Sustainable Mining and Metallurgy

A wastewater treatment plant in northern China adopted the AAO process in the past to ensure that the outlet water was in compliance with the first-level A standard regulated in Discharge Standard of Pollutants for Municipal Wastewater Treatment Plant. Now, to reduce pollution to water body, indicators of COD_Cr, NH₃-N and TP in the outlet water should be improved to comply with the Grade V water standard stipulated in Environmental Quality Standards for Surface Water. Due to the improvement of effluent standards, the sewage plant needs to be upgraded. Comparison of influent and effluent indexes showed that NH₃-N and TP should be focused on. Without adding new structures, MBBR packing is applied to partial gallery of the original oxic tank and AAO tanks were rezoned for 5-stage AO process. In the meantime, the blower room, aeration system, sludge dewatering system and other systems were also upgraded. After upgrade, After the transformation, the indexes of the effluent reached the standard stably, indicating that the process had strong stability and impact resistance.