Characteristic Of The Effect Of Substrate Concentration On Short-cut Denitrifying Phosphorus Removal

To resolve the problems encountered in conventional biological phosphorus removal processes,two novel technologies of short-cut nitrification and denitrifying dephosphatation were investigated,respectively.Based on it,an innovative hybrid system combining the above technologies was proposed in a laboratory anaerobic/anoxic sequencing batch reactor(A/A SBR) and set up for the advanced treatment of domestic wastewater.In the material course of study,author went along a few phases of research through single factor test in the system of denitrifying phosphorus removal.From the experiments I got the main conclusions as follows.(1)There was short-cut denitrifying dephosphatation in the anaerobic/aerobic biological phosphorus removal system originally.With the aid of a stepwise elevation of NO₂^- added in influent and the increase of anoxic time,short-cut denitrifying Poly-P accumulating organisms(DPAO) were gradually accommondated to resist and utilize NO₂^- as electron accepter,and good efficiency of phosphorus removal could be attained.During the experiment period of more than 30 days,the removal rate of TP was about 70%.The experimental results showed that short-cut denitrifying dephosphorus was stable metabolic behavior.Electron accepter utilized by PAO was related to its occurrence.The capacity of PAO utilizing nitrate as electron accepter couldn't be deteriorated by the existing of other electron acceptors.(2) The adding amounts of NO₂^- was one of key factors determining the effect of denitrifying phosphorus removal.Lacking of NO₂^- would cause high PO₄^3- in outfluent,while excessive NO₂^- would reduce P release at next time.When NO₂^- concentration was in the range sludge could tolerate,higher NO₂^- concentration benefited denitrifying phosphorus removal,while the rate reduced with the consumption of NO₂^-.But whether NO₂^- would restrain phosphorus removal efficiency was decided by the adaptability of sludge used to NO₂^-,NO₂^- concentration and pH,the quantity the sludge could resist NO₂^- was improved with sludge adapting to NO₂^-.The higher NO₂^-concentration and the lower pH were beneficial for HNO₂ increasing,and HNO₂ leaded to inhibition seriously.In this research,the relationship between phosphorus removal and NO₂^-consumption was rectilinear.(3)In order to keep steady phosphorous removal efficiency and sludge settle ability,an aerobic stage should be added following anoxic stage,but aerobic sludge was also influenced by NO₂^-.In the process of enrichment and cultivation of short-cut DPAO,in aerobic zone phosphorus was removed by aerobic PAO which was sensitive to NO₂^-;after enrichment and cultivation,the organisms could utilize both NO₂^- and O₂ as electron acceptor.So,the quantity of aerobic PAO resisting to NO₂^- in the anaerobic/anoxic/aerobic system was more than in the anaerobic/aerobic system.(4) The carbon concentration was the other key factor determining the effect of denitrifying phosphorus removal.Lacking of carbon would reduce P release,while excessive it would influence denitrifying phosphorus removal.In this research,when C/P was 25,the efficiency of phosphorus release was the best,beyond or low too much,the effect of the P release was not so good.The higher the C/P,the more the quantity of P release and P release rote,but the rate was decreased when C/P was beyond 25,which showed that wben carbon concentration was sufficient,P release and P release rate might be relevant to microbe.When C/P was right,but NO₂^- was not,we couldn't get good efficiency of phosphorus removal,which showed that the NO₂^- dosage was controlled by C/P to some degree.(5)At the same carbon concentration,efficiency of phosphorus removal was not completely improved with the increasing of P release.The relationship between P release and phosphorus removal was that the change of phosphorus removal was larger than P release,their relationship was quadratic function.(6) There were denitrifying Poly-P accumulating organisms(DPAOs) and glycogen accumulating organisms(GAOs) simultaneously in phosphorus removal system,if the operation condition was controlled properly,GAOs would increase in value,and dominanted in system finally,than the activity of DPAOs was restrained.In this research,the reasons of GAOs increasing included:low pH,too long sludge retention time(SRT),excessive oxygen,lack of nutrition,stir too fast and so on.Besides,there was an important but till in guess reason,which showed that NO₂^- would restrain DPAOs activity but improve GAOs activity.