A Comparative Study On Mechanism Of Nitrogen And Phosphorus Removal And Metabolic Activity Of Microorganism Between Reversed A~2/O Process And Conventional A~2/O Process Under Different Carbon Resource

Eutrophication threats the normal function of urban water environment of China. Althoughthe mechanism of the eutrophication occurrence is complex, high content of nitrogen,phosphorus and other nutritive substances in the water are the fundamental reason, so thedischarge requirement levels of Nitrogen and Phosphorus in the effluent form wastewatertreatment plants become more and more stringent to protect lake and other natural water fromeutrophication. Therefore, municipal wastewater biological nutrient and phosphorus removaltechnology has increasingly become a hot issue in the field of sewage treatment.Reversed A²/O process was proved to be an efficient nitrogen and phosphorus removalprocess. Because of the pre-anoxic, carbon source for nitrogen removal was satisfiedpreferentially, at the same time, the adverse effects toward anaerobic environment induced bythe nitrate in the returning sludge had been avoided. Many inherent contradictions andbottlenecks in biological nutrient and phosphorus removal system had been completely solved.But the biological mechanism of the reversed A²/O process was not systematic developed now,especially the influence of different carbon rescources on the nitrogen and phosphorusremoval in municipal wastewater treatment plants. Therefore, this test was designed toresearch the nitrogen and phosphorus removal capacity and the metabolic activity of activatedsludge in order to analyze the differences on nitrogen and phosphorus removal betweenreversed A²/O process and conventional A²/O process under different carbon resource.The results show that:（1） Whether VFA/COD_Crwas100%or VFA/COD_Crwas60%, reversed A²/O process hadbetter removal efficiency on organic pollutants, nitrogen and phosphate than conventionalA²/O process. Moreover, the superiority of phosphorus removal was most obvious in thecondition that VFA/COD2Crwas60%. In addition, Reversed A/O process had highernitrification rate and denitrification rate. In these experiments, change of the the rate of theVFA in the effluent could not obviously impacte the organic pollutants and nitrogen rate oftwo processes, but it could seriously influence the denitrification rate and metabolic activity inconventional A²/O process. However, change of the the rate of the VFA in the effluent couldobviously impacte phosphate removal of both processes, but reversed A²/O process hadstronger resistance and adaptability ability than conventional A²/O process.（2） Whether VFA/COD_Crwas100%or VFA/COD_Crwas60%, lower phosphorus releaseand PHA generation was achieved in reversed A²/O system under anaerobic conditions, buthigher phosphorus uptake rate of PHA comsumption was carried out under aerobic phase in reversed A²/O process compared with conventional A²/O system. The results indicated thatthe better phosphate removal effect of reversed A²/O process was reasonable the higherenergy utilization efficiency under aerobic conditions.（3） Whether VFA/COD_Crwas100%or VFA/COD_Crwas60%, the TTC-DHA activity,INT-ETS activity and SOUR of reversed A²/O process were higher than that of conventionalA²/O process. The reversing of anaerobic and anoxic enhanced the metabolic activity andbiochemical reaction efficiency of activated sludge in aerobic phase, resulting in a higheraerobic biological degradation rate and oxygen utilization rate.（4） The activity of microbial populations in reversed A²/O process had a stronger carbonmetabolism and metabolic efficiency than conventional A²/O process. In addition, the carbonresource utilized by microbial populations in two processes was slightly different whenVFA/COD_Crwas100%. However, species of carbon species used in reversed A²/O processwere significantly more than that in conventional A²/O process when the proportion of VFAdecreased.