Keywords: aerobic, anaerobic, BOD, biological oxygen demand, food-, microorganism ratio, hydraulic loading, nitrogen removal, wastewater treatment, activated sludge, sludge volume index, SVI, domestic wastewater
Efficient nitrogen removal for wastewater in compartmentalised activated sludge process
Studies were conducted on two aerobic-anaerobic configurations of the activated sludge process for nitrogen removal from domestic wastewater. An initial anaerobic stage followed by aerobic, anaerobic and aerobic stages provided best total Kjeldahl nitrogen removal. This profile was selected for conducting further experiments on the effect on nitrogen removal of the hydraulic loading and the food to micro-organism (F:M) ratio. The results show that higher nitrogen removal is observed at high hydraulic loading and low F:M ratio. The optimum removal of 68% was observed at a hydraulic loading of 0.665 kg/m.d and an F:M ratio of 0.18 kg BOD kg MLSS-d. Total and soluble BOD removal exceeded 95% and did not vary with the EM ratio. The sludge volume index remained below 120, showing good settling properties.