钙离子存在下胞外聚合物及其模拟溶液在膜污染中的差异

针对膜生物反应器膜污染的问题,为探究模拟物质替代实际物质的可行性,以胞外聚合物(EPS)及其模拟溶液(BSA+SA)为研究对象,对比了钙离子(Ca~(2+))存在下胞外聚合物及其模拟溶液在膜污染中的差异,考察了EPS-Ca~(2+)和BSA+SA-Ca~(2+)在粒径分布、官能团、流变特性和膜污染行为等方面的差异。结果表明:Ca~(2+)使得溶液粒径变大,且EPS-Ca~(2+)的平均粒径大于BSA+SA-Ca~(2+)的平均粒径;不同官能团与Ca~(2+)发生作用导致红外光谱中特征峰发生偏移;BSA+SA-Ca~(2+)水胶体系结构更稳定,随着应变的增大,胶体结构被破坏的程度较轻;在微滤过程中,相同操作条件下,BSA+SA-Ca~(2+)的膜污染现象更为严重。进一步采用Hermia过滤模型拟合发现,EPSCa~(2+)和BSA+SA-Ca~(2+)分别对中间堵塞模型和滤饼层过滤模型的拟合程度最高。上述结果可为膜污染过程中胞外聚合物及其膜污染机理研究提供参考。     

中空纤维微滤膜污染及阻力分析

选用0.1μm的PVDF中空纤维内压式微滤膜组件,在死端微滤工况下,研究了酵母(平均粒径5.3 μm)和高岭土(平均粒径0.7μm)体系在浓度和压力变化时的污染机理及过滤阻力、膜渗透通量的变化规律性.通过恒压堵塞定律积分式的具体形式与实验数据的拟合及根据堵塞过滤定律计算的结果都表明:死端微滤时,酵母体系和高岭土体系均符合滤饼过滤机理.     

中空纤维微滤膜污染及阻力分析

选用0．1μm的PVDF中空纤维内压式微滤膜组件，在死端微滤工况下，研究了酵母（平均粒径5．3μm）和高岭土（平均粒径0．7μm）体系在浓度和压力变化时的污染机理及过滤阻力、膜渗透通量的变化规律性。通过恒压堵塞定律积分式的具体形式与实验数据的拟合及根据堵塞过滤定律计算的结果都表明：死端微滤时，酵母体系和高岭土体系均符合滤饼过滤机理。     

超滤膜深度处理染整废水的膜污染机理

实验采用不同规格和材料的超滤膜进行染整二级尾水分离实验,对超滤膜污染机理及影响因素进行了分析。实验采用红外光谱分析了聚醚(PES)膜、聚砜(PSF)膜和聚醚酰亚胺(PEI)膜3种超滤膜材料,对比了污染前后膜面的接触角以及不同切割分子量对膜通量及出水水质的影响,并利用线性化的Herman堵塞模型拟合了不同分子量超滤膜的堵塞模型,初步探讨了超滤膜的污染机理。实验结果表明,膜材料表面亲水性基团的多少与初始膜通量大小成正比,出水COD值随超滤膜切割分子量减小而减小。切割分子量同为2 000 Da的3种超滤膜中,PES膜的处理效果最佳,出水COD平均值为47.81 mg/L;PEI膜通量最高,平衡通量可达50 L/(m2.h);切割分子量为1 000、10 000的超滤膜堵塞机理符合滤饼过滤模型,100 000的超滤膜堵塞机理更接近于完全堵塞模型;1 000的聚醚砜材质膜(PES)更适合此类废水的深度处理。     

陶瓷膜污染过程分析与膜清洗方法优化

采用膜孔径为50 nm的陶瓷膜错流过滤方式,对碱性高浓度有机洗涤废水进行9个周期的膜通量衰减及反向脉冲清洗再生实验研究.通过设计膜污染阻力构成实验,测算膜污染总阻力及其构成比例.实验结果表明,膜固有阻力比例较低,浓差极化污染较弱,Rt和Rc+Rirt污染阻力稳定性较高,膜堵塞形式兼有孔内堵塞和滤饼过滤;选择质量分数0.1％的稀盐酸和0.2％的草酸溶液膜清洗效果均较好,清洗时间为3 min,脉冲时间和频率为3 s/5 s.     

TiO_2光催化对微滤去除腐殖酸的膜污染控制研究

着重研究了不同紫外灯光源和照射时间条件下,TiO_2光催化(PCO)对微滤去除腐殖酸过程中的膜污染控制,并探讨了膜污染的控制机理。研究结果表明,TiO_2光催化能有效提高微滤对腐殖酸的去除,同时降低膜通量的下降,起到有效控制膜污染的作用。进一步的实验分析表明,TiO_2光催化控制膜污染的主要机理在于将腐殖酸降解为易于被TiO_2吸附的小分子量物质,吸附腐殖酸降解产物后的TiO_2聚合颗粒粒径增大,易于在膜表面形成更为松散的沉积层,并使膜污染从以膜孔堵塞和沉积层污染为主转化为以沉积层污染为主的可逆性污染。     

TiO2光催化对微滤去除腐殖酸的膜污染控制研究

着重研究了不同紫外灯光源和照射时间条件下,TiO2光催化（PCO）对微滤去除腐殖酸过程中的膜污染控制,并探讨了膜污染的控制机理。研究结果表明,TiO2光催化能有效提高微滤对腐殖酸的去除,同时降低膜通量的下降,起到有效控制膜污染的作用。进一步的实验分析表明,TiO2光催化控制膜污染的主要机理在于将腐殖酸降解为易于被TiO2吸附的小分子量物质,吸附腐殖酸降解产物后的TiO2聚合颗粒粒径增大,易于在膜表面形成更为松散的沉积层,并使膜污染从以膜孔堵塞和沉积层污染为主转化为以沉积层污染为主的可逆性污染。     

混凝剂品种对混凝-超滤联合工艺膜污染的影响

本实验以工业化学合成聚合硫酸铁混凝剂和自制生物聚合硫酸铁为例,考察了铁系混凝剂品种对地表水浊度、TOC和UV254的去除效果,混凝剂品种对混凝-超滤联合工艺处理地表水过程中超滤膜污染的影响。混凝实验结果表明,在10 mg/L(以Fe3+计)最佳投加量下,两类混凝剂对浊度、TOC和UV254的去除率基本相同。超滤膜污染实验结果表明,生物聚合铁预处理水样通量衰减速度略大于化学聚合铁预处理水样;膜污染阻力分析结果显示,随着循环次数的增加,工业化学合成聚合铁预处理水样造成的不可逆污染阻力逐渐增加,而生物聚合铁预处理水样造成的不可逆污染阻力却略有下降;膜污染机理分析表明,2组过滤过程的膜污染类型基本相似,由最初的膜孔堵塞过渡到最终的滤饼层污染。SEM分析表明,生物聚合铁预处理水样的膜污染较为严重。     

pH对钢铁废水再生过程中CMF系统的影响

通过中试实验研究了钢铁废水再生过程中pH变化对微滤系统性能的影响。结果表明,进水pH的升高增加了微滤膜对UV254、Ca2+和总铁的去除,同时引起了有机物以及无机沉淀物在膜面的吸附。铁锰无机沉淀物在膜面的吸附和对膜孔的堵塞是引起膜污染的主要因素。降低pH有助于控制无机沉淀在膜面和膜孔内的形成,抑制膜污染的形成。     

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0.1 MPa,搅拌速度为300 r/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＜50 mg/L,NH3-N＜10 mg/L,SS为0 mg/L,浊度为0 NTU,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.     

Irreversible fouling during multicycle microfiltration of wastewater effluent

This study focused on irreversible fouling during microfiltration of primary and secondary effluents from municipal wastewater treatment plants. Flow resistances were calculated from the sum of clean membrane resistances, resultant cake layer resistances, and consequent irreversible fouling resistances. Results from a dead-end cell experimental system showed that the accumulated cake resistance was dominating for microfiltration of primary/secondary effluents. Suspended solids in the primary and secondary effluents had a similar compressibility index, n, with a value of approximately 0.5, indicating that they were moderately compressible particles. The value of irreversible resistance is dependent on the intensity of membrane cleaning; however, for a given membrane cleaning strategy, this value steadily increased and reached a maximum after approximately 6 cycles of filtration and cleaning. This study provided an explanation for the significant drop of throughput flux in the early application of membrane processes, and a plateau flux approached correspondingly.     

BPAC-UF对二级出水中抗生素抗性基因的去除及膜污染缓解机制

采用生物粉末活性炭(BPAC)-超滤(UF)组合工艺去除控制二级出水中抗生素抗性基因(ARGs),并对ARGs的去除和BPAC缓解膜污染机制进行了探讨。结果表明：与直接超滤工艺相比,组合工艺对水中四环素类抗性基因(tetA、tetW)、磺胺类抗性基因(sul Ⅰ、sul Ⅱ)以及溶解性有机碳(DOC)的去除效果均有较大的改善,这主要是由于BPAC对ARGs的吸附降解作用所致;水中16S rDNA、int Ⅰ 1和DOC含量与不同种类ARGs浓度具有显著相关性,强化上述指标的去除可有效促进ARGs的削减;在BPAC投加量较低时,组合工艺的膜比通量较直接UF有所提高,膜污染状况明显改善;直接UF时,膜污染状况与滤饼层过滤模型的拟合度最好,而组合工艺的膜污染状况与标准膜孔堵塞模型和滤饼层过滤模型拟合度均较好。BPAC-UF组合工艺是一种较好的去除ARGs的工艺。     

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％。     

絮体性质对纳滤膜污染的影响

混凝过程产生的絮体会对后续膜过滤性能产生一定的影响。实验中利用激光粒度仪研究2种混凝剂(AlCl3和PAC)在不同投加量下的絮体性质,混凝出水(不经过沉淀)直接进入纳滤膜(NF270)装置进行过滤实验。研究表明,投加量低(<0.20 mmol/L)的情况下,混凝出水反而使纳滤通量衰减发生恶化,随着投加量的增加,纳滤膜通量衰减得到有效的减缓。直接过滤腐殖酸(HA)的膜通量衰减(J/J0)为0.65,投加量为0.50 mmol/L时,AlCl3和PAC 2种混凝剂产生的通量衰减(J/J0)分别为0.78和0.75。滤饼层阻力受到絮体尺寸的影响较大,絮体尺寸越大,形成的滤饼层透水性更好。通过污染模型分析,混凝出水的纳滤膜污染机理主要是滤饼层阻力。     

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.     

二级出水微滤过程中对醋酸纤维素酯膜的有机污染特征

低压膜过滤技术(包括微滤和超滤)在再生水生产领域正引起越来越广泛的关注。然而如何解决低压膜过滤过程中的膜有机污染问题始终是膜技术所面临的技术挑战。本研究采用醋酸纤维素酯微孔滤膜对二级出水溶解性有机物(EfOM)及其不同亲疏水性组分、蛋白模拟溶液、腐殖酸(HA)等进行恒流过滤实验。对不同有机物污染后的膜表面使用全反射傅立叶红外光谱(ATR-FTIR)和X射线电子能谱(XPS)进行表征。结果表明,相对于蛋白质和EfOM等,HA所造成的膜污染最少。ATR-FTIR的结果同时显示,以官能团而言,更多的氨化物(1535cm-1)、脂肪族物质(2860～2970cm-1)和氢氧根(3400cm-1)存在于膜表面。TMP/V数据比较结果表明,在EfOM各亲疏水性组分、蛋白质和HA的对比中,EfOM中的疏水碱性物质(HPO-B)对膜污染的贡献最大,而HA的膜污染贡献最小。UVA和荧光激发-发射光谱(FEEM)结果表明,HPO-B和蛋白质对醋酸纤维素酯膜的污染贡献较大。综合不同分析手段可以对不同有机物造成膜污染的潜能大小得出如下排序:HPO-B>蛋白质>HPO-A、HPI>HA。     

印染废水回用微滤膜污染控制研究

采用PVDF中空纤维微滤膜处理某纺织印染厂二级生化出水,研究了膜污染控制及清洗方法。结果表明,合理的膜通量是控制膜污染、保证膜寿命的关键,采用31 L/(m2.h)左右的通量有助于膜污染的控制。氢氧化钠与次氯酸钠可分别用于日常维护清洗与恢复清洗,通过循环正洗不仅能满足清洗要求,且药剂使用量也小于反洗方法,每吨产水清洗用碱费用仅0.06元。化学清洗后再水力正洗,能进一步提高清洗效果。     

Quantification of the interactions between Ca,Hg and extracellular polymeric substances (EPS) of sludge

The interactions between metals (Ca²⁺ and Hg²⁺) and extracellular polymeric substances (EPS) extracted from the aerobic and anaerobic sludge in wastewater treatment reactors were investigated using a combination of zeta potential measurement and 3-dimensional excitation–emission matrix (EEM) fluorescence spectroscopy with parallel factor (PARAFAC) analysis. Results show that Ca²⁺ had no substantial effects on the EEM fluorescence spectra of the EPS, but their zeta potentials increased with the increasing Ca²⁺ dosage. However, Hg²⁺ had a significant effect on the EEM fluorescence spectra of the EPS, while their zeta potentials seemed not to be affected by the dose of Hg²⁺. The interactions between Hg²⁺ and EPS were elucidated using the fluorescence quenching with PARAFAC analysis, while the interactions between Ca²⁺ and EPS were evaluated by the zeta potential technique. The binding constants for Hg²⁺ and EPS were two orders of magnitude higher than those for Ca²⁺ and EPS, suggesting that the binding mechanisms between Ca²⁺ and EPS were different from those between Hg²⁺ and EPS. The results might be useful for understanding the roles of EPS in bacterial self-protection against heavy metals and the aggregate formation mechanisms through ionic bridging interactions.     

Chitosan/albumin/CaCO3 as mimics for membrane bioreactor fouling: genesis of structural mineralized-EPS-building blocks and cake layer compressibility

Membrane bioreactor biofouling is usually described as an extracellular matrix in which biopolymers, inorganic salts and active microbes co-exist. For that reason, biomineralization (BM) models can be useful to describe the spatial organization and environmental constraints within the referred scenario. BM arguments were utilized as background in order to (1) evaluate CaCO₃ influence on flux decline; pore blocking and cake layer properties (resistance, permeability and compressibility) in a wide range of Chitosan/Bovine serum albumin (BSA) mixtures during step-pressure runs and, (2) perform membrane autopsies in order to explore the genesis of mineralized extracellular building blocks (MEBB) during cake layer build up. Using low molecular weight chitosan (LC) and BSA, 2 L of 5 LC/BSA mixtures (0.25-1.85 ratio) were pumped to an external ultra filtration (UF) membrane (23.5 cm², hydrophobic, piezoelectric, 100 kDa as molecular weight cut-off). Eight different pressure steps (40 ± 7 to 540 ± 21 kPa) were applied. Each pressure step was held for 900 s. CaCO₃ was added to LC/BSA mixtures at 0.5, 1.5 and 3 mM in order to create MEBB during the filtration tests. Membrane autopsies were performed after the filtration tests using thermo gravimetric, scanning microscopy and specific membrane mass (mg cm⁻²) analyses. Biopolymer-CaCO₃ step-pressure filtration created compressible cake layers (with inner voids). The formation of an internal skeleton of MEBB may contribute to irreversible fouling consolidation. A hypothesis for MEBB genesis and development was set forth.