 3.7.1.1. scope of works, 5th paragraph, please correct “intrumentation” to 

“instrumentation”. (Not modified in page 95 of the RDD Report). Comment taken into account 



9. Page 54, clause 3.7.2.5 SCADA system database configuration, second paragraph, the following 

shall be displayed to disc for display on the SCAD system. “ the integrated hourly, daily, weekly, 

monthly and yearly total outlet flow to treatment.. please re-draft for more clarity, is it including the 

effluent from the treatment plant as well. (The re-drafting of the specific comment is not clear in 

page 99-100 of the RDD Report). Comment taken into account in the DD report 

10. Page 68, clause c., sand and filtration –washing; 7th row, please verify or correct the word “ to rincing 

water”. The same as for “Automatic filter washing gestion” and “eletropump” in the fourth paragraph. 

(Not corrected in page 113 of the RDD Report). Comment taken into account in the DD report 

11. Page 79, clause 3.8.1, power supply; please specify the exact length of the electrical line to the KY 

WWTP, as about 2500 m is sound not accurate. (Please recheck the distance reference to survey. is 

it exactly 2500 m? ( page 124 RDD Report). Comment has been taken into account 

12. Page 83, clause 3.9, civil works, second paragraph, the metallic structures (grating, handrails, 

covers and stairs, will be from aluminum or hot galvanized iron for heavy pieces. Please check 

against corrosion and may stainless steel to be used to prevent corrosion whereas appropriate. 

(Check whether it is 304 or316 in page 133 of the RDD Report,1st paragraph). Comment taken 


13. Page 87, clause 3.9.1.3.4, design strengths, second paragraph, check and verify the strength of 

B300 and cement content with the strength of 25 Mpa as set in the table for the main applications. 

(Check the table of Page 137 of RDD report for modified strength of 30 MPA and check clause 

3.10.1.9 page 141 for the same comment to avoid confusion). Comment has been taken into 

account 

14. Page 98, clause 3.9.4.1.2 Grit removal basins. Check the dimensions of length 16.85m, width 4 m 

and depth of 3.6 m with the figures mentioned in page 11, clause 2.2.2 for discrepancy. (Verify the 

figures in page 148 of the DDR for compatibility with page 53 of the RDD Report). Comment 


15. Page 105, clause c, cleaning access connections (blow off connections). Please check and specify 

the applicability of using blind flanges in case it is located in paved roads, or in the future when roads 

paved. (Still not clear how it will be opened in paved roads). It will be removed by screwing 

the bolts out , see drawings DD-P-027 

16. Revise pages 159 -165 for: 

To check the clay depths in page 161, clause B, section a. reference to last geotechnical investigations. 

Verify and compare the flow rate of 26,664 m3/day in page 162 RDD, with flow as page 46 DDR if it is 

o.k. 

Add or complete missing data for section E, Access roads, in page 165 RDD. 

Comment has been taken into account. 

Chapter 6 

17. Page 123- 125, clause 6.1; Bidding Procedures; elaborated justification is needed concerning the 

selection of the FIDIC Red Book as per the relevant correspondence with UNDP. Need clarification. 

Page180 in the RDD report, please check if the FIDIC (MDB Harmonized Edition, March 2006) 

will be used as it is justified in the text, or the FIDIC Red Book 1999 as set in the Tender 

Documents. The text is not clear to reflect what finally agreed up with UNDP to go to the 

FIDIC Red Book. The first edition of the Detailed Design report was submitted to UNDP, the 8 

of February 2010. UNDP confirmed us by email to used FIDIC Red Book, the 28 February 2010. 

The Draft Tender Docmuent was submitted on the 25 March 2010 based on the FIDIC Red 

Book in accordance with the email. 


18. Page 181in the RDD report, package 4 is not included in the last paragraph. Comment taken into 


19. Page 128, clause 6.3.1.1, concrete to cast, second paragraph, check and adjust the figure 30m 3/j to 

m3/day. Not modified in page 182 in the RDD report. Comment taken into account in the DD 

report 

20. Page 128, clause 6.3.1.2. Earth work, check the amount of excavation and backfilling of the 

infiltration basins based on the last surface geotechnical investigations done on Al Fukhari infiltration 

site. The calculation and durations in page 182-183 in the RDD report still base on the old 

figures. Need check and modifications due to change of quantities. Comment taken into 


21. Page 128, concerning the 8 months duration for supply equipment and pipes, clarify the 0.5 months 

clearance for administration clearance in Ashkelon, if it is mean a harbor it could be Ashdod or Haifa 

harbor not Ashkelon. Not modified in page 183 of the RDD report. Check for Ashkelon. 


22. In Page 186 of the RDD report, in the MS bar implementation schedule, modify the name of 

the fourth package from infiltration basins to WWTP Power Connection as it is repeated for 

C3 and C4. Comment taken into account in the DD report 

Appendix 4 

Civil Structure Calculations 

23. According to the codes there is an allowable margin for accepting the concrete strength after testing 

and variance in the strength is allowable to a certain extent. Accordingly, B250 is considered too low 

to be accepted for such important facility; pleas check. Reference to the consultant 

recommendation and design, please check this point with what mentioned in the table of 

page137 and page 141 in the RDD report to avoid confusion between using B250 and B300 

and making it clear. Comment has been taken into account. 

Drawings 

24. The remaining comments on drawings set will be succeeded in a separate sheet. 


0.2.2. SHEET 2 – DRAWINGS 

* Plan Name Plan No. Status Comments Consultant Response 

Civil Works 

A - General Comments 

1 √ There is no base map drawing available or contour line and 

site plan level was not shown. 

2 X A general site layout drawing should be added to show the 

Treatment plant at its location and the surrounding 

facilities. The given comment checked and the consultant 

needs to follow it up with the municipality to finalize it. 

3 √ The drawings have to be arranged in accordance with the 

numbers shown on the layout drawing. 

This item is under the 

responsibility of Khan 

Younis Municipality. 

4 √ The expansion joints details has to be clearly shown. 

5 X The types of crops and irrigation system have to be 

included clearly in the treatment plant. Not clear well in 

added drawing, figures and dimensions and are not clearly 

readable and no details. 

6 √ 

√ 

7 √ 

√ 

The boundary walls and main entrance details are not 

shown. 

The guard room does not exist in any drawing. 

Check and correct some plans name to be fit with the 

contents of plans. 

There are two Drawing with the same Dwg. No. DD-GD- 

006-B (Hydraulic profile). Give different Number. 

8 √ Missing general buildings setting out layout with clear 

dimensions and distances with respect to specific bench 

mark 

9 √ Missing design of generator foundations 

The Scale of figures and 

dimensions is modified 

in the revised drawings 


10 √ Missing design of fuel tank and it's foundation 

11 √ Missing typical detail of steel grating and steel handrails. 

Check the thickness and depth of gratings bars and check 

the used aluminum material for strength. 

12 X Missing design of land scaping elements i.e walk ways, 

edge beam, curbstone …etc. throughout the site of plan. 

Check how the tiles at road edges will be retained. Design 

and details of edge beams need to be added with roads 

cross sections. 

13 X Missing design of access road to the plant. Included as set 

in item 11 of task 1 of TOR. 

14 √ Missing sheet # DD-PRE-A-005_B 

15 √ To think about raising the strength of concrete in order to 

suit the aggressive environment and specify the strength 

for walls and other elements in the side notes 

16 X Quantities measurement report should be provided. 

Included as per Task 3 of the TOR. 

17 √ Missing sheet # DD-THI-A-002_B 

18 √ Sheet # DD-Layout-E-004_B is repeated with different 

contents 

19 √ Expansion joint details and justify usage of 10 cm wide 

expansion joint. 

The dimension and 

thickness are checked 

and No problem. 

Typical details are 

added. 

The access road to the 

plant from Sofa road to 

the landfill entrance is 

existing and paved, 

however the road 

between the TP and the 

landfill was backfilled 

with solid waste from 

many years ago. Anyway 

the design includes 

typical cross section 

details which is 

appropriate for the 

traffic loads. 

The BOQs are prepared 

as per item 7 of task 3 of 

the TOR. No reports 

needed to be added 


B - Comments on the 

Drawings 

20 Pretreatment Building DD-PRE-C-003 _ c √ The reinforcement in the rib is one bar on the plan but in 

section a-a is 2 

21 Pretreatment Building DD-PRE-C-005 _ c X Detail for intersection of reinforcement in walls should 

reflect the correct position of the steel reinforcement with 

special details outlining the proper arrangement of steel 

bars. Some intersections detailed but other intersections in 

section CC need to be detailed as steel is not clear. 

22 Pretreatment Building DD-PRE-C-006 _ c X Specify for what element the frame section FF is. It's not 

clear in drawing DD-C002. The frame section still not clear 

√ related to what, please check. 

Done and added to the 

revised drawings 



Detail D in the footing drawings is not displayed in the 

relevant detail drawing. 

23 Pretreatment Building DD-PRE-A-001_B Revise the hand railing layout at drawing The hand railing is 

revised and No problem 

found. 

24 Pretreatment Building DD-PRE-A-001_B There is no access for the Storage area at level 58.00 The access door is clear 

in the drawing ( at axis 

F) 

25 Pretreatment Building DD-Pre-C-001-B Revise F1,F2 &F3 bottom foundation (should be notified Done in the draft 01 

by B –bottom- not T top) 

26 Pretreatment Building DD-PRE-M-001_B The storage area is named as Electrical equipments room, 

revise and correct. 

Done in the draft 01 

27 Pretreatment Building Electrical Equipment room is located under the 

screening channel, it is expected to be perfect, but 

through supervising all the pump stations at Gaza 

strip all the electrical equipment below the screening 

were flooded, it is preferable if all the electrical 

equipment are above the ground, better if it is at first 

floor level. 

More details are required for screening skid and the 

railing shown at some plans. 

It is not clear how the screens will be lifted from the top 



of the building, (crane or What?) 

28 Aeration Tank DD-AER-C-002_B X Missing details of steel reinforcement at the intersections 

Specify the embedded steel length of the circular wall into 

the 90 cm wall at the intersection. Details of steel 

reinforcement in the intersections are still not clear. 

29 Aeration Tank DD-AER-C-003_B √ revision of the number of reinforcement bars in section 2-2 

30 Aeration Tank DD-AER-C-004_B √ 

√ 

√ 

√ 

√ 

X 



√ 

√ 

√ 

X 

More detail is needed for the weir in detail 1 

The name of sections to be revised 

Check the level at Section C-C 

Check the reinforcement detail around the opening in 

Section C-C 

Correct the dimensions scale 

Correct the no. of rebars per meter length in the detail of 

W11 and W3 

Why not to apply the steel distribution for the other walls. 

Details of steel reinforcement and distribution for other 

walls need to be clarified as done for W11 and W3. 

There is discrepancy in the reinforcement steel in section 

A-A and Detail 1. It's repeated in Drwgs. 

Review the hidden and intersected walls in Section A-A 

The main steel is usually the vertical ones, so the main 

steel shall be external. Review the position of steel in many 

of the Dwgs. Please re-check. The given explanation is 

checked but why the same principle is not applied for the 

foundations. 

Review the water stop & expansion joint in the walls and 

foundation 

The work will dictate intermediate construction joint in the 

walls. Details in this regard to be considered. 

Check the number of steel bars in Detail 3. 

33 Aeration Tank DD-AER-C-014_B √ Specify the thickness of the landing above the column 



The details could be 

done by the Contractor 

as Shop drawings. The 

drawings contains 

sufficient details for 

tendering as per task 3 

of TOR. 



34 Aeration Tank DD-AER-C-018_B √ Show the dimensions and steel detail for the trenches 

35 Aeration Tank DD-AER-C-020_B √ Show the reinforcement for middle foundation in frame 


36 Aeration Tank DD-AER-C-004-B Revise section name AA to be BB. Done in the draft 01 

37 Aeration Tank DD-AER-M-001_B It show 62 air nozzles while at the section in DWG DD- 

AER-M-003_B show 31 nozzles, please check 


38 Aeration Tank Provide details for the expansion joint at walls. 

 

 

 

 

 

While you are using tie beams at the top of the 

walls at the tank, it looks like the external walls are 

designed as a cantilever walls with a thickness of 

900 mm, if another alternative of design with 

consideration for these tie beams and walls as a 

simply supported slab, the thickness of the external 

walls will be reduced 40%. 

Ribbed slabs for the platforms are not preferable as 

the block will be in direct contact with the vapor of 

the wastewater. 

There is no stair or ladder to enter inside the tank 

for maintenance works. 

The tank should have a low level pipe or sump pit to 

empty it at the case of maintenance, the lowest pipe 

level is 51.04 which is 2.41 meter above the floor 

will remain full of water. 

There is no details for the nozzles also no details to 

show the support of the nozzles at the ground. 

39 Clarification Tanks DD-CLA-A-001_B √ Review the required diameter for effluent line 

Show the detail of the components of the handrail 

v 

40 Clarification Tanks DD-CLA-A-002_B X 

√ 

√ 

√ 

√ 

X 

X 

There are many discrepancies in dimensions and scales. 

Please re-check as discrepancies still exist. 

Check the radii in Plan FF with that in plan DD-CLA-A- 

001_B 

Add detail for SS plate fixation with the concrete in Section 

FF. Please re-check the names of openings as indicated 

on bolts. 

Provide enough cover for the underground pipe in Section 

E-E 




Show more detailed dimensions to section E-E and D-D 

Show more detailed dimensions for the weir and cylindrical 

barrier. Clarify the thickness and material type of the 

metallic weir. 

Show the benching at the bottom of the well in section F-F. 

Still not illustrated in the section or detailed. 

41 Clarification Tanks DD-CLA-C-002_B X 

X 

X 

Review the dimensions to be fit with other sections and 

other plans. Check dimensions in section CC and DD and 

with section FF in DD-CLA-A-002-B. 

Clarify the steel reinforcement in section C-C. Clarify the 

steel reinforcement in section DD and add shrinkage steel. 

Show the pipe openings in section C-C. Re- check as the 

pipe opening still not shown in the concrete wall as per the 

related section. 

42 Clarification Tanks DD-CLA-C-003_B √ Check radii with previous drawings 



43 Clarification Tanks DD-CLA-C-004_B √ 

√ 

√ 

Show the pipe openings penetrating the pit walls 

Specify the depth of beam under the stair landing 

Check the reinforcement at the bottom corners in section 

CC and DD 

44 Clarification Tanks DD-CLA-C-005_B √ Show the pipe inlet in section EE 

Check the dimensions of scum tank with CLA-A-001B 

Show the stair width between degazing and scum tanks 

45 Clarification Tanks DD-CLA-M-022-B The top level of the front Metallic weir at section EE DWG 

DD-CLA-M-022-B is not shown, it looks like it is 54.69 

which may allow scum to move to the clarified effluent, 

please check. 

46 Clarification Tanks DD-CLA-A-002-B Revise section F-F at Drawing DD-CLA-A-002-B, the 

thickness of the wall show 2.22 while it should be 0.55, 

please revise. 




47 Clarification Tanks DD-CLA-A-003-B Clarifier Effluent collection well at DWG DD-CLA-A-003-B 

the raft level show 52.12 and at DWG DD-GD-006-B the 

WL is 51.68, please check. 


48 Clarification Tanks DD-CLA -C-006-B Revise section AA to be Section BB. Done in the draft 01 

49 Clarification Tanks It is not clear how the sludge is collected in the middle 

of the clarifier, if the sludge floating by bubbles, how 

to direct it to the center pier. And the sludge close to 

the external wall will float close to the clarified water 

exit. 

50 Sand Filter DD-TER-C-001_B X 

51 Sand Filter DD-TER-C-002_B √ 

√ 

52 Sand Filter DD-TER-C-003_B √ 

X 

√ 

Also the concrete top level of DW3 show 54.00 while 

the water level at the clarifier 54.69, at the case of 

water balance at the manhole and the clarifier the 

water will start flooding out of the well, check to raise 

the concrete level to 54.90 

The walls separating the two phases should not be 

permanently closed. Identify the mechanism to connect the 

two phases in the future. Still not shown in drawings. The 

comment is to suggest and to show mechanism to make 

the future connections to avoid fracturing the concrete in 

future. 

In general the sections presented didn't illustrate well the 

structural details in the filter rooms. Some of the sections 

can be deleted and new ones added 

Show the inlet opening 

Specify the stirrups reinforcement in detail 1 

Show the columns and walls location on the background 

Show the reinforcement around the openings. The given 

drawing checked for section KK but stel reinforcement not 

clear. 

53 Sand Filter DD-TER-C-004_B √ Specify the stirrups reinforcement in detail 1 

Show the reinforcement details at the intersections 






54 Sand Filter DD-TER-C-005_B √ All sections should be presented architecturally with full 

dimensions in separate sections 

Specify the diameter of spiral reinforcement in circular 

columns 


55 Sand Filter DD-TER-C-006_B √ Review the dimensions 

56 Sand Filter DD-TER-C-008_B √ There are duplicated details. They consume space. 

57 Sand Filter DD-TER-C-009_B √ All sections should be presented architecturally with full 

dimensions in separate sections 

58 Sand Filter DD-TER-C-010_B √ Only small difference between the two frames. Avoid 

duplication of details 

Specify the stirrups reinforcement in section 1-1 

59 Sand Filter DD-TER-C-011_B √ Check the stirrup spacing at max. shear (adjacent to the 

columns) 

Check the bottom reinforcement of B5 with that in section 

1-1 

60 Sand Filter DD-TER-C-012_B √ Check stirrup at max shear 

Details in this sheet could be integrated with the previous 

sheet 

61 Sand Filter In general there are no close details for the 

materials under the sand, and how to protect sand 

from going down. 

 

 

 

Why it is chosen to pump the dirty water up to the 

sand filter, as we are building the structure under 

the ground we can go down another 3 meters and 

let the water flow by gravity from the clarifiers to the 

sand filter without pumping. 

The location of sections EE, FF, GG non of them 

show the sand filter and the layers of sand, Why? 

Section EE should show pipes at the left hand side, 

where is the pipe please show. 

In plan A-A and section DD at DWG DD-TER-M- 

001-B the longitudinal channel beside the sand filter 

will be filled with dirty water without passing to the 

sand filter. 



62 Air Blowers DD-TER-C-014_B 

DD-TER-0-C-017-B 

of Rectified DD 

Drawings. 

63 Air Blowers DD-TER-C-015_B √ 

√ 

√ 

√ 

√ 

√ 

√ 

X 

Where's Reinforcement of the columns 

Check the Reinforcement in the cantilever 

Add detail of the joint between the back wash room and 

sand filter building 

Show the filler (polystyrene board 2.5 cm thick) in the 

expansion joint sec D-D. Please check as the given details 

in not reflecting it as an expansion joint. 

Check the details of B1 

In B1 check the stirrup spacing at max shear (adjacent to 

the column) 

Correct the name of sections and B4 dimension By 

engineering sense the reinforcement of the two spans of 

B4 is not the same. Check the design. 

64 Sand Filter DD-TER-M-002_B X Think about connecting phase II to the operating system in 

the future. Clarify details of that connections required for 

future expansion without disturbing the sand filters 

operations. Still not clear .The same comment as of No. 

50. 

65 Gravity Thickeners DD-THI-A-003_B 

DD-THI- A- 002-B of 

rectified DD 

Drawings. 

66 Gravity Thickeners DD-THI-C-002_B √ 

X 

67 Gravity Thickeners DD-THI-C-003_B √ 

X 

X 

√ 

More detail for S.S basin is needed. Dimensions, 

thickness, etc. need clarification. 

Correct the scale in section AA and FF 

Steel compensation around the opening is required? 

In section AA there is unclear steel. Some steel details are 

not clear, shape of bends and dimensions, etc... 

There is no difference between GB2 and GB3? No need 

for duplication 

Clarify the expansion joint Detail. The same as previous 

comment of No. 62. 

68 Gravity Thickeners DD-THI-M-001_B √ Add Details for supernatant return basin 











69 Gravity Thickeners DD-THI-M-003_B √ Correct the Scale 

70 Sludge Drying Beds DD-DEW-C-002_B √ 

√ 

√ 

Correct the dimension of concrete splash Slap 

This detail is not compatible with location of section B-B 

Variable because the bottom of the channel is sloped but 

how much? 


71 Sludge Drying Beds DD-DEW-C-003_B √ 

X 

√ 

√ 

√ 

X 

Is the joint is totally filled with mastic or using other 

material? 

Where is the joint on the plan and every how much should 

be repeated? It is not clear for walls and how much should 

be repeated. Correct and adjust the relevant given 

drawing. 

Determine what holding the pipe in section CC. 

Show the excavation level of wall foundation 

The depth of the channel is variable because the bottom of 

the channel is sloped, but how much is the slope? 

Check the dimensions on section DD. Compare with 

Section DD for discrepancies. 

72 Sludge Drying Beds DD-DEW-C-004_B √ No need for detail B beside the drainage pipe since the 

detail above is sufficient and slightly different. Duplication 

of drawing? 



73 Sludge Drying Beds DD-DEW-M-001_B √ This sheet does not differ from DD-DEW-C-001_B. Avoid 

duplication. 

74 Sludge Drying Beds DD-DEW-M-002_B √ This sheet does not differ from sheet DD-DEW-C-002_B 

except section B_B which is shown in D-D DEW-C-003_B. 

Duplication? 

75 Sludge Drying Beds DD-DEW-M-003_B √ Show more detail about pipe support. 

76 Sludge Drying Beds DD-DEW-M-004_B √ 

√ 

How by what mean sludge is to be collected from down 

stream and goes to pump well? 

Show the perforation spacing and diameter in detail 1. 

77 Sludge Drying Beds DD-DEW-M-005_B √ It’s enough to present levels at different sections in a small 

table or determination of slope. No need for this sheet. 

78 Sludge Drying Beds Detail B DWG DD-DEW-C-004-B the perforated 

pipes appears not to be continuous while at the plan 

at DWG M004 all the pipes are connected through 

T, please revise. 

The perforated pipes if covered with Geo textile 

fabric will be better. 

Extend the concrete splash slap another 50cm. 

Through the cleaning of the dried sludge by 

machines part of the graded soil will be loosed and 

the loader will destroy the layers, it would be better if 

the slab is constructed by strips of reinforced 



79 Compositing Area DD-COM-A-001_A 

DD-COM-C- 001-B 

80 Compositing Area DD-COM-A-002_B √ Check the slopes 

X 

concrete and empty places filled with the same 

layers in the drawings and keep the width of the 

empty spaces less than the width of the loader 

wheels. 

Missing detail for ramp and channel details? Check the 

amendments done for accuracy of figures and dimensions. 

Details are needed. 



81 Compositing Area DD-COM-A-003_B √ Check the slopes 

82 Compositing Area DD-COM-C-001_B √ 

X 

83 Compositing Area DD-COM-C-002_B √ 

√ 

√ 

√ 

Check the slopes 

Ramp should sustain heavy load trucks and loaders. Clear 

the design. Please recheck the design and the 

reinforcements for heavy load trucks. 

Concrete ground slab reinforcement details are not clear. 

Need to be illustrated? 

More details needed in detail A 

Unify the unit of dimensions otherwise to determine 

whether in m, cm or mm?? 

84 Compositing Area DD-COM-C-003_B √ In detail D, is it filled totally with kalkal or mastic sealant is 

to be used at the faces? 

85 WWTP Administration 

Building 


Building 


Building 


Building 


Building 

DD-BUI-A-001_A √ Show the North direction as long as the elevations are in 

terms of geographic directions. 

DD-BUI-A-004_A √ Complete the layers of roofing in the finishing table 

Is Tyrolean suitable for entrance finishing? 

DD-BUI-M-003_A √ Compare the AC capacity with spaces especially in the 1st 

floor. 

DD-BUI-C-002_A √ Study the supporting system in such square staircase and 

study also the openings so that they don't interrupt the 

supporting beams. 

DD-BUI-C-003_A 

√ 

√ 

√ 

Correct the name of the drawing 

Correct the name of sec 1-1 (Contraction joint detail) 

Revise the dimensions in Ground beams plan 

The design was checked 

and no problems are 

found 



Building 


Building 



92 Details DD-DET-C-001_A 

DD-DET-C-003-C of 

Rectified DD 

Drawings. 

93 Details DD-DET-C-002_A √ 

√ 

√ 

√ 

√ 

√ 

√ 

X 

X 

Correct the discrepancy in the reinforcement steel between 

plan and sections 

It is better to unify the size of haurdy blocks throughout the 

project as long as the slab thickness is the same. 

Check dimensions in detail of GB1 and compare with 

building layout in sheet DD-BUI-C-003_A 

Correct the discrepancy in the reinforcement steel between 

frames and sections. Please check as discrepancies still 

exist in steel reinforcement. Re-check the two sections of 

Frame 1. 

Add more detail for drainage channel. Please re-check the 

whole system of the open channels. The drainage system 

still not clear and re- check its applicability; how water will 

be collected in traps and manholes which could be mixed 

with mud or residuals. 

Missing dimensions and structure design of transformer 

base. 

Dimensions, design? 

Where is the design of the distribution manhole? 

Correct the discrepancy in the reinforcement steel in B1 

and ground slab. 

94 General Layout DD-Layout-E-004_B √ Specify for which building this foundation belongs and 

correct its dimensions? 

95 Infiltration Basins DD-INF-A-004_A √ Sections should show excavation levels as indicated in 

previous sheet. 



The design of open 

channels system is OK 

and usually used in 

similar projects 

96 Infiltration Basins DD-INF-A-012_A √ Determine stripping thickness? 

97 Infiltration Basins DD-INF-A-013_A X Add detail for the apron? Please re-check and add details 

not zooming and verify the dimensions of the zoom. 

98 Infiltration Basins DD-INF-A-015_A √ Show the structural Design of the platform around vertical 

pipe 

99 Infiltration Basins DD-INF-A-017_A √ Where is the boundary of the fence on the plan? 



100 Infiltration Basins DD-INF-A-018_A √ 

√ 

101 Infiltration Basins DD-INF-A-020_A √ 

√ 

Specify the Finishing of the building? 

Check the dia ф 920 mm in the lower plan E.P? 

Add the Finishing Table? 

Specify the external finishing? 


102 Infiltration Basins _ Intel 

Rooms 


√ 

√ 

What's about column reinforcement? 

Specify the dimensions and the reinforcement of the 

inverted beam in section SE 1-1? 

103 Infiltration Basins _ 

Administration Building 


√ 

X 

√ 

Add detail of circular column and its footing. 

Correct the discrepancies in scales. Please recheck scale 

A and scale B. Verify the dimensions of Beams and the 

shape of foundations for discrepancies and please adjust. 

Add supporting footings under the intersections of ground 

beam 

104 Infiltration Basins X Add details for the irrigation networks for agricultural 

purposes of plantations and details of the plantations. 

Please clarify and add details, source of connection, 

dimensions are not readable well and legend need to be 

added. 

105 Pressure Line Survey DD-P-001_A √ Where are R1, R2, and R3 on the plan?. 





106 Emergency & Effluent 

pipe Line 


Pressure Line 


Pressure Line 


Pressure Line 


Pressure Line 


Pressure Line 

DD-P-005_A √ Check the size of diffuser and compare with the pipe going 

to the infiltration 

DD-P-023_A √ Correct the discrepancies in scales? 

Check the items in the table of contents? 

DD-P-025_A √ Reconsider the size of rocks and indicate the total depth of 

respective rocks layers 

DD-P-026_A √ Specify the diameter of vertical pipe in Blow-Off 

Connection 

DD-P-027_A √ Indicate the degree of angle in Thrust Block Type (B) 

√ Add details for check and washing manholes 





1. 

GENERAL 

1.1. REMINDER 

1.1.1. BACKGROUND TO THE PROJECT 

Khan Younis is located in the southern part of the Gaza Strip of the Palestinian territories 

by the Mediterranean Sea. Khan Younis City is considered as the second largest city of 

Gaza Strip. 

Part of Khan Younis’ population is served by the new established public sewer collection 

system. According to information gathered from Khan Younis Municipality, 83% of the 

population of Khan Younis city and 63% of the population in the surrounding area is 

expected to be served by piped sewage system in the year 2025,. 

The remaining unconnected population disposes effluents to cesspits, which are emptied 

regularly by tanker vacuum trucks. Collected septage is then discharged to the sewer 

network through one of the existing manholes. 

At present, the Khan Younis area is not served by any wastewater treatment plant. Most of 

the collected wastewater is transported to the storm water and then to the western 

temporary lagoons, which have been constructed in 2008 in the western part of the city 

(close to the sea) and the wastewater has been discharged to the sea. 

The current wastewater discharge system is considered as temporary emergency system 

and the construction of a wastewater treatment plant is very urgent. 

The wastewater strategic development plan aims at constructing an extendable and 

phased wastewater treatment plant for Khan Younis. 





1.1.2. PROJECT SCOPE AND EXPECTED OUTPUT 

A Joint Venture Consortium between SOGREAH Consultants and UNIVERSAL Group for 

Engineering and Consulting, Gaza has been assigned for Consultancy Services for the 

detailed design of Khan Younis Wastewater Treatment Plant (KY WWTP). 

This assignment is part of the “Construction of KY WWTP Project” and financed through a 

grant from the Government of Japan. 

The Client of this project is United Nations Development Programme (UNDP) / Programme 

of Assistance to the Palestinian People (PAPP). 

The final output of the assignment is to produce a complete set of tender documents for 

the construction of KY WWTP, Phase 1. 

The assignment is divided into 6 tasks as follows: 

• Task 1: Initial Design Report 

• Task 2: Topographical Survey and Geotechnical Investigation 

• Task 3: Preparation of Completed Detailed Design for KY WWTP 

• Task 4: Carrying out Environmental Impact Assessment Study 

• Task 5: Preparation of the Client’s Requirements 

• Task 6: Preparation of Tender Documents for KY WWTP Phase 1 

During the assignment, following reports have been submitted previously to the Client: 

- Inception report, February 2009, report n° 1 31 0 076-R1-Final 

- Initial design report, July 2009, Report n°1 31 0 076-R2-Final-V4 

- Environmental Impact Assessment, January 2010, Report n° 1 31 0076-R3-Final 

Draft 

The present report corresponds to the detailed design phase (Task 3). It is based on 

outcomes of the initial design phase and main decisions taken by the Client and 

counterparts as stipulated in the addendum at the edition of final version of the Initial 

design report. 





1.2. TREATMENT OBJECTIVES 

1.2.1. INLET FLOWS AND LOADS 

KY WWTP project is planned to serve KY Governorate, thus effluents to be treated at KY 

WWTP include effluents from Khan Younis City and effluents from Eastern villages. 

Two horizons are distinguished for KY WWTP: 

• Phase 1: Year 2018 

• Phase 2: Year 2025. 

Effluents to be treated are composed of the following parts: 

- domestic wastewater from population which is connected to the sewer network; 

- septage from population which is not connected to the sewerage network. Septage 

is collected by vacuum trucks and is discharged to the sewer system. Accordingly, 

all effluents are transferred to KY WWTP by the sewer system 

- industrial wastewater 

Effluents arrive at the WWTP by two separate pressure pipes: 

- The first one is coming from the existing pumping station n°8 (PS 8) which is 

located in Al Fukhari area (El Manara neighbourhood) and serves Khan Younis city. 

Total length of the pressure line from PS 8 to KY WWTP is 4,750m. The 

implemented segment of this pressure line is a 24'' diameter steel pipe of 2000m 

length. The remaining part (2,750 m length) is not implemented yet. According to 

information from Khan Younis Municipality (letter dated on 20th April 2009), its 

design and tender documents and budget are ready and waiting for materials 

availability in local market to advertise the tender. However, a particular study has 

been conducted by the consultant during initial design phase in order to check 

capacity of PS 8 and adequacy of the PS 8 and the pressure line to the WWTP with 

updated KY WWTP project data. Based on this study, it has been decided by the 

Client and Counterparts to retain modification option n°3: 

 

 

Extend the existing 24'' diameter pipe (2000m long) with a 28'' 

diameter pipe (2750m long) to the WWTP in phase I. 

In phase II, a 20'' diameter (2000m long) pipe is to be installed in 

parallel to the existing 24'' pipe. 

- The second pressure pipe will supply KY WWTP with effluents from Eastern 

villages’ wastewater collection system. A new pumping station at Khuza’a and 

pressure line to KY WWTP need to be implemented. 

Comment : Upstream pumping stations and pressure pipes to KY WWTP are out of KY 

WWTP project scope and are not included in the present detailed design report. 





Inlet flows and loads were detailed in the Initial Design Report and approved by the Client 

and counterparts, however it had been decided to verify wastewater concentration 

estimations for current situation on the basis of wastewater analysis results conducted in 

2009 (see addendum at edition of final version of Initial Design Report). In addition, 

septage flow rates as estimated in the Initial Design Report needed to be verified. Thus, 

inlet flows and loads given hereafter and used for Detailed Design are slightly different 

from previous estimations given in the Initial Design Report. Differences concern the 

following points (see detail given in appendix 1 of the present report): 

- Septage flow rates: 2,24 m 3 /capita/year (according to information from Khan Younis 

Municipality). 

- Septage flows: For phase 2, it is considered that septage from all unconnected 

population in Khan Younis Governorate (Khan Younis City and Eastern villages) will be 

collected by vacuum trucks and discharged to the sewer system. For phase 1, only 

septage from Khan Younis City, Bani Suheila and Al Fukhari is considered, since no 

sewage network is existing at present time in the other parts of Eastern villages, which 

discharge their septage to agricultural lands. 

- Septage concentrations: revised for all parameters according to septage analysis 

results conducted in 2009. 

- Domestic wastewater loads: revised for parameter Phosphorus according to 

wastewater analysis results conducted in 2009. 

1.2.1.1. INLET FLOWS 

Total KY WWTP incoming flows considered in Detailed Design are the following: 

Parameter Unit Phase 1 

2018 

Phase 2 

2025 

Average daily flow m 3 /d 26 656 44 948 

Average hourly flow m 3 /h 1 111 1 873 

Peak coefficient 1.9 1.9 

Peak hourly flow m 3 /h 2 110 3 558 





1.2.1.2. INLET LOADS 

Total KY WWTP incoming loads considered in Detailed Design are the following: 


2018 

Phase 2 

2025 

BOD 5 kg/d 14 247 22 399 

Total SS kg/d 19 056 30 486 

Total Nitrogen kg/d 3 358 5 604 

Total Phosphorus kg/d 358 605 

1.2.2. TREATED EFFLUENT QUALITY REQUIREMENTS 

Based on initial design report and according to Clients’ and counterparts’ decision, the 

treated effluent requirements are based on required effluent quality for infiltration and 

irrigation. Treated effluent disposal to the sea is limited to emergency situations only. 

Consequently, Detailed Design is based on the following quality requirements for treated 

effluent : 

Parameter Unit Required effluent quality for KY WWTP 

BOD5 mg/l




1.3. PROJECT COMPONENTS 

The present detailed design for KY WWTP project contains the following components: 

1. KY WWTP plant itself; 

2. The treated effluent infiltration basin, and 

3. The treated effluent pressure line from the WWTP site to the infiltration basin and 

emergency discharge to the sea. 

Detailed design is prepared for phase 1 and phase 2 of KY WWTP, however only phase 1 

works will be concerned by tender documents to be prepared by the consultant (Task 6). 

In order to achieve wastewater treatment objectives, the following steps are necessary for 

KY WWTP: 

Pre-treatment including screening and degeasing/degritting 

Secondary treatment including nitrogen removal 

Tertiary treatment. 

According to Initial design and Clients’ and counterparts’ decisions, the secondary 

treatment by activated sludge process technology is chosen. Sand filtration followed by UV 

disinfection is proposed for tertiary treatment. 

The WWTP includes the following treatment steps: 

- Effluent treatment: 

Pre-treatment including fine screening as well as grit and grease 

removal, 

Aeration tanks and clarification tanks, 

Tertiary treatment including sand filtration and UV disinfection, 

Treated effluent outlet pumping station. 

- Sludge treatment: 

Gravity thickening, 

Sludge drying on open drying beds, 

Sludge composting. 

The WWTP includes also: 

- Buildings: 

Pretreatment building, 

Blower building for biological treatment, 

Tertiary treatment building, 

Administration building, including laboratory, control room, etc, 

Work shop, 

Electrical substations and generators. 

- Piping and connection systems, 

- Internal roads and site access, 

- Architectural and landscaping integration of works. 

General lay-out of the different project components is illustrated in figure 1 below: 





Fig. 1. GENERAL PROJECT LAYOUT 





2. 

WWTP PROCESS JUSTIFICATION 

2.1. RAW EFFLUENT FLOW MEASUREMENT AND INLET STRUCTURE 

The two arriving raw effluent pressure lines feed one common inlet channel and 

downstream treatment structures are common for all effluents. 

Raw effluent flow will be metered at the WWTP inlet at each of both arriving wastewater 

pressure lines. The flow metering equipments are implemented on the inlet trunk lines 

inside the pre-treatment building, directly upstream of the inlet structure, on the vertical part 

of the pipes. 

Flow metering devices are designed for phase 2 peak flow: 

- 2 610 m 3 /h coming from KY city via PS8, 

- 950 m 3 /h coming from Eastern villages via Eastern villages PS. 

Flow metering devices consist in: 

- Electromagnetic flow meter, 

- Flow converter, 

- Instant flow display and, 

- Totalizer with connection to the central control unit. 

2.2. PRETREATMENT OF EFFLUENTS 

2.2.1. FINE SCREENING 

Incoming wastewater has already undergone coarse screening at the upstream pumping 

stations. 

According to information approved in the Initial Design Report, coarse screens 40 mm are 

already installed in the PS8 and the PS to be implemented for transfer of Eastern Areas 

wastewater should also include coarse screens in order to protect the transfer pumps. 

Thus, KY WWTP is equipped with fine screens. 

Characteristics of screen channels and screens are determined on the following basis: 

v = Q / [ S x n x 36 x (d/(d+e)) x (100-C)], 





With: 

v: flow velocity (in m/s) 

Q: Peak effluent flow phase 2 (in m 3 /s) 

S: Wet surface of one screen (in m2) 

n: Number of parallel treatment lines 

C: tolerated clogging rate 

d: free space between screen bars (mesh spacing) 

e: screen bar width 

- Screen channels have the followings caracteristics: 

Total number of parallel screens in Phase 1: ...........................2 

Total number of parallel screens in Phase 2: ...........................3 

Mesh spacing......................................................................8 mm 

Screen bar width ..............................................................10 mm 

Channel height: ..................................................................1.3 m 

Channel width:.......................................................................1 m 

- Flow velocity at peak flow with all treatment lines and with clogging rate of 25%: 

Phase 1: 0.67 m/s 

Phase 2: 0.76 m/s 

- Flow velocity at peak flow with one treatment line in stand-by and with clogging rate 

of 25%: 

Phase 1: 1.35 m/s 

Phase 2: 1.14 m/s 

The parallel screening channels can be individually isolated by stop logs. Total flow may 

be hydraulically treated with one screening line in stand by. 

Screens will be automatically cleaned, with operation based on time setting and head loss. 

Screenings are conveyed by a shaft less spiral conveyor towards a screenings compacting 

device and then deposited into a 15 m 3 skip. 

Screenings quantity specific..................................... 4 l/PE/ year 

Screenings quantity Phase 1 (before compacting)........2.4 m 3 /d 

Screenings quantity Phase 2 (before compacting)........4.1 m 3 /d 





Compacting rate ...................................................................35% 

Screenings quantity Phase 1 (after compacting) .........1.56 m 3 /d 

Screenings quantity Phase 2 (after compacting) .........2.67 m 3 /d 

Screenings’ skip capacity..................................................15 m3 

Autonomy before skip exchange Phase 1 ..........................9.6 d 

Autonomy before skip exchange Phase 2 ..........................5.6 d 

Dripping waters and reject water from screenings’ compacting are collected and sent to the 

reject water pumping station situated in the pre-treatment building. 

Parallel to the fine screening channels, a by-pass channel is implemented. The by pass 

channel is fed by a crest-weir, situated directly downstream of the inlet structure. Crest 

characteristics are calculated using the following equation: 

With: 

Q = m x S x (2g x H) 1/2 Q = 1.77 x B x H 3/2 

Q: Peak effluent flow phase 2 (in m 3 /s) 

S: Overflow section (in m 2 ): S = H x L 

H: Overflow height (in m) 

L: Crest length (in m) 

For peak flow of 1 m 3 /s and overflow height of 0.3 m, the crest length is 3.4 m. 

2.2.2. DEGREASING AND DEGRITTING 

The grit and grease removal is carried out in a combined longitudinal tank with two parallel 

lines in the first phase and three parallel lines in the second phase. 

Degreasing and degritting tanks are dimensioned on the following basis: 

With: 

v a = Q / S t and t p = V / Q, 

v a : 

overflow rate (in m/h) 

S t : Total tank surface (in m 2 ) 

t p : retention time in the tank (in minutes) 

V: Total tank volume (in m 3 ) 

Q: Peak flow to be treated (in m 3 /h) 





Peak flow to be treated in degritting/degreasing tanks takes into account raw effluent and 

reject/backflow waters: 

Incoming raw effluent: 

Phase 1 Phase 2 

Average incoming flow 

Peak incoming flow 

Backflow and reject water: 

Average flow 

Peak flow 

Flow to be treated in 

degritting tanks: 

Average flow 

Peak flow 

1 111m 3 /h 

2 110m 3 /h 

111 m 3 /h 

211 m 3 /h 

1 224 m 3 /h 

2 321 m 3 /h 

1 873m 3 /h 

3 558 m 3 /h 

187 m 3 /h 

356 m 3 /h 

2 060 m 3 /h 

3 914 m 3 /h 

The characteristics of the grit and grease removal tank are as follows: 

- Type ...................................................................... aerated grit chamber 

- Shape .................................................rectangular tank with flat bottom 

- Number of parallel lines 

Phase 1......................................................................................2 

Phase 2......................................................................................3 

- Unit length...................................................................................16.25 m 

- Unit width ...........................................................................................4 m 

- Unit surface.................................................................................... 65 m 2 

- Unit volume ............................................................................... 214.5 m 3 

The normal operating conditions with all treatment lines in operation are thus the following: 

- Overflow rate: 

Phase 1 – at average flow...............................................9.4 m/h 

Phase 1 – at peak flow ..................................................17.9 m/h 

Phase 2 – at average flow.............................................10.6 m/h 

Phase 2 – at peak flow ..................................................20.0 m/h 

- Retention time: 

Phase 1 – at average flow.............................................21.0 min 

Phase 1 – at peak flow ..................................................11.1 min 

Phase 2 – at average flow.............................................18.7 min 





Phase 2 – at peak flow ....................................................9.9 min 

In downgraded operation, i.g. with one treatment line in stand-by, the operating conditions 

become the following ones: 

- Overflow rate at average flow: 

Phase 1..........................................................................18.8 m/h 

Phase 2..........................................................................15.9 m/h 


Phase 1..........................................................................10.5 min 

Phase 2..........................................................................12.5 min 

It is thus possible to operate with one treatment line in stand-by, which permits to do 

maintenance works on this line. 

The capacity of the aeration device is calculated to ensure that grease, oil and scum float 

at the surface, to facilitate the separation of grit from organic matter and to maintain the 

organic matter in suspension. Air is introduced by immersed turbines: 

- Required specific aeration capacity: ..................................................................20 W/ m 3 

- Required aeration capacity per treatment line:...................................................4.3 kW 

- Height of turbine immersion: ..............................................................................3 m 

Each line is provided with a travelling bridge which scrapes the grease accumulated at the 

surface towards a hopper at the bottom end of the tank, and scrapes the grit at the bottom 

of the tank to the grit collection chambers which are situated at the front end of each line. 

From there, the collected grit is extracted by pumping towards a grit classifier. It is then 

conveyed to a 15 m 3 skip for evacuation to land fill. 

The grease is evacuated to a grease pit, where surplus water is removed and conveyed to 

the reject water pumping station situated in the pre-treatment building. Grease is then 

transported to land fill by vacuum tank. 

Taking into account particular local conditions and local habits, estimated specific grit and 

grease quantities are relatively high: 

- Specific grit quantity removed from tanks . 100kg/1000 m3 raw effluent 

- Recovered grit quantities 

Phase 1.......................................................................2 670 kg/d 

Phase 2.......................................................................4 500 kg/d 

- Concentration of recovered gritty water..........................................30 g/l 

- Recovered quantity of gritty water (to classifier) 

Phase 1........................................................................... 89 m 3 /d 

Phase 2......................................................................... 150 m 3 /d 





- Concentration at classifier outlet ......................................................35% 

- Grit quantity from classifier to grit skip 

Phase 1......................................................................... 7.6 m 3 /d 

Phase 2........................................................................ 12.9 m 3 /d 

- 

Grit skip capacity............................................................................ 15 m 3 

- Autonomy before skip exchange 

Phase 1...................................................................................2 d 

Phase 2................................................................................1.2 d 

- Backflow from classifier to pre-treatment: 

Phase 1...........................................................................82 m3/d 

Phase 2.........................................................................137 m3/d 

- Specific grease quantity removed from tanks .....................30 l/PE/year 

- Greasy water quantity conveyed to grease pit 

Phase 1........................................................................17.8 m3/d 

Phase 2...........................................................................30 m3/d 

- Concentration rate in grease pit ......................................................75 % 

- Grease quantities to be evacuated by vacuum tanks: 

Phase 1.................................................................... 31 m3/week 

Phase 2.................................................................... 52 m3/week 

- Corresponding backflow from grease pit to pre-treatment: 

Phase 1........................................................................ 13.4 m 3 /d 

Phase 2........................................................................ 22.5 m 3 /d 

At the tank inlet, three isolation valves allow the isolation of each treatment line. 

At the tank outlet, an adjustable spillway allows the wedging and equal distribution of flows 

to the treatment lines. 

Complete drainage of the tank to the reject water pumping station is possible via a 

withdrawal pipe in each line, equipped with an isolation valve and a quick union ND 100. 





2.3. SECONDARY EFFLUENT TREATMENT 

2.3.1. TREATMENT PRINCIPLES AND DESIGN LOADS AND FLOWS 

Secondary effluent treatment comprises the following parts: 

- Aeration tank with: 

contact zone, 

anoxic zone, 

aeration channel, 

mixed liquor recirculation system 

- Degassing and distribution well 

- Clarifier 

- Sludge recirculation system 

- Excess sludge extraction system. 

The plant is designed with parallel treatment lines of equivalent capacity: 2 lines in phase 

1, 3 lines in phase 2. 

Pre-treated effluents are admitted upstream of aeration tanks in a distribution well (DW1), 

dividing the arriving effluent flow into equal parts prior to biological treatment. 

Effluents to be treated in secondary treatment comprise plant inlet effluents as well as 

internal backflow and reject water. 

Main sources of backflow and reject water flows are summarized below: 

Backflow from pre-treatment 

backflow PS 

Backflow from backflow PS in 

thickener area 

Backwash water from sand 

filters (Dirty water PS) 

Phase 1 

(m 3 /d) 

Phase 2 

(m 3 /d) 

530 900 

1 400 2 000 

135 135 

Miscellaneous (cleaning, etc.) 20 30 

TOTAL 2 085 3 065 

In order to take into account occasional backflows, we take into account the following 

backflows: 

- Phase 1: 2 670 m 3 /d 

- Phase 2: 4 500 m 3 /d, 





Which correspond to 10% of average incoming flows at the WWTP inlet. 

Corresponding backflow loads are calculated based on the following assumptions: 

BOD 5 :................................................................6% of inlet loads 

Total SS: .........................................................10% of inlet loads 

Total Nitrogen: ..................................................2% of inlet loads 

Total Phosphorus: ........................................... 7% of inlet loads 

Design flows and loads for secondary treatment are summarized below: 


2018 

Phase 2 

2025 

Average daily flow m 3 /d 29 370 49 500 

Average hourly flow m 3 /h 1 224 2 063 


Peak hourly flow m 3 /h 2 325 3 919 

BOD 5 kg/d 15 102 23 743 

Total SS kg/d 20 962 33 535 

Total Nitrogen kg/d 3 425 5 716 

Total Phosphorus kg/d 383 647 

2.3.2. AERATION TANKS 

The aeration tanks are of channel-flow type and are composed of an anoxic zone and an 

aerated zone. 

2.3.2.1. ELIMINATION OF CARBONATED POLLUTION 

Reduction of carbonated pollution is performed by heterotrophic bacteria during aeration 

periods. 

The BOD5 load balance is summarized below: 

BOD 5 e = BOD 5 i – BOD 5 r 

With: 

- BOD 5 e: BOD5 load to be removed (in kg/d) 

- BOD 5 i: BOD5 load at aeration tank inlet (in kg/d) 

- BOD 5 r: BOD5 load admitted at plant outlet (in kg/d) 






BOD 5 load at aeration tank inlet 15 102 kg/d 23 743 kg/d 

BOD 5 load admitted at plant 

outlet 

587 kg/d 990 kg/d 

BOD 5 load to be removed 14 515 kg/d 22 753 kg/d 

The total required aeration tank volume is calculated on the following basis: 

- Sludge concentration in tanks = 4.5 kg MLSS/m 3 

- Ratio MVSS/MLSS = 0.67 

- Sludge concentration in tanks = 3.02 kg MVSS/m 3 

- Minimum sludge age = 12 days 

- Sludge production ratio = 0.8 kg DS / kg BOD 5 removed 

- Minimum effluent temperature = 15 °C. 

Corresponding total aeration tank volumes are: 

- Phase 1: 32 000 m 3 

- Phase 2: 48 000 m 3 

2.3.2.2. ELIMINATION OF NITROGEN 

Nitrogen elimination is achieved in 2 stages in the aeration tanks: 

- A nitrification stage, which aims at transformation of ammonia nitrogen into 

nitrates by autotrophic bacteria. This stage requires: 

Presence of sufficient oxygen. 

Low load conditions, since growth of nitrifying bacteria is slow 

Favourable temperature conditions, since the growth rate of nitrifying 

bacteria is rapidly declining for temperatures below 12°C. 

- A denitrification stage, which aims at reducing the nitrate ions to nitrogen gas. This 

stage requires: 

Availability of sufficient carbon source, which can be easily assimilated by 

bacteria 

Absence of oxygen. 

The nitrification is achieved in the aerated zone. Partial denitrification is also performed 

inthis zone, using sequential aeration (i.g. aeration devices are shut-off periodically). 

However, in case of KY WWTP, denitrification needs to be completed in an anoxic zone in 

order to achieve the required Nitrate Nitrogen effluent discharge quality. Thus, an anoxic 

zone is implemented in front of the aerated zone and mixed liquor with high Nitrate 

concentration is recirculated from the aerated zone to the anoxic zone. 





The nitrogen balance is summarized below: 

Item Unit Phase 1 Phase 2 

N1: Total Kjeldhal Nitrogen at 

tank inlet 

N2: Total Kjeldhal Nitrogen 

assimilated in biological sludge 

N3: Total Kjeldhal Nitrogen not 

nitrifyable 

kg/d 3 425 5 716 

kg/d 906 1 425 

kg/d 102.8 171.5 

N4: Residual ammonia nitrogen kg/d 167.4 282.2 

N5: Total Kjeldhal Nitrogen to 

be nitrified 

kg/d 2248.8 3837.3 

N5 = N1-N2-N3-N4 

N6: Total Kjeldhal Nitrogen 

contained in SS of outlet 

effluents 

N7: Total Kjeldhal Nitrogen in 

treated effluent 

kg/d 24.2 40.8 

kg/d 294.4 494.5 

N7 = N3 + N4 + N6 

N8: Nitrate Nitrogen allowed in 

treated effluent (Discharge 

standard: 25 mg/l) 

N9: Nitrate Nitrogen to be 

denitrified 

kg N-NO 3/d 440.6 742.5 

kg N-NO 3/d 1808 3094 

N9 = N5-N8 

Denitrification: 

(1) Total volume anoxic zone m 3 4 000 6 000 

(2) Denitrification rate in anoxic 

tank 

(3) Sludge concentration in 

tanks 

(4) Denitrification potential in 

anoxic zone: (4) = 

(1)x[(2)x24/1000]x(3) 

(5) Remaining Nitrate to be 

eliminated in aerated zone: (5) 

= N8 – (4) 

(6) Denitrification rate in 

aeration tank 

g NO 3/kg MVSS/h 3.29 3.29 

kg MVSS / m 3 3.02 3.02 

kg N-NO 3/d 952 1 428 

kg N-NO 3/d 856 1 667 

g NO 3/kg MVSS/h 1.82 1.82 

(7) Total volume aerated zone m 3 28 000 42 000 

(8) Number of denitrification 

periods (stop of aeration 

device) 

(9) Total required minimum 

duration of aeration stop for 

denitrification: 

Number /d 4 4 

h/d 7.4 6.8 





Nitrification: 

(10) Maximum remaining 

aeration duration: (10) = 24 – 

(9) 

(10’) Retained duration of 

aeration period 

(11) Nitrification rate in aerated 

zone 

(12) Required sludge quantity 

for nitrification: (12)= 

N5/(10’)/(11)x1000 

h/d 16.6 17.2 

h/d 15 15 

g N/kg MVSS/h 3 3 

Kg MV 49 975 85 286 

(13) Sludge quantity present in 

aerated zone : (13)=(7)x(3) 

Kg MV 84 560 

Sufficient 

126 840 

Sufficient 

Nitrate recirculation from aerated zone to anoxic zone (Mixed liquor recirculation) 

Nitrate recirculation flow kg N-NO3/d 30 443 39 508 

Mixed liquor recirculation rate 

(recirculation flow / average 

incoming effluent flow) 

% 104 80 

2.3.2.3. SUMMARY OF AERATION TANK CHARACTERISTICS 

Aeration tanks for KY WWTP have the following characteristics: 

- Total tank volumes phase 1: 

Total aeration tank volume......................................... 32 000 m 3 

Total volume aerated zone......................................... 28 000 m 3 

Total volume anoxic zone ............................................ 4 000 m 3 

- Total tank volumes phase 2: 

Total aeration tank volume ......................................... 48 000 m 3 

Total volume aerated zone......................................... 42 000 m 3 

Total volume anoxic zone ............................................ 6 000 m 3 

- Number of units – Phase 1 ....................................................................2 

- Number of units – Phase 2 ....................................................................3 

- Unit tank volumes: 

Unit volume per aeration tank .................................... 16 000 m 3 

Unit volume aerated zone .......................................... 14 000 m 3 

Unit volume anoxic zone ............................................. 2 000 m 3 

Water depth in aeration tanks ...............................................8 m 

2.3.2.4. SUMMARY OF AERATION TANK OPERATING CONDITIONS 

Aeration tanks have the following operation parameters: 

- Sludge concentration in tanks: .....................................4.5 kg MLSS/ m 3 

- Sludge concentration in tanks: .................................. 3.02 kg MVSS/ m 3 





- BOD removal efficiency ....................................................................96% 

- Sludge loading ratio F/M: 

Phase 1:.........................................0.16 kg BOD5/kg MVSS/day 

Phase 2:.........................................0.16 kg BOD5/kg MVSS/day 

- Sludge age: 

Phase 1: ...................................................................... 12.4 days 

Phase 2: ...................................................................... 11.9 days 

- Volumetric load (BOD loading): 

Phase 1: ................................. 0.47 kg BOD5 removed / m 3 /day 

Phase 2: ................................ 0.49 kg BOD5 removed / m 3 /day 

2.3.2.5. MIXING DEVICES 

In each treatment zone, submersible stirrers are implemented. 

Mixing of pre-treated effluents with recirculation sludge and recycled mixed liquor is 

realised in the anoxic zone, which constitutes also a contact zone: 

- Specific stirring power: 6 W/ m 3 

- Required stirring power per treatment line: 6 kW 

In the aerated zone, banana plate type stirrers assure the blending of mixed liquor and the 

flow circulation in the channel: 

- Specific stirring power: 4 W/ m 3 

- Average circulation speed: 0.35 m/s 

- Required stirring power per treatment line: 39 kW 

2.3.2.6. MIXED LIQUOR RECIRCULATION 

Capacity of mixed liquor recirculation pumps is dimensioned for a recirculation rate of 

104% (Phase 1) and 80% (Phase 2) of incoming effluent average flow. 

Required total pump capacity is thus: 

- Phase 1: 1 280 m 3 /h 

- Phase 2: 1 650 m 3 /h 

Each aeration tank is equipped with 2 pumps of unit capacity 320 m3/h.Total provided 

mixed liquor recirculation capacity is thus: 

- Phase 1: 1 280 m 3 /h 

- Phase 2: 1 920 m 3 /h 





2.3.3. AIR PRODUCTION 

2.3.3.1. OXYGEN DEMAND 

Process air with required oxygen for biological treatment is furnished by compressors and 

introduced to the tanks via fine bubble diffusers. Design parameters are the following: 

Unit Phase 1 Phase 2 

BOD 5 load to be removed kg/d 14 515 22 753 

Nitrogen to be nitrified kg/d 2249 3838 

Nitrogen to be denitrified kg/d 1808 3094 

Sludge quantity present in 

aerated zone 

Retained aeration time 

(including security factor) 

Kg 

MVSS 

84 420 126 630 

h/d 14 14 

The table below summarizes corresponding oxygen requirements for biological treatment: 

Oxygen requirements 

Applied 

coefficient 


Oxygen requirements for 

BOD removal 


endogen respiration 

(sludge present in aerated 

zones) 


nitrification 

Oxygen liberation by 

denitrification 

Total daily oxygen 

requirements 

0.65 9 434 kg O 2/day 14 789 kg O 2/day 

0.07 5 909kg O 2/day 8 864 kg O 2/day 

4.18 9 400kg O 2/day 16 042 kg O 2/day 

2.8 - 5 063 kg O 2/day - 8 667 kg O 2/day 

19 681 kg O 2/day 31 029kg O 2/day 

Aeration time 14 h/day 14 h/day 


Theoretical peak hourly 

oxygen requirement 

2 109 kg O 2/h 3 325kg O 2/h 

Real oxygen requirement is calculated taking into account a correcting coefficient T which 

is determined as follows: 

- Coefficient T p (exchange clean water – activated sludge) : 0.7 

- Coefficient T d (oxygen deficit): 0.768 

- Coefficient T t (transfert velocity): 1.04 

Correcting coefficient T = T p X T d X T t = 0.56 





Real peak hourly oxygen demand is thus: 

- Phase 1: 3 766 kg O 2 /h 

- Phase 2: 5 938 kg O 2 /h 

2.3.3.2. NOMINAL AIR FLOW AND DIFFUSER NUMBER 

The required oxygen is introduced in the aeration tanks as fine bubbles of compressed air. 

The aeration system will consist of adjustable air diffusers mounted on headers. Air 

diffusers consist of tubes covered by a perforated rubber membrane that resists micro 

organisms and various compounds contained in the wastewater. 

The air flow required to furnish the real peak hourly oxygen demand determines the 

number of air diffusers which is required: 

- Water height above diffusers: 7.75 m 

- Nominal air flow per linear meter of diffuser length: 9 m3/h 

- Nominal oxygen flow of diffusers (immersed at 7.75m): 110 gO2/Nm3 

- Air flow: 

Phase 1: Q = 3766/0.11 = 34 236 Nm 3 /h (= 17 118 Nm 3 /h per aeration 

tank) 

Phase 2: Q = 5938/0.11 = 53 982 Nm 3 /h (=17 994 Nm 3 /h per aeration 

tank). 

We retain a nominal air flow of 18 000 Nm3/h per aeration tank, which means a total air 

flow of: 

Phase 1: 36 000 Nm 3 /h 

Phase 2: 54 000 Nm 3 /h 

The corresponding numbers of required diffusers are: 

Phase1: N= 36 000 / 9 = 4 000 

Phase 2: 54 000 / 9 = 6 000 

2.3.3.3. COMPRESSORS 

Total air flow per aeration tank is 18 000 Nm3/h. Each tank is supplied with process air by 

1 compressor. Pressurized air is supplied to the tank by a pressure pipe system, consisting 

of: 

- a trunk line from the compressor to the front end of the tank (ND 600) 

- two branches going along the tanks from the front end of the tank to the diffuser 

racks’ feeders (ND 400) 

- feeders from the top of the tank to the diffuser racks (ND 160). 





Discharge pressure at compressor outlet is calculated based on following parameters: 

Air flow (Nm3/h) Speed (m/s) Headloss (mbar) 

Feeders ND 160 1 125 15.5 Singular: 18 

Linear: 1.3 

Branch pipes ND 400 9 000 19.9 Singular: 1.6 

Linear: 4.1 

Trunk line ND 600 18 000 17.7 Singular: 11.4 

Linear: 0.6 

Diffusers at 7.75 m 

immersion height 

775 

TOTAL 868 

We retain a compressor discharge pressure of 880 mbar. 

2.3.4. DEGASSING AND DISTRIBUTION 

Prior to clarification, and to assure correct operating conditions in the clarification stage, a 

degassing structure is provided. Its function is to allow the bubbles of gas trapped in the 

turbulent mixed liquor to escape in the open air and thus sludge sedimentation in the 

clarifier is not disturbed. Each degassing structure is fitted with a surface scraper and 

floating matter is conveyed to a common floating matter pit from where it is conveyed by 

submersible pumps to the grease pit of pre-treatment. Degassing structures are located 

between each pair of secondary clarifiers. 

Degassing structures are dimensioned on following parameters: 

- Upflow velocity (v): 80 m/h 

- Sludge recirculation rate (τ): 113% 

- Peak effluent flow at aeration tank inlet (Q p ), including backflow: 

Phase 1: 2 325 m 3 /h 

Phase 2: 3 919 m 3 /h 

Required minimum degassing tank surface (S) is therefore: 

S = Qp x (1+ τ) / v 

Phase 1: S = 61.9 m 2 

Phase 2: S = 104 m 2 

Provided unit degassing tank surface is 35 m 2 , thus total available degassing surface is 70 

m 2 in phase 1 (on 2 degassing tanks), and 105 m 2 in phase 2 (on 3 degassing tanks). 





2.3.5. CLARIFIERS 

Incoming flows to clarifiers are the following: 


Average flow ( m 3 /h) 1 224 2 063 

Peak flow (m 3 /h) 2 325 3 919 

Clarifiers are designed for a maximum overflow rate of 0.8 m/h at peak flow in normal 

operating conditions and according to following equation: 

With 

S = Q p / v, 

- S = Total clarifier surface in m 2 

- Q p = Total peak flow to clarifiers 

- v = overflow rate in m 3 /m 2 /h 

Clarifiers have thus the following characteristics: 

- Number of units : 

Phase 1......................................................................................4 

Phase 2......................................................................................6 

- Peripheral water depth....................................................................3.5 m 

- Clarifier Inner Diameter ...................................................................33 m 

- Unit surface per clarifier............................................................... 855 m 2 

- Total provided clarification surface 

Phase 1......................................................................... 3 421 m² 

Phase 2......................................................................... 5 132 m² 

Normal operating conditions of clarifiers are the following: 

- Overflow rate at peak flow 

Phase 1...................................................................0.68 m 3 /m 2 /h 

Phase 2...................................................................0.76 m 3 /m 2 /h 

- Overflow rate at average flow 

Phase 1...................................................................0.36 m 3 /m 2 /h 

Phase 2...................................................................0.40 m 3 /m 2 /h 





In case of downgraded operation (with one clarifier out of operation), the overflow rate at 

peak flow becomes 0.9 m 3 /m 2 /h, which is acceptable. 

2.4. TERTIARY TREATMENT 

The requirements for treated water quality are below the concentrations achievable with 

secondary treatment. Tertiary treatment is therefore required, including the following 

process units: 

- rapid sand filtration 

- UV disinfection 

2.4.1. INTERMEDIATE PUMPING STATION 

An intermediate pumping station is needed to feed secondary clarified effluent to the top of 

the sand filters and allow gravity flow through the whole tertiary treatment from sand filters 

downstream UV disinfection. 

The characteristics of the intermediate pumping station are defined, as follows: 

Parameters Unit Phase1 Phase 2 

Total peak flow m3/h 2231 3919 

Number of pumps unit 2 + 1 stand-by 3 + 1 stand-by 

Unit flow m3/h 1306 1306 

TDH m 8.10 8.10 

2.4.2. SAND FILTERS 

2.4.2.1. DIMENSIONAL DESIGN OF SAND FILTERS 

The effluent is treated on a bed of homogeneous sand with an actual particle size between 

1 and 2 mm, at a rate of 10 m/h and more. Flushing is carried out by air scour with filtered 

water backwash. 

The high water head of 1.20 m above the filtration sand guarantees even distribution of the 

water to be filtered and hence a constant filtration rate across the entire filtration surface. 

This high head also prevents degasification. 





The characteristics of the sand filters are indicated hereafter: 


Peak total flow m3/h 2231 3919 

Average flow m3/h 1174 2063 

Number of filters unit 4 6 

Peak unit flow m3/h 558 653 

Average unit flow m3/h 294 344 

Length m 13.00 13.00 

Width m 4.66 4.66 

Unit surface area m² 60.58 60.58 

Filter slab 

dimensions 

m 0.49 x 1.15 0.49 x 1.15 

Nozzles U/m² 50 50 

Peak filtration rate m/h 9.20 10.78 

Filtration rate with 

average flow 

m/h 4.85 5.68 

The settled water reaches the filter via a weir. A manual valve can be used to isolate the 

filter for repairs. During washing, water continues to feed the filters, with a cross-washing 

action. 

The filtered water flows out via a motorised butterfly valve. This valve plays a dual role: 

isolating the filter during the washing period, and creating a variable head loss in order to 

maintain a constant level in the filters. 

The characteristics of the valves, penstocks at the inlet and outlet of each filters are as 

follows: 


Inflow m3/h 558 653 

Speed m/s 1 1.13 

Penstock 

dimensions (inlet 

settled water) 

Motorized valve 

(outlet filtered 

water) 

mm 400 x 400 400 x 400 

Ø mm 450 450 





The characteristics of the valves and sleeves on the fitter backwash network (air and wash 

water) are as follows: 


Scour air inlet : valves 

Scour air inlet 

inflow 

Nm3/h 3030 3030 

Speed m/s 25 25 

Dimensions of the 

motorized valves 

Ø mm 200 200 

Scour air : sleeves 

Scour air inlet 

inflow 

Nm3/h 3030 3030 

Speed m/s 20 20 


sleeves 

Ø mm 250 250 

Wash water inlet : valves 

Wash water inlet 

inflow 

m3/h 910 910 

Speed m/s 2.5 2.5 


motorized valves 

Ø mm 350 350 

Wash water inlet : sleeves 

Wash water inlet 

inflow 

m3/h 910 910 

Speed m/s 2 2 


sleeves 

Ø mm 450 450 

2.4.2.2. FILTER PACKING 

The filters are designed with a high water head to prevent degasification and guarantee 

even distribution of the water to be filtered. 

The filters are packed with sand with a particle size of 1.35 mm, which is compatible with 

wastewater filtration. Given the particle size and the filtration rate adopted, the filter 

medium height will be 1.40 m in order to prevent filter breakthrough and hence guarantee 

filtered effluent quality. 

The sand is to be placed on top of a 4 / 8 mm gravel layer. This gravel does not have any 

effect on the filtration process; its purpose is to distribute scour air and wash water across 

the entire surface of the filters and hence prevent stack effect. 

So, the filling heights are the followings: 

- Gravel, particle size 4 to 8 mm : 0.10 m 

- Sand, particle size 1.35 mm : 1.40 m 





2.4.2.3. FILTRATION CYCLES 

In 1.4 m of filtering material there are about 450 litres of voids irrespective of the particle 

size, and the volume that can be used by the particles to be retained is 110 litres, provided 

that the actual size of the filtering material is suited to the nature of these particles. 

When the SS to be retained are colloidal floc-based, their dry matter content does not 

exceed 10 g/l and the quantity that can be eliminated by 1 m3 of filtering material is 1100g. 

This figure increases when the floc is charged with dense mineral matter. With sludge 

containing 60 g of matter per litre it can reach 6600g. 

In the case of biological sludge we will adopt a value of 30 g/l. The quantity that can be 

eliminated for 1 m3 of filtering material is 3300g. 

The filtration cycle will be stopped before the filtration front reaches the gravel layer. We 

will keep a safety margin of 30 cm in Phase 1 and 20 cm in phase 2. The useful height of 

the filter medium is therefore 1.10m and 1.20m respectively for each phase. the quantity of 

SS retained in the filters is 14 g/m3 of filtered effluent. 


Useful filter medium 

volume 

Quantity of matter 

retained in the filter 

medium 

Quantity of effluent 

can be filtered before 

washing 

m 3 266 436 

kg 877 1439 

m 3 62 700 102 785 

Hourly flow rate m 3 /h 1174 2063 

Time for washing h 53 50 

As a precaution and in order to guarantee effective final UV disinfection treatment, all filters 

will be washed once every other day in phase 1 and 2. 

2.4.2.4. FILTER WASHING CYCLES 

The filter washing sequences are as follows whatever the Phase: 

- Decompacting with air only (50 m 3 /m²/h) .....................5 min. 

- Air scour + water washing sequence (8 m3/m2/h).......5 min. 

- Rinsing with water only (15 m 3 /m 2 /h)............................7 min. 

Throughout these phases, filter surface crosswashing with water continues. This process 

limits the backwash water quantities required and hence pump capacity. 

Pumped water volume during the air plus water sequence is of 40.50 m 3 and of 106 m 3 

during the water rinsing sequence. 





The quantity of the filtered water consumed to wash filter is as follows: 


Filtered water 

consumed to wash 

one filter 

Filtered water 

consumed to wash 

all filters 

m3 150 150 

m3 600 900 

As indicated above, the settled water inflow continues during filter washing. With a washing 

sequence lasting 17 min. plus idle times for manoeuvring valves, the total time taken to 

wash one filter is ≈20 min. 

The quantity of filtered water used for crosswashing all filters are as follows: 


Volume m3 1565 4126 

The following quantity of wash water will therefore be returned to the head of the station 

(pre-treatment): 


Volume m3 2165 5026 

With two filters being washed once per day in Phase 1 and three filters once per day in 

Phase 2, the following quantity will be returned to the head of station each day: 


Volume m3/d 1082 2513 

The backwash pollution will be: 


SS kg/2days 394 693 

DBO5 Kg/2days 225 396 

2.4.2.5. BACKWASH PUMPING STATION 

The backflow pumps are designed in order that during the air scour + water washing 

sequence the water flow rate will equivalent to 8 m3/m²/h and during the rinsing sequence 

the water flow rate will equivalent to 15 m3/m²/h. 






Water flow during 

the sequence air + 

water 

Water flow during 

the sequence 

rinsing water 

Number of backwash 

pumps 

Unit capacity of the 

pumps 

m3/h 484 484 

m3/h 910 910 

unit 2+1 standby 2+1 standby 

m3/h 455 455 

TDH m 7.6 7.6 

2.4.2.6. DIRTY WATER PUMPING STATION 

The dirty water issue of the filters washing and of the crosswashing will return to the head 

of the station in the pre-treatment building. The quantity of dirty water was calculated 

above. The dirty water pumps were designed to the phase 2. 


Volume m3/d 1082 2513 

Number of backwash 

pumps 

Unit capacity of the 

pumps 

unit 1+1 standby 1+1 standby 

m3/h 135 135 

TDH m 8.8 8.8 

2.4.2.7. AIR BLOWER FOR WASHING 

As indicated above, the maximum rate of scour air during the washing is 50 m3/m²/h, 

therefore the air flow required is 3030 Nm3/h. 

Two air blowers (1 + 1 standby) will be installed in the air blower building with a unit 

capacity of 3030 Nm3/h. 

2.4.2.8. FILTERED WATER QUALITY 

On good quality effluent from biological treatment, a SS reduction of about 70% and BOD5 

reduction of 40% are frequently obtained. 

Parameters Unit Phase 1 & Phase 2 

SS at secondary settling tank 

outlets 

mg/l 20 

Reduction by filtration % 70 

SS retained by filters mg/l 14 

SS content of filtered water mg/l 6 





2.4.3. UV DISINFECTION 

The wastewater treated in the previous process units can meet all standards except for 

pathogens. Very good removal of nematodes eggs is achieved by tertiary sand filtration. 

However, for other pathogens, an additional treatment step is required in order to achieve 

full compliance. 

In case of KY WWTP disinfection by UV radiation is proposed, which does not create any 

by-products. However, powerful UV lamps are required. 

UV treatment takes 6-10 seconds in a flow through channel, which makes maintenance 

very easy. Expected lamp life is about 10 000 to 12000 hours. Faecal coliform reduction is 

>99.99 %. UV rack and modules are installed directly into concrete channel. 

UV disinfection works for KY WWTP will have the following characteristics: 

- Number of UV modules – Phase 1...............................4 (2 in parallel + 2 in series) 

- Number of UV modules – Phase 2...............................6 (2 in parallel + 3 in series) 

- Total number of lamps – Phase 1 ................................144 

- Total number of lamps – Phase 2 ................................216 

- Minimum channel length...............................................8.5m 

- Number of channels......................................................1 + 1 by pass channel 

- Channel width ...............................................................1.5m 

- By pass channel width .................................................1.5m 

- Water depth in channel.................................................1.65m 

- Channel depth...............................................................2.0m 

2.4.4. TREATED EFFLUENT OUTLET PUMPING STATION 

The treated effluent pumping station is located at the east south corner of the sand filter 

building. The main function of this station is to pump the treated effluent to the infiltration 

basins at Al Fukhary area during the normal operation mode and to the sea during the 

emergency operation mode. The main challenge in designing this station was to overcome 

the differences in the piping system curves of the two operation modes (i.e. normal and 

emergency modes). To overcome this challenge, the diameter of the pressure line going to 

the sea was taken as 1030 mm (other sections of the pressure line are 920 mm) to 

decrease the head losses and to minimize the difference between the two operating 

systems (see chapter 3.10.1). This enabled the use of constant speed pumps that will 

experience almost similar pumping resistance when pumping to the infiltration basins and 

to the sea. 

The characteristics of the treated effluent pumping station are as follows: 





Parameters Unit Phase (1) Phase (2) 

Filtered water flow m 3 /hr 2110 3558 

Number of 

Treated effluent pumps 

Unit capacity of the pumps when 

pumping to the infiltration basins 

TDH when pumping to the 

infiltration basins 

Unit capacity of the pumps when 

pumping to the sea outfall 

TDH when pumping to the sea 

outfall 

Unit 2+1 standby 3+1 standby 

m 3 /hr 

1200 (For each unit 

when 2 pumps in 

operation) 

1200 (For each unit when 3 

pumps in operation) 

m 29 40 

m 3 /hr 

1200 (For each unit 

when 2 pumps in 

operation) 

1200 (For each unit when 3 

pumps in operation) 

m 31 42 

The pumps are identical variable speed pumps each equipped with variable frequency 

device (VFD) submersible non- clog type (see Appendix 7.4) 

The characteristics of the wet well of the effluent pump station are as follow: 

The characteristics of the wet well of the effluent pump station are as follow: 

- Dimensions: 7.9 m wide, 8.5 m long and 4.60 deep 

- Active depth: 0.75 for one pump, 0.9 for two pumps, 1.05 m for three pumps. 

- Active volume: 50 m3, 60 m3, and 70 m3 for one, two and three pumps, 

respectively. The active volume was designed based on an operating cycle time of 

6 minutes. 

- Minimum submergence depth for pumps to prevent vortexing is 2.7 m. 

All pumps in the system are speed regulated in parallel. The frequency range of the VFD 

device to be used should allow for the operating points in phase one and phase two as 

illustrated in the table above. The expected values of operation frequency vary from 30 to 

50 Hz. However, the exact frequencies are to be checked with the manufacturer. 

Water hammer analysis was performed to protect the effluent pumps and pipes. According 

to the analysis, a surge vessel ARAA type (Automatic air regulation) with a volume of 35 

m 3 . The water hammer analysis and the characteristics of the surge tank are given in 

Appendix 3.1. 

2.4.5. INDUSTRIAL WATER 

Industrial water is collected in the treated effluent pumping station after UV disinfection. 

The industrial water is designed to the phase 2. The industrial water needs on the waste 

water treatment plant are as follows: 





Cleaning buildings m 3 /h 37 

Pre-treatment area cleaning m 3 /h 8 

Clarification area cleaning m 3 /h 12 

Biological area cleaning m 3 /h 3 

Tertiary treatment area 

cleaning 

Unit 

Flow 

m 3 /h 5 

Sludge area cleaning m 3 /h 7 

Total m 3 /h 72 

The industrial water production will be equipped with 3 electropumps (2 +1 standby) with a 

total capacity of 72 m 3 /h and with a chamber of 500L. 

2.4.6. TREATED EFFLUENT METERING 

The treated effluent is metered at the WWTP outlet. The flow metering equipment is 

implemented on the outlet trunk line directly downstream the outlet pumps. Flow metering 

device is designed for effluent outlet peak flow in phase 2 (3 558 m 3 /h). It comprises: 

- Electromagnetic flow meter, 

- Flow converter, 

- Instant flow display and 

- Totalizer with connection to the central control unit. 

2.5. SLUDGE TREATMENT 

2.5.1. SLUDGE PIT 

Each pair of secondary clarifiers is fitted with one common sludge pit. Sludge pits contain 

sludge recirculation and excess sludge extraction pumps. 

2.5.1.1. SLUDGE RECIRCULATION 

The biological sludge is recycled from the sludge pits to the contact/anoxic zones of the 

aeration tanks. The required recycling rate is calculated on the basis of the mass balance: 

R = 100 x C a / (C d – C a ), with 

- Concentration of sludge extracted from clarifiers: C d = 8.5 g/l 

- Concentration of sludge in aeration tanks: C a = 4.5 g/l 

- R: sludge recycling rate in % of peak effluent inlet flow : 

R = 100 x 4.5 / (8.5 – 4.5) = 113% 





Total, required sludge recirculation flow capacity is thus the following: 

Phase 1: 2 384 m 3 /h 

Phase 2: 4 020 m 3 /h 

Each sludge pit is equipped with 3 recirculation pumps + 1 back-up pump. Unit pump 

capacity is 450m 3 /h, thus provided total sludge recirculation capacity is the following: 

Phase 1: 2 700 m 3 /h 

Phase 2: 4 050 m 3 /h 

2.5.1.2. EXCESS SLUDGE EXTRACTION 

Sludge balance is summarized below: 


(a) BOD 5 load removed in 

aeration tanks 

14 515 kg/d 22 753 kg/d 

(b) Sludge production ratio 0.8 kg DS / kg BOD 5 removed 0.8 kg DS / kg BOD 5 removed 

(c) Sludge production 

(c) = (a) x (b) 

(d) SS load in treated 

effluent (15 mg/l) 

(e) Excess sludge production 

(e) = (c) - (d) 

(f) Excess sludge 

concentration 

11 612 kg DS/d 18 202 kg DS/d 

441 kg/d 743 kg/d 

11 171 kg DS/d 17 460 kg DS/d 

8.5 g/l 8.5 g/l 

(g) Excess sludge daily flow 1 314 m 3 /d 2 054 m 3 /d 

(h) Excess sludge hourly 

flow 

(extraction duration: 10 h/d) 

132 m 3 /h 206 m 3 /h 

Excess sludge will be pumped from sludge pits to the gravity thickeners. Each sludge pit is 

equipped with 1 excess sludge extraction pumps + one backup pump of unit capacity 80 

m3/h. Thus total excess sludge extraction capacity is: 

Phase 1: 160 m 3 /h 

Phase 2: 240 m 3 /h 

2.5.2. THICKENERS 

Thickeners are of circular gravity type. They are feeded with sludge directly by the excess 

sludge pumps, situated in the sludge pits. Each thickener is feeded by 1 sludge pit. 

The inlet sludge is allowed to settle and compact, and the thickened sludge is withdrawn 

from the bottom of the tank. 

Gravity thickeners are designed on the basis of a solids loading of 26 kg DS/m²/d 

Sludge quantities to be treated are the following: 






Sludge load to be thickened (kg 

DS/d) 

11 171 17 460 

Sludge flow to be thickened (m 3 /d) 1 314 m 3 /d 2 054 m 3 /d 

The characteristics of the thickeners are: 

- Thickener diameter ..........................................................................17 m 

- Unit surface.................................................................................. 227 m² 

- Number of units 

Phase 1......................................................................................2 

Phase 2......................................................................................3 

- Surface......................................................................................... 227 m² 

Phase 1............................................................................ 454 m² 

Phase 2............................................................................ 681 m² 

- Sludge storage depth......................................................................3.5 m 

- Total peripheral depth.....................................................................4.5 m 

Effective operating conditions of thickeners are thus the following: 

- Effective solids loading rate: 

Phase 1............................................................. 24.6 kg DS/m²/d 

Phase 2............................................................. 25.6 kg DS/m²/d 

- Effective hydraulic loading rate: 

Phase 1.................................................................. 0.29 m3/m²/h 

Phase 2.................................................................... 0.3 m3/m²/h 


Phase 1................................................................................1.2 d 

Phase 2..............................................................................1.16 d 

In order to minimize operating costs, no chemicals are added for sludge treatment at KY 

WWTP. 

Biological excess sludge enters the thickeners at the top. 

Thickeners are fitted with a centrally driven rotary mechanism with a diametric bridge. A 

vertically mounted picket fence is attached to the rotary mechanism and enhances the 

release of interstitial water and gas contained in the sludge and allows therefore correct 

sludge settling and thickening conditions in the tank. 

Scrapers positioned directly above the thickener floor transfer the deposited sludge to a 

central hopper from where it is recovered by the thickened sludge pumping station and 





conveyed to the sludge drying beds. The thickened sludge pumps are designed for the 

following sludge flows: 


Thickened sludge dry matter 

concentration 

30 g/l 30 g/l 

Thickened sludge flow (m 3 /d) 372 m 3 /d 582 m 3 /d 

The thickened sludge pumping station is equipped with 1 pump (variable speed) + one 

backup pump (45 m3/h in phase 1, 73 m3/h in phase 2). Thus, maximum daily operating 

time of sludge pumps is 7.3 h in phase 2 and 4.7 h in phase 1. 

Supernatants are conveyed by gravity to the backflow pumping station. Supernatant flows 

are the following: 

Phase 1: 942 m 3 /d 

Phase 2: 1 472 m 3 /d 

2.5.3. DRYING BEDS 

Drying beds are dimensioned for the thickened sludge quantities indicated above, and 

based on following parameters: 

The characteristics of the drying beds for KY WWTP are summarized below: 

- Inlet dry matter concentration: 30 g/l 

- Maximum height of sludge layer in drying beds: 0.30 m 

- Outlet dry matter concentration: 40% 

- Required drying period: 15 days 

- Sludge moisture loss : 20% by evaporation and 80 % by drainage 

Drying beds have thus the following characteristics: 

- Drying area per unit ..................................................................... 450 m² 

- Number of units: 

Phase 1....................................................................................32 

Phase 2....................................................................................54 

- Total drying area: 

Phase 1....................................................................... 14 400 m² 

Phase 2....................................................................... 24 300 m² 

Operating conditions are summarized below: 

- Effective loading rate: 

Phase 1............................................................. 0.78 kg DS/m²/d 

Phase 2............................................................. 0.72 kg DS/m²/d 





- Dried sludge specific density..............................................................1.2 

- Dried sludge outlet volume: 

Phase 1........................................................................ 23.3 m 3 /d 

Phase 2........................................................................ 36.4 m 3 /d 

- Drainage water volume: 

Phase 1......................................................................... 279 m 3 /d 

Phase 2......................................................................... 436 m 3 /d 

2.5.4. COMPOSTING AREA 

The composting area for KY WWTP is calculated based on the following assumptions: 

- Mixture composition: 

Dried sludge (with 40% dry matter concentration): 1 volume 

Fresh support agent: 2 volumes 

Compost:1 volume 

- Product volume reduction: 

10% at mixture 

40% after fermentation 

- Retention time in composting area: 

Fermentation: 1 month 

Ripening and storage: 2.5 month 

Total: 3.5 month 

The corresponding characteristics of the sludge composting step at KY WWTP are the 

following: 

- Dried sludge volume: 

Phase 1............................................. 23.3 m 3 /d = 709 m 3 /month 

Phase 2.......................................... 36.4 m 3 /d = 1 107 m 3 /month 

- Required volume of support agent: 



- Total volume mixture to be composted: 


Phase 2 ....................................... 145.6 m 3 /d = 4 429 m 3 /month 

- Required total area (composting and storage): 

Phase 1....................................................................... 12 659 m 2 

Phase 2....................................................................... 19 470 m 2 





The annual composting mass balance for KY WWTP Phase 1 and Phase 2 is given in the 

figure below: 

Fig. 2. ANNUAL MASS BALANCE FOR SLUDGE COMPOSTING AT KY WWTP 

DRIED SLUDGE 

Phase 1 : 8 504 m 3 

Phase 2 : 13 286 m 3 

SUPPORT AGENT 

(3 volumes for 1 sludge volume) 

Phase 1 : 25 514 m 3 

Phase 2 : 39 858 m 3 

Phase 1 : 34 018 m 3 

Phase 2 : 53 144 m 3 

Raw product mixture 

Phase 1 : 30 616 m 3 

Phase 2 : 47 830 m 3 

Mixture after loss (10 %) 

Fermentation (volume loss : 40 %) 

Phase 1 : 18 370 m 3 

Phase 2 : 28 698 m 3 

COMPOST 

TO BE EVACUATED 

COMPOST TO BE RECYCLED 

AS SUPPORT AGENT 

(1 volume for 1 sludge volume) 

Phase 1 : 9 866 m 3 

Phase 1 : 8 504 m 3 

Phase 2 : 15 412 m 3 Phase 2 : 13 286 m 3 

Other than the specific composting area, KY WWTP works will also be fitted with a mixture 

area and a support agent storage area, which is designed for support agent requirements 

for 2 weeks. 





2.6. ODOUR TREATMENT 

The odour treatment process is sized for the preliminary treatment part and more 

specifically for the fine screening. Indeed, there may be serious odour problems at the 

screens. 

The dimensions of the preliminary treatment building will be equivalent in phase 1 and in 

phase 2. The biofilter is sized directly for phase 2. 

The air renewal rate in this building is 10/h. The renewal rate is chosen on the basis of 

measurements performed at numerous sites using different treatment processes and with 

a wide range of odour emanation. 

The deodorisation must therefore treat the following emissions: 

Effective volume of building 

2320 m3 

Renewal rate (unit/h) 10 

Air flow to be treated 

23 200 m3/h 

The values for ensuring no perceptible odours above the filter bed with the ceiling contents 

are as follows: 

H2S 

Mercaptans 

Total sulphur 

NH3 

Amines 

Total nitrogen 

Aldehydes + cetones 

≤ 0.1 mg/m³ 

≤ 0.07 mg/m³ 

≤ 0.15 mg/m³ 

≤ 0.10 mg/m³ 

≤ 0.15 mg/m³ 

≤ 0.3 mg/m³ 

≤ 0.4 mg/m³ 

Biofiltration is based on the use of micro-organisms within treatment systems that degrade 

foul-smelling and toxic organic and mineral compounds into odourless and atoxic 

compounds. 

The micro-organisms can only develop in the presence of moisture, air and heat. 

2.6.1. MOISTURE 

Sufficient moisture must be maintained at all times at the surface of the filter material so 

that foul-smelling compounds, which are carried away in vitiated air, can be absorbed at 

any moment. The diffusion process is encouraged by having a large area that facilitates 

absorption of the molecules. The large total net area of filter material must meet these 

requirements so that the biofilter can also support the optimum number of micro-organisms 

to encourage the reaction mechanism. The necessary moist medium is created by an 

automatic sprinkling system that distributes water and if necessary nutrients over the upper 

surface of the filter material. 





2.6.2. AIR 

The oxidation of foul-smelling compounds is encouraged by enzyme reactions, the 

substrates for which are generated by micro-oganisms. These micro-organisms can only 

develop if oxygen is present. This condition must be guaranteed in the filter material at all 

times. Consequently, the organic material selected must be as uniform as possible and 

permeable to air, but sufficiently rigid to withstand settlement and crushing, which would 

result in the filter becoming blocked. 

2.6.3. TEMPERATURE 

The temperature within the bed is a prerequisite to ensuring auto-regeneration of the 

micro-organisms: the "optimum" temperature is between 7°C and 40°C. 

The choice of filter material is a direct consequence of these three constraints. The contact 

area in the material itself must be as large as possible to encourage the activity of the 

micro-organisms. Similarly, the filter material must have a high water-retention capacity. 

Peat, amongst other things, has proved to be an ideal filter medium that meets these 

different conditions. 

The filter layer must be homogeneous and permeable to the air, to ensure uniform 

distribution of the air to be treated throughout the filter. The result is good oxygenation 

throughout the filter, which is favourable to the activity of the micro-organisms. 

The filter consists of a mixture of peat and hardly biodegradable, fibrous lignocellulose 

material. This material gives the filter layer a little rigidity. Peat has a very high waterretention 

capacity and the structural materials added ensure that the filter layer remains 

porous. Peat is the only material that can be used to obtain a depth greater than 1.5 m. It 

offers an exchange area of the order of 100 to 300 m²/m³ of biofilter. 

The filter is designed in such a way that it distributes air uniformly and reduces compaction 

effects, which would lead to a loss of head and reduction in air renewal together with an 

increase in energy consumption due to greater head losses. 

2.6.4. BIOFILTER DESIGN PARAMETERS 

The main conditions to be fulfilled are as follows: 

- Temperature of air to be treated: 7 - 35 °C 

- Relative humidity of air : 70 - 90% 

- Relative humidity of filter: 30 - 70% 

- Average head loss: 40 - 100 mmWC 

The assembly includes the following: 

- The filter substrates 

- The grating support 

- Water distribution on the biofilter 





- The filter sprinklers 

The design of the biofilter must ensure the following in normal situations: 

- A dwell time on the upper bed of 40 seconds or more 

- A throughflow speed of 0.06 – 0.065 m/s 

The geometric and functional characteristics are thus: 

- Discharge to be treated: 23 200 m3/h 

- Area of filter bed chosen: 110 m² 

- Depth of filter bed chosen: 2.3 m 

- Flow speed through filter bed chosen: 211 m/h 

- Contact time: 39 s 

- Treatment rate: 91 m3 gas/m3 of biofilter 

Foul air is removed from the preliminary treatment building by suction pipes that supply a 

suction fan. The foul air is then transferred under the biofilter. 

Fresh air is admitted along the walls of the preliminary treatment room via aluminium grilles 

fitted with shutters to keep out the rain and insect screens. 

The fresh air admission grilles will be installed opposite the foul air extraction grilles to 

create a throughflow effect inside the building. 

The fresh air inflow rate will be 80% of the extraction rate in order to maintain a slight 

negative pressure inside the building. 





3. 

PLANT DESCRIPTION 

3.1. GENERAL 

Khan Younis waste water treatment plant is situated on a long strip of land (171 m x 

680 m). Old solid waste dump cells are adjacent to the KY WWTP, but actually located 

outside the KY WWTP site. 

The treatment structures themselves are therefore grouped together at one end of this 

land, while most of the area is to be used for sludge composting and for drying beds. 

The main entrance to the plant is opposite the administrative building; this entrance will in 

theory be used only be light vehicles. It gives access to a 65 m x 45 m turning area. Most 

of the treatment structures and premises are organised around this inner courtyard: the 

administrative building, plant, preliminary treatment, air production plant, electrical 

equipment buildings, aeration tanks. 

This inner courtyard also provides access to heavier-duty roads, which, together with a 

second entrance on the site, serves the sludge composting areas and drying beds; these 

heavy-duty roads are necessary as trucks loaded with sludge and inert materials will use 

them frequently. 

Light-duty, stabilised roads provide exceptional access for work on certain structures. 

Lastly, in an area slightly away from the traffic areas, are the clarifiers and sludge 

thickeners. 

The overall layout takes into account in particular the future construction of phase 2, by 

relegating the future structures (1 aeration tank, 1 thickener, 2 clarifiers) to the periphery so 

that their construction will not disturb the general operation of the installation. 

3.2. CONNECTION PIPES 

The design includes all the pipes outside the structures, within the site, from the outlet from 

the preliminary treatment facilities as far as the drying beds and composting alls. 

The various networks are presented on drawing DD. PIP-001. 





This corresponds to: 

• A set of cast iron pipes of various diameters for all the pressure pipes from the outlet 

of distributor DW1 as far as the clarifiers; 

• A set of concrete pipes of various diameters for clarified liquor from the clarifier as far 

as the intermediate pumping station; 

• A set of cast iron pipes of various diameters, for recirculating and extracting sludge 

from the sludge sump as far as the aeration tanks and thickeners; 

• HDPE pipes of various diameters, for supplying the drying beds, for the installation 

water, and leachate collection; 

3.2.1. LAYING CONDITIONS 

The layout of the networks was designed according to the following principles: 

• Avoid passing under the base of a structure as far as possible 

Prefer laying along roads 

Dissociate wet networks from dry networks 

Minimise laying depths 

Laying depths should comply with the following requirements: 

• Minimum cover above the soffit ....................................................................0.80 m 

Maximum depth occasionally accepted.............................................................5 m 

Placing should comply with the following conditions: 

• Sand bed below the invert .............................................................................10 cm 

Small quantity of compacted fill above the soffit ....................................40 cm min 

Minimum space between two similar pipes ....................................................0.4 m 

Minimum slope: ................................................................................................. 1% 

3.2.2. CONNECTIONS TO STRUCTURES 

All pipes will be connected to concrete structures with Puddle and sleeves 

When appropriate, an electrical isolation joint will be fixed; 

When arriving from the ground, all pipes will be blocked in mass concrete through the 

slabs. The pipes (under ground pipes) will be encased with concrete and/or supported 

by thrust block. 





3.3. PRELIMINARY TREATMENT 

3.3.1. FLOW METERING 

Electromagnetic flow meters are fitted on each raw water pipe before intlet in the screening 

channels 

3.3.2. SCREENING 

Raw water arrives in the preliminary treatment structure from two different origins: 

• from Khan Younis via a ND700 pipe running from pumping station PS8; 

from the Eastern Villages via a ND450 pipe. 

In both cases the effluentr arrives via a stainless steel swan neck in a channel set at +3.00 

m from the ground level (normal-maximum water level at 57,53 WL in phase 2).The limit of 

supply in respect of the WWTP is 1 m beyond the bare outer surface of the cut-off, where a 

dielectric joint will be installed for connection with the raw water pipes. 

A channel supplies a diverging section giving access to 3 screening channels 1.00 m wide 

(2 of which will be used in phase 1). Each channel can be isolated by installing an 

aluminium stop log. 

A fine screen with the following characteristics is installed in each channel: 

Type 

Vertical, automatically cleaned 

Number 2 + 1 (phase 2) 

Maximum unit capacity 

1,779 m³/h 

Height of bar rack 

ca. 1.70 m 

Opening 

8 mm 

Installed capacity 

ca. 0.3 kW 

Miscellaneous 

Frame, slide rails and isolation stop logs 

With a screen working in exceptional conditions (50% clogged), it is possible for the 

maximum discharge of 1.14 m³/s to pass. 

The water level is then 1.60 m, i.e. more or less equal to the height of the screen. 

All the essential parts (frame, shafts, side plates, clip, embedded parts) are made of 316 

stainless steel or aluminium. The teeth are made of ABS or 316 stainless steel. 

The local control box has a protection index IP559; the slaving system includes: 

high and low level probes, 

clock-controlled cyclic operation, 

forced operation, 

temperature probe-controlled operation. 

A system of washing jets is used to clean the screens. 





A high-level probe is placed upstream of each fine screen to ensure safety in the event of 

the PLC probes malfunctioning. This probe triggers forced operation for the screen 

concerned. 

The quantities of waste extracted remain quite low: they are of the order of 1 m³/day in a 

separate network before compacting, i.e. about 0.5 m³/day after compacting, i.e. about 

0.3 skip per week. 

Screenings are drawn off to an automatic screw/compactor system, which has the 

following characteristics 

SCREENINGS TRANSFER SCREW 

Number 1 

Screw diameter 


ca. 190 mm 

ca. 1.1 kW 

SCREENINGS COMPACTOR 

Type 

screw 

Number 1 

Throughput 

ca. 2 m³/h 

Dryness 35 to 40% 


ca. 3 kW 

The casings are of special 250HB steel and the supports and flanges of 316 stainless 

steel. 

The screens are installed in sections that can be isolated from upstream and downstream 

by aluminium stop logs so that work can be carried out in the dry if necessary. 

A lateral by-pass channel with a weir upstream of the screens set at 57.70 is used to draw 

off 2,100 m³/h, i.e. more than a channel in phase 2, if a screen is completely blocked or a 

channel accidentally closed by a stop log. 

The downgraded operation case will occur when a channel will be out; in this case, all 

phase 2 flow can be handle with the 2 others under an upstream water level of 57.67. 

3.3.3. GRIT/GREASE REMOVAL 

A diverging section then supplies a perpendicular channel, itself supplying each 

preliminary treatment channel via two pressurised orifices measuring 1.50 m x 0.45 m. 

Each preliminary treatment channel can be isolated with a manually controlled aluminium 

stop log. 

Each channel measuring 4 m x 4.20 m x 16.25 m is capable of handling 1.035 m³/h in 

normal working conditions and 1.957 m³/h in downgraded conditions (1 channel shut 

down). 

Each channel is equipped with the following: 

• 3 aeration turbines (unit discharge 22 m³/h) with a lifting bracket; 





• 1 automatic alternating scraper made of 316L stainless steel and aluminium for the 

secondary parts; 

• 1 Vortex Monobloc type grit extraction pump: unit discharge 20 m³/h, housing made of 

cast iron (i.e. 2 pumps in phase 1). 

It should be noted that a stand-by pump is supplied in the store for rapid changeover. 

Grit is pushed to pits at the head of the channel, from where the grit pumps (one for each 

channel + 1 stand by in the ware house) draw off the waste to a grit classifier with a 

discharge of 60 m³/h. 

The drained grit is poured into a 15 m³ skip. Water drained from the grit is recovered and 

conveyed in gutters to a general water tank, from which a pump delivers it to the head of 

the preliminary treatment channels. 

Openings are left in the building walls so it can be deodorised later with an air renewal rate 

of k = 10. 

Grease is recovered from the surface at three weirs and conveyed to a chute, which 

removes it sideways to a grease pit with a capacity of 20 m³. A ND100 tube at the bottom 

of the pit is used to remove the grease by truck. 

Leaving the preliminary treatment channels, the liquor pours over 10 lateral sills (per 

channel) set at 57.36, supplying a perpendicular outlet channel. From this channel, 

1 submerged orifice measuring 1 m x 1 m supplies distributor DW1; this divides the liquor 

among the three secondary treatment lines (2 lines operational in phase 1) via ND600 

pipes. 

3.4. AERATION TANKS 

3.4.1. ANOXIC ZONE 

The pre-treated liquor is conveyed to the 3 aeration tanks (2 in phase 1) via three specific 

ND600 pipes (2 in phase 1). 

Liquor is admitted into the tank through submerged orifices set at 51.96 in the anoxic zone; 

recirculated sludge is introduced into the same anoxic zone by ND600 swan's necks above 

the cut-off crest level. 

The anoxic zone of each tank comprises two mixers with three 316 stainless steel blades, 

mixing 2.632 m³/h with a power of 6 kW. A fixed guide system with a winch is used to 

install and remove the mixers. 

3.4.2. AERATED ZONE 

Liquor is introduced into the aerated zone by 2 submerged orifices 1.5 m x 1.0 m. 

The channel shape of the tanks enables the liquor to be entrained successively into 

aerated zones above the air inlet, then into dead zones, then aerated zones, then dead 





zones, and finally aerated zones. This ensures maximum mixing of the liquor with the 

oxygen contained in the injected air. Curved guide walls steer the flow of liquor to the end 

of the channels in order to avoid head losses and cavitation. 

Each tank has 6 mixers with cast iron housings and banana blades with a unit power of 

6 kW. This mix and circulate the flow of liquor, generating a horizontal velocity of 0.35 m/s. 

A fixed guide system with a winch is used to install and remove the mixers. 

Air is introduced at the bottom of the tank by fine-bubble diffusers with the following 

characteristics: 

Number of diffusers per tank 2,016 

Unit length 

Material 

Unit discharge 

1 m 

perforated EPDM membrane 

9 m³/h 

The diffusers are installed on 16 316stainless steel frames per tank, with 126 diffusers per 

frame. 

These metal frames are set on supports installed at the bottom of the tank (installed with a 

ballasting device). A quick coupling system enables the frames to be connected at the 

bottom of the tank with the 16 plunging ND160 316 stainless steel pipes delivering the 

compressed air. Each tube is fitted with a shut-off valve and pressure relief valve. Two 

ND300 feeders installed on the central cut-off supply the plunging tubes from the northern 

end of the tanks. 

Liquor leaving the tank pours into an outflow pit via a 3 m long weir set at 56,40; this pit 

collects the liquor from the 2 aeration tanks. 

Two concrete footbridges that also act as tie bars provide access to the mixers and can be 

used to cross the tanks for inspection purposes. 

3.4.3. AIR PRODUCTION PLANT 

Air is produced by turbo-compressors installed in a room close to the aeration tanks. 

The operating principle allocates a turbo to a specific tank so that the inflow of oxygen, and 

hence air, is very precisely controlled in accordance with the requirements measured by 

the Redox probes, during the aeration period of time. 

Eventually, there will thus be 3 turbos plus one on standby (in phase 1: 2 + 1, in phase 2: 3 

+1). The turbo enables the exact quantity of oxygen required to be supplied by 

progressively and continuously opening the admission blades. 

Each turbo supplies 18,000 N m³/h of air at the bottom of the tank. The air is taken directly 

from outside the building, where it is cooler. Dust filters control the intake of air and sound 

traps are installed at the inlet. The compressed air is sent directly to the dedicated tank via 

a 316 stainless steel ND600 pipe. 

Each turbo outlet is fitted with an air-release value, a check value and a butterfly value. 





In addition, tappings with manual isolating valves on each outflow pipe enable the turbos to 

be interconnected to them via a horizontal cross-link. Each turbo can thus supply each tank 

specifically if the operator so decides. 

Wide openings at the top and bottom of the opposite façades allow air to be renewed 

inside the building. 

The project does not provide for soundproofing enclosures to be installed for each turbo, 

but hoods for conveying hot air from the motors outdoors. Exhaust fans will be installed in 

the blower room. 

3.5. CLARIFICATION 

3.5.1. DISTRIBUTOR DW2 

Aerated liquor is transferred by an ND1400 pipe to distributor DW2. 

This has two levels of distribution: 

• distribution of the discharge to 3 pairs of clarifiers (2 pairs in phase 1); 

• redistribution of the discharge to 3 clarifiers working out of the 4 in phase 1, or to 

5 clarifiers working out of the 6 in phase 2. 

The weir is fitted for this purpose with 3 channels, each divided into two half-lengths. 

Aluminium stop logs can thus be installed manually from a longitudinal access footbridge. 

3.5.2. DEGAZING STRUCTURE 

A siphon like path is followed by waters in degassing structure; this will allow to air release 

in the main pit before to be conveyed by a submerged (for avoiding water disturbance on 

the weir) orifice to the distribution weir. Then each degassing structure feeds 2 outlets 

toward the clarifiers by 2 x 3,5 m weirs which can be isolated by penstock. 

3.5.3. CLARIFIERS 

Each clarifier, 33 m in diameter, is supplied from the degassing structure via a ND600 pipe 

that feeds 4 pressurised orifices situated on the central drum. A peripheral metal plate 

limits disturbance at the water surface. 

Around the edge, a circular notched weir situated behind a floating debris protection plate 

admits clarified liquor into a peripheral chute with a longitudinal slot that empties into an 

outflow pit. 

The two pairs of phase 1 clarifiers thus empty via a ND900 pipe to the evacuation pit. 

Lastly, a peripheral scraper mounted on the rotary bridge collects floating debris and 

directs it to a floating debris pit situated between each pair of clarifiers. The floating debris 

is then pumped to the entrance of the preliminary treatment line. 





Sludge that has settled to the bottom of the clarifiers is sucked up by plunging tubes and a 

vacuum pump mounted on the rotary bridge towards the top of the central drum, where it is 

poured into a ND300 pipe supplying the under-floor sludge sump. 

3.5.4. SLUDGE SUMP 

There is one sludge sump for each pair of clarifiers (2 sumps in phase 1). Each sump is 

equipped with four centrifugal-type recirculating pumps with a unit discharge of 450 m³/h (3 

+ 1 standby) that deliver the sludge to the anoxic zone of the aeration tanks via a ND600 

pipe. A ND300 valve enables the sump pipe to be isolated. Each pump is fitted with a 

check valve and shut-off valve. Similarly, each pump has a fixed handling system 

consisting of a guide, chain and winch. 

Each sump is equipped with high and low level float detectors. 

The excess sludge extraction pumps (1+1 on standby) are installed in the same sump; 

these are centrifugal pumps with a unit discharge 80 m³/h that supply the sludge thickeners 

via a HDPE ND200 pipe. A bracket and winch are used to handle the pumps outside the 

sump. 

The same arrangements are made for operation and handling as in the case of the 

circulation pumps. 

3.5.5. SCUM PIT 

Scum collected by the pickets in the degassing and distribution wells and clarifiers is 

conveyed by gravity along ND 200 pipes to the scum pits (2 in phase 1 and 3 in phase 2). 

From there, the scum is transferred by submersible pumps (1+1 standby, capacity 10 

m3/h) to the grease tank, where it is mixed with grease from the grit and grease removal 

tanks and taken away from the treatment plant by vacuum trucks. 

3.6. TERTIARY TREATEMENT 

3.6.1. GENERAL 

The tertiary treatment building fulfils various functions linked with the final treatment of the 

waste water: 

• an intermediate lifting station that pumps the water to the upper channel spilling on to 

the sand filters; 

• the sand filters themselves with the associated requirements: a filtered water tank, a 

dirty water tank and the reverse blowing system for unclogging the filters; 

• a UV disinfection system for the final treatment; 

• a pumping station for transferring water to the infiltration basins or the emergency sea 

outlet. 





3.6.2. INTERMEDIATE LIFTING STATION 

Clarified water is admitted at level. 51.68 into a diversion pit of the following dimensions: 

l:10.00 m x w: 9.00 m x h: 4.30 m. 

3 submerged centrifugal pumps (2 + 1 stand-by), to be extended to 4 in phase 2, with unit 

capacity of 1,306 m³/h lift the water via a swan's neck to the longitudinal filter feeder 

channel set at 56.50 (normal water level 57.72). 

The pit is equipped with high and low level probes and an ultrasonic level sensor. 

3.6.3. SAND FILTERS 

From this channel, submerged orifices (1.00 x 1.50 m) supply a weir set at 57.58, which 

admits water laterally into each filter itself. A valve isolates each filter independently. 

The water level in the filter is maintained at 57.35 by means of a motorised ND450 butterfly 

regulating valve at the filter outlet. The valve opening is regulated by an ultrasonic level 

sensor. 

When the head loss and thus the level reaches a threshold value, washing is triggered. 

The depth of water on the filter is 1.20 m. 

The filter is 1.40 m deep; the specific size of the particles is 1.35 mm. 

The bottom of the filter consists of a 10 cm layer of 4/8 mm gravel. Below the gravel, 220 

mm diameter nozzles deliver the filtered water to a collecting floor at 53.80; some 50 

nozzles/m² are installed to admit 3030 Nm³/h of wash water per filter. The water is then 

directed to the filtered water tank measuring l: 26.50 m x w: 7.20 m x h: 4.20 m. 

3.6.4. DISINFECTION 

Via a 1.50 m x 2 m side channel set at 51.80, the water is admitted at the top end of the 

UV disinfection channel, which comprises 2x2 racks of lamps installed in phase 1 (2x1 

additional rack in phase 2). 

At the end of the channel, a regulated sliding valve that maintains the level in the UV 

channel allows the disinfected water to enter the treated effluent PS. 

A 1.50 m wide by-pass channel at the side, set at the same elevation as the UV channel, 

enables the water to be diverted so that work can be carried out on the lamps when stop 

logs are installed. 

Stop logs can also be installed at each end of the disinfection channel. 

3.6.5. FILTER WASHING 

When the outlet regulation valve is closed, washing is triggered. 





Water sweeps across the surface of a filter at the base of the feeder channel. This is 

maintained to produce a lateral flow that carries large flocs towards the side weir set at 

56.65. 

Three washing sequences are provided: 

1. air blowing to loosen the material; 

2. air blowing + low water discharge; 

3. rinsing with high discharge. 

The air is supplied by 2 blowers (1+1 stand-by sized for the final phase) which supply the 

base of the filters via ND200 316 stainless steel pipes. 

Wash water is taken from the filtered water tank by pumps with a discharge of 455 m³/h 

(2+1 stand-by sized for the final phase). Clean water is introduced, like air, at the bottom of 

the filters, on counter-flow basis. Dirty water is recovered by the side channel with 

longitudinal weir at 56.65, and enters the dirty water tank. This dirty water is then directed 

along a channel below the UV disinfection towards the two 135 m³/h lifting pumps (1+1 

stand-by sized for the final phase). 

3.6.6. TREATED EFFLUENT PUMPING STATION 

The disinfected effluent issued of the UV disinfection is pumped by three electropumps ( 2 

+ 1 standby), phase 1 and four electropumps (3 +1 standby) in phase 2. The unit capacity 

of the pumps when pumping to the infiltration basins is 1200 m3/h (for each phase) with a 

TDH of 29 m (phase 1) and 40 m(phase2). 

The unit capacity is the same when pumping to the sea outfall with a TDH of 31 m (phase 

1) and 42 m(phase 2). 

As indicated below, the treated effluent can be transfer to the infiltration basins or to sea 

outfall. 

3.6.7. INDUSTRIAL WATER 

Industrial water is produced by a variable-speed compression unit consisting of three 

electropumps (2 + 1 standby, total capacity 72 m 3 /h) and a 500 l tank installed on a 

platform (2 m x 1.5 m) in the sand filtration building. A ND125 manifold collects disinfected 

water from the treated effluent pumping station. The pumps supply a single ND65 HDPE 

distribution network. ¾’’ taps are installed in the treatment plant to provide service water. 

The pressure at the distribution taps is fixed at 4 bar. The pumps will be started up by a 

pressure switch. 

3.6.8. GRAVITY THICKENERS 

Excess sludge is conveyed by a ND 200 pipe from the sludge pits (2 pits in phase 1, 3 in 

phase 2) to the thickeners (2 thickeners in phase 1 and 3 in phase 2). Sludge is introduced 

in the centre of the thickener, through a surge skirt. The structure is equipped with a mobile 

bottom scraper bridge that pushes the sludge to the central recovery pit and with a picked 

fence that concentres the sludge. The thickened sludge is removed at the bottom of the 





thickener. Recovery pumps (1 + 1 standby sized for the final phase) with a variable 

discharge (45 m3/h in phase 1, 73 m3/h in phase 2) installed in the thickened sludge 

pumping station transfer the sludge to the drying beds via a ND200 pipe. 

Overflowing water is recovered at the surface and conveyed by gravity to the backflow 

pumping station tank. Water draining from the composting and drying beds is collected at 

the backflow pumping station. Two submersible pumps installed in the tank with a 

discharge of 132 m3/h (1 +1 standby sized for the phase finale) transfer the water to the 

head of the treatment process between the screens and the grit and grease removal tanks. 

3.6.9. SLUDGE DRYING 

Sludge from thickeners is fed by 1 (+1 back-up) feeder pumps with unit capacity 80 m3/h to 

the drying beds through a ND200 cast iron pipe. 

Sludge is placed on the drying beds in a 20 to 30 cm layer and allowed to dry following two 

principles: 

• Drainage trough the sludge mass and supporting sand and gravel layers. Drainage 

water is collected in under drainage system and returned to the effluent treatment line. 

• Evaporation from the surface exposed to the air. 

The layer of sludge spread into the beds is limited to about 30cm thickness, in order to 

avoid clogging of the top layer of fine sand. 

The total drying area is divided into individual beds. Distribution boxes are used to divert 

the thickened sludge flow into the selected drying bed. Splash plates are placed in the 

drying beds in front of the thickened sludge outlet in order to prevent erosion of the sand 

and to spread the sludge over the bed. 

Each drying bed is isolated with a manual gate valve. Every day, depending on sludge 

level in the bed, the operating personnel select the drying bed to be supplied with 

thickened sludge. 

After drying, sludge is spadable and is removed from the drying beds by a front end loader 

and transported towards mixture area prior to composting. 

Taking into account local conditions in Khan Younis, the moisture content in dried sludge is 

estimated to about 40% after 15 days drying period. 

Drainage water is collected under the drying beds by a drainage system and conveyed by 

gravity to the backflow pumping station in the thickeners area, from where it is pumped to 

the distribution channel upstream degritting/degreasing tanks. 

The drainage system is constituted by perforated plastic pipes or vitrified clay pipes laid 

under the whole drying bed surface with open joints and sloped at a minimum of 1%. 

Sand layers in the drying beds need to be replaced regularly. 





3.6.10. SLUDGE COMPOSTING 

After drying, the sludge produced in KY WWTP is stabilised and transformed by 

composting. 

The specific objectives of sludge stabilization include following actions: 

• Decompose sludge organics to stabilized humus. 

• Reduce the mass and volume of sludge. 

• Obtain a sanitised organic soil improvement agent. 

• Destroy/control pathogenic organisms. 

A mixture of dried sludge, fresh support agent and compost product will be composed 

using a front end loader with a bucket which is fitted with an integrated mixing device. The 

mixture is than disposed on the open air composting area in shape of windrows. 

During fermentation phase, windrows are regularly returned in order to assure sufficient 

aeration, which is needed to provide oxygen for the biological oxidation and to allow 

evacuation of the steam released in the compost mass. 

After fermentation phase, a ripening phase constitutes the last phase of composting. 

During this phase, degradation of organic matter is completed and the compost obtains the 

final agronomic value. 

Two front end loaders are required for manipulation of dried sludge and compost. 

In operating conditions, part of the total composting area surface is left free for circulation 

of the front loaders (for constitution and returning of compost windrows); another part 

corresponds to the compost windrows themselves, and third part corresponds to storage 

area of finished compost (before evacuation to agricultural area). By this way, it is assured 

that only final ripe compost will be transported to agricultural reuse areas. 

A central area is provided between phase 1 and phase 2 composting areas. It is composed 

of: 

- A bulk storage area for structuring agent: 20 m x 40 m; height of surrounding wall 

= 2.5 m (with opening on the front side for truck access); 

- A mixture area: 10m x 10m; Side wall on 2 sides, height = 2.5 m; 

- Parking space for 2 front loaders. 

Drainage water from composting area is evacuated to the backflow pumping station in the 

thickeners area, from where it is pumped to the distribution channel upstream 

degritting/degreasing tanks. 

Scum collected by the pickets in the degassing and distribution wells and clarifiers is 

conveyed by gravity along ND 200 pipes to the scum pits (2 in phase 1 and 3 in phase 2). 

From there, the scum is transferred by submersible pumps (1+1 standby, capacity 10 

m3/h) to the grease tank, where it is mixed with grease from the grit and grease removal 

tanks and taken away from the treatment plant by vacuum trucks. 





3.7. BIOLOGICAL FITTER – ODOUR TREATMENT 

Foul air is removed from the preliminary treatment building by suction pipes supplying a 

fan via an aluminium sheath 750 mm in diameter. The foul air is blown under the biofilter. It 

then passes through the filter bed consisting mainly of peat*. It leaves the biofilter 

cleaned**. A sprinkler system is installed above the filter bed to ensure the optimum 

moisture content for foul-smelling molecules to be absorbed. 

* The depth of biological filter media is 2.3 m 

** And without undesirable odour 

3.8. REMOTE CONTROL AND SUPERVISION 

3.8.1. INTRODUCTION 

This contract includes for the provision of a SCADA system for the monitoring and control 

of the Khan Younis Wastewater Treatment Plant. 

The SCADA system shall be implemented as an operational management tool, i.e. shall 

provide with facilities to undertake the day to day monitoring and control of the Wastewater 

Treatment Plant and the production of general management information. 

3.8.1.1. SCOPE OF WORKS 

The Scope of Works comprises: 

- Supply, installation and commissioning the Khan Younis master and standby 

dispatcher equipement sized to monitor and control each treatment area within the 

works with a total of 1000 database points, complete with: 

Operating system. 

All necessary data storage devices. 

Printing devices. 

Furniture. 

Communications equipment and cabling for communicating with the PLC 

equipment located within the wastewater treatment works. 

- Supply, installation and commissioning of the Khan Younis WWTP operator 

workstation equipement (2 no.). 

- Supply, installation and commissioning of the Khan Younis WWTP SCADA 

system software. 

- Supply, installation and commissioning of the communications network, including 

lightning protection units, via: 

A cable communications network for the PLCs. 





- Supply, installation into Motor Control Centers, interface to instrumentation signals 

and commissioning of PLC equipment. 

- Supply of all necessary PLC programming equipment, software and licences. 

- Supply, installation, and commissioning of instrumentation equipment. 

- Configuration of the Khan Younis WWTP SCADA system database, including: 

4 PLCs. 

1000 database points. 

50 mimic displays. 

30 trend displays. 

15 reports. 

- Programming of all PLC equipment to perform local control. 

3.8.1.2. PHASING AND INSTALLATION NUMBERS 

The initial phase will include all Dispatcher equipment and PLC equipment associated with 

each process area of the Khan Younis WWTP initial phase. 

The Dispatcher equipment provided under this contract shall capable of supporting all 

process area of the Khan Younis WWTP second phase. 

3.8.1.3. SYSTEM OVERVIEW 

A control centre should be established in the administration building to accommodate the 

Dispatcher equipment and operator workstations. 

The system implemented shall be able to operate within the control strategy described 

within the General Spécification for SCADA but shall be flexible enough to be easily 

changed should the control philosophy change. 

3.8.1.4. DISPATCHER SYSTEM HARDWARE 

3.8.1.4.1. GENERAL 

A Hot Duty/Standby SCADA Dispatcher will be installed in the control centre located within 

the Administration Building of the site. 

Furniture for the control centre shall be supplied and installed by the contractor, to include: 

3 no. flat top desks complete with integral cabling system and electrical 

sockets. 

1 no. lockable cupboard to be located beneath desk. 

1 no. swivel chair with a duty of 8 hours continuous use. 

Furniture shall be matching. 

An outline drawing of the proposed SCADA system is provided here attached 





3.8.1.4.2. SYSTEM AVAIBILITY 

The system availability shall be as defined within the General Specification for SCADA. 

3.8.1.4.3. DATA STORAGE 

The SCADA system shall provide on-line historical data for all inputs/outputs on the 

system, whether real or derived signals, at: 

Digital signals: ............................................ On change of state. 

Analogue:................. Every 15 minutes and significant change. 

Integrated e.g. flow,mean, max and min:15 minutes, daily, weekly, 

monthly, yearly. 

3.8.1.4.4. REMOTE DATA TRANSFER 

Data from the SCADA system will allow to export to other computer systems via the 

Microsoft Excel product. 

3.8.2. SCADA SYSTEM FEATURES 

3.8.2.1. MMICS DISPLAY 

They will include all mimics listed below. 

All mimics shall be suitable for display all sizes of monitor supplied within the contract and 

careful design of the mimic shall be used to this end. Where mimics replicate those 

configured for the local PLC display, the mimics shall be identical to those displayed on the 

PLC display. 

The following requirements are required for all mimics: 

- The backgroung color for all mimics shall be subject to the approval of the 

Engineer. 

- All flows shall be displayed in engineering units as specified in the I/O listing of the 

agreed Functional Design Specification. 

- Each mimic shall have navigation “pushbutton” to the process overview, the 

geographical overview and associated process mimics. 

- The symbols used to describe the plant items shall be subject to the approval of 

the Engineer. 

- Mimics shall display process lines as colour dynamic with arrow indication of flow 

direction. 

- Alarms indication shall be animated within the relevant mimic. 

- Trend pages (including historic and current information) and the alarm summary 

page shall be available from every mimic. 





- Each on-site workstation shall be configured such that a screen dump can be 

printed by a single keyboard/on-screen action. 

- Control pages for all plant that can be controlled, overridden or plant data entered 

manually shall be available form every mimic. 





KHAN YOUNIS WWTP SCADA MIMICS 

MIMICS 

Quantity 

Phase 1 

Quantity 

(total) 

Phase 2 

SCADA Network Status Schematic 1 1 

WWTP Geographical Overview 1 1 

WWTP Process Schematic Overview 1 1 

Inlet Structure 1 1 

Fine Screening (General) 1 1 

Fine Screening (Individual) 2 3 

Compacting 1 1 

Grit and Grease Removal (General) 1 1 

Grit and Grease Removal (Individual) 2 3 

Grease Pit 1 1 

Backflow Pretreatment PS 1 1 

Aeration Tanks (General) 1 1 

Aeration Tanks (Individual) 2 3 

Blower Room 1 1 

Degazing and distribution well 1 1 

Secondary clarification (General) 1 1 

Secondary clarification (Individual) 4 6 

Return and Excess Sludge Pit 1 1 

Intermediate Pumping Station 1 1 

Sand Filtration (General) 1 1 

Sand Filtration (Individual) 4 6 

Treated Effluent Tank 1 1 

UV Disinfection 1 1 

Treated Effluent Pumping Station 1 1 

Gravity Thickeners (General) 1 1 

Gravity Thickeners (Individual) 2 3 

Thickened Sludge Pumping Station 1 1 

Backflow Pumping Station 1 1 

Incoming HV supply 2 2 

LV Distribution System 2 2 

A clearance for the following number of additional mimics shall be included 20% 10% 





3.8.2.2. ALARM FACILITIES 

The alarm list shall be configured in accordance with the General Specification for SCADA. 

The colours used to describe the state and priority of each alarm shall be subject to the 

approval of the Engineer. 

The facility shall be fitted to enunciate user definable alarms that have been accepted 

within a user definable period via the klaxon and lights associated with each control panel. 

The klaxon and light at each panel shall be reset on acceptance of the alarm. 

3.8.2.3. HISTORIC INFORMATION 

The SCADA system to automatically will save the current day’s historic data and delete 

any data greater than 365 days old at midnight. The facilities shall be provided to recover 

data greater than 365 days old from the archive device. 

3.8.2.4. REPORT GENERATION 

The configuration of 15 no. simple reports proving statistical information relating to the 

performance of the WWTP station. The content of the reports shall be subject to the 

approval of the Engineer. 

3.8.2.5. SCADA SYSTEM DATABASE CONFIGURATION 

The Contractor shall configure the SCADA database will be configured to include all 

input/output requirements. This shall include, but not be limited to: 

- Descriptions. 

- High, High-High, Low-Low and Low alarm levels. 

- Alarm text. 

- Alarm priorities. 

- Dead-bands. 

- Persistency (How long the signal must be in alarm condition before alarm is 

raised). 

- Historic data for trending of inputs etc. 

- Scanning intervals. 

The following shall be saved to disc, for display on the SCADA system: 

- Hours run for each item of plant, including pumps, screens, washers, compactors, 

conveyors, scrapers, mixers, blowers, presses and transporters, etc. 

- Flowmeter readings for incoming flow to treatment, return sludge and excess 

sludge, etc. 

- Total outlet flows to treatment ( per hour, day, month and year) 

- Ditto for the return sludge. 





- The total daily sludge capacity shall be calculated using the measured excess 

flow, the amount of dry substance returned and the amount of dry substance dewatered 

for each day, month and year. 

- The instantaneous and integrated power consumption for the WWTP. 

In addition the following elements dependent upon the Consumption of Power: 

- The instantaneous and integrated power consumption for the Biological Load. 

- The instantaneous and integrated power consumption for the Hydraulic Load. 

- The instantaneous and integrated power consumption for the “Time dependent” 

power consumers. 

3.8.2.6. SYSTEM RESPONSES TIMES 

The equipment supplied within this contract shall satisfy the response times as detailed 

within the General Specification for SCADA 

3.8.3. GENERAL OVERVIEW CONTROL PHILOSOPHY 

3.8.3.1. GENERAL 

The Waste Water Treatment Plant (WWTP) will be controlled by using Programmable 

Logic Controllers (PLCs) and a SCADA system in the Control Center. 

The PLC systems shall be located in several substations within the WWTP. 

- PLC1 Pretreatment 

- PLC2 Aeration Treatment 

- PLC3 Tertiary Treatment 

- PLC4 Backflow Pumping Station 

3.8.3.2. COMMUNICATION MEDIA 

Communication between computer users interfaces (e.g.operator workplaces) and central 

units will have to use electrical media. 

Communication between central units and PLCs will have to use optical fiber media. 





3.8.3.3. LOW VOLTAGE PROCESS DISTRIBUTION (LVPD) 

For operation of the drives each motor starter shall be equipped with a Selector Switch 

‘”Manual/ Auto” and push buttons. 

In “Manual” mode the drive can be operated via push buttons independent from the PLC. 

3.8.3.4. OPERATING LEVELS 

3.8.3.4.1. FIELD CONTROL STATION (LOCAL) 

The field control station has the highest priority. The station shall be equipped with a 

selector switch “Local/Off/Remote” and an adequate number of push buttons to operate a 

drive. 

In “Local” mode the drives can be operated locally via push buttons. All other control levels 

shall be disabled. Protection interlocks shall be hared-wired and remains operation. 

The field control stations shall be located in the vicinity of the equipment. 

Each drive shall be equipped with a separate emergency lock stop push button, wich is 

hardwired directly into the drive contactor control circuit. 

3.8.3.4.2. PLC – SCADA (SUPERVISION CONTROL AND DATA SUPERVISION) AND LVPD CONTROL 

If the selector switch at the field control station is set to “REMOTE” and, 

- The selector switch at the LVPD is set in “AUTO”, the operation from the 

corresponding PLC in automatic or in manual mode by SCADA shall be possible. 

Start/Stop/Open/Close/Over-ride/Inhibit will be possible via SCADA. 

- The selector switch at the LVPD is set in “MANUAL”, the operation from the LVPD 

in manual mode shall be possible. 

By switching from automatic to manual the drives shall hold the actual state of operation, 

i.e. an operating drive keeps on running, a switched off drive is not started. 

3.8.3.5. MMI (MAN MACHINE INTERFACE) 

Each PLC shall be equipped with an operator interface with touch screen facility. Mimic 

page reflecting the current status and leves of the plant, to wich the PLC is interfaced. 

Also modifications such timers, counters or other parameters shall be possible. 





3.8.3.6. LOCAL CONTROL PANEL FOR PACKAGE UNITS 

Package units shall be independent panels, located on site near by the belonging 

machines/equipment. Where appropriate field control units shall be provided, for the safety 

of the operator and the equipment the control shall be completely implemented in 

hardwired control systems or in PLCs. 

Where it is applicable manual and automatic operation will be provided. 

3.8.3.7. ALARM AND SWITCHING POINTS 

The alarm and switch points can be adjusted at the operator work stations of the SCADA- 

System. Permission of acces levels can be defined, to prevent unauthorised adjustement. 

Alarm and switch points within package units can only be adjusted at the local control 

panel. 

Alarms will be shown at the mimic page of the SCADA-System. Unacknowledged alarms 

are shown with flashing puls and with acoustic signal. After acknowledging, the alarms are 

shown steady and the acoustic signal stops. 

The alarm will be also printed out on the alarm printer at the Control Center. 

For restart of the pumps/drive the alarm will have to be reset. 

3.8.3.8. CONTROLLER 

All controllers will be implemented in the PLC. The set points for these controllers can be 

adjusted at the operator panel. 

If automatic control is not possible, an alarm will have to be indicated. 

3.8.3.9. DETAILED FUNCTIONAL DESCRIPTION 

3.8.3.9.1. PLC 1 PRETREATMENT 

A. Intlet structure - Flow meter measurement 

- Used materiel. 

- Function. 

Electromagnetic flowmeter for measure of inlet flow from PS8. 

Electromagnetic flowmeter for measure of inlet flow from Eastern Village. 

Continuous operation of a set of continous measurement of flow with chain 

of local inidcation and remote 





- Way of functioning. 

Instantaneous flow, totalization, default measurement chain and data 

storage 

B. Intlet structure - Flow measurement 


- Function. 

PH sensor. 

Temperature sensor. 

Local indication and transmision of pH and temperature of raw water 

values to control room 

- Automatic functioning. 

- Continuous operation 

C. Fine screening 


- Function. 

Fine screenings. (1 per channels) 

Low level (float). (1 per channels) 

Detector of blocking of the refusals. (1 per channels) 

Electronic load limiter (1 per channels) 

Screening before treatment 


Continuous operation of fine screens 

Stop on low level into each inlet channel 

Stop on demand of screenings waste block detector or electronic load 

limiter 

- Manual functioning. 

- Security. 

The start or the stop will depend only on push buttons 

Stop on low level into each fine screens 

Stop on demand of screenings waste block detector or electronic load 

limiter 

Security stop on Emergency stop button 





D. Screening conveyor 


- Function. 

Screw conveyor. 

Detector of blocking of the refusals. 

- Screening wastes transfer to the compactor 

Automatic functioning. 

- Continuous operation of the screw conveyor associated to the screenings 

operation 

Manual functioning. 

- Depends only on the corresponding on/off buttons 

Security. 

- Stop on screening wastes block detector 

- Security stop on Emergency stop button 

E. Screening compacting device 


- Function. 

Compactor 

Detector of blocking of the refusals 

Screnning waste compacting 


Continuous operation of compactor associated with screw coveyor 

operation 


- Security. 

Depends only on the corresponding on/off buttons. 

Stop on demand of electronic load limiter 

Security stop on Emergency stop button 

F. Grit and grease removal – grease removal 


Submerged turbine aerators. (3 per tanks) 

Scraper bridge. (1 per tanks) 

Low level sensor. (1 per tanks). 





- Function. 

Grease floating and extraction by surface skimming 


Automatic continuous operation of surface skimmer and aeroflots 


- Security. 

Operation and stop depend only on the corresponding on/off buttons, 

under the same conditions for the automatic operation 

- Security stop on Emergency stop button 

Stop on low level 

G. Grit and grease removal - Grit removal 


- Function. 

Grit extraction pumps. (1 per tanks + 1 standby in stock) 

Grit classifier. 

Level Switch Alarme High High (LSA HH). (1 per tanks) 

High level sensor. (1 per tanks). 


Level Switch Alarme Low Low (LSA LL). (1 per tanks) 

Grit extraction 


Automatic operation of grit extraction pumps on high level 

Automatic stop of grit extraction pumps on low level 

Automatic operation of grit classifier linked to the grit extraction pumps 

operation 

Automatic stop of the grit classifier linked to the grit extraction operation 


- Security. 



- High high alarm level 

Low level stop 

Low low level stop 





H. Grease Pit 


- Function. 

Sprinkler for grease evacuation. (1 per tanks) 

Solenoid valves on industrial water network. (1 per tanks) 

High level controller. 

Grease extraction 


Automatic operation of sprinkler valve at the end of scraper cycle 

Automatic shutting of the valves after 20 secondes ( to be defined in 

execution phase) 


- Security. 



Low level alarm (vacuum trucks evacuation) 

I. Backflow pretreatment PS 


- Function. 

Electropumps sets (1 + 1S). 

Level Switch Alarme High High (LSA HH). 



Level Switch Alarme Low Low (LSA LL). 

Backflow feedback 


Pumps operation and stop will be slaved on tank level 

Level measurement detector 

Pumps stop on low level 


- Security. 



For each pump in manual and automatic operation, stop by Emergency 

stop button 

Low level alarm 





3.8.3.9.2. PLC 2 AERATION TREATMENT 

A. Aearation tanks - ERATION TANKS - ANOXIA 


- Function. 

Submersible stirrers (2 per anoxic tanks). 

Preatreated water and mixed liquor recirculation mixed 


Stirrer continuous operation 


- Security. 

The start or the stop will depend only on push buttons, in the same 

conditions that the automatic fonctionning. 

Stop on electronic load limitor 

In automatic or manual operation, stop on local emergency stop button 

B. Aeration tanks – aerated zone 


Submersible stirrers (6 per aeration tanks). 

O2 meter (2 per tanks). 

Rh sensor (3 per tanks). 

MES sensor (1 per tanks). 

NO3 sensor (1 per tanks). 

- Function. 

Submersibles stirrers. 

- Water circulation inot the tank 

Measures of dissolved oxygen and redox potential. 

- Dissolved oxygen concentration measurement 

Measure of MES. 

- Control of sludge extraction demand (Sludge pit) 


Stirrers continuous operation 


- Security. 



In automatic or manual operation, stop on local emergency stop button 





C. Blower room 


- Function. 

Air Blower (1 per aeration tanks + 1 standby). 

Electrovannes (2 per tanks). 

Air flow measurement at the exit of air blower (1 per tanks). 

Air pressure measurement at the exit of air blower (1 per tanks). 

Temperature measurement at the exit of air blower (1 per tanks). 

Temperature measurement at the building. 

Fresh air injection fan 

Surpressed air production 


3 air blowers in service (1 per aeration tank). The fourth is on standby. The 

change is manual. The air blowers are controlled by dissolved oxygen 

measurement or redox measurement. Variable speed by modification 

paddles of air blowers 

At the air blowers stop, the solenoid valve control the valves stop 

Fresh air injection fan is controlled by on/off button and temperature 

measurement into the building. 


- Security. 



In case of default on the measurement chain, using of cycling mode 

(predefined on the automat during execution phase) 

In case of low or no flow ; high, low or no pressure ; high air outlet 

temperature, air blower stop and alarm 

For each air blower in manual and automatic operation, stop on 

emergency stop button 

D. Mixes liquor recirculation 


- Function. 

Recirculation pumps (2 per aeration tanks + 1 stand-by in stock). 

Electromagnetic flowmeter for measure of flow from recirculation (1 per 

tanks). 

Mixed liquor recirculation 






The mixed liquor recirculation pumps controls will be defined by the raw 

water inlet flow, the outlet NO3 sensor 

The electromagnetic flow meter measure the quantity of mixed liquor 

sludge recirculation. 


- Security. 



For each pump in manual and automatic operation, stop on emergency 

stop button. 

E. Degazing and distribution well - Degazing 


- Function. 

Skimmer (1 per distribution well). 

Scum evacuation to scum pit 


The control of skimmer will be carried out by cycle predefined in execution 

phase 


- Security. 

Operation and stop depend only on the corresponding on/off buttons 

For each skimmer in manual and automatic operation, stop on emergency 

stop button 

F. Degazing and distribution well – scum pit used materiel. 

Electropumps sets (1 + 1S per tanks). 

- Function. 

Agitateur immergé. (1 per tanks) 

Level Switch Alarme High High (LSA HH). (1 per tanks) 



Level Switch Alarme Low Low (LSA LL). (1 per tanks) 

Scum storage tank 


Pumps. 

Pump operation on high level 

Pump stop on low level 






- Security. 




stop button 

For each stirrer in manual and automatic operation, stop on emergency 

stop button 

high high level alarm 

Low low level alarm 

G. Secondary clarification 


- Function. 

Suction scraper bridge (1 per tanks). 

Top level of sludge sensor (1 per tanks). 

Sludge extraction and scum scrapper 


Suction scraper bridge operation and stop will be carried out by cycle 

predefined in execution phase 

The top level of sludge sensor control sludge recirculation pumps 


- Security. 




stop button 

For each stirrer in manual and automatic operation, stop on emergency 

stop button 

H. Sludge pit – Sludge recirculation 


- Function. 

Sludge recirculation pumps (3 + 1S per sludge pit). 

Electromagnetic flowmeter for measure of flow from sludge recirculation (1 

per tanks). 

Low level controller (1 per sludge pit). 

Sludge recirculation to aeration tanks 






Pumps operation or stop are slaved to the inlet raw water flow, to the top 

level of sludge sensor, or low level sensor and MES sensor of the aeration 

tanks 

The variable speed will be carried out by operation of one or more pumps 


In case of HS pump, the standby pump will be commisionned manually 


Sludge recirculation instantaneous flow measurement, totalization, default 

of chain measurement and data storage 


- Security. 



For each sludge recirculation pump in manual and automatic operation, 

stop on local emergency stop button 

I. Sludge pit – Sludge excess 


- Function. 

Sludge excess pumps (1 + 1S per sludge pit). 

Electromagnetic flowmeter for measure of flow from sludge excess (1 per 

tanks). 

Excess sludge extraction 


The excess sludge operation or stop are slaved to the MES sensor 

Excess sludge pump on low level 

In case of pump HS, the standby pump will be commisionned manually 


Excess sludge instantaneous flow measurement, totalization, default of 

chain measurement and data storage 


- Security. 



For each excess sludge pump in manual and automatic operation, stop on 

local emergency stop button 





3.8.3.9.3. PLC 3 TERTIARY TREATMENT 

A. Intermediate pumping station 


- Function. 

Electropumps sets (2 (Phase 1)+ 1(Phase2) + 1S). 

US Level Sensor. 

Level Switch Alarm Low Low (LSA LL). 

Sand filters feed 


Intermediate pumps operation and stop will be slaved to tank level 

Continuous level by US sensor 



- Security. 



For each intermediate pump in manual and automatic operation, stop on 



B. Sand filtration – filters 


- Function. 

US Level Sensor. (1 per filters) 

Butterfly motorized valves controlled by US sensor to outlet filtered water 

Settled water filtration 


Continuous level by US sensor 

Control outlet filtered water valve by filter level 

Shutting outlet filtered water valve on low low level (US sensor) 


- Security. 



High high level alarm 






C. Sand and filtration – Washing 


- Function. 

Submersibles electropumps sets (2 + 1S). 

Air blowers type roots (1 + 1S). 

Head Loss Detection. (1 per filters). 

Butterfly motorized valve to inlet wash water . (1 per filters) 

Butterfly motorized valve to inlet scour air . (1 per filters) 

Penstock to outlet wash water(1 per filters) 

Butterfly motorized valve to rinsing water 

Electromagnetic flowmeter for measure of flow from wash water. 

Electromagnetic flowmeter for measure of flow from backwash water. 

Air flow measurement for measure of flow from filter backwash air. 

Clogging filter washing 

Only one filter in washing in the same time. 


Filter clogging measurement by vacuometer 

Washing cycle operation by filter clogging measurement 

Two electropumps in duty, the third is in standby. The change is carried out 

manually 

Automatic filter washing operation as follows : 

 

 

 

 

 

 

 

 

Shutting outlet filtered water valve 

Opening outlet wash water valve 

Air blower operation and opening inlet scour air valve 

Operation first electropump and opening inlet wash water valve 

Air blower stop and shutting inlet scour air valve. 

Operation second electropump and opening high flow valve 

Electropump stop and shutting high flow filtered wash water valve 

Shutting outlet filtered wash water valve 

Instantaneous filtered wash water flow measurement, totalization, default 

of chain measurement and data storage 

Instantaneous filter wash water feedback flow measurement, totalization, 

default of chain measurement and data storage 

Instantaneous scour air flow measurement, totalization, default of chain 

measurement and data storage 






- Security. 

Eletropumps sets operation and stop depend only on the corresponding 

on/off buttons, under the same conditions for the automatic operation 

Air blowers operation and stop depend only on the corresponding on/off 

buttons, under the same conditions for the automatic operation 

High high level alarm 


D. Filters wash water pumping station 


- Function. 

Electropumps sets (2 + 1S per tanks). 

Low level controler. 

Level Switch Alarm Low Low (LSA LL). 

Filtered wash water feed 


oElectropumps operation and stop will be slaved to filters washing cycle 

Low and low low level measurement 

Electropumps stop on low level. 


- Security. 

Eletropumps sets operation and stop depend only on the corresponding 

on/off buttons, under the same conditions for the automatic operation 

oFor each pump in manual and automatic operation, stop on local 


Low low level alarm. 

E. UV Disinfection 


UV channel with 2*2 modules 

- Function. 

Filtered water disinfection 


Continuous operation 

Data transfert og UV modules 






- Security. 



For each intermediate pump in manual and automatic operation, stop on 


UV modules operation default alarm 

F. Treated effluent pumping station 


- Function. 

Electropumps sets (2 (phase 1) + 1 (phase 2) + 1S). 


High level sensor. 

Low level sensor. 


Electromagnetic flowmeter for measure of flow from treated effluent. 

Ph sensor. 

O 2 sensor. 

Temperature sensor. 

NO 3 sensor. 

Ammonium sensor. 

Treated effluent evacuation to the infiltration site 

Continuous operation of a set of continous measurement of flow with chain 

of local inidcation and remote 

Continuous analyses of treated effluent quality on retained parameters 


Electropumps operation and stop will be slaved to water level into tank 

Instantaneous treated effluent flow measurement, totalization, default of 

chain measurement and data storage. 

Low level and low low level measurements 

Electropumps stop on low level 








- Security. 

For each treated effluent pump in manual and automatic operation, stop on 



3.8.3.9.4. PLC 4 BACKFLOW PUMPING STATION 

A. Gravity thickeners 


- Scraper bridge 

- Function. 

Blocking detector 

Settling sludge 


Continuous operation 


- Security. 



For each scrapper bridge in manual and automatic operation, stop on local 


B. Thickened sludge pumping station 


- Function. 






Transfer thickened sludge to drying beds 


Pumps operation and stop will be slaved to level tank 

Level measurement by capacitives sensors 









- Security. 

For each pump in manual and automatic operation, stop on local 



C. Backflow pumping station 


- Function. 






Transfer drainage water and supernatant to pretreatment 


Pumps operation and stop will be slaved to level tank 

Level measurement by capacitives sensors 



- Security. 



For each pump in manual and automatic operation, stop on local 







3.8.3.10. INPUT/OUTPUT REQUIREMENTS 

PLC1 PRETREATMENT 

Item Description Source 

Number + 

(Spare) 

Digital Input 

Digital 

Output 

Analogue 

Input 

Analogue 

Out put 

Ph. 1 Ph.2 Ph. 1 Ph.2 Ph. 1 Ph.2 Ph. 1 Ph.2 Ph. 1 Ph.2 

1 Inlet Structure 

Flowmeter PS8 Electromagnetic 1 1 1 1 

Flowmeter Eastern Village Electromagnetic 1 1 1 1 

PH Sensor Transducer 1 1 1 1 

Temperature Sensor Transducer 1 1 1 1 

2 Fine Screening 

Screens Motor 2 3 6 9 2 3 

Low Level Switch 2 3 2 3 

Detector of blocking Switch 2 3 2 3 

Overload detector Transducer 2 3 2 3 

Screening Conveyor Motor 1 1 3 3 1 1 


Screening compacting device Motor 1 1 3 3 1 1 


Power Measurement 1 1 

3 Grit and Grease Removal 

Submerged Turbine Aerators Motor 6 9 18 27 6 9 

Scraper Bridge Motor 2 3 6 9 2 3 

Low Level Level Sensor 2 3 2 3 

Grit Extraction Pump Motor 2 3 6 9 2 3 

Grit Classifier Motor 2 3 6 9 2 3 

Alarme HH Level Switch 2 3 2 3 

High Level Level Sensor 2 3 2 3 


Alarme LL Level Switch 2 3 2 3 

Sprinkler for Grease Evacuation Motor 2 3 6 9 2 3 

Solenoid Valves Actuator 2 3 2 3 2 3 


Backflow Pretreatment PS Motor 1 1 3 1 1 1 






Allocated I/O Count 79 109 19 27 10 12 3 4 

Spare (Mimimum) 10 14 4 6 4 4 4 4 

Total I/O Count 89 23 14 7 

Total I/O Count Phase 1 & 2 123 33 16 8 





PLC2 AERATION TREATMENT 

Number + Digital Digital Analogue Analogue 


(Spare) Input Output Input Out put 


1 Aération Tanks 

Anoxic Submersible Stirrers Motor 4 6 12 18 4 6 

Aeration Submersible Stirrers Motor 12 18 36 54 12 18 

O2 Meter Transducer 4 6 4 6 

Rh Sensor Transducer 6 9 6 9 

MES Sensor Transducer 2 3 2 3 

NO3 Sensor Transducer 2 3 2 3 


2 Blower Room 

Air Blower Motor 2 + (1) 3 + (1) 9 12 3 4 

Electrovannes Actuator 4 6 4 6 4 6 

Air Flow Measurement Transducer 2 3 2 3 

Air Pressure Measurement Transducer 2 3 2 3 

Temperature Measurement Transducer 2 3 2 3 

Building Temperature Measur. Transducer 1 1 1 1 

Fans Motor 1 1 3 3 1 1 

Recirculation Pump Motor 4 6 12 18 4 6 

Recirculation Flowmeter Electromagnetic 1 1 1 1 


3 Degazing and Distribution Well 

Skimmer Motor 2 3 6 9 2 3 

Submersible pump Motor 2 + (2) 3 + (3) 12 18 4 6 

Agitator Motor 2 3 6 9 2 3 





Suction Scraper Bridge Motor 4 6 12 18 4 6 

Sludge Top Level Level Sensor 4 6 4 6 

Sludge Recirculation Pump Motor 6 + (2) 9 + (3) 24 36 8 12 

Sludge Recirculation Flowmeter Electromagnetic 2 3 2 3 


Sludge Excess Pump Motor 2 + (2) 3 + (3) 12 18 4 6 

Sludge Excess Flowmeter Electromagnetic 2 3 2 3 


4 Incoming Electrical Supply 

Incoming Supply Meters Meter 2 2 2 2 

20 kV Switchboard 18 18 

Power Measurement 2 2 2 2 

Batteries & Chargers 8 8 

5 Generator 

Connection Status 6 6 


Spare (Mimimum) 20 27 10 10 8 10 4 4 





PLC2 AERATION TREATMENT (next) 

Number 

Item Description Source + 

(Spare) 

Digital Input 

Digital 

Output 

Analogue 

Input 

Analogue 

Out put 

Total I/O Count 212 58 45 8 






PLC3 TERTIARY TREATMENT 





1 Intermediate Pumping station 


US Level Sensor Transducer 1 1 1 1 



2 Sand Filtration 

US Level Sensor Transducer 4 6 4 6 

Filtred Water Butterfly Gate Actuator 4 6 4 6 4 6 


Air Boster Motor 1 + (1) 1 + (1) 6 6 2 2 

Head Loss Detection Actuator 4 6 4 6 4 6 

Wash Water Butterfly Gate Actuator 4 6 4 6 4 6 

Air Wash Butterfly Gate Actuator 4 6 4 6 4 6 

Backwash Water Valves Actuator 4 6 4 6 4 6 

Wash Water High Flow Butterfly Gate Actuator 1 1 1 1 1 1 

Wash Water Flowmeter Electromagnetic 1 1 1 1 

Backwash Water Flowmeter Electromagnetic 1 1 1 1 

Backwash Air Flowmeter Electromagnetic 1 1 1 1 


3 Filtered wash water pumping station 




4 UV Disinfection 

UV Chanel Actuator 3 3 3 3 3 3 

5 Treated Effluent Pumping Station 






Treated Effluent Flowmeter Electromagnetic 1 1 1 1 

Ph Sensor Transducer 1 1 1 1 

O2 Sensor Transducer 1 1 1 1 

Temperature Sensor Transducer 1 1 1 1 

NO3 Sensor Transducer 1 1 1 1 

Ammonium Sensor Transducer 1 1 1 1 


6 Industrial water 2+1 2+1 9 9 3 3 


Spare (Mimimum) 10 10 4 4 8 10 4 8 





PLC3 TERTIARY TREATMENT (next) 

Number 

Item Description Source + 

(Spare) 

Digital 

Input 

Digital 

Output 

Analogue 

Input 

Analogue 

Out put 

Total I/O Count Phase 1 59 18 49 29 






PLC4 BLAKFLOW PUMPING STATION 





1 Gravity Thickeners 

Bridge Motor 2 3 6 9 2 3 

Detector of Blocking Switch 2 3 2 3 


2 Thickened Sludge Pumping station 







3 Blackflow Pumping Station 








Spare (Mimimum) 6 6 4 4 4 4 2 2 

Total I/O Count Phase 1 34 10 7 2 






3.9. ELECTRICAL EQUIPMENT 

Electrical works include arranging both main and a spare power supply for the wastewater 

treatment plant. 

3.9.1. POWER SUPPLY 

According to Gaza Electricity Distribution Company (GEDCO), the area of KYWWTP can 

be provided with electricity through the electrical line MT/(22kv) which is parallel to Salah 

Eden street. The distance from this electrical line to the WWTP is 2,630 m. The electrical 

connection point (ECP) with this electrical line is illustrated in Figure n°3. 

Fig. 3. POWER SUPPLY TO KY WWTP SITE-POINT OF ELECTRICITY CONNECTION 

The electrical connection between KY WWTP and the point (ECP) on the electrical line 

MT/(22kv) mentioned above will be constructed under this project in a separate package. 

This electrical connection consist of the following equipment: 





A. Poles 

- Steel pole 12m long of stop type. 

- Steel pole 12m long of line type 

- Steel base for the pole. 

- Steel arm for pole (stop). 

- Steel arm for pole ( line). 

- 24 kv insulator and Pin. 

B. Foundation 

- Concrete foundation B 250 for stop type Pole ( 5,5m3). 

- Concrete foundation B 250 for the line pole 1 ( 3m3 ). 

C. Wires (line length 2550m) 

- Copper wires of 50mm2 conductor. 

- 18/30 KV under ground single core copper cable 1x50mm2 for transformer. 

- 36 kv Indoor termination kit for single core copper cable 1x50mn2. 

- -36 kv isolating switch with built in arc Interrupter 

D. Steel Bolts 

Different sizes of Bolts for fixation the different elements (like arms, Insulators, steel base, 

etc). Surge arrestor 24 KV and earthling Rod. 

3.9.2. REQUIRED POWER FOR KYWWTP 

Electrical power is needed in KY WWTP for operating and lightening, the required power 

for each component in KY WWTP is summarized in the following table: 





PRE-TREATMENT 

Item 

No. 

Description 

Phase I Phase II Notes 

unit kw/u Total kw 

1 Fine Screens 1 1,1 1,1 

2 Screenings conveyor 1 1,1 1,1 

3 Screenings Compacting device 1 3,0 3 

4 Aeration devices for degreasing 9 1,5 13,5 

5 Scraper bridges 3 0,37 1,11 

6 Grit extraction Pumps(3+1 standby 

1stock) 3 2,2 6,6 

7 Grit classifier 1 1,1 1,1 

8 Back flow Ps from Pretreatment 

installation 

* Submerged Electropump Sets 

(1+1stand by 1 1 1 

* Lighting (inside pretreat) 1 6 6 

Total Power 34,5 

AERATION TANKS 

Item 

No. 

Description 

1 Anoxic stirrers 


unit kw/u Total kw unit kw/u Total kw 

* Submersible stirrers 4 7 28 2 7 14 1 Pump.st.by 

2 Aeration Zone 

* Submersible stirrers 12 6,5 78 6 6,5 39 

3 Mixed Liquor Recircul 

Recirculation Pumps 4 35 140 2 35 70 1 stock 

4 Air Production for A.T 

* Air Pzoduction (Comp) 2 630 1260 1 630 630 1 stand by 

5 Lighting of sand filter set 3 3 set 1,5 1,5 

Total 1509 754,5 

Total electrical power for phase I and II 

2263 Kw 





CLARIFICATION TANKS 

Item 

No. 

Description 



1 Degazing-Distribution -Scum 

* Longitudinal skimmers 2 0,37 0,74 1 0,4 0,37 

2 Scum pit 

* 2 Submerged Electro pump set(1+1 

Standby) 

2 1,2 2,4 1 1,2 1,2 

* Submerged stirrer 2 1,5 3 1 1,5 1,5 

3 * Suction scraper bridge 4 0,55 2,2 2 0,6 1,1 

4 

* Sludge Recirclation pumps 

(3+1Standby) 

3x2 9 54 3 9 27 

5 Excess sludge Extraction 

Sludge recirculation 

( Pumps (1+1 stand by) 2 3,1 6,2 1 3,1 3,1 

6 Lighting outside building set set 2,6 2,6 1 1,3 

Total Power 71,14 35,57 

Total Power for phase I and II 107 





SAND FILTRATION 

Item 

No. 

Description 

1 Inlet pumping station 


(2+1(Extension)+1 stand by 



2 40 80 1 40 40 1 Pump.st.by 

2 Filters 

* Motorised butter fly Valve 4 0,5 2 

* Motorised butter fly Valve 4 0,5 2 

* Motorised butter fly Valve cont 4 0,5 2 

* Motorised butter Penstocks 4 0,5 2 

3 Filter Washing 


(2+1stand by 

2 22 35 

* Blowers (1+1 stand by) 1 55 42,9 

4 Filter Wash water feed back system 

* Submerged electropump sets (1+1 

standby) 

1 5,9 5,9 

5 UV Disin Fection + Compressor set 1 20 1 30 30 

6 Industrial Water 

* Variable speed booster 

Consist electropumps (2+1 Standby) 2 7,5 15 

7 Treated Effluent outlet Pumping station 

* Submerged electropump sets (3+1 

standby) 

3 250 750 1 250 250 1 Pump.st.by 

8 Lighting of sand filter set 5 

Total Power 978 320 

Total Power 

1300 Kw 





SLUDGE TREATMENT 

Item 

No. 

Description 



1 Thickened Sludge 

Pumping station 

* 2 electropump sets (1+1 standby 1 22 22 1 stand by 

2 Backflow Pumping station 

* 2 Submerged electropump sets(1+1 

standby) 

1 5,9 6,7 1 stand by 

3 Lighting 1 

Total Power 

30kw 

3.9.3. MAIN POWER SUBSTATIONS AND SWITCHGEARS 

Two substations shall be installed inside The WWTP, the first substation is located beside 

the blowers house (2000 KVA /22KV/ 0.4KV), and the second one is located beside the 

sand filter (1600 KVA /22KV/ 0.4KV). the substations shall be ventilated with AC units and 

contains the following equipments: 

A. Substation No 1 (Beside the sand filters) 

- (SF6) 24 KV/630A switch gear and 16KA short circuit current Ring main unit SF6 

incoming switch disconnections, and one transformer protection equipped with 

circuit breaker GAS type combination (CTTC). 

- Transformer: substation No 1 contains two transformers as follows : 

Transformer T1 = 1250KVA/22KV for supply of the electrical power for the 

following components: 

Item 

No. 

Description U KW/U Tot kw Tot KVA Notes 

1 * Inlet pumping station 2 40 80 94 

2 * filters motorized butterfly valves 16 0,5 8 9,4 

3 * Filter mashing 

a) Submerged electro pumps 2 22 44 51 

b) Blower 1 55 55 64 

4 * Filter wash water feed back up 

a) Submerged electropump 1 5,9 6 7 





b) UV disinfection set 20 20 23 

5 * Tndustrial water Electropump 2 7,5 15 17 

6 * Treated effluent outlet 250 294 

7 *Submerged electropump 3 250 750 882 

Total Power (KVA) 1147,4 

Transformer T2 = 630KVA/22KV for supply of the electrical power for the 


Item 

No. 

Description Phase I Phase II Notes 

KW KVA KW KVA 

1 Administration 34 40 

2 Work shop 30 35 

3 External lighting 18 21 

4 Clarifiers (Phase I ) 71 83 

5 Clarifiers (Phase I I) 

6 Pretreatment 34,5 40 

7 Gravity thickeners (No1,2+3) 30 35 

8 Sand filter - Phase II 

a) Submerged electropump 40 47 

b) UV disinfection + Compressor 30 35 

c) Treated effluent outlet 250 294 

Total Power 254 417 

Total Power (KVA) for phase I and II 

Taking 0.85 Coefficient of usage between 

the buildings. 

671 KAV 

672x0.85=570 KAV 

- M.D.B/T1 (Main distribution Board): connected by cable from transformer to 

M.D.B/T1 with cable u 1000V- 2( 3x300mm2) + (1 x 300mm2) (one core cable ) 



B. Substation No 2 (Beside the blowers house) 

- (SF6) 24 KV/630A switch gear and 16KA short circuit current Ring main unit SF6 

incoming switch disconnections, and one transformer protection equipped with 

circuit breaker GAS type combination (CTTC). 





- Transformer: substation No 2 contains two transformers as follows : 

Transformer T3 = 1250KVA/22KV for Supply of the electrical power for two 

roots type Blowers as follows : 

Item 

No. 

Description U KW/U Tot kw Tot KVA Notes 

1 * Air production for areation tanks 

a) Compressor, AERZEN type 

(consumption power) 

b) Compressor, AERZEN type 

(consumption power) (effeciency 

=70%) 

c) Control Panel outomatic regulation 

system 

Total power 

2 581 1 260 683,53 

2 407 1 260 478,82 

2 10 20 11,765 

1174 KVA 

Transformer T4 = 1250KVA/22KV for Supply of the electrical power for the 


Item 

No. 

Description 


U KW/U T/kw U kw/u T/kw 

1 *Air production for areation tank 

a) Compressor, AERZEN type 1 581 581 

b) Control Panel (LC) 1 10 10 

2 *Anoxic stirrers Submersible Stirrers 4 7 28 2 7 14 

3 * Areation Zone Submersible Stirrers 12 6,5 78 6 6,5 39 

4 * Mixed liquor Recirculation 

Recirculation Pump 4 35 140 2 35 70 

5 *Lighting of Areation Tanks set 3 3 set 1,5 1,5 

Total Power 249 715,5 

Total Power for phase I and II 

Total Power for phase I and II 

964.5 Kw 

1135 KVA 


M.D.B/T3 with cable u 1000V- 3 (3x300mm2) + (2 x 240mm2) (one core cable ) 



The switchgear with starters and Feeders for blowers, mixers, secondary sedimentation 

and related pumps were installed at M.D.B. The switchgear with starters and feeders for 

inlet, screening, grit removal and primary sedimentation were located at secondary 

distribution board that were located inside or beside each building. 





3.9.4. ELECTRICAL GENERATORS: 

The plant shall be equipped with two stand-by generators, they are located beside the 

sand filters. The first generator has a rating power of 1100 Kw (1375KVA), it will feed the 

sand filters, clarification tanks, gravity thickeners, administration building, and the 

workshop. The second one has a rating power of 1500 Kw (1875 KVA), it will feed the 

aeration tanks and the blowers. In case of power interruption, an Automatic Transfer 

Switch (ATS) at the main distribution board shall be automatically switched from 

transformer to generator. Underground fuel tank of 50m3 volume shall be constructed 

beside the generators. The fuel tank will be sufficient for 72 hours (8 hours/day for 9days) 

since the first generator consumes 291 l/hr, and the second one consumes 397 l/hr. 

3.9.5. LIGHTENING: 

lightening shall be provided for each building (local lightening) as well as for the WWTP 

(external lightening). Weatherproof lighting fitting shall be selected to resist the out door 

climate condition. Buildings inside shall be equipped with fluorescent lights. Security 

lighting fittings shall be provided and fixed all around the boundary wall to illuminate the 

area, and to ensure safe property. The fittings shall be street lighting type, utilizing – SON- 

T lamps. 

3.9.6. EARTHING: 

An insulated galvanized steel Tape 34 mm x 4mm shall be used to connect all HV and LV 

distribution board with isolating cables 1x50 to 1x150 mm. 

The LV neutral Resistance to earth shall not exceed 4 ohm and shall be separated from 

H.V. metal work. electrode diameter shall not less than 19 mm diameter Copper or Copper 

clad steel Provided with hard end tips and Driving Caps. 

Earth leads and earth tapes shall be of high conductivity bare copper in internal dry 

conditions and where they are run underground or in damp locations they shall be tinned. 

As far as possible they shall be continuous without joints, but where joints are un 

avoidable, they shall be bolted and soldered. All such joints shall be coated with anticorrosive 

paint and wrapped with self – adhesive PVC tape. 

3.10. CIVIL WORKS 

Civil works cover the wastewater treatment units, pipes and chambers, pumping stations, 

sludge treatment units, and the buildings for administration, blowers, and workshop. 

Construction material is reinforced concrete. Floors and interior walls of the facilities for 

the process units will be painted with epoxy that is resistant and sustainable against waste 

water (Fosroc Epoxy type Nitocote ET 402 or equivalent, a coal tar entended epoxy resin 

coating). Ceramic tiles will be applied for floors in the administration building. Walls of the 

rooms for personnel and administration will be plastered or smoothened and painted with 

acrylic latex paint. The buildings will be facilitated with mechanical ventilation, and the 

pumping stations to be naturally ventilated. Basins will be equipped with metal handrails 

and service platforms. Service metallic structures (grating, handrails, covers and stairs) will 





be from aluminium or hot galvanized iron for heavy pieces, meanwhile, processing devices 

(screens, scrapers, etc. ) will be made from 316 Stainless Steel. 

Soil investigation has been performed in KY WWTP site, and includes field study and 

laboratory tests. The field study includes drilling of Thirteen (13) boreholes up to a depth of 

(25) meters depth using a rotary air drilling machine provided with auger of 40 cm 

diameter. Samples representing different soil layers were collected, examined, labelled 

and sealed at the site then sent to the Material & Soil laboratory. The soil logs of each bore 

hole and the water table were recorded. 

Also (5) standard penetration tests (SPT) tests were performed according to ASTM D1586- 

67(1974)”Penetration Test & Split Barrel sampling of Soil” up to (15) m depth at 1.5m 

intervals. 

Representative samples of the soil layers were tested to determine the physical, 

mechanical and chemical properties of the ground materials. The following tests were 

performed according to the American Society for testing and Materials (ASTM) and the 

British Standards (B.S.): 

1. Natural Water Content .................................................Test.ASTM D 2216-92 

2. Grain Size Analysis by Sieves...................................... ASTM D 422-92. 

3. Liquid and Plastic Limits and Plasticity Index............... ASTM D 4318- 

4. Field unit weight............................................................ ASTM D2937 

5. Unconfined Compressive Strength............................... ASTM D2166 

6. Permeability test – Constant &Falling Head................. ASTM D2434 

7. Consolidation test ........................................................ASTM D2435 

8. Direct shear test............................................................ ASTM D3080 

9. Modified Compaction Test............................................ ASTM D 1550 

For more details refer to Appendix 8 (soil investigation report). 

All foundations design based on net allowable soil bearing capacity of 100 Kpa at minimum 

depth of 1.50m below ground surface . The cohesion for clay layer is c= 25kpa and angle 

of internal friction is 20 degrees. Excavated area below foundation in the WWTP shall be 

re-backfilled by two compacted layers 0.2 thick for each of a coarse gravelly calcareous 

sand (Kurkar) of minimum density of 18KN/m3 and min CBR=30% compacted to not less 

than 98% of it is maximum dry density of modified proctor test. No liquefaction problem is 

expected due to the far distance of the water table from the foundation level. Gaza area is 

free of any noticeable seismic activities. 

3.10.1. GENERAL PRINCIPLES AND DESIGN CRITERIA 

This section provides general structural design guidance for concrete buildings including 

foundations for the various components of Khan Younis Waste Water Treatment Plant 

(KYWWTP). The design requirements provided herein, or cited by reference, are based on 

international building codes, industry standards, and technical manuals developed. 

Instructions necessary to provide serviceable buildings and to assure load path integrity 

and continuity are included. 





3.10.1.1. CODES 

The design and specification of all work will comply with all applicable laws, regulations, 

local codes and ordinances, and with the codes and industry standards referenced herein. 

The following is a summary of specific codes and industry standards and the general 

design criteria that used in the concrete structural design and construction of KY WWTP. 

1. Design & placement of structural concrete building based on American Concrete 

Institute Building Code Requirements for Reinforced Concrete ACI 318-05. 

2. Design and placement of concrete for liquid containment structures at KY- WWTP 

intended for conveying, storing, or treating water, wastewater, or other non-hazardous 

liquids, and for secondary containment of hazardous liquids followed Code 

requirements for American Concrete Institute Environmental Engineering Concrete 

Structures Report of Committee 350 (ACI 350R-06) in addition to the requirements of 

ACI 318. These features include tanks, reservoirs, wet wells, pump stations, and other 

similar structures and appurtenances. The main purpose of ACI Committee 350 

Report is to minimize cracking in order to avoid leakage of chemicals and wastewater 

3. The guidelines given by regional and internationally recognized building codes 

concerning applied loads, e.g. dead, live, wind and seismic loads, properties and 

specifications for construction materials and other construction requirements 

considered in the structural design. The load calculation is to be based on the 

requirements of ASCE/SEI 7-05 (copyright 2006). 

In addition, acceptable and proper local construction practices will also been observed in 

the design and in determining the construction requirements for this project. 

3.10.1.2. DESIGN APPROACH FOR CONCRETE STRUCTURES PROTECTING THE ENVIRONMENT 

The design approach for concrete structures protecting the environment is: 

- In accordance with the ACI Committee 350 Report, the design strength required 

by the ACI 318 load factor equations is to be multiplied by a sanitary coefficient. 

The sanitary coefficient increased the design loads to provide a more conservative 

design with less cracking. The increased required strength is given by: 

Required strength = Sanitary coefficient x U 

Where the sanitary coefficient equals: 

1.3 for flexure 

1.65 for direct tension 

1.3 for shear beyond that of the capacity provided by the Concrete. 

- The purpose of the sanitary coefficient is to reduce reinforcing steel stresses (and 

cracking potential) at service load conditions. 

- Small diameter bars at close spacing are encouraged in order to limit crack widths. 





- Cover requirements greater than those of ACI 318 are required to provide 

increased protection against reinforcing steel corrosion (minimum steel cover at 

least 5cm for foundation and surfaces in contact with water and 3cm for other 

surfaces). 

- Information on joints, joint details, and water stops are also covered in the ACI 

Committee 350 Report. 

3.10.1.3. STRUCTURAL DESIGN REQUIREMENTS 

The following design requirements are applicable to the design of structures in addition to 

the requirements of the design codes and standards specified herein. 

3.10.1.3.1. STRUCTURAL ANALYSIS: 

1. The method of analysis 

The method of analysis was appropriate for the design conditions. Calculations includes 

sufficient diagrams and sketches to explain the framing systems and illustrate all loading 

conditions. This is particularly important with computer generated calculations. 

2. 2DFEM analysis 

Finite Element Analysis is a simulation technique which evaluates the behaviour of 

components, equipment and structures for various loading conditions including applied 

forces, pressures and temperatures. 

The consultant used finite element techniques (2D modelling) in analyzing and designing 

most of the civil component in the Khan Younis waste water treatment plant. 

3. Computer software 

- STAAD PRO, SAP2000, and other computer programs was used in this project for 

the analysis and design of various structural elements. Regardless of the 

computer program used, all members will be designed based on ACI 318-05 and 

ACI 350-06. The computer output was checked using hand calculations. 

- 2D structural analysis and design including design optimization was used in this 

project when it is required. 

- Excel computer software was used for calculate of different structural elements. 

3.10.1.3.2. DEFLECTION LIMITS AND MINIMUM DEPTH: 

Cast-in-place concrete framing members will be at least as deep as indicated in the Table 

below Deflections will not exceed values listed in ACI 318. 

Member 

Simple Support 

Minimum 

Thickness 

One End Fixed 

Minimum 

Thickness 

Both Ends Fixed 

Minimum Thickness 

Cantilever 

Minimum 

Thickness 

One way 

Solid Slab 

L/20 L/24 L/28 L/10 

Beam L/16 L/18.5 L/21 L/8 





3.10.1.3.3. CONCRETE DESIGN: 

All concrete structures was considered as reinforced concrete structures and is designed in 

accordance with ACI 318 and as further specified herein. Liquid containment structures will 

additionally comply with the requirements of ACI 350R. 

General Requirements: 

- Concrete design is based on the strength design method. Load factors for the 

strength design method is in accordance with the following requirements in 

addition to the prescribed loading combinations of the governing building code. 

Additional load factors is applicable in liquid containment structures. 

U=1.4(D+F)................................................................... (ACI 9-1) 

U=1.2D+1.6L ................................................................ (ACI 9-2) 

U=1.2D +I.6 (Lr) + (1.0L or 0.8 W) ............................... (ACI 9-3) 

U=1.2D + l.6W+ l.0L+0.5(Lr) ........................................ (ACI 9-4) 

U= 0.9D +1.6W + 1.6H................................................. (ACI 9-6) 

U=0.9D+1.0E+1.6H ...................................................... (ACI 9-7) 

D = Dead Load E = Seismic Load 

L = Live Load H = Lateral Earth Pressure 

W = Wind Load F = Lateral Fluid Pressure 

- Walls have at least 10" [250 mm] thick and footings have at least 12" [300 mm] 

thick. 

- Concrete beams have continuous top reinforcement equal to at least 20 % of the 

bottom reinforcement. Over supports where positive moment is not indicated by 

analysis, bottom beam reinforcement is lapped at least 12" [300mm]. 

- Design for Flexure: Minimum flexural reinforcement was as required by the 

referenced codes and standards. Design for crack control was satisfy the 

provisions of ACI 224. 

- Design for Shear: Reinforced concrete members was proportioned such that the 

applied shear (Vu) is less than the combined shear capacity of the concrete (Vc) 

and the shear reinforcing (Vs). 

- Liquid Containment Structures: Controlling and minimizing cracking is essential to 

the function of liquid containment structures. Concrete in liquid containment 

structures was designed in accordance with the previous requirements and 

supplemented by the following additional requirements: 

 

 

 

Reinforcement tensile stresses was kept as low as practical. 

Smaller diameter bars at closer spacing are preferred over larger bars 

spaced further apart. 

Concrete joint and placement sequencing was indicated on the construction 

drawings and in the specifications. 





 

Load factors for liquid containment structures was the load factors previously 

indicated modified as follows: 

In calculations for tension reinforcement in flexure, the required strength 

(U) will be U = 1.3 U. 

 

 

In calculations for reinforcement in direct tension, the required strength 

(U) will be U = 1.65 U. 

In calculations for reinforcement in diagonal tension (shear), the required 

strength provided by reinforcing steel (Vs) was 1.3 times the excess of 

applied shear (Vn), less shear carried by the concrete (Vc). 

Vs = 1.3 (Vn - Vc) 

Where Vs is the design capacity of the shear reinforcement. 

3.10.1.3.4. DESIGN STRENGTHS 

Concrete strengths for various applications and various exposures are listed in the 

following table. 

Usage Minimum 

Concrete fills. 

Encasements for utility lines and ducts. 

Foundation walls, footings and cast-in-place 

concrete piles 

Slabs on grade 

Reinforced concrete buildings 

Walls or floors subjected to severe exposure 

Strength 

15 Mpa 

20 Mpa 

25 Mpa 

25 Mpa 

25 Mpa 

30 Mpa 

The design cylinder concrete strength (fc =0.8 fcu) was considered in the design. The 

required coverage concrete strength was assumed to be equal to the specified concrete 

strength pluses 50 Mpa to account for variation in concrete results. 

It is recommended that the cement type "V" Sulfate Resistant Cement or Ordinary Portland 

cement with 10% coal ash to be used for construction of the foundations, to prevent 

corrosive action of the surrounding environments. The concrete mix shall be designed as 

dense as possible to prevent chemical attacks due to its low permeability. In addition; a 

plastic film (150 micron thick) shall be laid below foundations. The sides of the foundations 

and other structural members buried below the ground shall be painted with two coats of 

bitumen to avoid any attack due to infiltration of subsurface water. 

Grade 60 deformed steel bars of fy = 400MPa was used as main reinforcement. Minimum 

steel diameter of 8mm was used for all main reinforcement including stirrups. 

3.10.1.3.5. DETAILING REQUIREMENTS 

Details and detailing of concrete reinforcement was conformed to ACI 315, "Details and 

Detailing of Concrete Reinforcement". Engineering and placing drawings for reinforced 

concrete structures was conformed to ACI 315R, "Manual of Engineering and Placing 

Drawings for Reinforced Structures". 





3.10.1.4. STRENGTH AND SERVICEABILITY PERFORMANCE OBJECTIVES 

3.10.1.4.1. STRENGTH 

Buildings and other structures, and all parts thereof, was designed to support safely the 

loads and load combinations indicated above. 

3.10.1.4.2. SERVICEABILITY 

Structural systems and members thereof was designed to have adequate stiffness to limit 

deflections, lateral drift, vibration, or any other deformations that adversely affect the 

intended use and performance of the building. Building designs considered deformation 

loads such as temperature, differential settlement, creep, and shrinkage. Measures 

necessary to keep buildings free from deformation load cracking and deterioration, such as 

crack control joints, was considered as an essential part of the building design. In addition 

buildings, when necessary, was capable of withstanding severe environmental effects 

without incurring damage or deterioration that would reduce the building's service life. 

3.10.1.4.3. DEFLECTION AND DRIFT LIMITS 

Deflections of structural members was not greater than allowed by the applicable material 

standard (ACI, AISC, etc.). Deflection limits are needed to restrict damage to ceilings, 

partitions, and other fragile non-structural elements. 

3.10.1.4.4. DURABILITY 

Durability of Portland cement concrete is defined as its ability to resist weathering action, 

chemical attack, abrasion, or any other process of deterioration. Causes of concrete 

deterioration, such as freezing and thawing, aggressive chemical exposure, abrasion, 

corrosion of steel and other materials embedded in concrete, and chemical reactions of 

aggregates are described in the ACI Committee 201 Report, "Guide to Durable Concrete". 

This report, which was adopted in this project, also covers various preventive measures to 

assure durability problems do not occur. 

3.10.1.4.5. CRACK CONTROL 

Cracks indicate a major structural problem, or a serviceability problem. A discussion of the 

factors that cause cracking in concrete and measures that can be used to control cracking 

are provided in the ACI Committee 224-01 Report, "Control of Cracking in Concrete 

Structures." This report was adopted in this project. Cracking was controlled by providing 

adequate temperature and shrinkage reinforcement, by reducing steel stresses at service 

load conditions, and by reducing restraint through the use of joints. 

Crack widths must be minimized in walls to prevent leakage and corrosion of 

reinforcement. ACI 350-06 provide a criterion for flexural crack width 

Z 

= 

f 

3 

s 

d 

c 

A 

where, 





z = quantity limiting distribution of flexural reinforcement. 

fs= calculated stress in reinforcement at service loads, ksi. 

dc= thickness of concrete cover measured from extreme tension fiber to center of bar 

located closest thereto, in. 

A = effective tension area of concrete surrounding the flexural tension reinforcement 

having the same centroid as that reinforcement, divided by the number of bars, sq in. 

ACI 3 18-89 does not allow z to exceed 175 kips/in. for interior exposure and 145 kips/in. 

for exterior exposure. These values of z correspond to crack widths of 0.016 in. and 0.013 

in.,respectively. ACI 350 has stricter requirements. The limiting value of z specified in ACI 

350 is 115 kips/in. For severe environmental exposures, the quantity z should not exceed 

95 kips/in. 

3.10.1.5. STABILITY 

The building foundation was capable of safely transferring all vertical and horizontal forces, 

due to specified design load combinations, to the supporting soil. The mechanism used for 

the transmission of horizontal forces may be friction between the bottom of the footing and 

ground, friction between the floor slab and the ground, and /or lateral resistance of soil 

against vertical surfaces of grade beams, basement walls, footings, piles, or pile caps. Net 

upward forces on footings and piles, which must be resisted to prevent overturning and/or 

flotation, was considered in the foundation design. 

Moreover, Environmental structures as wastewater treatment plants are frequently sited in 

areas subject to stream flooding and high ground water tables, where hydrostatic uplift 

pressures can significantly reduce the overall stability of the structure. This is not the case 

in KY WWTP as the flooding plan for the project site shows that flood does not occurred 

before. 

3.10.1.6. SELECTION STRUCTURAL SYSTEM 

The goals in the selection of a load resisting system are simplicity in the structural framing 

layout and symmetry in the structural system reaction to design loadings. The selections 

considered the need for economy, function, and reliability. 

Two structural systems was used to resist gravity and lateral loads. (1) A simple structural 

system used to resist gravity loads. In this system one-way slabs rest over continuous 

beams that were simply supported on columns. The columns and the walls transmitted 

their loads to the foundation. (2) Concrete moment frame used to resist lateral loads due to 

wind or seismic forces. 

3.10.1.7. FOUNDATION DESIGN 

Foundation design is critical to control cracking and maintenance of liquid tightness in 

liquid-containing structures. Differential movements can cause cracking in structures, 

failure of joints, and failure of rigid pipe connections, or damage to operating equipment. 





3.10.1.7.1. ALLOWABLE BEARING PRESSURES 

Allowable bearing pressures is 100kPa at a minimum depth of 1.5m below ground surface 

(according to soil investigation report). Raft foundation is used for the aeration tanks, 

clarification tanks, thickener tanks, and sand filters, while strip footing is used for the pretreatment 

building and the mixing area walls. The isolated footing is used for the 

administration building, workshop and blowers room. To avoid the negative effects of nonhomogeneousness 

of soil and to improve soil drainage parameters, it is recommended to 

perform soil improvement through re-backfilling of 40cm Kurkar under the footings level. 

3.10.1.7.2. LATERAL SLIDING & OVERTURNING RESISTANCE 

The resistance of footings to lateral sliding was calculated by combining shear frictional 

resistance and lateral soil resistance. Sliding and overturning can occur to environmental 

structures and to individual components of environmental structures due to unbalanced soil 

conditions, unbalanced liquid levels, wind or earthquake effects. 

3.10.1.7.3. DESIGN 

Footings are designed in a manner so that the allowable bearing capacity of the soil is not 

exceeded 100 Kpa. The total and differential settlements for the foundations designed and 

constructed in accordance with the recommendation of settlement limits given in the soil 

investigation report which is less than the allowable limiting values of 75mm and 19mm for 

total and differential settlements respectively, Design also meets the requirements of ACI 

318. To increase the foundation stability toward lateral forces effects and to reduce the 

differential settlements, tie beams (ground beams) are used to interconnect the Individual 

spread footings . 

3.10.1.7.4. FOUNDATIONS FOR MACHINERY: 

Commonly used machines such as centrifugal pumps, fans, centrifuges, blowers, 

generator engines and compressors have vibration characteristics that can be damaging to 

foundations. The design of foundations supporting these types of equipment requires 

special consideration to assure the equipment and foundations supporting the equipments 

is not damaged due to resonant vibration. Information and references pertaining to the 

design of foundations for vibratory loads are the ACI Committee 350 Report, 

"Environmental Engineering Concrete Structures". Additional information can be found in 

ACI Committee 351 Report, "Foundations for Static Equipment". 

3.10.1.7.5. SOIL LIQUEFACTION: 

Because liquefaction only occurs in saturated and loose cohesionless soil and due to the 

farness of the water table from the foundation level, no liquefaction problem is expected 

since the soil in KY WWTP is cohesion soil (clay). 

3.10.1.7.6. FOUNDATION PROTECTION: 

Regarding to foundation protection and water proofing, the source of water that may affect 

the building is mainly surface storm water. No ground water is expected to exist within the 

zone of influence of the foundations. Isolation of subsoil elements against adverse 

environmental factors shall be provided in the project using conventional isolation 

materials. In this regards, an efficient surface drainage is recommended such that 

rainwater is diverted away from the building edges. This can be achieved by sloping 





(preferably paving) the adjoining ground away from the building edges, and providing 

drainage ditches to take the water to lower ground (street). The Drainage system used for 

KY WWTP was by conveying the water through buried pipes and channels to drainage 

boreholes that transfer the water to the ground water. 

Protection for foundations is carried out by isolating the exposed surfaces with special 

coatings. 

3.10.1.8. SLAB-ON-GRADE DESIGN REQUIREMENTS 

Slabs-on-grade was designed for bending stresses due to uniform loads and concentrated 

loads and for in-plane stresses due to drying shrinkage and sub grade drag resistance. 

Cracking, warping, and curling can impair slab-on-grade serviceability. These problems are 

directly attributable to drying shrinkage. Cracking was controlled by minimizing drying 

shrinkage, by providing adequate crack control and isolation joints, and through the use of 

reinforcing steel. Water penetrating the slab is a common serviceability problem that can 

be cured by proper drainage system. 

3.10.1.9. STRUCTURAL MATERIALS SPECIFICATIONS 

Concrete: 

Reinforcing: 

Stainless Steel: 

15 Mpa - Concrete fills. 

20 Mpa - Encasements for utility lines and ducts. 

25 Mpa - Foundation walls, footings and cast-in-place concrete 

piles. 

25 Mpa - Slabs on grade. 

25 Mpa - Reinforced concrete buildings 

30 Mpa - Walls or floors subjected to severe exposure 

400 Mpa ( 60,000 Psi) -Grade 60 - all applications. 

Type 316 L - processing devices 

Masonry: Normal weight (Plaster thickness is 2.0cm)(strength of 35 kg/cm 2 ) 

Water stops: 

New Construction - PVC MWH standard shapes 

Concrete joints at new structure/existing pipes - 

3.10.2. WORKSHOP 

Workshop is located in a one floor with a reinforced column-beam frame structure. The 

building will be located in the current ground level. The area of the building is 216m2 and 

the clear height is 5m. The used footings are isolated and the foundation level is 2m below 

the ground surface. The building will be facilitated with lifting and transfer equipment and 

tools needed for service and repair works. 

The finishing works in the workshop was indicated in the following table: 





No. Place Finishing Doors Windows 

1 Work Shop Floors & Skirting: 

Fair Face Concrete 

Walls: 

Super creel paint 

All height 

Roof: 

Policed Paint 

- Two Galvanized 

Steel Doors 

( rolled) Ds1 

- One leaf Galvanized 

steel Door ( Ds2) 

Ten Aluminum 

Windows with 

mosquito wire mesh 

(W1) 

3.10.3. OFFICES BUILDING 

An administration building consist of 2 floors with an area of 295m2 will be implemented. 

Load bearing structures are made by reinforced concrete. Bricks are used for the other 

walls. Facades to be of plastered concrete or bricks. Construction of the buildings shall 

include adequate HVAC (Heating, Ventilating, and Air Conditioning) and plumbing works. 

The structural system used in the administration building is one-way ribbed slabs rest over 

continuous beams that were supported on columns. The columns and the walls transmitted 

their loads to the foundation. The used footings are isolated and the foundation level is 2m 

below the ground surface 

Metal doors and windows shall be installed. Concrete is the material for the stairs inside 

the building and the floors shall be paved with ceramic floor tiles. 

The first floor contains the following units: 

- Entrance hall. 

- Guard. 

- Praying room 

- Microscope room 

- Laboratory. 

- Chemical storage 

- Clean locker room 

- Dirty locker room 

- Showers 

- Stair. 

Where the second floor contains the following units 

- Entrance hall. 





- Meeting room. 

- Offices (2). 

- Secretary 

- Copy paper storage. 

- Room for breaks. 

- Control room 

- Server room 

- Break room 

- Stair. 





The finishing works in the building was indicated in the following table: 


FIRST FLOOR 

1 Entrance hall 

& Information 

Floors & Skirting: 

Non sliding Porcelain 

Tiles 

Walls: 

Oil Paint ( 1.60m) 


above 

Multi lock (DMLT1) 

Entrance Door 

(two leaves) 

Two Aluminum 

Windows with 


(W1) and steel 

protection 

Furniture & 

Equipments 

- Information wooden 

counter 

( L shape) 

- chairs 


Policed Paint 

2 Corridor Floors & Skirting: 


Tiles 

Walls: 



above 

Steel Door ( Ds2) 

(two leaves) 


Policed Paint 

3 Guard room Floors & Skirting: 

Mosaic Tiles with marble 

chips 

Walls: 


Super creel Paint 

above 

Wooden door (Dw1) 

(One leaf) and 

Steel Door ( Ds3) 

(One leaf) 

Four Aluminum 

Windows with 



protection 

Office Table , chair & 

bed 


Policed Paint 

4 Praying room Floors & Skirting: 


chips 

Walls: 



above 


(One leaf) 

Two Aluminum 

Windows with 



protection 

Carpet 


Policed Paint 

5 Microscope 

room 



chips 

Walls: 

Glazed ceramic Tiles all 

height 


Policed Paint 


(two leaves) 

Six Aluminum 

Windows with 



protection 

- L shape Marble 

cupboards 

(90cm height & 60cm 

width) 

with aluminum doors 

and granite top 

surface ( oriz eye) 

- Chairs 






6 Laboratory Floors & Skirting: 


Tiles 

Walls: 

Glazed Porcelain 

Tiles all height 


Door (two leaves) 

Nine Aluminum 

Windows with 



protection 

Furniture & 

Equipments 

- U shape Marble 

cupboard 


width) 




- Chairs 


Policed Paint 

7 Chemical 

storage 



chips 

Walls: 


height 


(One leaf) 

Two Aluminum 

Windows with 



protection 

-Shelves 


Policed Paint 

8 Clean & Dirty 

locker rooms 



chips 

Walls: 


all height 

Steel door (Ds3) 

(One leaf) 

Three Aluminum 

Windows with 


(W1) ) and steel 

protection 

Steel Cupboards 


Policed Paint 

9 Wc.s & 

showers 


Non sliding Ceramic 

Tiles 

Walls: 


height 

Wooden doors 

(Dw2) (One leaf) 

Six Aluminum 

Windows with 



protection 

-showers, basin and 

W.C.s 


Policed Paint 

10 stair Floors & Skirting: 


Tiles 

Steps: 

Rozabita Marble treads 

and oriz marble risers 

Walls: 



above 


Policed Paint 

Steel door (DS1) 

(two leaves) 

Four Aluminum 

Windows with 



protection 






SECOND FLOOR 

1 Entrance hall Floors & Skirting: 


Tiles 

Walls: 



above 

One Aluminum 

Windows with 



protection 

Furniture & 

Equipments 

- Chairs for waiting 

- Wooden Table 


Policed Paint 

2 Corridor Floors & Skirting: 


Tiles 

Walls: 



above 


Policed Paint 

3 Office Floors & Skirting: 


chips 

Walls: 



above 


(One leaf) 

Two Aluminum 

Windows with 



protection 

Tables , chairs 

,computers & 

cupboard 


Policed Paint 

4 Copy & Paper 

Storage 



chips 

Walls: 



above 


(One leaf) 

Two Aluminum 

Windows with 



protection 

U shape wooden 

counter , chairs 

,computer , printer, 

copy machine , 

shelves & cupboard 


Policed Paint 

5 Break room Floors & Skirting: 


chips 

Walls: 


height 


Policed Paint 


(two leaves) 

Two Aluminum 

Windows with 



protection 

- Marble cupboards 


width) 




include sinks 

- Chairs 

- tables 






6 Control room Floors & Skirting: 


chips 

Walls: 



above 


Door (two leaves) 

Four Aluminum 

Windows with 



protection 

Furniture & 

Equipments 

- Computer Tables 

- Computers 

- Chairs 

- cupboards 


Policed Paint 

7 Server room Floors & Skirting: 


chips 

Walls: 


height 


Door (One leaf) 

One Aluminum 

Windows with 



protection 

-4 Servers 


Policed Paint 

8 Secretary 

room 



chips 

Walls: 



above 


(two leaves) 

Two Aluminum 

Windows with 



protection 

- L shape counter 

- Chair 

- chairs 

- cupboard 

- Computer with 

printer 


Policed Paint 

9 Meeting 

Room 



chips 

Walls: 



above 


(two leaves) 

Three Aluminum 

Windows with 



protection 

Meeting Table & 

chairs 


Policed Paint 

10 Manager 

Room 



chips 

Walls: 



above 


(One leaf) 

Two Aluminum 

Windows with 



protection 

L shape Table 

- Manager Chair 

- Table with four 

chairs 

- cupboard 

- Computer with 

printer 


Policed Paint 






11 Wc.s & clean Floors & Skirting: 

Non sliding Ceramic 

Tiles 

Walls: 


height 

Wooden doors 

(Dw2) (One leaf) 

Aluminum Windows 

with mosquito wire 

mesh (W3) and steel 

protection 

Furniture & 

Equipments 

-Basins and W.cs 


Policed Paint 

12 stair Floors & Skirting: 


Tiles 

Steps: 

Rozabita Marble treads 

and oriz marble risers 

Walls: 



above 

Four Aluminum 

Windows with 



protection 


Policed Paint 





3.10.4. PROCESS STRUCTURES 

3.10.4.1. PRE-TREATMENT 

The pre-treatment building consists of three units as follows: 

3.10.4.1.1. PRE-TREATMENT BUILDING UNIT 

The pre-treatment units with 2 floors cover an area of 340 m2 will be constructed. Pretreatment 

building will be elevated structures. The structural system used is two-way solid 

slabs rest over continuous beams that were supported on columns. The columns and the 

walls transmitted their loads to the foundation. The used footings are strip footing and the 

foundation level is 2.8m below the ground surface. 

3.10.4.1.2. GRIT REMOVAL BASIN UNIT 

Grit removal basins will be implemented in phase I as also the screen channels. in phase I, 

three basins will be constructed of which only two will be used. Reinforced concrete walls 

that transfer the load to a strip foundation will be used. Grit will be transferred through the 

overflow weir to the removal channel. Length of the basin is 16,25 meters, width 4meters, 

water depth is 3.3 meters. In the bottom of the basin will placed a sand pit with a total 

depth of 2.0 meters, and also a small sand sump. Chambers are equipped with traveling 

bridges, scrapers, scum screen and a grit classifier with containers. 

3.10.4.1.3. DISTRIBUTION WELL DW1 

The outlet of the grit removal basin deliver the pre-treated water to the distribution well that 

transfer and distribute it to the aeration tanks. 

3.10.4.2. AERATION BASINS 

Three aeration basins will be used for phase II, of which two basins will be constructed for 

phase I. these basins will be made from reinforced concrete, and to be facilitated with 

partition walls and outlet channels. Influent to the aeration basins will enter through the 

distribution well. Effluent of the aeration basins will be conducted through an overflow weir 

located at the end of the basin that transfer it to distribution well. Basins will be facilitated 

with concrete made service bridges and with handrails. 

Water depth in the tanks reaches up to 8m. Walls are constructed to resist horizontal water 

pressure. The geometry of the wall has non prismatic section to suit the stresses 

distribution, the wall thickness at the base is 90cm and 70cm at the top. The walls are 

assumed to be fixed at the bottom and hinge at the top (horizontal tie beams) 

The following loading cases have been considered in design: 

- Case 1: due to leakage test. 

- Case 2: when the tank is empty the soil surrounding the tank acting as active 

pressure. 

- Case 3: neglect uplifting force, because the distance to the water table level under 

the tank reaches 60m. 





Top of the basins will be 3.30 meters above the ground level and the level of foundation is 

6.46m below the ground level. The width of the aeration tank is 22m and the length is 

97.10m. 

3.10.4.3. SECONDARY CLARIFIERS 

Six circular tanks for the secondary clarifiers will be used for phase II, four tanks will be 

constructed for phase I. the diameter of each circular tank is 33 m, and the depth is 3.80m. 

Top of the tank will be 1.68m above the ground level. The clarifiers will be made of fairface 

concrete. The circular walls of the tanks stand on a circular mat foundation. Each pair 

of tanks has a rectangular concrete sludge pit of 9.0x5.0m and 5.8 depth, scum collection 

concrete tank of 4.30x1.45 m and 3.90 depth, and degazing concrete tank of 7.20x5.70m 

and depth 5.40 m. these tanks facilitated with stairs, steel covers, and balustrades. 

3.10.4.4. GRAVITY THICKENERS 

Three circular tanks for the gravity thickeners will be used for phase II, two tanks will be 

constructed for phase I. the diameter of each circular tank is 17m, and the depth is 4.5 m in 

average. top of the tank will be 3.60 m above the ground level. The thickeners will be 

made of fair-face concrete. The circular walls of the tanks stand on a circular mat 

foundation. The gravity thickeners facilitated with concrete platform, circular stairs, and 

handrails. 

3.10.4.5. SAND FILTERS 

The system is traditional sand filtration in concrete blocks with backwash system. four filter 

units will be constructed in phase I and two additional filters for phase II. the units consist 

of concrete basins and special type of intermediate floor where the filter consist of two 

layers, the first is sand with height of 1400mm and the second is gravel with height of 

100mm. 

Pre-cast concrete panels of 0.49m x 1.15 m and thickness 15cm are proposed for 

supporting the filter media (sand). 220mm long stem nozzles are used for filtration, the 

number of these nozzles is 50/m2 and accordingly, every concrete panel will be equipped 

with 28 nozzles. Pre-cast units are fixed with beams using steel plate with 15cm width and 

2cm thickness and 2.5cm diameter bolts. 

The sand filter building with 2 floors will be constructed. Building is located partly below 

the existing ground level. The area of the building is around 770 m for phase I. the 

building will be extended during the phase II in order to allow implementation of the new 

filtration units. Bottom floor and the treatment units and channels will be made by 

reinforced concrete. 

The bottom floor consists of: 

- Basin for the dirty water. 

- Basin for the clean water 

- Basin for the backwashing water 

- Pumps rooms. 

- Facilities for UV disinfection. 

- Basin for washing water. 





The ground floor consists of: 

- Room for electrical systems. 

- Service level. 

- Inlet channel and distribution channel. 

- The compressor hall. 

Facilities: tracks for the crane, the equipment for lifting and removing of materials, covered 

openings. 

Facilities outside: stairs. 

3.10.4.6. SLUDGE DRYING BEDS(SLUDGE DEWATERING) 

Sludge will be pumped to the main channel from where it will be conducted to the drying 

beds trough a distribution channels equipped with closure discs. Earth based drying beds 

are equipped with drainage pipes in the bottom and sand layer above the pipes. 

Layers sequence as follows: 

The inlet end of the drainage pipes will be located above the sand level to allow flushing of 

the drainage pipes when need. Filtered liquid will conducted back to the treatment 

process. 

Partition walls made by pre-cast concrete walls and distribution channel shall be 

implemented. The area consists of 32 drying beds in the construction phase, each with 

area of around 450 m2. After the extension the total amount of similar beds will be 54 in 

phase II. 

3.10.4.7. SLUDGE DRYING BEDS (SLUDGE DEWATERING) 

Composting field with suitable slope will be paved with asphalt. Excess water will flow from 

the composting field to a ditch transferring the liquid to the reject water pumping station 

from where it is pumped in the beginning of the treatment process. 

3.10.5. ROADS AND FENCING 

There are three types of road in KY WWTP, heavy (asphalt) roads, light (interlock) roads, 

and stabilized roads. The heavy roads with an asphalt pavement of 5m width will be 

implemented for the roads that serve the heavy traffic loads. While the roads of the light 

traffic loads will be paved by interlock with width of 5 m. Stabilized roads contains sub-base 

and base-course layers. 

These roads designed according to the standards set by (AASHTO). Medium traffic is 

expected in these roads , i.e. 300 to 500 ESAL. Consequently, design will be based on 500 

ESAL. (for more details refer to annex 4) 

The structural design showed that the roads will be composed of four main layers to 

sustain trucks traffic loads: 





1. Wearing asphalt layer of 3cm 

2. Blinder asphalt layer of 4cm 

3. Base course layer (composed of 30cm base coarse compacted in two layers) 

4. Sub base layer (composed of 40cm Kurkar compacted in two layers). 

Typical section for the heavy roads is presented hereinafter: 

Fig. 4. TYPICAL SECTION IN FOR THE HEAVY ROADS 

Light roads will be composed of the following: 

1. Interlok tile (set pavement) 

2. Sand layer (5 cm) 

3. Base course layer (composed of 30cm base coarse compacted in two layers) 





Fig. 5. TYPICAL SECTION IN FOR THE LIGHT ROADS 

The roads will be composed of two lanes with width of 2.5m each. 

A galvanized steel fence with a height of 2 meters to be located in the borders of KY 

WWTP site. a 4mm wire with 50mm mesh used in KY WWTP fence, this mesh is attached 

to a 60 mm O.D. pole tube. The pole tube will be anchored into a concrete blocks of 

35x35x100 cm. Bracing bars, stretcher bar, and tension wire will be used for fixation. The 

site will be facilitated with two swing gates with width of 6m. The gate frame will be 60 mm 

O.D. pole tube. 

3.11. PRESSURE PIPES AND OTHERS STRUCTURES 

3.11.1. EFFLUENT PRESSURE LINE 

3.11.1.1. GENERAL DESCRIPTION 

The effluent pressure line is the pipe used to pump the treated effluent from the effluent 

pump station at the WWTP to the infiltration basin at Al Fukhari area or to the sea in 

emergency cases. 

The effluent pressure line consists of six sections as the following: 





a. Section (1): starts from the effluent pump station and ends at station R1-137+15.79. It 

has a length of 3355 m and has a nominal diameter of 920 mm. At this station, a split 

junction ( Tee connection) is used to split the effluent pressure line into two branches. 

The first branch diverts the flow towards the infiltration basins and the second branch 

diverts the flow towards the sea in emergency cases. 

b. Section (2): starts from the split junction and extends to the infiltration basins at Al 

Fukhary. It has a length of 2300m and has a nominal diameter of 920 mm. 

c. Section (3): starts from the split junction and extends to the highest point on the route 

to the sea (at station R1-376). It has a length of 4760 m and a nominal diameter of 

1030 mm. At the end of this section (at station R1-376) a concrete energy breaker is 

installed (EB 1) to reduce the kinetic energy of the flowing water. This energy breaker 

is the end of the pressure system produced by the effluent pump station at the 

KWWTP. 

d. Section (4): starts from EB1 to EB2 ( the second energy breaker) .This section is 

designed as an inverted siphon pressure pipe to make use of the potential energy 

created by the effluent pumping station at EB1 . The advantage of this design is to 

reduce the excessive excavation work along this section if we use gravity system. This 

section has a length of 2140 m and a nominal diameter of 920 mm. At the end of this 

section (at station R1-483) a concrete energy breaker is installed (EB 2) to reduce the 

kinetic energy of the flowing water. 

e. Section (5): starts from EB2 to EB3 (the third energy breaker).This section is also 

designed as an inverted siphon pressure pipe to make use of the residual potential 

energy at EB2. The advantage of this design is to reduce the excessive excavation 

work along this section if we use gravity system. This section has a length of 2240 m 

and a nominal diameter of 920 mm. At the end of this section (at station R1-595) a 

concrete energy breaker is installed (EB 3) to reduce the kinetic energy of the flowing 

water. 

f. Section (6): starts from EB3 to the sea outfall structure. This section is also designed 

as a gravity pipe. This section has a length of 3780 m and a nominal diameter of 920 

mm. At the end of this section (at station R1-783+8.98) a concrete sea outfall structure 

is constructed. 





Figure n°4 illustrates the layout and different sec tions of the effluent pressure line as 

mentioned above. 

Fig. 6. SECTIONS OF THE EFFLUENT PRESSURE LINE 

3.11.1.2. OPERATION MODES OF THE PRESSURE EFFLUENT LINE: 

The effluent pressure line will be operated in the following operation modes: 

A. Normal mode : 

Normally, the effluent pressure line will be transferring the treated effluent to the infiltration 

basins at Al Fukhari. This operation mode achieves the main purpose of the improving the 

groundwater quality and quantity in Al Fukhari area aquifer and eventually saving a 

valuable water resource for the agricultural activity in the area. 

B. Emergency mode: 

Pumping to the sea outfall is the emergency operation mode. This mode will be in 

operation at following cases only: 

Maintenance works in treatment plant leading to lower water quality that is 

not adequate for infiltration, so the treated will be pumped directly to the 

sea. 

Emergency cases or maintenance in the infiltration basins site. 





3.11.1.3. DESIGN OF EFFLUENT PRESSURE LINE: 

3.11.1.3.1. PIPES DIAMETERS AND MATERIALS: 

The diameters of the effluent pressure line sections were selected on the bases of the 

following main criteria: 

The velocity is in the range of 0.75 to 2.5 m/s. With a preferable velocity 

range of 1 to 2 m/s. 

The diameter was selected based on optimization calculations to get the 

optimum combination between the investment cost and the operation cost. 

The detailed hydraulic calculations of the pressure line and the succeeding gravity line are 

given in Appendix 3. The selected diameters for the different sections are listed in the 

following table 

Section No. Pipe diameter (mm) Length (m) Material Flow type 

1 920 3355 Steel lined with cement Pressure 





6 920 3780 Steel lined with cement Gravity 

It should be noted that the diameter of section 3 is increased to 1030 mm to reduce the 

head losses in this section. This modification is made to minimize the difference between 

the piping system curve when pumping to the infiltration basin and the piping system curve 

when pumping to the sea. As a result of this modification, the effluent pumps can be used 

efficiently in both modes of operation without the need to have variable speed pumps or to 

use different size constant speed pumps. Figure n°5 illustrates the piping system curves 

when pumping to the infiltration basin and to the sea. 





Fig. 7. SYSTEM CURVES OF THE EFFLUENT PIPE TO THE INFILTRATION BASIN AND TO THE SEA 

3.11.2. PRESSURE LINE FROM WWTP TO INFILTRATIONS BASINS AND SEA OUTFALL 

3.11.2.1. VALVES INSTALLED ON THE EFFLUENT PRESSURE LINE: 

a. Double acting Air release /vacuum relief valves 

These valves are installed at the following locations 

All height points 

Long rising segments at intervals of 750 to 1000 m 

Long descending segments at intervals of 750 to 1000 m 

The details of these valves are illustrated in the typical details drawings. 

b. Drainage valves 

These valves are installed at the following locations: 

All low points 

Long rising and flat pipes at intervals of 500 m 

The details of these valves are illustrated in the typical details drawings. 





The waste water will be drained by vacuum tankers. The drainage valves 

are equipped with quick connection (such as the connection of fire hose) to 

ease the connection between it and the vacuum tanker hose connection. 

The vacuum tanker will dispose the evacuated waste water to the nearest 

sewage pumping station or to the nearest manhole in the gravity system of 

Khan Younis. Evacuation of the sewage from the pressure line into private 

land or into the environment is not allowed 

c. Cleaning access connections (Blow off connections): 

These connections are constructed on the gravity pipe (section 6) at 100m interval starting 

from EB3. Each connection is made from,920 mm diameter steel pipe welded vertical on 

the gravity pipe and extended to the street level and closed from its upper side with a blind 

flange that can be opened in case of blockage of the line. These connections are used for 

maintenance instead of constructing the typically used manholes on gravity lines. The 

purpose is to prevent the population a long the gravity section from connecting their house 

connections to the line. This is a very important issue. If the population connect to the line 

we will have a continuous pollution to the sea from these illegal connections which will 

jeopardize all the project as a whole. 

The number and types of these valves are summarized in the following table: 

Type of Valve 

Number of valves 

Air release/ Vacuum relief valves 11 

Drainage valve 7 

Blow off connections 33 

3.11.2.2. DESIGN CRITERIA FOR SELECTING AND SIZING THE AIR RELEASE VALVES 

The Air / Vacuum or Combination Air Valve should be capable of admitting air after power 

failure or line break at a rate equal to the potential gravity flow of water due to the slope of 

the pipe. The flow of water due to slope can be found by the equation: 

Q = 0007872*C* ( S*D5 ) 1/2 

Where: 

Q = Flow of water, CFS 

C = Chezy Coefficient = 110 for iron pipe 

S = Slop of pipe, vertical rise/horizontal run. 

D = Pipe inside diameter, inches. 

The gravity flow due to slope is calculated for every pipe segment. For stations where there 

is a change in up slope or down slope, the difference between the upstream and 

downstream flows is used for sizing because the upper segment feeds the lower segment 

and helps prevent a vacuum from forming. 

When steel or any collapsible pipe is used, it is important to determine if there is a risk of 

pipeline collapse due to the formation of a negative pressure. The following equation finds 





the external collapse pressure of thin wall steel pipe using a safety factor of 4. A safety 

factor of 4 is recommended to take into account variances in pipe construction, variances 

in bury conditions, and possible dynamic loads. 

P = 16,250,000 * ( T/D)3 

Where: 

P = Collapse Pressure, psi 

T = Pipe Thickness, in. 

D = Pipe Diameter, in. 

Collapse may also be a concern on large diameter plastic or ductile iron pipe. The pipe 

manufacturer should be asked to provide maximum external collapse pressures. 

The valve should be capable of admitting the flow due to slope without exceeding the lower 

of the calculated pipe collapse pressure or 5 PSl ( 35 kPa ). 5 PSl (35kPa) is used for 

sizing to remain safely below the limiting sonic pressure drop of 7 PSl ( 48 kPa). 

Manufacturers provide capacity curves for their valves which can be used to select the 

proper size. The capacity of an Air / Vacuum Valve can be estimated using: 

q = 678 *Y*D2*C* (DP*P1÷ Sg ) 1/2 

Where: 

q = Air Flow, SCFM 

Y = Expansion Factor 

0.79 ( for vacuum sizing) 

0.85 ( for exhaust sizing at 5 psi ) 

0.93 ( for exhaust sizing at 2 psi ) 

d = Valve Diameter, in 

Dp= Delta Pressure, psi 

The lower of 5 psi or pipe collapse pressure ( for vacuum sizing 2 or 5 psi ( for exhaust 

sizing) 

P1 = Inlet pressure, psia 

14.7 ( for vacuum sizing) 

16.7 or 19.7 psia ( for exhaust sizing at 2 or 5 psi ) 

T1= Inlet Temperature – 520 R 

Sg = Specific Gravity = 1 for air 

C = Discharge Coefficient = .6 for square edge orifice 





The air valve should also be sized for exhausting air during filling of the system. The flow 

rate used for venting should be the fill rate of the system. The fill rate may be the flow rate 

from a single pump in a multiple pump system. If there is only one pump in the system, 

then special filling provisions should be taken such as the use of a smaller pump for filling 

or the ability to throttle the flow from the pump to achieve a fill rate in the range of 1 to 2 ft/ 

sec ( 0.3 to 0.6 M/sec). Higher fill rates may cause surges in the line and Anti Slam 

Devices should be used to reduce the surges within Air/ Vacuum or Combination. 

The location of these valves is shown in the effluent pressure line profile drawing (DD-P- 

001). 

3.11.2.3. TANKS AND CHAMPERS INSTALLED ON EFFLUENT PRESSURE LINE 

a. Surge tank 

A 35 m3 ARAA type (Automatic Air Regulation) stainless steel surge tankis installed at the 

beginning of the pressure line just down stream of the manifold. The purpose of the surge 

tank is to control the water hammer that my occur due to sudden power failure. The 

detailed water hammer analysis and the selection of the surge tank type and volume is 

given in Appendix 3.1. 

b. Energy breakers 

Energy breakers are concrete champers that are used to dissipate energy at the end of 

pressure lines. Three energy breakers are installed on the effluent pressure line. The first 

energy breaker (EB1) is installed at the end of section3. The second and third energy 

breaker (EB2 and EB3) are installed at the end of sections 4 and 5, respectively. The three 

energy breakers have typical design. The detailed design of the energy breakers are 

shown on drawings (DD-P-023&024). 

3.11.2.4. HORIZONTAL ALIGNMENT AND VERTICAL PROFILE OF EFFLUENT PRESSURE LINE: 

The horizontal alignment of the pressure line is carefully designed after studying the 

existing infrastructure utilities (water & wastewater networks – electricity installations– 

communication network) to avoid or minimize any damage that may occur during the 

construction stage. Accordingly, the location of the pressure line changed from right to left 

at some locations. The vertical alignment of the pressure line was designed to follow the 

profile of the existing roads to minimize the excavation cost. A minimum cover of 1.5 m 

was selected. The details of the horizontal and vertical alignments are shown on drawing 

(DD-P-001) 

3.11.3. INFILTRATIONS BASINS 

3.11.3.1.1. INTRODUCTION: 

Infiltration Basins (IBs) are permeable earthen basins, designed and operated to treat and 

disperse municipal treated wastewater. IBs are typically operated in conjunction with 

Municipal wastewater treatment systems / plants. 

The Infiltration basin system is managed by repetitive cycles of flooding, infiltration and 

drying. Rapid infiltration of wastewater is based on a relatively high rate of wastewater 

infiltration into the soil followed by rapid percolation, either vertically or laterally away. The 





best soils for rapid infiltration are relatively coarse textured, with moderate to rapid 

permeability. 

3.11.3.1.2. DESIGN PHASES: 

A. Investigation of infiltration requirements: 

The establishment of the needed area for direct (natural) infiltration purpose depends on 

the following factors: 

Influent flow rate 

Operation & Maintenance activities 

Infiltration rate 

a. Influent flow rate: 

As the flow rate which loading the infiltration basins increased, the needed infiltration area 

will increase in order to accommodate the incoming amounts of water. The period of 

pumping is affect also on the flooding period needed for each basin to operate. 

b. Operation & Maintenance activities: 

Operation and maintenance activities will control the hydraulic loading cycle which shall 

affect on the needed loading infiltration area. A regular drying period is necessary for 

system performance. To maximize infiltration the drying periods should be long enough to 

re-aerate the soil, to dry and oxidize the filtered solids. 

To maximize nitrogen removal the entire basin needs to be flooded, and the application 

period must be long enough for the soil bacteria to deplete soil oxygen, resulting in 

anaerobic/denitrifying conditions. The Pollution Control Agency suggested loading and 

Drying cycles as shown in the table below: 

Objective 

Maximize Infiltration 

Pond Discharge 

Application Period 

(days) 

Drying Period 

(days) 

Primary 1-2 5-7 

Rates Secondary 1-3 4-5 

Maximize Nitrogen 

Primary 1-2 10-14 

Removal Secondary 7-9 10-15 

* Source: Guidance and Submittal Requirements for Rapid Infiltration Basin Wastewater 

Treatment Systems, Minnesota Pollution Control Agency, 2005. 

Similar Local experiences in this field can be useful. In Shafadan infiltration basins ( In 

Israel ), the loading cycle system was designed for ( 1-2 ) days flooding alternated with ( 2- 

5 ) days drying. 

Other important operation factor is to determine the ratio of the basin area simultaneously 

in use to the total basin area which varies between (25% to 0.33%). 

c. Infiltration Rate : 

Infiltration rate is the rate at which water penetrates the surface of the soil, expressed in 

cm/hr, mm/hr, or inches/hr. The rate of infiltration is limited by the capacity of the soil and 





the rate at which water is applied to the surface. The soil capacity is obtained by identifying 

the soil textures by a gradation test for each change in soil profile. For each soil texture 

type, minimum infiltration rate is recommended depending on previous tests on each 

texture class. These values are summarized in the table below: 

Texture Class 

Effective Water 

Capacity (C w) 

( inch per inch) 

Minimum 

Infiltration Rate 

( inches per hour) 

Hydrologic Soil 

Grouping 

Sand 0.35 8.27 A 

Loamy Sand 0.31 2.41 A 

Sandy Loam 0.25 1.02 A 

Loam 0.19 0.52 B 

Silty Loam 0.17 0.27 B 

Sandy Clay Loam 0.14 0.17 C 

Clay Loam 0.14 0.09 D 

Silty Clay Loam 0.11 0.06 D 

Sandy Clay 0.09 0.05 D 

Silty Clay 0.09 0.04 D 

Clay 0.08 0.02 D 

* Source: (Rawls, Brakensiek and Saxton, 1982) 

Based on the soil textural classes and the corresponding minimum infiltration rates, a 

restriction is established to eliminate unsuitable soil conditions. Soil textures with minimum 

infiltration rates less than 0.52 inches per hour are not suitable for usage of infiltration 

practices. Soil textures that are recommended for infiltration systems include those soils 

with infiltration rates of 0.52 inches per hour or greater, which include loam, sandy loam, 

loamy sand, and sand. 

B. Investigation of site specific infiltration condition: 

According to the basic soil investigations ( one deep borehole in each site) implemented in 

both Khuza'a and Muraj proposed infiltration sites, the results show that Khuza'a site is 

considered the best area for infiltration purpose so this area is chosen as the approved 

infiltration area. 

a. Site description: 

Khuza'a infiltration site has available top area of (97,000 m2) with a trapezoidal shape. The 

top soil consists of sandy silty clayey layer with thickness between 1 to 6m above clay layer 

with thickness between 4 to 6 m. Thus; infiltration basins can't be constructed directly on 

the ground. The clay layer will be excavated an removed from the site, then the basins will 

be backfilled by suitable soil with high hydraulic conductivity until reach the design level of 

each basin. 

b. Area basins requirements : 

By Applying the factors of basin area determination mentioned in section (2.1), the results 

are summarized in the following points: 





Influent Flow Rate: 

The influent flow rate that will received by the infiltration basins was considered as the 

average flow for phase (1) ( 26,656 m3/day). 

Operation and Maintenance Activities: 

The loading cycle system that will be taken is to operate 2 days for flooding & 4 days 

for drying. 

Infiltration Rate: 

Depending on the above data, brief calculations for the required area was performed 

for several infiltration rates as shown in the following table. 


(m/d) 

Required bottom area if effective area equal (m 2 )* 

25 % 33 % 67 % 

0.6 177,76 134,66 66,32 

1.0 106,65 80,80 39,79 

1.2 88,88 67,33 33,16 

1.5 71,10 53,86 26,53 

* 

Based on the range of infiltration rates and the ranges of effective basin area, the results 

show that the more reasonable area is ( 67,333 m2) which meets infiltration rate of 1.2 

m/day and effective area of 33%. This conclusion was supported by the following site 

determinants: 

- The available bottom area in the site can be determined approximately by 

subtraction the top area of the site from the area needed for roads , basin side 

slopes, and other needed building facilities. The following equation show this 

calculation. 

- 2-Referring to the soil profile section for ( F9- BH01-03-04) motioned in soil 

investigation report (Al Fukhari infiltration basin pilot wells and pumping & 

recharge tests, 2009 ), the range of the infiltration rate for the top soil ( 8 m 

average depth) varies from ( 1 to 1.6 m/d), so the average value (1.3m/d) is 

greater than the chosen one ( 1.2 m/d). 

Based on the available bottom area (67.900 m2) and the respective design flow in addition 

to using 33 % effectiveness for infiltration rate, the infiltration rates and hydraulic loads will 

develop as shown in the table below: 





Year 

Q avg (m 3 /day)* 

Hydraulic Load 

(m 3 /m 2 /year) 


(m/d) 

2010 13,905 75 0.62 

2015 21,673 117 0.97 

2018 26,664 143 1.19 

* Resource : Initial Design Report,2009 table (4.9), updated value. 

The hydraulic loads resulted can be compared with hydraulic load of similar local infiltration 

basins. The main conclusion is that the hydraulic load of Khuza'a infiltration basins seems 

reasonable and sufficient until 2018 (Phase 1). After 2018, the infiltration area has to be 

extended to reach the same hydraulic load. 

Comparison between hydraulic rate of the site and similar local sites 

Site Name 

Location 

Hydraulic Load 

(m 3 /m 2 /year) 

Khuza'a South of Gaza strip 61 to 143 

Shafadan Israel 134 to 215* 

NWWTP infiltration basins North of Gaza strip 89 to 162* 

* Resource :NGWWTP final infiltration system rport,2002. 

C. Geometric Design of infiltration basins: 

a. The number of the infiltration basins: 

The basin layout and dimensions are controlled by topography, distribution system 

hydraulics, and loading rate. The number of basins is also affected by selected loading 

cycle. The minimum number of basins required for continuous wastewater application is 

presented as a function of loading cycle in the table below. 





Loading application 

period (day) 

Cycle drying period 

(day) 

Minimum number of 

infiltration basins 

1 5-7 6-8 

2 5-7 4-5 

1 7-12 8-13 

2 7-12 5-7 

1 4-5 5-6 

2 4-5 3-4 

3 4-5 3 

1 5-10 6-11 

2 5-10 4-6 

3 5-10 3-5 

1 10-14 11-15 

2 10-14 6-8 

1 12-16 13-17 

2 12-16 7-9 

* Source : Rapid infiltration process design manual, USACE army. 

According to the table above and the infiltration rate effectiveness ratio (33%), the number 

of infiltration basins was chosen to be (6 basins). 

Assuming that the needed loading area per day will divided into 2 basins, the total number 

of basins can be calculated as follow: 

b. Infiltration basin slopes: 

The bottom of the basin should be graded as flat as possible to provide uniform ponding 

and infiltration of the loaded water across the floor. The side slopes of the basin should be 

no steeper 1V:2H to assure soil stability, allow for proper vegetation stabilization, easier 

access, emphasizes accessibility and ease for maintenance. 

c. Infiltration Site geometric design: 

The site has been divided into 6 basins each with bottom area of 11,200 m2. The design 

level of the bottom of basins has been graduated into 3 levels to befit the topography of the 

site and the surrounding area. The bottom of basins considered to be flat without any 

slope, and the side slope of the basins has been taken 1V:2H which assure soil stability, 

however the basins layout has been implemented by the way which guarantee, for each 





basin, reaching the existing level of the edges border lines to avoid any objections from the 

private land owners. 

D. Infiltration basins Facilities: 

The facilities of the infiltration basin can be listed as follow: 

1. Access roads. 

2. Chamber valve rooms. 

3. Administration building. 

E. Access Roads: 

A main road and corridors around the basins were designed to facilitate the movement 

inside the basin's site. A brief description for each type of road can be summarized as 

follow: 

3.11.4. SEA OUTFALL 

The Emergency pipe line in this project is used to deliver treated sewage from the KWWTP 

to the sea in emergency situations only. Such situations may occur when some of the 

infiltration basins are out of work for maintenance or incase the infiltration basins are full of 

water for any reason (such as heavy rain events , etc..). 

The quality of the treated wastewater in the KWWTP meets the allowable Palestinian and 

international standards for pumping to the sea. Consequently, the sea outfall is designed 

to deliver the treated wastewater at a point very close to the shore taking into account the 

following Criteria: 

- Protecting the shore at the outfall location from erosion 

- Considering the aesthetic appearance of the outfall 

- Keeping the continuity of traffic on the shore around the outfall 





The sea outfall is given in the following figure: 

s 

e 

a 

Effluent pipe 

Concrete walls 

o 

u 

t 

f 

a 

l 

l 

Concrete walls 

(energy breaker) 

Rip Rap channel 

to the sea 

Concrete base 

Fig. 8. SEA OUTFALL 

The sea outfall consists of a concrete structure constructed at the end of the gravity section 

of the effluent pipe (section 6) and a Riprap channel that transfers the water to the sea. 

The concrete structure has a hexagon projection and its walls are covered with rocks from 

the exterior side to give a nice architectural view on the beach. The Riprap channel is 

made of heavy rocks to resist the erosion caused by the sea waves and to give a nice 

architectural. The channel is also designed to allow smooth traffic across it on the beach. 

The detailed drawings of the sea outfall are shown in drawing (DD – P- 025). 





4. 

INVESTMENT COSTS EVALUATION 

4.1. WWTP 

4.1.1. GENERAL PRINCIPLES 

The investment costs for WWTP are expected to be paid in different currencies, namely : 

- mainly because the imported equipment and materials, as well international staff, 

will be paid in foreign currencies 

- also, because the most of the civil works costs ( staff, raw materials, …) will be 

paid in local currency, i.e. the USD for the Palestinian territories. 

Then, the cost estimate is prepared considering 2 different currencies, one foreign 

currency , which will be chosen by the bidders – we retain in this report to use the Euro -, 

and the local currency ( USD) 

In fact, most of the equipment will be paid in foreign currency (here the EUR) and most of 

the civil works will be paid in local currency (the USD). 

Depending on the donors or funding agencies, this kind of project doesn’t (or does) bear 

VAT, taxes, or levies. Then because the funding agreements are not totally fixed at this 

time, all rates are estimated without any taxes or levies. 

The estimation is on the basis January 2010; for the calculation of the Global price in USD, 

the applied exchange rate is : 1 EUR = 1.40 USD. 

4.1.2. DAYWORKS 

In a such project, it is common to include in the BoQ, some rates for Dayworks. These 

rates will cover small unexpected works or adjoining works. 

We considered these rates as usually done, ie. the Contactror will propose in the bid 

special rates for Dayworks (gross cost ) , and a % ratio is applied for all related small costs 

( small tools, water, transportation of staff,…) 

These percentages are fixed as follows: 

- 20% for the labour charges 

- 15% for the Equipment and Materials charges 





For the purpose of the present estimate, we propose to use, as provisional sum ; the 

following figures 

- 50 000 USD for the equipment use 

- 50 000 USD for the Materials charges 

- 50 000 USD for the Labour charges 

4.1.3. ORIGIN OF UNIT PRICES 

For all unit prices, we used actual unit prices observed for similar works, with the following 

consideration: 

Unit rates of the equipment are based on similar recent projects in Europe; then, we add to 

these prices, a 15% ratio for taking into account the cost of transportation and assurance. 

Unit rates of the civil works are based on some recent important project in Gaza or West 

Bank; then, we add to these prices, a 10% ratio for taking into account the necessary cost 

increase to quality control, which will be involved in this particular project. In some cases, 

unit prices were considered in the Far East area, because not available in Palestina. 

4.1.4. SUMMARY 

As result of the previous consideration the investment costs for the WWTP are as follows : 





BILL1 GENERAL 

Total Bill 1 General 

WWTP PHASE 1 

WWTP PHASE 2 

Amounts 

Amounts 

FEX USD FEX USD 

1 245 000 600 000 650 000 250 000 

BILL 2 SCREENING AND PRETREATMENT 

Total Bill 2 Screening and Pretreatment 

BILL 3 MANHOLES AND DISTRIBUTORS 

Total Bill 3 Manholes and distributors 

698 145 554 729 183 998 0 

23 877 133 710 4 032 18 870 

BILL 4 AERATION TANKS 

BILL 5 CLARIFIERS 

BILL 6 SAND FILTERS 

BILL 7 THICKENER 

Total Bill 4 Aeration Tanks 

Total Bill 5 Clarifiers 

Total Bill 6 Sand Filters 

Total Bill 7 Thickeners 

2 700 665 4 184 077 1 078 126 1 410 200 

742 411 1 513 745 370 546 503 400 

1 496 451 1 499 340 483 002 335 573 

354 690 300 430 167 400 96 700 

BILL 8 DRYING BEDS AND COMPOSTING AREA 

Total Bill 8 Drying beds and composting area 

45 390 2 415 750 31 550 1 220 600 

BILL 9 ROADS 

BILL 10 PIPING 

BILL 11 OFFICE BUILDING 

BILL 12 WORKSHOP 

BILL 13 LANDSCAPING 

Total Bill 9 Roads 

Total Bill 10 Piping 

Total Bill 11 Office Building 

Total Bill 12 Worksop 

Total Bill 13 Landscaping 

0 490 070 0 0 

306 320 0 143 121 0 

39 991 390 759 1 860 0 

0 108 783 0 0 

0 1 345 140 0 81 375 

BILL 14 22KV DISTRIBUTION LINE 

Total Bill 14 22KV Distribution Line 

0 548 614 0 0 

BILL 15 MISCELLANEOUS 

Total Bill 15 Miscellaneous 

32 785 964 230 0 0 

TOTAL BILL OF QUANTITIES WWTP 7 685 725 15 049 377 3 113 634 3 955 018 





Then, considering an exchange rate of 1 EUR = 1.4 USD, the global cost for the WWTP is: 

- Phase 1 : 7,7 MEUR + 15 MUSD = 25,8 MUSD 

- Phase 2 : 3.1 MEUR + 3,95 MUSD = 8.3 MUSD 

4.2. TREATED EFFLUENT PRESSURE LINE 

Works realized in Phase 1 cover needs for Phase 2 (no additional works for Phase 2) 

Pressure Line 

FEX 

Phase 1 

Amounts 

USD 

SUB-BILL NO.1 - CONCRETE 0 171 600 

SUB-BILL NO.2 - Piping ITEMS 0 7 716 700 

Total Bill Pressure Line 0 7 888 300 

4.3. INFILTRATION BASINS 

Works realized in Phase 1 cover needs for Phase 2 (no additional works for Phase 2) 

Infiltration basins – Equipments 

FEX 

Phase 1 

Amounts 

USD 

SUB-BILL NO.7 - HAVC ITEMS 0 9 190 

SUB-BILL NO.9 - MECHANICAL EQUIPMENT 0 12 300 

SUB-BILL NO.10 - ELECTRICAL EQUIPMENT 0 142 094 

Total Bill Equipments (Infiltration Basins) 0 163 584 





Infiltration basins – Civil works 

Phase 1 

Amounts 

FEX USD 

SUB-BILL NO.1 - EARTHWORKS 0 5 313 400 

SUB-BILL NO.2 - CONCRETE 0 234 750 

SUB-BILL NO.3 - JOINTS 0 280 

SUB-BILL NO.4 - PROTECTIVES FINISHES 0 16 770 

SUB-BILL NO.5 – ROAD STRUCTURE MATERIALS 0 184 870 

SUB-BILL NO.6 - FABRICATED ITEMS 0 20 640 

SUB-BILL NO.8 - Piping ITEMS 0 506 500 

SUB-BILL NO.11 - Landscaping 0 72 160 

SUB-BILL NO.12 – Irrigation Network Items 0 3 545 

Total Civil Works Bill ( Infiltration Basins) 6 352 915 

Total investment cost for infiltration basins is thus: 

Civil works 

Equipments 

Total Infiltration Basins 

Phase 1 

Amounts 

6 352 915 USD 

163 584 USD 

6 516 499 USD 

4.4. GLOBAL PROJET COSTS 

Global project investment cost is summarized in the table below : 

Projet component 


Amounts 

Amounts 

FEX USD FEX USD 

WWTP 7 685 725 15 049 377 3 113 634 3 955 018 

Effluent pressure line 0 7 888 300 0 0 

Infiltration basins 0 6 516 499 0 0 

TOTAL 7 685 725 29 454 176 3 113 634 3 955 018 

Unexpected costs (15%) 1 152 859 4 418 126 467 045 593 253 

TOTAL including unexpected costs 8 838 584 EUR 33 872 302 USD 3 580 679 EUR 4 548 271 USD 

Overall total in USD * 46 1910 258 USD 9 561 222 USD 

(*) Exchange rate : 1 EUR = 1.4 USD 





Projet component 

Total Phase 1 & 2 

Amounts 

FEX 

USD 

WWTP Phase 10 799 359 19 004 395 

Effluent pressure line 0 7 888 300 

Infiltration basins 0 6 516 499 

TOTAL 10 799 359 33 409 194 

Unexpected costs (15%) 1 619 904 5 011 379 

TOTAL including unexpected costs 12 419 263 EUR 38 420 573 USD 

Overall total in USD * 

55 807 541 USD 

(*) Exchange rate : 1 EUR = 1.4 USD 





5. 

RUNNING COSTS 

5.1. WWTP 

The operating costs for KY WWTP are estimated for a one-year operation of the treatment 

plant at full load. The costs are estimated without taxes and charges and include the 

following items: 

- energy 

- waste disposal 

- personnel 

- maintenance 

Financial costs are not included in the estimate. 

Due to the degree of precision, estimates have been rounded. 

5.1.1. ENERGY COST 

The energy costs concern the electricity consumption. Preliminary cost estimates are 

calculated on a global consumption rate of 1,8 kWh/kg DBO5-incoming. 

Incoming load 

DBO 5 

Annual electricity 

consumption 

Unit cost 

Annual cost 

Phase 1 14 247 kg/d 9 360 300 kWh /year 0,09 $ US/ kWh 842 400 $ US/year 

Phase 2 22 399 kg/d 14 716 150 kWh 

/year 

0,09 $ US/ kWh 1 324 500 $ US/year 

5.1.2. WASTE DISPOSAL COST 

The various wastes (screenings, grease, grit) extracted in the plant are evacuated to 

landfill. 

Corresponding transportation and evacuation costs depend on that landfill site and are to 

be defined later. 





Item 

Annual quantity 

Phase 1 

Annual quantity 

Phase 2 

Screenings 

Grit 

Grease 

600 m 3 /year 

2 800 m 3 /year 

1 600m 3 /year 

1 000 m 3 /year 

4 700 m 3 /year 

2 700 m 3 /year 

Total 5 000 m 3 /year 8 400 m 3 /year 

5.1.3. PERSONNEL COST 

The WWTP work contract will include 1 year operation & maintenance after the completion 

certificate. During this year, local operating supporting staff will be supplied by CWMU. 

Required personnel categories for the local supporting staff and corresponding costs are 

detailed below: 

Category 

Monthly salary 

US $/month 

Number 

Annual salary (US $/month) 

Phase 1 Phase 2 Phase 1 Phase 2 

Manager 1 300 1 1 15 600 15 600 

Engineers/Technicians 800 3 3 28 800 28 800 

Skilled labour 500 6 6 36 000 36 000 

Total 10 10 80 400 80 400 

5.1.4. MAINTENANCE COST 

The maintenance cost includes the maintenance of works and equipment, cleaning, 

maintenance of green areas, repairs and replacement of consumables. 

The maintenance cost is estimated as a yearly percentage of the investment cost: 1% of 

civil works and 2.5% of equipment. 

ANNUAL MAINTENANCE COST – PHASE 1 

Item 

Civil works 

Equipment 

Investment cost for 

Phase 1 (in MUSD) 

15 

10, 7 

Percentage 

1.0% 

2.5% 

Annual cost 

$ US/year 

150 000 

268 000 

Total 418 000 





ADDITIONAL ANNUAL MAINTENANCE COST – PHASE 2 

Item 

Civil works 

Equipment 


Phase 2 (in MUSD) 

3,95 

4,36 

Percentage 

1.0% 

2.5% 

Additional annual cost 

$ US/year 

40 000 

109 00 

Total 149 000 

5.1.5. TOTAL OPERATING COST KY WWTP 

The total operating cost is summarised in the following table: 

Item 

Annual operating cost 

in $ US/year 

Phase 1 

Annual operating cost 

in $ US/year 

Phase 2 

Energy 842 400 1 324 500 

Personnel 80 400 80 400 

Maintenance 418 000 567 000 

TOTAL 1 340 800 1 971 900 

Waste disposal costs will have to be added to total operating costs. Compost may be 

source of revenues if sold to farmers. However, composting process requires also 

important amounts of structuring agent, wich needs to be identified and transported to 

WWTP site. 

5.2. TREATED EFFLUENT PUMPING AND DISCHARGE 

Including : treated effluent pumping station, pressure pipe, infiltration basins 

5.2.1. ENERGY COST 

Annual quantity Unit cost Annual cost ($ US) 

Phase 1 1,095,000 KWh 0.09 $ US/KWh 98,600 

Phase 2 1,500,150 KWh 0.09 $ US/KWh 135,000 





5.2.2. MAINTENANCE COST 

The maintenance cost includes the maintenance of works and equipment, cleaning, 

maintenance of green areas, repairs and replacement of consumables. 

The maintenance cost is estimated as a yearly percentage of the investment cost: 1% of 

civil works and 2.5% of equipment. 

ANNUAL MAINTENANCE COST – PHASE 1 

Item 


Phase 1 

Percentage 

Annual cost 

$ US/year 

Civil works 

14 404 799 * 

1.0% 

144 048 

Equipment 

680 584 ** 

2.5% 

17 015 

Total 161 063 

* Total cost of civil works for infiltration basins and pressure lines 

** Total cost of equipment for effluent pumping station and infiltration basins 

ADDITIONAL ANNUAL MAINTENANCE COST – PHASE 2 

Item 

Additional Investment 

cost for Phase 2 

Percentage 

Additional annual cost 

$ US/year 

Additional 

Equipment 

200 000 * 2.5% 5000 

Total 5000 

* Total cost of additional effluent pumps in outlet pumping station 

5.2.3. PERSONNEL COST 

Operating personnel requirements are estimated to 4 in phase 1 & 2 . Required personnel 

categories and corresponding costs are detailed below: 

ANNUAL PERSONNEL COST 

Category 

Monthly salary 

US $/month 

Number 

Annual salary (US $/ year) 

Phase 1 Phase 2 Phase 1 Phase 2 

Engineers/Technicians 800 1 1 9600 9600 

Skilled labour 500 1 1 6000 6000 

Unskilled labour 350 2 2 4200 4200 

Total 4 4 19800 19800 





5.3. OVERALL RUNNING COST 

Phase 1 

Consumption 

(in kWh/year) 

Energy 

Annual costs 

(in USD/year) 

Staff number 

(persons) 

Personnel 

Annual costs 

(in USD/year) 

Maintenance 

(in USD/year) 

Total annual 

cost 

(in USD/year) 

WWTP 9 360 000 842 400 10 80 400 418 000 1 340 800 

Effluent pumping 

and discharge 

1 095 000 98 600 4 19 800 161 000 279 400 

TOTAL 10 455 000 941 000 14 100 200 579 000 1 620 200 

Phase 2 

Consumption 

(in kWh/year) 

Energy 

Annual costs 

(in USD/year) 

Staff number 

(persons) 

Personnel 

Annual costs 

(in USD/year) 

Maintenance 

(in USD/year) 

Total annual 

cost 

(in USD/year) 

WWTP 14 716 000 1 324 500 10 80 400 567 000 1 971 900 

Effluent pumping 

and discharge 

1 500 000 135 000 4 19 800 166 000 320 800 

TOTAL 16 216 000 1 459 500 14 100 200 733 000 2 292 700 





6. 

PROJECT IMPLEMENTATION 

6.1. BIDDINGS PROCEDURE 

Work contracts are most often based on a set of documents, each of which supplements 

the others. The aim is to combine two principal objectives: 

- having reliable documents that offer good guarantees from the contractual 

standpoint and enable the parties to deal with all potential legal problems (appeals, 

arbitration, etc.) and all the technical issues of liabilities, guarantees, acceptance, 

reservations, etc., 

- having documents that can include and take into account the specific features of the 

site and project without distorting or contradicting the other contract documents. 

Numerous forms of contract have been developed by different countries and organisations 

to deal with these problems, such as: 

- Bidding Documents for Supply and Installation of Plant and Equipment (World 

Bank) 

- Conditions of Contract for Construction (FIDIC) 

- General Conditions of Contract for Civil Works (UNDP) 

- Many others forms 

The following is a brief analysis of these three main types: 

* The oldest type of document, which is regularly updated and is the most widely used 

throughout the world is the "General Conditions of Contract for Civil Works" published by 

the FIDIC, the latest version of which dates from 1999. 

FIDIC stands for "Fédération Internationale des Ingénieurs Conseils" (International 

Federation of Consulting Engineers). It was set up in Switzerland in 1955 to meet the 

increasing demand for unified contract documents that could be used in different countries 

without encountering problems in respect of local regulations and laws. 

The contract forms offered by the FIDIC are reliable, have no legal "gaps" and in particular 

have been tried and tested over the decades on thousands of different contracts. The first 

version dates from 1957. The latest, dating from 1999, includes for example environmental 

constraints and new arrangements for solving conflicts between the Employer and the 

Contractor. 





* The document proposed by the World Bank is much more recent (1997); it was based on 

a type of contract published by the Engineering Advancement Association of Japan, and 

initially prepared for turnkey contracts in which the Contractor is responsible for the entire 

project. It was therefore substantially modified by the World Bank to become Standard 

Bidding Documents. 

The result is a fairly "dense" document that it awkward to use and therefore generates 

much misunderstanding and discussion. 

Furthermore, with a view to being perfectly transparent, the Bank introduced complex 

payment clauses and procedures that make daily management heavier, thus causing 

possible difficulties in making payments to the Contractor, which in turn generates delays. 

The document proposed by the UNDP is dedicated mainly to civil works. It is a type of 

contract that is distinguished by its extreme flexibility of use. It handles all the major issues 

that a scheme of the Khan Younis WWTP type may generate while remaining at a 

relatively general level. For example, the amount of insurance and guarantees to be 

produced is not defined, "liquidated damages" are suggested only, price escalation 

conditions remain to be defined, etc. 

More importantly, it seems that the specific constraints and conditions connected with the 

commissioning of process installations (completion certificate, ramp-up, industrial start-up 

period, etc.) are hardly treated in this document, if at all. This will require the introduction of 

specific stipulations that risk creating uncertainties in applying the document in its entirety. 

Lastly, it seems that the UNDP library proposes only general conditions of contract. The 

other documents forming the contract (Conditions of Particular Application, Form of 

Contract or Contract Agreement) would thus need to be written, which also results in a 

certain degree of risk for future management. 

Finally, it seems that the UNDP document is well suited to medium-sized pure construction 

projects. 

It thus appears that the most appropriate form of contract is the FIDIC. 

* However, it is important to note that another type of contract has recently (2005) been 

published by the FIDIC in the name of the following group of banks, in order to harmonize 

the different contractual forms : 

- The World Bank 

- African Development Bank 

- Asian Development Bank 

- Black Sea Trade and Development Bank 

- Caribbean Development Bank 

- Council of Europe Development Bank 

- European Bank of Reconstruction and Development 

- Inter American Development Bank 

- Australia Aid 





Because of, a number of the Multilateral Development Banks (MDBs) have, for many 

years, adopted the FIDIC Conditions of Contract for Construction as part of their standard 

bidding documents (SBDs), which the MDBs require their borrowers or aid recipients to 

follow. In using the FIDIC Conditions, it has been the regular practice of the MDBs to 

introduce additional clauses in the Conditions of Particular Application in order to amend 

provisions contained in the FIDIC General Conditions. These additional clauses in many 

cases, which are specific to the MDBs, have standard wording which has had to be 

repeated whenever procurement documents have been prepared for a new project. 

Furthermore, the provisions in tender documents, including the additional clauses 

contained in the Particular Conditions, have varied between the MDBs. This has created 

inefficiencies and uncertainties amongst the users of the documents and increased the 

possibilities of disputes. 

These problems were recognised by the MDBs as significant, as were the benefits of 

standardisation. In response, the MDBs resolved to harmonise their tender documents on 

an international basis. For this purpose the MDBs resolved that there should be a modified 

form of the FIDIC Conditions of Contract for Construction, 1st Edition 1999 ("CONS1"), in 

which the General Conditions would contain the standard wording which previously had 

been incorporated by MDBs in the Particular Conditions. FIDIC is pleased to work with the 

MDBs in producing a special MDB Harmonised Edition ("CONS MDB") of the 1999 

conditions for MDB financed contracts. It was not intended to replace the standard 1999 

contract, which is still available to all users. 

The first version of the MDB Harmonised Construction Contract was released in May 2005 

and an amended second version in March 2006. 

We therefore feel it is justified and particularly appropriate to use the "Conditions of 

Contract for Construction for Building and Engineering Works designed by the Employer", 

issued by the FIDIC (Multilateral Development Bank Harmonised Edition, March 06). 

These conditions include a full set of documents, namely: 

- Form of contract 

- Letter of acceptance 

- Particular conditions 

- General conditions 

In addition, the schedules and any other documents (Specifications and Drawings) will be 

put of Contract. 

6.2. CONTRACT PACKAGING 

Whatever the selected biddings procedure, the contract packaging issue has to be 

analysed. 

A good contract packaging will allow to fulfil contracting constraints, namely: 

- To limit the risks of delays, 

- To optimize the overall cost of the project, 

- (Generally) to allow local contractors to bid, 

- To limit the risks of technical issues. 





Then, an analyse of so much constraints leads to the following elements: 

There are different parts in this project, with technical issues and risks totally different. 

First of all, it is obvious that the delivery pipe to the infiltration basins, the emergency pipe 

to the sea are a typical piping project; so it is normal to consider it is a single package. The 

discussion can be enlarged to two others items: 

- The pumping station upstream the pipe is sometimes linked to the pipe itself, 

because the hydraulic parameters inside the pipe depend on the characteristics of 

the pumping station (PS) itself; but here, it is quite different because the outlet PS 

is located inside the station and filters buildings (there are a lot of connections with 

the structure, including the electrical power) and because all parameters of both 

PS and pipes are defined in the current report ; therefore, there are no advantage 

to include this PS in the pipes contract. 

- The infiltration basins are largely earthworks and pipes works, i.e. works similar to 

the pipes lines themselves; in addition, the contractor’s means could be used for 

the basins excavation, before the trenches excavation (writing for the pipes 

delivery). So there is an actual advantage to join the pipes and the basins in the 

same works contract. 

Secondly, it is clear that the WWTP must be considered as a single package, in order to 

avoid general delays stemming from the delay of our specific Contractor; for the same 

reason, the contractor in charge of the civil works must be in charge of the equipment too. 

Finally, there is one specific item, which could be awarded to another specific contractor, 

namely the buildings works (administration buildings and workshop) ; in fact, there are 

many advantages to award separately these works : 

- Because they are only buildings, local Palestinian Contractor’s, with references in 

Buildings Construction, could bid directly for this part. 

- Consequently, the cost of this part should be lower than an award to a general 

contractor (for the whole plant) because the later will add a financial fee on these 

works. 

- These works are not similar with the process structures because they are mainly 

masonry works, without too much concrete, and finishing works; so, the means 

(staff, equipment and experience) are different. 

Then, as a conclusion, it is proposed to tender 4 different contracts: 

 

 

 

 

C1 Pressure lines – National Bidding, 

C2 WWTP (Process structure and appurtenant works) including Buildings 

(Administration Building and Workshop) – International Bidding, 

C3 Infiltration basins– National Bidding, 

C4 WWTP (Power connection line and substation) – Local award. 

Another aspect, related to the origin of Contractors must be questioned; it is obvious that 

the contract C2 WWTP must be awarded to an experienced international Contractor, with 

financial and means back up. 

But the contracts C1, C3 and C4 are not very specialized works, and it is possible that local 

Contractors have enough experience and means for performing these works in terms of 

duration and quality; so, they could be awarded to local Contractors. 





6.3. PLANNING 

The duration of the works is directly connected to some specific items, which govern in fact 

the most part of the works implementation, because they are on the critical path, namely : 

 

 

 

The length of pipes to laid, 

The global volume of concrete to cost, 

The global volume of earthworks to move. 

So, the estimation of the planning is directly limited to these items; then it is interesting to 

precisely analyse each of them. 

6.3.1. PIPES TO LAID 

In normal conditions, (i.e. soft ground and non-urban are), a western civil Contractor style 

is able to laid around 60m/d of cast-iron pipes with such 900m DI. Of course, due to the 

specific condition of the Gaza strip (old plant, difficulties for spare parts importation, 

possible difficulties for fuel, …) it is necessary to keep clearance and to select a lower 

figure, which can be defined as 50% of normal progress, i.e. 30 m/d. 

Then, taking into account an anticipate trenches excavation (2 months, i.e. # 1300 ml), the 

duration of pipes laying is roughly 1800 ml /30 = 600 days, i.e. around 20 months. 

After laying, the duration of backfill and reinstallement is roughly the same, but as a 

floating period. It must be highlighted that time for supplying the project is roughly 8 months 

(including factory, transport …). 

6.3.1.1. CONCRETE TO CAST 

The total volume of concrete to be cast is around 19 000 m 3 in total, from which 17 000 m 3 

are related to civil structures. 

Considering a batching plant and auxiliary equipment (crane, pump …) a capacity of 30 

m 3 /day (which is in fact an actual challenge) i.e. around 800 m 3 /m, the total duration of 

concrete costing is around 19 000/800 #24 months. 

This figure 5 on average, ranging from 300 m 3 /m for complex structures like the pretreatment 

and sand filters to 1000 m 3 /m for the aeration tanks. Then, in total, the duration 

of concrete casting is actually 19 months. 

The most important structures in terms of equipment fitting will be build at the beginning of 

the implementation in order to allow the equipment installation at the earliest. 

6.3.1.2. EARTHWORKS 

The total volume of earthworks is roughly: 

Excavation = 400 000 m 3 (from which 330 000 m 3 are from the infiltration basins), i.e.: 70 

000 m 3 on KYWWTP site 





Backfilling = 80 000 m 3 (from which 50 000 m 3 are on the infiltration basins, i.e. ≠ 30 000 

m 3 on the KYWWTP site. 

It is considered that an earthworks squad (including 1 excavator or/and 1 loader and 1 

truck) can handle and move in soft ground a daily volume of 800 m 3 /d in usual conditions 

(Western Europe), with close stockpiling. 

As previously for the pipes lagging, we apply a reduction ratio of 50% for taking account 

the particular conditions in Gaza strip, then 400 m 3 /d = 175 days. 

Considering 2 squads, the duration comes to roughly 3 months. 

For backfilling, it can be considered a 200 m 3 /d (including compacting along the structure), 

then also a 3 months duration for 30 000 m 3 . 

For the infiltration basins, we consider 3 squads in activity, i.e. 1200 m 3 /d. So, the total 

duration is 330 000/1200 = 275 days, i.e. # 11 months. 

In addition to the above criteria, we have considered the followings constraints: 

The supply of equipment and pipe to the site is estimated to 8 months including, from the 

purchase order: 

4 months for manufacturing, 

0,5 month for administrative clearance abroad and transportation to 

harbour, 

1 month for maritime transportation, 

0,5 month for administration clearance 

2 additional months for specific regulations and importation clearance at 

Gaza strip border. 

The mechanical equipment installation will take between 9 and 6 months to be done, 

The electrical and SCADA equipment installation will take around 3 months to be done, 

The completion tests (particularly for the whole plant) should take 0,5 month for the dry 

test, 0,5 month for development of the sludge bacteria and then 1 month for the completion 

tests themselves, i.e., 2 months in total. 

6.3.2. GENERAL IMPLEMENTATION SCHEDULE 

Considering these data, the attached general implementation schedule presents the 

followings mains concerns: 

- C 1: Pressures lines 

The total duration of works is 30 months; the time during which the pipes will be 

manufactured and supplied to the site is fully used for anticipated trenches excavation. 





- C 2: WWTP and Buildings 

The total duration of the works is 29 months; the largest task is the construction of the 

aeration tanks. 

In order to optimize the duration, the equipment installation starts as soon as a particular 

structure a building is completed, as it is usually made. 

- C 3: Infiltration basins 

The total duration of the works is 16 months. 

- C 4: WWTP Power connection 

The total duration of the works is 6 month. In order to assure power connection of the site 

during construction works, the power connection of the WWTP site should be finalized 

starting C2 on works site.

etailed Design Plain for the construction of Khan Younis ... - UNDP

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