Odor Emissions From Biological Nutrient Removal Processes

As phosphorus and nitrogen limits become more stringent in NPDES permits, many treatment facilities are converting from the conventional activated sludge process to a biological nutrient removal (BNR) process. The BNR process typically incorporates selector, anaerobic and/or anoxic zones prior to the aerobic zone. In some cases, post (secondary) anoxic and re-aeration (final aerobic) follow the initial aerobic zones.Based on numerous odor evaluation studies of facilities using conventional activated sludge and those using the BNR process, the odor emission rates can differ significantly. This paper will present dilution to threshold ratios (DT) and odor emission rates (OER) for facilities with conventional activated sludge and those employing the BNR process.