Effects of Temperature and Mean Cell Residence Time on Enhanced Biological Phosphorus Removal

Abstract

The effects of temperature and mean cell residence time (MCRT) on biological phosphorus and nitrogen removal were investigated by operating pilot-scale continuous-flow activated sludge reactors over a range of temperatures and MCRTs. Two reactors were operated as high-rate Virginia Initiative Plant (VIP) biological nutrient removal (BNR) processes, and a third was operated as a conventional, fully aerobic activated sludge process for comparison. The BNR systems were operated at MCRTs of both 5 and 15 days, while the conventional system was operated at an MCRT of 5 days at temperatures of 10, 15, and 20°C. Decreasing temperatures had an adverse effect on the performance of enhanced biological phosphorus removal (EBPR), with 5-day MCRT being more affected than 15-day MCRT. Operation at 5-day MCRT and 10°C resulted in a washout of organisms responsible for EBPR. Nitrification, however, was more sensitive to washout than was EBPR under all experimental conditions.