【作者】 方丽；

【导师】 李小明；

【作者基本信息】 湖南大学 ， 环境工程， 2010， 硕士

【摘要】 能源是当今世界的一个重要问题,随着人类活动的增加天然能源被逐渐消耗,导致了化石燃料枯竭和全球变暖。随着能源危机的日益严重,人们纷纷把眼光投向了可再生能源技术以及可变废为宝的能源技术。利用微生物作为催化剂将储存在有机物中的化学能转变成为电能的装置叫做微生物燃料电池(Microbial full Cell,MFC)。由于所用原料可以是有机高浓度废水、城市垃圾或者污水处理厂的剩余污泥,来源丰富价格低廉且不消耗矿物资源而且能有效降解污染物,因此微生物燃料电池越来越受到人们的关注。活性剩余污泥中含有丰富的有机物质如蛋白质、多糖类和脂肪类等是一种极具潜力的生物燃料。利用剩余污泥直接作为MFC燃料的研究已经不少,但是目前利用直接剩余污泥作为微生物燃料电池产电所获得的输出功率密度非常小。为了进一步提高电池输出功率密度本研究首次将污泥预处理技术与MFC技术联合起来。将微波预处理的污泥上清液作为微生物燃料电池的底物通过接种剩余污泥为燃料的微生物燃料电池的细菌悬液后成功启动了单室无膜微生物燃料电池。考查了微波时间和功率对微生物燃料电池最大输出功率密度的影响、可能影响输出功率密度的相关因素以及一个周期内燃料性质变化规律并且对不同外接电阻下MFC阳极表面附着的微生物形态差异进行了分析。结果表明长时间和适度较高的微波功率(<900W)能够有效提高MFC的产电能力,在最佳微波处理条件(300s,720W)时输出功率密度可达306.2mW·m-2；电池阳极面积越大,输出功率密度反而越小。阴阳极距离从5.0cm缩小到0.5cm时,输出功率密度先增加后降低,在距离为2.0cm时输出功率密度达到最大值282.7mW·m-2,说明阴阳极距离过近时溶解氧可能通过空气阴极传递到阳极影响了阳极表面上厌氧微生物的活性。采用NaCl作为离子添加剂时,随着投加量的增加,内阻显著降低输出功率密度相应增加,最大输出功率密度为362.6mW.m-2；不同外接电阻(30Ω、500Ω、2000Ω)下库仑效率依次为83.3%、79.0%、33.6%；通过扫描电镜观察到在外接电阻较高为2000Ω时阳极表面附着的微生物以球菌为主外接电阻较低为30Ω时形态较为复杂主要是丝状菌、球菌和杆菌；外接电阻对SCOD去除率的影响不大；采用最优条件时最大输出功率密度高达387.6mW·m-2。更多还原

【Abstract】 Energy is an important issue in today’s world.Increasing human activities are consuming the natural energy sources leading to depletion of fossil fuel and global warming.In the ever-increasing search for renewable and environmental friendly energy alternatives to fossil fuels,various approaches to derive energy from renewable sources especially from waste have been examined. MFC is a biochemical-catalyzed system,which generates electricity by oxidizing biodegradable organic matter in the presence of either catalytic activity of microorganisms or enzyme.Since the MFC can trap renewable energy by using a variety of substrates including carbohydrate,protein, food wastewaterand swine wastewater, the application of MFC were studied quite extensively.The excess sludge from wastewater treatment plant is rich in polysaccharides and proteins and thus it is regarded as a potential substrate for MFC.Recently, some studies have been focused on using sludge to produce electricity with MFC.However, the reported maximum power density is very low by using the excess sludge as MFC fuel.Due to the low electricity yield from raw sewage, the pretreatment technology and the MFC technology were first combined to improve the power density.After inoculating with the supernatant in the cell operating with surplus sludge,a single-chamber and membrane-less microbial fuel cell was successfully started up by using the supernatant fluid of pretreated sludge as substrate.The effect of microwave power and time on the maximum output power destinies were investigated.Moreover, the features of electricity production and the substrates of the cell during one cycle were investigated, and the difference influences of external resistance on the performance of MFC and the morphologies of the microorganisms forming on the anode surface were also analyzed.The results indicated that the sludge on the pretreatment condition of longer irradiation time and moderate higher microwave power(<900W) could effectively improve the performance of MFC.On the optimal treatment conditions of (300s,720W),the maximum output power destinies could reach up to 306.2mW·m-2.The larger anode area of the cell made the output power density smaller. When the distance between cathode and anode decreased from 5cm to 0.5cm,the output power density first increased and then decreased later, which mainly due to the diffuseness of oxygen from the air-cathode may affect active of the anaerobic bacteria on anode.The maximum output destiny was observed while the distance was 2cm.When using NaCl as an ionic additive, it had a corresponding decrease in internal resistance with the dosage increased resulting an increase in output power density, and the maximum was 362.6mW·m-2.The coulombic efficiency were decreased obviously with the increase of external resistance(30Ω、500Ω、2000Ω) as shown in the following sequence:83.3%、79.0%、33.6%.The SEM observation showed that the surface of the anodic electrode was covered by spherical bacteria at higher external resistance of 2000Ω.However, it was covered by server kinds of bacteria at a lower external resistance of 30Ω, such as filamentous bacteria, spherical bacteria and bacilliform bacteria. The external resistance had minimal impact on the removel efficiency of SCOD.Finally, the output power density of microbial fuel cell with excess sludge as fuel was successfully raised to 387.6 mW·m-2 under optimal experimental conditions.更多还原