膜污染和膜材料的最新研究进展

介绍了近两年来国际上膜污染和膜材料领域的最新研究进展。目前,研究学者对膜污染机理进行了深入研究,建立了新的膜污染表征和控制方法,并通过膜材料的改性来逐步解决膜污染问题。     

膜生物反应器膜污染及其防治技术

讨论了膜污染对膜生物反应器运行的影响,对膜污染现象、膜污染过程及其种类对膜生物反应器的冲击进行了综述。通过分析认为：膜污染的影响因素主要有膜的性质、活性污泥混合液和膜组件的运行条件等,其中后两者为主要因素。     

延缓膜生物反应器中膜污染的措施探讨

膜生物反应器是膜分离技术和污水生物处理技术有机结合的一种污水处理工艺，与传统污水处理工艺相比具有很多优点，但膜污染限制了该工艺的广泛应用。介绍了膜污染的定义，系统论述了膜污染的研究进展，着重从改良膜的性质、改善污泥混合液的特性和优化膜分离操作条件等三个方面介绍了国内外有效延缓膜污染的技术措施。     

膜生物反应器中膜污染问题概论

膜生物反应器(Membrane Bioreactor,MBR)是一种新的高效污水处理工艺,同时,MBR也存在至今尚未得到很好解决的技术难题——膜污染。文中综述了对膜污染机理研究的相关成果,介绍了相关的解决措施,并展望了今后的发展前景。     

三种一体式MBR的膜污染趋势比较

对活性污泥—膜生物反应器、生物膜—膜生物反应器、复合式膜生物反应器的除污效果和膜污染趋势进行了研究。结果表明:活性污泥—膜生物反应器的膜污染程度最轻,膜通量下降速度最慢,膜污染也最容易消除;生物膜—膜生物反应器的膜污染程度最重,膜通量的下降速度最快;较大的曝气量可减轻膜的污染程度并减缓膜通量的下降速度。     

超声波控制膜生物反应器膜污染研究

近年来,膜生物反应器在污水处理领域中得到了广泛的应用,它具有占地面积小,剩余污泥量少和出水水质好,可以达到回用的标准的特点.然而膜污染控制问题一直是此种方法在应用中的一个难题.本文介绍了采用低强度超声波控制污水回用中膜生物反应器的膜污染的研究及得到的初步成果.通过小试,确定超声波辐照可以使膜清洗周期延长,对膜污染有一定...     

添加剂对减缓膜生物反应器中膜污染的作用研究

膜生物反应器(MBR)具有高效、出水水质好的特点,在生活污水和工业废水处理中得到应用,但膜污染是MBR广泛应用的主要障碍。通过向膜生物反应器中投加添加剂,人为改善反应器中活性污泥混合液的性质,从而减缓膜污染进程成为一种新兴的膜污染控制技术。总结近年来对添加剂减缓膜生物反应器中膜污染的效果和机制的研究,以期找到更有效、廉价的减缓膜污染添加剂。     

膜生物反应器及膜污染的研究进展

在综合大量国内外文献的基础上，阐述了膜生物反应器的发展历程、类别、膜污染及相应解决措施，并展望了膜生物反应器的发展前景。     

膜生物反应器中膜污染机理研究

膜生物反应器(MBR)结合了生物反应器有效去除有机物和膜分离组件高出水水质的优点,广泛应用于处理各种生活污水和工业废水,限制MBR进一步推广应用的主要因素是膜污染。膜污染造成水通量急剧下降和出水水质变差。MBR中膜污染的形成机理复杂,不仅与膜材料、膜孔大小、膜的疏水性和表面电荷等物理化学特性相关,而且和废水、污泥和上清液的特性有密切的关系。本综述从混合液悬浮固体浓度、污泥结构特点、上清液特征和组成成分及胞外聚合物等几方面对造成膜污染现象的机理进行分析总结,以找到制约和减少膜污染发生的具体方向。     

抽停比和膜组件放置方式对MBR膜污染的影响

采用PVC新型材料MBR反应器处理模拟生活污水,控制其MLSS在4 500~6 500mg/L之间,探讨了出水抽停比和膜组件的放置方式对膜污染的影响。结果表明,当以12 min为一周期时,其最佳抽停比为9 min/3 min,这一模式是该新型材料MBR反应器的经济出水模式;当进行在线清洗时,膜组件水平放置的MBR反应器的膜污染速率为2.26 kPa/d,膜组件竖直放置的MBR反应器的膜污染速率为1.28 kPa/d;进行在线水洗和0.02%的次氯酸钠清洗,可有效降低膜污染速率,延缓膜污染,降低运行成本。     

Analysis of fouling mechanisms in anaerobic membrane bioreactors

In this paper, we investigate the fouling mechanisms responsible for MF and UF membrane flux decline in Anaerobic Membrane Bioreactors (AnMBR). We have used the fouling mechanism models proposed by Hermia (1982), namely pore constriction, cake formation, complete blocking and intermediate blocking. Based on an optimization approach and using experimental data extracted from the literature, we propose a systematic procedure for identifying the most likely fouling mechanism in play. Short-term as well as long-term experiments are considered and discussed. It was found that short-term experiments are usually characterized by two fouling phases during which the same fouling mechanism or two different mechanisms affect the process. In contrast, in long-term experiments involving cleaning cycles, membrane fouling appears to be better ascribed to one phase only.The impact of abiotic parameters on membrane fouling mechanisms is reviewed and discussed in the light of these results. Finally, it is shown that the mechanism most responsible for membrane fouling in an AnMBR is cake formation. This main result will be useful for the future development of simple integrated models for optimization and control.     

操作条件及运行通量对超滤膜污染的影响

从优化操作工艺和摸索长期运行零污染通量2个角度对浸没式超滤膜污染进行了研究.结果表明:曝气强度为40m3/(m2·h)时,对膜污染的去除可取得良好的效果;运行周期越短,膜污染越轻;存在一个通量范围,在此范围内,TMP和膜阻力随时间增长缓慢,一旦超出了这个范围,TMP和膜阻力便会随时间增长迅速增加.     

Novel electrokinetic approach reduces membrane fouling

An innovative submerged membrane electro-bioreactor (SMEBR) was built to reduce membrane fouling through a combination of various electrokinetic processes. The objective of this research was to assess the capability of SMEBR to reduce fouling under different process conditions. At the bench scale level, using synthetic wastewater, membrane fouling of the SMEBR was compared to the fouling of a membrane bioreactor (MBR) in five runs. Different protein concentrations in the influent synthetic wastewater were selected to develop different membrane fouling potentials: high (240 mg/l), low (80 mg/l) and zero protein addition. The MBR and SMEBR were operated at a flux equal to the membrane critical flux in order to create high fouling rate conditions. Membrane fouling rate, expressed as the change in the trans-membrane pressure per day (kPa/d), decreased in the SMEBR 5.8 times (standard deviation (SD) = 2.4) for high protein wastewater, 5.1 times (SD = 2.4) for low protein content, and 1.3 times (SD = 0.7) for zero protein, when compared to the MBR. The supernatant concentrations of the soluble microbial products (SMP) were 195–210, 65–135 and less than 65 mg/l in respective experimental series. Following the bench scale study, membrane fouling was assessed in a pilot scale SMEBR, fed with raw un-clarified municipal wastewater, and operated under real-sewage variable quality conditions. The pilot SMEBR exhibited three times smaller membrane fouling rate than the MBR. It was concluded that electrokinetic processes generated by SMEBR led to a reduction of membrane fouling through: i) removal of soluble microbial products (mainly protein and polysaccharides) and colloidal organic materials; ii) change of the structure and morphology of the suspended solids due their conditioning by DC field.     

Effects of magnetic ion exchange pretreatment on low pressure membrane filtration of natural surface water

Magnetic ion exchange (MIEX) pretreatment has been increasingly employed by water treatment plants for removal of dissolved organic carbon (DOC). In this study, the effects of MIEX pretreatment on low pressure membrane filtration of natural surface water were investigated under different feedwater qualities, membrane properties, and MIEX dosing conditions. Regardless of feedwater DOC, moderate decrease in the total and hydraulically irreversible fouling was observed for a polyvinylidene fluoride (PVDF) microfiltration membrane and a polyethersulfone ultrafiltration (UF) membrane after MIEX pretreatment, which was coincident with moderate removals of high molecular weight DOC in the feedwaters. Comparatively, the fouling of a PVDF UF membrane did not decrease after MIEX pretreatment, revealing the impact of membrane properties on membrane fouling in the presence of MIEX pretreatment. Reuse of virgin or regenerated MIEX resulted in similar membrane fouling as observed with single use of the virgin MIEX. The level of DOC removal by MIEX was similar to the removal of MS2 bacteriophage spiked in the feedwater, suggesting a potential similarity in the removal of organic and microbial particles. In conclusion, MIEX pretreatment was effective for DOC removal, but less effective in controlling short-term membrane fouling or removing viruses.     

Reduced membrane fouling in a novel bio-entrapped membrane reactor for treatment of food and beverage processing wastewater

A novel Bio-Entrapped Membrane Reactor (BEMR) packed with bio-ball carriers was constructed and investigated for organics removal and membrane fouling by soluble microbial products (SMP). An objective was to evaluate the stability of the filtration process in membrane bioreactors through backwashing and chemical cleaning. The novel BEMR was compared to a conventional membrane bioreactor (CMBR) on performance, with both treating identical wastewater from a food and beverage processing plant. The new reactor has a longer sludge retention time (SRT) and lower mixed liquor suspended solids (MLSS) content than does the conventional. Three different hydraulic retention times (HRTs) of 6, 9, and 12 h were studied. The results show faster rise of the transmembrane pressure (TMP) with decreasing hydraulic retention time (HRT) in both reactors, where most significant membrane fouling was associated with high SMP (consisting of carbohydrate and protein) contents that were prevalent at the shortest HRT of 6 h. Membrane fouling was improved in the new reactor, which led to a longer membrane service period with the new reactor. Rapid membrane fouling was attributed to increased production of biomass and SMP, as in the conventional reactor. SMP of 10-100 kDa from both MBRs were predominant with more than 70% of the SMP <100 kDa. Protein was the major component of SMP rather than carbohydrate in both reactors. The new reactor sustained operation at constant permeate flux that required seven times less frequent chemical cleaning than did the conventional reactor. The new BEMR offers effective organics removal while reducing membrane fouling.     

Extracellular polymeric substances (EPS) properties and their effects on membrane fouling in a submerged membrane bioreactor

A pilot-scale submerged membrane bioreactor (MBR) for real municipal wastewater treatment was operated for over one year in order to investigate extracellular polymeric substances (EPS) properties and their role in membrane fouling. The components and properties of bound EPS were examined by the evaluation of mean oxidation state (MOS) of organic carbons, Fourier transform infrared (FT-IR) spectroscopy, three-dimensional excitation-emission matrix (EEM) fluorescence spectroscopy, and gel filtration chromatography (GFC), etc. Test results showed that MOS of organic carbons in the bound EPS was ranging from −0.14 to −0.51, and major components could be assessed as proteins and carbohydrates. FT-IR analysis confirmed the presence of proteins and carbohydrates in the bound EPS. The organic substances with fluorescence characteristics in the bound EPS were identified as proteins, visible humic acid-like substances and fulvic acid-like substances by EEM technology. GFC analysis demonstrated that EPS had part of higher MW molecules and a broader MW distribution than the influent wastewater. It was also found that a high shear stress imposed on mixed liquor could result in the release of EPS, which would in turn influence membrane fouling in MBRs. Bound EPS solution was observed to have a stronger potential of fouling than mixed liquor. During long-term operation of the MBR, bound EPS demonstrated positive correlations with membrane fouling while temperature was verified as a negative factor affecting EPS concentration. Compared to tightly bound EPS (TB-EPS), loosely bound EPS (LB-EPS) showed more significant correlations with membrane fouling. This critical investigation would contribute towards a better understanding of the behavior, composition and fouling potential of EPS in MBR operation.     

浸没式膜工艺处理滦河水的膜污染清洗技术研究

对浸没式膜工艺处理滦河原水过程中采用的三种膜污染清洗技术进行了中试研究.试验结果表明,对膜定期进行反冲洗是防治膜污染的必要手段.EFM操作是防治膜污染的有效措施.EFM执行时间和清洗剂浓度对清洗效果有一定影响,在该试验工况下,EFM执行时间在45～60 min较为合适,清洗剂选择0.41%NaOH和800 mg/L NaClO为宜.化学清洗可使膜性能得到极大恢复,对于高温高藻期滦河水,碱洗效果要比酸洗效果好.操作优化试验表明,化学清洗前进行3次物理清洗可最大发挥物理清洗的强化作用;化学清洗后进行4次物理清洗可避免清洗残留液对正常过滤的出水水质造成影响.     

Fouling of proton exchange membrane (PEM) deteriorates the performance of microbial fuel cell

The fouling characteristics of proton exchange membrane (PEM) in microbial fuel cell (MFC) and the resulting deterioration of MFC performance were explored in this study. It was observed that the ion exchange capacity, conductivity and diffusion coefficients of cations of PEM were reduced significantly after fouling. Imaging analysis coupled with FTIR analysis indicated that the fouling layer attached on PEM consisted of microorganisms encased in extracellular polymers and inorganic salt precipitations. The results clearly demonstrate that PEM fouling deteriorated the performance of MFCs and led to a decrease in electricity generation. Cation transfer limitation might play an important role in the deterioration of MFC performance because of the membrane fouling. This was attributed to the physical blockage of charge transfer in the MFC resulted from the membrane fouling. With the experimental results, the effect of membrane fouling on the electrical generation of MFCs was evaluated. It was found that the decreased diffusion coefficients of cations and cathodic potential loss after membrane fouling contributed mainly to the deterioration of the MFC performance.     

Contaminated particle characteristics influence on membrane fouling

The goal of the current research study was to critically examine the role of the shape of contaminated particles for an accurate prediction of membrane fouling phenomenon. Polycarbonate flat membranes with uniform pore sizes of 0.05 µm and 0.1 µm, in addition to Polysulfone membranes with molecular weight cut of 60,000, were used under a constant feed flow rate and a cross‐flow mode in ultrafiltration of a latex paint solution featuring a wide range of particle size distribution. The current mathematical model was developed to illustrate the effect of irregularity and polydispersity of latex particles on the mass of fouling and irreversible fouling on membranes. The results obtained indicate that the sphericity of contaminated particles had a significant influence on fouling potential at different aggregation levels.     

Characterisation of initial fouling in aerobic submerged membrane bioreactors in relation to physico-chemical characteristics under different flux conditions

The initial fouling characteristics of aerobic submerged membrane bioreactors (MBRs) were analysed under different flux conditions. Physico-chemical analyses of the mixed liquor hinted that carbohydrates were more important to membrane fouling than proteins. However, this contrasted with the characterisation of foulants on the membrane surfaces. Micro-structural analyses of the foulants on the membrane surfaces showed that the dominant foulants were different under different flux conditions. Membrane fouling occurred through a biofilm-dominated process under lower flux conditions, but the mechanism shifted towards a non-biofilm, organic fouling process as the flux was increased. In spite of the differences in fouling mechanisms, it was found that the protein fraction on the membrane surfaces, in the initial stages of MBR operations, had the greatest impact in the rise of transmembrane pressure.