Hydrolysis Acidification/AAO Process for Simultaneous Nitrogen and Phosphorus Removal and Excess Activated Sludge Reduction

Aimed at the disadvantages of low nitrogen and phosphorus removal efficiency and high sludge production in conventional activated sludge processes,the integrated treatment process of wastewater and excess sludge by hydrolysis acidification/anoxic-anaerobic-aerobic(AAO) process was put forward.The efficiencies of COD,nitrogen and phosphorus removal and sludge reduction by this process and the main influencing factors were investigated.The results show that when the influent COD,NH+4-N and PO3-4-P are 286 to 425 mg/L,36 to 58 mg/L and 4 to 12 mg/L,as well as the hydraulic retention time is 11.5 h and no external carbon source or alkalinity is added,the removal rates of COD,NH+4-N,TN and PO3-4-P are 95%,98%,84% and 87% respectively.The DO concentration,SRT in aerobic stage and reflux ratio of excess sludge significantly affect the operation results.The simultaneous hydrolysis of wastewater and excess activated sludge can improve the biodegradability of raw wastewater,the utilization rate of carbon source,and reduction of excess activated sludge.The reduction rate reaches 56.5% in the experiment.