Method Development for Determining the Biodegradability of Dissolved Organic Nitrogen in the Stamford WPCA Effluent

Wastewater treatment plant data from the City of Stamford, CT Water Pollution Control Authority (SWPCA) indicate that dissolved organic nitrogen (DON) can make up half of the effluent total nitrogen (TN). It is believed that most of the effluent DON is not biodegradable or recalcitrant (rDON) and that the fraction that is biodegradable (BDON) may change with process parameters. A method was developed to measure the biodegradability of DON in the SWPCA plant effluent. It consists of batch experiments in which filtered final effluent is seeded with a mixed liquor inoculum and incubated over a 30-day period. Results using the methodology developed indicate that effluent BDON may be a function of sludge retention time (SRT) and/or temperature in the activated sludge process. Ongoing work will help refine the methodology and help verify DON sources and the impacts of these process parameters on the biodegradability of DON in the plant effluent.