Improved integrated anaerobic-anoxic-oxic system for landfill leachate treatment using domestic wastewater as carbon source: Performance study and optimization

Landfill leachate has been treated by using an anaerobic-anoxic-oxic (A(2)/O) system at Datansha Wastewater Treatment Plant in Guangzhou, South China for nearly five years. Through the pilot-scale testing and engineering experiments, the impulse loads of the wastewater treatment systems were successfully reduced. The results showed that the highest removal efficiencies of chemical oxygen demand (COD), ammonium-nitrogen (NH4+-N), and total nitrogen (TN) for the combined treatment of domestic wastewater and landfill leachate were achieved under the operating conditions of hydraulic retention time = 11 h, dissolved oxygen = 3 mg/L, mixed liquid return ratio = 200%, and sludge return ratio = 80%. Compared with the data obtained from the previous operating A(2)/O system, the removal efficiencies of COD, NH4+-N, and TN increased by 5.6%, 9.8%, and 5.3%, respectively, under the optimal operating conditions for one year. The average effluent concentrations of BOD5, COD, NH4+-N, TN, and total phosphorus were 12.4, 29.9, 2.5, 18.0, and 0.5 mg/L, respectively, and these values could be kept below standard discharge limits in China.