Study On Denitrification In A/O Process Enhanced By Bio-electrode Methode

Among several kinds of nitrogen removal methods,biology process is widely used due to the advantages of low cost and the muti-pollutant removal effect,and A/O process is the most popular technology in the project.In A/O process,with the rate of denitriflcation increasing,the cubage of Tank A will be dimished sharply,which can cut down the cost of the whole project.A study of bio-electrode method which is used to enhancing the denitrification of A/O process is carried out.On the popurse of researching the characters of combination of A/O process and bio-electrode method and providing some according for the application of the technology,influencing factors of denitriflcation,such as applied voltage,carbon source,C/N ratio,N source and load of TN were investigated under simulated condition to the Tond A of A/O process,which was enhanced by bio-electrode method.A proper applied voltage significantly enhanced the rate of denitrification. The relation between applied voltage and the rate of denitrification was positive correlation.And the optimum voltage was 3.0V,at which the decomposing rate of TN and NO₃^--N increased by 74%and 20%respectively.Meanwhile,the applied voltage depressed the accumulation of NO₂^--N.The accumulation of NO₂^--N at 2.1V was only 14.5mg/L,which was 61%less than the concentration without applied voltage.The kind of carbon source needed in the degradation of nitrate and nitrite was different.The degraded rate of TN and NO₃^--N had obvious distinction with different kind of carbon source;methanol was a better kind of carbon source to the degradation of TN while dextrose was more suitable to the degradation of NO₃^--N.Carbon source mixed with methanol and dextrose had the best performance in the three.The degraded rate of TN had an enhancement of 50.3%, 26.3%and 33.0%in the reactor with applied voltage while the carbon source was dextrose,methanol and mixed carbon source.The range of enhancement was positive correlation with the concentration of NO₂^--N accumulated.The rate of denitrifition could be enhanced by elevating the C/N ratio,while the accumulation of NO₂^--N was also higher.In the reactor with applied voltage,the degraded rate of TN had a steady enhancement of 60%at different C/N ratio.Orthogonal experiment result showed that except for the change of applied voltage,the microorganism was without domestication.The influencing factors to the degradation of TN were decreasing as TN loading,C/N ratio and applied voltage.Inital concentration of NO₂^--N had no obvious influence with a correlation coefficient of -0.07(nearly 0).The degraded rate of NO₃^--N was correlated with TN load and inital concentration of NO₂^--N.The biggest influencing factors of the percentage of NO₂^--N to TN were TN load and applied voltage.A kinetics study,in which the connection of applied voltage and parameters of Monod equation were investigated,was finished.A mathematical model of the degradation of TN under different applied voltages was obtained by finding parameters of Monod by linear translation method.Under proper applied voltage, the parameter of Monod V_max had linear connection,while the other parameter K_N was determined by the existence of the applied voltage or not.K_N was 32mg/L in the reactor without applied voltage and 43mg/L with applied voltage.The mathematical model obtained simulated the concentration of the TN in the course of degradation well.The error between simulated and experimental values was less than 3mg/L.A higher simulating precision would be got through finding the parameters of Monod equation by MATLAB.The error between simulated and experimental values could be less than 1mg/L except for some special data.And the confidence interval of the modle obtained by MATLAB was narrow,which meaned that the modle had an excellent performance.