Water Reuse at West Point Makes Dollars and Sense

A 500 gpm (0.72 MGD) water reclamation facility capable of producing Class A (Washington State Standards) reclaimed water was constructed at King County's West Point Treatment Plant with support from Seattle Public Utilities. The facility has been in operation since June of 1997. Major in-plant uses include polymer batching, pump seal water, various spray systems, hose bibs, boiler make-up and cooling. Reclaimed water was also used externally for irrigating new landscaping during 1998 and 1999 until the drought tolerant vegetation became established. Estimated savings on potable water costs from the use of the reclaimed water are 161,000 per year (0.42 average mgd used). Some operational problems have been encountered with chlorine residual analyzers and alum feed piping associated with the reuse facility; however these have been corrected. Operations and maintenance costs, including modifications to improve system reliability, have been tracked.Extensive microbiological and chemical testing has been conducted in addition to required compliance monitoring to provide product characterization data. Langelier index testing indicated that reclaimed was more aggressive than the potable water supply and the plant secondary effluent, and there was evidence of increased corrosion in cooling and boiler water make-up applications. This prompted a move away from use of alum as a flocculent in early 1999 and testing began using aluminum chlorhydrate and polyaluminum chloride solutions. Further Langelier testing suggests these flocculents contribute to a much less aggressive reclaimed product.