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This paper describes innovative design concepts used for the 20-mgd immersedmembrane water treatment plant under construction for the Westchester Joint WaterWorks (WJWW), at Rye Lake, New York to afford water treatment process flexibility, whileenabling the plant to meet stringent disinfection byproduct (DBP) regulations and minimize operational costs.Raw water quality from Rye Lake is typically very good and the plant design allowswater to be fed directly to the membranes. Alternatively, the raw water can becoagulated and flocculated prior to the membranes in dual-purpose tanks.To enable side-by-side comparison, two different membrane systems are being suppliedby the vendor, Zenon Membrane Solutions, ZW500d with a large diameter fiber and lowpacking density and ZW1000 with a finer fiber and a higher packing density.To improve performance, both membrane systems use periodic solids removal by tankdrain, rather than the "feed and bleed" method used previously by the membrane systemvendor. Implementing this solids removal method presented significant designchallenges.To reduce overall power consumption, individual permeate pumps that create theoperating vacuum for the membranes have been replaced by siphons located in anequalization tank. A small number of efficient vertical turbine pumps transfer water fromthe wet well to the clearwells. Additionally, the membrane tanks are aerated by efficientpositive displacement blowers and the control system for these blowers incorporates twomodes of operation, air cycling and intermittent air operation. Includes tables, figures.

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Edition: Vol. - No. Published: 03/01/2007 Number of Pages: 13File Size: 1 file , 500 KB