USE OF A NEW ANAEROBIC-AEROBIC SEQUENCING BATCH REACTOR SYSTEM TO ENHANCE BIOLOGICAL PHOSPHORUS REMOVAL

A two-stage anaerobic-aerobic sequencing batch reactor (SBR) system (P AF-SBR) was developed to enhance biological phosphorus removal in the sequencing batch reactors. The system performance was evaluated agains t a conventional SBR system in parallel lab-scale reactors at room tem perature, using the degritted raw wastewater as the feed. The SRT for the anaerobic SBR which is named PAF (Primary Acid Fermenter) was 12 d ays, and for both the BNR reactors was 10 days. All reactors were run at 3 cycles per day. A significant difference (P=0.01) was observed be tween the performances of the two systems; The Ortho-P concentration i n the effluent from the PAF-SBR was mostly below 0.5 mg/L while in the conventional SBR was generally above 1.5 mg/L. Lack of availability o f carbon (mean VFA/P-Sol.=1.1) and long anoxic/anaerobic period were t he major causes of inefficient removal of phosphorus in the convention al SBR system. The use of anaerobic stage however increased the mean V FA/P-Sol. to 11.3 which enhanced Bio-P removal in the PAF-SBR system. Prefermentation also improved the sludge consistency and settleability in the following SBR unit. The results indicated that by using the pr efermentation step, the anoxic/anaerobic period in the BNR-SBR could b e controlled and reduced to less than 50 minutes, which would reduce t he total cycle time from 8 hr to 6 hr. Copyright (C) 1996 IAWQ.