Biological nitrogen removal is becoming a proven approach to reducing the total nitrogen discharged from wastewater treatment facilities. Simulation performed with intermittent aeration-type activated sludge process using Activated Sludge Model No. 1 predicted that up to 90% total
nitrogen removal could be attained when the total cycle time and its anoxic phase were balanced adequately. This control limits electron donor and acceptor levels—ammonia-nitrogen (NH4+-N) in the aerobic phase and nitrate-nitrogen (NO3−-N)
in the anoxic phase. Specifically, maximum nitrogen removal appears to be achieved with a 2- to 3-hour cycle time, during which, anoxic conditions were present for 40 to 50% of the time. A 10- to 16-hour hydraulic retention time appears adequate to achieve these results. The solids retention
time studied was between 15 and 25 days, as this range was deemed sufficient to establish the nitrifying organism population in most applications. Predictions indicate that the conventional activated sludge system can be retrofitted for better nitrogen management at the treatment plants.
Water Environment Research® (WER®) publishes peer-reviewed research papers, research notes, state-of-the-art and critical reviews on original, fundamental and applied research in all scientific and technical areas related to water quality, pollution control, and management. An annual Literature Review provides a review of published books and articles on water quality topics from the previous year. Published as: Sewage Works Journal, 1928 - 1949; Sewage and Industrial Wastes, 1950 - 1959; Journal Water Pollution Control Federation, 1959 - Oct 1989; Research Journal Water Pollution Control Federation, Nov 1989 - 1991; Water Environment Research, 1992 - present.