PILOT TESTING OF HIGH RATE PHSICAL-CHEMICAL TREATMENT (HRPCT) FOR WET WEATHER TREATMENT

This paper presents the results of pilot testing of high rate physical chemical treatment (HRPCT) technologies in New York City at the 26th Ward wastewater pollution control plant (WPCP) during the summer of 1999. The US Filter/Microsep Ballasted Floc Reactor™ (BFR), the Actiflo™ from Krüger Inc. and the Densadeg 4D™ from Ondeo Degremont Inc. were evaluated by Hazen and Sawyer for the New York City Department of Environmental Protection (NYCDEP). The pilot units treated primary effluent, which was used to simulate combined sewer overflow (CSO) quality due to the limited pilot period, the difficulties in predicting wet weather events, and the ability to staff the units outside normal working hours. Process performance was measured in terms of effluent concentration and percent removal for TSS and BOD5 as well as time to achieve full performance after start-up (start-up time).Pilot testing was successful and showed that HRPCT is a compact technology that would be well suited for the treatment of CSO. All units performed well when operating was optimized, removing between 69% and 84% of TSS on average. In addition, testing provided information on hydraulic loading, chemical dosage rates, recirculation rates, ballast dosage rate, operating ranges, as well as time to full performance after start-up and sludge quality. Due to short testing period and scale up issues with the pilot test, some operational aspects require further evaluated before proceeding to full-scale design. NYCDEP is currently designing a full scale HRPCT demonstration facility to further evaluate the technology.