Study On Simultaneous Nitrification And Denitrification Nitrogen Removal And Chemical Phosphorus Removal In Oxidation Ditch Process

The conventional biological sewage treatment processes,in order to achieve nitrogen and phosphorus removal usually set up to anaerobic,anoxia and aerobic pond,which will increase the sewage treatment plant infrastructure costs.And running,aerobic pond aeration system,the cost of electricity consumed throughout the sewage plant is the main part of the operating costs.In order to reduce infrastructure costs and save energy,many processes spring up.Such as simultaneous nitrification and denitrification,anammox, denitrifieation and other new types of aerobic biological nitrogen removal process in recent years.This paper mainly studies the low dissolved oxygen conditions,by controlling the impact factors of simultaneous nitrification and denitrification to determine the best conditions.And then establish the oxidation ditch simultaneous nitrification and denitrification dynamics model.In the latter part of the study,I did reseach on chemical phosphorus removal of effluent of oxidation ditch.In the course of the study I focused on some impact factors.Such as HRT,C/N,activated sludge concentration and F/M.During the study temperature of oxidation ditch is between 20℃and 25℃, dissolved oxygen is between 0.6 mg/L and 1.0mg/L.Due to the impact of nitrification and denitrification the pH can automatically keep between 7.5 and 8.3.Under these conditions,the study showed that when we treated with the campus sewage,the best operating conditions of Oxidation Ditch simultaneous nitrification and denitrification was that the HRT was 6 hours,the sludge concentration was 3.5 g/L,the C/N was between 6 and 9,the sludge load was 0.3kgSCOD/kgMLSS^*d and 0.03 kgNH₄⁺-N/kgMLSS^*d.In the best operating conditions,the average removal efficiency of COD was 91.29%,the average removal efficiency of ammonia nitrogen was 80.68%,the average removal efficiency of TN was 68.13%.This shows that,COD and ammonia nitrogen were relatively easier to remove,while TN removal of the entire process was difficult.Study showed that HRT,C/N and concentration of sludge were the most important factor ofoxidation ditch simultaneous nitrification and denitrification.Reasonable HRT assured biological floc formation of aerobic,anoxic structure when the dissolved oxygen conditions was low in the oxidation ditch.Suitable C/N not only meet the heterotrophic aerobic micro-organisms,but also as a carbon source to provide denitrifying bacteria.Enough sludge activated sludge concentration is a necessary condition.South China's domestic sewage C/N remained in the 6 to 9,the process is an ideal operating conditions.Low dissolved oxygen conditions,the phosphorus removal rate was only 20%to 40%and phosphorus concentration of effluent was 1.0mg/L to 4.0mg/L,phosphorus removal mainly by the basic microbial growth and metabolism.So we adopted isochronous deposition phosphorus removal process,used Al-Fe polymerization as the main phosphorus reagents,addingβcoefficient of 1.5,phosphorus concentration of effluent could meet the emissions standards.Paper analysed the removal of pollutants(including COD,NH₄⁺-N,TN and TP) comprehensively.And analysed various control parameters(HRT,C/N,activated sludge concentration and F/M) for the removal of nutrients.Through the establishment of the dynamics model of COD remol,we had conclusion the maximum specific velocity of substrate removal Vmax=5.32d-1,and the organic contaminant degradation coefficient Ks=21.56mgCOD/d;thereaction order in of NH₄⁺-N degradation n=0.2,and the reaction velocity constant k=4.27.