Views
9 months ago

galvis

Water treatment

Previous observations

Previous observations were further considered by taking samples simultaneously from Q i , Q f , and Q e and finding connections between remaining weight fractions of particles (Fw) and distribution of settling velocities (V s ) using column settling tests (CST). The columns were made of Plexiglas having 0.30-m diameter and 1.0 m depth with four sampling ports located at 0.26, 0.46, 0.61 and 0.71-m below the water surface. The values of Fw are calculated as C i /C 0 where C 0 is the initial SS concentration in Q i at t=0 and C i are the measured values at different times and depths during the CST. Figure 3.16 illustrates the typical pattern of Fw and V s based on data produced with Qi, Qf and Qe samples taken from a filter run identified as 1(A) in table 3.13. Remaining weight fraction Fw (%) 100 80 60 40 20 0 0 20 40 60 80 Settling velocity, Vs in cm.s -1 x10E -3 Qi Influent Qf Filtered effluent Qe Overflow Figure 3.16 Settling velocity curves of samples taken from Q i , Q f and Q e of a DyGF unit with 0.75 m 2 of surface filtering area and working with Qi=4 m 3 h -1 (1.1 ls -1 ) and initial filtration rate of 2.0 mh -1 . All Fw values calculated with respect to initial SS concentration (C 0 ) in Q i (Based on Latorre, 1994; Latorre et al, 1996). On the basis of figure 3.16 it may be concluded that very small differences exist between the Fw values in the curves for Qi and Qe at each settling velocity. The Fw values associated with Qi are normally greater than those associated with Qe but most of their differences are in the range of 0 to 10%. Both, Qi and Qe show a remaining weight fraction Fw close to 45%, with Vs≤ 5.0x10 -3 cms -1 . Only 20 to 30% of the initial SS concentration C 0 remains in the filtered water, thus indicating the impact of DyGF on suspended solids reduction. The mean density of Cauca river water solids removed on top of the gravel bed of DyGF units was 1564 (SD=78.2) kgm -3 . At least for these solids, the results in table 3.13 and figure 3.16 indicate that overflow in DyGF is neither playing any role in improving SS removal efficiencies nor contributing to reducing partial cleaning frequencies by scouring and transporting away removed solids from the top of the gravel beds. Therefore overflow can be eliminated as a normal hydraulic element in DyGF operation, but including a shallow overflow weir (2 to 5 cm from the gravel bed surface to the crest of the weir) at the end of the filtering box of DyGF (see Annex 1, figure A1-2). This shallow weir should behave as a “ safety valve” by allowing overflow during abrupt water quality changes, with high SS concentration, and keeping the possibility of applying the concept of protection capacity discussed before. DyGF 101

units designed with this criterion will work at constant filtration rates until headloss in the gravel bed becomes greater than the height of the overflow weir. Afterwards the units will work at declining rate filtration, as initially proposed (Galvis, 1983; Galvis and Fernandez, 1991). Influence of initial filtration rates on solids distribution in gravel bed layers of DyGF units. Removed solids in DyGF units should concentrate in the top gravel layer or at the bottom, close to the drainage system, to increase the impact of partial cleaning activities and the length of total cleaning cycles. Sludge accumulated in the gravel layers was measured at the end of filtration runs 1A to 3A. figure 3.17. These results complement the observations at higher initial filtration rates (3.1, 3.7 and 4.8 mh -1 ), keeping Q i in the range of 4.3 to 5.6 m 3 h -1 (1.2 to 1.7 ls -1 ). Performance of the DyGF units at these higher filtration rates is summarised in table 3.14. Table 3.14. Performance of DyGF units with similar influent and different filtration rates. Filtering surface area of 0.75 m 2 (Based on Latorre, 1994). Run (filter unit) Raw water SS (mgl -1 ) Mean ± SD Run length (days) Q i Flow (m 3 h -1 ) Filtration rate Q e (overflow) (mh -1 ) (range) Initial Final Initial Final Filtered SS (mgl -1 ) Mean ± SD Overflow SS (mgl -1 ) Mean ± SD 3.B 406 ± 172 3 5.0 – 5.6 2.7 5.8 3.1 0.2 62 ± 73 348 ± 128 4.A 424 ± 161 3 4.3 – 5.0 1.6 4.9 3.7 0.2 129 ± 83 355 ± 131 4.B 125 ± 21 6 5.0 – 5.6 1.8 5.0 4.8 0.0 46 ± 14 104 ± 18 Testing period: January 4 – April 7 1994. Figure 3.17 A and B show weight fraction distributions of accumulated sludge in each gravel layer after filtration runs included in table 3.13 and 3.14 respectively. With initial filtration rates in the range of 1.8 to 2.1 mh -1 (figure 3.17 A) solids accumulated mainly (81%, SD = 9%) in the upper gravel layer. The intermediate and bottom gravel layers stored 11% (SD = 4%) and 9% (SD = 6%) of removed solids respectively. 100 100 Stored sludge weight fraction Fw(%) A 80 60 40 20 0 1 2 3 Gravel layers (1,2,3) Qei=1.0m h Qei=2.5m h Qei=4.0m h Qei=5.8m 3 h -1 Qei=7.3m 3 h -1 3 -1 3 -1 3 -1 Stored sludge weight fraction Fw (%) B 80 60 40 20 0 1 2 3 Gravel layers (1,2,3) Vf = 3.1 mh -1 Vf = 3.7 mh -1 Vf = 4.8 mh -1 Figure 3.17. Weight fractions of stored solids in top (1), intermediate (2) and bottom gravel layers of DyGF units with initial filtration rates (Vf) in the range of 1.8 to 2.1 mh -1 (A) and 3.1 to 4.8 mh -1 (B) (Based on Latorre, 1994 and Latorre et al, 1996). A similar trend (of removed sludge distribution between the gravel layers) to that observed with the previous range of initial filtration rates (1.8 – 2.1 mh -1 ) was found at higher filtration 102

Screen Filtration for Ballast Water Treatment Applications - Cross ...
Water Treatment Improvements and Plant Capacity ... - Ohiowater.org
Pall Aria™ AP-Series Packaged Water Treatment ... - Pall Corporation
Pall Aria™ AP-Series Packaged Water Treatment ... - Pall Corporation
Precursor Removal from Ground Water Using GAC ... - Ohiowater.org
The Treatment of Scottish Water for Private Communities
Water Treatment Products - Colorfil
Pilot Testing and Evaluation of Three Filtration Technologies - pncwa
Microorganisms (The Coliform Group Bacteria)
Capacity Charts for Water Treatment Systems
Water Quality Report - 2010 - Presidio Trust
may 4th am water treatment.pdf(18358.4kb) - PNWS-AWWA
The best solutions in water treatment - Istobal
krones Hydronomic Water treatment for all areas of ... - Krones AG
Meshing Treatment Objectives, Water Quality Goals ... - Ohiowater.org
2003 City of Roanoke Water Quality Report - Western Virginia Water ...
Council Bluffs Water Works South Water Treatment Plant – Planning ...
Waste water treatment without chemistry Atec Advanced Oxidation ...
Technical Advances in the Treatment of Water and Air for ... - IAAPA
ZTF Filter Catalog - ZEKS Compressed Air Solutions
FILTRATION - Environmental Protection Agency
Filter housings catalogue
Chemicalfree Water Treatment - Necon
Weatherford in Waste Water Treatment (WWT)
Commercial water treatment solutions - CMS
Evaluation of Treatment Options for the Raspberry ... - Loudoun Water