污水生化处理过程中N_2O的产生特征研究进展

Study on the production characteristics of nitrous oxide in wastewater biochemical treatment process

N2O是大气中重要的温室气体之一,而污水生化处理已被报道是导致N2O产生的潜在人为源之一。大量研究表明,污水生化处理过程中N2O主要产生于微生物的硝化和反硝化代谢过程中。从微生物学和生物化学反应角度,阐述了硝化和反硝化过程中N2O的生成机理,同时给出了几种典型污水处理工艺N2O的产生量和相关影响因素,并对A/A/O工艺中不同处理单元N2O的释放情况进行重点论述。研究发现,对于几种典型的污水处理工艺,由于工艺条件和主要影响因素的不同,N2O的释放量存在较大的差异;对于同一污水处理工艺,不同处理单元N2O的释放量也存在很大差别。污水处理厂中,好氧处理单元是N2O的主要排放单元,而在好氧单元中,DO质量浓度及NO2--N质量浓度是影响N2O释放量的主要因素。在综合分析硝化和反硝化过程N2O产生机理的基础上,进一步总结了污水生化处理过程中DO质量浓度、NO3-和NO2-质量浓度、pH值、C/N比、污泥龄等对N2O释放的影响。

N2O is considered as one of the most important greenhouse gases in the atmosphere.The wastewater biochemical treatment process was reported as one of the potential human sources of N2O production.Many studies and applications of wastewater nitrogen removal processes indicated that,nitrification and denitrification in biological nitrogen removal processes are considered the major sources of N2O in wastewater treatment.The paper reviews the production mechanism of N2O during both nitrification and denitrification processes from the point of view of microbiology and biochemistry.Based on the existing literature reports,N2O production with its influencing factors in several typical wastewater treatment technologies during the wastewater biochemical treatment processes are discussed.In addition,the article put emphasis on N2O emission conditions in different processing units in a particular process,i.e.the A/A/O process.The study revealed that the amount of N2O emission was greatly different for several typical water treatment processes due to distinction in the technological conditions and the main influencing factors.Besides,the N2O emission amount has also been found to be varied in different processing units of same wastewater biochemical treatment process.The studies showed that in the wastewater biochemical treatment processes of the sewage treatment plant, aerobic treatment unit was the main source of N2O emissions where the total emission was significantly more than other units.In the aerobic treatment unit as well,the concentrations of DO and NO-2-N were found to affect the emission of N2O.Based on the mechanism of N2O production during biological nitrogen removal processes,the article analyzed the main factors affecting the N2O production in the wastewater biological treatment process,including DO concentration,NO-3 concentration,NO-2 concentration,pH,C/N and SRT etc.We have provided a theoretical basis for the effective control of N2O emission during wastewater biological nitrogen removal processes.