Sturbridge, Massachusetts historically suffered from periodic blooms of filamentous bacteria that caused bulking in the secondary clarifiers of their three activated sludge package plants. The elevated clarifier solids loading rates (SLR) during high flow events often caused excessive sand filter backwash cycle times and occasional diversion of excess flow to a neighboring publicly owned treatment works (POTW). Sturbridge’s need for additional treatment capacity in a highly constricted footprint, coupled with tighter permit limits for BOD, TSS, total nitrogen (TN) and phosphorus (TP), created the need to upgrade the wastewater treatment plant.
Innovative Technology Creates a More Cost-Effective Solution
Initially, Sturbridge considered installing a membrane bioreactor (MBR) system to achieve the required limits on contaminant removal and deliver the additional capacity needed without expanding the footprint of the plant.