Quantitative Research of Nitrogen Removal for Modified A~2O Technology

The nitrate nitrogen in the sludge can be removed by first anoxic district of modified A2O technology.The bio-denitrification in first anoxic district was an important way for total nitrogen(TN) removal in system.Based on modified A2O technology in Kunshan astewater Treatment Plant(WWTP),the ways and quantity of TN removal were analyzed by quantitative methods.TN removal was the most happened in the first anoxic district and traditional anoxic district,where contribution rate of NO-3 were 51% and 42%,respectively.The average quantity of NO-3 in the first anoxic district was 132kg/d,correspondingly the rate of removal was up to 81.5%.However,the rate of mixed liquid recycles was excess for bio-denitrification in the traditional anoxic district.The rate of mixed liquid recycles was suggested reducing to 150%.As an important way for TN removal in preposing denitrification,the TN removal relationship between traditional anoxic and first anoxic should be balanced in order to meet TN discharge standard.