STEP -FEED OPERATION AT SHORT DETENTION TIMES - A COST EFFECTIVE METHOD FOR IMPROVING WASTEWATER TREATMENT

摘要

The Newtown Creek Water Pollution Control Plant (WPCP) is New York City's largestrnwastewater treatment plant. Located on a 21.3 hectare (53 acre) site in Brooklyn, thernNewtown Creek WPCP treats an average annual flow of 12.5 cubic meters perrnsecond (285 MGD) from a combined sewer service area of 67.8 square hectare (25.4rnsquare miles), encompassing portions of Brooklyn, Queens and Manhattan.rnWastewater treatment is provided by a high-rate activated sludge process withoutrnprimary sedimentation. Biosolids are gravity thickened, digested and barged offsiternfor dewatering and further processing. This process has achieved approximately 65rnpercent BOD_5 and 75 percent TSS removal. As part of a revised facility plan, twornalternative tracks were recommended for upgrading the plant to secondary treatmentrnand providing nitrogen removal. One track would require demolishing most of thernexisting tankage and constructing new primary tanks followed by a step-feedrnbiological nitrogen removal activated sludge process. The second track wouldrnpreserve the existing high-rate activated sludge process and use biofilters to removernadditional TSS and BOD_5 and nitrogen by nitrification and denitrification.. Alternativesrnwere investigated to enhance treatment at the Newtown Creek WPCP while thernsecondary treatment plant upgrading is being completed. Four of the sixteen processrntrains were isolated and used to test different methods for enhancing treatment. Thisrninvestigation demonstrated that simply converting the existing aeration tanks to stepfeedrnoperation could significantly improve TSS and BOD removals. These findingsrnhave led the City to consider a third track to meet secondary treatment requirements,rn(but with no nitrogen removal), consisting of modifying the existing plant to step-feedrnand adding additional step-feed aeration/sedimentation capacity. This track offersrnsignificant cost savings over Track 1 and Track 2.