Evaluation of the parameters affecting nitrogen and phosphorus removal in anaerobic/anoxic/oxic (A/A/O) biological nutrient removal systems

Abstract

Considerable research has been performed on biological nutrient removal (BNR) systems which remove the problematic nutrients, nitrogen and phosphorus, that cause eutrophication. This research focussed on setting up two laboratory-scale anaerobic/anoxic/oxic (A/A/O) systems and investigating their reliability while undergoing various parameter changes. Pump failure, in the ®rst trial, R1, led to a decrease in pH, exposure of the sludge to relatively low nitrate concentrations and reduction of the suspended solids concentration within the system. This adversely affected the phosphorus removal ef®ciency. Shock loading the system with increased in¯uent phosphate concentrations for 56 days was shown to aid remediation of the phosphorus removal ef®ciency to values between 65 and 70% (w/w). The second trial, R2, highlighted the presence of bacteria capable of P-uptake under anoxic conditions (in the presence of nitrate). The characteristic anaerobic P-release was also evident. The bacteria responsible for phosphate uptake under anoxic conditions are thought to be the denitrifying phosphate removing bacteria (DPB). However, the presence of higher nitrate concentrations retarded the P-removal ef®ciency to some extent. Secondary release of P was evident in the clari®er of the A/A/O system during the R2 trial and especially during times of increased nitrate concentrations in the system. Between 20 and 40% (w/w) of the P taken up in the oxic stage of the system was released in the clari®er at various stages throughout the trial.

Mathematical Modelling and Computer Simulation of Activated Sludge Systems

“…Schonberger 1990;Wouters-Wasiak et al 1996;Mulkerrins et al 2000;Hughes et al 2004;Batista et al 2005;Barnard and Abraham 2006;Mikola et al 2009) Substantial amounts (up to 60%) of the phosphate taken up in the aerobic stage of the bioreactor were subsequently released in the clarifier. Schonberger 1990;Wouters-Wasiak et al 1996;Mulkerrins et al 2000;Hughes et al 2004;Batista et al 2005;Barnard and Abraham 2006;Mikola et al 2009) Substantial amounts (up to 60%) of the phosphate taken up in the aerobic stage of the bioreactor were subsequently released in the clarifier.…”

Enhancement of pollutants removal from real sewage by embedding microbial fuel cell in anaerobic–anoxic–oxic wastewater treatment process

“…Removal of nitrogen and phosphorus from wastewater is essential to avoid eutrophication. Thus, the anaerobic–anoxic–oxic (A 2 /O) process is widely used for wastewater treatment because of its simultaneous removal of nitrogen and phosphorus . However, lack of or competition for carbon source in the A 2 /O process, the different sludge retention time requirements for phosphorus removal and nitrification, and the difficulty in enhancing denitrification have also been reported .…”

Determination of phosphite in a full-scale municipal wastewater treatment plant

“…20 The A 2 /O system accounted for 35.67 AE 10.50% removal and 66.50 AE 20.00% removal of TSP and phosphite, respectively. During the anaerobic phase, P is released by polyphosphate bacteria, and the uptake of P occurs by poly-P bacteria under aerobic conditions.…”