High Biosolids Costs? – Reduce Volume, Starve the Bugs!
Abstract:The Springfield Water and Sewer Commission (SWSC) operates a 67 million gallons per day (MGD), regional activated sludge wastewater treatment facility (SRWTF) located on Bondi's Island in Agawam, Massachusetts. The facility began secondary treatment in 1977 and recently upgraded its mechanical, surface aeration system to fine bubble diffusion through a 10.8 million dollar SRF loan.
Over the last few years the SWSC has been developing a more competitive operation at the SRWTF. One major component is cost reduction, especially for Biosolids management which normally represents about 50% of a facility's budget. The new aeration system provides process flexibility to address secondary sludge production issues, which are an important part of the longterm Biosolids management program. Secondary sludge dewaters poorly; is unstable with respect to organics, oxygen demand, and odors; and is expensive to manage.
As part of the short-term Biosolids program, it was decided to examine cost reductions associated with lower waste activated sludge WAS production levels and associated downstream solids handling. Equipment and process modifications were made to the secondary system to allow operation in the traditional extended aeration range of organic and solids loadings, i.e. long solids retention times (SRT). The presentation will discuss the following aspects of the two year field study:
equipment modifications necessary for higher final clarifier solids loading rates (SLR)
changes in microbiology at mixed liquor suspended solids (MLSS) levels of 4000 mg/l and SRT values of fifteen (15) to twenty-five (25) days
operational procedures developed for high flow, wet weather operation
reductions in WAS volumes and associated savings in solids management costs
dewatering improvements resulting from improved primary/secondary sludge ratios
seasonal effects involving foaming and settling
Document Type: Research Article
Publication date: January 1, 2001
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