Step-feed operation at short detention times – a cost effective method for improving wastewater treatment

Abstract

The Newtown Creek Water Pollution Control Plant (WPCP) is New York City's largest wastewater treatment plant. Wastewater treatment is provided by a high-rate activated sludge process without primary sedimentation. This process has achieved approximately 65 percent BOD5 and 75 percent TSS removal. As part of a revised facility plan, two alternative tracks were recommended for upgrading the plant to secondary treatment and providing nitrogen removal. One track would require demolishing most of the existing tankage and constructing new primary tanks followed by a step-feed biological nitrogen removal activated sludge process. The second track would preserve the existing high-rate activated sludge process and use biological filters to remove additional TSS, BOD5 and nitrogen. Alternatives have been investigated to enhance treatment at the Newtown Creek WPCP while the secondary treatment plant upgrading is being completed. This investigation demonstrated that simply converting the existing aeration tanks to step-feed operation could significantly improve TSS and BOD removals. These findings have led the City to consider a third track to meet secondary treatment requirements, (but with no nitrogen removal), consisting of modifying the existing plant to step-feed and adding additional step-feed aeration/sedimentation capacity. This track offers significant cost savings over Track 1 and Track 2.