【作者】 张景新；

【导师】 张耀斌； 全燮；

【作者基本信息】 大连理工大学 ， 环境工程， 2013， 博士

【摘要】 厌氧消化是处理中高浓度废水最现实、有效的方法之一。它将污水处理与污染物能源化相结合,在国内外得到广泛应用。但是,产甲烷菌代谢缓慢且对环境条件敏感,其容易导致水解酸化过程和甲烷化过程失衡,从而引起有机酸积累、甲烷化抑制甚至厌氧过程的失败。因此,有必要研究强化有机酸高效降解以及提高厌氧甲烷化能力的新方法,提高厌氧处理效率,这对解决高浓度难降解有机废水的有效处理和污染物资源化利用具有重要意义。针对以上问题,本论文利用零价铁的还原性和微生物异化铁(Ⅲ)还原的特性,将零价铁和三价铁分别置于厌氧反应器内用以强化厌氧消化的处理效果,重点开展了基于铁电极和铁氧化物的微生物电化学强化厌氧甲烷化技术的研究,考察了电化学强化技术、铁(0,Ⅲ)强化技术与厌氧生物处理的耦合关系和交互作用机制,结合分子生物学技术探索了铁(0,Ⅲ)和电与厌氧微生物之间的协同作用关系。主要研究内容和结果如下：(1)通过零价铁(ZVI)置于厌氧反应器内的方法有效增强了处理含硫酸盐废水过程中的厌氧甲烷化。结果表明,零价铁作为还原剂可有效缓冲酸性、维持厌氧体系中性的pH(7-8)从而减弱了硫酸盐还原产生的硫化氢对厌氧甲烷化的抑制作用,实现了较高的COD去除率和甲烷产量。分子生物学实验结果表明该反应器底部硫酸盐还原菌为优势菌而上部则以产甲烷菌为主导。该方法实现了微生物群落的功能化分区,这与两相厌氧反应器处理含硫酸盐废水较相似,却在单一反应器内实现。同时,这表明零价铁的加入有助于强化厌氧甲烷化过程。(2)采用将Fe203置于酸化硫酸盐还原反应器内的方法,强化了硫酸盐废水处理过程中有机酸的降解。研究结果发现Fe203的加入可促进微生物异化Fe(Ⅲ)还原过程,其协同硫酸盐还原过程增强了有机酸的降解能力,从而实现了酸化硫酸盐还原反应器较高的COD去除率(27.3%)和硫酸盐还原率(57.9%)。分子生物学的定性和定量分析结果表明该方法实现了铁还原菌、硫酸盐还原菌和酸化菌的共生并大量富集,其中硫酸盐还原菌Desulfovibrio marrakechensis和铁(Ⅲ)还原菌Iron-reducing bacteria HN54的含量均明显高于参比反应器。(3)由(1)部分可知,零价铁可促进厌氧甲烷化过程,基于此构建了使用铁电极为阳极的生物电解池(MEC)-上流式厌氧污泥床反应器(UASB)装置,即将一对铁-石墨电极置入厌氧反应器内并施以适当的电压。零价铁的加入可强化厌氧过程(包括强化厌氧还原氛围和厌氧菌生长),从而实现了其对含盐废水、染料废水和含氮废水的有效处理。此外,该反应器对有机废水的厌氧水解酸化过程也表现出了明显促进作用。针对含盐废水的处理,该反应器表现出了较高的耐盐能力和有机物降解能力。在较高盐度条件下(50g/L),该反应器(外加电压1.2V)的COD去除率达到了93%且有机酸去除率较高,而参比反应器的COD去除率降为53%且发生了严重的有机酸积累。分子生物学实验表明该反应器富集了大量的耐盐古菌和耐盐细菌且食丙酸盐细菌的丰度较高；针对高浓度偶氮染料废水(1200mg/L活性艳红X-3B)的处理,该反应器表现出了较高的脱色能力(83.4%)和COD去除能力(84.7%)。阳极腐蚀释放的Fe2+与电场的耦合作用强化了胞外聚合物的产生。微生物群落结构的动态分析表明基于铁电极的电场作用可显著加快微生物的富集速度,这对缩短反应器启动时间和增加反应器负荷具有重要意义；铁电极和电场的耦合作用明显提高了废水的水解酸化效率并优化产酸类型,实现了酸化相高效的COD去除并以产乙酸结构为主导。同时,铁电极作用下反应器的甲烷产量也有近两倍的提高。分子生物学的定性和定量分析结果表明基于铁电极的水解酸化反应器仍保留了大量古菌,其中食乙酸产甲烷菌相对含量较高,而参比无电极的反应器古菌含量相对较低且以食氢产甲烷菌为优势菌；基于铁电极的电催化作用可有效增强厌氧氨氧化(ANAMMOX)菌的富集,进而缩短ANAMMOX反应器的启动时间(近24%)。考察了不同电压对ANAMMOX脱氮的影响,在一定范围内增加电压(≤0.6V)有助于强化反应器的脱氮性能,但当电压超过一定的值(0.8V)将会减弱ANAMMOX反应器的脱氮能力。(4)由(2)部分可知,三价铁具有异化还原降解有机物和富集铁还原菌的特性,基于此通过在MEC-UASB反应器内投加氢氧化铁的方法,强化了厌氧消化和阳极氧化作用,实现了有机废水的高效降解。分子生物学实验结果表明氢氧化铁可增强反应器内细菌和古菌菌落的富集度和生物多样性,同时电场作用使得电极表面的微生物群落结构发生明显改变,这使得反应器内实现了不同功能微生物群落的垂直分布。此外,该方法对染料废水脱色也表现出较好的效果。酶活分析表明氢氧化铁与电场的耦合作用提高了微生物偶氮还原酶活性,其对废水脱色具有重要作用。在该反应器体系的阳极生物膜内富集并分离到了一株具有电化学活性的新型铁还原菌Aeromonas hydrophila.XB (KC507819)。该菌株同时具有铁还原、脱色和电化学活性。更多还原

【Abstract】 Anaerobic digestion (AD) is a desirable and widely used technology for high-strength organic wastewater treatment, simultaneously with the generation of bio-energy resources. Slow metabolism of methanogens and its sensitive characteristics to environmental perturbation are liable to cause the unbalance between acidogenesis and methanogenesis, thereby resulting in the accumulation of volatile fatty acids (VFAs), inhibition of methanogenesis and even failure of anaerobic process. Therefore, it is necessary to develop a new approach to enhance the effective degradation of VFAs and improve the ability of methanogenesis. This study is meaningful for efficient treatment of lugh concentration organic wastewater, bio-energy recovery and the application of AD in a wider field.To solve the above issues, we explored the performance and potential mechanisms of zero valent iron (ZⅥ) and Fe(Ⅲ) on the enhancement of AD, and we mainly focused on the study of microbial electrocatalysis of anaerobic methanogenesis system based on the iron electrode and Fe(Ⅲ) oxides. Furthermore, we also investigated the coupling effects among electrochemical technology, iron (0, Ⅲ) enhanced technology and anaerobic digestion, and clarified the synergistic relationships and mechanisms among Fe (0, Ⅲ), electricity and anaerobic microbial community. Main contents and results are as follows:(1) A novel method via dosing zero-valent iron (ZⅥ) into an anaerobic reactor significantly enhanced anaerobic methanogenesis in sulfate-containing wastewater treatment. The results showed that ZⅥ as a reducing agent could buffer acidity, maintain neutral pH(7-8) and reduce the inhibition of H2S generated from sulfate reduction on methanogenesis, resulting in high COD removal and methane production. Molecular biology analysis showed that the fractions of methanogens and SRB presented highest in the upper portion and the bottom of the ZⅥ-anaerobic reactor, respectively. This method realized the functionalized partitioning of microbial activities that was similar to a two-stage anaerobic reactor for sulfate-containing wastewater treatment, but in a single anaerobic reactor. The addition of ZⅥ in an anaerobic reactor helped to enhance anaerobic methanogenesis.(2) Based on the characteristics of microbial Fe(Ⅲ) reduction for the degradation of organics, a novel approach via dosing Fe2O3into an acidogenic sulfate-reducing reactor was developed to enhance the degradation of organic acids in the sulfate-containing wastewater treatment. The results showed that the addition of Fe2O3resulted in microbial reduction of Fe (Ⅲ), which enhanced the degradation of organic acids through assisting sulfate reduction process. In this way, high COD removal (27.3%) and sulfate reduction (57.9%) were realized. The qualitative and quantitative analysis of molecular biology revealed that this method realized the enrichment and symbiosis of iron reducing bacteria, sulfate reducing bacteria and acidogenic bacteria. Thereinto, the abundances of sulfate reducing bacteria Desulfovibrio marrakechensis and Iron-reducing bacteria HN54were significantly higher than that in the control reactor.(3) Using the characteristics of ZVI on the enhancement of anaerobic methanogenesis, a Fe anode-based microbial electrocatalysis cell (MEC)-upflow anaerobic sludge blanket reactor (UASB) was developed i.e. a pair of Fe-graphite electrodes was inserted into an UASB reactor with a proper voltage input. The addition of ZVI could strengthen the anaerobic process including the enhancement of anaerobic reducing atmosphere and the growth of anaerobic bacteria, further realizing the effective treatment of high salinity wastewater, dye wastewater and nitrogen-containing wastewater. In addition, this coupled reactor also enhanced acidogenic process of organics. For the high salinity wastewater treatment, this coupled reactor presented high salt-adapted ability and high degradation ability. Under the high salt condition, the COD removal of this coupled reactor reached93%while the COD removal of the control reactor was only53%and the accumulation of organic acids occurred. The molecular biology analysis indicated that a large amount of salt-adapted bacteria and archaea were enriched in this coupled reactor and the relative abundance of propionate-utilizing bacteria was higher. For the high azo dye wastewater treatment (1200mg/L reactive brilliant red X-3B), this coupled reactor showed high decolorization (83.4%) and COD removal (84.7%). The coupling effect of Fe2+generated from anode and electric field enhanced the production of extracellular polymer substances (EPS). The dynamic analysis of microbial community indicated that the coupling of Fe electrode and electric field significantly accelerated the enrichment of anaerobic bacteria, which was meaningful for shortening the start-up time and increasing organic loading. The coupling of Fe electrode and electric field significantly improved the efficiency of hydrolysis and optimized the composition of organic acids, realizing the high COD removal and the dominant acetate production. Additionally, the yields of methane of this coupled reactor was about two times higher than that of the control reactor. The qualitative and quantitative analysis of molecular biology indicated that a large amount of archaea was retained in this coupled reactor, in which the acetate-utilizing methanogens was dominant. From comparsion, the abundance of archaea in the control reactor was low and the hydrogen-utilizing methanogens was dominant. The Fe anode-based MEC-UASB reactor could enhance the enrichment of ANAMMOX bacteria, which further shortened the start-up time (about24%). Through investigating the effects of different voltage on the nitrogen removal of ANAMMOX, we discovered that raising the voltage applied for the electrode in a given extent (≤0.6V) enhanced the performance of the reactor, while a voltage more than0.8V reduced the anammox performance.(4) Using the characteristics of microbial Fe(III) reduction on the degradation of organics and the enrichment of iron reducing bacteria (IRB), a novel method via dosing Fe(OH)3into a MEC-UASB reactor enhanced both anaerobic digestion and anodic oxidation of organics, realizing the high treatment performance of organic wastewater. Molecular biology analysis indicated that the addition of Fe(OH)3increased the abundance and biodiversity of bacteria and archaea communities. Meanwhile, the effects of electric field changed the microbial community structure on the surface of electrodes, which created a vertical distribution of different functional microbial community in a single reactor. On the other hand, this method also presented high performance for color removal. Enzyme activity analysis showed that the coupling of Fe(III) and electric field could improve the activity of azoreductase that was important for the decolorization. Subsequently, a novel iron reducing bacteria (IRB) Aeromonas hydrophila. XB (KC507819) with electrochemical activity was isolated from the anodic biofilm of MEC-UASB reactor. The strain XB had the electrochemical activity, Fe(III) reducing activity and decolorization capacity.更多还原