DEVELOPMENT OF 2-REACTOR INTERMITTENT-AERATION ACTIVATED-SLUDGE PROCESS FOR SIMULTANEOUS REMOVAL OF NITROGEN AND PHOSPHORUS

We have developed a new intermittently aerated anaerobic-aerobic activ ated sludge process. This process employs 2 reactors connected in seri es, and is capable of controlling the duration of aerobic, anoxic and anaerobic conditions in both reactors by utilizing the ORP bending poi nt, which corresponds to the termination of denitrification. One cycle of aeration and agitation takes approximately 120 minutes. In the Ist reactor, nitrification and phosphorus uptake occur in the aeration pe riod, followed by denitrification and phosphorus release in the agitat ion period. In the 2nd reactor, nitrification and phosphorus uptake ar e conducted during aeration, and denitrification and weak phosphorus u ptake during agitation. A one-year pilot plant experiment using sewage (22 m(3)/day) showed stable and high removal ratios of 98% for BOD, 9 2% for T-N, and 85% for T-P under conditions of HRT 20 hours and water temperature 9-33 degrees C. Copyright (C) 1996 IAWQ.