Experimental Research On Factors And Enhance Operation Effect Of A/O Biological Nitrogen Removal Process

The following experiments were carried out with the simulative wastewater as the research object and the removal behaviors of COD, NH4+-N and TN of A/O biological nitrogen removal as the main index.The concentration of COD, NH4+-N and TN was respectively574.9mg/L-639.6mg/L,93.73mg/L-117.6mg/L, and pH was7-8.(1) The main controlling factors such as the reaction time of anoxic and aerobic, reflux ratio and SRT of A/O process were clearly studied and the optimal operating condition of A/O process was determined.(2) On the base of the optimal operating condition, the dynamics pilot of ammonia degradation and denitrification were carried out, then calculated the kinetic parameters.(3) In order to enhance the operational effect of A/O biological nitrogen removal process, suspended fillers were added.Pre and Post operation effect of the system were showed by analysis and comparison.The research of A/O process treating sewage at different time was took under the condition of the sludge ratio was100%, reflux ratio of nitrification was200%, SRT was15d, MLSS was for3000-3500mg/L and DO was about2.0-3.5mg/L.The research results showed that the change of the reaction time of anoxic and aerobichad little effect of the removal rate of COD, but had greatly affected the removal rate of TN. When increased the reaction time of anoxic to6h, the removal rate of TN could be above80%.And the effluent quality reached to: COD=21.99mg/L, and NH4+-N=3.9mg/L.The experiment was carried out at different sludge reflux ratio and reflux ratio of nitrification, and the research conclusion was that reflux had little effect on effluent COD and NH4+-N concentration of the A/O process, while the removal rate of TN was influenced greatly at different reflux ratio.The removal rate of TN could be more than80%when the sludge reflux ratio and internal recycle ratio respectively was100%,200%, however, higher reflux ratio went against the removal of TN.In the experiment, the SRT of the system was adjusted at5d,10d,15d,20d, and it was found that SRT had little effect in the removal rate of COD, but the removal rate of NH4+-N and TN could be improved with the prolongment of SRT. And thereasonable SRT of the process was15d.The transformation law of nitrogenin the A/O biological nitrogen removal treatment showed that ammonia concentrationdecreased, also the nitrite nitrogen went peak then gradually decreased, but the nitrate nitrogen entirely escalated, however, the TN concentration decreased.The forms of nitrogen in effluent was mainly nitrate, accounting for about81.81%, but ammonia nitrogen and nitrite nitrogen accounted a small proportion, respectively13.86%and0.33%.The reaction order was n=0.786of ammonia degradation, with the reaction rate constant k=0.644.The denitrification process of static test was carried out at the ratio of C/N was6, and the rate curve of denitrification process could be divided into3stages, in this case, the denitrification rate were7.1Omg/(g·h),14.64mg/(g·h),2.12mg/(g·h).Controlling the A/O process under the optimal operation condition, and by adding fillers, the removal rate of COD, NH4+-N and TN was higher than the conventional A/O process, which were96%,95%,87%.The concentration of COD, NH4+-N and TN of the effluent were18.04mg/L,1.96mg/L and12.78mg/L.