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Phased Activated Sludge Concept Retrofitted for Compliance With Chesapeake Bay Nutrient Reduction Initiative

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The phased activated sludge system (PASS) was retrofitted into existing treatment structures at the Salisbury WWTP to achieve biological nutrient removal (BNR) in response to the Chesapeake Bay Initiative. The PASS schematic integrates return activated sludge (RAS) phase separation with attributes of sequencing batch reactor (SBR) and multi-stage conventional activated sludge (MSCAS) technologies offering temporal and spatial process control. The PASS arrangement reduced biochemical oxygen demand (BOD5), total suspended solids (TSS) and ammonia nitrogen (NH3-N) by more than 98%. Oxygen uptake rate (OUR) dependent transitional periods were used to separate aerobic and anoxic events to administer nitrification and denitrification within a single reactor. In situ TSS and nitrate (NO3) analyzers were used to register causal responses to operational changes. Effluent total nitrogen (TN) levels below 5 mg/l and total phosphorus (TP) concentrations below 0.4 mg/l were demonstrated without secondary filtration or supplemental carbon addition.

Keywords: Biological Nutrient Removal; Chesapeake Bay Initiative; Denitrification; Phase Separator; Phased Activated Sludge; Total Nitrogen; Total Phosphorus

Document Type: Research Article


Publication date: 2009-01-01

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