Reverse Osmosis Membrane Modules Research Articles

Reliable Sea Water Ro Operation with High Water Recovery and No-Chlorine/No-Sbs Dosing in Arabian Gulf, Saudi Arabia.

For providing advanced desalination the combination of the improvement of water recovery ratio in the reverse osmosis (RO) process and the No-Chlorine/No-Sodium Bisulfite (SBS) Dosing process was studied. In order to prevent membrane fouling even in high recovery water operations, an advanced two-stage design was implemented to (1) control the permeate flux through the RO membrane module, (2) optimize the system to reduce contaminant build-up and (3) eliminate the use of chlorine and SBS, which can accelerate membrane fouling. The system was evaluated by monitoring the biofouling and the microorganisms proliferation on the membrane surface based on membrane biofilm formation rate (mBFR). The pilot plant was operated in the condition of a water recovery rate of 55%. As a result, the system was operated for longer than four months without membrane cleaning (clean in place; CIP) and the possibility of operation for seven months without CIP was confirmed by the extrapolation of the pressure values. In addition, the mBFR is a reliable tool for water quality assessment, based on a comparison between the fouling tendency estimated from the mBFR and the actual membrane surface condition from autopsy study and the effectiveness No-Chlorine/No-SBS Dosing process was verified from mBFR of pretreated seawater.

The separation of radionuclides and silicon from boron-containing radioactive wastewater with modified reverse osmosis membranes

The ability to reuse boron and minimize the volume of radioactive waste could be accomplished with modified reverse osmosis (RO) membranes. RO membranes were fabricated via polyethylenimine (PEI) grafting to separate silicon and radionuclides from boron-containing radioactive wastewater. The positively charged RO membrane promoted more efficient removal of nuclides and silicon while the rejection of boron declined from 55.88 % to 41.71 % after modification. Compared with virgin RO membrane, the SFB-Si, SFB-Cs, and SFB-Co of the modified RO membranes increased from 6.02, 5.16, and 12.62–29.52, 61.91, and 547.15, respectively. SFB-Si, SFB-Cs, and SFB-Co of the simulated RO system with modified RO membranes further increased to 156.96, 1068.12, and 83617.88, respectively. As a result, permeate water with 433.92mgL−1 boron, 0.04mgL−1 silicon, 1.62μg·L−1 Cs(I), and 0.02μg·L−1 Co(II) was obtained, which could satisfy radionuclide treatment requirements and allow for the reuse of boron. Overall, modified RO membranes would be able to reuse boron and minimize the volume of discharge of radioactive wastewater.

Pomegranate juice concentration through the consecutive application of a plasma modified reverse osmosis membrane and a membrane contactor

A low-pressure nitrogen plasma (LPNP) modified commercial thin-film composite membrane was used for pre-concentration of the clarified pomegranate juice (C-PJ) by reverse osmosis (RO). Pre-concentrates then submitted to osmotic distillation (OD) for further concentration. The productivity of the integrated membrane process was benchmarked considering both the performance and the final product quality. The modified RO membranes had great potential for shortening duration of consecutive concentration process, enabling up to 36% time saving during concentration of the C-PJ from 15.6°Brix to >65°Brix. Aroma losses observed in stand-alone OD are also prevented by shortening the duration of OD. Lower retention of malic acid, gallic acid, glucose, and fructose was observed due to the increased permeability following LPNP modification. However, these losses did not seem to affect the total acidity, total phenolic content, and total antioxidant activity of the concentrates obtained. The total color change was also in the range of barely noticeable values.

Evaluation of a new air water generator based on absorption and reverse osmosis

The evaluation of a new air water generator (AWG) based on absorption and reverse osmosis is described. For the evaluation, an aqueous lithium bromide solution has been selected from a wide range of liquids as the absorbent. At high salt mass fractions, the aqueous lithium bromide solution has a low vapour pressure and a high osmotic pressure. The low vapour pressure ensures that the water vapour can be absorbed from the air, but the high osmotic pressure leads to high pressures over the membrane. Due to the high osmotic pressures, several reverse osmosis membrane modules are necessary and salt solution has to be present on both sides of the membrane, which leads to an additional inlet on the permeate side. Models for the absorber, the reverse osmosis membrane module and the complete multi-stage reverse osmosis system have been developed in Python. The model of the complete system has then been used to simulate the performance of the AWG at different boundary conditions. The simulations have shown that based on the defined assumptions, extracting water from the air with absorption and reverse osmosis is possible and that the energy demand per litre of pure water is similar to AWG systems which use condensation.

Impacts of non-uniform filament feed spacers characteristics on the hydraulic and anti-fouling performances in the spacer-filled membrane channels: Experiment and numerical simulation

Feed spacer is universally used in spiral-wound nanofiltration (NF) and reverse osmosis (RO) membrane modules. It can separate membrane sheets, create flow channels, promote turbulence and enhance mass transfer. However, it also induces increased pressure drop across the flow channel, and generates dead zones for biofilm growth at specific locations. Optimization of feed spacer geometries is highly desirable for energy saving and biofouling control. In this study, four kinds of commercial feed spacers featured with non-uniform filaments were compared in terms of hydraulic and anti-fouling performances. Computational fluid dynamics (CFD) simulations were launched to give insights into the impacts of feed spacer characteristics on the flow field. Results show that the hydraulic performance was substantially affected by the number of filament layers (single or dual layer), the non-uniformity of filament diameter and the width of thinning zones. The design of single layer feed spacer of non-uniform filaments was not recommended due to high flow resistance and poor anti-fouling performance. The feed spacer structure of alternating filament diameter contributed to reducing dead zones and alleviating membrane fouling. The thinning zones located adjacent to the filament junctions achieved better anti-fouling performance, as it disturbed the dead zones and partially washed away the deposited foulants. This study demonstrates for the first time that the characteristics of non-uniform filament feed spacer had a crucial impact on the hydraulic and anti-fouling performances, and suggests that more emphasis should be laid on number of filament layers, variation of filament diameter and width and positioning of thinning zones for the optimization of feed spacer geometries in the future.

The influence of membrane surface properties on the radionuclide mass transfer process in reverse osmosis

Reverse osmosis (RO) technology has been playing an increasingly important role in radioactive wastewater treatment. In this study, the influence of membrane surface properties on the trace radionuclide (Cs+) mass transfer process in polyamide RO membrane was investigated. The Cs+ mass transfer process was described using the solute permeability coefficient (B) with the solution-diffusion with defects (SDWD) model. Several modified RO membranes grafted by different polymers were fabricated to provide different properties, including surface charge, surface roughness and hydrophilicity. The results of correlation analyses demonstrated that BCs+ was independent of both the membrane hydrophilicity and surface roughness. In contrast, there was a significant correlation between BCs+ and the membrane surface charge. The zeta potential exhibited a strong correlation with BCs+. BCs+ decreased from (7.78 ± 0.70) × 10−7 to (7.19 ± 2.95) × 10−9 m/s as the zeta potential increased from −43.57 to 21.2 mV. The results of this study indicated that the membrane surface charge of RO membrane played a key role in the radionuclide mass transfer process. Fabricating positively charged RO membranes could significantly obstruct the radionuclide mass transfer process. The results provided fundamental insights into the mechanisms of the radionuclide mass transfer process in the RO membrane, which emphasized the application prospects of membrane surface modification as a method for the treatment of radioactive wastewater.

Radioactive wastewater treatment with modified aromatic polyamide reverse osmosis membranes via quaternary ammonium cation grafting

With the growing application of nuclear power, development of methods for the treatment of radioactive wastewater has become increasingly important. In this study, a positively charged aromatic polyamide reverse osmosis (RO) membrane was prepared using a quaternary ammonium salt (2, 3-epoxypropyltrimethylammonium chloride, EPTAC) grafting to improve nuclide removal efficiency. After modification, the zeta potential of the RO membrane surface increased from −22.89 mV to 21.20 mV in neutral conditions. The positively charged RO membrane promoted more efficient removal of nuclides when compared with the original RO membrane. The decontamination factor (DF) of cesium (I) increased from 11.69 to 151.12 and the DF of cobalt (II) increased from 28.62 to 1670.84. In addition, the surface properties of the modified RO membrane were measured, including hydrophilicity, chemical elements, and morphology. The results of these analyses demonstrated that the hydrophilicity of the membrane was significantly improved as the water contact angle decreased from 65° to 10°. The analysis also demonstrated that the EPTAC-modified RO membrane had a stable nuclide DF under different pH conditions. A brief comparison of the DF of nuclides between commercial RO membranes and modified membranes demonstrated a potential application of EPTAC-modified RO membranes for the treatment of radioactive wastewater from nuclear power plants.

Nanoscale polyelectrolyte/metal ion hydrogel modified RO membrane with dual anti-fouling mechanism and superhigh transport property

The anti-fouling polyamide (PA) reverse osmosis (RO) membranes modified by hydrophilic polymer are trapped in the problems of declined flux, single anti-fouling mechanism, high cost or complex fabrication. Here the nano-sized sodium alginate/Cu2+ hydrogel prepared with the layer-by-layer (LBL) method was firstly applied for PA RO membrane modification to solve these contradictions. The combination of passive and active antifouling capabilities can be imparted by the polyelectrolyte hydrogel cross-linked with metal ions. In addition, remarkable transport properties can be achieved by brilliant hydrophilicity of hydrogel layer and LBL method which can control the thickness of the modified layer at nanometer level to minimize the transmembrane resistance of water molecules. The modified membrane possesses a water flux of 71.40 LMH up to 192.97% of the unmodified membrane without sacrificing salt rejection at 25 °C, 1.6 MPa. In the BSA and DTAB fouling tests, the flux recovery rate of the modified membrane was 26.44% and 29.14% greater than that of the unmodified membrane, respectively. Moreover, the modified PA membrane exhibited great bactericidal potential to S. aureus and E. coli. Besides prominent comprehensive performance, this strategy is low cost and simple in operation, shining a light on preparing new generation of high-performance RO membrane.

Functionalization of reverse osmosis membrane with graphene oxide and polyacrylic acid to control biofouling and mineral scaling

The polyamide reverse osmosis (RO) membrane was modified with graphene oxide (GO), followed by polymerization of acrylic acid (used as an antiscalant) for the reduction of both biofouling and mineral scaling. After functionalization, the water contact angle reduced from 41.7 ± 4.5° for unmodified RO membrane to 24.4 ± 1.3° for the modified RO membranes, which showed that membrane hydrophilicity was significantly enhanced, in addition to the improvement in surface smoothness. The modified membranes were tested for their anti-scaling and anti-biofouling characteristics. When the mineral scaling test was performed using CaSO4 solution as feedwater, the permeate flux was reduced by only 3% as compared to the unmodified RO membrane which encountered up to 22% decline in flux by the end of the experiment. After the scaling test, the membrane surface was characterized by Scanning electron microscopy – energy-dispersive X-ray spectroscopy, Fourier transform infrared, and X-ray diffraction techniques. The results showed that the unmodified RO membrane was fully covered with gypsum precipitates. Whereas, the precipitates were detected only at the highly saturated zones of the water channel i.e. towards the exit of water flow. Additionally, the anti-bacterial test was performed through bacteriostasis rate determination, which showed that the modified membranes inhibited the growth of nearly 95% of the bacterial cells. Further experiments were also performed to investigate the inhibition of both scaling and biofouling by modified RO membranes. Thus, it was found that the polymer-modified GO coated RO membranes were able to diminish both gypsum scaling and biofilm formation demonstrating their potential to control different types of membrane fouling.

Metagenomic Insight Towards Vanillin-Mediated Membrane Biofouling Prevention: In Silico Docking Validation.

Biofouling leads to water quality deterioration and higher maintenance cost for cleaning of membranes. The present study has demonstrated the application of a biomolecule (vanillin) in scrubbing and destabilizing biofilms of drinking water reverse osmosis (RO) membrane module in lab scale reactor set-up. Reverse osmosis membrane reactor was connected with tap water supply and subjected with optimal concentration of vanillin. The pressure drop was delayed by 17-20days as compared to control reactor. Real-time PCR analysis of metagenome indicated the reduced copy number of functional biofilm-associated genes (bdlA, lasI, pgaC) in treated membrane. SEM and metagenome analysis revealed that the sticky biofilm communities shifted to loosely bound emboli after vanillin treatment. Metagenome sequence analysis revealed the inhibitory activity against major biofouling biota like members of Proteobacteria, Acidobacteria, Acnitobacteria, Bacteroidetes, Candidatus, Nitrospira, and Firmicutes. Biofouled membrane metagenome sequence was also compared with real-life (brackish water, waste water, domestic drinking water) biofouled membrane communities. In silico docking of vanillin to receptor proteins and chemical configuration simulation along with other phenolic derivatives were performed, which suggested that the autoiducer signal capability of vanillin was effective against representative broad spectrum biofilm population. Vanillin exhibited the quorum-quenching mode of action by virtue of docking towards similar amino acid (Thr 131, Ilu 214) responsible of autoinducer signal anchoring in the transcriptional regulatory proteins.

Fouling behavior of marine organic matter in reverse osmosis membranes of a real-scale seawater desalination plant in South Korea

The effects of marine organic matter (MOM) characteristics on the fouling layer composition of seven parallelly arranged reverse osmosis (RO) membrane modules were identified to offer valuable insights into the fouling behavior of MOM in a real-scale seawater desalination plant in the South Korea region. Although both hydrophobic (HPO) and hydrophilic (HPI) MOM fractions governed the fouling formation of the RO membranes, HPO MOM fractions complexed with multivalent metal ions (i.e., Al, Ca, Cu, Fe, and Mg) were found to be major contributors to the irreversible fouling of the RO membranes. Despite the efficient recovery of the negative surface zeta potential after the cleaning procedures with deionized water, base and acid solutions, the contact angle of the fouled RO membrane was reduced significantly, which was more pronounced for the cleaned RO1st membranes than the cleaned RO7th membranes. HPI MOM fractions were preferentially deposited onto the membrane surfaces in the RO1st module, while residual HPO MOM fractions strongly contributed to the fouling formation of the RO membranes in the RO7th module. These phenomena might lead to significant differences in the fouling layer composition of the RO membrane modules in the real-scale seawater desalination plant in the South Korea region.

Structure regulation for synergistically improving the permeation properties of the reverse osmosis membrane based on an amphiphilic hyperbranched polymer

The aromatic polyamide (PA) thin film composite (TFC) reverse osmosis (RO) membrane has been widely used in the desalination processes to settle the global water crisis. To further decrease the desalination cost, in this work, an amphiphilic hyperbranched polymer of HBPO-star-PEO-COCl with abundant end groups of acyl chloride and core-shell hydrophilic/hydrophobic phase separation structure was synthesized and used as the functional nanomaterial to modify the conventional polyamide TFC RO membrane through interfacial crosslinking reaction. The modified RO membrane with 0.005% HBPO-star-PEO-COCl presents the optimal structure and permeation properties. Its PA layer becomes thinner and denser, and its water flux reaches 69.8LMH nearly double that of the original membrane (33.27LMH), at the same time, its NaCl rejection rate reaches 99.22% higher than that of the original membrane. It can attribute to the unique amphiphilic core-shell structure of HBPO-star-PEO-COCl. On the one hand, the PEO shell of HBPO-star-PEO-COCl is highly hydrophilic while the internal HBPO is highly hydrophobic and collapses easily in water to form a three-dimensional quasi-spherical structure, which leads to the formation of the core-shell two-phase interface, thereby facilitating the water molecules to rapidly pass through the PA layer along the hydrophobic wall surface. On the other hand, the end acly chloride groups of HBPO-star-PEO-COCl take part in the crosslinking reaction, which makes the PA layer have higher crosslinking degree and become denser, thereby enhancing the salt retention. Therefore, this study provides an effective way to fabricate a new reverse osmosis composite membrane with favorable comprehensive separation performance based on amphiphilic hyperbranched polymer.

A seawater RO desalination process driven by dynamic pressure of high-speed seawater droplets

Seawater reverse osmosis (RO) desalination requires driving pressure of 5~8 MPa which is usually offered by the high-pressure pump, the standard device employed in the commercial application, accompanied by a series of problems. To replace the high-pressure pump, a seawater RO desalination technique driven by the dynamic pressure of high-speed seawater droplets is proposed. By theoretical calculation and computational fluid dynamic (CFD) simulation, the required operating conditions for the acquisition of effective impacting seawater droplets were investigated. The results showed that the velocity of the seawater droplets should exceed 70 m/s to achieve the driving pressure of 5 MPa, and simultaneously the air flow velocity should exceed 70 m/s to act as the accelerating medium. The proper size of the accelerated droplets at different air flow velocity within the range of 70~100 m/s was determined not only considering the final velocity of the droplets but also their gravitational settling limitation. In addition, five structures of the RO membrane module were designed and tested, in which the ring-shaped and semicircle-shaped structure exhibited good performance with droplet trap rate greater than 90%. Furthermore, the energy balance of the whole system was analysed, and some constructive suggestions are provided to reduce the energy consumption.

A seawater RO desalination process driven by dynamic pressure of high-speed seawater droplets

Seawater reverse osmosis (RO) desalination requires driving pressure of 5~8 MPa which is usually offered by the high-pressure pump, the standard device employed in the commercial application, accompanied by a series of problems. To replace the high-pressure pump, a seawater RO desalination technique driven by the dynamic pressure of high-speed seawater droplets is proposed. By theoretical calculation and computational fluid dynamic (CFD) simulation, the required operating conditions for the acquisition of effective impacting seawater droplets were investigated. The results showed that the velocity of the seawater droplets should exceed 70 m/s to achieve the driving pressure of 5 MPa, and simultaneously the air flow velocity should exceed 70 m/s to act as the accelerating medium. The proper size of the accelerated droplets at different air flow velocity within the range of 70~100 m/s was determined not only considering the final velocity of the droplets but also their gravitational settling limitation. In addition, five structures of the RO membrane module were designed and tested, in which the ring-shaped and semicircle-shaped structure exhibited good performance with droplet trap rate greater than 90%. Furthermore, the energy balance of the whole system was analysed, and some constructive suggestions are provided to reduce the energy consumption.

Optimization of Recycled-Membrane Biofilm Reactor (R-MBfR) as a sustainable biological treatment for microcystins removal

This work aims to investigate optimization while running a Recycled-Membrane Biofilm Reactor as a sustainable biological treatment for microcystins (MC) removal. For this purpose, coupons from an end-of-life seawater reverse osmosis (RO) membrane module were extracted and conditioned. The MC-degrading biofilm formation on this recycled membrane surface was carried out in a simulator cell on the laboratory scale to study the influence of air supply in this step. Firstly, the main results obtained in this work are related to the biofilm formation. Confocal laser scanning microscope (CLSM) demonstrated that air supply provide a higher biomass, maximum thickness and lower roughness coefficient. Secondly, the air supply also stimulated the MC removal by shortening the lag phase and increasing the MC degradation rate. Finally, the developed biofilm with air supply also was able to efficiently remove MC from two different types of polluted water, surface natural water (SNW) and synthetic reclaimed water (SRW). These results support the R-MBfR technology for treating MC-polluted water that could be used for different application, especially in nutrient-rich water. Therefore, this study addresses the lack of sustainable technologies for water treatment, while opening an alternative in sustainable solid waste management under a circular economy approach.

An analysis of the effects of pressure-assisted osmotic backwashing on the high recovery reverse osmosis system

AbstractThe low cost simplified method for implementation of pressure-assisted osmotic (PAO) backwash (BW) for spiral wound reverse osmosis (RO) membrane module is presented in this work. The effect of membrane design and an operating parameter concerning the efficiency of PAO membrane BW is analyzed. The following design and operating parameters are considered in this study: (i) spacer thickness, (ii) dimension of the permeate channel, (iii) number of leaves, and (iv) BW water pressure. The performance of PAO BW with respect to membrane cleaning efficiency is analyzed for three different high recovery RO systems by purifying 1,500 liters of water. The membrane cleaning efficiency is measured by examining the rate of permeate quality and quantity decline using ASTM D4516 method. Finally, to quantify the membrane fouling with respect to different high recovery configurations, the thickness, and composition of foulants present in the used membrane's surface are measured by using field emission scanning electron microscope with energy dispersive X-ray (FESEM-EDX). The result concludes that the RO membrane operated at high recovery with PAO BW is found to have less fouling deposits than membrane without PAO BW.

Synthesis of surface-anchored stable zwitterionic films for inhibition of biofouling

The article reports a two-step method for the synthesis of antifouling films; wherein we first deposited the copolymer films of poly(4-vinylpyridine-co-ethylene glycol diacrylate) (p-4VP-co-EGDA) onto the surface of different substrates (e.g., delicate substrate such as reverse osmosis (RO) membranes, Si wafers and gold sensors) via an all-dry and substrate-independent technique known as initiated chemical vapor deposition (iCVD). The iCVD technique is based upon free radical polymerization where vapors of initiator and monomers are transported to the surface to be modified to initiate simultaneous polymerization and thin film formation. In a subsequent step, th as-deposited copolymer films were converted to zwitterions by a diffusion limited gas-phase reaction with vapors of 1,3-propane sultone to form polysulfobetaine (pSB) type of zwitterionic surface moieties. Bare and the surface modified substrates were characterized by AFM, FTIR and XPS for their topographical and compositional analysis. The presence of zwitterionic moieties considerably discourages the irreversible attachment/adhesion of proteins and bacterial cells as demonstrated by quartz crystal microbalance with dissipation monitoring (QCM-D) and SEM analysis respectively. The results of bacterial adhesion studies showed 99.6% lower attachment of Pseudomonas aeruginosa cells onto the surface of modified RO membranes as compared to bare membranes. The authors wish to mention that a new pyridine-based pSB type of antifouling zwitterionic films has been added to the library of iCVD films. We believe that the demonstrated attempt of membrane surface modification strategy holds promise for potentially controlling the biofouling of other polymeric membranes such as ultrafiltration, nanofiltration and RO membranes. Furthermore, salient features such as solvent less nature, the easy tunablity of film and the capability of retention of functional group make iCVD a unique method to modify the surface of virtually any substrate including, metals, polymeric membranes, Si and gold sensors etc. Thus, it is expected that the developed coating technique could possibly lead to prepare a wide spectrum of environmentally benign antifouling films for other applications such as biomedical devices, medical implants and ship hulls where inhibition of microbial adhesion and subsequent biofilm growth is a severe challenge.

Assessing the passage of particles through polyamide reverse osmosis membranes

The safety of recycled water for potable water reuse can be enhanced by improving the removal of pathogenic microorganisms through reverse osmosis (RO) membrane. The present study aimed to identify the causes of the passage of particles through intact RO membrane elements using stable 0.5 µm fluorescent (FL) microspheres as bacteria-sized surrogates. Pilot-scale tests revealed that the removal of FL particles varied between 1.6 and 6.1-log among seven commercial RO membrane modules, and a less permeable RO membrane had a higher efficiency for removing bacteria-sized particles. To clarify the causes of particles passing through the tight RO membrane, further investigations were performed focusing on the following three types of membranes based on the RO membrane manufacturing process: an ultrafiltration membrane (the supporting layer of RO membrane), and RO membranes obtained before assembly and after disassembly of their membrane elements. The highest concentrations of FL particles in permeate were obtained in the disassembled RO membranes, suggesting that the commercial spiral wound membrane elements may have lesser integrity than the intact RO membrane sheets for removal of bacteria-sized particles. However, the conductivity removal of the two types of RO membranes was equivalent regardless of the assembly process; thus, typical performance tests could not identify the membrane integrity breach for particle removal. To the best of our knowledge, this is the first study to report that the integrity of the RO membrane for particle removal may be compromised after assembling its spiral wound membrane element.

Impact of membrane biofouling in the sequential development of performance indicators: Feed channel pressure drop, permeability, and salt rejection

Biofouling development is affected by a variety of factors that change over the length of reverse osmosis (RO) membrane modules in pressure vessels. Spatially resolved biofouling formation was studied under conditions representative to practice using four one-meter Long Channel Membrane Test Cells (LCMTCs) in series, simulating an industrial pressure vessel.Biofouling was induced by dosing an easily assimilable substrate to the feed water. The impact of biofouling on the sequential decline of RO membrane performance indicators (feed channel pressure drop, permeability and salt rejection) was investigated. Also, the temporal organic carbon (DOC) consumption was assessed spatially over the four test cells.Results showed that all membrane performance indicators were impacted by biofouling formation. The feed channel pressure (FCP) drop increase was impacted earliest and strongest followed by permeability and salt rejection decline, underlining that FCP drop is a sensitive and early biofouling monitoring indicator. Spatially resolved biofouling investigations revealed that most biofouling was formed in the lead sections of membrane installation with a decreasing gradient over length, linked to DOC availability in the system. In this study, FCP drop played a crucial role: the FCP drop increase at the lead test cell of the membrane installation caused performance losses for the downstream test cells.Minimizing the effect of biofouling on membrane performance should be pursued by a combination of strategies involving (i) early detection and preventive cleaning, (ii) substrate limitation for delaying biofouling built-up and (iii) optimized (early) cleaning procedures for more effective biofilm removal.

Improved fouling resistance for RO membranes by a surface modification method

We investigated the surface modification of reverse osmosis (RO) membranes to enhance fouling resistance. RO membranes were modified via a sol–gel process using aminopropyltrimethoxysilane (APTMS), chlorotrimethoxysilane (CTMS) and mercaptopropyltrimethoxysilane (MPTMS). The fouling test showed that the flux of the pristine decreased continuously from 52.3 to 20 GFD, whereas APTMS-RO, CTMS-RO and MPTMS-RO were maintained about 37, 25, and 13 GFD, respectively. Salt rejection was maintained over 97.4%. The FRR values of pristine, APTMS-RO, CTMS-RO, and MPTMS-RO were 75.5, 98, 92.2, 88.3%, after chemical cleaning process. As a result, the modified RO membranes have excellent antifouling properties after 3-cycles chemical cleaning.