【作者】 张吉强；

【导师】 郑平；

【作者基本信息】 浙江大学 ， 环境工程， 2014， 博士

【摘要】 面对环境污染和能源短缺的双重压力,传统高能耗的废水处理技术已难以满足可持续发展的要求。微生物燃料电池(Microbial fuel cell, MFC)以微生物为催化剂将废水中污染物蕴含的化学能直接转化为电能,可实现同步治污产电。但迄今为止,MFC研究主要集中在有机废水方面。在氮素污染凸现的今天,研发兼具脱氮产电功能的MFC对废水处理具有重大的现实意义。本文创建阳极反硝化微生物燃料电池(Anodic denitrification MFC, AD-MFC)和厌氧氨氧化微生物燃料电池(Anaerobic ammonium oxidation MFC, ANAMMOX-MFC),系统而深入地研究了AD-MFC和ANAMMOX-MFC的脱氮产电性能、影响因素和工作机理,主要结果如下：1)创建了AD-MFC,探明了其同步反硝化产电性能。以反硝化菌富集培养物为生物催化剂,成功创建AD-MFC,实现了同步反硝化产电。AD-MFC具有良好的脱氮产电性能。在批式试验中,初始硝氮浓度和COD浓度分别为100.22±0.62mg/L和500.40±1.67mg/L, AD-MFC的最大容积反硝化速率、最大电压和最大功率密度分别达到0.31±0.01kgN/m3·d、602.80±5.42mV和908.42±0.07mW/m3。AD-MFC的产电过程呈现阶段性变化。由于阳极液中主导反应(反硝化、甲醇降解、内源呼吸和细胞水解发酵)依次演替,阳极电极电势不断变化,导致电压曲线呈现“降低-升高-再降低”的三阶段过程特性,未见国内外相关文献报道。AD-MFC蕴藏指示功能。硝氮消耗、COD消耗与电压损耗的Pearson相关系数分别达到0.9964和0.9917,电压变化与反硝化基质浓度变化呈显著线性相关,电信号可指示反硝化进程。2)考察了基质浓度对AD-MFC脱氮产电性能的影响,揭示了AD-MFC污染物降解和产电动力学规律。AD-MFC脱氮产电性能与基质浓度密切相关。在低浓度范围,提高基质浓度可提高微生物活性,强化AD-MFC脱氮产电能力,但在高基质浓度范围,基质产生自抑制,削弱AD-MFC脱氮产电能力。AD-MFC基质降解和产电动力学过程符合Han-Levenspiel模型。以该模型拟合得到的NO3-N降解、COD降解、输出电压、功率密度的最大值(rmax)、半饱和常数(Ks)和完全抑制浓度(Sm)分别为1.27kg N/m3·d.351.63mg/L和4301.25mg/L;5.14kgCOD/m3·d.1950.21mg/L和20050.69mg/L;1030.53mV.203.25mg/L和4950.36mg/L;1386.39mW/m3、293.47mg/L和4649.03mg/L。NO3--N半饱和常数(Ks)大于200mg NO3--N/L,完全抑制浓度(Sm)大于4000mg NO3--N/L,表明AD-MFC对高基质浓度具有较强的耐受性。AD-MFC适用于高浓度硝酸盐有机废水的除污和产电。初始NO3-N浓度和COD浓度分别为1999.95±2.86mg/L和10058±1.26mg/L时,最大反硝化速率、最大电压和最大功率密度分别达1.26±0.01kg N/m3·d、1016.75±4.74mV和1314.41±24.60mW/m3.其容积脱氮速率处于国内外文献报道的较高水平。3)分析了AD-MFC物质转化特性、微生物功能空间分布、电子传递机制和功能菌群组成,揭示了AD-MFC工作机理。AD-MFC产电过程与反硝化相耦合。单独以甲醇或硝酸盐作为基质时,两者不能被有效降解,AD-MFC产电能力也有限；只有当两者共存时,AD-MFC才能发挥脱氮产电效能。阳极上的生物膜和阳极液中的悬浮污泥均具有脱氮产电功能,其功能空间小于AD-MFC的总体功能空间,AD-MFC反硝化脱氮过程由电极生物膜和悬浮污泥协作完成。电极生物膜和悬浮污泥的反硝化功能空间分别为41.90%和67.98%,产电功能空间分别为52.26%和69.03%,悬浮污泥在AD-MFC功能空间中占据优势。电极生物膜和悬浮污泥具有不同的电子传递机制。电极生物膜主要依靠直接接触的方式进行电子传递；而悬浮污泥在不同反应阶段可产生多种中介体,主要依靠中介体为媒介进行电子传递。AD-MFC中功能菌群组成差异较大。接种污泥含有大量的球菌、杆菌和丝状菌,而电极生物膜主要为丝状菌和杆菌,悬浮污泥主要为球菌和丝状菌。菌群结构随产电过程发生演替,悬浮污泥和电极生物膜中微生物种类较接种污泥明显减少。AD-MFC中的优势菌群归属于γ-变形菌纲、p-变形菌纲、拟杆菌纲和Ignavibacteria纲,功能菌群主要为反硝化菌。4)创建了ANAMMOX-MFC,探明了其同步厌氧氨氧化产电性能。以ANAMMOX菌富集培养物作为生物催化剂,成功创建ANAMMOX-MFC,实现了同步厌氧氨氧化产电。ANAMMOX-MFC具有良好的脱氮产龟性能。在连续试验中,进水NH4+-N和N02--N浓度分别从25mg/L和33mg/L逐渐提升至250mg/L和330mg/L时,NH4+-N、 NO2--N和TN去除率分别保持在90%、90%和80%以上,容积脱氮速率最大可达3.01±0.27kg N/m3·d,最大电压和最大功率密度可达225.48±10.71mV和1308.23±40.38mW/m3,是目前文献报道的最高MFC脱氮负荷。ANAMMOX-MFC阳极极化显著,阳极电荷传递电阻约占ANAMMOX-MFC总电阻的60%,是限制ANAMMOX-MFC产电的瓶颈因素。ANAMMOX-MFC也蕴含指示功能。在一定范围内(25mg/L～250mg/L),输出电压随进水NH4+-N浓度线性变化,可以指示NH4+-N浓度,这种指示功能主要来自于不同NH4+-N浓度所致的氨氧化速率变化。5)考察了温度、pH和中介体对ANAMMOX-MFC脱氮产电性能的影响,优化了ANAMMOX-MFC的操作条件。温度可显著影响ANAMMOX-MFC的脱氮产电性能。ANAMMOX-MFC脱氮产电的最适温度约为30℃；高于或低于此温度时,容积脱氮速率和输出电压同步降低；温度变化引起生物反应变化是导致ANAMOX-MFC产电性能变化的主要原因。pH也可影响ANAMMOX-MFC的脱氮产电性能。ANAMMOX-MFC脱氮产电的最适pH为7～8；pH影响ANAMMOX-MFC容积脱氮速率和输出电压的同步性较低；pH所致的生物反应变化和阳极电极电势变化共同引发了ANAMMOX-MFC产电性能变化。中介体可强化ANAMMOX-MFC产电性能。低浓度(<0.01mmol/L)的中性红、2-羟基-1,4-萘醌和吩噻嗪等对应电子传递链前端、分子量较小、结构简单的中介体,可有效降低阳极电荷转移电阻,显著强化ANAMMOX-MFC产电性能；而灿烂甲酚蓝和血红素等对应电子传递链后端、分子量较大、结构相对复杂的中介体,对ANAMMOX-MFC产电性能的强化作用较弱；中介体浓度过高(0.01～0.02mmol/L)会抑制生物反应,致使ANAMMOX-MFC产电能力不升反降。6)研究了ANAMMOX-MFC的物质转化特性、功能菌群组成、微生物功能空间分布和电子传递机制,揭示了ANAMMOX-MFC工作机理。ANAMMOX-MFC产电过程与ANAMMOX反应相耦合。单独以氨或亚硝酸盐作为基质时,ANAMMOX菌富集培养物发生水解,脱氮产电过程无法维持；氨氧化与亚硝酸盐还原相耦合,只有当氨和亚硝酸盐共同作为产电基质时,ANAMMOX-MFC才能持续发挥脱氮产电功能。阳极上的生物膜和阳极液中的悬浮污泥均具有同步厌氧氨氧化产电功能,ANAMMOX-MFC脱氮产电过程也由电极生物膜和悬浮污泥协同完成。ANAMMOX-MFC中电极生物膜和悬浮污泥分别在不同的功能空间中占据优势,电极生物膜和悬浮污泥的厌氧氨氧化功能空间分别为30.14%和53.43%,产电功能空间分别为59.52%和47.87%。电极生物膜和悬浮污泥具有不同的电子传递机制。电极生物膜主要依靠直接接触方式进行电子传递；而悬浮污泥主要依靠中介体为媒介进行电子传递,基质中的NO2-N组分可作为潜在的中介体,悬浮污泥自身也可产生中介体。ANAMMOX-MFC中的功能菌群组成存在一定差异。电极生物膜上的ANAMMOX菌厌氧氨氧化体更大,铁颗粒数量较多,血红素c含量较高,胞外多聚物(Extracellular polymeric substances,EPS)含量较少,有助于增强胞外电子传递能力。悬浮污泥中的微生物种类与接种污泥类似,而电极生物膜中的微生物种类与接种污泥差异较大。ANAMMOX-MFC中的优势菌群归属于p-变形菌纲、γ-变形菌纲、酸杆菌纲、Ignavibacteria纲和浮霉状菌门,功能菌群是由ANAMMOX菌、反硝化细菌和其他多种细菌组成的共生体系。更多还原

【Abstract】 Under the dual pressures of environmental pollution and energy shortage, it is obvious that conventional energy-intensive wastewater treatment processes do not meet the requirements of sustainable development any longer. Microbial fuel cell (MFC) is an emerging technology that directly converts chemical energy stored in wastewater to electricity, purifying wastewater and generating electricity simultaneously, which is considered as an attractive option for sustainable wastewater treatment. So far, however, most of the MFC research has been focused on organic wastewater treatment. Since nitrogen pollution is becoming a serious environmental problem, it is significant to develop MFC that can simultaneously remove nitrogen and recovery electricity from wastewater.In this research, the anodic denitrification MFC (AD-MFC) and the anaerobic ammonium oxidation MFC (ANAMMOX-MFC) were developed and their performances, operational parameters and working mechanisms were studied to achieve high-efficient nitrogen removal and electricity generation. The main results are as follows:1) The AD-MFC was constructed and its performances of simultaneous denitrification and electricity production were investigated.It was proved that the AD-MFC could be successfully started up with denitrifying bacterial enrichment culture as inoculum. The AD-MFC had good performances of nitrogen removal and electricity generation. In batch mode, when the initial nitrate and COD concentrations were100.22±0.62mg/L and500.40±1.67mg/L, the maximum denitrification rate, the maximum output voltage and the maximum power density were0.31±0.01kg N/m3·d,602.80±5.42mV and908.42±0.07mW/m3, respectively. The voltage curves of the AD-MFC showed three-phase characteristics of descend phase, ascend phase and redescend phase, which could be attributed to the succession of denitrification, methanol degradation, endogenous respiration and cell hydrolysate fermentation as dominant reactions in the anolyte. This phenomenon has never been reported before in literatures. The AD-MFC also had sensor function. The Pearson correlation coefficients between the voltage loss and the consumed nitrate and the consumed COD were0.9964and0.9917, respectively, which suggested that the voltage variation was closely related to the change of substrate concentration and the voltage could indicate the denitrification course.2) The influence of substrate concentration on the performance of the AD-MFC was explored, and kinetic characteristics of substrates degradation and electricity generation in the AD-MFC were revealed.It was discovered that both of nitrogen removal and electricity generation performances were closely related to the substrate concentration. Nitrogen removal rate and power generation could be promoted with increasing substrate concentration in a certain range (50-2000mg NO3--N/L), but they would be inhibited at high substrate concentrations (over2000mg NO3--N/L). Han-Levenspiel model could well describe the kinetic characteristics of the AD-MFC. Based on Han-Levenspiel model, the maximal value (rmax), the half-saturation coefficient (Ks) and the critical inhibitory concentration (Sm) for nitrate degradation, COD degradation, output voltage and power density were1.27kg N/m3·d,351.63mg/L and4301.25mg/L;5.14kg COD/m3·d,1950.21mg/L and20050.69mg/L:1030.53mV,203.25mg/L and4950.36mg/L;1386.39mW/m3,293.47mg/L and4649.03mg/L, respectively. According to the kinetic model, the half-saturation coefficient and the critical inhibitory concentration for nitrate were more than200mg/L and4300mg/L, respectively. The results demonstrated that AD-MFC was tolerant to high strength nitrate-containing wastewater. When the initial nitrate and COD concentrations were1999.95±2.86mg/L and10058±1.26mg/L, the maximum denitrification rate, the maximum output voltage and the maximum power density could be as high as1.26±0.01kgN/m3·d,1016.75±4.74mV and1314.41±24.60mW/m3, respectively. The volumetric nitrogen removal rate was much higher than that reported in literatures. 3) The substance transformation, microbial functional space, electron transfer pathway and functional microbial community were studied to reveal the working mechanism of the AD-MFC.It was found that electricity genaration was coupled to denitrification in the AD-MFC. Methanol or nitrate could not be effectively degraded as sole substrate, and electricity production capacity was very low. Only when methanol and nitrate coexist, could the AD-MFC achieve simultaneous denitrification and electricity production. Both the biofilm on the anode and the suspended sludge in the anolyte had the ability for denitrification and electricity production. The functional space of the anode biofilm and the suspended sludge was smaller than the total functional space of the AD-MFC, which suggested the anode biofilm and the suspended sludge both contributed to denitrification and electricity production. The suspended sludge was predominant in the functional space of the AD-MFC, and the functional spaces of the anode biofilm and the suspended sludge for denitrification and for electricity production were41.90%and67.98%,52.26%and69.03%, respectively. The electron transfer pathways of the anode biofilm and the suspended sludge were different. The electron transfer of anode biofilm was mainly realized by the direct contact to the electrode, while the suspended sludge relied on endogenous mediators for electron transfer. There was a great difference between the functional microbial populations. The seed sludge involved large amounts of cocci, bacilli and filamentous bacteria, while the anode biofilm mainly involved bacilli and filamentous bacteria, and the suspended sludge mainly involved cocci and bacilli. It was found that succession of bacterial communities occurred along with power generaion process, and the population diversity in the anode biofilm and the suspended sludge was significantly fewer than that in the seed sludge. The predominant bacterial populations in the AD-MFC belonged to y-proteobacteria,(3-proteobacteria, Bacteroides and Ignavibacteria, and the functional bacteria were mainly denitrifying bacteria.4) The ANAMMOX-MFC was constructed and its performances of simultaneous anaerobic ammonium oxidation and electricity production were investigated.It was proved that the ANAMMOX-MFC could be successfully started up with ANAMMOX bacterial enrichment culture as inoculum. The ANAMMOX-MFC also had good performances of nitrogen removal and electricity generation. Under continuous operation, when the initial ammonia and nitrite concentrations increased from25mg/L and33mg/L to250mg/L and330mg/L, the removal efficiencies of the total nitrogen, ammonia and nitrite were always above90%,90%and80%, respectively. Meanwhile, the maximum nitrogen removal rate, the maximum output voltage and the maximum power density were3.01±0.27kg N/m3·d,225.48±10.71mV and1308.23±40.38mW/m3, respectively. The volumetric nitrogen removal rate was the highest reported value so far. It was found that the polarization resistance of the anode was significant, accounting for60%of the total ANAMMOX-MFC internal resistance, which was the bottleneck for electricity production in the ANAMMOX-MFC. The ANAMMOX-MFC also had sensor function. The output voltage changed linearly with the variation of ammonia concentration in a certain range (25mg/L-250mg/L), which might mainly caused by the changed ammonia oxidation rate.5) The influences of temperature, pH and exogenous mediators on the performance of the ANAMMOX-MFC were explored, and the critical operational parameters for the ANAMMOX-MFC were optimized.It was discovered that temperature could significantly affect the performances of both nitrogen removal and electricity generation in the ANAMMOX-MFC, and the optimum temperature was about30℃. When the temperature was above or below30℃, the nitrogen removal rate and output voltage would decrease at the same time. The change of biological reaction responding to the changed temperature was the primary cause of the varied power output. The pH could also significantly affect the performances of both nitrogen removal and electricity generation in the ANAMMOX-MFC and the optimum pH was about7-8, but the changed degrees of nitrogen removal rate and output voltage were not so consistent compared with the temperature influence. The changes of biological reaction and anode potential responding to the changed pH was the common causes of the varied power output. The addition of exogenous mediators could enhance the electricity generation in the ANAMMOX-MFC. In the range of low concentrations (<0.01mmol/L), exogenous mediators such as neutral red,2-Hydroxy-1,4-naphthoquinone and phenothiazine which corresponding to the front of the electron transport chain, with small molecular weight and simple molecular structure would effectively reduce the anode charge transfer resistance and enhance power production in the ANAMMOX-MFC. While exogenous mediators such as brilliant cresyl blue and heme which corresponding to the end of electron transport chain, with large molecular weight and complex molecular structure, the enhancement effect of power production was not so obvious. However, when the concentrations of exogenous mediators were too high (0.01-0.02mmol/L), the biological reaction would be inhibited and the output voltage in the ANAMMOX-MFC would fell rather than rose.6) The substance transformation, microbial functional space, electron transfer pathway and functional microbial community were also studied to reveal the working mechanism of the ANAMMOX-MFC.It was proved that electricity genaration was coupled to ANAMMOX in the ANAMMOX-MFC. When ammonia or nitrite was as the sole substrate, ANAMMOX enrichment culture would hydrolyzed and the nitrogen removal and electricity production processes could not be sustained. The ammonia oxidation was coupled to the nitrite reduction, only when ammonia and nitrite coexist, could ANAMMOX-MFC sustain simultaneous anaerobic ammonium oxidation and electricity production. Both the biofilm on the anode and the suspended sludge in the anolyte had the ability for ANAMMOX and electricity production, and they both contributed to ANAMMOX and electricity production processes. The anode biofilm and the suspended sludge dominated different functional spaces of the ANAMMOX-MFC, and the functional spaces of the anode biofilm and the suspended sludge for ANAMMOX and for electricity production were30.14%and53.43%,59.52%and47.87%, respectively. The electron transfer pathways of the anode biofilm and the suspended sludge were also different in the ANAMMOX-MFC. The electron transfer of anode biofilm was mainly realized by the direct contact to the electrode, while the suspended sludge relied on endogenous mediators or nitrite as the potential mediator for electron transfer. There was certain difference between the functional microbial populations in the ANAMMOX-MFC. The ANAMMOX bacteria on the anode had larger anammoxosome, more iron particles, more heme c and less extracellular polymeric substances (EPS), which would facilitate the extracellular electron transfer. It was found that the microbial species in the suspended sludge were similar to that in the seed sludge, but the microbial species in the anode biofilm was significantly different from that in the seed sludge. The predominant bacterial populations in the ANAMMOX-MFC belonged to β-proteobacteria, y-proteobacteria, Acidobacteria, Ignavibacteria and Planctomycetes, and the functional microbial communities were consisted of ANAMMOX bacteria, denitrifying bacteria and a variety of other bacteria.更多还原