The implementation of single-sludge step-feed anoxic–aerobic process in a domestic wastewater treatment plant

The single-sludge step-feed anoxic–aerobic process (SSFAOP) was implemented in the Xuzhou wastewater treatment plant (WWTP) in China to enhance ammonia and nitrogen removal performance. Influent flow splitting and step feeding in the aerobic zone were used to provide high concentrations of mixed liquor suspended solids (MLSS), long solids retention time (SRT), and short nitrification time. After implementation, removal efficiencies of ammonia nitrogen >90% and total Kjeldahl nitrogen (TKN) >80% were achieved. The amount of waste activated sludge (WAS) was significantly reduced, and sludge bulkings were eliminated. The application of SSFAOP also reduced capital and operational costs.