【作者】 陈伟伟；

【导师】 刘进荣；

【作者基本信息】 内蒙古工业大学 ， 化学工艺， 2013， 博士

【摘要】 近年来，膜生物反应器（membrane bioreactor，MBR）在污水处理和回用中倍受学者和从业人员的大力推崇和关注。然而，膜污染依然是其中至今尚未得到很好解决的技术难题。本论文以浸没式膜生物反应器（submerged membrane bioreactor，SMBR）中试系统处理废水中的膜污染控制为研究对象，在研究了适宜污泥停留时间（sludgeretention time，SRT）以及最佳曝气方式和曝气量的基础上，采取向SMBR中投加大孔吸附树脂构建吸附-膜生物反应器复合系统，以控制其在生活污水处理中膜污染；选择预混凝-膜生物反应器复合系统用于内蒙古地区实际乳制品工业废水处理，以实现膜污染控制的同时回收水中有机物。此外，对SMBR处理当地城市生活污水时的膜污染清洗方案进行了探索。本文取得的主要研究结果如下：首先，通过研究SRT对污泥浓度（mixed liquor suspended solids，MLSS）、污泥负荷（food-to-microorganism ratio，F/M）、胞外聚合物（extracellular polymericsubstances，EPS）中的多糖（polysaccharide，PS）浓度、化学需氧量（chemical oxygendemand，COD）及氨氮（ammonia nitrogen，NH4+-N）去除率的影响，确定了SMBR处理生活污水的适宜SRT。延长SRT能够增加MLSS和降低F/M，即有利于提高污染物去除率和减少剩余污泥产生；然而，SRT>40d后，过低的F/M会增加进行内源呼吸微生物的数量，使得MBR中MLSS虽高，但微生物活性整体降低，不利于系统维持稳定的生物处理性能。EPS中PS浓度影响活性污泥特性和膜污染发展，实验以该参数作为适宜SRT的选择标准，得出适宜SRT应控制在40d以下。COD和NH4+-N的生物去除效果表明，当SRT介于20-40d时，污染物去除率均达到实验中的最好水平，且受SRT的影响较小。从生物活性、膜污染和出水水质三个方面综合考虑，得出本文实验条件下的适宜SRT为20d≤SRT＜40d。进一步通过改变曝气方式及强度，对跨膜压差（transmembrane pressure，TMP）、临界通量（critical flux，CF）、微生物种类及大小、混合液各组分过滤阻力、COD及NH4+-N去除率进行考察，确定了合适的曝气方式及曝气量。尽管松弛阶段曝气对去除滤饼层具有重要意义，但连续曝气是缓减膜污染最有效的方法，因此优化连续曝气时的曝气量对于平衡能耗和膜污染速率之间的关系更具现实意义。通过测定临界通量的短期实验结果表明，增加连续曝气过程中的曝气量能够提高错流速度，有利于减少污泥颗粒在膜表面的沉积，即可以控制膜污染。尽管如此，长期运行实验结果显示，增加曝气量将改变污泥特性，增加膜污染可能性；同时，降低系统对进水水质的选择性和硝化细菌活性。因此，在后续复合系统的研究中，曝气量的选择应该按照实验需求予以确定。通过对比实验，探索了以大孔吸附树脂（macroporous adsorption resin，MAR）构建的吸附-膜生物反应器（Adsorption-MBR）复合系统在生活污水处理中的膜污染控制。通过对临界通量的表征，验证该复合系统在膜污染控制上的效果；通过考察膜面污泥层发展和混合液特性变化，揭示该复合系统中膜污染控制的途径；最后对使用过的吸附树脂进行了再生实验。结果表明，投加粉末活性炭（powdered activatedcarbon，PAC）和MAR都可以提高MBR的临界通量，而投加MAR的MBR其临界通量改善幅度尤为明显。MAR对膜面的冲刷作用和对混合液可滤性的改善作用是SMBR实现膜污染控制的途径。以MAR构建的Adsorption-MBR复合系统能够更好地降低生物反应器中的污染负荷、减少污泥产量；且由于MAR的可再生性，该复合系统用于膜污染控制的运行成本将优于PAC构建的Adsorption-MBR。运用实验数据进行污染模型拟合以及对污染物进行傅里叶变换红外光谱（fouriertransform infrared spectroscopy，FTIR）分析，确定了同时使用物理化学清洗的污染膜清洗方法；借助扫描电镜（scanning electron microscope，SEM）可视化图像分析和清水比通量（specific flux，SF）测定验证了清洗程序的效果和合理性。实验发现，滤饼层的形成是膜通量衰减的主要原因，发生有机污染的主要污染源是蛋白质、多糖和脂类物质；物理清洗可以有效恢复由污泥絮体沉积造成的污染，化学清洗是去除强烈附着和造成膜孔阻塞的有机、无机污染的重要手段。膜清水比通量实验表明，本文所采用的清洗程序能够将污染膜的通量恢复到新膜的90%以上，不可逆污染已经无法通过清洗过程去除。将预混凝工艺与膜生物反应器耦合构建预混凝-膜生物反应器（Precoagulation-MBR）复合系统用于内蒙古地区实际乳制品工业废水处理，实现膜污染控制的同时回收废水中有机物。通过烧杯实验，考察明矾、硫酸铝、氯化铁和聚合氯化铝四种典型混凝剂对实际乳制品废水浊度的去除率，筛选合适的混凝剂并确定药剂投加量、进水pH和沉降时间参数。通过与乳制品废水处理厂现用工艺进行出水水质（浊度、COD、残留铝）比较和测定跨膜压差变化，探索该复合系统的整体应用性能。通过与预混凝-微滤（Precoagulation-MF）复合系统在临界通量参数上的比较，说明预混凝-膜生物反应器复合系统在膜污染控制方面的优越性。研究结果发现，聚合氯化铝可以作为降低复合系统中有机负荷的最佳混凝剂；进水pH为7.5、加入量为900mg/L时，浊度去除率可达到98.95%，有效沉降时间为30min。预混凝过程对于稳定MBR出水水质和改善膜污染起着重要作用；MBR在去除预混凝出水中的残留浊度和铝方面效果优于现用处理系统，且能够抵抗高有机负荷冲击、保持出水中较高的COD去除率。与Precoagulation-MF复合系统相对比，Precoagulation-MBR复合系统可以成功地实现膜污染控制。更多还原

【Abstract】 In recent years, membrane bioreactor (MBR) for wastewater treatment and reuse isgreatly esteemed and concerned by scholars and professionals. However, membranefouling is still the technical problem which has not yet been well-solved. The object of thispaper was the membrane fouling control of submerged MBR (SMBR) pilot-scale system inwastewater treatment. Based on results of the moderate sludge retention time (SRT) andthe optimal aeration mode and intensity, adsorption-MBR hybrid system by adding MARto MBR was investigated to control membrane fouling in domestic wastewater treatment,and precoagulation-MBR hybrid system was investigated to achieve membrane foulingcontrol and reuse organics in dairy wastewater treatment. Cleaning methods of the fouledmembrane were also investigated in the treatment of local domestic wastewater. The mainresults obtained in this paper are as follows:Firstly, the moderate SRT of SMBR treating domestic wastewater was determined bystudying the impact of SRT on mixed liquor suspended solids (MLSS), food-to-microorganism ratio (F/M), polysaccharide (PS) concentration of extracellular polymericsubstances (EPS), chemical oxygen demand (COD) and ammonia nitrogen (NH4+-N)removal. Extending SRT could increase the MLSS concentration and decrease the F/M andthus could enhance the removal of foulants and reduce the production of excess sludge.However, the low F/M increased the number of microorganisms suffering endogenousrespiration when SRT was higher than40d, and therefore the microbial activity wasdecreased although the MBR with high MLSS and the biological treatment performancecould not be stably maintained. PS concentration of EPS affects the characteristics ofactivated sludge and the development of membrane fouling. This parameter as the selectioncriteria, suggested the moderate SRT should be controlled in less than40d. Results of thebiological removal of COD and NH4+-N showed that pollutant removal reached the bestlevel and almost unaffected by SRT when SRT was in the range of20-40d. Consideringthe three aspects of microbial activity, membrane fouling and effluent quality, theappropriate SRT was20d≤SRT＜40d under the conditions of this experiment.The aeration mode and the aeration intensity were further determined by investigatingtransmembrane pressure (TMP), critical flux (CF), microorganisms’ type and size, resistance of different mixed liquor fractions, COD and NH4+-N removal. Continuousaeration was the most effective strategy for the mitigation of membrane fouling althoughintermittent aeration in the relaxation phase played an important role in the cake layerremoval. Therefore, optimizing aeration intensity in the mode of continuous aeration hadmore practical significance to balance the relationship between energy consumption andmembrane fouling rate. Short-term results by measuring CF showed that increasingaeration rate could enhance the cross-flow velocity, reduce the deposition of suspendedparticles on membrane surface, and so mitigate the membrane fouling. Nevertheless, theresults of long-term running experiment found that increasing the aeration intensitychanged the characteristics of activated sludge, increased the possibility of membranefouling, and decreased the selectivity of the system for influent quality and the nitrifyingbacteria activity. Therefore, the aeration intensity should be determined according to theexperimental needs of hybrid system in subsequent studyMembrane fouling control of adsorption-MBR hybrid system with macroporousadsorption resin (MAR) treating domestic wastewater was researched through comparativeexperiments. Characterization of the critical flux showed the effect of membrane foulingcontrol in this hybrid system. Evolution of the sludge layer on membrane surface andchange of the mixture properties revealed the pathway of membrane fouling control in thishybrid system. Finally, regeneration experiment of the used adsorption resin was carriedout. The results showed that the critical flux could be improved by adding powderedactivated carbon (PAC) and MAR to MBR, and resin showed excellent result particularly.The scouring of MAR on membrane surface and the improved filterability of sludgemixture were the ways to realize fouling control. Adsorption-MBR hybrid system withMAR could reduce the foulant loading in bioreactor, decrease sludge production and wouldbe better than the adsorption-MBR hybrid system with PAC in operating costs due to therenewable performance of resin.Physical cleaning and chemical cleaning are determined and used for the cleaning ofcontaminated membrane by model fitting of experimental data and fourier transforminfrared spectroscopy (FTIR) analysis of foulants. Effect and rationality of the cleaningprocedure was tested by scanning electron microscope (SEM) image analysis and specificflux (SF). The results found that the decline of membrane flux was mainly affected by the formation of cake layer. Proteins, polysaccharides and lipids were the major foulants oforganic fouling. Physical cleaning can effectively remove the fouling caused by thedeposition of sludge floc, and chemical cleaning was the important means to removestrongly attached organic fouling and inorganic fouling caused by pore blocking. Waterflux of membrane showed that the flux could be restored more than90%of the newmembrane flux by the cleaning procedure used in this paper, and irreversible fouling couldnot be removed by this cleaning process.In order to achieve membrane fouling control and reuse the organics in wastewater,precoagulation-MBR hybrid system coupling precoagulation process with MBR was usedfor dairy industrial wastewater treatment of Inner Mongolia. By jar test, turbidity removalefficiency of the actual dairy wastewater using four typical coagulants of alum, aluminumsulfate, ferric chloride and polyaluminium chloride were investigated. Then, coagulant typeand its dosage, influent pH and settling time were determined. The overall applicationperformance of the precoagulation-MBR hybrid system was compared with the presentprocess of dairy wastewater treatment plant in effluent quality (turbidity, COD and residualaluminum) and TMP change. The superiority of the precoagulation-MBR hybrid system inmembrane fouling control was indicated by comparing the CF of the hybrid system withprecoagulation-microfiltration (Precoagulation-MF) hybrid system. The results showedthat polyaluminium chloride could be used as the optimal coagulant to reduce the organicloading in the hybrid system. Turbidity removal efficiency could reach98.95%when theinfluent pH was7.5and the dosage of polyaluminium chloride was900mg/L. Effectivesettling time was30min. Precoagulation process of the hybrid system played a veryimportant role in stabilizing the effluent quality of MBR and improving the membraneperformance. MBR could removal the residual turbidity and aluminum in precoagulationeffluent better than the existing treatment system, and it had the capability to resist shockloading and maintain the high COD removal. Compared with precoagulation-MF hybridsystem, precoagulation-MBR could control membrane fouling successfully.更多还原