【作者】 吴小刚；

【导师】 张晖；

【作者基本信息】 武汉大学 ， 环境工程， 2012， 博士

【摘要】 垃圾填埋是垃圾最终处置的最佳途径之一,但在此过程中所产生的渗滤液会对环境造成危害。渗滤液的成分十分复杂,特别是其中含多种难降解有机物,高级氧化技术是一种有效的处理方法。本论文以电Fenton技术为基础,展开了其操作条件的优化及相关强化技术的研究。对电Fenton法处理渗滤液过程中氧化作用与絮凝作用对COD去除的贡献进行了深入分析。在电Fenton中引入紫外光,对光电Fenton处理过程中多因子进行了析因分析。同时探讨电Fenton处理前后渗滤液的可生化性。另外利用SBR法适应渗滤液水质变化、经济高效去除氨氮的特性,优化了其处理工艺,探讨了其与电Fenton相关技术组合工艺处理渗滤液。(1)研究了电Fenton法处理渗滤液过程中氧化作用与絮凝作用对COD去除的数量关系,考察了反应过程中H202与Fe2+摩尔比,Fenton试剂量、初始pH值、电流密度、电极板间距、H202投加方式对COD去除的影响。结果表明,高H2O2/Fe2+条件电Fenton下,在氧化作用与絮凝作用COD去除率中,氧化作用COD去除率占主导。总COD去除率与氧化作用COD去除率呈相同趋势。絮凝COD去除率随着初始pH值和亚铁离子的增大而增加,当二者固定后,其它因素影响较小。氧化作用COD去除率随初始pH值减小而增加,存在优化的H202和Fe2+的投加比、电流、板间距时,氧化作用COD去除率更高。多次投加或连续投加比一次投加COD去除率更高。电Fenton法处理渗滤液120min后分子量小于4kDa有机物占绝对优势。GC-MS检测结果显示,原渗滤液检测到87种有机污染物,其中68种经电Fenton法处理后在出水中未检测到。(2)光电Fenton处理渗滤液过程中紫外光有利于亚铁再生,促进羟基自由基的产生。本试验对多个影响因子进行了析因分析。结果表明,H202、初始Fe2+浓度、初始pH值、电流密度与pH值交互作用是显著因子。主效应分析和模型等高线分析表明,在光电Fenton中COD去除率随着H202、初始Fe2+浓度增加而增加,随初始pH值增加而减少,电流密度对响应值COD去除率影响不大。析因分析后根据显著因子拟合模型是显著的。(3)研究了电Fenton处理前后影响渗滤液可生化性的相关水质变化。电Fenton处理后小于4k Da组分的TOC占总TOC比例提高到92.5%,渗滤液中大于4kDa难降解大分子有机物几乎都降解为小于4kDa有机组分。红外光谱分析表明大分子芳环类有机物减少,而小分子脂肪烃类有机物增加。NH4+-N去除率相对于COD去除率较低,其它形态氮浓度变化不明显；重金属离子As、 Pb、Hg, Cr去除效果好。电Fenton处理后其中可生物降解性有机物绝对数量BOD5减小,而可生化性指标BOD5/COD及BOD5/TOC提高。原渗滤液BOD5/COD及BOD5/TOC分别为0.09、0.27,电Fenton处理后,出水分别为0.21、0.29。(4)本试验对SBR处理渗滤液过程中运行方式、容积负荷的变化进行了比较与分析,并探讨SBR内置膜强化氨氮的去除。SBR驯化后,采取A/O方式时TN、NH4+和COD的处理效果没有A/O/A/O方式好。采取A/O/A/O方式稳定运行,容积负荷为0.5-0.55kgCOD/m3.d左右时,COD去除率在45.9%-49.1%范围,NH4+去除率在72.2%-77.3%范围。容积负荷为0.54kgCOD/m3.d的运行周期内发生短程硝化,亚硝酸盐累积率91.9%。增加负荷至0.7kgCOD/m3-d左右时,TN、 NH4+和COD去除率下降。采用SBR内置膜技术处理垃圾渗滤液,稳定运行后出水NH4+和COD的平均去除率分别为91.2%和87.3%,内置膜防止硝化菌的流失,有利于渗滤液中氨氮去除。(5)应用组合工艺SBR与电Fenton、SBR与电化学氧化处理渗滤液。原渗滤液平均COD6325mg/L、平均NH4+1269.1mg/L,首先经过SBR处理,水质能降到平均COD797mg/L、平均NH4+101.5mg/L。而SBR出水进行电Fenton处理,在优化条件下运行3h, COD、NH4+分别达到187.3mg/L、56.1mg/L。SBR出水进行电化学氧化处理,三维电极运行3h比二维电极氨氮去除率高34.3%。三维电极电化学氧化法在电流密度40mA/cm2下运行3h, COD、NH4+去除率分别为93.5%、66.9%,比30mA/cm2运行效果好。电流密度40mA/cm2反应2h后氨氮能达到污染控制标准规定的25mg/L以下。比较两组合工艺,在试验优化条件下,SBR法+电Fenton对COD去除效果好,而SBR法+电化学氧化对氨氮去除效果好。更多还原

【Abstract】 Landfill is one of the best ways to waste final disposal, and leachate generated in this process would cause harm to the environment. Leachate composition is very complex, which contains a variety of refractory organic matter. Advanced oxidation processes were effective to degrade refractory organics. In this paper, based on the electro-Fenton treatment, Research on optimization of operating conditions and enhanced technology were expanded. In-depth study of oxidation and coagulation removal of COD from landfill leachate by E-Fenton. Factorial design analysis to screen the significant factors which influenced photoelectro-Fenton process. And the biodegradability of leachate during E-Fenton process was discussed. As SBR adapt to changes in leachate quality and effective removal of ammonia, studies of optimization of SBR process were conducted. And then the combination of SBR with E-Fenton related technologies were investigated.(1) COD removal by oxidation as well as by coagulation during Fered-Fenton treatment of landfill leachate was quantitatively determined in this study. The effects of operating conditions such as H2O2to Fe2+mole ratio, Fenton’s reagent dosage, initial pH, current density, inter-electrode gap and hydrogen peroxide feeding mode on COD removal was investigated. The results showed that COD removal by oxidation is dominant due to the high H2O2/Fe2+mole ratio employed and the overall COD removal showed the same behavior as oxidation removal. The coagulation removal of COD increased with initial pH and ferrous iron dosage, but it was independent of current density and the inter-electrode gap at a fixed initial pH value and ferrous iron dose. Increasing Fenton’s reagent dosage or decreasing the initial pH is likely to promote COD removal by oxidation. There existed an optimal H2O2/Fe2+mole ratio, current density or inter-electrode gap to reach the highest COD removal efficiency by oxidation. The stepwise or continuous addition of hydrogen peroxide was more effective to oxidize organics than a single dose of hydrogen peroxide. Nearly all the organic compounds (>4kDa) were degraded into smaller ones after Fered-Fenton treatment. GC-MS analysis was used to determine the organic compounds before and after the treatment.(2) PE-Fenton process induces the production of hydroxyl radicals from the regeneration of ferrous ions and the reaction of hydrogen peroxide with UV light. As there are so many operating parameters in the PE-Fenton process, it is necessary to develop a mathematical model in order to produce the most economical process. In the present study a factorial design was carried out to evaluate leachate treatment by the photoelectro-Fenton process. The influence of the variables:initial H2O2concentration, initial Fe2+concentration, current and pH in the PE-Fenton process was investigated by measuring COD removal efficiencies after60min of reaction time. The relationship between the COD removal and the most significant independent variables was established by means of an experimental design. The H2O2concentration and initial Fe2+concentration, the pH and the interaction effect between current density and initial pH were all significant factors. The factorial design models were derived based on the COD removal efficiency results and the models fit the data well.(3) A basic study to investigate the variety of water quality associated with biodegradability during E-Fenton process. The rate of MWCO less than4k Da would be obviously shifted from70.2%to92.5%after E-Fenton. FTIR observations reveal the decrease of aromatic organic compounds and the increase of the aliphatic ones. The removal of ammonium was less than the removal of COD at the experimental conditions, heavy metal ions As, Pb, Hg and Cr was nearly all removed. The biodegradability was improved (BOD5/COD from0.09to0.21, BOD5/TOC from0.27to0.29), although the value of BOD5is reduced.(4) Leachate treatment using the sequencing batch reactor with different operation mode and volume load, and membrane bioreactor are trial operated. The research results show that the removal of COD and TN is better in the condition of anoxic/aerobic/anoxic/aerobic (A/O/A/O) than that of anoxic/aerobic (A/O) process. During the treatment with SBR of A/O/A/O, The volume loading around0.5-0.55kgCOD/m3·d has got better results. The COD removal rates of45.9%～49.1%and NH4+-N removal rates of72.2%～77.3%were achieved. The particial nitrification is achieved in the reactor with more than92.1%of the nitrite accumulation ratio with volume loading around0.54kgCOD/m3·d. SBR-membrane bioreactor treatment of landfill leachate was investigated, average removal rates of COD and NH+-N were87.3%and91.2%.(5)The integration of SBR and E-Fenton or SBR and electrochemical oxidation technologies to deal with landfill leachates have been investigated. The raw leachate, with average values of COD6325mg/L and NH4+1269.1mg/L, was first treated by SBR reducing the former parameters to797mg/L of average COD and101.5mg/L of average NH4+. Next, the effluent was treated using electrochemical oxidation technologies or E-Fenton method. After the treatment of E-Fenton, COD and NH4+-N were reduced to187.3mg/L and56.1mg/L respectively. The increase of ammonium removal was34.3%by three-dimensional electrodes compared to two-dimensional electrodes. COD and NH4+removal rate is higher in40mA/cm2than that of30mA/cm2, and93.5%of ammonium nitrogen removal efficiency and66.9%of COD removal efficiency could be achieved at40mA/cm2in3hour. Ammonium was degraded to lower25mg/L by three-dimensional electrode method, below the disposal limit of chinese pollution control standards. The integration of SBR and E-Fenton were prefered to COD removal, while the integration of SBR and electrochemical oxidation technologies were prefered to ammonium removal.更多还原