Low Pressure Reverse Osmosis Research Articles

Effect of volumetric concentration factor on virus removal for low-pressure reverse osmosis membrane in drinking water production: A study on different scales

Reverse osmosis membranes are intended to constitute a complete physical barrier against nanometric-sized pathogens such as enteric viruses. Literature describes that low-pressure reverse osmosis achieves high viral removal rates (above 5 log), surpassing those of ultrafiltration (1 to 3 log). However, these studies often used individual viruses and high feed viral concentrations (above 109 virus L-1), greater than typical viral concentrations present in the environment like groundwater, to promote virus detection in the permeate. These high concentrations can promote viral aggregation, potentially affecting the observed retention. This work evaluates the simultaneous elimination of three viruses during the production of drinking water by low-pressure reverse osmosis: two enteric viruses (adenovirus 41 and coxsackievirus-B5) and bacteriophage MS2, a widely used virus surrogate in the literature. The permeates produced by low-pressure reverse osmosis were concentrated to allow virus detection in permeate at lower feed concentrations (106 virus L-1) while staying above the limits of detection and quantification. Experiments were carried out on two pilot plants of different scales (laboratory and semi-industrial) to assess the potential effect of the number of membranes and O-rings on virus retention. The effect of the volume concentration factor on low-pressure reverse osmosis efficiency was evaluated for each scale. Results indicate an average viral reduction of 6 log (up to 7 log), regardless of the size of the virus and/or the scale of LPRO pilot. For the semi-industrial scale, better retention was observed as the volume concentration factor increased. However, viruses were still present in the permeate for each scale (even if close to the detection limit), indicating that retention was not complete. At the same feed viral concentrations, the number of viruses recovered in the semi-industrial scale permeates was higher than in the laboratory scale. A 24-fold greater number of membranes and O-rings used for the semi-industrial scale showed that micro-leaks through O-rings could be responsible for the passage of viruses into the permeate.

Integration of Full-Size Graywater Membrane-Aerated Biological Reactor with Reverse Osmosis System for Space-Based Wastewater Treatment.

To date, life support systems on the International Space Center (ISS) or those planned for upcoming moon/Mars missions have not included biological reactors for wastewater treatment, despite their ubiquitous use for the treatment of terrestrial wastewaters. However, the new focus on partial gravity habitats reduces the required complexity of treatment systems compared with those operating in micro-gravity, and the likely addition of large-volume wastewaters with surfactant loads (e.g., laundry and shower) makes the current ISS wastewater treatment system inappropriate due to the foaming potential from surfactants, increased consumable requirements due to the use of non-regenerative systems (e.g., mixed adsorbent beds), the complexity of the system, and sensitivity to failures from precipitation and/or biological fouling. Hybrid systems that combine simple biological reactors with desalination (e.g., Reverse Osmosis (RO)) could reduce system and consumable mass and complexity. Our objective was to evaluate a system composed of a membrane-aerated bioreactor (MABR) coupled to a low-pressure commercial RO system to process partial gravity habitat wastewater. The MABR was able to serve as the only wastewater collection tank (variable volume), receiving all wastewaters as they were produced. The MABR treated more than 20,750 L of graywater and was able to remove more than 90% of dissolved organic carbon (DOC), producing an effluent with DOC < 14 mg/L and BOD < 12 mg/L and oxidizing >90% of the ammoniacal nitrogen into NOx-. A single RO membrane (260 g) was able to process >3000 L of MABR effluent and produced a RO permeate with DOC < 5 mg/L, TN < 2 mg/L, and TDS < 10 mg/L, which would essentially meet ISS potable water standards after disinfection. The system has an un-optimized mass and volume of 128.5 kg. Consumables include oxygen (~4 g/crew-day), RO membranes, and a prefilter (1.7 g/crew-day). For a one-year mission with four crew, the total system + consumable mass are ~141 kg, which would produce ~15,150 kg of treated water, resulting in a pay-back period of 13.4 days (3.35 days for a crew of four). Given that the MABR in this study operated for 500 days, while in previous studies, similar systems operated for more than 3 years, the total system costs would be exceedingly low. These results highlight the potential application of hybrid treatment systems for space habitats, which may also have a direct application to terrestrial applications where source-separated systems are employed.

Environmental and Economic Assessment of Membrane Capacitive Deionization (MCDI) and Low-Pressure Reverse Osmosis (LPRO) for Sustainable Irrigation in the Mediterranean Region

Ensuring the sustainability of a product or a system requires a thorough evaluation of its environmental and socioeconomic impacts. In this context, one of the objectives of the EU-PRIMA SmaCuMed project is to evaluate the socioeconomic and environmental impacts of the Smart Cube system. The Smart Cube was developed for the PV-powered desalination of brackish groundwater with membrane capacitive deionization (MCDI) and low-pressure reverse osmosis (LPRO); it additionally uses smart sensors for controlled irrigation in remote agricultural areas in Morocco, as an example for the North African region. Based on the Life Cycle Sustainability Assessment approach, this paper aims to assess the environmental and economic impacts of the Smart Cube, using Life Cycle Costing (LCC) and Life Cycle Assessment (LCA) analyses for environmental evaluation. Various scenarios have been defined for both environmental and economic assessments. Based on 1 m3 of produced desalinated water, the LCC results showed that, when using the desalination technologies directly connected to the grid, the prices are lower than those obtained when it was supplied by the PV system. This is only due to the very low energy prices from the Moroccan grid (EUR 0.10/kWh). The LCC results showed that LPRO is a more cost-effective option for producing desalinated water, with a lower total cost compared to MCDI. However, LCA results indicated that LPRO has a higher environmental impact compared to MCDI. If higher water production capacity is a priority, MCDI connected to PV is the best choice, with lower carbon emission but higher overall water costs.

Life cycle analysis of seawater biodesalination using algae

This study assesses environmental impacts of reverse osmosis and algae-based biodesalination in four scenarios using a life cycle assessment (LCA) approach. These scenarios encompass (1) a multistage conventional pre-treatment desalination system, (2) immobilized algae-based hybrid desalination system, (3) suspended algae pre-treatment hybrid system, and (4) an attached growth algae-based hybrid system with a low-pressure reverse osmosis (LPRO) system. The assessment integrates the ReCiPe and USEtox 2.0 methods, examining diverse phases such as construction, operation, waste treatment, and chemicals. The impact analysis unveils waste treatment as a significant contributor in Scenario 1. In Scenarios 2 and 3, the operational phase, driven by chemical consumption, emerges as a major factor by 60–70 %, causing environmental damage. Scenario 4 showcases superior environmental performance, notably in global warming potential, freshwater eutrophication, marine eutrophication, ozone layer depletion, and fossil resource scarcity. Results highlight that Scenario 2 and Scenario 3, utilizing immobilized and suspended growth biodesalination, do not align with favorable LCA outcomes. Overall, Scenario 4 displays the least environmental impact and a favorable carbon footprint. The study advocates pipeline brine disposal due to its greater convenience and lesser environmental damage. A sensitivity analysis emphasizes the advantages of shorter transportation distances for optimal brine disposal from the desalination plant to the sea.

Implementation of a Sensitive Method to Assess High Virus Retention Performance of Low-Pressure Reverse Osmosis Process.

Human enteric viruses are important etiological agents of waterborne diseases. Environmental waters are usually contaminated with low virus concentration requiring large concentration factors for effective detection by (RT)-qPCR. Low-pressure reverse osmosis is often used to remove water contaminants, but very few studies focused on the effective virus removal of reverse osmosis treatment with feed concentrations as close as possible to environmental concentrations and principally relied on theoretical virus removal. The very low viral concentrations usually reported in the permeates (i.e. at least 5 log of removal rate) mean that very large volumes of water need to be analysed to have sufficient sensitivity and assess the process efficiency. This study evaluates two methods for the concentration of adenoviruses, enteroviruses and MS2 bacteriophages at different viral concentrations in large (< 200 L) and very large (> 200 L) volumes. The first method is composed of two ultrafiltration membranes with low-molecular weight cut-offs while the second method primarily relies on adsorption and elution phases using electropositive-charged filters. The recovery rates were assessed for both methods. For the ultrafiltration-based protocol, recovery rates were similar for each virus studied: 80% on average at high virus concentrations (106-107 viruses L-1) and 50% at low virus concentrations (103-104 viruses L-1). For the electropositive-charged filter-based method, the average recoveries obtained were about 36% for ADV 41, 57% for CV-B5 and 1.6% for MS2. The ultrafiltration-based method was then used to evaluate the performance of a low-pressure reverse osmosis lab-scale pilot plant. The retentions by reverse osmosis were similar for all studied viruses and the validated recovery rates applied to the system confirmed the reliability of the concentration method. This method was effective in concentrating all three viruses over a wide range of viral concentrations. Moreover, the second concentration method using electropositive-charged filters was studied, allowing the filtration of larger volumes of permeate from a semi-industrial low-pressure reverse osmosis pilot plant. This reference method was used because of the inability of the UF method to filter volumes on the order of one cubic metre.

Advanced treatment of pharmaceutical and Tyre wastewater with the help of low-pressure reverse osmosis membrane

Advanced treatment of pharmaceutical and Tyre wastewater with the help of low-pressure reverse osmosis membrane

Comparison of Pilot-Scale Capacitive Deionization (MCDI) and Low-Pressure Reverse Osmosis (LPRO) for PV-Powered Brackish Water Desalination in Morocco for Irrigation of Argan Trees.

The use of saline water resources in agriculture is becoming a common practice in semi-arid and arid regions such as the Mediterranean. In the SmaCuMed project, the desalination of brackish groundwater (TDS = 2.8 g/L) for the irrigation of Argan trees in Essaouira, Morocco, to 2 g/L and 1 g/L (33% and 66% salt removal, respectively) using low-pressure reverse osmosis (LPRO) (p < 6 bar) and membrane capacitive deionization (MCDI) was tested at pilot scale. MCDI showed 40-70% lower specific energy consumption (SEC) and 10-20% higher water recovery; however, the throughput of LPRO (2.9 m3/h) was up to 1.5 times higher than that of MCDI. In addition, both technologies were successfully powered by PV solar energy with total water costs ranging from EUR 0.82 to EUR 1.34 per m3. In addition, the water quality in terms of sodium adsorption ratio was slightly higher with LPRO resulting in higher concentrations of Ca2+ and Mg2+, due to blending with feed water. In order to evaluate both technologies, additional criteria such as investment and specific water costs, operability and brine disposal have to be considered.

Application of Low-Pressure Reverse Osmosis Membranes for Drinking Water Softening

Application of Low-Pressure Reverse Osmosis Membranes for Drinking Water Softening

Research of phosphate removal from water on reverse osmotic filters

Eutrophication of natural water bodies caused by an excess of biogenic substances is one of the global environmental problems of modern times. Usually, phosphorus is a limiting biogenic element, the concentration of which determines the intensity of eutrophication processes in water bodies. Therefore, it is important to develop methods aimed at preventing excessive amounts of phosphates from entering the environment. To remove phosphates from water, typically used biological degradation technologies, which usually proceed very slowly and depend on the conditions under which the process takes place. Also, Biogenic elements can be removed by using ion exchange, reverse osmosis, and chemical methods. However, the disposal of concentrated solutions becomes an issue with these methods. Baromembrane purification methods, particularly reverse osmosis, are becoming increasingly important in the field of water treatment and purification and are essential in creating efficient and low-waste complex technologies for water purification from biogenic compounds. The study investigated the processes of removing orthophosphates from distilled and artesian water using a low-pressure reverse osmosis membrane Filmtec TW30-1812-50. The dependence of membrane productivity and selectivity on the concentration of phosphates and the degree of permeate rejection was determined. Was found that residual concentrations of phosphates in the permeate increase with the increase in the degree of permeate rejection. The lowest residual concentrations of phosphates were observed at the initial concentration of up to 10 mg/dm3. The highest residual phosphate concentrations were observed at initial concentrations above 900 mg/dm3. At the same time, the membrane productivity constantly decreased with increasing feed concentration and degree of permeate recovery due to the increased osmotic pressure on the membrane. The selectivity of the membrane was highest at an initial concentration of up to 10 mg/dm3 and slightly decreased at a rejection rate of 20-50% for initial phosphate concentrations of 100-900 mg/dm3. At the maximum degree of permeate rejection (90%), the selectivity of the membrane reached 97-99 % and decreased with an increase in phosphate concentrations, which is due to a change in the pH of the medium, hydrolysis of phosphates, hydration of ions, and concentration polarization. The membrane selectivity for phosphates in solutions in artesian water was slightly lower (95-99 %), which was due to the competing influence of chlorides, sulfates, and bicarbonates, as well as a decrease in the pH of the solution to 7.52-7.67, which promotes the hydrolysis of o-phosphates.

Enhancing boron rejection in low-pressure reverse osmosis systems using a cellulose fiber–carbon nanotube nanocomposite polyamide membrane: A study on chemical structure and surface morphology

Nanocomposite membranes based on carbon nanotubes (CNTs) or cellulose nanofibers (CNFs) are promising solutions for water filtration technologies such as seawater desalination, brackish water purification, and wastewater treatment. In this study, we investigated the effect of integrating CNTs and CNFs into a polyamide membrane (CNT–CNF–PA) on boron rejection in low−pressure reverse osmosis (RO) systems (0.75 MPa). A NaCl (500 ppm) and boron (5 ppm) based solution at pH = 7 was tested in an RO filtration system. The CNT–CNF–PA membrane exhibited a high boron rejection rate (up to 74%) and high permeation (greater than 1.0 m3/m2∙day). The chemical structure played a significant role in boron rejection performance. We conducted principal component analysis (PCA) to statistically study the changes in bond vibrations obtained by Fourier transform infrared (FTIR) spectroscopy, comparing the oxygenated and hydrogenated changes to sodium chloride rejection, boron rejection, and water permeation of the membranes. Additionally, the surface morphology, i.e., roughness, exhibits a direct positive effect on boron rejection, whereas the pore structure is linked to both sodium chloride and boron rejections. Molecular dynamic simulations revealed that the CNF and CNT structures suppress the hydrogen bonds between the PA matrix and boric acid, negatively affecting its diffusion and rejection. These findings help clarify the boron rejection mechanism, enabling further development of PA membranes.

Evaluation of Forward Osmosis and Low-Pressure Reverse Osmosis with a Tubular Membrane for the Concentration of Municipal Wastewater and the Production of Biogas

Currently, freshwater scarcity is one of the main issues that the world population has to face. To address this issue, new wastewater treatment technologies have been developed such as membrane processes. Among them, due to the energy disadvantages of pressure-driven membrane processes, Forward Osmosis (FO) and Low-Pressure Reverse Osmosis (LPRO) have been introduced as promising alternatives. In this study, the behavior of a 2.3 m2 tubular membrane TFO-D90 when working with municipal wastewater has been studied. Its performances have been evaluated and compared in two operating modes such as FO and LPRO. Parameters such as fouling, flow rates, water flux, draw solution concentration, organic matter concentration, as well as its recovery have been studied. In addition, the biogas production capacity has been evaluated with the concentrated municipal wastewater obtained from each process. The results of this study indicate that the membrane can work in both processes (FO and LPRO) but, from the energy and productivity point of view, FO is considered more appropriate mainly due to its lower fouling level. This research may offer a new point of view on low-energy and energy recovery wastewater treatment and the applicability of FO and LPRO for wastewater concentration.

Removal of Chromium Species from Low-Contaminated Raw Water by Different Drinking Water Treatment Processes

The occurrence of Cr (VI) in drinking water resources in low but toxicologically relevant concentrations requires the development of reliable and industrially applicable separation processes in drinking water treatment. There is little information in the literature on the removal of chromium species at concentrations below 10 µg/L. Therefore, in this study, the removal of chromium in the concentration range ≤10 µg/L was investigated using three separation processes, activated carbon filtration (ACF), reduction/coagulation/filtration (RCF) and low-pressure reverse osmosis (LPRO), in both laboratory- and pilot-scale tests. In ACF treatment, Cr (III) was removed by deep bed filtration over 1.5 m of anthracite at a pH of 7.5 (which was used as a prefilter prior to ACF), while Cr (VI) was removed up to 75% via ACF at a filter bed depth of 2.5 m. Fresh activated carbon (AC) exhibited the highest adsorption capacity for Cr (VI), while reactivated AC had a significantly lower capacity for Cr (VI), which was attributed to calcium and iron deposits. In technical filters, where multiple reactivated activated carbon is used, this led to a low removal rate for Cr (VI). Using the RCF process with Fe (II) dosing in a continuous flow reactor at a specific coagulant dosing ratio, high Cr (VI) removal, down to a concentration of 0.1 µg/L, was achieved within minutes. The subsequent anthracite filtration ensured the complete removal of Fe (III) and Cr (III) precipitates. The RCF process was limited by the oxygen side reaction with Fe (II), which dominated at Cr (VI) concentrations below 1 µg/L. In addition, a four-step LPRO process with concentrate recycling showed effective removal (&gt;99%) of both Cr (III) and Cr (VI) species in raw water as well as a negligible effect of pH in the testing pH range of 5.6 to 8.3 on the Cr (VI) removal. Nevertheless, the water hardness and pH of the LPRO permeate must be increased to make it available as drinking water. The three separation processes were found to be able to meet the expected more stringent future regulations for Cr (VI) level in drinking water. The most suitable technology, however, can be selected with respect to the raw water quality/characteristics, site-specific conditions and the already existing equipment.

ВИЗНАЧЕННЯ ЕФЕКТИВНОСТІ ВИЛУЧЕННЯ СУЛЬФАТІВ НА ЗВОРОТНООСМОТИЧНІЙ МЕМБРАНІ НИЗЬКОГО ТИСКУ

The dependence of the efficiency of the low-pressure reverse osmosis membrane Filmtec TW30-1812-50 on the initial concentrations of sodium sulfate in the range of 10-650 mg/dm3 at permeate recovery rates of 1-90 % using a pressure of 4 atm was determined. The effect of increasing the permeate recovery rate on selectivity, membrane performance, and the in-crease in the sulfate content of concentrates was determined. It is shown that the concentration of sulfates in permeate depends on their initial concentration in solutions and increases both with an increase in the initial concentration and with an increase in the degree of permeate extraction. The latter factor is quite significant at initial sulfate concentrations of 650 mg/dm3. The membrane performance increases with decreasing salt content in water and decreases with increasing permeate removal rate, which leads to an increase in salt concentration in the pre-membrane space. The selectivity of the membrane for sulfates is 94.9-99.3 % and increases with increasing concentration of sodium sulfate solutions in solutions, despite a certain increase in salt concentrations in permeates. It is shown that as the degree of permeate selection increases, the selectivity for solutions with low initial sulfate concentrations increases. A FFP-based process modeling was performed to determine the sulfate con-centration in the permeate and concentrate at any initial sulfate concentration in a certain range. It was found that the con-centrate solutions are stable in the entire range of concentrations used with an increase in the degree of permeate recovery from 10 to 90 %. Based on the research results, a method for determining the capacity of the plant and the osmotic and oper-ating pressures based on the salt concentration and the set pressure in the system was proposed. From the data obtained, it can be concluded that the permissible level of mineralization at which the use of low-pressure reverse osmosis membranes is ad-visable.

Modular desalination concept with low-pressure reverse osmosis and capacitive deionization: Performance study of a pilot plant in Vietnam in comparison to seawater reverse osmosis

Membrane capacitive deionization (MCDI) has shown many advances, however, its performance in combination with other treatment technologies has not been widely reported. In this study, a pilot-scale low-pressure reverse osmosis (LPRO) (FilmTec™ XLE-2540) with MCDI (CapDI© C17, Voltea) was developed and tested as a promising modular desalination system. The systems were evaluated individually at different salinities and tested together as a modular system. The study focused in the comparison to conventional seawater reverse osmosis (SWRO) (FilmTec™ SW30-2540) at pilot-scale and in theory using the software Water Application Value Engine (WAVE, DuPont™), including a cost evaluation of the systems. Pilot tests were carried out in Can Gio, a riverine estuary region in South Vietnam, which is affected by progressive salinization (TDS ≈ 1–25 g/L). Drinking water quality (TDS < 600 mg/L) was achieved with a specific energy consumption (SEC) of 5.2 kWh/m³. Additionally, fouling mitigation was investigated for the ultrafiltration (UF) pre-treatment by periodic hydraulic and chemical enhanced backwashing. While the SWRO had a slightly lower SEC of 5.0 kWh/m³, WAVE calculations showed that lowering the SEC to 3.6 kWh/m³ is possible by improving the LPRO pump design and an optimization of the MCDI operation.

The problem of pollution of drinking water with nitrate ions and modern methods of its solution

The article discusses various regulatory documents that regulate the content of nitrate ions in drinking water, as well as the impact of nitrates on human health and safety. The results of studies on nitrate ion contamination of sources of drinking water supply in 5 regions of Ukraine are presented. Physico-chemical analysis was carried out for water sources from wells in rural areas, city limits and in the territories adjacent to cities. The relevance of the problem of water pollution with nitrate ions, which requires the search, implementation and improvement of water purification methods from nitrates, has been proven. A comparative analysis of the advantages, disadvantages and features of the use of various methods of removing nitrate ions from drinking water, including water from non-centralized sources of water supply, was carried out. Biological, ion-exchange, adsorption, electrochemical methods, as well as baromembrane methods, in particular the reverse osmosis method, are used to purify water from nitrate ions. The regularities of the reverse osmosis process during the removal of nitrate ions from model solutions and water from wells were studied. Reverse osmosis membranes manufactured in the USA by Filmtec type TW30-1812-50 were used for experimental studies. Model solutions of Mg(NO3)2, Zn(NO3)2 and, directly, water from non-centralized sources of water supply were used as the tested water. Membrane selectivity and permeate selection coefficient were determined according to the known method. Parametric curves of the dependence of the selectivity of the membrane in relation to NO3- on the increase of the working pressure from 0.5 MPa to 1.9 MPa for model solutions of different concentrations were constructed. The dependences of the change in the concentration of nitrate ions in well water and the selectivity (φ, %) of the membrane in relation to NO3- on the working pressure were obtained. On the basis of the research results, a conclusion was made about the high efficiency of water purification from nitrates by low-pressure reverse osmosis (in the range from 0.5 MPa to 1.9 MPa) and the parameters of the researched process were determined, which would allow reaching the MPC standards for nitrates in drinking water.

Feasibility of Poly (Vinyl Alcohol)/Poly (Diallyldimethylammonium Chloride) Polymeric Network Hydrogel as Draw Solute for Forward Osmosis Process.

Forward osmosis (FO) has been identified as an emerging technology for the concentration and crystallization of aqueous solutions at low temperatures. However, the application of the FO process has been limited due to the unavailability of a suitable draw solute. An ideal draw solute should be able to generate high osmotic pressure and must be easily regenerated with less reverse solute flux (RSF). Recently, hydrogels have attracted attention as a draw solution due to their high capacity to absorb water and low RSF. This study explores a poly (vinyl alcohol)/ poly (diallyldimethylammonium chloride) (PVA-polyDADMAC) polymeric network hydrogel as a draw solute in forward osmosis. A low-pressure reverse osmosis (RO) membrane was used in the FO process to study the performance of the hydrogel prepared in this study as a draw solution. The robust and straightforward gel synthesis method provides an extensive-scale application. The results indicate that incorporating cationic polyelectrolyte poly (diallyldimethylammonium chloride) into the polymeric network increases swelling capacity and osmotic pressure, thereby resulting in an average water flux of the PVA-polyDADMAC hydrogel (0.97 L m-2 h-1) that was 7.47 times higher than the PVA hydrogel during a 6 h FO process against a 5000 mg L-1 NaCl solution (as a feed solution). The effect of polymer and cross-linker composition on swelling capacity was studied to optimize the synthesized hydrogel composition. At 50 °C, the hydrogel releases nearly &gt;70% of the water absorbed during the FO process at room temperatures, and water flux can be recovered by up to 86.6% of the initial flux after 12 hydrogel (draw solute) regenerations. Furthermore, this study suggests that incorporating cationic polyelectrolytes into the polymeric network enhances FO performances and lowers the actual energy requirements for (draw solute) regeneration. This study represents a significant step toward the commercial implementation of a hydrogel-driven FO system for the concentration of liquid-food extract.

Rural Application of a Low-Pressure Reverse Osmosis Desalination System Powered by Solar–Photovoltaic Energy for Mexican Arid Zones

A reverse osmosis system driven by photovoltaic energy is an eco-friendly and sustainable way to produce freshwater in rural areas without connection to a power grid and with available brackish water sources. This paper describes a project where a photovoltaic-driven low-pressure reverse osmosis system (LPRO-PV) was designed, tested under laboratory conditions, and installed in Samalayuca, Chihuahua, Mexico, to evaluate the technical feasibility and social impact of this technology. The LPRO-PV system was tested with synthetic water with a salinity of 2921 ± 62.3 mg/L; the maximum freshwater volume produced was 1.8 ± 0.06 m3/day with a salinity value of 91 ± 1.9 mg/L. The LPRO-PV system satisfied the basic freshwater requirements for a local family of three members for one year, including the mobility-restriction period due to the COVID-19 pandemic. The social evaluation analysis reflects the importance of considering the technical aspects derived from the experimental tests, as well as the users’ perception of the performance and operation of the system. As a result of the implementation of this technology and the benefits described by the users, they committed to the maintenance activities required for the LPRO-PV system’s operation. This technology has great potential to produce fresh water in arid and isolated regions with high-salinity groundwater sources, thus fulfilling the human right to safe and clean drinking water.

Tradeoff between micropollutant abatement and bromate formation during ozonation of concentrates from nanofiltration and reverse osmosis processes

Water treatment with nanofiltration (NF) or reverse osmosis (RO) membranes results in a purified permeate and a retentate, where solutes are concentrated and have to be properly managed and discharged. To date, little is known on how the selection of a semi-permeable dense membrane impacts the dissolved organic matter in the concentrate and what the consequences are for micropollutant (MP) abatement and bromate formation during concentrate treatment with ozone. Laboratory ozonation experiments were performed with standardized concentrates produced by three membranes (two NFs and one low-pressure reverse osmosis (LPRO) membrane) from three water sources (two river waters and one lake water). The concentrates were standardized by adjustment of pH and concentrations of dissolved organic carbon, total inorganic carbon, selected micropollutants (MP) with a low to high ozone reactivity and bromide to exclude factors which are known to impact ozonation. NF membranes had a lower retention of bromide and MPs than the LPRO membrane, and if the permeate quality of the NF membrane meets the requirements, the selection of this membrane type is beneficial due to the lower bromate formation risks upon concentrate ozonation. The bromate formation was typically higher in standardized concentrates of LPRO than of NF membranes, but the tradeoff between MP abatement and bromate formation upon ozonation of the standardized concentrates was not affected by the membrane type. Furthermore, there was no difference for the different source waters. Overall, ozonation of concentrates is only feasible for abatement of MPs with a high to moderate ozone reactivity with limited bromate formation. Differences in the DOM composition between NF and LPRO membrane concentrates are less relevant than retention of MPs and bromide by the membrane and the required ozone dose to meet a treatment target.

Low-pressure reverse osmosis membrane made of cellulose nanofiber and carbon nanotube polyamide nano-nanocomposite for high purity water production

Cellulose nanofiber (CNF) and multiwall carbon nanotube (CNT) nanocomposite polyamide membranes were synthesized and used in a low-pressure reverse osmosis (RO) system. Incorporating CNT and CNF into the polyamide structure (PA-CNT/CNF) allows the homogenous dispersion within the polymeric matrix, increasing its hydrophobic character and surface oxygen functionalities while reducing its surface roughness when compared to plain polyamide (PA), PA-CNT, and PA-CNF membranes. The resultant nanocomposite was tested at 0.75 MPa and sodium chloride salt concentration of 500 ppm resulting in a rejection of 99.47 % and water permeability of 1.65 m3/m2day. The rejection and permeation performance is highly competitive compared with commercial RO membranes. A 2in spiral module built with the PA-CNT/CNF membrane and tested for SiO2, NaCl, and CaCl2 rejection showed a reduction in its permeability of 24.9 % after 100 h of operations, while the commercials showed a decrease of 49.42 %. The present RO membrane module achieved a calcium rejection of 97.5 % and a boron rejection of 50.4 %. The 2in PA-CNT/CNF spiral module was tested in a two-step RO filtration system for high pure water (HPW) production and compared with a TW30 module with NSF certification. The PA-CNT/CNF module revealed a permeability reduction of 9.07% after 30 h operation, while TW30 had a reduction of 20.3%, which is about twice the durability. Molecular dynamics simulation showed that the CNF increased water hydration and boron diffusion on the membrane while CNT increased charge transfer to the PA structure. This polymeric nanocomposite has potential use in producing high purity water for brackish water or wastewater reuse for applications in the emerging semiconductor or pharmacology industry.

Assessing the potential of highly permeable reverse osmosis membranes for desalination: Specific energy and footprint analysis

The ultra-permeable membranes (UPMs) are expected to reduce the specific energy consumption (SEC) of desalination, but the potential of UPMs in hollow fiber configuration has not been well quantified. Herein, we analyse the SEC and footprints of UPM modules in three feed salinities: seawater reverse osmosis (SWRO), brackish water RO (BWRO) and low-pressure RO (LPRO). Through the modelling the fluid dynamics and mass transport of RO systems, we find that a tripling in spiral-wound SWRO membrane permeability (based on the current value of 1 L m−2 h−1 bar−1; LMH/bar) could result in 16% decrease in SEC. Contrastingly, the quadrupling of hollow fiber SWRO membrane permeability (based on the current value of 0.25 LMH/bar) could reduce the SEC by 23%. According to our analysis, hollow fiber and spiral-wound SWRO membranes with permeabilities up to 1 LMH/bar and 3 LMH/bar, respectively, can reduce the SEC of seawater desalination. On the other hand, membranes with permeabilities up to 9 LMH/bar and 12 LMH/bar can lead to SEC savings in BWRO and LPRO desalination, respectively. This study provides a general guidance to RO membrane researchers on the permeability upper-limit of which UPMs could bring about SEC and footprint savings at a system level.