【作者】 陈莹；

【导师】 朱南文；

【作者基本信息】 上海交通大学 ， 环境科学与工程， 2016， 硕士

【摘要】 传统的污泥厌氧消化技术存在污泥生物可降解性能低、设施占地大、停留时间长、产气率及产气量较低等缺点。本课题组在前期预实验中发现,在剩余污泥厌氧消化过程中施加低强度的直流电压,能够明显提高厌氧消化甲烷产量及挥发性固体有机物（VS）去除率。本论文基于以上研究背景,以城市污水处理厂剩余污泥为对象,在污泥厌氧消化过程中施加不同强度的直流电压,考察电场对剩余污泥厌氧消化效果的影响并筛选出最佳刺激电压,同时对电刺激提高污泥厌氧消化效果的机理进行了分析。其次在最佳刺激电压下,考察污泥初始浓度和初始pH值对剩余污泥厌氧消化效果的影响,并对消化过程中上清液各组分变化情况及微生物种属演化规律进行了比较分析。主要得出以下研究结果:（1）在剩余污泥厌氧消化过程中施加不同强度直流电场（0 V,0.3 V,0.6 V,0.9 V,1.2 V,1.5 V）,结果表明除0.9 V电压外,其他强度的直流电压均能提高剩余污泥厌氧消化甲烷产率及VS去除率。0.6 V电压下刺激效果最好,在该电压下,甲烷产率和VS去除率比对照组分别提高了76.2%和26.6%。当直流电压小于0.6 V时,电场对微生物新陈代谢有促进作用,能够提高剩余污泥厌氧消化效能;当电压为0.9 V时,电场对微生物新陈代谢有抑制作用,厌氧消化产气效果不理想;当电压为1.2 V和1.5 V时,水电解形成微好氧环境,促进污泥水解酸化,提高后续污泥厌氧消化甲烷产量。通过分析消化过程中SCOD、蛋白质、碳水化合物和挥发性脂肪酸（TVFAs）浓度变化情况,发现各电压强度均能不同程度地提高剩余污泥的水解和酸化速率。（2）电压对于厌氧消化过程中微生物种群结构变化有明显影响。0.9 V电压作用下微生物多样性降低,种群结构趋于简单,其余电压均能明显提高微生物多样性及种群丰度。在细菌种属水平上,0.3 V电压下不动杆菌属（Acinetobacter）为系统中的优势菌,其所占比例明显高于其他组;0.6 V电压下假单胞菌属（Pseudomonas）占优势,其丰富度比其他组高。在古菌水平上,当施加电压小于0.6 V时,乙酸发酵型产甲烷菌是甲烷菌中的优势菌;而当电压高于0.6 V时,嗜氢产甲烷菌则占优势。（3）在最佳刺激电压（0.6 V）作用下,污泥初始浓度（15 g/L,25 g/L,35 g/L,45 g/L）对厌氧消化效果有明显影响。当污泥浓度为35 g/L时,甲烷产率为139.4 mLCH₄/g-VS,VS去除率为46.7%,厌氧消化效果最好。而相同消化时间内,当污泥浓度为45 g/L时,TVFAs积累严重,较高的TVFAs和氨氮浓度抑制了产甲烷菌活性,其甲烷产率仅为16 mLCH₄/g-VS,产气基本停滞。污泥初始浓度对消化过程中SCOD浓度、TVFAs浓度、氨氮浓度和pH值的变化有明显影响。改变污泥初始浓度对厌氧消化过程中细菌种群结构的变化有明显影响,对产甲烷菌的结构的影响不明显。当污泥的初始浓度为45 g/L时,水解和酸化细菌种类比其他组丰富,导致消化前期水解酸化速率高,有机酸大量积累,不利于后续产甲烷。四个反应器中的优势产甲烷菌均为甲烷鬃毛菌属,且各组之间甲烷鬃毛菌属的丰富度差异不显著。（4）在最佳刺激电压（0.6 V）下,污泥初始pH（3,5,7,9,11）对厌氧消化效果有明显影响。不调节pH时,VS去除率为32.21%,甲烷产率为162 mLCH₄/g-VS;而相同消化时间内,调节污泥初始pH值为9时,甲烷产率高达224 mLCH₄/g-VS,同时VS去除率高达38.07%,厌氧消化效果最好。调节污泥初始pH值为11时,TVFAs积累严重,且氨氮浓度高,VFAs和游离氨抑制了产甲烷菌的活性,产气基本停滞。初始pH对污泥的水解酸化过程有比较明显的影响。在产酸高峰期,初始pH为3、11时,乙酸和丁酸是主要产物;初始pH为5、7、9时,主要产物是乙酸和丙酸。调节污泥初始pH不会影响整个系统pH的自然平衡过程;较低的污泥初始pH会加速厌氧消化过程中氨氮的释放。更多还原

【Abstract】 Anaerobic digestion of waste activated sludge（WAS）is a cost-effective and sustainable technology to realize sludge stabilization,mass reduction and methane production simultaneously.However,the application of conventional anaerobic digestion is often limited by its long retention time,low removal efficiencies of organic compounds and low biogas production rate.Electrical stimulation refers to a microbial process performed in the presence of electrolysis by low direct current.The operation of electrical stimulation is easy and energy conservation.Therefore,the potential for practical application of electrical stimulation to microbial processes is high.Meanwhile electrical stimulation is a green and environment friendly technology.Electrical stimulation has been applied in sewage treatment,groundwater purification and soil remediation.However,applying electrical stimulation in sludge anaerobic digestion under practical conditions was still limited,and the relationship between stimulating effects and applied voltage was not established to date.In this study,different voltages（0.3 V-1.5 V）were applied to investigate the influence of electrical stimulation on anaerobic digestion of WAS.Firstly,the best performance in terms of methane production and sludge reduction was obtained with the applied voltage of 0.6 V.Secondly,the effect of WAS concentration（15 g/L,25 g/L,35 g/L,45 g/L）and initial pH（3,5,7,9,11）on anaerobic digestion performance under 0.6 V direct electrical stimulation were investigated.The main conclusions are as follows:（1）Different voltages（0.3 V-1.5 V）were applied to investigate the influence of electrical stimulation on anaerobic digestion of WAS.The results revealed that applied voltages could accelerate sludge hydrolysis and acidification process.The best performance in terms of methane production and sludge reduction was obtained with the applied voltage of0.6 V.In this case,methane production increased by 76.2%with an enhanced VS removal rate（26.6%）compared to the control group.The energy consumption at 0.6 V could be neglected compared to the incremental energy generated from the methane.However,methane production decreased and hydrogen was produced when the applied voltage increased to 0.9 V.At higher voltages（1.2 V and 1.5 V）,more soluble organic matters were released.In particular,the VFAs concentration peaked at 640 mg/L and 1001 mg/L,respectively.（2）Pyrosequencing revealed that hydrogenotrophic methanogens consisted majority of methanogen population when the applied voltages was over 0.6 V,while acetoclastic methanogens showed overwhelming dominance at 0.3 V.Moreover,0.6 V enriched Pseudomonas for protein degradation and Methanoregula for methane generation with species richness of 19.1%and 53.3%,respectively.（3）Batch tests were operated to investigate effects of WAS concentration（15 g/L,25 g/L,35 g/L,45 g/L）on anaerobic digestion of waste activated sludge under 0.6V direct electrical stimulation.The results showed that WAS concentration had a great influence on biogas production and VS removal efficiency.At the optimal concentration of 35 g/L,maximum methane yield of 139.4 mLCH₄/g-VS and VS removal efficiency of 46.7%were achieved after 35 days digestion.At higher WAS concentration（35 g/L,45 g/L）,the SCOD,VFAs and ammonia from WAS were increased in quantities.In particular,at concentration of 45 g/L,the VFAs concentration peaked at 12,000 mg-COD/L and the methanogenesis was inhibited.The bacteria communities were enriched at concentration of45 g/L,which was in agreement with the result of SCOD and VFAs concentrations.Methanobacterium,Methanosaeta,Methanoculleus,Methanospirillum and Methanobrevibacter were dominated methanogens in these four samples.（4）Batch tests were operated to investigate effects of initial pH（3,5,7,9,11）on anaerobic digestion of waste activated sludge under 0.6 V direct electrical stimulation.The results showed that initial pH had a great influence on biogas production and VS removal efficiency.At the optimal initial pH of 9.0,maximum methane yield of 224 mLCH₄/g-VS and VS removal efficiency of 38.1%were achieved after 32 days digestion.Initial pH could accelerate hydrolysis and acidification process of waste activated sludge.Alkaline environment（pH 9,11）enhanced SCOD and VFAs concentrations in suspensions,especially at pH 11.Acetic acid and butyric acid were dominant at pH 3 and 11 while acetic acid and propionic acid were main products at pH 5,7 and 9.Initial pH facilitates release of ammonium from waste activated sludge and in acidic environment ammonium was released in excess.更多还原