Control strategies of nitrogen removal process in a pilot test of the southern WWTP based on the nitrogen balance

By building the mass balance of nitrogen in A2/ O process,the nitrogen model which raised some strategies on how to control sludge return ratio and mixed liquid return ratio to make the effluent nitrogen achieve the national standard A under different influent total nitrogen( TN),was set up. And the presumed parameters were verified by the pilot test of the Wuhan's Longwangzui WWTP. The result showed that when the temperature and the TN were over 15℃ and below 30 mg·L- 1respectively,the mixed liquid return ratio was 0. When the temperature was between 10℃ and 15℃ and TN was over 30 mg·L- 1,higher MLSS and DO elevated N removal. When the temperature was far below 10℃,the mixed liquid return ratio was also at a higher level. Based on the Wuhan's Longwangzui WWTP influent water quality,measures of adjusting the return ratio were well adapted to obtain acceptable nitrogen effluent.