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Abstract Several fouling indexes, such as silt density index (SDI), have been applied in the reverse osmosis (RO) process to predict the fouling tendency, design the pretreatment process, and optimize the cleaning cycles. However, the forward osmosis (FO) process has no reliable method, as yet, that relates fouling with its performance. This study utilized the concept of fouling reversibility to develop a fouling index for the FO process simulation. The osmotically driven reversibility index (ORI) was determined by measuring the flux recovery after the physical cleaning or flushing cycle. The protocols of ORI measurement were developed systematically by determining the proper operation mode, cross-flow velocity for physical cleaning, and draw solution type and concentration. The applicability of ORI was examined by investigating the FO process in treating secondary effluents from various full-scale wastewater treatment plants. The results demonstrated that the normalized final flux by fouling in FO was closely correlated to the ORI measurements with high statistical reliability (R2 = 0.84). After conducting a long-term stable FO operation, it is deduced that the ORI is a useful evaluation parameter for continuous FO and its cleaning cycles in which periodic flushing is normally utilized to exploit and enhance the fouling reversibility of FO. Graphical abstract fx1 Highlights • An osmotically-driven reversibility index (ORI) was developed for FO process. • ORI simulates FO fouling reversibility and its operational protocol was constructed. • High correlation of ORI and FO fouling was obtained using various real wastewaters. • ORI is a useful evaluation parameter for continuous FO and its cleaning cycles. [ABSTRACT FROM AUTHOR]

During filtration in reverse osmosis membranes (ROM), the system performance is dramatically affected by membrane fouling which causes a significant decrease in permeate flux as well as an increase in the energy input required to operate the system. In this work, we develop a model, able to dynamically capture foulant evolution, that couples the transient Navier–Stokes and the advection–diffusion equations, with an adsorption–desorption equation for the foulant accumulation. The model is validated against unsteady measurements of permeate flux as well as steady-state spatial fouling patterns. For a straight channel, we derive a universal scaling relationship between the Sherwood and Bejan numbers, i.e. the dimensionless permeate flux through the membrane and the pressure drop along the channel, respectively, and generalize this result to membranes subject to morphological and/or topological modifications, i.e. whose shape (wiggliness) or surface roughness is altered from the rectangular and flat reference case. We demonstrate that a universal scaling can be identified through the definition of a modified Reynolds number, $Re^{\star }$ , that accounts for the additional length scales introduced by the membrane modifications, and a membrane performance index, $\unicode[STIX]{x1D709}$ , an aggregate efficiency measure with respect to both clean permeate flux and energy input required to operate the system. Our numerical simulations demonstrate that 'wiggly' membranes outperform 'rough' membranes for smaller values of $Re^{\star }$ , while the trend is reversed at higher $Re^{\star }$. The proposed approach is able to quantitatively investigate, optimize and guide the design of both morphologically and topologically altered membranes under the same framework, while providing insights into the physical mechanisms controlling the overall system performance. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Introduction of the environmental impacts index on RO system. • Choosing the optimum configuration and ORC fluid from 4E+D point of view. • The benefit of low grade heat losses to reduce the environmental impacts of RO. • Water-Energy-Environmental nexus. Abstract This paper presents the concentration disposal index (CDI) concept extension for increasing the Water–Energy-Environmental nexus and reducing the environmental impacts of RO system brine. This non-dimensional index introduces the difference between the density of brine flow and raw water tank in recovery. This concept is utilized in main engine system of the ship. Different configurations of Organic Rankine Cycle (ORC) and working fluids are studied at the outlet of high temperature thermal source (280 °C), based on Energy analysis (1E), Exergy (2E), Economic (3E) and environmental impacts (4E) in order to produce desalinated water (4E+D). The output power from ORC is used as the driver of RO high pressure pump. Based on the waste heat in system, the sources are used for preheating of RO system pump inlet water. These sources are: Lubricating oil, air cooler and jacket cooler and ORC condenser. The key parameters in optimization are: (1) the ORC configuration choice, (2) the working fluid of Rankine cycle based on thermal source, (3) the RO system optimum design, (4) the membrane selection among the DOW company membranes, (5) the pinch and approach temperatures of the Waste Heat Recovery (WHR), (6) the reduction of environmental impacts of RO brines, (7) the selection of Energy Recovery Device (ERD). Determination of these parameters is done according to system optimization by genetic algorithm (GA). In order to consider the CDI function impact, once the system is considered with two objectives based on exergy efficiency of the entire cycle and the unit product cost (UPC) and then is considered by three objectives; the two mentioned ones and the CDI function. The results of these two optimizations indicate that, utilizing CDI reduces the ultimate concentration of the brine and increases the buoyancy force for faster mixture. In three-objective optimization, the ORC configuration is chosen with the recuperator, the R245ca working fluid, the two-stage RO system and the SW30XLE-400i membrane for both of stages. [ABSTRACT FROM AUTHOR]

Water is a key resource for sustainable development and plays a crucial role in human development. Desalination is one of the most promising technologies to mitigate the emerging water crisis. Thermal desalination and reverse osmosis are two of the most widely employed desalination technologies in the world. However, these technologies are energy intensive. Clathrate-hydrate-based desalination (HyDesal) is a potential energy-efficient desalination technology to strengthen the energy-water nexus. In our previous study, we proposed a ColdEn-HyDesal process utilizing waste Liquefied Natural Gas (LNG) cold energy based on a fixed-bed reactor configuration. In this study, we evaluated the effect of 10% propane in three different gas mixtures, namely, nitrogen (G1), argon (G2), and carbon dioxide (G3), as hydrate formers for the HyDesal process. The achieved water recovery was very low (~2%) in the presence of NaCl in the solution for gas mixtures G1 and G2. However, high water recovery and faster kinetics were achieved with the G3 mixture. To improve the water recovery and kinetics of hydrate formation for the G2 gas mixture, the effect of sodium dodecyl sulfate (SDS) was evaluated. The addition of SDS did improve the kinetics and water recovery significantly. [ABSTRACT FROM AUTHOR]

Small-scale reverse osmosis plants that can produce less than 50 m³/d are vital for small communities in villages located in remote areas. The design parameters of such plants involve low flow rate and high-pressure feed. For such operating conditions, reciprocating pumps are more favorable than centrifugal pumps because the efficiency of centrifugal pumps in such conditions is reduced extensively. Recently, reciprocating pumps with energy recovery are presented by several pump companies for desalination applications. The concept of energy recovery in these pumps is quite similar to that used in pressure exchangers. In these pumps, the pressurized brine is directed to the back of the pumping pistons which reduces the pumping motor required power. This work presents a numerical simulation and experimental analysis for such pumps. The numerical simulation includes a computational fluid dynamics transient analysis for the used pump. The analysis is presented using both two-dimensional and three-dimensional models. The effects of the operational and design parameters on the performance of the pump and its volumetric efficiency are investigated. The results show that increasing the valve spring stiffness increases the volumetric efficiency. It also shows that increasing the outlet pressure and piston speed reduces the volumetric efficiency. The most striking result to emerge from the data is that reducing the valve spring stiffness below a specific value results in large reduction on the volumetric efficiency. Results of pump’s testing at different operating conditions are evaluated. The results of the presented numerical simulation were compared with the experimental results at several operating conditions, and the deviation was less than 10%. [ABSTRACT FROM AUTHOR]

Energy and water are essential components to any civilization. Both are important for industrial, agricultural and societal development. Desalination seems to be one of the most suitable solutions to the water problem. The integration of renewable energy into water desalination systems has become increasingly attractive due to the growing demand for water and energy. In this paper, a proposed model consists of a solar photovoltaic (PV) powered seawater reverse osmosis desalination plant for the southern region of the Gaza Strip. The proposed system of reverse osmosis plant with a capacity of 2,400 m³/h is designed using ROSA software. As the solar PV plant is designed using System Advisor Model software that does not rely on expensive batteries, the water production cost is nearly the same as the current expenses (0.56 USD/m³). The simple payback period for PV plant was found to be 5.9 years, the nominal levelized cost of energy was 9.3 cents/kWh, the net present value was around $800,000 and the investor internal rate of return was 10.6% (which is greater than the interest rate 6%). The system reduces the emission of greenhouse gases. Comparing the results obtained with the conventional values, this model would provide a much needed efficient compensator of the shortage of water and energy, making it more sustainable and economically feasible. [ABSTRACT FROM AUTHOR]

Aqueous extract of sunflower (Helianthus annuus) seeds was used as a novel environmental friendly additive to improve the performance and anti-biofouling properties of cellulose acetate reverse osmosis (RO) membranes. Modified membranes were characterized by Fourier transform infrared spectroscopy and scanning electron microscopy, while the anti-biofouling properties were studied by water contact-angle measurements, water content measurements, and static protein adsorption. The effect of modification of the membrane on the salt rejection and water flux was studied using a cross-flow RO unit. The results indicated that modified membranes have lower contact angle accomplished with high water content. They showed limited adsorption of protein and microbes, in addition to increased salt rejection and water flux values. [ABSTRACT FROM AUTHOR]

Abstract Recent progress in reverse osmosis (RO) technology is not limited to RO membrane materials, module designs and RO process optimization. It involves prior feed treatment which directly impacts RO system performance. The ongoing challenges of membrane fouling in RO membranes can be addressed by increasing the operational efficiency through the use of correct pretreatment options which can mitigate organic and inorganic fouling by selectively rejecting contaminants prior to reaching the RO unit. Highly polluted water resources have put critical stress on the existing conventional pretreatment techniques, whereby membrane pretreatment has emerged as a promising alternative. This paper provides an overview of the development and current trends in conventional and non-conventional RO pretreatment techniques whereby the techniques are critically reviewed to inform readers of potential improvements in such areas. This paper addresses the major drawbacks of conventional pretreatment methods which have necessitated the use of membrane pretreatment techniques. Special attention is given to microfiltration, ultrafiltration and nanofiltration methods and their development in terms of advanced membrane materials based on ceramics and self-cleaning membranes. Studies from laboratory scale standalone systems, pilot scale and large scale integrated systems for performance, cost and ecological analysis have been reviewed to familiarize readers with the many factors which need to be analyzed for selection of the appropriate pretreatment method(s). The critical review in this paper will help researchers focus more on the areas which have room for further development for cost-effective and advanced RO pretreatment techniques. Highlights • Reverse osmosis (RO) pretreatment continues to be one of the most challenging aspects of RO plants. • Membrane pretreatment capital and operational cost is higher than conventional pretreatment. • Membrane pretreatment water production cost is smaller than conventional ones due to improved permeate quality. • Ultrafiltration system with minimal prior pretreatment can reduce the cost of the overall RO process. • Integrated pretreatment systems incorporating nanofiltration saved up to 25–30% energy. [ABSTRACT FROM AUTHOR]

Abstract In the context of decentralised brackish water treatment in development applications, the influence of water quality on membrane separation was investigated with real waters. High ionic strength (low net driving pressure) on fluoride (F) retention by nanofiltration (NF) and reverse osmosis (RO) was investigated over a wide pH range (2–12). Further, the influence of pH on the permeation of natural organic matter (NOM) fractions, in particular low molecular weight (LMW) neutrals, was elucidated. Natural and semi-natural waters from Tanzania with similar F concentrations of about 50 mg L−1 but varying NOM and inorganic carbon (IC) concentration were filtered with an NF and RO, namely NF270 and BW30. F retention by NF270 for the feed water with highest ionic strength and IC concentration was lower and attributed to charge screening. This parameter further reduced at high pH due to co-ions (F− and CO 3 2−) interactions and combined (synergistic) effect of high salt concentration and pH on F. High NOM resulted in higher membrane zeta potential in comparison with low NOM natural water. However, there was no significant difference in F retention due to the fact that F retention enhancement was annulled by deposit formation on the membrane. The fraction of NOM found in NF/RO permeates was dominated by LMW neutrals. This was attributed to their size and uncharged nature, while their higher concentration at low pH remains unexplained. More humic substances (HS) of higher molecularity and aromaticity permeated the NF270 when compared with BW30, which can be explained with the different membrane molecular weight cut off (MWCO). The study highlights the complexity of treating tropical natural waters with elevated F and NOM concentrations. In order to develop appropriate membrane systems that will achieve optimal F and NOM removal, the influence of water quality parameters such as pH, NOM content, ionic strength and IC concentration requires understanding. Seasonal variation of water quality as well as operational fluctuations, which occur in particular when such treatment processes are operated with renewable energy, will require such challenges to be addressed. Further, given the high permeability of low molecular weight (LMW) organics significant permeate side fouling may be expected. Highlights • Real tropical waters with different IS, IC, NOM but similar F content treated by NF/RO. • At high IS & pH, F retention decreases due to IC speciation, pH and salt effect. • No enhancement effect of high NOM on F retention was observed. • A discrepancy between permeate NOM measured by TOC analyser and LC−OCD was observed. • According to LC−OCD results, LMW neutrals accounted for 60–90% of permeate NOM. [ABSTRACT FROM AUTHOR]

As Independent water and power plant projects (IWPPs) connecting electricity generation and desalination is rapidly growing, interest in the SWRO (Seawater reverse osmosis) process is increasing. However, membrane fouling is an important problem in seawater reverse osmosis (SWRO) processes, because it was one of factors by increasing operating expenses. Many studies have been conducted to control this. However, only clean-in-place (CIP) is carried out. There is a need for practical maintenance cleaning. The objective of this study was to examine characteristics of membrane fouling by operating SWRO pilot plants using hot wastewater generated from power plants and derive maintenance chemical cleaning (MCC) applicable to these sites. Results of this study, depending on the operating conditions of the power plant, the influent water temperature showed a change of about 5ºC. This affected the operating pressure of the SWRO pilot plant and fluctuates by about be 7 kgf/cm on average. This variation in water temperature caused by characteristics of hot wastewater generated from power plant directly affected fouling on membrane. Results of MCC and cleaning wastewater showed that organic fouling was dominant. With increasing water temperature, the structure of protein was unfolded and its surface charge was converted to positive charge. Such protein with positively charged surface then formed insoluble aggregates through mutual bonding with negative charge of polysaccharide. This was considered the main cause of accelerated membrane fouling. In order to control membrane fouling, possible way of MCC method was derived for field application. It was performed under various conditions (only acid, acid-alkali, alkali-acid, or only alkali). As a result, alkali-acid cleaning was found to be an optimal protocol because the main cause of membrane fouling due to water temperature change was found to be organic foulants. Therefore, it is considered that MCC can be applied as a operational strategy for organic fouling control in a seawater desalination plant using feed water with frequent temperature changes in a power plant. [ABSTRACT FROM AUTHOR]

Abstract Swine wastewater treatment plant has become one of the main sources of antibiotic resistance genes (ARGs). Membrane treatment processes are promising solutions for removal of the emerging contaminants. However, limited studies have investigated the effects of nanofiltration and reverse osmosis treatment in removing ARGs in swine wastewater. In this study, the presence and the fate of common ARGs including sul 1, sul 2, tet A, tet M and tet W, as well as intI 1 and 16S rRNA gene, were investigated in a medium-sized (6500) pig farm wastewater treatment plant (WWTP) equipped with conventional biological treatment and advanced membrane processing system. All of the genes were detected with highly abundance in the raw sewage. The biological treatments of the swine wastewater treatment plant did not reduce the quantity of the ARGs. As expected, nanofiltration and reverse osmosis treatment reduced the absolute gene copy number of ARGs efficiently (4.98–9.52 logs removal compared to raw sewage). Compared to the reverse osmosis effluent, however, the absolute abundance of ARGs in the artificial wetland increased by 1.00–2.06 logs. Meanwhile, the relative abundance of sulfonamide resistant genes were basically unchanged, while tetracycline resistance genes (tet A, tet M and tet W) decreased by 0.88, 3.47, 2.51 log, respectively. The results demonstrated that advanced membrane treatments are capable of removing various kinds of ARGs efficiently, as well as some common nitrogen and phosphorus contaminants. This study suggested a mature alternative method for the removal of ARGs from livestock wastewater. Graphical abstract Image 1 Highlights • Swine sewage presents high content of ARGs. • Nanofiltration and reverse osmosis reduces ARGs, nitrogen and phosphorus contaminants. • The abundance of ARGs in artificial wetland increased. [ABSTRACT FROM AUTHOR]

The article offers information related to the use of Reverse Osmosis (RO) in the chemical process industries (CPI). Topics discussed include need to understand best practices for troubleshooting, monitoring and cleaning; RO as a desalination technique to operate effectively at minimal cost and primary membrane type used in modern RO systems based on polyamide chemistry and preparation techniques.

Abstract One possible contender to replace conventional reverse osmosis schemes is an energy solution where inexhaustible resources work together with a reverse osmosis plant. Based on the experience of an existing wind-powered desalination scheme run for more than 15 years by Soslaires Canarias S.L., the final objective of this paper is to propose improvements to the scheme so as to achieve a reduction in the cost of water (through restrained capital expenses) for the sake of greater feasibility and efficiency. The cost of the scheme is evaluated assuming a combined use of a reverse osmosis desalination plant and wind energy, using, for this purpose, the (exclusive) information provided by the industrial partner. Results showed that by carrying out the actions suggested in this paper, this scheme would be able to reduce its cost of water (COW) by about 0.022 EUR per cubic meter for the current LCOE of wind turbine technology in the study area (about 6 c€/kWh for the southeast of the island of Gran Canaria, Spain). This would mean that with an additional total capital investment cost of 196 000 € (from the current scheme of Soslaires Canarias S.L.), and supposing an average membrane life expectancy of 10 years for the current state-of-the-art membranes, a net present value of 74 360.95 €, a profitability index of 1.3794, and a 224.4881% internal rate of return would be achieved. Graphical abstract Typical cost structure for RO seawater desalination. Image 1 Highlights • Several configurations of desalination plants based RES have been simulated. • Cost of water has been considered as the central element of the evaluation. • In case of carrying out the actions suggested COW would be reduced. [ABSTRACT FROM AUTHOR]

In the Brazilian semiarid region, groundwater usually have high concentration of salts. In order to make these waters suitable for consumption, desalinators have been installed in communities and rural settlements to meet the water demand. However, regardless of the efficiency of the membrane and the installed structure of the desalinators, the reverse osmosis system will produce the drinking water and also the residue with salt concentration higher than the previous water salinity. The sampling of water of wells, purified water, and saline reject was carried out in four expeditions, between October 2013 and November 2014, in seven water treatment facilities of communities and/or rural settlements in the west of Rio Grande do Norte State, Brazil. Determinations included the efficiency of reverse osmosis in water purification and parameters of quality: electrical conductivity, pH, cations and anions, sodium adsorption ratio, calcium/magnesium ratio and the influence of the Langelier saturation index and the Ryznar stability index on the recovery rate of reverse osmosis desalination systems. The results indicate that the average recovery rate for desalination systems was 32.11% in October/November of 2013; 52.42% in February/March of 2014; 41.41% in June/July of 2014, and 33.60% in October/November of 2014. [ABSTRACT FROM AUTHOR]

Fluoride contamination of groundwater has become a major concern worldwide, resulting in serious medical conditions such as dental and skeletal fluorosis. Consequently, the WHO recommends that drinking water should not contain more than 1.5 mg/l of fluoride. Various defluoridation techniques such as coagulation, reverse osmosis, activated alumina adsorption, and biosorbent adsorption have been developed. Adsorption through the activated alumina and biosorbent process is not cost effective and has regeneration problems, and the reverse osmosis process has the high initial cost which makes it unacceptable for developing countries. Coagulation is a commonly employed field technology for defluoridation, which involves the addition of aluminum salts, lime, and bleaching powder followed by rapid mixing, flocculation, sedimentation, and filtration but suffers from a limitation of high residual aluminum in treated water. This paper critically reviews the recent developments in the coagulation technique for defluoridation along with its comparison to other defluoridation techniques. The review describes the pertinent gaps in the process and throws open suggestions for extending research by citing the recent studies which may lead to the revival of the process. The description about the suspension of alumino-fluoro complexes that constitute a substantial part of the residual aluminum after alum treatment has been narrated in the paper that helps in a deeper understanding of the defluoridation mechanism. To make the process highly suitable for communities, appropriate technological interventions, such as converting it to a continuous mode of operation, replacing alum with poly-aluminum chloride (PAC), and attaching a micro-filtration unit in series of the existing process, can be done. Also, using PAC as a coagulant with sand filtration has to be considered for making the process more efficient. [ABSTRACT FROM AUTHOR]

Abstract As potable reuse guidelines and regulations continue to develop, the presence of N -nitrosamines is a primary concern because of their associated health concerns. In this study, bench-, pilot-, and full-scale tests were conducted to focus on the occurrence and treatment of N -nitrosomorpholine (NMOR) in United States (U.S.) potable reuse systems. Out of twelve U.S. wastewater effluents collected, ambient NMOR was detected in eleven (average = 20 ± 18 ng/L); in contrast, only two of the thirteen surface water and stormwater samples had NMOR. Across all of these samples maximum formation potential by chloramination produced an average increase of 3.6 ± 1.8 ng/L. This result underscores the need to understand the sources of NMOR as it is not likely a disinfection byproduct and it is not known to be commercially produced within the U.S. At the pilot-scale, three potable reuse systems were evaluated for ambient NMOR with oxidation (i.e., chlorination and ozonation), biofiltration, and granular activated carbon (GAC). Both pre-oxidation and biofiltration were ineffective at mitigating NMOR during long-term pilot plant operation (at least eight-months). GAC adsorbers were the only pilot-scale treatment to remove NMOR; however, complete breakthrough occurred rapidly from <2000 to 10,000 bed volumes. For comparison, a full-scale reverse osmosis (RO) potable reuse system was monitored for a year and confirmed that RO effectively removes NMOR. Systematic bench-scale UV-advanced oxidation experiments were undertaken to assess the mitigation potential for NMOR. At a fluence dose of 325 ± 10 mJ/cm2 , UV alone degraded 90% of the NMOR present. The addition of 5 mg/L hydrogen peroxide did not significantly decrease the UV dose required for one-log removal. These data illustrate that efficient NMOR removal from potable reuse systems is limited to RO or UV treatment. Highlights • Surface waters and wastewaters typically did not form NMOR under chloramination. • Ozone-BAC did not significantly remove NMOR during pilot-plant operation. • Limited sorption of NMOR was observed during GAC pilot-plant operation. • Low pressure UV removed NMOR at doses lower than those required for NDMA. • Significant removal of NMOR in potable reuse is limited to RO or UV treatment. [ABSTRACT FROM AUTHOR]

Abstract The robustness of reverse osmosis (RO) against polar organic micropollutants (MPs) was investigated in pilot-scale drinking water treatment. Experiments were carried in hypoxic conditions to treat a raw anaerobic riverbank filtrate spiked with a mixture of thirty model compounds. The chemicals were selected from scientific literature data based on their relevance for the quality of freshwater systems, RO permeate and drinking water. MPs passage and the influence of permeate flux were evaluated with a typical low-pressure RO membrane and quantified by liquid chromatography coupled to high-resolution mass spectrometry. A strong inverse correlation between size and passage of neutral hydrophilic compounds was observed. This correlation was weaker for moderately hydrophobic MPs. Anionic MPs displayed nearly no passage due to electrostatic repulsion with the negatively charged membrane surface, whereas breakthrough of small cationic MPs could be observed. The passage figures observed for the investigated set of MPs ranged from less than 1%–25%. Statistical analysis was performed to evaluate the relationship between physicochemical properties and passage. The effects of permeate flux were more pronounced for small neutral MPs, which displayed a higher passage after a pressure drop. Graphical abstract Image 1 Highlights • Strong size-passage correlation for neutral hydrophilic organics (log D <2). • Weaker size-passage correlation for moderately hydrophobic organics (log D >2). • Passage of cationic organics was higher than that of anions of comparable size. • Low permeate flux resulted in increased passage of small neutral polar organics. • Higher salt and organic passage observed for at least 5 h following a pressure drop. [ABSTRACT FROM AUTHOR]

Introduction: In this study, we investigated contaminants in sediments of reverse osmosis water systems in Iraqi households. These filters are imported from the US and Taiwan and are available in the Iraqi market. The rate of environmental pollutions in residues of the water filters was examined by measuring alpha particles emission rates and the concentration of heavy metals. Material and Methods: In this study, we measured the rate of alpha particles emission using CR-39 detector. Heavy elements were measured using an atomic absorption spectrometer. Results: The highest value of cadmium was found in Ghadeer district and the lowest cadmium value in Alswag district. The highest value of lead was found in Ghadeer district and the lowest in Aljameha. The emission rates of alpha particles were found to be the lowest in the sediments of Ghadeer district, and the highest values were found in Khan Almkhdhar. Conclusion: The average concentrations of dissolved Cd and Pb were higher than the safe limits for Iraq specifications and the world standard limit. [ABSTRACT FROM AUTHOR]

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The regeneration and recycling of discarded membranes are of great importance for extending the membrane lifespan, and thus, they are crucial to achieve the economic feasibility of the industrial scale membrane process. In this research, an end-of-life reverse osmosis (RO) membrane was analyzed, and a cleaning protocol and mechanism were investigated. Several chemical agents were optimized, including acid (H2SO4), base (NaOH), metal-chelating agents (Na2-EDTA), surfactants (SDS), oxidizing agents (KMnO4), and their combinations. The results showed that good regeneration of the membrane can be achieved after the membrane was cleaned by a KMnO4 + NaOH solution, followed by NaHSO3. To achieve a high cleaning efficiency, the effects of oxidant concentration, cleaning time, and solution pH were studied. The optimum cleaning protocol was a 0.5% (w/v) KMnO4 + 0.2% (w/v) NaOH solution, followed by NaHSO3; and the optimum cleaning time was 60 min, allowing for a cleaning efficiency of 5.87. The experimental results showed that the cleaning procedure could be divided into three stages and that both the KMnO4 concentration and pH can control the cleaning stage. Based on economic feasibility, controlling the solution pH with low KMnO4 concentrations could lead to the transformation of membranes into target recycled membranes (such as reverse osmosis, nanofiltration, and ultrafiltration). [ABSTRACT FROM AUTHOR]

Abstract Potable water production is an essential but energy intensive process and usually requires many chemicals. Furthermore, small-scale plants are not yet available because of the problems associated with downscaling the thermal evaporation or reverse osmosis processes. Freeze crystallization is an alternative, especially for the self-sufficiency of potable water in remote areas. The use of a crystallizer and a separate press in combination with a perforated pressing mold has shown that the desalination of saltwater can be achieved by pressing the ice only; no additional washing step is necessary. A pressing force of 37.4 kN (100 bar) and a holding time of 180 s were found to be sufficient. Therefore, these parameters were used to design a single-step plant, which also showed good results in the case of ion expulsion. Nonetheless, the variation in the test parameters showed their influence on crystal growth and crystal purity and demonstrated the need to find the optimal design parameters for future continuously operating systems. Highlights • Development of a single-step plant continuously producing potable water • Small-scale plant for self-sufficient supply in remote areas • Comparison of Nusselt correlations for a scraped surface crystallizer • Prove of pressing as post-treatment step for freeze desalination [ABSTRACT FROM AUTHOR]

Abstract Due to the improved dilution of draw streams, employing pressure-assisted forward osmosis (PAFO) to the hybrid system of forward osmosis (FO) followed by reverse osmosis (RO) for seawater desalination has been expected to reduce the overall economics. However, replacing FO with PAFO causes an additional energy cost in the seawater dilution step which inevitably leads to a question that PAFO-RO hybrid is truly an economically beneficial option. More importantly, though serial connection of FO elements improves the dilution of initial draw water, this economic benefit is also compensated with the additional membrane. To rationalize its overall performance and economic benefit, thorough performance and economic evaluations were conducted based on actual pilot-scale PAFO operations for serial connection of up to three 8040 FO elements. The results showed the FO-RO hybrid is not an economically feasible option unless a significant unit FO element cost cut-down is guaranteed. Meanwhile, PAFO-RO showed benefits with regards to target RO recovery and unit FO element cost, particularly when two FO elements are serially connected (SE2). It was found that PAFO-RO, indeed, has higher economic potential than FO-RO. A graphical overlapping method suggested in this work can help determine optimal serial configuration and operating conditions of PAFO-RO. Graphical abstract Unlabelled Image Highlights • Significant impact of initial draw flowrate and hydraulic pressure on the PAFO-RO economics • Hydraulic pressure dependence of FO membrane element performance • Drastic pressure-drop in the draw channel of the last element in serial configuration • Target RO recovery and unit FO element cost in PAFO-RO hybrid are important for economics [ABSTRACT FROM AUTHOR]

Abstract The coupling of thermal (multi stage flash, MSF) and membrane processes (reverse osmosis, RO) in desalination systems has been widely presented in the literature to achieve an improvement of performance compared to an individual process. However, very little study has been made to the combined multi effect distillation (MED) and reverse osmosis (RO) processes. Therefore, this research investigates several design options of MED with thermal vapor compression (MED_TVC) coupled with RO system. To achieve this aim, detailed mathematical models for the two processes are developed, which are independently validated against the literature. Then, the integrated model is used to investigate the performance of several configurations of the MED_TVC and RO processes in the hybrid system. The performance indicators include the fresh water productivity, energy consumption, fresh water purity, and recovery ratio. Basically, the sensitivity analysis for each configuration is conducted with respect to seawater conditions and steam supply variation. Most importantly, placing the RO membrane process upstream in the hybrid system generates the overall best configuration in terms of the quantity and quality of fresh water produced. This is attributed to acquiring the best recovery ratio and lower energy consumption over a wide range of seawater salinity. Highlights • Detailed mathematical models for MED-RO hybrid process are developed. • The performance of different superstructures of the hybrid process is simulated. • Sensitivity analysis aids to detect the best structure based on performance factors. • Hybrid configuration with RO upstream achieves the best performance indicators. [ABSTRACT FROM AUTHOR]

Abstract A hybrid system consisting of RO (reverse osmosis) and SE (Stirling engine) was proposed to utilize the moderate temperature heat for the brackish water desalination. The performance of two configurations was systematically investigated. Config. II employs ERD (energy recovery device) to harvest the residual pressure energy in outlet feed solution for the pre-pressurization of inlet feed solution while Config. I does not. Impacts of substance temperature in the SE heater and RO hydraulic pressure difference on the fresh water recovery ability and energy consumption were investigated. Results indicated that Config. I presents the highest recovery rate of 17.3% while Config. II gets the largest fresh water production of 34.2 L/h. As to the energy consumption, a lowest specific energy consumption of 2.5 kW · h / m 3 and specific thermal energy consumption of 35.9 MJ/m 3 were achieved in Config. II, which exhibits much more effectively compared to those obtained in Config. I. Furthermore, the performance comparison under the ideal and non-ideal SE models was also conducted. Highlights • High flow rate can reduce the osmotic pressure difference aside membrane. • High hydraulic pressure difference is beneficial for system performance. • Energy recovery device reduces the specific thermal energy consumption by 52%. • Energy consumption can be reduced up to 35% with a more efficient Stirling engine. [ABSTRACT FROM AUTHOR]

Membrane technology has become a common separation technology over the past decennia. Membranes are used more and more for the production of drinkable water from groundwater, surface water and wastewater. Membranes are now competitive versus conventional techniques. Desalination is predominantly used to eradicate the problem of water scarcity. The sustainability of all desalination processes depends mainly on the reduction of energy costs (production cost) and the increase in water recovery. Forward osmosis and membrane distillation are emerging technologies for sustainable desalination. Here we review membrane processes of forward osmosis and membrane distillation and the advancements in membrane material and modules. We also discuss the capability of membrane distillation in treating highly concentrated aqueous solutions derived from other desalination processes. Furthermore, the advancements in fabrication of high-performance membrane is reviewed and the performance of different membranes and optimization of membrane distillation process are summarized. [ABSTRACT FROM AUTHOR]

Water shortage is a major problem facing the world today, although 70% of the earth is covered with water. With 95% of this water in seas and oceans, man has to find the most energy-efficient way of desalination for sustainable freshwater supply. Conventional desalination technologies such as reverse osmosis and thermal distillation involve large amounts of energy, especially for high salt rejection. In comparison, the discovery of two-dimensional materials such as graphene and its structural analogs boron nitride and molybdenum disulphide (MoS2) has fostered been tremendous progress for energy-saving desalination using nanopores of these materials. This article reviews the recent developments in this technology with experimental and molecular simulation literature survey over the past few years. It explains the role of nanopores in desalination in terms of structure, energy, cost-effectiveness and process efficiency. [ABSTRACT FROM AUTHOR]

Upgrading existing wastewater treatment plants (WWTPs) is a more challenging task than constructing new plants. The aim is usually to overcome overloading and to reduce pollution concentrations in the effluent. There are various methods that can be used to upgrade WWTPs. This article reviews some of the methodologies, such as inserting new tanks as additional treatment steps and modifying the WWTP by introducing new technologies. A number of effective technologies are reviewed in terms of their basic concepts, operational conditions, and treatment performances. Examples of WWTPs in China that have been successfully upgraded using these technologies are also highlighted. [ABSTRACT FROM AUTHOR]

In this article the solar energy is utilized to generate needed steam for a power generation cycle which in turn provides the required power of a RO system. Optimization was carried out on two levels. First, Economizer, Evaporator, Super heater in power generation cycle as well as the type of membrane, PV numbers and series were optimized. In addition, the optimum design of a solar field for the system was carried out and the collector specifications, number of branches, and flow rate were designed. Based on the first level, optimization was designed to reduce costs and increase the permeate water production and reduction in costs and pressure drop of the solar filed. Preheating of the RO feed water had different effects on the production of fresh water at various concentrations. For feed water with constant flow rate and concentration of 45 000 ppm, the maximum rate of permeate flow was obtained at 26°C, while for concentration of 35 000 ppm, the maximum permeate flow rate was achieved at 33°C. By using 5 parallel elements SW30XLE‐400 for RO system, in the optimized condition, permeate flow rate and recovery were 9494.19 (m3/day) and 59.5%, respectively. In this condition, the unit production cost of water was 0.6046 ($/m3). In this study, a reverse osmosis system using feed water preheating system and solar collectors was investigated. The purpose of this study was designing a solar field for an optimized system including power plant, heat exchanger, and RO system. In order to achieve the optimized design, all involved systems except the solar field were optimized simultaneously. [ABSTRACT FROM AUTHOR]

The cleaning efficiency of reverse osmosis (RO) membranes inevitably fouled by organic foulants depends upon both chemical (type of cleaning agent, concentration of cleaning solution) and physical (cleaning time, flowrate, temperature) parameters. In attempting to determine the optimal procedures for chemical cleaning organic-fouled RO membranes, the design of experiments concept was employed to evaluate key factors and to predict the flux recovery rate (FRR) after chemical cleaning. From experimental results and based on the predicted FRR of cleaning obtained using the Central Composite Design of Minitab 17, a modified regression model equation was established to explain the chemical cleaning efficiency; the resultant regression coefficient (R2) and adjusted R2 were 83.95% and 76.82%, respectively. Then, using the optimized conditions of chemical cleaning derived from the response optimizer tool (cleaning with 0.68 wt% disodium ethylenediaminetetraacetic acid for 20 min at 20°C with a flowrate of 409 mL/min), a flux recovery of 86.6% was expected. Overall, the results obtained by these experiments confirmed that the equation was adequate for predicting the chemical cleaning efficiency with regards to organic membrane fouling. [ABSTRACT FROM AUTHOR]

BACKGROUND With the rapid development of nuclear energy in China, a broad spectrum of low level radioactive wastewater (LLRW) has been generated and must be purified prior to discharging to the environment. Reverse osmosis (RO) has been proved an effective technology in the treatment of high boron‐containing LLRW in nuclear power plants (NPPs). However, there is always a large amount of salts in the LLRW as background compounds. It is important to understand the influences of salts on the rejection of nuclides and boron. RESULTS: A lab‐scale cross‐flow membrane filtration unit was used. With the increase of ion concentration, the permeate flux decreased by 15% and 25% for BW30XFR and LE, respectively. Nuclides rejection increased by 2–8% and boron rejection increased by 5–10% when raising salts concentration to 2.5 mmol L–1. Divalent ions such as Mg2+ and SO42− had a stronger impact than monovalent ions such as Na+ and Cl− on nuclides and boron rejection. CONCLUSION: Increasing ion strength promoted the rejection of trace nuclides and boron, but at the cost of membrane flux loss. The results of dealing with simulated wastewater would give us information to better understand how to treat real radioactive wastewater. © 2018 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

The spreading of reverse-osmosis desalinated seawater (DSW) in the Israeli coastal aquifer was studied using groundwater modeling and stable water isotopes as tracers. The DSW produced at the Hadera seawater reverse-osmosis (SWRO) desalination plant is recharged into the aquifer through an infiltration pond at the managed aquifer recharge (MAR) site of Menashe, Israel. The distinct difference in isotope composition between DSW (δ18O = 1.41 ‰; δ2H = 11.34 ‰) and the natural groundwater (δ18O = - 4.48 ‰ to - 5.43 ‰; δ2H = - 18.41 ‰ to - 22.68 ‰) makes the water isotopes preferable for use as a tracer compared to widely used chemical tracers, such as chloride. Moreover, this distinct difference can be used to simplify the system to a binary mixture of two end-members: desalinated seawater and groundwater. This approach is validated through a sensitivity analysis, and it is especially robust when spatial data of stable water isotopes in the aquifer are scarce. A calibrated groundwater flow and transport model was used to predict the DSW plume distribution in the aquifer after 50 years of MAR with DSW. The results suggest that after 50 years, 94 % of the recharged DSW was recovered by the production wells at the Menashe MAR site. The presented methodology is useful for predicting the distribution of reverse-osmosis desalinated seawater in various downstream groundwater systems. [ABSTRACT FROM AUTHOR]

Abstract Multi-Stage-Flash (MSF) Distillation is a large scale sea water desalination plants that are widely used in Gulf area. Most installations of MSF plants are operated in cogeneration with a power plant. Also, MSF plants can be combined with other desalination technologies such as Nano filtration and Reverse osmosis (RO) in new installation. However, the new MSF plants are recommended, where large amounts of cheap or waste energy are available (e.g. conventional power plants). Also, the plant location is playing an important role for economic operation due to cold or hot weather conditions. The present study is applied on the seawater multi-stage flash (MSF) desalination plant that is currently under operation in Al-Khafji operations plant located in Saudi Arabia (KSA). The plant contains 20 evaporator stages at capacity of 600,000 gallon per day (GPD). The presented operating data has been collected during a visit of the plant. The objective is to present field results of this MSF plant operation in order to measure and evaluate the performance at 70% and 100% capacity during summer (case-1) and winter (case-2) operation. Then, the plant overall performance indicators are presented to compare between the studied two cases in terms of specific cooling water flowrates and performance ratio. Finally, the seasonal performance variation of the plant is included. The results showed that, for the same plant output, the main cooling water flow rates is decreased from 47.1% to 20.1% for case-1 and case-2 respectively, which in turns directly reduces the pumping power by the same ratio. Consequently, running the large scale thermal desalination MSF plant in cold regions is more economic than hot regions for pumping power energy saving considerations. This is to be considered in future large scale desalination plants. [ABSTRACT FROM AUTHOR]

Abstract Ensuring the biological stability of drinking water is essential for modern drinking water supply. To understand and manage the biological stability, it is critical that the bacterial growth in drinking water can be measured. Nowadays, advance treatment technologies, such as reverse osmosis (RO), are increasingly applied in drinking water purification where the produced water is characterized by low levels of nutrients and cell counts. The challenge is, therefore, how to measure the low bacterial growth potential (BGP) of such ultra-pure water using the available methods which were originally developed for conventionally treated drinking water. In this study, we proposed a protocol to assess BGP of ultra-pure drinking water produced by RO and post-treatment (including remineralization). Natural bacterial consortium from conventional drinking water was added to all water samples during this study to ensure the presence of a wide range of bacterial strains. The method development included developing an ultra-pure blank with high reproducibility to lower the detection limit of the BGP method (50 ± 20 × 103 intact cells/mL) compared with conventional blanks such as bottled spring water, deep groundwater treated by aeration and slow sand filtrate of surface water supply. The ultra-low blank consists of RO permeate after adjusting its pH and essential mineral content under controlled laboratory conditions to ensure carbon limitation. Regarding the test protocol, inoculum concentrations of >10 × 103 intact cells/mL may have a significant contribution to the measured low levels of BGP. Pasteurization of water samples before measuring BGP is necessary to ensure reliable bacterial growth curves. The optimized method was used to assess BGP of ultra-pure drinking water produced by RO membranes and post-treatment (including remineralization), where the BGP has decreased more than 6-fold to a level of 90 ± 20 × 103 intact cells/mL compared with conventionally treated water (630 ± 70 × 103 intact cells/mL). Graphical abstract Image 1 Highlights • The detection limit of bacterial growth potential method was significantly lowered. • Inoculum has a significant influence on bacterial growth potential measurements. • Pasteurization is necessary before measuring bacterial growth potential. • RO permeate has lower bacterial growth potential than conventional drinking water. [ABSTRACT FROM AUTHOR]

Abstract This work addresses the comparison of seawater desalination by the RO-PRO hybrid system with open-loop and closed-loop configurations regarding normalized specific energy consumption (NSEC) using a model-based optimization approach. The NSECs in both configurations are minimized by solving a constrained nonlinear optimization model so that the comparison is addressed based on their best conditions. The underlying impacts of membrane area, pretreatment energy of feed water, feed water concentration and internal concentration polarization on system performances are systemically investigated. It is shown that the optimization program gives priority to the closed-loop configuration due to its advantages in energy-saving and cost reduction at an adequate membrane area (γ tot ≥ 1.0) and low water recovery (Y ≤ 0.5). It highlights the significance of an essential prerequisite γ tot , min > π 0 Y /(σ ∆π PRO ¯) for the operation of a closed-loop configuration. Nevertheless, the analysis of internal concentration polarization effect further indicates that the closed-loop configuration may be vulnerable to the variation of operating and feed conditions and the degradation of membrane in practice. Graphical abstract Unlabelled Image Highlights • Open-loop and closed-loop RO-PRO systems are compared using a model-based optimization approach. • The coupled behaviour among membrane properties, operating conditions, and feed conditions are revealed. • Closed-loop system is advantageous in terms of energy-saving and cost reduction at γ tot ≥ 1.0 and Y ≤ 0.5. • There is a prerequisite γ tot , min > π 0 Y /(σ ∆π PRO ¯) for the operation of closed-loop system. [ABSTRACT FROM AUTHOR]

Abstract In remote areas, the vital need is production of drinking water and the provision of electrical energy for housing. Often the only sources of energy are based on renewable energies with storage to create a local micro-network. This paper investigates the optimal design of embodied energy for water treatment by reverse osmosis, coming from brackish water (6 g/l) and with a double storage that is done in a drinking water tank and in batteries for electricity. Taking account wind and photovoltaic potentials in such system for assessing its performance implies its simulation over long periods of time. This can drastically increase the CPU time cost related to the design step, especially if the system energy management and sizing are sequentially optimized into a two-level optimization process. In order to solve this problem and accelerate the system simulation, meta-models are used for representing the system constraints and objectives. These meta-models are built by the design of experiments method. From realistic data, the results of this paper show that the contribution of the meta-models divides by two or three the design time by obtaining values of the sizing parameters close to the dynamic simulator depicting the real operation of the whole system. Highlights • To propose a methodology for optimal sizing of a freshwater and electricity production system, for an isolated site, from renewable energies and a double storage in a battery and in the water tanks (brackish and freshwater). • This approach is applied to the total life cycle of the embodied energy (EE) and not of cost (the EE models are given in the paper). • The motor pump and reverse osmosis unit are modeled with a single parameter that depends on the flow rate per day (to limit the number of parameters to be optimized to facilitate the convergence of the optimization algorithm). • To compare the optimization results obtained with a dynamic simulator taking into account the meteorological data over one year with meta-models obtained by design of experiments. • The obtaining of these meta-models is one of the main highlights of this paper (obtaining the database, the equation forms of the meta-models,...). [ABSTRACT FROM AUTHOR]

Abstract Desalting brines from Reverse Osmosis (RO) plants is one of the most promising applications of Membrane Distillation (MD) systems. The development of accurate models to predict MD system performances plays a significant role in the design of this kind of industrial applications. In this paper, a commercial-scale Permeate-Gap Membrane Distillation (PGMD) module was modelled by means of two different approaches: Response Surface Methodology (RSM) and Artificial Neural Networks (ANN). Condenser inlet temperature, evaporator inlet temperature, feed flow rate and feed water salt concentration were selected as inputs of the model, while permeate flux and Specific Thermal Energy Consumption (STEC) were chosen as responses. The prediction abilities of both RSM and ANN models were compared with further experimental data by using the Analysis of Variance (ANOVA) and the Root Mean Squared Error (RMSE). The results show that the ANN model is able to predict in a more precise way the behaviour of the module for the whole range of input variables. Thus, ANN model was used to find the optimal operating conditions, for the module operating at feed water salinity of 70 and 105 g/L, concentrations that can be reached when desalting RO brines. Highlights • Commercial-scale permeate-gap membrane distillation evaluated for high salinity • Prediction models based on RSM and ANN have been developed from the experimental data. • A comparison between the two modelling tools is provided. • 3D response surfaces showing the influence of the feed salinity are presented. • The operation of MD pilot unit for desalting RO brines is optimized. [ABSTRACT FROM AUTHOR]

In the current paper, a suggested process of coupled ultrafiltration (UF), nanofiltration (NF), and reverse osmosis (RO) to produce isotonic solution (IS) and drinking water from coastal well water was investigated. Due to its high fouling potential, the feed water was pretreated using UF. Results showed that UF eliminates almost the totality of natural organic matter (NOM), and a relatively high portion of calcium (calcium rejection ∼75%) due to the complex Ca-NOM formed. To understand the fouling mechanism, previously developed mathematical models and equations were adopted. It was shown that the fouling mechanism for UF fits the blocking pores model. For NF, the extended model using cross-flow mode showed a slight difference compared to UF (No compression cake phase). It was concluded that, with some experimental precautions, fouling mechanism of the NF membrane used is internal pore blocking mechanism. Due to its attractive quality, the brine of NF was used to produce drinking water by RO treatment. The energy consumption of the UF-NF-RO system was investigated for different operating conditions. Finally, the permeate of the UF-NF process was compared to a commercialized IS. It was found that the two solutions revealed a remarkable similarity. However, a specific post-treatment should be added to the process to accomplish the pharmaceutical exigencies of IS. [ABSTRACT FROM AUTHOR]

Energy recovery device (ERD) is a critical power component in seawater reverse osmosis (SWRO) desalination system. In this study, the energy transfer and flow characteristics for an innovative integrated energy recovery and pressure boost device (IERPBD) are investigated. The IERPBD which consists of a rotary pressure exchanger (RPE) and an axial piston type booster pump (APBP) is introduced in Section 2. To optimize both the structure parameters and working conditions of IERPBD, a series of three-dimensional (3D) CFD simulations are carried out. The CFD simulations for the RPE with port plate silencing grooves are conducted with a set of operating conditions through orthogonal designed theory. It should be noted that the leakage through the lubricating gaps of valveport plate, fluid compressibility effect and cavitation damage are considered in the simulation. And partial numerical results are validated by comparison with the results from other research groups. The mixing process, pressure distribution, components distribution, leakage flow characteristics and related characteristic parameters of RPE are presented in Section 3. And then the optimal parameters of RPE with a duct diameter of 10 mm, duct length of 70 mm, 12 ducts with fresh seawater flow of 10.8 L/ min were used to design the IERPBD. The energy transfer and flow characteristics of IERPBD were also presented with different gap heights of the valve-port plate interface. The simulation results turned out that when the lubricating gap height of valve-port plate changes from 5 μm to 20 μm, the flow ripple rate of RPE could increase from 6.15% to 36.13%, whereas the energy recovery efficiency of RPE could decrease from 97.2% to 49.8%. Therefore, a well-designed lubricating gap of valve-port plate could improve both energy transfer and flow characteristics of IERPBD. This research will lay the foundation for the further development of high efficiency and low fluid noise IERPBD. [ABSTRACT FROM AUTHOR]

This research investigates the fouling behavior of reverse osmosis (RO) membranes in an integrated membrane bioreactor (MBR)-RO system for landfill leachate treatment. In a long-term operation under natural alkaline condition (pH 8.0–8.5), a full-scale integrated MBR-RO system achieved high treatment efficiencies (>95%) but suffered RO membrane fouling as a result of calcium scaling. Specifically, in the study, the mixed liquor pH in MBR was varied between 5.5, 6.5, 7.5, and 8.5, and the effect on RO membrane fouling examined in laboratory-scale experiments. The results showed that pH influenced the removal of dissolved organic matters in the MBR and the characteristics of MBR permeates. At pH 5.5, the deposition of protein-like substances substantially reduced the RO flux, and calcium scaling on the RO membrane was clearly visible under pH 8.5. The RO flux slightly decreased under pH 6.5 and 7.5. The optimal pH for treating landfill leachate using the integrated MBR-RO system was between 6.5 and 7.5. [ABSTRACT FROM AUTHOR]

Membrane distillation (MD) is a thermal separation process which possesses a hydrophobic, microporous membrane as vapor space. A high potential application for MD is the concentration of hypersaline brines, such as e.g. reverse osmosis retentate or other saline effluents to be concentrated to a near saturation level with a Zero Liquid Discharge process chain. In order to further commercialize MD for these target applications, adapted MD module designs are required along with strategies for the mitigation of membrane wetting phenomena. This work presents the experimental results of pilot operation with an adapted Air Gap Membrane Distillation (AGMD) module for hypersaline brine concentration within a range of 0–240 g NaCl /kg solution. Key performance indicators such as flux, GOR and thermal efficiency are analyzed. A new strategy for wetting mitigation by active draining of the air gap channel by low pressure air blowing is tested and analyzed. Only small reductions in flux and GOR of 1.2% and 4.1% respectively, are caused by air sparging into the air gap channel. Wetting phenomena are significantly reduced by avoiding stagnant distillate in the air gap making the air blower a seemingly worth- while additional system component. [ABSTRACT FROM AUTHOR]

Capacitive deionization (CDI) is an electrochemical ion removal technique that could offer a lower energy or more selective alternative to reverse osmosis for water treatment applications. Over a dozen CDI cell architectures have been developed, but few studies have directly compared these designs for performance metrics such as ion adsorption rate and energy efficiency. Two of the most popular cell architectures include flow-by CDI, in which a feed stream flows parallel to two charged porous electrodes, and flow-through electrode CDI, in which the feed stream flows perpendicular to the electrodes. In this study, flow-by and flow-through CDI architectures were compared using commercially available electrode materials. Experimentally observed salt adsorption capacity (SAC), average salt adsorption rate (ASAR), and charge efficiency (Λ) was then compared to theoretical models over a range of voltage conditions (0.2–1.2 V), charge cycle times (1–60 min), and flow rates (10–30 mL min - 1 ). Cell architecture affected the SAC, ASAR, Λ, electrode stability, and oxidation rates for a given electrode material. Flow-by CDI tended to have higher SAC and better charge efficiency than flow-through CDI, yet flow-through CDI demonstrated a higher ASAR, particularly for shorter half-cycle times. [ABSTRACT FROM AUTHOR]

Membrane distillation (MD) is considered as a key technology for desalination applications. It shows indeed numerous advantages compared to reverse osmosis and other desalination processes (e.g. thermal driving force, no osmotic pressure effect on membrane fluxes). Nevertheless, this technology still presents some issues, most notably due to pore wetting effects. This study proposes the use of a thin, self-standing dense membrane in place of microporous materials as a solution to avoid wetting in MD for water desalination. In a first step, a membrane contactor model is developed based on mass and energy balances and the simulations are validated using experimental results obtained on hollow fiber modules with microporous membranes. A comparative performance analysis is then achieved between a porous and a dense membrane module. A parametric study on the influence of dense membrane thickness and water permeability shows that a two fold increase in water flux, without significant impact on energy efficiency, is potentially achievable with thin and permeable dense materials compared to microporous membranes. Guidelines for the design of high-performance dense membrane modules for MD are finally proposed. [ABSTRACT FROM AUTHOR]

Desalination of geothermal brackish water by membrane distillation (MD) provides a low recovery rate, but integrating MD with reverse osmosis (RO) can maximize the production rate. In this study, different design configurations of a hybrid system involving brine recycling and cascading are studied via simulations, and the performance improvement due to the process integration is substantiated via the increased recovery rate and reduced specific energy consumption. Brine recycling is also found to improve the recovery rate considerably to 40% at an energy cost of 0.9 $/m3. However, this achievement is only valid when the final brine is recycled to the RO feed: when the final brine is recycled to the MD feed, the overall performance degrades because the recycled brine cools the feed and causes a serious reduction in the driving force and the consequent production rate. Configuring the hybrid system in multiple stages connected in series increases the recovery rate to 90% and reduces the specific energy consumption to 0.9 MJ/kg. Although the specific energy cost increases dramatically because external inter-stage heating is implemented, using a free energy source (such as a geothermal or waste-energy source) for inter-stage heating could provide the optimum configuration. [ABSTRACT FROM AUTHOR]

Osmotic microbial fuel cells (OsMFCs) combine the merits of microbial fuel cell (MFC) and forward osmosis (FO) for simultaneous contaminant removal, electricity generation, and high-quality water extraction. As an FO based technology, reverse solute flux (RSF) is one of the key challenges for its operation. Herein, RSF was converted into a positive effect on the system performance by using NaHCO 3 solution as a draw solution (DS)/catholyte. It was found that reverse-fluxed NaHCO 3 helped buffer the anolyte pH and thus enhance electricity generation, compared to the OsMFC using the NaCl DS/catholyte. At the same concentration, the NaHCO 3 DS/catholyte achieved a higher Coulomb production of 1349.2 ± 80.3 C and higher anolyte pH of 6.48 ± 0.19 than those of the NaCl DS/catholyte. At the same conductivity, the NaHCO 3 DS/catholyte exhibited better electricity generation performance with a comparable recovered water volume of 417.7 ± 13.7 mL to that of the NaCl DS/catholyte. As the NaHCO 3 concentration increased from 0.1 M to 0.75 M, the OsMFC electricity generation was enhanced due to the increased RSF from 19.2 ± 2.3 to 210.8 ± 17.5 mmol m −2 h −1 . In the anode, 92.0 ± 0.8% to 97.1 ± 0.9% of reverse-fluxed NaHCO 3 was used to neutralize protons. These results have demonstrated a new strategy that uses the bicarbonate migration driven by both a concentration gradient and electricity generation to successfully raise the alkalinity of the anolyte towards enhancing electricity generation. [ABSTRACT FROM AUTHOR]

Petroleum compounds appear in the surface and ground water in increasing concentrations. This is due to the emergence of new risks associated with the production, transport, use, and disposal of hazardous waste substances. These pollutants have a strong toxic impact on living organisms, hence they should be removed using the most effective methods. The paper deals with the removal of petroleum compounds from water using a combination of classical and membrane methods. Coagulation and reverse osmosis were applied. The study used synthetic water, that is, distilled water enriched with a mixture of diesel fuel and gasoline. [ABSTRACT FROM AUTHOR]

To obtain higher concentration of sodium chloride than in reverse osmosis (RO), the hybrid RO–nanofiltration (NF) system was applied. The use of RO retentate pressure as a driving force in NF decreased the energy consumption in the brine concentration process and increased RO permeate recovery. In such a hybrid system, NF could be regarded as an alternative method of energy recovery. Five NF membranes were tested on the synthetic sodium chloride solution, conducted at 40 bar, with highest rejection coefficients 31.3%. Selected membranes were tested at the higher pressure (50, 55 and 60 bar) on the synthetic sodium chloride solution and on the coal-mine brine RO retentate (60 bar). Based on the obtained results, energy consumption in RO–NF–vapour compression (VC) system was estimated and compared with the RO–VC system. The energy consumption in the RO–NF hybrid system with VC (123.3 kWh/m³ of brine with 290 g/dm³ NaCl) was lower than in the currently used RO–VC system (213.2 kWh/m³ of brine with 290 g/dm³ NaCl without energy recovery and 204.6 kWh/m³ of brine with 290 g/dm³ NaCl with energy recovery). [ABSTRACT FROM AUTHOR]

The performance of a dynamic vibratory membrane system for the recovery of usable water from soluble coffee processing wastewater has been investigated. Coffee wastewater is a complex food and beverage wastewater consisting of a variety of inorganic and organic constituents and dissolved and suspended solids. Manufacturing processes require high volumes of water, which leads to significant generation of wastewater. Effective design and scale-up of a recovery process are necessary to improve the sustainability of water draw for production. Rejections of COD, turbidity, and conductivity were observed to determine the purity of water recovered. A variety of membranes were initially screened for effective performance; a thin-film composite nanofiltration and a thin-film composite reverse osmosis membrane were selected for further studies. Process parameter studies for these membranes evaluated the effect of time, pressure, and vibration (shear). Steady-state flux was enhanced when vibration was introduced by factors of 4.5 and 1.6 when processing with the nanofiltration and reverse osmosis membranes, respectively. COD and turbidity rejection were above 97% for both the nanofiltration and reverse osmosis membranes in vibratory filtration. Conductivity rejection was 75 and 99% for the nanofiltration and reverse osmosis membranes, respectively, in vibratory filtration. The nanofiltration membrane was tested in a high-recovery simulation run and produced high flux at 85% total permeate recovery, indicating commercial-scale design is feasible. [ABSTRACT FROM AUTHOR]

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Background: Application of the point-of-use water treatment (POU-WT) systems has consistently increased during the last decade in Iran. In this study, the qualitative performances of reverse osmosis-based POU devices in selected cities of Iran were investigated. Methods: This applied- descriptive study was conducted in three cities of Tehran, Rasht, and Ahvaz in 2016 (selected based on the level of POU devices sale index in three phases). After choosing the most popular five brands of six stages POU devices, 360 water sampling zones and POU consumer households of the selected cities were measured. Also, the awareness of the consumers about POU-WT systems selection and performance was investigated through a designed questionnaire. Results: The qualitative parameters in the three cities were acceptable (p < 0.05) for tap water (except for EC in Ahvaz), the output water were as follows: pH = 6.05–7.5, EC = 49.8–58.2 μs/cm, TOC = 0.01–0.23 mg/L and Nitrate = 0.52–4.5 mg/LNO3 (lower or within the range of regulatory limits), Total Hardness = 33–41.5 mg/L and Fluoride = 0.01–0.23 mg/L (which were lower than the admissible limit, with p < 0.05), HPC values were in the range of 543–676 CFU/mL, which exceeded the regulatory level. Results of ANOVA analysis showed significant differences between the selected cities. The results of the questionnaire survey showed that the dissatisfaction of tap water quality and health-related concerns were the two main reasons for household POU-WT systems; awareness levels of 64% of these households about the performances of their POU systems were weak. Also, social media were mostly used by POU-WT users for brand selected. Conclusion: Based on the results of the tap-water quality application of POU-WT systems are not recommended in Tehran and Rasht, and regarding the outputs of these systems, side effects of softened water, lack of Fluoride and a remarkable increase of the number of bacteria should be considered. In Ahvaz, application of POU-WT systems can decrease the health-related problems and it is necessary to increase the access to read POU-WT efficiency information for the consumers. [ABSTRACT FROM AUTHOR]