预处理调解对剩余污泥发酵液微生物电解产氢影响研究

发布时间：2018-08-28 08:56

【摘要】：微生物电解池(MECs)由微生物燃料电池发展而来,具备能量输入低(与电解水产氢相比)、氢气产率高的特点。MECs主要利用乙酸盐产氢,但如何利用MECs处理实际废物且同步获得氢气成为目前研究的热点。剩余污泥的处理与处置是污水处理厂处理污水的同时急待解决的难题,传统厌氧处理污泥存在的问题是周期长、碳源转化速率慢、能源(甲烷)回收率低等。针对上述问题,提出了有效的污泥预处理方法-强化发酵产酸-微生物电解回收氢能的处置思路,将分别提升剩余污泥中的有机质水解酸化效率、强化挥发酸最适底物产量、提高氢气转化回收效率,从而实现剩余污泥梯级利用的高效碳源转化产氢新方法探索。本研究针对不同常用预处理方法制备污泥发酵液性质分析,主要针对发酵液有机物成分优化并确定在MECs反应器产氢工艺中不同有机质组分转化效能。实验结果表明,MECs反应器利用蛋白类物质产氢,在外加电压0.8 V条件下,蛋白质初始浓度800 mg COD/L时产氢率最高(0.3±0.015 ml/mg COD);发酵液中不同挥发酸组分对MECs产氢影响密切,丙酸积累不利于MECs反应器产氢,而丁酸积累则相对有利于MECs氢气产量提升。MECs处理污泥发酵液在初始p H值6.5、外加电压0.8 V以及电导率为8时,MECs产氢率最高。对于发酵液的离子含量决定的缓冲能力和电导率进行分析发现,碱预处理后产生的发酵液电导率能够提高从而有利于MECs产氢效率提升;适当磷酸盐(PBS)调节可有效的提高MECs反应器的运行效能。对于发酵过程产酸带来的酸化影响,通过酸性p H值冲击实验发现,p H5的酸性冲击会导致MECs产氢效率降低,产甲烷率增加。待p H恢复到中性后,MECs反应器中的微生物在反应器受到酸性冲击后多样性增加,而对于阳极菌群中胞外电子传递菌为优势菌的高效产氢反应器,在去除短暂酸性冲击后细胞色素C基因相关菌群能够较快恢复为优势菌,而与碳利用相关的功能基因中降解简单碳源功能基因变化最为显著。通过比较热预处理、碱预处理和热碱联合预处理污泥发酵液接种MECs反应器运行效能和产氢效率,发现热碱联合预处理污泥发酵液各种VFAs释放更充分,发酵液在MECs中乙酸利用率最高;污泥发酵液氢气回收效率分析表明热碱联合预处理污泥发酵液联合MECs产氢过程获得氢气回收效率最高,单位污泥氢气产量34.4±4.1 m L H_2/g VSS,每日氢气产量为19.3±2.3 m L H_2/d。按照不同预处理发酵液的MECs产氢效率的大小比较:热碱联合预处理热预处理碱预处理未预处理污泥。针对MECs处理污泥发酵液产甲烷对MECs氢气回收率损耗影响,提出了通过污泥预处理过程增加适量微氧曝气形成对MECs中产甲烷菌有效抑制的方法,结果证明了短期曝气有效提高MECs处理污泥发酵液回收氢气。一方面,通过污泥预处理过程中适当微氧曝气预处理可以提升剩余污泥水解过程的有机物释放,结果证明了碱处理条件增加适量微氧预处理更有利于污泥发酵液中总挥发性脂肪酸(TVFAs)的积累。另一方面,MECs利用污泥发酵液产氢运行阶段,在序批式运行过程直接采用对MECs生物膜短期(10 min)空气暴露方式可有效抑制甲烷的产生,产氢回收率提高60%,氢气产率达到1.3 m L H_2/m L反应器/d。通过高通量测序发现,通过微氧-热碱联合预处理制备剩余污泥发酵液联合单室MECs反应器产氢过程的微生物群落结构变化以厌氧发酵菌群最为显著,结果表明β-Proteobacteria、Legionella和Clostridium为MECs反应器运行过程中主要的微生物菌群,其中Clostridium从启动时的4.1%增加到产氢阶段的19.3%,Solobacterium增加至10.5%;与微生物电极系统电子传递过程密切相关β-Proteobacteria略有降低,在反应器产氢效率最高时β-Proteobacteria占21.3%。研究结果初步揭示了体系氢气回收效率与剩余污泥发酵液联合微生物电解产氢过程厌氧发酵菌群与MEC电极功能菌群的相互作用过程的内在关联。
[Abstract]:Microbial electrolysis cells (MECs) are developed from microbial fuel cells (MFCs), which have the characteristics of low energy input (compared with hydrogen production from electrolytic water) and high hydrogen production rate. MECs mainly use acetate to produce hydrogen. However, how to use MECs to treat real waste and obtain hydrogen simultaneously has become a hot research topic. The problems of traditional anaerobic sludge treatment are long cycle, slow carbon source conversion rate and low recovery rate of energy (methane). Aiming at these problems, an effective sludge pretreatment method-enhanced fermentation and acid production-microbial electrolysis to recover hydrogen energy is proposed, which will enhance the residual sludge separately. In this study, the characteristics of sludge fermentation broth prepared by different pretreatment methods were analyzed, and the organic components of fermentation broth were optimized and optimized. The conversion efficiency of different organic matter components in MECs reactor was determined. The experimental results showed that the hydrogen production rate of MECs was the highest when the initial concentration of protein was 800 mg COD/L under the applied voltage of 0.8 V, and different volatile acid components in fermentation broth had a close effect on the hydrogen production of MECs. Accumulation of acid was disadvantageous to hydrogen production in MECs, but accumulation of butyric acid was relatively beneficial to the increase of hydrogen production in MECs. The hydrogen production rate of MECs was the highest when initial P H value was 6.5, applied voltage was 0.8 V and conductivity was 8. The conductivity of raw fermentation broth can be improved and the hydrogen production efficiency of MECs can be improved. Proper phosphate (PBS) regulation can effectively improve the operation efficiency of MECs reactor. When P H returned to neutrality, the diversity of microorganisms in the MECs reactor increased after acid shock, while for the high-efficiency hydrogen production reactor, in which extracellular electron-transporting bacteria were the dominant bacteria, the cytochrome C gene-related bacteria could recover to the dominant bacteria quickly after removal of short acid shock, which was related to carbon utilization. Compared with thermal pretreatment, alkali pretreatment and thermo-alkali pretreatment of sludge fermentation broth inoculated with MECs reactor, the results showed that the VFAs released more fully and the acetic acid utilization rate of fermentation broth was the highest in MECs. The hydrogen recovery efficiency analysis of sludge fermentation broth showed that the hydrogen recovery efficiency of the combined pretreatment sludge fermentation broth with MECs was the highest, and the hydrogen yield per unit sludge was 34.4 +4.1 m L H_2/g VSS, and the hydrogen output per day was 19.3 +2.3 m L H_2/d. In view of the effect of methane production from sludge fermentation broth treated with MECs on the hydrogen recovery rate of MECs, a method of increasing appropriate amount of micro-oxygen aeration formation in sludge pretreatment process to effectively inhibit methanogens in MECs was proposed. The results showed that short-term aeration could effectively increase the methanogens in MECs treatment sludge. Hydrogen recovery from fermentation broth. On the one hand, the release of organic compounds in the hydrolysis process of excess sludge can be enhanced by appropriate micro-oxygen aeration pretreatment during sludge pretreatment. The results show that the accumulation of total volatile fatty acids (TVFAs) in sludge fermentation broth can be improved by adding appropriate micro-oxygen pretreatment under alkali treatment conditions. In the operation stage of hydrogen production, short-term (10 min) air exposure to MECs biofilm could effectively inhibit methane production. The recovery rate of hydrogen production increased by 60% and the hydrogen yield reached 1.3 m L H_2/m L reactor/d. Anaerobic fermentation was the most significant microbial community in the combined single-chamber MECs reactor. The results showed that beta-Proteobacteria, Legionella and Clostridium were the main microbial community during the operation of MECs reactor. Clostridium increased from 4.1% at the start-up stage to 19.3% at the hydrogen production stage, and Solobacterium increased to 19.3%. 10.5%; the beta-Proteobacteria closely related to the electron transfer process of microbial electrode system decreased slightly, and the beta-Proteobacteria accounted for 21.3% at the highest hydrogen production efficiency of the reactor. The results preliminarily revealed the anaerobic fermentation flora and the MEC electrode functional flora in the process of hydrogen recovery efficiency of the system and surplus sludge fermentation broth combined with microbial electrolysis. The internal relationship of the interaction process.
【学位授予单位】：哈尔滨工业大学
【学位级别】：博士
【学位授予年份】：2016
【分类号】：X703;TM911.45

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