膜生物反应器次临界通量运行的膜污染特性研究

膜生物反应器（MBR）是将膜分离与生物反应相结合的污水处理新工艺,近年来已引起广泛的关注,但不可避免的膜污染限制其更广泛的应用。临界通量在膜污染控制中是个非常重要的概念。本试验研究平板膜生物反应器在次临界通量运行下的膜污染状况,并结合膜污染模型进一步表征膜表面的污染特性。试验结果表明。该平板膜生物反应器在次临界通量运行的情况下,膜污染可分为膜污染缓慢发展阶段（第Ⅰ阶段）和膜污染迅速发展阶段（第Ⅱ阶段）,可分别用膜孔堵塞模型和泥饼阻力模型表征膜阻力与时间的变化关系。同时,对运行后的膜阻力分布进行分析,表明泥饼阻力和孔道吸附堵塞阻力是膜污染的主要组成部分,分别占到总阻力的73％和24％,而膜本身阻力仅占3％。     

附着性胞外多聚物对HMBR膜污染控制性能的影响

采用复合式膜生物反应器（HMBR）处理城市生活污水,对附着性胞外多聚物影响HMBR膜污染控制性能的作用机理进行了研究。实验结果表明,HMBR中附着性胞外多聚物、松散附着性胞外多聚物和紧密附着性胞外多聚物的浓度比常规膜生物反应器分别降低了10．0％、43．6％和2．1％。附着性胞外多聚物与膜表面滤饼层污泥比阻的关系较为密切,随着其浓度逐渐降低,滤饼层污泥比阻相应减小。与紧密附着性胞外多聚物相比,松散附着性胞外多聚物对滤饼层污泥比阻的影响程度更深。因此,随着反应器中附着性胞外多聚物特别是松散附着性胞外多聚物浓度的降低,HMBR的膜污染控制性能增强,反应器中膜表面的滤饼层阻力比常规膜生物反应器降低了56．9％。     

活性污泥中EPS的2种测定方法及其对膜通量的影响

以动态膜生物反应器（DMBR）中养殖废水为研究体系,探讨活性污泥中细菌胞外多聚物（EPS）的2种测定方法,蛋白质多糖加合法（EPS PSP）、TOC法（EPS TOC）及其与膜通量之间的相关性研究。结果表明,EPS PSP与EPS TOC的相关性较好,相关系数R2为0.9183;EPS PSP约为EPS TOC的80%左右。EPS TOC和EPS PSP与膜通量的相关系数较低,仅为0.490和0.412,说明造成膜污染的因素很多,相比之下,EPS TOC比EPS PSP更适合说明膜生物反应器中的污泥状态,更能体现膜污染的状况。     

粉末活性炭对膜过滤性能的影响

向一体式膜生物反应器中投加粉末活性炭（PAC），可以显著提高膜的过滤性能，有效缓解膜的污染。研究结果表明：投加PAC的吸附作用减少了由于胞外聚合物（EPS）而引起的膜污染；膜表面PAC颗粒的存在减小了浓差极化层的厚度和水力边界层的厚度，提高了过滤物质的传递速率；膜表面形成的PAC层还可过滤微生物和胶体颗粒，减少了它们到达膜表面的数量。     

在线超声作用下流化床膜生物反应器的膜污染机制

在流化床膜生物反应器中引用在线超声技术来控制膜污染,考察了在线超声对污泥混合液特性的影响,探讨了在线超声作用下的膜污染机制。结果表明：在线超声流化床膜生物反应器的跨膜压差（TMP）增长速度明显慢于普通流化床膜生物反应器,可延长膜清洗周期约51％。在线超声作用下,污泥平均粒径降低约70μm,污泥胞外聚合物（EPS）含量增加（14±5）mg／g,混合液溶解性微生物产物（SMP）有所降低;同时,在线超声使得污泥浓度和混合液粘度降低,从而改善了混合液的过滤性,有助于膜污染的控制。分析表明,在线超声能够减少膜表面不可逆污染的发生,膜的主要污染机制为泥饼层污染。     

复合式膜生物反应器膜污染机理研究

通过在膜生物反应器中添加填料,在保持良好出水水质的前提下可有效降低悬浮污泥浓度,从而减轻膜表面的污泥沉积,减轻膜污染。在处理生活污水的试验中,膜表面泥饼层阻力在总阻力中的比例下降到10％,而膜孔吸附阻力中由溶解性有机物所造成的阻力占到83．3％,这表明由于膜表面的污泥沉积降低,膜组件对溶解性有机物的吸附增加,因而应当选择合适的污泥浓度以得到最佳的综合效果。     

好氧硝化颗粒污泥膜生物反应器性能和膜污染研究

实验研究了好氧硝化颗粒污泥膜生物反应器AGMBR的处理性能,并将其与活性污泥膜生物反应器ASMBR进行对比,考察了颗粒污泥在减缓膜污染中所起的作用.好氧硝化颗粒污泥膜生物反应器AGMBR连续稳定运行102 d,系统具有良好的去除有机物和同时硝化反硝化能力,在进水COD和NH+4-N浓度分别为500和200 mg/L时,COD、NH+4-N和TN的去除率分别稳定在86%、94%和45%以上.颗粒污泥有效减缓了膜污染,延长了膜清洗的周期,AGMBR中的膜污染以膜孔堵塞为主,占总阻力的64.81%;滤饼层的阻力为2.1×1012m-1,远小于ASMBR中的16.07×10"m-1;膜清洗周期是相同条件下ASMBR的2.43倍以上;而且AGMBR内不断有新颗粒生成,维持了AGMBR系统性能和运行的稳定.     

长泥龄膜生物反应器中活性污泥的膜污染研究

长泥龄膜生物反应器(MBR)内污泥性质与普通活性污泥有显著差异。利用一污泥停留时间长达300 d的膜生物反应器研究了污泥浓度、过膜压力和错流速率对长泥龄活性污泥膜污染特性的影响。研究结果表明,使用0.2 μm微滤膜错流过滤时,浓差极化阻力R_cp和滤饼层阻力R_c是膜污染的主要影响因素,各占总的膜阻力R_t的23%～63%和31%～73%。与之相比,膜内部阻力R_if和膜固有的阻力R_m只占总的膜阻力Rt的0.7%～2.4%和1.2%～6.4%,几乎可以忽略不计。随着污泥浓度,过膜压力的增大和错流速率的减小,膜污染逐渐加剧。因此,降低过膜压力,提高流速,可以有效减缓膜污染,减少清洗频率,延长膜组件的使用寿命,从而节约操作成本,推广应用。     

生物制剂对MBR中无纺布膜组件过滤性能的影响

研究了生物制剂对浸渍式膜生物反应器(submerged membrane bioreactor,SMBR)中聚丙烯无纺布(non-wov-en fabric,NWF)膜组件过滤性能的影响。结果表明,能减少膜组件表面附着污泥胞外聚合物(extra-cellular polymeric sub-stances,EPS)的含量及污泥的沉积,减缓膜通量的衰减速率和膜污染,无纺布膜组件的过滤性能得到明显改善,表现出一定的耐污染性。生物制剂能改善污泥的沉降性能,有效防止污泥膨胀;对MBR的COD去除率基本没有影响,但略微增大了处理水的浊度。     

中水回用中平板膜的污染机理分析

采用间歇式生物反应器，对模拟小区生活污水的人工配水进行了生物处理；然后，在操作压力为0．1MPa，搅拌速度为300r／min条件下，选用膜生物反应器中常用的聚醚砜（PES，切割分子量分别为2万、1万和5千）、聚丙烯腈（PAN，切割分子量为20万）、聚偏氟乙烯（PVDF，切割分子量为20万）超滤平板膜和聚醚砜（PES，孔径为0．1μm）、聚丙烯腈（PAN，孔径为0．1μm）、聚偏氟乙烯（PVDF，孔径为0．1μm）微滤平板膜在实验室用死端超滤器上分别对活性污泥悬浮液进行了过滤并探讨了和间歇式生物反应器组合在一起用于中水回用的效果，结果表明：每种组合处理后的出水水质为COD〈50mg／L，NH3-N〈10mg／L，SS为0mg／L，浊度为0NTU，都达到了中水回用的水质标准（CJ25．1．89），其中生物反应器分别与PES超滤膜（5千、1万、2万）和PAN（20万、0．1μm）膜组合时，对COD的去除率较高，但所有组合对NH3-N、TOC去除率及膜的渗透通量都相差不大。此外，根据恒压堵塞过滤定律对膜的污染机理进行的研究证实：对于微滤膜和PAN（20万）超滤膜而言，由滤饼过滤过渡到完全（标准）堵塞，再到滤饼过滤；但对于PVDF（20万）和PES（2万）超滤膜，则由标准堵塞过渡到完全堵塞，再到滤饼过滤；PES（5千、1万）超滤膜的污染机理相对简单，整个过程以滤饼过滤为主。     

改性PES膜在MBR中膜阻力分析及膜污染机理研究

以聚醚砜(PES)、醋酸纤维素(CA)和纳米二氧化钛(TiO2)为膜材料,采用L-S相转化法制备共混改性PES膜。在24℃、0.2 MPa的操作条件下,制得的PES膜纯水通量为300 L/(m2.h)左右,CA改性PES膜为660 L/(m2.h)左右,TiO2改性PES膜为840 L/(m2.h)左右。通过膜生物反应器中膜阻力的测定,表明膜污染主要由浓差极化层及凝胶层引起的;通过活性污泥对膜污染机理的研究,判断出污泥的过滤过程基本符合沉积过滤定律。在MBR中运行时,改性PES膜稳定通量高于未改性膜,总阻力低于未改性膜;TiO2改性膜稳定通量高于CA改性膜,总阻力低于CA改性膜;通过扫描电镜分析,改性PES膜沉积层的厚度均比未改性膜薄,TiO2改性膜沉积层厚度小于CA改性膜,表明改性膜的抗污染性能提高了,TiO改性膜抗污染性能更优。     

Investigation of the role of biopolymer clusters in MBR membrane fouling using flash freezing and environmental scanning electron microscopy

The technique that employs flash freezing and environmental scanning electron microscopy (ESEM) was utilised for detailed investigation of the fouling materials in a membrane bioreactor (MBR). The method involves the flash freezing of a wet sample in liquid nitrogen for 10 s to preserve its structure for direct ESEM observation with a high image resolution. ESEM images show that the sludge cake formed by simple filtration of the MBR bulk sludge has a highly porous, sponge-like structure with a fairly low resistance. However, the fouling layer attached to the membrane surface contains a thin gel layer under the main body of the sponge-like sludge cake, which is similar to that formed by filtration of a dispersion of biopolymer clusters (BPCs). It is apparent that BPCs tend to accumulate on the membrane surface, and the gel layer is largely responsible for the high filtration resistance of the cake layer on the fouled membranes.     

Aerobic and anaerobic membrane bioreactors for municipal wastewater treatment.

An aerobic bioreactor and an anaerobic bioreactor, each coupled with a microfiltration membrane filter (MBR), were operated at different hydraulic retention times (HRTs) with primary effluent from the City of Elmhurst, Illinois, municipal-wastewater-treatment plant. The soluble chemical oxygen demand (COD) removal performance of the anaerobic MBR system was similar to that of the aerobic MBR under the same operational conditions, without the added cost of aeration. The results indicated that the solids deposition rate on the membrane surface was lower in the case of anaerobic MBR compared to the aerobic MBR, indicating possible lower loss in water-flux rates. This research found that an anaerobic MBR is a feasible and economical option for municipal-wastewater-treatment plants seeking COD removal by a biological process followed by a separate nitrification and denitrification system.     

Use of chemical coagulants to control fouling potential for wastewater membrane bioreactor processes.

Chemical coagulation with ferric chloride, alum, and an organic polymer were used to control the fouling potential of mixed liquors for submerged membrane bioreactor (MBR) processes in treating municipal wastewater. Their filterability was evaluated using a submerged hollow fiber ultrafiltration apparatus operated in constant permeate flux mode. The collected transmembrane pressures over filtration time were used to calculate the membrane fouling rates. The results showed that coagulation pretreatment can reduce fouling rates when MBRs were operated above the critical flux. Even though coagulation with the organic polymer formed larger mixed liquor suspended solids particles and had shorter time-to-filtration than those with ferric chloride and alum, the filterability for membrane filtration were similar, indicating that the membrane fouling in MBR systems was mainly controlled by the concentration of smaller colloidal particles.     

Effect of membrane type and material on performance of a submerged membrane bioreactor

This study evaluated the impact of membrane type and material on filtration performance in a submerged membrane bioreactor (MBR) for municipal wastewater treatment. Three types of microfiltration membranes with similar pore size of 0.1 microm but different materials and types, phase-inversed polytetrafluoroethylene (PTFE), track-etched polycarbonate (PCTE) and track-etched polyester (PETE), were used. Changes in permeability with time for the PCTE and PTFE membranes appeared similarly, whereas the PETE membrane exhibited the most rapid flux decline. Lower TOC in the permeate compared to the supernatant was probably due to a combination of biodegradation by the biofilm (cake layer) developed on the membrane surface and further filtration by cake layer and narrowed pores. The faster permeability decline and higher TOC removal rate of the PETE membrane were attributed to an initial permeate flux higher than an average design flux, which led to a faster rate of fouling and thicker cake layer. Therefore, an MBR should not be operated at a flux higher than the average design flux for a specific type of membrane. A gradual increment of biomass concentration did not significantly affect membrane permeability of each membrane investigated. Dissolved organic carbon fractionation results showed that the composition of each fraction between the supernatant and permeates did not change significantly with time, suggesting that membrane hydrophobicity was not a dominant factor affecting MBR fouling in this study. The organic foulants desorbed from the PCTE membrane contained approximately 60% of hydrophobic fraction, which was probably attributable to the extracellular polymeric substances proteins released from the biomass attached to the membrane. While the total filtration resistance of the PTFE membrane was influenced by a higher surface roughness, those of the PETE and PCTE membranes, which had a similar and lower roughness, were affected by the initial operating flux.     

好氧颗粒污泥动态膜生物反应器工艺参数及运行性能

以一体式尼龙筛网动态膜生物反应器(DMBR)为研究体系,与好氧颗粒污泥相结合,形成新的好氧颗粒污泥动态膜生物反应器(AGDMBR),探讨了在新工艺条件下对COD、氨氮的去除,以及出水浊度的变化,与活性污泥动态膜生物反应器(DMBR)做比较,研究了进水流量、曝气量等工艺运行参数与膜污染之间的关系,并对系统中污泥的EPS进行分析。结论表明,AGDMBR系统对COD和NH4+-N的平均去除率分别为91%和95%,出水浊度为6 NTU,处理效果均优于DMBR系统;AGDMBR系统在运行过程中膜污染速度随进水流量的增大而加快;曝气量为125～150 L/h时,膜通量持续时间最长;AGDMBR系统比DMBR系统在膜污染的延缓上具有明显的优势。     

一体式膜-生物反应器中膜污染过程的动态分析

膜污染过程的动态研究对于有效地控制膜污染意义重大。结合膜过滤压差的上升和污染膜表面微观形态的变化 ,对不同污泥浓度和膜通量条件下 ,一体式膜 生物反应器中膜污染过程进行了动态分析。结果表明 ,膜污染初期主要是水中溶解性物质在膜表面附着 ,随后污泥在膜表面沉积。溶解性有机物在膜面的附着 ,对膜过滤压差即膜过滤阻力的变化影响不大 ,而活性污泥在膜表面的大量沉积将导致膜过滤压差迅速上升。污泥浓度愈高 ,膜通量愈大时 ,活性污泥颗粒愈易在膜面沉积。通过停止进出水维持空曝气、降低反应器内污泥浓度或延长膜的停抽时间可以使沉积在膜表面的悬浮污泥脱离膜表面 ,从而使膜过滤能力得到很好的恢复。采用经典的膜污染模型对各运行阶段膜污染模式进行了分析 ,模型拟合结果与电镜观察结果基本吻合。