Direct drinking water treatment by spiral-wound ultrafiltration membranes

This paper presents the results of a research on direct drinking water treatment through an ultrafiltration pilot plant unit using spiral-wound membranes (3500 MWCO). The source of water is the Guarapiranga Reservoir, an eutrophicated water body located in the metropolitan region of São Paulo, Brazil. The data were collected during a period of almost 3400 h, from August 2005 to January 2006. The main objective of the study was to evaluate the membrane production capacity and contaminant removal efficiency. It was verified that the system was able to produce a high quality permeate with a flow close to the specified by the membrane manufacturer. The average permeate flow was 19.7 L.h⁻¹.m⁻², at 467 kPa and 25°C, with a global water recovery of almost 85%. The removal efficiencies for TOC, UV light absorption, and turbidity were 85%, 56%, and 95%, respectively. The results provide substantial evidence of the technical feasibility of spiral-wound UF membranes for direct drinking water treatment from euthrophicated sources, as an alternative for conventional drinking water treatment systems.     

Membrane application for recovery and reuse of water from treated tannery wastewater

Secondary treated tannery wastewater contains high concentrations of Total Dissolved Solids (TDS) and other residual organic impurities, which cannot be removed by conventional treatment method. A pilot plant membrane system with a designed processing capacity of 1 m³/h, comprising of nano and reverse osmosis (RO) membrane units, accompanied by several pre-treatment operations, was evaluated in order to further treat and reuse the tannery wastewater. The maximum TD S removal efficiency of the polyamide RO membrane was more than 98%. The permeate recovery of about 78% was achieved. The water recovered from the membrane system, which had very low TDS concentration, was reused for wet finishing process in the tanneries. The reject concentrate obtained from the operation was sent to solar evaporation pans. It was evident from the study that the membrane system can successfully be applied for recovery of water from secondary treated tannery effluent, provided a suitable and effective pretreatment system prior to membrane system is employed. Combining nano and RO membranes improved the life of the membranes and permeate recovery rate.     

Study of drinking water treatment by ultrafiltration of surface water and its application to China

In China, many water supplies depend on conventional water treatment. Due to unfit soil and water conservationin some regions of China, conventional water treatment has showed some defects for the poor quality of water resource. In addition, advances in membrane technology and increasing requirements on water quality have stimulated ultrafiltration (UF) for water treatment. In this research, OF test apparatus was set up to produce drinking water from raw water of the Binxian Reservoir (China). The performance of UF membranes was investigated. There was a linear relationship between membrane resistance and accumulated permeate water. Using coagulation before OF increased permeate flux and retarded membrane flux decline. Surprisingly, membrane permeate flux in a coagulation/UF process was higher than that in coagulation-sand filtration-UF process with raw water of medium turbidity. OF treatment provided effective turbidity removal. Iron, manganese and aluminum were removed completely. The UF membrane also perfectly removed all coliform bacteria. The reduction of total organic carbon was satisfactory. The treated water quality complied with China's drinking water guidelines. The Ames test showed that the mutagenic activities of membrane permeate water was negative.     

Nanocomposite hollow fiber nanofiltration membranes: Fabrication,characterization, and pilot-scale evaluation for surface water treatment

Thin-film nanocomposite (TFN) membranes were fabricated by interfacial polymerization of a polyamide (PA) layer on the shell side of hollow fiber membrane supports. TiO₂ nanoparticle loadings in the thin-film layer were 0.01, 0.05, and 0.20 wt %. Nanoparticle-free PA thin-film composite (TFC) membranes served as the comparative basis. The TFN membranes were characterized in terms of the chemical composition, structure, and surface properties of the separation layer. Incorporating nanoTiO₂ improved membrane permeability up to 12.6-fold. During preliminary laboratory-scale evaluation, TFN membranes showed lower salt rejection but higher TOC rejection in comparisons with the corresponding values for TFC controls. Based on the performance in lab-scale tests, TFN membranes with 0.01 wt % nanoTiO₂ loading were selected for an evaluation at the pilot scale with synthetic surface water as the feed. While the permeate flux during long-term pilot-scale operation gradually decreased for TFC membranes, TFN membranes had a higher initial permeate flux that gradually increased with time. The TOC rejection by TFN and TFC membranes was comparable. We conclude that TFN membranes show promise for full-scale surface water treatment applications. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 48205.     

Application on to nanofiltration to water management options for oil sands operation

A membrane separation process, nanofiltration (NF), has been applied successfully for treatment of oil sandswaters, particularly to water softening and removal of toxic components. This study focused on the selection of appropriate membranes and the assessment of their performance for the removal of polyvalent ions (hardness) and naphthenic acids (NA) (the main acute toxicant in oil sands process-affected imported waters) from both imported and potential discharge waters. Experiments were carried out using a bench-scale flat sheet membrane system with several commercially available NF membranes. It was found that after membrane filtration, both water hardness and the NA concentrations were reduced significantly (>95%). A permeate flux was maintained at 15 L/m²/h or higher, with a retentate volume of about 10% of the feed volume.     

Application of membrane distillation technology in the treatment of table olive wastewaters for phenolic compounds concentration and high quality water production

Direct contact membrane distillation process (DCMD) is proposed for the treatment of table olive wastewaters (TOW) for high quality water production and concentration of their phenolic compounds. The main objective was to investigate the effectiveness of DCMD process to concentrate phenolic compounds from TOW that can be reused as a potential source for powerful natural antioxidants. The performance of three commercial membranes, made from polytetrafluoroethylene supported by polypropylene net (TF200, TF450 and TF1000), were tested. The permeate fluxes and polyphenols concentration in both the permeate and retentate have been monitored under different DCMD operating temperatures. It was found that the three membranes exhibit an excellent separation coefficient (greater than 99.5%) even after 4 h of DCMD operation with TOW. High concentration factors were obtained with the membrane TF450 at 70 °C, while the membrane TF200 having the lowest pore size was found to be more resistant to fouling phenomenon compared to the other membranes since the reduction of its water permeate flux after TOW treatment did not exceed 2.9%. High quality of the permeate was obtained with phenolic concentration lower than 16 mg of TYE/L. In addition, the values of electrical conductivity of the permeate were lower than 193 μS/cm for the membranes TF450 and TF200, and lower than 355 μs/cm for the membrane TF1000. Consequently, DCMD proved to be an effective process for the treatment of TOW for high quality water production and a phenolic-rich concentrate.     

Low-pressure RO membrane desalination of agricultural drainage water

Agricultural drainage water is a complex mixture of dissolved and suspended chemical species and may contain a wide variety of microorganisms. The application of membrane systems for desalination of agricultural drainage (AD) water requires careful consideration of feed water quality, suitable membrane selection and operating conditions. In order to evaluate the potential applicability of low-pressure reverse osmosis (RO) to the treatment of AD water, a diagnostic approach to membrane selection and process evaluation was undertaken in support of a pilot field study in the California San Joaquin Valley. Five candidate membranes were evaluated in a diagnostic laboratory membrane system which provided an initial selection based on salt rejection and product water flux performance for model salt solutions of univalent and divalent cations. Biofouling potential of the selected membranes was also evaluated using two standards strains of bacteria. Preliminary pilot plant performance, based on the selected membranes, was encouraging and has provided the basis for long-term pilot plant testing at higher recoveries to assess the impact of fluctuating AD water feed composition.     

组合膜-表面活性剂法处理垃圾渗滤液中的氨氮

氨氮是《生活垃圾填埋污染控制标准》(GB 16889-1997)严格控制的、也是传统工艺难处理的一项指标。文中以北京市北神树垃圾填埋场渗滤液为研究对象,采用组合膜-表面活性剂法对其氨氮进行了处理。水样依次通过OSMONICS微滤EW膜和超滤GE膜后,调节膜出水pH值为6.5,加入质量分数0.02%的十二烷基苯磺酸钠(SD-BS),通过静电引力与NH4+形成大分子的复合态铵,然后经反渗透SE膜进一步处理。处理后的水样清澈透明,无异味,水质达到了GB 16889-1997的一级排放标准,氨氮去除率为99.4%。另外还探讨了水样的pH值、SDBS投加量等因素对氨氮去除率的影响。     

Surface characterization and performance evaluation of commercial fouling resistant low-pressure RO membranes

This paper describes the characterization and evaluation of various RO/NF membranes for the treatment of seasonally brackish surface water with high organic contents (TOC ≈21 mg/L). Twenty commercially available RO and NF membranes were initially evaluated by performing controlled bench-scale flat-sheet tests and surface characterization. Based on the results, four low pressure RO membranes were selected for use in the pilot study. The surface characterization revealed that each of four selected membranes had unique surface characteristics to minimize membrane fouling. Specifically, the LFC1 membrane featured a neutral or low negative surface to minimize electrostatic interactions with charged foulants. The X20 showed a highly negatively charged surface, and thus, was expected to perform well with feed waters containing negatively charged organics and colloids. The BW30FR1 exhibited a relatively neutral and hydrophilic surface, which could be beneficial for lessening organic and/or biofouling. The SG membrane had a smooth surface that made it quite resistant to fouling, particularly for colloidal deposition. In the large-scale pilot study using single element, all of the four membranes experienced a gradual increase in specific flux over time, indicating no fouling occurred during the pilot study. The deterioration of permeate water quality such as TDS was also observed over time, suggesting that the integrity of the membranes might be compromised by the monochloramine used for biofouling control.     

Effect of different operation pressures for various membranes on the performance of RO plants

The aim was to study the effect of different operation pressures on the performance of reverse osmosis (RO) plants for various types of membranes. The study was conducted in a pilot plant at the University of Basrah, College of Engineering, which has a capacity of 9 m³/h. The plant is comprised of two parallel vessels containing five elements for each vessel, 8″ in diameter and 40″ in length. The first vessel has Saehane membranes, type RE8040BE-400 ft² manufactured in South Korea. Koch membranes, type 8822-XR-365 ft² made in the US, were used in the second vessel. The pilot plant uses brackish water from the Tigris River with TDS <600 ppm. The new type of RO membranes (Saehane) were used for the first trial for production of desalted water from brackish water less than 600 ppm and the results were compared with performance of the Koch membranes. It was found that over 180 days of continuous operation, the amount of permeate for Saehane membranes is larger than Koch membranes by about 26%. It was also observed that the quality of permeate water stream for Koch membranes is less than for the Saehane membranes by about 11%.     

Application of ultrafiltration membranes for removal of humic acid from drinking water

Humic acids are primarily a result of the microbiological degradation of surrounding vegetation and animal decay and enter surface waters through rain water run-off from the surrounding land. This often gives rise to large seasonal variations, high concentrations in the wet season and lower concentrations in the dry season. Alone humic acid is just a colour problem but when present in conventional treatment processes like chlorination, carcinogenic by-products like trihalomethane and haloacetic acid are formed. This, in addition to the demand for clean potable drinking water, has sparked extensive research into alternative processes for the production of drinking water from various natural/industrial sources. One of the major areas of focus in these studies is the use of membranes in microfiltration, ultrafiltration and nanofiltration. In this report the humic acid removal efficiency of ultrafiltration membranes with 3 kDa, 5 kDa and 10 kDa MWCO is examined. The membranes were made of regenerated cellulose and were in the form of cassette providing a 0.1 m² surface area. At first distilled and deionised water, known as milliQ water, was used as the background feed solution to which humic acid powder was added. It was found that all three membranes removed humic acid with an efficiency of approx. 90% and were capable of reducing initial concentrations of 15mg/L to below the New Zealand regulatory limit of 1.17 mg/L. The permeate flux at a transmembrane pressure of 2.1 bar was approx. 20 l/m²/h (LMH) and 40 LMH, respectively through the membranes with MWCO 3 kDa and 5 kDa. These membranes experienced significant surface fouling resulting in retentate flow rates as low as 11 litres per hour after just four runs compared to the recommended 60–90 l/h. Cleaning with 0.1 M NaOH slightly improved the retentate flow rate, but well below those obtained with fresh membranes. The 10 kDa membrane provided high retentate flow rates which evidently minimised fouling by providing a good sweeping action across the membrane surface while maintaining humic acid removal below the regulatory 1.17 mg/L level. The permeate flux through this membrane was initially high (140–180 LMH) and reduced to approx. 100 LMH after 10–12 min of operation. Increasing the initial humic acid feed concentration from 10 mg/L to 50 mg/L did not significantly decrease humic acid removal efficiency although the retentate flow rate was lower at higher concentrations. Finally the tap water was tested as the background solution and treated for the removal of humic acid. The presence of ions and other impurities in the tap water had little effect on humic acid removal. However, the permeate flux through 10 kDa membrane decreased from 100 LMH for milliQ water to 60 LMH for tap water after 20 min of operation.     

Development of a biofilm-MBR for shipboard wastewater treatment: The effect of process configuration

The direct discharge of wastewater from ships is prohibited by the International Maritime Organization, especially discharge of oily bilge water. This study aims to develop a compact onboard integrated wastewater treatment system for all the wastewater streams on ships, including grey water, black water and bilge water, using biofilm-MBR technology. Both dead-end side-stream and recycle side-stream configurations of a biofilm-MBR concept have been investigated. Flat sheet ceramic membranes from KeraNor AS were applied in the membrane filtration unit. A good membrane permeate quality was achieved in each process configuration, with oil concentrations < 5 mg/L. However, the membrane was seriously fouled when the dead-end side-stream configuration was operated with a high filtration unit recovery (93%). A significantly improved membrane performance, and better permeate quality, was achieved by recycling the concentrate solution back to the biofilm reactor due to better bio-flocculation and biodegradation of oil compounds in the process. The effect of process configuration was investigated by comparing oil concentration, SMP, TSS, FCOD, TCOD, PSD of the concentrate solutions around the membrane in filtration unit. The membrane fouling rate was found to be directly related to oil concentration and oily biomass characteristics in the membrane filtration unit.     

海上油田注水纳滤软化中试研究

针对海上油田回注驱油工艺中的海水软化问题,以胶州湾某海域海水为例,采用超滤-纳滤技术进行了中试规模的海水软化研究。考察了操作压力对两种型号（NF-A、NF-B）纳滤膜软化性能的影响,以及回收率为70%时的水质情况及其与地层水的配伍性,并对NF-A型纳滤膜进行了长期运行稳定性实验。结果表明NF-A型纳滤膜软化水能够与某海上油田地层水配伍,超滤-纳滤集成膜技术能长期、稳定地为海上油田提供软化水。     

Pilot plant study of an ultrafiltration membrane system fordrinking water treatment operated in the feed-and-bleed mode

A pilot plant study of a polysulfone ultrafiltration (MWCO of 30 kD) tubular membrane process was conducted for the treatment of reservoir water. The membrane separation system was operated in the cross-flow filtration mode at 4.7 m/s and the feed-and-bleed mode for a long term of 4000 h without chemical cleaning and backwashing. The results showed that the behavior of permeate flux of the membrane system operated in the feed-and-bleed mode was similar to that of membrane systems with a periodic backwashing. At the beginning of filtration, bleeding of highly concentrated retentate caused a significant increase in permeate flux by 20%. However, as filtration progressed over time, the permeate flux of the fouled membrane was almost independent of the change in concentration of retained materials by bleeding the retentate. Three distinct stages in permeate flux decline were observed as follows: (1) sharp decrease from 120 to 30 1/m²/h in 1250 h due to a rapid build-up of a fouling layer, (2) gradual decrease to 15 1/m²/h in 2800 h due to the role of tangential shear induced by cross-flow velocity, and (3) stable permeate flux until 4000 h due to the establishment of a pseudo-steady-state condition. Permeate quality was stable, regardless of concentrating and diluting retentate in each cycle and fouling for a long duration of filtration. Rejection efficiencies for ultraviolet absorbance at 260 nm (UV₂₆₀) and dissolved organic carbon (DOC) were around 58% and 49%, respectively. The measured turbidity and concentration of suspended solids in bleed water agreed with calculated values from a simple mass valance, while the measured DOC and UV₂₆₀ of bleed water were much lower than calculated values.     

Separation of phenol–water mixture by membrane pervaporation using polyimide membranes

Separation of components of aqueous waste streams containing organic pollutants is not only industrially very important but also is a challenging process. In this study, separation of a phenol–water mixture was carried out by using a membrane pervaporation technique with indigenously developed polyimide membranes. The membranes were found to permeate water selectively. The total flux as well as that of the individual components were measured. The effect of lithium chloride modification of polyimide film on total flux was investigated. The total flux obtained with 2% lithium chloride modification was about 3.6 times higher than that obtained with virgin membrane. The effects of different parameters such as feed composition and temperature on flux, and separation factor were determined. With modified membrane, a separation factor as high as 18.0 was obtained for water at 27°C and with 8.0 wt % phenol solution. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 822–829, 2002     

基于多巴胺亲水改性下Janus膜的制备及其油水乳液分离

目前用于处理含油废水的特殊润湿材料通常分为去油型和去水型,其仅局限分离单一乳液。本文基于多巴胺改性的聚偏氟乙烯（PVDF）膜,通过交替浸渍工艺和无纺布剥离,制备了具有不对称润湿性的Janus膜。通过调整交替次数以及剥离无纺布,可分别获得超亲水/水下超疏油的表面以及超疏水/超亲油的底面,水/水下油接触角（CA）差异高达150°。基于Janus膜的非对称润湿性,仅通过切换跨膜方向,对表面活性剂稳定的水包油（O/W）和油包水（W/O）乳液渗透通量高达367L/(m²·h)和1729L/(m²·h),其中水包油渗透液化学需氧量（COD）符合石油化工排放标准,油包水渗透液中水含量小于80mg/L,实现了对O/W和W/O乳液的高效分离。此外,Janus膜在牛血清蛋白（BSA）溶液分离过程中表现出理想的防污性能和可重复使用性。     

Membrane fouling and chemical cleaning in water recycling applications

Fouling and subsequent chemical cleaning are two important issues for sustainable operation of nanofiltration (NF) membranes in water treatment and reuse applications. Fouling strongly depends on the feed water quality, especially the nature of the foulants and ionic composition of the feed water. Consequently, appropriate selection of the chemical cleaning solutions can be seen as a critical factor for effective fouling control. In this study, membrane fouling and chemical cleaning under condition typical to that in water recycling applications were investigated. Fouling conditions were achieved over approximately 18 h with foulant cocktails containing five model foulants namely humic acids, bovine serum albumin, sodium alginate, and two silica colloids in a background electrolyte solution. These model foulants were selected to represent four distinctive modes of fouling: humic acid, protein, polysaccharide, and colloidal fouling. Three chemical cleaning solutions (alkaline solution at pH 11, sodium dodecyl sulphate (SDS), and a combination of both) were evaluated for permeate flux recovery efficiency. The results indicated that with the same mass of foulant, organic fouling was considerably more severe as compared to colloidal fouling. While organic fouling caused a considerable increase in the membrane surface hydrophobicity as indicated by contact angle measurement, hydrophobicity of silica colloidal fouled membrane remained almost the same. Furthermore, a mechanistic correlation amongst cleaning efficiency, characteristics of the model foulants, and the cleaning reagents could be established. Chemical cleaning of all organically fouled membranes by a 10 mM SDS solution particularly at pH 11 resulted in good flux recovery. However, notable flux decline after SDS cleaning of organically fouled membranes was observed indicating that SDS was effective at breaking the organic foulant—Ca²⁺ complex but was not able to effectively dissolve and completely remove these organic foulants. Although a lower permeate flux recovery was obtained with a caustic solution (pH 11) in the absence of SDS, the permeate flux after cleaning was stable. In contrast, the chemical cleaning solutions used in this study showed low effectiveness against colloidal fouling. It is also interesting to note that membrane fouling and chemical cleaning could permanently alter the hydrophobicity of the membrane surface.     

Synthesis of graft copolymeric membranes of poly(vinyl alcohol) and polyacrylamide for the pervaporation separation of water/acetic acid mixtures

Graft copolymers of poly(vinyl alcohol) (PVA) with polyacrylamide were prepared and membranes were fabricated at 48 and 93% grafting of acrylamide onto PVA. These membranes were used in the pervaporation separation of water/acetic acid mixtures at 25, 35, and 45°C. The permeation flux, separation selectivity, diffusion coefficient, and permeate concentration were determined. The highest separation selectivity of 23 for neat PVA at 25°C and the lowest value of 2.2 for 93% acrylamide‐grafted PVA membranes were observed. A permeation flux of 1.94 kg m^?2 h^?1 was found for the 93% grafted membrane at 90 mass % of water in the feed mixture. The diffusion coefficients in a water/acetic acid mixture had an effect on the membrane permselectivity. The Arrhenius equation was used to calculate the activation parameters for permeation as well as for the diffusion of water and of acetic acid. The activation energy values for the permeation flux varied from 97 to 28 kJ/mol. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 244–258, 2002     

Evaluation of the fouling potential of ceramic membrane configurations designed for the treatment of oilfield produced water

During the treatment of oilfield produced water (PW) with ceramic membranes, process efficiency is primarily characterized by the specific permeate flux and the oil separation performance. In addition to membrane properties, the increase in total filtration resistance (fouling) and the decline in permeate flux are strongly dependent on the constituents of the PW as well as process conditions such as trans-membrane pressure and cross-flow velocity. The extensive study presented herein describes the characterization, application and performance of various ceramic membrane filtration technologies designed and developed for the efficient treatment of PW generated from tank dewatering and several oily model systems.     

Fouling characteristics of an ultrafiltration membrane used in drinking water treatment

The fouling characteristics of ultrafiltration membranes used in drinking water were investigated when used alone and when used in an integrated biofilter-membrane system to treat a humic-acid laden solution. Membrane strands from sacrificial modules operating in parallel with bench-scale modules were analysed from both systems (with and without pretreatment). Chemical and microbiological analyses were performed on these strands together with different process streams along the treatment train. Microscopic observations performed on the sacrificial membrane strands revealed that most of the fouling material was organic in nature with high numbers of viable microorganisms. When comparing their fouling characteristics, a positive effect from the biofilter was observed on the performance of the membrane with pretreatment, decreasing in general the amount of material deposited and reducing the fouling rate. Membranes were tested at two different permeate fluxes; this variable did not have an effect on the overall amount of material deposited, but it significantly impacted the membrane fouling rate.