【作者】 苏欣颖；

【导师】 田禹；

【作者基本信息】 哈尔滨工业大学 ， 环境工程， 2013， 博士

【摘要】 膜生物反应器（MBR）以膜分离装置取代传统的二沉池，具有高效的固液分离效果，受到国内外学者的普遍关注。但膜污染问题仍然制约着MBR的广泛应用，膜污染机理及膜污染控制方法仍是膜技术领域的研究热点。本文针对目前关于膜污染研究存在的关键问题，探讨了胞外聚合物（EPS）的静态吸附机理，解析了溶解性微生物产物（SMP）及生物大分子（BMM）在膜过滤过程中发生的堵塞机理，考察了膜对SMP和BMM的截留情况，提出了污泥稳定性和聚集性两个识别污泥絮体污染倾向的综合指标，构建了微生物燃料电池与膜生物反应器耦合系统（MFC-MBR），并解析其膜污染减缓机理。利用静态吸附的方法分析了膜污染初期的吸附污染，通过热力学途径确定了膜对EPS的吸附机理。结果表明，Sips等温线最适合描述膜对EPS多糖和蛋白质的吸附；通过热力学计算得到膜吸附过程的rG值在-10至-17kJ mol（-1）之间， rH值在10至30kJ mol^-1之间。说明膜对EPS多糖和蛋白质的吸附是热力学可行且自然吸热的过程，EPS多糖和蛋白质与膜之间的相互作用主要是物理吸附，温度的升高可以提供更多的能量来强化吸附。利用多级Hermia模型研究了膜污染初期的过滤污染，分析了SMP及BMM不同时间段内主导的膜堵塞机理，确定了不同堵塞机理主导时段通量衰减的情况。结果表明，SMP过滤阻力的平均增长速率随时间增加，而BMM过滤阻力的平均增长速率随时间减少。对于SMP，主要顺次发生中间堵塞、标准堵塞及完全堵塞；而对于BMM，顺次发生了中间堵塞及滤饼过滤。不同堵塞机理所对应的时间及通量衰减百分比表明，膜孔堵塞是造成通量下降的主要原因。考察了不同SRT下MBR的膜污染情况及污泥性质，分析了基于修正的粘附-侵蚀模型的污泥絮体剪切稳定性，提出采用污泥絮体稳定性作为评价污泥性质和污染潜力的综合指标。结果表明，具有较差的沉降性、较高的疏水性、较高EPS含量、较多的丝状菌及更多初级粒子的低SRT（15d）污泥絮体容易形成致密无孔的污染层，导致严重的膜污染；低SRT（15d）污泥絮体具有较高的剪切敏感值，即更差的污泥稳定性。分析了MBR混合液及滤饼层污泥性质，解析了基于扩展DLVO理论的混合液及滤饼层污泥聚集性，提出采用污泥聚集性作为一个综合指标反应污泥的膜污染趋势。结果表明，滤饼层污泥具有较高的SMP、胶体及LB-EPS含量、较多小于100μm的絮体、较高DSI、更疏水的表面以及更负的zeta电势。同时，污泥细胞间相互作用能曲线表明，滤饼层污泥具有较高的初级能量最大值和较浅的二级能量最小值，意味着滤饼层污泥具有较差的聚集性。本研究基于污泥改性构建了低污染、低能耗的新型MFC-MBR耦合系统。结果表明，新型MFC-MBR耦合系统系统同时具有废水处理、污泥减量、电能回收及污染抑制的效果。耦合系统MBR的操作周期大约是传统MBR操作周期的两倍。对膜污染减缓机理分析可知，耦合系统MBR中污泥性质得到改善，表现出更好的过滤性和脱水性。与传统MBR相比，耦合系统MBR中LB-EPS的浓度从16.14mg·gSS^-1降低到12.56mg·gSS^-1，且LB-EPS中简单芳香蛋白和色氨酸蛋白类物质分别减少了10%和8%。更多还原

【Abstract】 Membrane bioreactors (MBRs) are efficient wastewater treatment technology,which uses membrane to replace the conventional gravitational settling for thesolid–liquid separation. However, membrane fouling remains a major obstacle forwider application of MBRs. The mechanism and mitigation of membrane foulingare still the challenge of membrane technology. This paper investigated themechanism of static adsorption extracellular polymeric substances (EPS) during ofMBR process and analyzed the filtration mechanisms of soluble microbial products(SMP) and biomacromolecules (BMM). The stability and aggregation of activatedsludge, which could represent the characteristics of the flocs as a whole and identifythe fouling potential, were developed in the paper. A novel combined system ofmicrobial fuel cell (MFC)-MBR based on the modification of sludge characteristicswas also proposed in this study to obtain effective membrane fouling mitigation.The static adsorption experiments were carried out to study the adsorptiveinteraction between EPS and different membranes. The adsorption isotherms wereidentified to understand the adsorption mechanism of EPS onto membranes. Theresults demonstrated that the Sips isotherm model provided the best fit to theexperimental data. Furthermore, some important thermodynamic parameters wereevaluated to understand the nature of adsorption process for different membranes.For all adsorption process of different membranes, the values of rG between-10and-17kJ mol-1, confirming that the adsorption of EPS onto membranes wasthermodynamically feasibility and spontaneous. And the interaction between theEPS and membranes can be considered as a physical adsorption event. The positivevalue of rH further indicated that the adsorption of EPS on membranes was anendothermic in nature and higher temperatures provide more energy to enhance theadsorption.Dead-end filtration tests were used to study the fouling potential of SMP andBMM. Filtration behaviors were analyses and filtration mechanisms weredetermined using multistage Hermia’s model. The contributions of different foulingmechanism to flux reduction were also analyzed. The results showed that theincrease of filtration resistance for SMP was increased with prolonged time whilethe increase of filtration resistance for BMM was decreased with increased time.The multistage Hermia’s model could identify the fouling mechanism dominating ata certain experimental time. For SMP, intermediate blocking occurred first,followed by standard blocking and then complete blocking. In contrast, for filtrationwith BMM, intermediate blocking, and then cake filtration were found to occur successively. Further results indicated that pore blocking was the main reason forflux reduction.By the analysis of membrane fouling, sludge characteristics and stability of thesludge flocs at different SRTs, stability of activated sludge flocs based on amodified adhesion-erosion model (AE-model) was developed to be an integrativereflection of sludge characteristics and fouling potential. The sludge with higherEPS, RH, more filamentous bacteria and more primary particles at lower SRT mightlead to more loose structure and poorer floc stability. It is argued that the highershear sensitivity means more primary particles, a less porous fouling layer and arelative higher specific resistance.By the analysis and compare of sludge characteristics and sludge aggregationof bulk sludge and cake sludge, sludge aggregation based on the extendedDerjaguin-Landau-Verwey-Overbeek (extended DLVO) theory was developed to bean integrative reflection of sludge characteristics and fouling potential. Cake sludgewith had more SMP, colloids and loosely bound EPS (LB-EPS), more small sizeflocs (<100μm), higher distribution spread index (DSI), higher hydrophobicity andmore negative charge. Interaction energy analysis based on the extended DLVOshowed that the cake sludge had a higher primary energy barrier and a lowersecondary energy minimum, implying worse aggregation.A novel combined system of MFC-MBR was proposed in this study. Theeffective wastewater treatment, sludge reduction, energy recovery and membranefouling mitigation could be obtained in the combined system. The operation cycle inthe combined system was found nearly twice as long as that in the conventionalMBR. The characteristics of SMP, EPS and sludge were analyses to detect thereason of fouling mitigation. And the combined system was able to mitigatemembrane fouling by the sludge modification. Further investigation indicated thatthe MFC could effectively reduce the LB-EPS content from16.14mg·gSS-1to12.56mg·gSS-1. Additionally, the intensities of the simple aromatic proteins andtryptophan protein-like substances in LB-EPS decreased by10%and8%respectively, compared with the conventional MBR.更多还原