Energy Saving, High Biological Phosphorus Removal and Improvement of Sludge Settleability on Full-Scale Anaerobic–Aerobic Activated Sludge Process

An anaerobic-aerobic process was modified from a conventional process used in municipal sewage works to enable phosphorus removal and improving sludge settleability. Research was conducted in three sewage works in comparison with the conventional process. The phosphorus removal efficiency by the anaerobic-aerobic process was higher. The T-P removal ratio ranged 80 - 90% and T-P concentration of the effluent was almost below 1 mg/l, when the average T-P/BOD ratio was 0.04. The removal efficiency of other water quality and excess sludge generation ratio were almost equal in both processes. The anaerobic-aerobic process is not only effective for improving the sludge settleability but also enables wastewater treatment with less quantity of air (approx. 20% reduction). Even including the power consumed for mixing, the anaerobic-aerobic process used up less power (approx. 12%).