【作者】 王金鹤；

【导师】 张建；

【作者基本信息】 山东大学 ， 环境工程， 2011， 博士

【摘要】 随着全球变暖加剧,温室气体减排已经引起了国际社会的普遍关注。N2O和CH4是两种重要的温室气体,其温室效应分别是C02的298倍和23倍。污水生物处理过程是N2O和CH4的重要人为释放源。因此,研究城镇污水处理厂污水生物处理过程中N2O和CH4的释放现状和变化规律并探讨减排措施,具有重要的工程实践和社会意义。本论文以采用不同工艺的城镇污水处理厂为研究对象,通过长期系统的现场采样监测和实验室同步分析,研究了污水处理厂污水／污泥处理全工艺流程的温室气体释放状况和变化规律,统计测算了温室气体的释放量范围和释放系数；通过研究不同处理工艺对温室气体释放的影响,筛选确定了温室气体排放较低的推荐处理工艺；通过厂区原位水质监测和实验室分析相结合的方法探讨了在城镇污水处理厂中能显著影响温室气体释放的因素；基于现场实验数据对CH4气体的释放量建立了简易的估算模型。主要研究内容及结论如下：(1)开展了常规A/A/O工艺城镇污水处理厂中N2O气体的释放规律研究工作。通过对以济南市水质净化一厂(简称A/A/O一厂)为代表的A/A/O工艺污水处理厂长期系统的N20释放通量监测分析发现,N20的主要释放源是好氧池,占比约80%。A/A/O一厂的N20人均释放系数是1.69～2.34gperson-1yr-1,流量释放系数是2.32×10-5～3.21×10-5gL-1,该厂的人均释放系数和IPCC报告的数据比较接近,但是流量释放系数要远高于IPCC报告中的数据；好氧池污水中溶解氧浓度和亚硝酸盐浓度是能显著影响N2O气体释放的主要因素,冬季较低的水温区间也能促进N2O气体的产生和释放；进水总氮的脱除量是影响全厂N2O气体释放量占总氮脱除量比例的重要因素,对于采用A/A/O生物脱氮工艺的城镇污水处理厂,N2O释放总量占总氮脱除量的比例范围为0.119-0.195%。(2)开展了常规A/A/O工艺城镇污水处理厂中CH4气体的释放规律研究工作。以A/A/O一厂为代表,对其进行了长期系统的CH4释放通量监测,确定了该厂CH4气体的主要释放源是厌氧池和好氧池,约占该厂CH4总释放量的40%和32%；该厂CH4的人均释放系数是8.17～17.66gperson-1yr-1,流量释放系数是1.12×104～2.42×104gL-1。好氧池、曝气沉砂池中的溶解氧浓度和高效沉淀池中的水温是影响CH4释放通量的重要因素,夏季较高的水温区间有利于污水处理厂CH4气体的产生和释放；进水COD的脱除量是影响全厂CH4气体释放量占COD脱除量比例的重要因素。利用监测得到的A/A/O污水处理厂的CH4释放数据和相关参数,对CH4的气体释放量建立了简单的估算模型,用现场实测数据对模型进行了检验,表明模型参数设置合理,能够用于CH4释放量的简易估算。(3)开展了采用不同处理工艺的城镇污水处理厂中N20和CH4的气体释放通量监测工作。获取了厌氧+氧化沟工艺、预缺氧-A/A/O工艺和倒置A/A/O工艺中N20和CH4的流量释放系数,发现三种工艺中N20和CH4的流量释放系数均明显高于IPCC报告中的参考值；不同处理工艺中释放的N20气体总量占总氮脱除量的比例分别为厌氧+氧化沟工艺：0.183±0.016%,预缺氧-A/A/O工艺：0.156±0.025%和倒置A/A/O工艺：0.117±0.010%；各种工艺中脱除的COD转化成CH4气体的比例分别是厌氧+氧化沟工艺：0.789±0.203%,预缺氧-A/A/O工艺：0.938±0.231%和倒置A/A/O工艺：0.078±0.016%。对三所污水处理厂在实验期间监测到的水质参数变化和N2O、CH4的气体释放通量变化联合进行相关性分析发现在实验期间能够统一显著影响不同处理工艺中N20产生释放的主要因素是污水中的亚硝酸盐浓度,能够统一显著影响不同处理工艺中CH4产生释放的主要因素是污水的氧化还原电位；倒置A/A/O工艺脱除的总氮向N2O的转化率和脱除的COD向CH4的转化率均是四种工艺中最低的,在本论文研究的四种污水处理工艺中,倒置A/A/O工艺是适合城镇污水处理厂采用的温室气体释放最低的推荐处理工艺。更多还原

【Abstract】 With the accelerating of global warming, the reduction of greenhouse gas (GHG) emissions has aroused international attention. Nitrous oxide (N2O) and methane (CH4) are two important greenhouse gases, and their global warming potentials (GWPs) are 298 and 23 times higher than CO2, respectively. It had been reported that biological wastewater treatment process is an important anthropogenic source of N2O and CH4. Therefore, it is very important to study the production, emission and reduction control of N2O and CH4 during biological wastewater treatment processes.This study selected typical municipal wastewater treatment plants (WWTPs) where different biological wastewater treatment processes are used. By long-term systematically field sampling, on-site monitoring in these WWTPs combined with subsequent laboratory analyses, the GHGs production and emission status and variation trends in the entire wastewater/sludge treatment processes in these WWTPs were investigated. The GHGs emission ranges and emission factors (EFs) were calculated based on the experimental data. By comparison between the GHGs emissions of different WWTPs using different wastewater treatment processes, the effect of biological treatment process on GHG emissions were investigated to determine the lowest GHG emission wastewater treatment process. The factors which can significantly influence GHG emissions in WWTPs were identified by both in-situ measurement in WWTPs and laboratory analysis. A simple mathematical model was established to estimate the CH4 emissions and tested by actual experimental data. The main research conclusions are as follows:(1) The N2O emissions from 3 WWTPs using typical A/A/O process were measured systematically in long-term experimental period and the No.1 WWTP in Jinan city was selected for N2O emissions analysis as a typical A/A/O WWTP. Results showed the main N2O emission sources are the oxic tanks, which account for more than 80% of total emissions. The per capita EFs and flow based EFs are 1.69～2.34gperson-1yr-1 and 2.32×10-5～3.21×10-5gL-1. The dissolved oxygen (DO) concentration and nitrite concentration in the oxic tanks are the dominant factors influencing N2O emissions. The lower water temperature range in winter could promote N2O emissions in these WWTPs. Total removed nitrogen in influent wastewater is an important factor influencing the proportion of emitted N2O in the T-N removed from this WWTP, the proportion of N2O in the removed T-N was 0.119～0.195% taking these 3 A/A/O WWTPs into account.(2) The CH4 emissions from 3 WWTPs using typical A/A/O process were measured systematically in long-term experimental period and the No.1 WWTP in Jinan city was selected for CH4 emission analysis as a typical A/A/O WWTP. Results showed the main CH4 emission sources are the anaerobic tanks and oxic tanks, which account for 40% and 32% of total emissions. The per capita EFs and flow based EFs are 8.17～17.66gperson-1 and 1.12×10-4～2.42×10-4gL-1. The DO concentration in oxic tanks and aerated grit tanks and the water temperature in high density settler tanks are the dominant factors influencing CH4 emissions. The higher water temperature range in summer could promote CH4 emissions in these WWTPs. A simple mathematical model was established to estimate the CH4 emissions in WWTPs and the test for model accuracy by actual experimental data showed this model can better reflect the CH4 emissions from these WWTPs.(3) Based on the research of GHG emissions from 3 A/A/O WWTPs, long-term comparative studies were conducted on the GHG emissions from three other WWTPs where anaerobic oxidation ditch, preanoxic A/A/O and reversed A/A/O processes were used respectively. The GHG emission fluxes and sources were determined, the emission variation trends were investigated, and the EFs were figured out. Correlation analyses between N2O and CH4 emissions and water quality parameters were performed to determine the dominant factors influencing GHG emissions from different WWTPs using different biological wastewater treatment processes. Results showed nitrite concentration and oxidation-reduction potential were the factors significantly influencing GHG emissions from these 3 WWTPs. By comparison between the GHG emissions of these WWTPs using 4 different treatment processes, the effect of biological treatment process on GHG emissions were researched, and the lowest GHG emission wastewater treatment process was determined to be the reversed A/A/O process, which has both the lowest N2O/(removed T-N) conversion ratio and CH4/(removed COD) conversion ratio among these 4 studied treatment processes(anaerobic oxidation ditch, conventional A/A/O, preanoxic A/A/O and reversed A/A/O processes).更多还原