超滤浓差极化阻力与复合滤饼阻力增长模型的研究

采用外压式PVC中空纤维超滤膜直接过滤地表水,根据曝气周期内的压浊比变化导出相对浓差极化阻力的估算方法,通过研究相对浓差极化阻力与单位膜面积的累积浊度降的关系得出绝对浓差极化阻力;另外还考察了曝气周期内复合滤饼阻力的变化,并建立了复合滤饼阻力增长模型。结果表明,浓差极化阻力与单位膜面积的累积浊度降存在一元三次函数关系;当曝气周期内的累积浊度降90NTU时,复合滤饼阻力与时间具有良好的线性相关性;曝气周期内的复合滤饼阻力增长速率与累积浊度存在指数相关性。反冲洗周期可根据单位膜面积的累积浊度降和累积浊度的变化来确定,以及时、有效地控制膜污染。     

混凝对膜过滤的影响

采用混凝－膜分离技术对黄浦江原水进行试验的结果表明，混凝不仅可提高膜的透水通量，还可有效地降低滤饼层阻力和浓差极化阻力；混凝剂投量为2－4mg/L（以Al计）时，滤饼层阻力最小，投加硫酸铝会增加吸附阻力且造成膜污染。     

不同膜通量下MBR处理餐饮废水的研究

分别在5、10、15、20、25 L/(m2.h)5个膜通量下,考察了平板膜生物反应器(MBR)对餐饮废水的处理效果。结果表明,随着膜通量的提高,出水COD和NH3-N浓度稍有升高,但去除率都基本维持在90%以上;同时,MBR对TN、TP、BOD5、DOC、浊度、含油量、SS、UV254等都有很好的去除效果,出水水质完全符合《城市污水再生利用城市杂用水水质》的要求。对比进、出水中DOC的分子质量分布发现,进水中的大分子有机物被降解为小分子有机物。通过测定不同膜通量下混合液的MLSS、SV30、污泥粒径、粘度等指标,发现MLSS和SV30与粘度之间有很好的线性关系。在运行结束时进行阻力分布测试,发现随着膜通量的增大,内部阻力比例逐渐增大,而滤饼层阻力和浓差极化阻力的比例都逐渐下降。     

超滤法净化污水及在线清洗对膜污染的影响

应用超滤工艺处理污水的试验结果表明,超滤对水中的浊度几乎可以完全去除,对细菌和大肠杆菌的去除率>99%,对水中的有机物、氨氮、总铁和总锰也均有一定的去除;增加周期反冲洗频度大大减缓了通量的下降程度,延长了通量达到平衡的时间;水力清洗可去除部分膜表面污染物,使滤饼层变得松散,在一定程度上减轻了膜污染,而经化学清洗后膜表面的滤饼层基本被去除,有效消除了膜污染。     

MBR/PAC工艺处理微污染源水的膜污染机理及控制

采用膜生物反应器(MBR)与粉末活性炭(PAC)的组合工艺(MBR/PAC)处理微污染源水,考察了膜污染的机理与特征,探讨了控制膜污染的措施。结果表明:MBR/PAC工艺处理微污染源水时的膜污染发展速度较快;膜污染以滤饼层沉积和有机物膜孔污染为主,同时伴随着少量的无机物污染;膜固有阻力、滤饼层阻力、凝胶层与膜孔堵塞阻力分别占膜总阻力的15%、43%和42%。只用清水冲洗膜表面可使膜过滤性能恢复35.7%~38.5%;而用0.3%~0.5%的NaClO浸泡足够时间后,膜过滤性能基本得到恢复;在碱洗后增加稀酸清洗,可进一步提高清洗效果。     

投加颗粒活性炭对膜生物反应器过滤特性的影响

膜污染是制约膜技术应用的重要因素。向膜生物反应器(MBR)中投加颗粒活性炭(GAC),通过分析MBR系统中膜通量、过滤阻力等的变化,考察投加GAC对MBR系统过滤特性的影响。结果表明,运行30d后,未投加和投加GAC的MBR系统的膜通量分别降至初始的31.3%和91.7%;未投加GAC系统的总过滤阻力和极化阻力分别为投加GAC系统的5.8和19.4倍,其污泥的多糖和蛋白质含量为投加GAC系统的近2倍,而其胶体物质和溶解性物质浓度分别为投加GAC系统的3.2和2.2倍。由此表明,投加GAC可大大减缓膜污染,延长膜的过滤周期。     

自生动态生物膜形成过程中的结构变化特征

利用动态膜生物反应器处理模拟生活污水,对自生动态膜形成过程中的结构特征及阻力特性进行了研究.结果表明,反应器启动10 min后出水浊度即小于5 NTU,后期的出水浊度始终保持在2 NTU以下.自生动态膜的形成可分为3个阶段:①镶嵌快滤阶段--污泥絮体镶嵌于无纺布纤维丝之间,平均当量孔径为数十微米,膜阻力为(0.395～0.88)×10-m-1,出水中仍有较多颗粒;②网状覆盖阶段--滤饼层表面呈网状分布,膜孔径在2.78～6.49μm之间,孔隙率高达36.1%～40.2%,阻力为(2.74～3.77)×109m-1,出水水质较好,微生物增殖和小颗粒堵塞为孔径缩小的主要原因;③膜孔堵塞阶段--平均当量孔径缩小至0.97μm,孔隙率降为21.7%,阻力突增至2.26×1010m-1,微生物增殖和小颗粒堵塞仍是导致其孔径缩小的主要原因.     

膜生物法处理城市垃圾渗滤液

采用膜生物法对垃圾渗滤液经UASB预处理的出水进行了降解试验。结果表明，MBR对COD的去除率为70％～85％，对氨氮的去除率为90％～99．8％，对总氮的去除率为50％～67％；膜通量与运行时间呈幂函数关系；滤饼层阻力在总阻力中所占的比例最大；无机型膜污染阻力远大于有机型；酸洗对膜的清洗效果要好于碱洗。     

浸没式厌氧双轴旋转膜生物反应器的开发

针对浸没式厌氧膜生物反应器的膜污染问题,开发了一套内置双轴旋转膜组件的浸没式厌氧膜生物反应器.系统的容积为120 L,内装填平板超滤膜.膜组件采用双轴同向旋转,由膜旋转形成的湍流可减缓膜表面的浓差极化及凝胶层的形成,从而有效控制膜污染.与传统厌氧膜生物反应器相比,该工艺具有结构紧凑、除污效果好、能耗低和可大幅度减轻膜污染等优点.     

钙离子浓度对超滤天然有机物膜污染的影响

膜污染一直是阻碍超滤工艺应用的瓶颈性难题。通过超滤试验研究了天然水中钙离子浓度对超滤膜污染的影响。结果表明,钙离子浓度增加促进了超滤膜跨膜压差的增长,同时加重了超滤膜的浓差极化阻力、水力可逆阻力和水力不可逆阻力。此外,钙离子浓度增加会加强超滤过程的浓缩效应,并促进膜表面滤饼层的形成。钙离子浓度提高提升了有机物Zeta电位,增加胶体粒径尺寸,进而提高超滤膜对有机物的截留率。同时,钙离子浓度的增加提高了反冲洗和化学清洗洗脱液中腐殖酸类和蛋白质类有机物的浓度,说明钙离子能够强化有机物与膜之间的相互作用,导致超滤膜污染加剧。     

Enhancement of filterability in MBR achieved by improvement of supernatant and floc characteristics via filter aids addition

Reduction of membrane fouling in membrane bioreactors (MBR) by addition of three typical filter aids (aluminum sulfate (Al(2)(SO(4))(3)), polymeric ferric sulfate (PFS) and Chitosan) was investigated. The effects of filter aids on membrane pore blocking, gel layer and cake layer resistance were analyzed respectively. Significant improvement of the sustainable filtration was demonstrated in the filter aids added MBRs. The membrane fouling rate of the MBRs operated under 20L/m(2)h flux was in the order of Control MBR (no filter aid added)>Al(2)(SO(4))(3) added MBR>Chitosan added MBR>PFS added MBR. Membrane inner fouling due to pore blocking was analyzed by means of Fourier-transform infrared microscope (FTIR). Compared to the control MBR, significantly low protein and carbohydrate concentrations were measured in the membranes of the filter aids added MBRs, indicating that filter aids could effectively alleviate membrane pore blocking. Gel Permeation Chromatography (GPC) analysis suggested that both the concentration and molecular weight distribution of the macromolecules in supernatant play an important role in gel layer formation and loss of membrane porosity. The reduction of fouling rate in the filter aids added MBRs could be attributed to lower concentration and reduction in molecular weight of macromolecules in supernatant. The specific cake resistance (alpha(c)), mean floc size (d(p)) and fractal dimension of the flocs (df) in the filter aids added MBRs were also investigated. It was demonstrated that alpha(c) decreased with the increase of d(p) and with the decrease of df, which is in consistent with the model prediction.     

膜技术回收处理水厂生产废水试验研究

采用机械搅拌澄清池→保安过滤器→超滤膜过滤工艺对北京某水厂生产废水(沉淀池排泥水的上清液与煤砂滤池、活性炭滤池的反冲洗水的混合液)进行了回收利用的中试研究,并对比了不同种类混凝剂对膜过滤性能及除浊效果的影响,确定了聚铝的最佳投量为4 mg/L.中试结果表明,采用该工艺处理生产废水,产水各项指标均优于或达到<生活饮用水卫生标准>(GB5749-2006),水的回收率达到了95%.此外还对膜面上的污染物进行了能谱分析,确定了其清洗方法(化学清洗剂为盐酸和次氯酸钠,清洗周期为2个月).     

SMSBR处理焦化废水的膜污染机理研究

在采用SMSBR处理焦化废水的过程中，通过对污泥进行终端过滤来反映膜污染机理，着重考察了过滤过程中的阻力分布，并通过标准堵塞过滤定律和沉积过滤定律来拟合膜过滤过程，从而确定了膜污染的控制因素。污泥的阻力分布试验表明，沉积阻力占总阻力的90％以上，并随压力的升高而增大，而内部污染阻力所占比例最小；污泥的终端过滤过程严格符合沉积过滤定律，即使在过滤初期也不受堵塞过滤的控制，这与阻力分布的结果相对应；污泥在严格符合沉积过滤定律，即使在过滤初期也不受堵塞过滤的控制，这与阻力布的结果相对应；污泥在终端过滤过程中膜的相对通量随过滤时间呈指数衰减趋势，并在几分钟内就达到相对稳定值，且低压对应较高的相对通量，但通量衰减指数和压力之间没有相关性；污泥的压密指数为0．7015。     

膜污染中污泥层阻力模型及影响因素研究

膜污染是影响膜生物反应器大规模化应用的重要因素之一．优化了污泥层阻力的数学模型,并对污泥层阻力的影响因素进行了试验研究,模型确定了污泥浓度和膜面流速是引起污泥层阻力的主要因素．短期试验的结果较好地验证了污泥层阻力的数学模型,存在最佳的膜通量、污泥浓度和膜面流速．     

SMSBR中PAC对膜污染的防治作用

在SMSBR处理焦化废水的过程中，通过向反应器中投加粉末活性炭（PAC）进而形成生物活性炭（BAC）来实现对膜污染的防治，并通过对BAC污泥的终端过滤来反映其对膜污染的改善作用。试验结果表明，BAC污泥在终端过滤过程中，其相对通量的变化规律与普通活性污泥相同，但投加PAC后的膜通量明显提高。另外，在相同压力下普通活性污泥的通量衰减指数要远高于BAC污泥，而在相同PAC浓度下BAC污泥的通量衰减指数随压力的变化与普通活性污泥一样，未表现出一定的规律性。BAC污泥的阻力分布表明，沉积层阻力仍占有绝对优势（大于80％），并随压力的升高而增大，但与普通活性污泥相比该比例有明显下降，膜的固有阻力所占比例明显提高，体现了PAC对膜污染的防治作用。     

Characteristics of microfiltration membranes in a membrane coupled sequencing batch reactor system

Factors affecting filtration performance were investigated in a sequencing batch reactor (SBR) coupled with a submerged microfiltration module. Special bioreactors for aerobic and anoxic phases were specifically designed in order to differentiate the effect of dissolved oxygen (DO) from that of mixing intensity, on membrane filterability. When the filterability of a submerged microfilter was examined at each SBR phase, DO concentration, as well as mixing intensity proved to have a major influence on the membrane performance regardless of the SBR phase. A higher DO concentration resulted in a slower rise in TMP, corresponding to less membrane fouling, which was investigated in depth through a series of analyses including resistance measurements and compressibility of the cake layer as well as particle sizes as a functions of DO for both aerobic and anoxic phases in SBR.     

两种膜的前端处理技术减缓膜污染的试验研究

通过超滤膜过滤粉末活性炭预处理长江水和混凝沉淀预处理太湖水的上清液试验,比较各工艺中有机物极性含量的变化,结合膜的扫描电镜照片,探讨粉末活性炭和混凝沉淀预处理技术对膜污染的减缓作用。结果表明,疏水性有机物是造成膜污染的主要因素,亲水性有机物对膜污染的影响较小。超滤膜分别过滤经20 mg/L投量的粉末活性炭预处理的长江水样和25 mg/L投量的聚合氯化铝预处理的太湖水样时,相比直接过滤2种原水,超滤膜反洗后膜通量可有效恢复。粉末活性炭和混凝沉淀预处理后,膜表面形成的滤饼层较松散,易被周期性反洗排出膜组件,滤饼层可阻止疏水性有机物直接沉积在膜表面,减缓超滤膜污染,同时也可提高超滤膜出水的化学安全性。     

投加粉末活性炭对膜阻力的影响研究

小试和中试研究结果表明：粉末活性炭在膜生物反应器系统中具有改善泥水泥合液的性质和膜表面泥饼层结构的作用,从而减小了膜的过滤阻力,减缓了膜通量的下降。向膜生物反应器内投加粉末活性炭是提高和维持膜通量的有效途径,并且可以降低运行费用。     

TiO2 and polyvinyl alcohol (PVA) coated polyester filter in bioreactor for wastewater treatment

Prepared by coating TiO₂/polyvinyl alcohol (PVA) on a low cost polyester filter cloth (22 μm), a composite membrane (10 μm pore size) was successfully used in an anoxic/oxic membrane bioreactor (A/O-MBR) for treating a simulate wastewater in removing nitrate/ammonium for water reuse in a polyester fiber production plant. Its permeate flux and the anti-fouling properties against extracellular polymeric substances (EPS) were studied. Comparing with a commercial (0.1 μm) PVDF (polyvinylidene fluoride) membrane, similar effluent qualities were achieved, meeting the basic COD requirements for reuse. Anti-EPS accumulation, the TiO₂/PVA Polyester composite membrane had higher sustained permeability and required less frequent cleaning. Its filtration time was 4 times longer when operated at a higher flux than the PVDF membrane. The nano-TiO₂ enhances the interaction between PVA and polyester, forms a more hydrophilic surface, drastically reduces the contact angle with water and reduces EPS fouling. The slow (trans-membrane pressure) TMP rise, loose cake layer, the low filtration resistances, and the EPS, SEM analysis confirmed the advantage of the composite membrane. Potential in lowering the membrane cost, the operation and maintenance cost, and in enhancing MBR waste water treatment efficiency is expected by the use of this new composite membrane.     

聚四氟乙烯覆膜滤料的发展及应用特点

本文主要介绍了聚四氟乙烯覆膜滤料的发展过程,分析了聚四氟乙烯覆膜滤料表面过滤的除尘机理。通过与传统滤料相比,说明了覆膜滤料的优越性,并指出覆膜滤料具有除尘效率高、排放浓度低、运行阻力小、过滤速度高、使用寿命长和运行费用省等特点。最后介绍了覆膜滤料在水泥工业中的应用。