Denitrifying Phosphorus Removal Mechanism And Influencing Factors In AOA-SBR System

The standard of wastewater discharge was controlled more strictly with the severe eutrophication question occurred.Therefore,the wastewater techniques developed gradually from the period of simplex COD removal to the period of simultaneous COD,nitrogen and phosphorus removal.Today,the nitrogen and phosphorus removal technology aimed for eutrophication control has been one of the hotest study focuses in the wastewater treatment area.Denitrifying phosphorus removal is the new prominent biological wastewater treatment technique.The AOA-SBR system is based on this technique without too much aeration and plus nitrate nitrogen,at the same time,the system can reduce organic carbon and cut the volume of reactor.So these characteristics benefit significantly for the municipal wastewater treatment.This research uses manual wastewater as domestic sewage,not only researchs the best running time of AOA-SBR system,but also concerns with these factors:inlet concentration of organic carbon,C/P,pH,temperature and different electron acceptor which will influence denitrifying phosphate removal process.The main results are as follows:(1) Denitrifying phosphorus bacteria grow and accumulate by adjusting the location of the three phases and run-time.The best operating run-time in anaerobic/aerobic/anoxic is:anaerobic phase 2h,aerobic phase 3h,anoxic phase 3h.in this stable state,COD removal rate is 75%～93%,87.06%on average;phosphate removal rate is 85%on average.(2) After the activated sludge acclimated mature,the AOA-SBR system has built an ideal microbe ecosystem.Here,microbes are diversity,zoogloea presented markedly,the sedimentation performed well and even the protozoan and metazoan could get satisfied environment from this system.It's significant that denitrifying phosphate bacteria acccouts PAOs for 40%in this system,more than traditional nitrogen and phosphorus removal processes. (3) To research on denitrifying phosphorus removal effect in different organic carbon concentration of AOA-SBR system,this trial successfully restrains aerobic phosphorus removal by increasing inlet COD concentration gradually,and comes to the conclusion:Aerobic phosphorus absorption is restrained when COD＞44mg/L in aerobic.Organic carbon restrains aerobic phosphorus absorption more obviously when COD=66mg/L.(4) This trial analyzes the changes of pH in its disciplines and the reasons for changes,researchs the changes of anoxic phosphorus release in different pH values and comes to the conclusion:it makes phosphorus release rate gradually impove and phosphorus concentration also gradually impove in the end of anaerobic phase when pH value rises between 6.5～7.5;it also comes to the conclusion that the best temperture of this system is 20～25℃in this trial.(5) Through the analysis of effect on denitrifying phosphorus removal process under different C/P ratios,come to the conclusion that over low C/P ratio will cause PAOs release at the end of anoxic phase,and over high C/P ratio will increase organic carbon concentration in anoxic and restrain denitrifying phosphorus removal.Both of these will affect outlet water quality.So the best C/P ratio range is 35～45.(6) The trial of different electron acceptor dephosphatation studies have found that over low NO₃^--N concentration will cause anoxic phosphorus release of DPB and PAOs,on the other side there is less impact on denitrifying phosphorus removal after NO₃^--N concentration exceeded a certain extent,so the best NO₃^--N concentration range is 25～30mg/L;NO₂^- is available to be as electron acceptor in denitrifying phosphorus removal process,denitrifying phosphorus removal process will be inhibited when NO₂^--N concentration is over high.So the best NO₂^--N concentration range is about 30～35mg/L.