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Reverse osmosis (RO) is increasingly becoming the dominant strategy for seawater desalination owing to its excellent desalination performance over the past few decades. It produces a considerable amount of concentrated brine, which is a threat to marine ecosystems accompanying freshwater production. Electrodialysis has been demonstrated to be a feasible process for brine treatment. In this work, a novel process called Selectrodialysis with Bipolar Membranes (BMSED) was firstly proposed for treating concentrated brine. BMSED uses bipolar membranes and monovalent selective ion exchange membranes inside the ED stack and thus combines the selectrodialysis (SED) and bipolar membrane electrodialysis (BMED) processes into a single step. BMSED can desalinate concentrated brine, selectively regenerate monovalent ions and produce acids/bases in a single route. The feasibility of the process was investigated by using different commercial membranes. The factors, including the current density and brine concentrations, were investigated. The results indicated that brine was successfully treated by using BMSED and that a HCl and NaOH solution (up to an approximate 2 mol/L concentration) with high purity was eventually produced. Therefore, BMSED is a pertinent environmentally and economically friendly process for RO concentrated brine management. [ABSTRACT FROM AUTHOR]

Although pristine graphene oxide (GO)-based membranes have previously demonstrated promising molecular separation due to their well-defined interlayer spacing, their applications in water processing operations remain limited due to the natural swelling tendency of GO in the aqueous phase which decreases separation ability. In this work, pristine GO laminate has been successfully integrated into a highly crosslinked network to produce membranes with anti-swelling behaviour and excellent desalination capability. The process of free-radical polymerisation in aqueous conditions of a GO suspension enables the formation of a GO-polymer network without covalent bonding between GO and polymer, leading to a combination of mechanical robustness, remarkable water transport properties, and an anti-swelling tendency suitable for the high-pressure operation required for reverse osmosis (RO) membrane process. The resulting GO-polymer membrane was not swollen during RO operation while it was stable under a harsh oxidising environment. It also demonstrated water flux of 33.5 L m −2 h −1 with 98.5% NaCl rejection at 10 bar when prepared by high-vacuum filtration and subsequent polymerisation of the precursor solution on to a mesoporous substrate. This methodology makes large-scalable membrane fabrication very feasible. [ABSTRACT FROM AUTHOR]

In this study, the influence of reverse draw solute permeation on the rejection and prediction of NO 3 − and NH 4 + by forward osmosis (FO) were investigated. The rejection of NO 3 − and NH 4 + were experimentally compared between FO mode (active layer facing the feed water) and RO mode (hydraulic pressure applied). Under similar water fluxes, the rejection ratio of NO 3 − by HTI-ES membrane was much higher during RO than it was during FO, while the opposite was true for HTI-TFC membrane. For both membranes, the rejection of NH 4 + was higher during RO than that it was in FO. Rejection was mathematically predicted by using the solution–diffusion model with the permeability obtained from the diffusion cell. The predicted NH 4 + rejection for the HTI-TFC membrane matched well with the experimental rejection ratios. However, the model greatly overestimated the rejection ratios of NO 3 − by HTI-ES membrane and underestimated the rejection of NH 4 + by HTI-ES membrane and NO 3 − by HTI-TFC membrane. The electrostatic equilibrium at the interface and electrostatic gradient across the membrane may differ between RO, FO and diffusion cell mode, which should be considered in future FO models. [ABSTRACT FROM AUTHOR]

An increasing demand for freshwater inspires further understanding of the mechanism of water diffusion in reverse-osmosis membranes for the development of high-performance membranes for desalination. Water diffusion has a close relationship with the structural and dynamical characteristics of hydrogen bonds, which is not well-understood for the confining environment inside the polyamide membrane at the molecular level. In this work, an atomistic model of a highly cross-linked polyamide membrane was built with an equilibrated mixture of m-phenylenediamine and trimesoyl chloride monomers. The structure and dynamics of water in the regions from the bulk phase to the membrane interior were investigated by molecular dynamics simulations. Explicit hydrogen bond criteria were determined for hydrogen-bonding analysis. The local distribution and orientation of water reveal that the hydrogen-bonding affinity of the hydrophilic functional groups of polymers inhibits water diffusion inside the membrane. The affinity helps to produce percolated water channels across the membrane. The hydrogen-bonding structures of water in different regions indicate dehydration is required for the entry of water into the polyamide membrane, which dominates water flux across the membrane. This paper not only deepens the understanding of the structure and dynamics of water confined in the polyamide membrane but also stimulates the future work on high-performance reverse-osmosis membranes. [ABSTRACT FROM AUTHOR]

The most common desalination technology is based on reverse osmosis, which uses semi-permeable membranes and pressures from 5.5 MPa to 6.8 MPa in order to overcome the osmotic pressure. The lowest achievable energy consumption of RO is 2 kWh/m 3 . The other viable methods of desalination include membrane distillation and pervaporation. Each of these techniques has certain advantages and disadvantages but in terms of energy consumption pervaporation seems particularly promising. Over the past few years, desalination performed with the help of pervaporation has been widely investigated. In this study, desalination experiments were carried out with a commercial membrane. The salt concentration and the feed solution temperature were varied between 0.8% and 7.0% and between 40 °C and 70 °C, respectively. The experiments helped determine the desalinated water flux and the salt rejection factor. In addition, differences in enthalpy and Gibbs free energy, representing the theoretical energy consumption, were estimated in the raw water/feed and the feed/permeate systems. For the purpose of comparing the energy consumption, three desalination techniques were considered: RO, PV and MD. [ABSTRACT FROM AUTHOR]

The study presents in situ modification of a spiral-wound seawater reverse osmosis (SWRO) membrane elements using sorption of hydrophobic long-chain aliphatic amine molecules as a generic approach to increasing selectivity, in particular, boron removal. Spiral-wound seawater SW30 elements modified using decylamine and dodecylamine showed 2–4 times lower boron passage for the modified elements at the expense of a moderate drop in permeability. Autopsy indicated no change in surface morphology and chemistry, suggesting immobilization of the modifying molecules within the active layer. Overall, the reported in situ modification of the SWRO element resulted in a superior trade-off between permeability and boron passage and no change in salt rejection, as compared to regular polyamide membranes. The enhanced selectivity toward boron5 removal could potentially help eliminate or reduce the costs related to the second pass in sea water desalination. [ABSTRACT FROM AUTHOR]

The potential of a commercial forward osmosis (FO) module to recover water from NEWater brine, an RO retentate, was assessed by taking an innovative approach to obtaining the mass transfer coefficients. The performance comparison of the spiral wound (S-W) FO module with that of the flat sheet laboratory unit suggests that the winding involved in S-W construction can adversely affect performance; the values for the S-W mass transfer coefficients were half of those expected. This first-of-its-kind performance comparison utilised coupons of the membrane and spacers taken from the module. The module was used both in the conventional manner for FO and in the reverse manner with the active layer facing the draw solution. Estimates of membrane parameters and mass transfer coefficients experiments for the two orientations were obtained using pure water, 10 mM and 25 mM NaCl solution on the feed side and 1 M NaCl as draw solution. The fouling potential of NEWater brine per se was found to be low. These are the first results with a S-W module that suggest potential for this niche application; nevertheless the level of the water flux through the S-W module clearly indicates that industrial applications of S-W FO will be constrained to special cases. [ABSTRACT FROM AUTHOR]

Due to stricter environmental regulations and lack of other alternatives, saline effluents reuse is becoming necessary in arid regions. Produced water generated in oil and gas exploration is a promising stream for this purpose, since remarkable quantities are available. In order to turn desalination routes into economically attractive options, it is mandatory to choose and to optimize technologies aiming to minimize capital and operational costs. Therefore, several combinations of technologies, involving forward osmosis (FO), reverse osmosis (RO), assisted reverse osmosis (ARO), microfiltration (MF), mechanical vapor compression (MVC), and membrane distillation (MD) were simulated and optimized for different reuse destinations. Results indicated MF-RO as the cheapest route for salinities lower than 90 g/L, while FO-RO had the highest cost and could be unfeasible depending on salinity. For higher salt content, MF-ARO-RO was the cheapest alternative, followed by thermal processes (MF-MVC and FO-MVC, respectively). However, applicability of MVC depends on final water quality due to possible volatiles constraints. MF-ARO-RO process, which is a novel technology, was submitted to a retro-techno-economic analysis (RTEA) to investigate its potentialities. Although membrane parameters had minor influence, external parameters as ARO membrane cost, energy cost and interest rate play important roles on process cost. [ABSTRACT FROM AUTHOR]

Biofilm occurrence in reverse osmosis (RO) membranes constitutes a key problem in water plants, leading to a loss of performance and a decrease in treatment efficiency. Knowledge on the microbial community composition and the links to operational conditions is therefore crucial to understand biofilm formation and develop proper biofouling management strategies. The advent of molecular methodologies in the last years has evidenced the failure of culture-dependent techniques to assess the great level of diversity present in RO membranes. More recently, the application of – omics has unveiled a new horizon to study microbial diversity and function in wastewater treatment. This manuscript focuses on the latest discoveries in prokaryotic diversity in RO membranes, highlighting the importance of operating conditions and cleaning strategies in community structure. The current knowledge of biofilm dynamics in these systems is also reviewed. However, despite the enormous possibilities that metagenomics and metatranscriptomics can offer, studies using these methodologies in RO membranes are still scarce, and further efforts to uncover a core microbial composition and expression patterns of relevant genes are still needed. [ABSTRACT FROM AUTHOR]

This work reports the repairing of partially degraded polyamide TFC RO membrane for restored salt rejection and simultaneously enhanced resistance to both chlorine and fouling through adopting an in-situ, simple and upscalable approach of cross-flow filtration of sericin aqueous solution followed by flushing with de-ionized water. The attachment of sericin molecule on membrane surface was confirmed by XPS analysis and was found to be effective in recovering membrane reverse osmosis performance. The membrane with a degraded salt rejection higher than 94.0% exhibited a restored salt rejection the same as or a little higher than that of the new membrane (before chlorination). The deposition of sericin was also found to make membrane surface smoother and more hydrophilic and negatively charged under neutral condition, and thus endow the restored membrane with enhanced fouling resistance to bovine serum albumin compared with the new membrane. Furthermore, the chlorine exposure experiments demonstrated that the restored membrane with the coating of sericin exhibited better resistance to chlorine compared to the new membrane. The simplicity and good reproducibility of the restoration treatment procedure and the satisfactory performance stability of the restored membrane reveal that the in-situ restoration approach of present work is attractive for practical applications. [ABSTRACT FROM AUTHOR]

Hot climate countries require large amounts of desalinated water. The Reverse osmosis (RO) technique is currently considered the most reliable technique for brackish water and seawater desalination. However, its power consumption is considerably higher than all other techniques. Therefore, the present study investigates the performance of reverse osmosis plants in hot climate conditions. A typical Reverse osmosis system was designed, constructed and investigated. The ROSA software was also used for the analysis of seven different membrane elements. The experimental data were utilized in order to validate the simulation results of the ROSA software. A variance-based sensitivity analysis was performed in order to define the most effective design and operating parameters. The present investigation shows that the tap and brackish water membrane elements are more sensitive to the feed water temperature rather than the feed water pressure and concentration. Meanwhile, seawater membrane elements are more affected by the feed concentration. The detailed investigation of the different membrane elements shows that wastewater reclamation using reverse osmosis technology could be a significant source of low-cost fresh water for hot climate countries. [ABSTRACT FROM AUTHOR]

Four dual media filters (DMFs) were operated in a biofiltration mode with different engineered environments (DMF I and II: coagulation with/without acidification and DMF III and IV: without/with chlorination). Designed biofilm enrichment reactors (BERs) containing the removable reverse osmosis (RO) coupons, were connected at the end of the DMFs in parallel to analyze the biofilm on the RO membrane by DMF effluents. Filtration performances were evaluated in terms of dissolved organic carbon (DOC) and assimilable organic carbon (AOC). Organic foulants on the RO membrane were also quantified and fractionized. The bacterial community structures in liquid (seawater and effluent) and biofilm (DMF and RO) samples were analyzed using 454-pyrosequencing. The DMF IV fed with the chlorinated seawater demonstrated the highest reductions of DOC including LMW-N as well as AOC among the other DMFs. The DMF IV was also effective in reducing organic foulants on the RO membrane surface. The bacterial community structure was grouped according to the sample phase (i.e., liquid and biofilm samples), sampling location (i.e., DMF and RO samples), and chlorination (chlorinated and non-chlorinated samples). In particular, the biofilm community in the DMF IV differed from the other DMF treatments, suggesting that chlorination exerted as stronger selective pressure than pH adjustment or coagulation on the biofilm community. In the DMF IV, several chemoorganotrophic chlorine-resistant biofilm-forming bacteria such as Hyphomonas , Erythrobacter , and Sphingomonas were predominant, and they may enhance organic carbon degradation efficiency. Diverse halophilic or halotolerant organic degraders were also found in other DMFs (i.e., DMF I, II, and III). Various kinds of dominant biofilm-forming bacteria were also investigated in RO membrane samples; the results provided possible candidates that cause biofouling when DMF process is applied as the pretreatment option for the RO process. [ABSTRACT FROM AUTHOR]

The ionic liquid (1,3-dimethylimidazolium dimethyl phosphate ([MMIM][DMP])) synthesized by addition reaction was used to modify a commercial reverse osmosis (RO) membrane thorough activation method. The activation promoted modification process was completed within just 6−12 min under optimal condition of the immersion time of 4 min, activation temperature of 110   °C and activation time of 4 min. The variation of surface morphologies and properties of the RO membrane were characterized by SEM, AFM, water contact angle, FTIR, and the RO performance was evaluated by desalination of 1000 mg⋅L −1 NaCl aqueous solution. The results showed that the active layer of the modified RO membrane became thinner, smoother, and more hydrophilic with increasing of activation temperature. The IL modified membrane achieved water flux of 33.7 L m −2  h −1 and rejection of 93.2%, showing 62% higher water flux comparing to the pristine membrane and 2.6% decrease in salt rejection. Moreover, the IL modified membrane showed an enhanced anti-fouling property with 95.5% of normalized water flux recovery. This work provides a facile and efficient way to modify and improve separation performance and anti-fouling property of commercial thin film composite (TFC) RO membranes. [ABSTRACT FROM AUTHOR]

This paper is a detailed study of the need to find and implement new solutions for water filtration and the promotion of modern techniques that are more effective than traditional methods. As a result of extension waste water pollution as well as low efficiency through classical filtration means, more and more research is being discussed and researched worldwide, focusing on the use of hybrid membranes for seawater desalination. Hybrid membrane filtration processes present a number of advantages including superior water quality but also reduced energy consumption that was needed in previous purification processes. This review describes the water desalination process in detail by looking at the relationship between membrane module operating parameters and energy efficiency. The methodology and the experimental installation of the desalination process will be presented in part. The results of the study clearly showed that the combined use of membrane processes is efficient due to the flexibility of exploitation, the low acquisition costs and the high degree of water filtration through low energy consumption. A major advantage in the use of membranes is that the energy required to conduct filtering processes can be obtained from solar, wind energy, which means significant environmental benefits by promoting "green energy". The worldwide implementation of the use of membrane water desalination methods also involves increasing the percentage of fresh water, so this is a solution to be considered in present and future research. [ABSTRACT FROM AUTHOR]

Polyamide (PA) reverse osmosis (RO) membranes suffer performance decay when exposed to oxidizing species, limiting their lifetime and increasing operation costs. This article aims at reviewing the effect of chlorine species on the performance and characteristics of PA-membranes. Experimental evidence supporting different competing mechanisms for chlorine-polymer interaction will be presented, together with the influence of operational parameters. Additionally, an overview of different modification methods that exist to render PA-membranes more chlorine-resistant is given. [ABSTRACT FROM AUTHOR]

Background: As an appropriate tool, membrane process is used for desalination of brackish water, in the production of drinking water. The present study aims to investigate desalination processes of brackish water of Qom Province in Iran. Methods: This study was carried out at the central laboratory of Water and Wastewater Company of the studied area. To this aim, membrane processes, including nanofiltration (NF) and reverse osmosis (RO), separately and also their hybrid process were applied. Moreover, water physical and chemical parameters, including salinity, total dissolved solids (TDS), electric conductivity (EC), Na+1 and Cl-1 were also measured. Afterward, the rejection percent of each parameter was investigated and compared using nanofiltration and reverse osmosis separately and also by their hybrid process. The treatment process was performed by Luna domestic desalination device, which its membrane was replaced by two NF90 and TW30 membranes for nanofiltration and reverse osmosis processes, respectively. All collected brackish water samples were fed through membranes NF90-2540, TW30-1821-100(RO) and Hybrid (NF/RO) which were installed on desalination household scale pilot (Luna water 100GPD). Then, to study the effects of pressure on permeable quality of membranes, the simulation software model ROSA was applied. Results: Results showed that percent of the salinity rejection was recorded as 50.21%; 72.82 and 78.56% in NF, RO and hybrid processes, respectively. During the study, in order to simulate the performance of nanofiltartion, reverse osmosis and hybrid by pressure drive, reverse osmosis system analysis (ROSA) model was applied. The experiments were conducted at performance three methods of desalination to remove physic-chemical parameters as percentage of rejections in the pilot plant are: in the NF system the salinity 50.21, TDS 43.41, EC 43.62, Cl 21.1, Na 36.15, and in the RO membrane the salinity 72.02, TDS 60.26, EC 60.33, Cl 43.08, Na 54.41. Also in case of the rejection in hybrid system of those parameters and ions included salinity 78.65, TDS 76.52, EC 76.42, Cl 63.95, and Na 70.91. Conclusions: Comparing rejection percent in three above-mentioned methods, it could be concluded that, in reverse osmosis process, ions and non-ion parameters rejection ability were rather better than nanofiltration process, and also better in hybrid compared to reverse osmosis process. The results reported in this paper indicate that the integration of membrane nanofiltration with reverse osmosis (hybrid NF/RO) can be completed by each other probably to remove salinity, TDS, EC, Cl, and Na. [ABSTRACT FROM AUTHOR]

Oily wastewaters from different onshore and offshore installations and from maritime transport pose a serious threat to the environment so they must be treated by multistage separation also including membrane processes. The main advantages of such membranes are high performance and selectivity, high resistance for temperature and pressure, resistance for acids, bases and solvents, long service life and for application - significant reduction of industries and transport environmental impact. This work presents the results of the process of separation of oil from the emulsion with NaCl addition. Research was performed with a use of laboratory installation with ceramic 300 kDa membrane. The analysis concerned performance and selectivity of a membrane in the function of time and test results have been subsequently compared with the requirements of the IMO. [ABSTRACT FROM AUTHOR]

Over the last few decades, significant efforts have concentrated on mitigating biofouling in reverse osmosis (RO) systems, with a focus on non-toxic and sustainable strategies. Here, we explored the potential of applying quorum quenching (QQ) bacteria to control biofouling in a laboratory-scale RO system. For these experiments, Pantoea stewartii was used as a model biofilm forming organism because it was previously shown to be a relevant wastewater isolate that also forms biofilms in a quorum sensing (QS) dependent fashion. A recombinant Escherichia coli strain, which can produce a QQ enzyme, was first tested in batch biofilm assays and significantly reduced biofilm formation by P. stewartii . Subsequently, RO membranes were fouled with P. stewartii and the QQ bacterium was introduced into the RO system using two different strategies, direct injection and immobilization within a cartridge microfilter. When the QQ bacterial cells were directly injected into the system, N- acylhomoserine lactone signals were degraded, resulting in the reduction of biofouling. Similarly, the QQ bacteria controlled biofouling when immobilized within a microfilter placed downstream of the RO module to remove QS signals circulating in the system. These results demonstrate the proof-of-principle that QQ can be applied to control biofouling of RO membranes and may be applicable for use in full-scale plants. [ABSTRACT FROM AUTHOR]

Perfluorooctane sulfonate (PFOS) has been under the spotlight in recent decades due to its adverse environmental and ecological concerns. Existing treatment methods (such as reverse osmosis and nanofiltration) for this recalcitrant surfactant are generally energy intensive. In this study, for the first time, a gravity-driven filtration using a highly porous nanofibrous membrane was systematically investigated for PFOS removal. The membrane possesses a high water permeability of 354.9 LMH/kPa, allowing the membrane to be operated under gravity-driven conditions. PFOS removal efficiency ranging from 36% to 90% was observed under a wide range of water chemistry conditions (5–20 ppb PFOS, pH 4–10, and ionic strength 1–10 mM). The best removal efficiency was obtained at pH 4 and 10 mM ionic strength as a result of the enhanced PFOS-membrane electrostatic attraction and/or weakened electrostatic repulsion. The removal efficiency was also higher at lower membrane permeate flux due to the increased residence time of PFOS molecules in the internal pores of the membrane. Simple methanol rinsing was able to effectively regenerate the membrane, and the high PFOS removal efficiency can be maintained over 20 cycles of regeneration. The current study may provide important insights of using highly porous membranes for energy-efficient PFOS removal and recovery. [ABSTRACT FROM AUTHOR]

Seawater reverse osmosis (SWRO) has been applied as a desalination method to provide potable water to regions under the stress of water shortages and is more effective than other desalination processes. However, specific energy consumption (SEC) must be considered in SWRO process design because of its energy intensive features. Hybrid membrane inter-stage design (HID) was examined to enhance the SEC efficiency of the reverse osmosis process. The additional removal of boron may improve the water quality by adding a second pass. However, this additional factor may increase costs. This study investigated a potential HID that satisfies water quality standards with single pass SWRO only. The element configuration for the HID was evaluated by changes in SEC, salt rejection, and boron rejection under general seawater quality conditions. Case studies were also conducted to estimate the energy efficiency of the HID under three feed conditions: high concentration and high temperature (Case 1); low concentration and high temperature (Case 2); and low concentration and low temperature (Case 3). The results showed HID application can save up to 0.41 kWh/m 3 of SEC. Temperature is a more important design factor than recovery rate for HID application. [ABSTRACT FROM AUTHOR]

POSS (polyhedral oligomeric silsesquioxane)-containing silica sols were prepared by hydrolysis/condensation of octakis(triethoxysilylethyl)-substituted POSS (TESE-POSS) and mixtures of 1,2-bis(triethoxysilyl)ethane (BTESE1) and TESE-POSS in HCl/H 2 O/EtOH. Nitrogen adsorption isotherms of bulk gels prepared by drying the sols indicated that the gels had porous properties with surface areas of 168–424 m 2 /g, depending on the BTESE1/TESE-POSS molar ratio. The sols were coated on SiO 2 /ZrO 2 /TiO 2 porous supports and calcinated at 350 or 400 °C to produce the membranes. Water desalination performance of the membranes was evaluated by reverse osmosis (RO) experiments using 2000 ppm NaCl aqueous solution. At 25 °C, liquid permeance was approximately 1 × 10 − 13 m/s·Pa and NaCl rejection was 90%. Interestingly, the membranes were robust to heat and chlorine. Membrane performance was not changed even after exposure of the membranes to as high as 1 × 10 4 ppm·h aqueous NaOCl. When RO experiments were conducted at 90 °C, liquid permeance was increased to approximately 1 × 10 − 12 m/s·Pa whereas NaCl rejection remained nearly unchanged, indicating potential application of the membranes to high-temperature water separation. Lowering the operation temperature again to 25 °C resulted in the recovery of the original data, indicating that the membranes were neither decomposed nor damaged upon contact with hot water. [ABSTRACT FROM AUTHOR]

In this work, the optimal schedule of membrane cleaning and replacement of spiral-wound SWRO (seawater reverse osmosis) system was studied and analyzed under different feed conditions. Firstly, the spiral-wound RO process model described by differential and algebraic equations was established with the consideration of membrane fouling. Then the optimization problem was formulated to minimize the daily cost of the SWRO system, and a new method by which the optimization problem was transformed as an NLP problem was proposed to solve the problem effectively and quickly. The method was used for SWRO case study and was compared with the traditional method in the form of MINLP. Computing results demonstrate that the proposed method has the advantages of efficiency and stability. Moreover, it can get schedule of membrane cleaning and replacement with lower operational cost as well as give more detailed information of membrane channel. Lastly, influence of feed temperature and feed concentration of seawater was analyzed with the new method. Computing results show the stability of the new method and lead to new profiles of optimal operational variables and performance when feed temperature and salt concentration change, which are quite different from those in designed conditions. [ABSTRACT FROM AUTHOR]

It is widely accepted that our understanding about the membrane process increases by investigation of the hydraulic conditions of membranes. While numerical studies have been broadly used for this purpose, the experimental studies of a comparable resolution are scarce. In this study, we compared the pressure drop, the temporal and the spatial velocity maps of a spacer-filled channel and an empty channel of the same size to determine the effect of presence of the feeds spacer on hydraulic conditions. The velocity maps are obtained experimentally by using of the Particle Image Velocimetry (PIV) technique. Application of the feed spacer caused 2–8.5 higher pressure drop increase in the experimental conditions in this research. The flow had a spatial distribution in the form of a unimodal symmetric curve of normal distribution in the empty channel and a bimodal asymmetric curve in the spacer-filled channel. The bimodal curve indicates the presence of high- and low-velocity zones. Additionally, the low-velocity zones showed also a lower variation of velocity in time, which indicates the high fouling potential of these locations. The results from this study may be uses for validation of numerical studies. [ABSTRACT FROM AUTHOR]

This study considers two novel ideas to further explore and enhance the graphene membrane for desalination. Firstly, while earlier molecular dynamics (MD) simulations studies have used frozen membranes, free-standing membrane is considered here. Since 2D membranes are usually embedded on porous support in the experimental reverse osmosis (RO) process, the free-standing membrane can more accurately model the behavior expected during operation. This study showed, using MD simulations, that a free-standing nanoporous graphene membrane can provide a higher salt rejection, but lower water permeability as compared to frozen membrane. Secondly, the performance of a slit membrane as compared to a membrane with circular pore is studied. At a pressure of 268 MPa, the critical diameter of circular pore that can maintain perfect salt rejection is found to be 5 Å and the critical size for a slit is determined to be 2.28 Å. It is shown that a slit membrane at its critical size can achieve water flux 3.5 times higher than a membrane with circular pore at its critical radius. This finding highlights the importance of slits over circular pores which can potentially widen the options for the design and fabrication of 2D graphene membranes for experimental verification of RO. [ABSTRACT FROM AUTHOR]

A novel Poly (vinyl alcohol) (PVA) reverse osmosis (RO) membrane with unique performance and characteristics was synthesized for water desalination. PVA thin film nanocomposite (TFN) membranes were fabricated by the infusion of Pluronic F-127 and multi-wall carbon nano-tubes (MWCNTs) in a single layer crosslinked by bisphenol A diglycidyl ether (DGEBA). The overall RO performance of the membranes including hydrophilicity, surface roughness, water permeability, salt rejection, chlorine resistance and biofouling resistance was evaluated using a dead end RO filtration unit. The incorporation of Pluronic F-127 and MWCNTs improved the overall RO performance of the membranes. It was found that the modified membranes surface became smoother and highly hydrophilic compared to the pristine PVA membranes surfaces. This study indicated that the membranes that contain 0.08 and 0.1 wt% MWCNTs provided excellent permeation, salt rejection, Chlorine and biofouling resistance and mechanical strength. The most striking result to emerge from this study is that the overall RO performance enhancement has transpired while utilizing PVA as an active RO separation layer without a polymeric or ceramic substrate. This study shows that proper crosslinking of PVA coupled with mechanical strength enhancement overcomes the common PVA drawbacks, mainly swelling and rupture under very high pressure. [ABSTRACT FROM AUTHOR]

RO membrane technology has been broadly applied in China in the past two decades and its applications increased quickly, as China is faced with a combination of rapid growth of heavy industries, large population, and water stress. The literature often underestimated the scale of RO applications in China as it was traditionally derived from surveys of RO membrane plants. Chinese RO market is highly monopolized, which provides an alternative to examine RO applications. This study collected manufacturing and sales data of RO membrane modules from limited RO membrane manufacturers, and analyzed the history and driving forces. For 2014, 1.8 million 8-inch RO membrane modules were used by membrane plants in China and the output capacity was about 27 million m 3 /d. RO plants are mainly applied for heavy industries, such as power, petrochemical, and coal industries. The power industry has highest number and output capacity of RO applications. RO plants are clustered in three regions, i.e. coastal provinces; northern China; and other provinces with advanced electronic, pharmaceutical and landfill leachate treatment industries. The RO applications in China were primarily driven by decreasing cost, rapid development of domestic membrane manufacturers, fast development of industries, and increasing water stress. [ABSTRACT FROM AUTHOR]

This paper discusses the steps followed to establish an accelerated reverse osmosis membrane biofouling test protocol. Easily bioassimilable nutrients were dosed into water from the Ebro River which was fed into a membrane flat cell pilot plant. The membrane biofouling results were determined by measuring adenosine triphosphate and total organic carbon extracted from the exposed membrane and feed spacer. This strategy was chosen because the equipment does not have pressure drop measurement capability and the observed change in flux or salt rejection was not significant under the testing conditions. The duration of the experiment was set to 3 d to enable rapid screening of different membrane types, yet enable a smooth evolution of biofilm. This study determined that achieving a similar amount of biofouling in each of the three cells was very sensitive to the level of bioassimilable nutrients were dosed to the water. For the Ebro River water, 0.2 mg/L of carbon, 0.04 mg/L of nitrogen, and 0.02 mg/L of phosphorous was determined to provide the best result. [ABSTRACT FROM PUBLISHER]

A brackish borehole located at a rural school in northern Tanzania contains excessive salinity (TDS = 3632 mg/L) and fluoride concentration (F − = 47.6 mg/L). This field study evaluated the feasibility of a solar-powered nanofiltration/reverse osmosis (NF/RO) system in treating this brackish water to make it potable. Key performance parameters such as permeate productivity, fluoride retention and specific energy consumption (SEC) were compared among four different NF/RO membrane modules (BW30, BW30-LE, NF90, and NF270). The NF90 membrane exhibited the best overall performance, balancing permeate productivity and quality, with 1582 L of clean drinking water being produced with an average SEC of 1.6 kWh/m 3 over a solar day, while the NF270 could not meet the guideline values for fluoride. Further, the impact of fluctuating solar energy on system performance was studied. Very brief periods of heavy cloud cover in the afternoon affected transmembrane pressure and feed flow, and thus caused the permeate quality to temporarily exceed the guideline values. However, when considering that the permeate was stored in a product tank and was produced over the whole solar day, the system equipped with the NF90 membrane was able to produce high-quality drinking water that, on average, easily meets the guideline values despite the energy fluctuations. [ABSTRACT FROM AUTHOR]

Several industrial processes, such as desalination or neutralization, generate brines defined as concentrated solutions of salts in water, usually NaCl, typically discharged in the vicinities of the desalination plant or factory. To reduce the environmental impact and promote the valorization of the wasted resources, alternatives must be sought. Among sustainable alternatives for the recovery of brines, the possibility of using Electrodialysis with Bipolar Membranes (EDBM) is of interest, because it allows recovering brines as useful acids and bases. This review focuses on the discussion of the technical aspects of the EDBM as a means to treat streams rich in NaCl from reverse osmosis desalination and industrial processes in order to complete the direct delivery of chemicals for self-supply. The main environmental issues associated with desalination brine disposal are presented. The state-of-the-art of valorization of brines by EDBM to acids and bases is completed. This work concludes with an in-depth discussion of the technical, techno-economic and economic barriers that prevent the widespread use of EDBM technology. [ABSTRACT FROM AUTHOR]

By pre-treating reverse osmosis (RO) feed water for process water production with cationic ion-exchange (IEX), scaling on the membrane can be avoided and the water recovery can be increased. Furthermore, by recycling the RO brine for the regeneration of the IEX, the addition of chemicals is avoided. A pilot-scale study of the hybrid IEX-RO system was performed. This study indicates that an RO recovery of 85% can be reached by removing the multivalent cations from the feed. In the IEX, the efficiency of the regeneration with the brine depends on the monovalent:multivalent cation ratio in the feed. In the case of low cation ratios, a minor addition of NaCl to the RO brine is sufficient to fully restore the IEX capacity. The CNK index was developed to predict the efficiency of the hybrid system for a given feed water. An economic analysis indicated that the water revenue for stand-alone RO is 0.52 €/m 3 , while for the hybrid process this revenue increases up to 0.69 €/m 3 , thus resulting in a pay-back time of 2.5 years. [ABSTRACT FROM AUTHOR]

Reverse osmosis (RO) desalination of 35,000 ppm seawater consisting of sodium and chlorine ions with water was simulated using molecular dynamics. In this study, RO simulations were performed at different pressures using carbon nanotube (CNT) membranes having varying pore diameters (8–14 Å). Results showed that a CNT membrane allowed high water fluxes because of the presence of a low energy barrier for water–carbon interactions, with continuous and ordered water chains observed inside the CNTs. The investigations into the ion rejection capability of CNT membranes revealed that (6, 6) CNTs could provide high rejection rates (>95%). The rejection of ions was mainly due to the presence of a high energy barrier caused by removing the hydrating water molecules necessary for ions to pass through the narrow CNT pore. The desalination performance of (6, 6) CNT membranes and conventional polymeric membranes was then compared. It was found that CNT membranes have a higher normalized flux and comparable ion rejection, indicating their feasibility for effective seawater desalination. Overall, this study demonstrated the usefulness of molecular dynamics in investigating membrane processes and its potential role in improving desalination performance. [ABSTRACT FROM PUBLISHER]

Bacterial biofilm formation, the main cause of membrane biofouling, is a crucial issue for membrane separation. Biofilm production is regulated by quorum sensing (QS) systems where bacteria secrete auto-inducers to communicate with neighboring bacteria. This research identified that several marine bacteria isolated from a desalination plant produced a low molecular weight auto-inducer 1 (AI-1) signaling molecule. AI-1 production in the mixed culture of the four different biofilm-forming marine bacteria was greater than in individual bacterial cultures. The QS inhibiting compounds, vanillin and cinnamaldehyde at 1200 mg/L significantly reduced biofilm formed by these marine bacteria by more than 79% and 70%, respectively in a microtiter plate assay. Anti-biofilm capabilities of vanillin and cinnamaldehyde were further assessed in a reverse osmosis membrane bio-monitoring system using mixed bacterial cultures and native uncultured bacterial communities in natural seawater. Confocal microscopy showed vanillin (1200 mg/L) significantly reduced biofilm extracellular polysaccharides and dead cells on the membrane surface (> 40%, > 20%). These results indicate that QS inhibitors have the potential to remediate membrane biofouling. [ABSTRACT FROM AUTHOR]

Reverse osmosis (RO) is the most employed technology for water desalination. Energy consumption and membrane fouling represent some of the major concerns in membrane technology because they increase the costs associated with treated water. Membrane lifespan is mainly correlated to the quality of the water and the operation condition and it is estimated that often membrane lifespan is 5 to 10 years. Remarkable advances have been made improving the reverse osmosis desalination by integrating pretreatment and cleaning processes. Attending to the membrane active layer, substantial research efforts have been conducted in preparing new antifouling RO membranes to i) enhance antifouling properties, ii) obtain high recovery flux and iii) have low energy requirements. However, scarce research has been detected in literature regarding end-of-life membrane management. This review summarizes the most representative research activities conducted to prevent membrane fouling. In addition, it highlights alternative routes to discarded end-of-life-membranes in order to prevent the uncontrolled disposal of fouled membranes in landfills. In this way, this review aims at summarizing research efforts found in literature in order to approach a more circular economy society, covering the whole life cycle of RO membranes: from the new development of antifouling membranes to the membrane waste management. [ABSTRACT FROM AUTHOR]

Forward osmosis (FO) is a promising membrane technology to combine seawater desalination and water reuse. More specifically, in a FO-reverse osmosis (RO) hybrid process, high quality water recovered from the wastewater stream is used to dilute seawater before RO treatment. As such, lower desalination energy needs and/or water augmentation can be obtained while delivering safe water for direct potable reuse thanks to the double dense membrane barrier protection. Typically, FO-RO hybrid can be a credible alternative to new desalination facilities or to implementation of stand-alone water reuse schemes. However, apart from the societal (public perception of water reuse for potable application) and water management challenges (proximity of wastewater and desalination plants), FO-RO hybrid has to overcome technical limitation such as low FO permeation flux to become economically attractive. Recent developments (i.e., improved FO membranes, use of pressure assisted osmosis, PAO) demonstrated significant improvement in water flux. However, flux improvement is associated with drawbacks, such as increased fouling behaviour, lower rejection of trace organic compounds (TrOCs) in PAO operation, and limitation in FO membrane mechanical resistance, which need to be better considered. To support successful implementation of FO-RO hybrid in the industry, further work is required regarding up-scaling to apprehend full-scale challenges in term of mass transfer limitation, pressure drop, fouling and cleaning strategies on a module scale. In addition, refined economics assessment is expected to integrate fouling and other maintenance costs/savings of the FO/PAO-RO hybrid systems, as well as cost savings from any treatment step avoided in the water recycling. [ABSTRACT FROM AUTHOR]

A new system was developed for the research on the cleanings of ultrasonic acid and alkali to the used reverse osmosis membrane (UROM). By continuously detecting the absorbance, conductivity and K + /Na + /Cl − /Ca 2 + contents in the cleaning solutions with this system, the cleaning information of organic and inorganic fouling on the UROM can be obtained and their cleaning effects can be judged directly. In the research, after comparing the cleaning effects of five kinds of acid solutions to the used polyamide ROMs, it was found that the ultrasonic cleaning effect of oxalic acid is the best. Therefore the concentration and pH of the oxalic acid, the sequence of acid and alkali cleanings were investigated, the results showed that, when the pH of 0.2% oxalic acid was regulated to 2.5 by the ammonia water, the defouling rate of the UROM can be reached 91%, and if employing the acid and alkali solutions to simultaneously clean, the best cleaning effect will be obtained, in which the cleaning order should be the first acid then alkali plus the ultrasound. The results and parameters obtained in this study can be used as a reference basis for designing large-scale chemical and ultrasonic cleaning system of UROM. [ABSTRACT FROM AUTHOR]

The potential of the carbon nanotube (CNT) membrane has been highly strengthened in water treatment during the last decade. According to works published up to now, the unique and excellent characteristics of CNT outperformed conventional polymer membranes. Such achievements of CNT membranes are greatly dependent on their fabrication methods. Further, the intrinsic properties of CNT could be a critical factor of applicability to membrane processes. This article provides an explicit and systematic review of the progress of CNT membranes addressing the current epidemic—whether (i) the CNT membranes could tackle current challenges in the pressure- or thermally driven membrane processes and (ii) CNT hybrid nanocomposite as a new generation of materials could complement current CNT-enhanced membrane. [ABSTRACT FROM AUTHOR]

Salinity gradient power is proposed as a source of renewable energy when two solutions of different salinity are mixed. In particular, Pressure Retarded Osmosis (PRO) coupled with a Reverse Osmosis process (RO) has been previously suggested for power generation, using RO brine as the draw solution. However, integration of PRO with RO may have further value for increasing the extent of water recovery in a desalination process. Consequently, this study was designed to model the impact of various system parameters to better understand how to design and operate practical PRO-RO units. The impact of feed salinity and recovery rate for the RO process on the concentration of draw solution, feed pressure, and membrane area of the PRO process was evaluated. The PRO system was designed to operate at maximum power density of Δ P = Δ π 2 . Model results showed that the PRO power density generated intensified with increasing seawater salinity and RO recovery rate. For an RO process operating at 52% recovery rate and 35 g/L feed salinity, a maximum power density of 24 W/m 2 was achieved using 4.5 M NaCl draw solution. When seawater salinity increased to 45 g/L and the RO recovery rate was 46%, the PRO power density increased to 28 W/m 2 using 5 M NaCl draw solution. The PRO system was able to increase the recovery rate of the RO by up to 18% depending on seawater salinity and RO recovery rate. This result suggested a potential advantage of coupling PRO process with RO system to increase the recovery rate of the desalination process and reduce brine discharge. [ABSTRACT FROM AUTHOR]

In order to facilitate the global performance of seawater reverse osmosis (SWRO) systems, it is important to improve the feed water quality before it enters the RO. Currently, many desalination plants experience production losses due to incidents of organic and biofouling. Consequently, monitoring or characterizing the pretreatment step using more advanced organic and biological parameters are required for better operation to lessen fouling issues. In this study, the performance of pretreatment processes (including coagulation, dual media filtration (DMF), polishing with cartridge filter (CF) coupled with anti-scalant) used at Perth Seawater Desalination Plant (PSDP) located in Western Australia were characterized in terms of organic and biological fouling parameters. These analyses were carried out using liquid chromatography with organic carbon detector (LC-OCD), three dimensional-fluorescence excitation emission matrix (3D-FEEM) and assimilable organic carbon (AOC). Furthermore, the used (exhausted) RO membrane and CF were autopsied so that the fates and behaviors of organic foulants in these treatment systems could be better understood. [ABSTRACT FROM AUTHOR]

Membrane fouling in reverse osmosis (RO) systems caused by organic matter (OM) remains a significant operational issue during desalination. Dissolved air flotation (DAF) has recently received attention as a pre-treatment option for seawater OM removal; however, only a limited number of studies have been undertaken. This may be because it is difficult to characterise OM in seawater due to the high salt content and low carbon concentration. In this study, DAF pre-treatment experiments were conducted using a model seawater solution, and real seawater and brackish water samples. DAF performance was determined via conventional water quality parameters as well as fluorescence excitation–emission matrix (FEEM) spectroscopy and liquid chromatography with organic carbon detection (LC-OCD). Biopolymers and humic substances were the major organic fractions removed between 38 and 84% and 20–61% depending on the sample, respectively. The optimal normalised coagulant dose (Fe 3 + to DOC ratio) was observed to be 0.5–4 at pH 5.5 increasing to 4–12 at pH 7.5. At pH 5.5, the optimum coagulant dose increased with increasing humic character of the feed water. Overall, the OM removal efficiency by DAF observed in this study was higher than reported for other membrane-based processes; a combination of DAF and biofiltration is likely to be complementary. [ABSTRACT FROM AUTHOR]

Membrane technology is the dominant process in water treatment. However, the operation cost of membranes cannot be decreased unless the amount of fouling, the “Achilles heel” of membranes, and energy consumed are cut. The high energy requirements in commercial nanofiltration, reverse osmosis and forward osmosis technologies lead researchers to develop new membrane designs having high flux values with high salt rejection values. The purpose of this review is to present the inadequacies of the membrane processes by considering studies related to fouling and energy minimization. In this respect, lipid bilayers, block copolymers, aquaporin Z proteins and aligned carbon nanotubes can be the base to build biomimetic membranes. Such studies are summarized due to their remarkable properties in fouling control. Furthermore, the review describes the membrane design strategies and points the limitations hindering commercialization. Additionally, it is hoped that this review will trigger further needed studies. [ABSTRACT FROM PUBLISHER]

Recent forward osmosis–bioelectrochemical hybrid systems (FO-BESs) have been designed to simultaneously produce bio-energy and clean water from wastewater. Asymmetric forward osmosis (FO) membranes are a crucial component for determining FO-BES performance, but only cellulose triacetate (CTA NW) membranes in the same orientation have been applied to FO-BESs. In this work, both CTA NW and polyamide (PA) membranes were tested in two membrane orientations (active layer facing feed solution or anolyte and support layer facing feed solution). For an in-depth understanding of the FO membranes, properties were investigated using scanning electron microscopy, contact angle, impedance spectroscopy, and proton transport analyses. The electricity generation and water extraction in FO-BESs having these two FO membranes in different orientations were then evaluated. Based on membrane characterization, PA seemed to be a proper membrane for the FO-BES because of higher hydrophilicity, lower membrane thickness, lower mass transfer resistance, and better proton transfer ability. However, there was no significant current output difference between the FO-BESs having CTA NW and PA. Rather, in terms of water flux, the FO-BESs having CTA NW in the support layer facing feed solution orientation showed better performance. [ABSTRACT FROM PUBLISHER]

Membrane ageing reduces the quality of the filtered water. Therefore, in order to warrant public health, monitoring membrane performances are of utmost importance. Reverse osmosis (RO) membranes are generally used to remove viruses and salt. However, there is no detailed study demonstrating the impact of aged membrane on the rejection of viruses and of membrane integrity indicators. In this paper, the impact of hypochlorite induced RO ageing on the rejection of a virus surrogate (MS2 phage) and four membrane integrity indicators (salt, dissolved organic matter, rhodamine WT and sulphate) was evaluated. Hypochlorite exposure was either active (under filtration) or passive (soaking), and the changes of the membrane surface chemistry were characterised using several autopsy techniques. Under this accelerated ageing condition, the introduction of chlorine in the membrane chemistry and the breakage of amide bonds caused an increase of the water permeability and a decrease of the virus surrogate's and indicators' rejection. Ageing resulted in a more negatively charged membrane and also in a higher hydrophobicity, which lead to the adsorption of MS2 phage. Despite severe physical membrane damage leading to a reduction of salt rejection to 1.2 log (94%), the minimum rejection of MS2 phage stayed on or above 4 log. [ABSTRACT FROM AUTHOR]

Membrane fouling is an important shortcoming limiting the efficiency and wide application of reverse osmosis (RO) technology. In this paper, RO membranes in a full-scale municipal wastewater reclamation plant were autopsied. From the lead to tail position RO membranes in RO system, both of organic and inorganic matters on membranes reduced gradually. The higher ion products in RO concentrate didn't result in more serious inorganic scaling on the last position RO membranes, which was contrast with some other researches. Fe, Ca and Mg were major inorganic elements. Fe had a relatively low concentration in RO influent but the highest content on membranes. However, there was no specific pretreatment in terms of Fe removal. Ca and Mg scaling was controlled by the antiscalants injected. Organic fouling (75.0–84.5% of dry weights) was major problem on RO membranes due to the large amount of dissolved organic matters in secondary effluent as raw water. Hydrophilic acid (HIA, 48.0% of total DOC), hydrophobic acid (HOA, 23.6%) and hydrophobic neutral (HON, 19.0%) fraction was largest among the six fractions in RO influent, while HON (38.2–51.1%) and HOA (22.1–26.1%) tended to accumulate on membranes in higher quantities. Monitoring HON and HOA might help to forecast organic fouling. [ABSTRACT FROM AUTHOR]

Investigated are working characteristics of reverse-osmotic membranes of low pressure ESPA-1 and TFC-75 in purifying aqueous solutions of phosphates in the range of their concentrations 10-490 mg/dm. It is shown that at minor difference of selectivity of studied membranes with respect to phosphate-ions the specific capacity of the membrane ESPA-1noticeably exceeds such of the membrane TFC-75. [ABSTRACT FROM AUTHOR]

Fluctuations in solar irradiance were varied in frequency and magnitude to investigate the performance of a directly-connected solar energy powered reverse osmosis (RO) membrane system. Typically, the system produced acceptable quality water with constant solar irradiances ranging from 400 to 1200 W m −2 . Low average motor powers were encountered during fluctuations, however, in many cases, good performance was still realised, even at solar irradiance values that were equivalent to <400 W m −2 . This counter-intuitive result arises from the effect of averaging the motor power, with periods of high solar irradiance compensating for the under-performance at times when the system was off. Overall, even though the permeate flux was often low when operating under fluctuating conditions, the RO system continued to deliver satisfactory quality water and at a low specific energy consumption (SEC). Temporal studies revealed that a disruption of the concentration polarisation layer occurs via a naturally induced backwash for steps in the solar irradiance as low as 100 W m −2 . This suggests that a renewable energy powered RO filtration system could benefit from being operated from a fluctuating energy source. Furthermore, the operating conditions during the first couple of minutes after a system shutdown event is shown to be very important, with: (i) shorter off-periods resulting in good performance being achieved quicker, and (ii) short-term power availability dramatically improving system performance. These findings indicate that a renewable energy powered RO system can operate well from a fluctuating energy source, in particular when additional power – for example, via supercapacitor energy buffering – is available to boost the system after a shut-down period. [ABSTRACT FROM AUTHOR]

Ion-exchange (IEX) and Donnan dialysis (DD) are techniques which can selectively remove cations, limiting scaling in reverse osmosis (RO). If the RO concentrate could be recycled for regeneration of these pre-treatment techniques, RO recovery could be largely increased without the need for chemical addition or additional technologies. In this study, two different RO feed streams (treated industrial waste water and simple tap water) were tested in the envisioned IEX–RO and DD–RO hybrids including RO concentrate recycling. The efficiency of multivalent cation removal depends mainly on the ratio of monovalent to multivalent cations in the feed stream, influencing the ion-exchange efficiency in both IEX and DD. Since the mono-to-multivalent ratio was very high in the waste water, the RO recovery could potentially be increased to 92%. For the tap water, these high RO recoveries could only be reached by adding additional NaCl, because of the low initial monovalent to multivalent ratio in the feed. In both cases, the IEX–RO hybrid proved to be most cost-efficient, due to the high current cost of the membranes used in DD. The membrane cost would have to decrease from ±300 €/m² to 10–30 €/m² – comparable to current reverse osmosis membranes – to achieve a comparable cost. In conclusion, the recycling of RO concentrate to regenerate ion exchange pre-treatment techniques for RO is an interesting option to increase RO recovery without addition of chemicals, but only at high monovalent/multivalent cation-ratios in the feed stream. [ABSTRACT FROM AUTHOR]

This paper discusses the feasibility of using reverse osmosis concentrate to backwash ultrafiltration membranes in the seawater reverse osmosis desalination space. Brine is produced through DOW FILMTEC™ reverse osmosis elements and it backwashed every 90 min to DOW™ ultrafiltration membranes. A side-by-side validation is done for 15 d using two parallel ultrafiltration and reverse osmosis integrated systems. One line uses brine for backwashing, while the other uses conventional filtrated water. The optimization is proven to have the same cleaning efficiency than the conventional backwashing methods and no precipitation is observed in the fibers. An additional validation period that uses reverse osmosis brine during backwashes and only two backwash steps is also carried out successfully. These steps are the previously identified backwash top with air scour and forward flush. Fibers also show an excellent integrity after the whole experimental period. A model is built in order to analyze the backwash efficiency of the optimized conditions and the transmembrane pressure increases during the filtration cycle. The results show the same fouling tendency for the line operating with brine and the line operating with filtrated water. The efficiency of the ultrafiltration process is improved from 88 to 98% thanks to this optimization together with the previous researches. This represents filtrating 96 min extra per day and a reduction of 100% in the filtrated water used during backwashes. The chemical equivalent concentration is also optimized from 0.28 to 0.06 mg/L NaClO thanks to the adjustment of the chemically enhanced backwash frequency. This accounts for a 7.1% savings in the ultrafiltration step and for a 1.2% savings in the whole desalination process. [ABSTRACT FROM PUBLISHER]

This paper proposes a simple design method of the RO system in RO brackish water desalination plants. This method is based on the application of maximum available recovery without scaling of any of the compounds present in the water as silica, calcium carbonate, calcium sulfate, barium sulfate, strontium sulfate, and calcium fluoride, and membrane manufacturer design guidelines, and the plant production. It is a continuation of the paper “A design method of the RO system in reverse osmosis brackish water desalination plants (procedure)” presented at the conference on Membranes in Drinking and Industrial Water Production, Leeuwarden, The Netherlands, 10–12 September 2012. Although the method was originally conceived for application to subterranean brackish waters in the Canary Islands, Spain (principally Gran Canaria, Fuerteventura and Tenerife), it can be extrapolated to other types of region and water treatable with RO systems. The required input data are the chemical composition of the feed water, pH, temperature, SDI, membrane manufacturer design guidelines, and the plant production. The programmed method determines the design of the RO system (arrangement) and the operating pressure so as the quality of the product water for different operating years and different types of the RO elements. The method whose procedure is described graphically and analytically can be used as an aid in design optimization of RO brackish water desalination plants with acid-free pre-treatment processes and by the use of scale inhibitor using spiral wound membranes. Practical applications are presented. Calculations and simulations for different types of feed water and capacities are showed. A comparison between the values obtained by this method and from membranes manufacturer software is shown so as the comparison between these and the real values from different desalination plants. [ABSTRACT FROM PUBLISHER]

The Palmachim Seawater desalination plant supplies to the Israeli water net potable water in accordance with all contractual requirements of water quality and quantity. The plant was commissioned in 2007 and produced up to 110,000 m3d−1(30 million m3/year). During 2009–2010, the plant production capacity was expanded up to 150,000 m3 d−1(45 million m3/year). Recently, the plant production capacity was further increased, doubling production rate up to 300,000 m3 d−1(90 million m3/year). This paper provides a general overview of the work undertaken along the years to accomplish the final assembly of the plant. The main plant characteristics are described, notably the small footprint, high operational flexibility, low energy consumption, and low chemicals usage. In addition to the physical constructions, the recent expansion incorporated several significant process modifications, aiming to improve the efficiency of the plant. A description of the characteristics of two main modifications is displayed: the use of new generation seawater reverse osmosis membranes in the desalination trains that enabled a reduction in energy cost and changes in the post-treatment hardening that led to a significant reduction in the chemicals consumption. [ABSTRACT FROM PUBLISHER]