Reverse Osmosis System Research Articles

Piloting batch reverse osmosis with a flexible bladder for water recovery from scaling-prone brine

A pilot-scale batch reverse osmosis (RO) system with a flexible bladder was designed to recover additional water from RO concentrate. The sulfate-rich, ~6400-ppm concentrate was sourced from the Yuma Desalting Plant (Arizona, USA), which desalinates agricultural drainage water. The pilot produced 4.4 m3/day of permeate with 150 ppm total dissolved solids from the facility’s concentrate stream with a recovery ratio of 82.6%. Despite producing supersaturated brine, there was no performance deterioration due to scaling. Using a bladder for retentate pressurization limited average power to 633 W and the specific energy consumption to 3.3 kWh/m3. The pilot’s energy data informed a model of large-scale batch RO, which has the potential to desalinate the same water for less than 1 kWh/m3. Additionally, a model was developed to predict scaling likelihood in batch RO. This investigation demonstrates that batch RO is a viable technology for low-energy brine concentration beyond saturation limits.

Closing the loop: model-predictive control for a closed-circuit reverse osmosis system

ABSTRACT This article presents a model-predictive controller (MPC) for the maximization of the energy efficiency of a closed-circuit desalination reverse osmosis (CCRO) system. CCRO is a process for producing drinking water that is based on a cyclic operation with the following two phases: (a) filtration and (b) drain. In this article, we test model predictive control for optimal control of this process. The most important features of our approach are as follows: (a) the selection of a model structure that enables reliable forecasts of the filtration phase (up to 3 h), (b) an on-line model calibration strategy that ensures model forecast reliability, and (c) the satisfaction of equipment safety and operational constraints on the selected setpoints. We challenge this through deliberate introduction of changes in the unmeasured feed concentration and the applied constraints. Our results indicate that frequent model parameter updates are critical to maintain model reliability for MPC purposes. In addition, we illustrate that parameter identifiability is not guaranteed and that deliberate variation in flow rates is necessary even though the process never operates in steady state. Finally, MPC can compute flow rate setpoints that maximize the energy efficiency of the CCRO process while satisfying the applicable equipment and safety constraints.

Can UVC-LEDs mitigate biofouling in community-scale photovoltaic-powered reverse osmosis systems?

Can UVC-LEDs mitigate biofouling in community-scale photovoltaic-powered reverse osmosis systems?

Hemodialysis and Water Management in a Dialysis Unit in Morocco, an Approach to Dealing With Water Scarcity.

Chronic kidney disease is a global public health issue, affecting approximately 10% of the world's population, and more than 3 million people living with kidney failure who are estimated to be on maintenance dialysis programs, with the majority receiving hemodialysis (HD). This treatment is particularly water-intensive, posing a considerable challenge in regions experiencing water scarcity, such as Morocco. Our HD center in Oujda, Eastern Morocco, has implemented several key strategies to address water scarcity and ensure uninterrupted HD procedures during periods of hydric stress. These strategies include expanding water storage capacities to safeguard against shortages, upgrading infrastructure to enhance water efficiency, and employing innovative technology for real-time monitoring and management of water resources. Additionally, we collaborate closely with local water authorities to secure reliable water supplies and explore possibilities for water regeneration and recycling. The rising demand for clean water, coupled with its increasing scarcity, presents a significant challenge for healthcare systems, particularly in the context of HD. Therefore, innovative approaches are essential to mitigate this issue. The concept of green dialysis, which focuses on reducing water usage and minimizing environmental impact, is emerging as a promising solution with measurable benefits. Implementing water-efficient reverse osmosis systems has resulted in significant reductions in water waste, while real-time monitoring and early warning systems have enhanced water security and operational efficiency. Additionally, initiatives exploring the reuse of reject water hold potential for further conservation. These tangible outcomes demonstrate how green dialysis practices can contribute to sustainable HD treatment, ensuring uninterrupted patient care, reduced resource consumption, and improved environmental stewardship in water-scarce regions.

Water–Energy Nexus: Membrane Engineering Towards a Sustainable Development

Sustainable development is linked to the achievement of several different objectives, as outlined by the 17 Sustainable Development Goals (SDGs) defined by the United Nations. Among them are the production of clean water and the combat of climate change, which is strictly linked to the use of fossil fuels as a primary energy source and their related CO2 emissions. Water and energy are strongly interconnected. For instance, when processing water, energy is needed to pump, treat, heat/cool, and deliver water. Membrane operations for water treatment/desalination contribute to the recovery of purified/fresh water and reducing the environmental impact of waste streams. However, to be sustainable, water recovery must not be energy intensive. In this respect, this contribution aims to illustrate the state of the art and perspectives in desalination by reverse osmosis (RO), discussing the various approaches looking to improve the energy efficiency of this process. In particular, the coupling of RO with other membrane operations, like pressure-retarded osmosis (PRO), reverse electrodialysis (RED), and forward osmosis (FO), as well as the osmotic-assisted reverse osmosis (OARO) system, are reported. Moreover, the possibility of coupling a membrane distillation (MD) unit to an RO one to increase the overall freshwater recovery factor and reduce the brine volumes that are disposed is also discussed. Specific emphasis is placed on the strategies being applied to reduce the MD thermal energy demand, so as to couple the production of the blue gold with the fight against climate change.

Advancing freshwater conservation: techno-economic study of conventional and closed-circuit reverse osmosis systems in full-scale units with challenging feed water conditions.

This techno-economic study evaluated two approaches for conserving freshwater in full-scale brackish RO units, i.e., conventional secondary RO and closed-circuit RO (CCRO) systems. Three industrial cases with silica-rich, sulfate-rich, and high-salinity waters were analyzed through numerical modeling. Results demonstrated that both secondary RO and CCRO effectively conserved freshwater, with CCRO achieving 5-8% higher recovery rates and being less prone to scaling. However, CCRO recovery was limited by silica and sulfate salts supersaturation and constrained by the maximum operating pressure (41.3bar) for high-salinity water. CCRO systems required fewer membrane elements, eliminated acid use, and consumed less energy but demanded more pressure vessels, higher antiscalant use, and produced slightly lower permeate quality. Statistical analysis revealed critical operational thresholds for both systems: 83% recovery for multi-stage RO and 89% for CCRO, beyond which performance declines significantly, especially at higher feed salinities. Economically, multi-stage RO consistently exhibited lower capital and total production costs across all case studies, while CCRO's advantages in recovery and energy efficiency were offset by higher capital and chemical expenses. Nevertheless, CCRO remains a potentially competitive option in moderate-salinity conditions if antiscalant consumption is optimized.

Optimization of carbon membrane performance in reverse osmosis systems for reducing salinity, nitrates, phosphates, and ammonia in aquaculture wastewater.

Optimization of carbon membrane performance in reverse osmosis systems for reducing salinity, nitrates, phosphates, and ammonia in aquaculture wastewater.

Multiple benefits of MBR and absolute-rated cartridge filters for RO pretreatment: Results from a full-scale facility

ABSTRACT There is interest in processes that can both contribute to pathogen removal and provide effective pretreatment for reverse osmosis (RO) in potable reuse systems. The most familiar reuse treatment train employs micro-/ultra-filtration (MF/UF) along with cartridge filters (CFs) upstream of RO. However, there are some applications for which other pre-RO processes, such as membrane bioreactors (MBRs), are desirable, and more research is needed on MBR for RO pretreatment. In addition, although CFs are widely used, the literature does not elucidate their capability for pathogen removal and fouling control. In this study, MBR along with absolute-rated 1 µm CFs were demonstrated for RO pretreatment at full scale. This plant included two identical trains, which provide additional robustness to the results. Online MBR and CF data confirmed performance within critical control point limits, and breach testing of the CFs demonstrated a consistent response pattern in differential pressure (dP) data and with novel derived parameters. These observed breach responses and novel parameters are a useful contribution to the online monitoring of CFs as a pathogen barrier. The combined pretreatment processes also achieved remarkably low fouling rates at the downstream RO system, lower than other recently-reported MBR-RO facilities and consistent with 5 -7 month clean-in-place intervals. The observation of significant increase in dP over 2 weeks showed that the CFs were capturing colloidal particles even from low-turbidity influent, and this resulted in lower-than-expected fouling rates at the downstream RO. This study therefore provides a fundamental insight into the into RO fouling propensity of MBR filtrate: namely, colloidal particles in the size range of 1 µm and above are an important contributor to fouling propensity when they are not removed by pre-RO treatment. Overall, these results demonstrated the multiple benefits of a novel MBR-CF pre-RO treatment train.

Pressure-Driven Membrane Processes for Removing Microplastics.

The intense consumption of polymeric materials combined with poor waste management results in the dissemination of their fragments in the environment as micro- and nanoplastics. They are easily dispersed in stormwater, wastewater, and landfill leachate and carried towards rivers, lakes, and oceans, causing their contamination. In aqueous matrices, the use of membrane separation processes has stood out for the efficiency of removing these particulate contaminants, achieving removals of up to 100%. For this review article, we researched the removal of microplastics and nanoplastics by membrane processes whose driving force is the pressure gradient. The analysis focuses on the challenges found in the operation of microfiltration, ultrafiltration, nanofiltration, and reverse-osmosis systems, as well as on the innovations applied to the membranes, with comparisons of treatment systems and the peculiarities of each system and each aqueous matrix. We also point out weaknesses and opportunities for future studies so that these techniques, known to be capable of removing many other contaminants of emerging concern, can subsequently be widely applied in the removal of micro- and nanoplastics.

Unravelling pH-dependent formation and deposition mechanisms of Si–Al complex scale in reverse osmosis systems

Unravelling pH-dependent formation and deposition mechanisms of Si–Al complex scale in reverse osmosis systems

Critical challenges in high-salinity seawater reverse osmosis systems: Technical, energy, and environmental reviews

Critical challenges in high-salinity seawater reverse osmosis systems: Technical, energy, and environmental reviews

Characterization and mitigation strategies for inorganic scaling in reverse osmosis system treating brackish groundwater

Characterization and mitigation strategies for inorganic scaling in reverse osmosis system treating brackish groundwater

Harnessing Electrochemistry Synergy in Reverse Osmosis: Modulating Ammonium Localized Oxidation and Restricted Transport.

The unsatisfactory selectivity of reverse osmosis (RO) membranes toward ammonium poses a critical challenge in water safety when reclaiming water from domestic wastewater. Herein, we developed a novel integrated electrochemical-assisted RO (ECRO) system using the electrically treated feed spacer and permeate carrier as electrodes. This system enhanced ammonium removal efficiency significantly while maintaining low energy consumption, increasing from 94.36% at 0 V to 99.91% at 4 V. The improvement was primarily attributed to localized oxidation and restricted transport of ammonium ions. Specifically, the permeate carrier anode facilitated the indirect oxidation of ammonium through active chlorine via the breakpoint chlorination pathway, notably localized on the permeate side to prevent damage to the separation layer of the RO membrane and simultaneously avoid additional chemical additives. Furthermore, the restricted ammonium ion transport was responsible for its improved enthalpic barrier, as evidenced by both experimental investigation and Monte Carlo simulation. This rise in enthalpic barrier was primarily driven by the reverse electric field force across the RO membrane, coupled with the constrained ion migration near the membrane surface and ion diffusion within the membrane. This study offers new insights and a theoretical foundation for the optimization of electrochemistry synergy membrane systems, highlighting the potential for enhancing ammonium removal in wastewater reclamation in a green and low-energy manner.

Role of microbial electrolysis desalination cell in sustainable water and energy management: Performance assessment of platinum and nickel foam cathodes and simulating integration with reverse osmosis systems

Role of microbial electrolysis desalination cell in sustainable water and energy management: Performance assessment of platinum and nickel foam cathodes and simulating integration with reverse osmosis systems

Hygienic assessment of the ionic composition of drinking water of the centralized water supply of the Vladimir region

Introduction. The paper presents the results of a study on the hygienic assessment of the cationic-anionic composition of drinking water of centralized water supply in the administrative centers of the Vladimir region. Materials and methods. The object of the study was the water of the sources of the central water supply of the administrative centers of the Vladimir region. The content of water-soluble forms of anions and cations was determined by capillary electrophoresis. There were compared concentration values ​​with maximum permissible concentrations (MPC) and ranges of permissible hygienic standards (RHS). Results. In some administrative centers, there has been established concentrations of nitrate ions, phosphate ions, magnesium ions, hardness exceeding the maximum permissible concentrations in drinking water of centralized water supply. Non‒compliance with permissible hygienic standards for chlorides in 16 localities was revealed as follows: for sulfates – in 11; for potassium ions – in 8; for sodium ions – in 9; for magnesium ions – in 3. Non-compliance with minimum RHS for calcium ions was found in the one city. The excess of RHS was noted in seven administrative centers for calcium ions. The drinking water of centralized sources in the city of Petushki is characterized by the highest compliance with hygienic standards (MPC and RHS) according to a set of indices; the smallest is the city of Murom. Limitations are related to the one-time selection and small number of samples, which fails to allow for a broader interpreting of the obtained data. Conclusion. The use of drinking water, the quality of which does not meet sanitary and hygienic requirements, may cause an increase in both the level of general morbidity of the population and in certain nosological forms. In order to reduce the potential adverse impact of drinking water with a high content of nitrate ions, phosphate ions, hardness salts on health, the population is recommended to use household water purification filters, the principle of operation of which is based on methods of adsorption and ion exchange, as well as to use household reverse osmosis systems with a mineralizer, allowing to purify drinking water by the membrane method get rid of excess anions and hardness salts and saturate it with trace elements necessary for the human body.

Highly Permselective Contorted Polyamide Desalination Membranes with Enhanced Free Volume Fabricated by mLbL Assembly.

The permeability-selectivity trade-off in polymeric desalination membranes limits the efficiency and increases the costs of reverse osmosis and nanofiltration systems. Ultrathin contorted polyamide films with enhanced free volume demonstrate an impressive 8-fold increase in water permeance while maintaining equivalent salt rejection compared to conventional polyamide membranes made with m-phenylenediamine and trimesoyl chloride monomers. The solution-based molecular layer-by-layer (mLbL) deposition technique employed for membrane fabrication sequentially reacts a shape-persistent contorted diamine monomer with a trimesoyl chloride monomer, forming highly cross-linked, dense polyamide networks while avoiding the kinetic and mass transfer limitations of traditional interfacial polymerization. The mLbL process allows precise nanoscale control over polyamide selective layer thickness, network structure, and surface roughness. The resulting controlled film thicknesses enable direct measurements of water and NaCl permeabilities. The permselectivities of contorted polyamide membranes surpass those of commercial desalination membranes and approach the reported polyamide upper bound. Solution-diffusion transport modeling indicates that this high permselectivity may be attributed to enhanced water transport pathways in the contorted polyamides that increase water diffusivity-permeability while maintaining high solute rejection through solubility-selectivity.

A water footprint inventory for a textile organization: A Case Study in Denim Washing Industry based on the Integrated Reverse Osmosis System.

The consideration of scarcity and overexploitation of freshwater at the organizational level increased interest in the water footprint. The water footprint measures freshwater use for activities, taking into account water consumption and pollution contamination by classifying consumed water into groundwater and surface water (blue water), rainwater (green water), and polluted water (grey water). This study aims to identify a comprehensive water footprint inventory analysis for a denim washing organization and assess the grey water footprint (GWF) based on the effluent concentration of pollution indicators (chemical oxygen demand (COD), suspended solids (SS), ammonium nitrogen (NH4-N), and phenol) measured monthly in 2021. The company used well water for its operations, which constituted 61.79% of the total water use of the facility, water used by the organization by reverse osmosis accounted for 37.60% of total water consumption, and rainwater made up 0.61% of the volume of water used overall. The grey water footprints of COD, SS, NH4-N, and phenol were calculated as 59981.53 m3, 31747.21 m3, 10514 m3, and 48190 m3, respectively. The results illustrated that the COD, which accounted for 40% of the pollutants, had the highest grey water footprint in the organization, corresponding to the amount of freshwater required to assimilate pollutants to meet water quality standards. In addition, the effect of the reverse osmosis system on the blue water footprint of this organization was analyzed by considering two different scenarios. Reverse osmosis considerably impacted the blue water footprint, accounting for over 37% of this organization's water use. It suggests that a wastewater treatment plant using reverse osmosis is an ideal option for recovering water. The main contributions of this study are comprehensively assessing the water footprint components of the denim washing company and understanding sector-specific water footprint at the organization level.

Isolation and Identification of Cryptosporidium sp. by Reverse Osmosis System of Tap water in Baghdad

A total of 60 samples of drinking water filtrated by Reverser 0smosis Filtration System from April to October 2012, from different houses in Baghdad – Al Resafa, so as to identify the eggs and cysts of protozoa. Two methods applied direct smear and staining technique with zeal nelson stain, which appeared Tape warm eggs, Ascaris lumbrecoides eggs and oocyst of Cryptospordium sp. This study revealed that total contamination rate with intestinal parasites in tap water were 96.6% this high rate, refers to filtrate tap water by reverse osmosis system was useful to prevent or reduce the contamination of drinking water, in order to reduce risks to public health; So recommended to apply this method at water purification stations. Distribution of Cryptosporidium sp. as study months of year appeared that Spring (April& May ) were recorded the highest rate of contamination in filtrate tap water samples, that due to potential temperatures degrees for this protozoa as(20-30cº).When the drinking water was better as environmental maintained decreased the infection with these parasites.

Investigation of carbon dioxide for scale control in reverse osmosis systems.

Investigation of carbon dioxide for scale control in reverse osmosis systems.

POLYAMIDE REVERSE OSMOSIS MEMBRANES MODIFIED WITH GRAPHENE OXIDE FOR ENHANCED CHLORINE ATTACK AND FOULING RESISTANCE

Reverse osmosis (RO) systems are an essential tool for water desalination, but their effectiveness can be hampered by membrane fouling and susceptibility to chemical degradation from free chlorine. Polyamide (PA)...