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Secondary Settling Tank Inlet Design: Full Scale Test Results Lead To Optimization

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Many of the activated sludge and trickling filter plants in operation today are capacity limited by the performance of their secondary settling tanks (SST). A large percentage of these in turn are circular or square, center-feed units. Adding a tank to increase capacity at a large plant could easily cost 1-2 million or more. Such an additional unit could also require changes in yard piping and the RAS pump station, as well as take up valuable footprint area. Recent full-scale research at Hyperion showed that a relatively inexpensive modification to the clarifier inlet design resulted in doubling the tank's capacity. This paper presents a review of inlet designs, gives a hypothesis as to why some inlets are so much more effective than others, and shows data compiled from several full-scale test projects. The results suggest that designs emphasizing impingement for energy dissipation and flocculation are superior to others.

Document Type: Research Article


Publication date: 2002-01-01

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