High-Nitrate Wastewater Denitrification

The rapidly development of coal glycol industry has brought serious environmentalproblems. This project derives from the DongHua coal glycol corporation, with an annualoutput of100000tons. The coal glycol industry wastewater contains large amount ofnitrate and nitrite, which is belong to national non-emission high concentrationwastewater. Aimed at the characteristic of this wastewater, with the comprehensivecomparison of the denitrification process both home and abroad, we have our primefocus on domestication of denitrification sludge, and choose two-stage denitrifyingbiological denitrification to deal with such high concentration of industrial wastewater.Explore the domestication and cultivation of denitrifying bacteria, the analysis of carbonresource, the orthogonal design of experiment and controlling model. Based on theexperiments we did before, we make our further study on high nitrate denitrificationdegradation kinetics. The methods we used to conduct our study were artificialsimulating and orthogonal experiment.Denitrification sludge can be divided into three stages for domestication. Theremoval rate of both nitrate and nitrite can be as high as50%after65days’ domestication,showing a good sign that the sludge are successfully domesticated. Adding methanol ascarbon source for denitrification, the ration of C/N can be controlled by4. In primarystage of sludge acclimated, COD removal rate is up to80%, the nitrate and nitritenitrogen removal rate almost zero. In the subsequent stages, COD removal rate ismaintained at about60%. Under certain condition （MLSS:8000mg/L,T:28℃,DO<0.2mg/L）, the two-step of denitrification biological nitrogen is influenced mainlyby the value of pH, HRT and stirring rate n in its reaction system. We finally determinesthe optimum process parameters HRT=8h, n=1800r/min and pH=7.5after comparingdifferent experiments. We found out that we could have the best result by using two-step of denitrification biological nitrogen, after which the removal rate of nitrate could be68%with nitrite reaching72%. We also obtained the best controlling model and wereable to validate nitrate nitrogen and high concentration of NO₃^--N and NO₂^--Ndegradation accorded with Monod level degradation dynamics equation by carrying outmore experiments based on it. The three groups of the concentration of nitratedegradation kinetics fitting equation, shows that the concentration of1（861mg/L） andconcentrations of3（3445mg/L） degradation rate have no obvious difference, comparewith them, the concentration of2（1722mg/L） degradation rate was the biggest. Threeconcentrations of nitrite degradation kinetics fitting equation, shows that theconcentration of1（255mg/L） and concentrations of3（1020mg/L） degradation rate haveno obvious difference. Compare with them, concentration of2（510mg/L） degradationrate was the biggest.