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# galvis

Water treatment

## Annex 2: Design of

Annex 2: Design of Manifolds Manifolds consist of a main pipe with orifices lateral pipes, which are usually placed at regular intervals. The layout should ensure an equal distribution of flow to establish the best possible hydraulic behaviour of the tank or reactor in which the manifold is being installed Two principal systems exist: dividing-flow manifolds that are used to distribute a liquid in a filter medium or tank, and collecting-flow manifolds, which abstract a liquid from a filter medium or tank, ensuring a uniform abstraction. Some manifolds are designed to comply with both functions, as is the case with drainage systems in rapid sand filters and upflow gravel filters. Due to the lack of a straightforward calculation method, manifold design is often neglected. As a result many treatment plants show poor hydraulic performance and have low efficiency levels. Hudson (1981), on the basis of experiments of other researchers (e.g.McNown, 1954; Vennard and Dentoni (1954), developed equations which permit the calculation of the headloss coefficients in the orifices or lateral pipes. These coefficients can be calculated for both types of manifolds, taking into account the lateral entry losses but not the friction losses. In an upflow gravel filter, a manifold system is used which combines both functions. The system acts as a dividing-flow manifold under normal operating conditions and as a collecting-flow manifold when being drained for cleaning. Under normal operating conditions low flow velocities are used (0.6 mh -1 ) and thus manifold design is not critical as the gravel bed also ensures uniform distribution of flow. When the filter is being drained flow velocity is considerably higher (10 to 20 mh -1 in the present study) and therefore manifold design becomes critical. The following sections will focus on collecting-flow manifold option. A.2.1. Collecting-manifold hydraulics In this section the equations presented by Hudson (1981) are used to establish a design procedure for collecting-flow manifolds (figure A2-1). The following assumptions are made: • The surface area in the manifold main remains constant before and after a branch section. • The laterals are connected under a 90-degree angle with the manifold main. • The laterals are circular and connected to the manifold main without extending into its interior. Figure A2-1: Hydraulic conditions in a collecting-flow manifold The collecting flow manifold is the opposite of the dividing-flow manifold, with the flow in the beginning of the manifold main being smaller than at the end. The water level at the entry side of the outlet ports in a given treatment unit is the same for all ports. With sharp edged ports there is an entry loss (∆h) of ’ 0.4 to 0.5 lateral velocity heads, which is not included in the headloss h f in equation A2-1. There is, A2-1

however, some recovery of velocity head, which ranges from: (a) nearly none when the collecting conduit velocity is small compared to the port velocity; to (b) complete recovery when the conduit velocity (V M ) equals or exceeds about 1.5 times the lateral velocity (v L ). This relationship is shown in figure A2-2. Rather than representing a head loss, equation A2-1represents that part of the port velocity head that is not recovered. Figure A2-2: Headloss coefficient of laterals discharging into a collecting-manifold main (Hudson, 1981). α = ⎛ ⎜ ⎝ hf 2 V L ⎞ 2 ⎟ g ⎠ = ⎛ V 1- 0.7⎜ ⎝ V M L ⎞ ⎟ ⎠ 0.5 ⇒ h f ⎡⎛ V ⎢⎜ ⎛ = 1- 0.7⎜ ⎢⎜ V ⎣⎝ ⎝ M L ⎞ ⎟ ⎠ 0.5 ⎞ ⎟ ∗ ⎟ ⎠ V 2 L 2g ⎤ ⎥ ⎥ ⎦ (A2 - 1) Hf = ∆h + h f ⇒ 2 L V Hf = 0.5 2g + ⎡⎛ V ⎢⎜ ⎛ 1- 0.7⎜ ⎢⎜ V ⎣⎝ ⎝ M L ⎞ ⎟ ⎠ 0.5 ⎞ ⎟ ∗ ⎟ ⎠ V 2 L 2g ⎤ ⎥ ⎥ ⎦ Hf = ⎡⎛ V ⎢⎜ ⎛ 1.5 - 0.7⎜ ⎢⎜ V ⎣⎝ ⎝ M L ⎞ ⎟ ⎠ 0.5 ⎞ ⎟ ∗ ⎟ ⎠ V 2 L 2g ⎤ 2 ⎛ V ⎞ L ⎥ ⇒ Hf = β ⎜ ⎟ , ⎥ 2g ⎦ ⎝ ⎠ ⎛ VM ⎞ Where β = 1.5 - 0.7⎜ ⎟ ⎝ VL ⎠ 0.5 (A2 - 2) Considering that ß n = 1.5 for the lateral (n) furthest away from the outlet (where V M ≅ 0), and that ß is given by equation (A2-2) for other laterals, the following equations are derived ( ) 2 2 1.5 qn/a (q1/a) Hfn = , and Hf1 = ß1 2g 2g Accepting a 20% difference in flow distribution between the first and the last (n) lateral (orifice), implying that q 1 = 1.2 q n , and neglecting friction loss (H 1 = H n ): 2 2 1.5 (qn/a) (q1/a) 2 2 2 2 = ß1 ⇒ 1.5 (qn) = ß1(q1) ⇒ 1.5 (qn) = ß1(1.2 qn) ⇒ 2g 2g 1.5 ß = 2 1.2 1 = 1.042 (A2 - 3) A2-2

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Development and Evaluation of Multi

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ACKNOWLEDGEMENTS To my supervisor,

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ABBREVIATIONS ABNT: Acuavalle: ACV:

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SOCs: Synthetic Organic Chemicals S

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u c V V f Vs uniformity coefficient

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4 MULTISTAGE FILTRATION EXPERIENCIE

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1 INTRODUCTION Water is essential f

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Table 1.5 Safe drinking water cover

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1.2 Multiple Barriers Strategy and

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2 OVERCOMING THE LIMITATIONS OF SLO

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On January 14, 1829, Simpson’s on

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With increasing life expectancy, en

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Table 2.2 Treatments steps recommen

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In table 2.3, WHO guideline values

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2.5 The Slow Sand Filtration Proces

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When the particles are very close t

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in which p 0 is the clean media por

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Yao et al (1971) related the remova

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compensate for the increase in the

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can be applied, but intermittent op

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Table 2.4 Comparison of design crit

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Although accepted as indirect indic

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50% when the temperature falls from

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Figure 2.9 Flow diagram of the wate

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ut higher running costs, since more

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Headloss and flow control. Final he

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Figure 2.13 Influence of flow condi

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Operation and maintenance (O & M).

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in parallel (Galvis, 1983; Smet et

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cleaning simple, DyGF should behave

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case of Dortmund (Germany), the HGF

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Table 2.9 Data about three experien

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Some points of discussion about HGF

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and 600-800 NTU) and different filt

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the HGF units of Aesch (see table 2

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in spite of the low removal efficie

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order to overcome the water quality

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full-scale units. In this research,

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3 MULTISTAGE FILTRATION STUDIES WIT

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in the case of UGFL. Initially, it

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• Bigger and better-instrumented

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l Figure 3.7 Plan view of Cinara's

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The present research work was divid

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Table 3.1. Design parameters, grave

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Figure 3.9. Piezometer distribution

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were used to collect samples for DO

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were poured into a funnel using fil

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H 0 : H a : Treatment levels workin

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3.2 Results and Specific Discussion

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3.2.2 Dynamic gravel filtration (Dy

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Mean faecal coliform removal effici

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Table 3.10 Comparative analysis of

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DyGF-A had flow reductions in the r

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The experimental data used to produ

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Previous observations were further

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ates (figure 3.17 B). However, at t

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Longer “initial-ripening” perio

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Table 3.17. Descriptive statistics

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100 Filtration rate = 0.3 mh -1 100

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After the present experience, faeca

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nature of the organic matter and th

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Table 3.24 Comparative analyses of

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3.2.4.3. Filtration run lengths and

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deep bed filter (data not included

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and operational considerations Pard

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than in sand samples from other SSF

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Step dose tracer tests were made at

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for HGFS and from 3 to 5 for HGF. T

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Constant and declining filtration r

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The efficiency levels summarised be

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Surface area of CGF and SSF units.

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community based organisations and l

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systems. All these systems were fed

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Parts of the suburban settlements o

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Figure 4.2. Layout of Retiro MSF pl

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Traditionally, in the WS&S of Colom

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Photo 4.10. Partial cleaning activi

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Figure 4.3 Location of full-scale M

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4.4.1.3 Main characteristics of mul

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Figure 4.4 Layout of Restrepo MSF p

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Figure 4.6 Layout of Javeriana MSF

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Figure 4.9 Layout of Cañasgordas M

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Figure 4.11. Layout of Ceylan MSF p

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Table 4.4 Descriptive statistics fo

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Water sources in the coffee region

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Filterability results seem to under

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Table 4.8 Mean removal efficiencies

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The length of this ripening period

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in Peru (Pardon, 1989) and Colombia

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Photo 4.24 Drainage facilities in u

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the Cauca Valley. This is not the c

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Pardon (1989) reports similar evide

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5. COST OF MULTI-STAGE FILTRATION P

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ecame formally established as WS en

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Models for assessing construction q

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• Page 204 and 205: 5.7 Cost Model for the Cali Area an
• Page 206 and 207: Table 5.8. Annual labour costs due
• Page 208 and 209: 5.8 General Discussion The followin
• Page 210 and 211: systems. The differences between MS
• Page 212 and 213: guideline for colour is < 15 PCU (W
• Page 214 and 215: Table 6.1. Individual (at each trea
• Page 216 and 217: Table 6.3. Individual (at each trea
• Page 218 and 219: As shown in tables 6.1 and 6.3, col
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• Page 222 and 223: Table 6.4. An example of identifica
• Page 224 and 225: MSF technology showed great flexibi
• Page 226 and 227: In harmony with the new development
• Page 228 and 229: epresents the risk the community ha
• Page 230 and 231: The selection of MSF alternatives i
• Page 232 and 233: scouring and transporting away prev
• Page 234 and 235: REFERENCES ABNT, (1989) NB-592 Proj
• Page 236 and 237: Craun, G.F., Bull, R.J., Clark, R.M
• Page 238 and 239: Drinking Water Disinfection, ed. by
• Page 240 and 241: Huisman, L. (1989) Plain Sedimentat
• Page 242 and 243: Mendenhall, W. and Sincich, T. (199
• Page 244 and 245: Ridley, J.E. (1967) Experience in t
• Page 246 and 247: Visscher, J.T. and Galvis, G. (1992
• Page 248 and 249: ANNEXES Annex 1: Accessories for Mu
• Page 250 and 251: aw water. The red colour is used fo
• Page 254 and 255: + q 2 Q1 (1.2 qn + qn) (2.2 qn) = =
• Page 256 and 257: R 1 = (total orifice area / lateral
• Page 258 and 259: 0.30 0.25 0.20 0.15 0.10 0.05 0.00
• Page 260 and 261: Table A.4-2 General notation for th
• Page 262 and 263: Box A4-3. Sum of Square Error (SSE)
• Page 264 and 265: Annex 5: Residence times in coarse
• Page 266 and 267: Table A5-1 Percentage of incoming w
• Page 268 and 269: Annex 6 Number and Type of Valves N
• Page 270: Table A7-1. Descriptive statistics
• Page 274 and 275: Tables A7-3 Removal efficiencies of
• Page 276 and 277: Tables A7-5 Removal efficiencies of
• Page 278 and 279: Construction quantities of DyGF com
• Page 280: Net present value (US\$) of MSF and
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