Production Key Factors And Emission Control Of Nitrous Oxide In Sequencing Batch Reactor Wastewater Treatment Process

Wastewater biological nitrogen removal process is an important anthropogenic sources of nitrous oxide in the atmosphere, its value has a tendency to increase year by year in recent years, then effectively reduct and control the emission of nitrous oxide has become one of the important research topic in the field of air and water pollution. Therefore, this study focused on the production and release of nitrous oxide with Sequencing Batch Reactor(SBR) as a model test device in the wastewater treatment process. The test resolved and screened the key role of nitrous oxide to produce in the sewage biological denitrification process with the orthogonal experimental method system, and then quantitative clarify the generation of nitrous oxide under the action of key factors. Whichprepareded for researching the generation of nitrous oxide in the actual wastewater treatment, and put forward the corresponding control strategy of nitrous oxide. Thus, which canprovided a theoretical reference and scientific basis for the mechanism and emission control of nitrous oxide in wastewater biological nitrogen process, and provide technical references for practical engineering application in nitrous oxide controlof sewage biological denitrification.The test design the nine factors and four levels orthogonal table to research the key factors that temperature(A), dissolved oxygen(B), carbon and nitrogen ratio(C), p H(D), ammonia nitrogen concentration(E), the running mode(F) and the kind of carbon source(G) according to the filter based on literature. Then come out seven main factors affecting nitrous oxide generated in the orthogonal experiment and the extremum of the seven main factors is RB>RD>RG>RC>RE>RA>RF. Therefore, the dissolved oxygen, carbon and nitrogen ratio, kinds of carbon source and inflow p H value is the key factors what affect the production of nitrous oxide in the sewage biological denitrification process and which is based for the next research. Then using the response surface method to screen out the four key factors for further analysis, then come out that dissolved oxygen is uppermost factor, carbon and nitrogen ratio and carbon source are next, the inflow p H value at last.Which was in accorded with the experimental results.Then start the model of SBR reactor and the reactor inlet is the artificial mixed simulation sewage reactor by 20 d start-up success, and then researched the success of the start and stable operation stage, the system of COD, ammonia nitrogen and total nitrogen removal rate can stay above 90%, 85% and 80% respectively. The production of nitrous oxide gradually reduced and remained at 2mg/L in stable operation stage.Subsequently, we still analyzed the pollutants removal efficiency and the generation of nitrous oxide under the different of dissolved oxygen, carbon and nitrogen ratio, the kind of carbon source and the inflow p H value in Sequencing Batch Reactor. During the test, the dissolved oxygen level in 0.5, 1.0, 1.5, 2.0, 2.5, 3.0 mg/L, carbon and nitrogen ratio of inflow in 2, 4, 6, 8, 10, 12, the p H value of inflow in 6.5, 7.0, 7.5, 8.0, 8.5, 9.0. Under the premise that ensure the pollutant removal efficiency, the DO = 1.5 mg/L, C/N = 6.0 and p H = 7.5~8.0 can maintain the production of nitrous oxide to minimum quantity, which can be used as a control the recommended operating conditions to control the emission of production. Meanwhile, test selected soluble starch, glucose, sodium acetate, methanol, propionic acid and butyric acid as carbon source to found that the production of nitrous oxide is least at the methanol as carbon source. There are also found that mixing carbon source system under the condition of nitrous oxide to produce value lower than single carbon source, and the actual sewage are mixed carbon sources. This study also found that nitrous oxide is mainly produced in aeration stage, and the aeration phase discharge of nitrous oxide has strong positive correlation with the nitrate concentration.The paper also researched the pollutants removal efficiency and the regularity of nitrous oxide produced in the Sequencing Batch Reactor to removal the actual wastewater. When the aeration stage dissolved oxygen is 1.5 mg/L and the p H value is 7.5~8.0, and the COD and ammonia nitrogen concentration for an average of 277 mg/L, 62 mg/L. The COD, ammonia nitrogen concentration of effluent can be stable at 25.8 mg/L, 9.2 mg/L, which can achieve to the urban sewage treatment plant pollutant discharge standard(GB18918-2002) in the level of A and B discharge standards respectively. The concentration of nitrous oxide remained at 1.7 mg/L and remained comfortably low comparison with literature and the preliminary test results. Therefore, we choose that aeration stage dissolved oxygen is 1.5 mg/L and the p H value of inflow is 7.5~8.0 take the pollutants removal efficiency and the production of nitrous oxide into consideration to control.