The use of RO to remove emerging micropollutants following CAS/UF or MBR treatment of municipal wastewater

The removal of various organic micropollutants (OMPs), including six antibiotics (ERY, ROX, CLA, SMX, SMZ, and TMP), three pharmaceuticals (ibuprofen, salicylic acid, and diclofenac), one industrial product (BPA), and one hormone (cholesterol), was investigated in two pilot plants treating the same raw sewage of the Tel-Aviv WWTP. The effluent production by CAS-UF was 45 m³/h while that of MBR was 40 L/h. Each system's effluent constituted the feed for its RO, which comprised three RO steps after the CAS/UF and a semi-batch RO system after the MBR. Despite significant molecular differences between the selected OMPs, high removal rates were achieved after the RO stage (> 99% for macrolides, pharmaceuticals, cholesterol, and BPA, 95% for diclofenac, and > 93% removal of sulfonamides). However, low antibiotics concentrations and 28–223 ng/L residuals of ibuprofen, diclofenac, salicylic acid, cholesterol, and BPA in the MBR/RO and CAS-UF/RO permeates showed that although RO is an efficient removal solution, it cannot serve as an absolute barrier to OMPs. Therefore, additional treatment techniques should be considered to be incorporated aside the RO to ensure complete removal of such substances.     

Potential for reuse of high cellulose containing wastewater after membrane bioreactor treatment

It is difficult to adequately treat wastewater with a high cellulose content with the traditional anaerobic and aerobic activated sludge processes. In this study we used microfiltration (MF) and reverse osmosis (RO) membranes combined with an anaerobic or aerobic activated sludge process to treat high cellulose containing wastewater for different hydraulic retention times (HRTs). The potential target applications for reuse of the treated wastewater are also compared. Six bioreactors, which were configured as anaerobic sequencing batch reactor (ANSBR), aerobic sequencing batch reactor (ASBR), aerobic membrane bioreactor (AMBR), AMBR plus RO (AMBR/RO), anaerobic activated sludge plus aerobic MBR (AOMBR), and AOMBR plus RO (AOMBR/RO), was operated in this study. The experiment results showed that, as expected, no effluents from the ASBR or the ANSBR could meet the Taiwan EPA criteria for effluent and wastewater reuse, no matter what the HRT was. However when the HRT was 12 h or more, the effluent from the AMBR and AOMBR processes did meet the criteria for effluent, but still did not meet the treated wastewater reuse criteria , primarily due to the color, total alkalinity, and total dissolved solid parameters. Finally, the effluents from the AMBR/RO and AOMBR/RO processes did meet the Taiwan criteria for both effluent and treated wastewater reuse when the HRT for the AOMBR/RO and AMBR/RO processes was equal to or longer than 12 h and 8 h, respectively. For the HRT of 4 h for both the AOMBR/RO and AMBR/RO process, and an HRT of 8 h for the AOMBR/RO process, neither the effluent criteria nor the treated wastewater reuse criteria were met.     

A pilot study for wastewater reclamation and reuse with MBR/RO and MF/RO systems

A pilot study was conducted to evaluate the quality of the effluent of an enhanced tertiary treatment process consisting of MBR/RO or MF/RO units and explore the feasibility of reclamation of treated effluent for potable and non-potable reuse applications. The performance of both the MBR/RO and MF/RO pilot plants was excellent. The MBR or MF alone was able to bring down the concentrations of most of the pollutants under acceptable limits for non-potable reuse applications. The application of RO further improved the treated water quality, especially the aesthetical and microbial qualities. Different strategies were employed to control membrane fouling in RO, and hypochlorite dosing showed the best results. The RO permeate quality in terms of conductivity, turbidity, organic content, ammonia, nitrate, hardness, E. coli and virus could meet the water quality requirements for many potable and non-potable reuse applications. In removal of total estrogens, the MBR/RO combination performed better than that of MF with RO, indicating the importance of the role of biomass. The rejection of virus in MBR and MF was greatly affected by the chemical membrane cleaning. It took more than 24 h for the recovery, implying that the presence of membrane biofilm plays a key role in rejection of virus.     

Processing of composite industrial effluent by reverse osmosis

Reverse osmosis (RO) is a well‐established process for water desalination and effluent treatment and it is anticipated that its application could be extended to complex mixtures of industrial effluents. Pilot‐scale experiments using a spiral‐wound thin‐film composite (TFC) polyamide membrane were carried out to investigate the potential of RO for processing a composite effluent, which was a mixture of various wastewaters from bulk drug and pharmaceutical factories. Separation performance was evaluated at various feed pressures (0–70 bar) and feed concentrations (2–30 gdm^?3), and was found to improve with increasing pressure. High rejection of dissolved solids (～98%), COD, BOD and almost complete removal of color were achieved with reasonable flux rates and water recovery. The effect of concentration polarization and fouling on flux and rejection rates as functions of time was evaluated. An approximate cost estimate for an aerobic process vis‐à‐vis a RO membrane process for treatment of the composite effluent is presented. Copyright © 2003 Society of Chemical Industry     

An advanced treatment of high-strength opium alkaloid processing industry wastewaters with membrane technology: pretreatment, fouling and retention characteristics of membranes

This paper presents the results of the laboratory and pilot-scale membrane experiments of opium alkaloid processing industry effluents. Different types of ultrafiltration (UF), nanofiltration (NF) and reverse osmosis (RO) membranes were evaluated for membrane fouling, permeate flux and their suitability in separating COD, color and conductivity. Experiments demonstrated that membrane treatment is a very promising advanced treatment option for pollution control for opium alkaloid processing industry effluents. Almost complete color removal was achieved with NF and RO membranes. COD and conductivity removals were also greater than 95% and met the current local standards. Nevertheless, pretreatment was an important factor for the NF and RO membrane applications. Membrane fouling occurred with direct NF membrane applications without UF pretreatment. The total estimated cost of the UF and NF treatment system was calculated as $0.96/m³, excluding the concentrate disposal cost.     

平面显示面板生产有机工业废水的回用水处理技术

该文采用混凝沉淀、MBR和反渗透组合工艺装置针对平面显示面板生产有机废水进行深度处理。结果表明通过混凝沉淀,有机废水中的 COD能降低约10％,并减轻后续 MBR膜的有机物污堵。MBR装置出水能保持良好水质（TOC ＜10 mg/L、SDI15＜3）,很适合采用反渗透进行进一步处理。通过反渗透装置进行深度处理后,出水能达到TOC＜1 mg/L、电导率＜85μs/cm,可作为原水直接回用到超纯水制备系统。     

Threshold performance of a spiral-wound reverse osmosis membrane in the treatment of olive mill effluents from two-phase and three-phase extraction processes

A reverse osmosis (RO) treatment stage was examined for the complete depuration of the different effluents exiting the olive mill factories (OMW) working with diverse extraction procedures, that is, the two-phase and the three-phase extraction processes, respectively. In the present work, the modelization of batch RO purification of OMW by means of the relevant equations of the threshold flux theory for fouling control and plant dimension is addressed. Results show that higher threshold flux values (20.2–22.1% increase) and major feed recovery rates (80.2–85.0%) as well as very significant reduction of the long-term fouling index (27.3–52.7%) were achieved by using as pretreatment steps the following series of processes: pH-T flocculation, UV/TiO₂ photocatalysis, UF and NF in series. This leads to both lower energy and capital costs, in particular a reduction of the required membrane area in case of batch membrane processes equal to 22.3–44.8%. Accurate prediction of the rejection behavior was attained by the used leaky solution-diffusion model in all cases, with reflection coefficients (σ_COD) ranging from 0.86 to 1.0. The purified effluent streams are finally compatible with irrigation water quality standards (COD values below 1000 mg L⁻¹).     

聚氯乙烯离心母液高品质回收工艺的研究

采用膜生物反应器(MBR)和反渗透(RO)工艺对聚氯乙烯离心母液废水进行回收。研究了该系统工艺对有机物和悬浮固体的处理效果以及系统的耐冲击能力;观察了生物相在MBR系统中的变化情况及MBR膜片和反渗透膜的污染情况。试验结果表明,该工艺在稳定运行的情况下,废水总COD去除率可达到95%以上,MBR出水COD浓度低于40 mg/L,达到直接排放标准,再经过反渗透、离子交换或连续电解除盐(EDI)处理后,出水可以达到聚合回用水标准,回收率达到70%以上,而且,整个试验过程中膜耐污染性能良好。     

Treatment of Fumaric Acid Wastewater Using Integrated Process of Hollow-Fiber Supported Liquid Membrane-Strip Dispersion with Reverse Osmosis

In this paper, the integrated process of series connected hollow-fiber supported liquid membrane-strip dispersion (HFSLM-SD) with reverse osmosis (RO) was designed and used to recover fumaric acid (FA) from waste effluents and treat FA wastewater. The results showed that FA could be almost completely recovered by this integrated process, and TOC of wastewater finally decreased to the environment acceptable level. In addition, the continuous operation of wastewater treatment was implemented by the integrated process. After FA wastewater was extracted by six series connected HFSLM-SD modules, its TOC decreased from 35625 mg/L to 1000 mg/L, and the TOC removal rate reached 97.17%. Then the effluent from HFSLM-SD was further treated by RO, and TOC of permeate in RO was below 100 mg/L. The total TOC removal rate of the integrated process was as high as 99.7%. Furthermore, the effect of the osmotic pressure of RO process on TOC in the feed was obtained. The investigation of RO membrane fouling revealed that washing process was necessary because of the serious fouling in RO system.     

膜法处理石化废水探索研究

以膜生物反应器(MBR)和膜混凝反应器(MCR)分别处理石化污水厂水解池出水和二沉池出水.结果发现水力停留14.5 h,DO约4 mg/L时,MBR对石化废水的化学需氧量(COD)去除率达到88 %,膜出水COD为71.3 mg/L.以MCR对污水厂出水进行深度处理,发现PAC约10 mg/L为最佳投药量,此时COD去除率达到32 %,膜出水COD为75.6 mg/L.以两种微滤膜反应器出水进行淤泥密度指数(SDI)实验,SDI在3～5之间,可以作为RO进水,但为了RO系统的稳定运行,应进一步对出水进行深度处理.     

Fouling of reverse osmosis membranes by hydrophilic organic matter: implications for water reuse

Effluent organic matter (EfOM) is suspected as a major cause of fouling of reverse osmosis (RO) membranes in advanced wastewater reclamation. Among the main constituents in EfOM, polysaccharides are the most ubiquitous. The influence of solution chemistry and hydrodynamics on RO membrane fouling with alginate — a model for polysaccharides in secondary wastewater effluent — was systematically investigated. Results of fouling runs with alginate demonstrate that RO membrane fouling increases with decreasing pH, increasing ionic strength, and addition of calcium ions. At fixed solution ionic strength and pH, the presence of divalent calcium ions, at concentrations typical of those found in secondary wastewater effluent, had a dramatic effect on membrane fouling. However, for similar concentrations of divalent magnesium ions, fouling was negligible. The severe fouling in the presence of calcium is attributed to the formation of a thick, dense alginate gel layer on the membrane surface via calcium-alginate complexation and crosslinking (bridging) of alginate macromolecules by calcium. In addition to solution chemistry, hydrodynamic operating conditions — initial permeate flux and crossflow velocity — were also shown to influence RO membrane fouling with alginate.     

Influence of filtration conditions on the performance of nanofiltration and reverse osmosis membranes in dairy wastewater treatment

Filtration performance and fouling of nanofiltration (NF) and reverse osmosis (RO) membranes in the treatment of dairy industry wastewater were investigated. Two series of experiments were performed. The first one involved a NF membrane (TFC-S) for treating the chemical-biological treatment plant effluents. The second one used a RO membrane (TFC-HR) for treating the original effluents from the dairy industry. The permeate flux was higher at higher transmembrane pressures and higher feed flowrates. The curves of permeate flux exhibited a slower increase while the feed flowrate decreased and the pressure increased. Membrane fouling resulted in permeate flux decline with increasing the feed COD concentration. Furthermore, the flux decline due to the COD increase was found higher at higher pressures for both NF and RO membranes.     

膜生物反应器+反渗透工艺对再造烟叶废水的处理

采用膜生物反应器(MBR)和反渗透(RO)组合工艺,深度处理再造烟叶生产的废水。结果表明:经"MBR+RO"处理后,废水的COD、色度、氨氮、浊度等的去除率均达到95%以上,RO出水(回用水)完全可以满足生产需要,部分指标优于生活饮用水。     

The possibility and applicability of coagulation-MBR hybrid system in reclamation of dairy wastewater

The significant improvements of membrane technology in reliability and cost effectiveness have increased the reuse probability and recycling extent of dairy wastewater. However, membrane fouling still remains a major bottleneck in wide application. In order to solve the problem, this paper investigated the possibility and applicability of coagulation-membrane bioreactor (MBR) hybrid system in reclaiming dairy wastewater. A comparative experiment based on the removal efficiencies and the membrane performance was designed to achieve the purpose. The results showed that polyaluminium chloride as the appropriate coagulant in coagulation process was effective for turbidity removal. Coagulation process played a very important role in stabilizing the effluent of MBR and the level of transmembrane pressure. MBR was a crucial process in turbidity and aluminum removal. MBR had the capability to resist shock loading and to maintain the high COD removal. Biological flocs in MBR could improve the fouling level of membrane. The hybrid system reduced 98% COD from the original and COD value of the wastewater came down to 8 mg/L. The combination of coagulation with MBR presents the possibility and applicability to reclaim effluent in dairy industries.     

Pilot-scale testing of reverse osmosis using conventional treatment and microfiltration

In order to meet the growing needs of its consumers, the Metropolitan Water District of Southern California is looking for ways to desalt water from the relatively hard Colorado River. This study evaluated conventional treatment as the pretreatment step for reverse osmosis (RO) desalting. Other pretreatment options studied include microfiltration (MF) and conventional treatment with ozone and biologically active filters. Each of three pretreatment scenarios produced effluent waters generally considered appropriate for use with RO [median turbidity of less than 0.1 Nephelometric turbidity unit (NTU) and median silt density index of less than 3]. Both microfiltered and ozonated/ biofiltered waters gave steady RO performance over 3 months of testing. However, conventional treatment left the RO system vulnerable to organic and biological fouling. Despite maintaining a 2-2.5 mg/L chloramine residual, pretreatment using conventional treatment required more frequent cleanings than either MF or ozonation/biofiltration (O₃/BF). The good performance for biofiltered water may have resulted from the stabilization of the natural organic matter through the O₃/BF process. Microfiltration, with its superior particle and bacteriological removal characteristics, provided the best RO pretreatment technology.     

臭氧-活性炭技术对膜生物反应器膜污染减缓研究

本研究目的是探讨臭氧-活性炭技术对膜生物反应器（membrane bioreactor,MBR）膜污染减缓的影响。通过短期批式实验表明,粉末活性炭（power activated carbon,PAC）可强化臭氧的氧化效果,臭氧投加量超过0.25mg/(gSS)将恶化污泥混合液可滤性;对滤出液残余臭氧浓度检测表明,PAC的加入有利于维持本体溶液臭氧浓度。臭氧-活性炭技术引入MBR系统有助于膜污染的减缓,反应器内微生物活性受到一定的抑制作用,但对MBR出水水质影响较小;臭氧-活性炭减小了反应器内溶解性微生物产物（soluble microbial products,SMP）中的蛋白质及多聚糖含量,显著降低了污泥絮体中松散的胞外聚合物（loosely bound EPS,LB）及胞外聚合物（extracellular polymeric substances,EPS）中蛋白质浓度,以上结果表明应用臭氧-活性炭技术来延缓MBR膜污染是可行的。     

基于小孔径PVDF内衬膜A/O-MBR膜污染分析

为研究膜生物反应器膜污染问题,在缺氧-好氧一体式膜生物反应器中,对模拟生活污水的处理效果进行考察,考察了4种不同孔径聚偏氟乙烯(PVDF)内衬膜对膜污染的影响规律。结果表明,基于小孔径PVDF膜的MBR工艺对模拟生活污水中COD、NH3-N的去除率分别达到96%、90%,出水浊度在0.35 NTU以下;在操作条件固定的情况下,随着膜孔径增加,临界通量逐渐降低;孔径越小,跨膜压差上升越缓慢,膜污染较轻。膜污染模型分析结果显示:无论何种孔径的膜,在MBR系统中,滤饼层和凝胶层污染所占的比例都最大(>80%),因此,在使用过程中减缓滤饼层及凝胶层的形成至关重要。     

A comparative study of the growth of lactic acid bacteria in a pilot scale membrane bioreactor

BACKGROUND: A central problem in the production of lactic acid bacteria (LAB) is the low productivity conventional batch systems due to end product inhibition. This work investigated the impacts of the membrane bioreactor (MBR) on the growth of four industrially important LAB and compared the growth in pH controlled STR using Lactobacillus buchneri, L. brevis, Oenococcus oeni, and Bifidobacterium longum. RESULTS: The four LAB were grown in a pH‐controlled STR batch culture and this was compared with perfusion culture of the MBR. The growth of LAB in MBR produced a far more intensive production of cells with great volumetric productivity and high cell concentrations compared with STR cultures. Total cell concentration in perfusion culture of LAB reached 13 to 23 g DCW L^?1 up to 14 times higher than those obtained in the STR cultures. Overall volumetric biomass production rates in the MBR increased from 10 to 33 times that in the STR, and were organism dependent. CONCLUSION: The MBR has considerable potential for enhanced production of LAB. Limitations to growth and growth rate during perfusion culture of LAB in the MBR were from gas bubbles produced or membrane fouling. Further improvements in productivities are possible with careful design of the media, the MBR reactor and the performance characteristics of the LAB. Copyright © 2010 Society of Chemical Industry     

垃圾渗滤液生化出水絮凝-纳滤处理及过程机理

垃圾焚烧发电厂渗滤液是一种含高浓度腐殖酸类物质和高盐含量的复杂有机废水, 传统生化处理后仍难达标排放。本工作围绕垃圾渗滤液生化出水的特性, 开展了Ca(OH)₂絮凝、臭氧氧化预处理与NF处理相结合的处理工艺, 并对处理过程的机理进行了探讨。研究表明, 渗滤液生化出水经过Ca(OH)₂絮凝处理, 可以有效地去除其中的杂环类化合物。生化出水经8 g·L^-1的Ca(OH)₂絮凝处理后, 比MBR出水产水通量提高达8.2%。对Ca(OH)₂絮凝出水进行臭氧氧化处理, 虽然降低了它的COD, 但并未进一步提高其NF膜通量, 其主要原因可能是臭氧氧化生成的硅氧烷类物质造成了膜的污染;与RO处理垃圾渗滤液生化出水相比较, NF膜无法分离废水中的酮类、胺和酰胺类、杂环类化合物, 使得NF产水的COD处在100~160 mg·L^-1。NF平均膜通量的增大可导致产水COD略有上升;垃圾渗滤液生化出水及其预处理水在NF处理过程中, 都没有表现出严重的膜污染。     

A comparison of submerged and sidestream tubular membrane bioreactor configurations

This paper provides an improved understanding of the effect of sidestream (SS) and submerged (Sub) MBR configurations on hydraulic and biological system performance for a tubular membrane geometry. Effects of key flow parameters, these being aeration rate (U_G) in the Sub MBR and cross flow velocity (CFV) in the SS MBR, on fouling behaviour have been assessed during short-term flux-step experiments. Both synthetic and real sewage feeds have been used. Series of tests carried out with both feeds indicate the similar fouling behaviour observed for Sub and SS MBRs operated at U_G of 0.07-0.11 m s⁻¹ and CFV of 0.25-0.55 m s⁻¹ respectively. Analysis of the TMP-based parameters determined from the flux-step experiments show the effect of U_G in Sub configuration to be greater than those of CFV in SS MBR, and to be more efficient at higher fluxes (up to 97% decrease in fouling rate for U_G increased from 0.02 to 0.2 m s⁻¹, at 291 m⁻² h⁻¹). The influence of MBR configuration on biomass characteristics was also assessed by acclimatising the biomass at three MLSS concentrations for both configurations and revealed the carbohydrate contained in the biomass supernatant to be a possible indicator of fouling for MBR operation.