High Biosolids Costs? – Reduce Volume, Starve the Bugs!

The Springfield Water and Sewer Commission (SWSC) operates a 67-MGD, regional activated sludge wastewater treatment facility (SRWTF) located on Bondi 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 long-term solids management program. Secondary sludges dewater poorly; are unstable with respect to organics, oxygen demand, and odors; and are expensive to manage.As part of the short-term biosolids program, it was decided to examine cost reductions associated with lower waste activated sludge production levels and downstream solids handling. Equipment and process modifications were made to the secondary system to allow operation in the extended aeration range of organic and solids loadings. The presentation will discuss the following aspects of the two year field study:equipment modifications necessary for higher clarifier solids loading rates (SLR)changes in the microbiology at MLSS levels up to 5000 mg/l and solids retention time (SRT) values of 20 to 30 daysoperational procedures developed for high flow, wet weather operationsignificant reductions in waste activated sludge (WAS) volumes and associated savings in biosolids management costsdewatering improvements resulting from improved primary/secondary sludge ratiosseasonal considerations and effects