[Autotrophic nitrogen removal and enhanced biological phosphorus removal from municipal wastewater in a three-sludge system].

Using a three-sludge system consisted of anaerobic/oxic (A/O) process, partial nitritation and anaerobic ammonium oxidation (ANAMMOX) reactors, cost-effective removal of nitrogen and phosphate from municipal wastewater was achieved. The experimental results showed that effluent total phosphorus (TP) of the A/O system was less than 0.5 mg/L under hydraulic retention time (HRT) of 3.6 h. Partial nitritation with nitrite accumulation efficiency of 75% -96% was realized in the partial nitritation system under room temperature, DO < 0.2 mg/L and HRT of 4.6 h. Under temperature of 27-30 degrees C and HRT of 1.4 h, effluent total nitrogen (TN) and TN removal rate of ANAMMOX reactor were less than 8 mg/L with the minimum value of 1.6 mg/L and 0.57 kg/(m3 x d), respectively. In the three-sludge system, phosphate accumulating organisms, ammonia-oxidizing bacteria and Anammox bacteria existed under suitably environmental condition to optimize the microbial community structure and improve treatment efficiency of various units. Autotrophic nitrogen removal can reduce 62.5% of the oxygen supply, save 100% of denitrification carbon sources theoretically, lower the sludge production, and greatly decrease carbon dioxide emission. As compared to traditional biological nutrient removal process, the three-sludge system has great advantages and potential in energy saving and carbon dioxide emission reduction to realize sustainable development of water resources.