Reverse Osmosis Membrane Process Research Articles

Utilizing Hybrid RO-OARO Systems as New Methods for Desalination Process

The scarcity of fresh water and its essential role in sustaining life on Earth have motivated researchers to seek new, low-cost, scalable technologies for water desalination. Therefore, the osmotically assisted reverse osmosis (OARO) membrane process presents an innovative approach to achieve moderate water recoveries from high salinity water without undergoing a phase change. This work aims to investigate the performance of hybrid RO-OARO systems with various designs and operational parameters on recovery and R%. The hybrid systems were evaluated for 60 minutes at feed concentrations of 3.98-5.54 g/l, applied pressures ranging from 3 to 7 bars, and different membrane types. The results showed that the flux of the hybrid system increased by increasing the pressure and decreased by increasing the feed concentration. The highest recovery value was obtained for the RO-OARO system at an RO pressure of 7 bar and an OARO unit at 3 bar for a 3.98 g/l feed concentration. In contrast, when the reverse osmosis pressure was fixed at 5 bar, and the pressure of the OARO unit increased by 2 bar, the recovery value exceeded by about 6%. Furthermore, the FilmTech membrane showed the highest recovery at 31.7%, while the highest R% was 94.55% for the AquaTec membrane. The RO-OARO-OARO system contributed to increasing both the recovery and rejection values by 11.4 and 2.1%, respectively, compared with the RO-OARO system. The experiments in this study revealed a slight increase in the feed concentration of the reverse osmosis unit, indicating the efficiency of the hybrid systems compared to traditional RO systems.

Removal of heavy metals from wastewater using reverse osmosis

This study presents an overview of and innovations in reverse osmosis (RO) membrane processes for rejecting charged metal ions in wastewater in relation to the main problems associated with purification methods. It also explains the emergence of nanomaterials and the different methods applied for RO membrane modification to improve performance. Membrane regeneration and retentate management are also considered. The study concludes with an economic feasibility study for the industrial scale-up of the methodology.

Scaling and cleaning of silica scales on reverse osmosis membrane: Effective removal and degradation mechanisms utilizing gallic acid

Silica scaling on membranes represents one of the most important issues in industrial water systems because of its complex composition and difficulty in removal. However, there is a lack of understanding of the mechanisms for cleaning silica scales from reverse osmosis (RO) membranes. To address this research gap, this study investigated the scaling and cleaning behavior of silica on RO membrane processes, with a specific focus on the silica scale cleaning mechanism using gallic acid (GA). The membrane flux continuously decreased with operation time, even at the lowest initial silicic acid concentration, owing to silica scale blockage. The GA solution exhibited a strong efficacy in cleaning silica-scaling RO membranes. The membrane flux returned to 89.7% of the initial value by removing 81.87% of the silica scale within the first 30 min of the study period. The cleaning mechanism of GA involved its adsorption onto the surface of silica scale particles to form a surface complex and subsequently transition into a water-soluble 1:3 complex within the solution. This complex interaction facilitated the gradual decomposition of the silica scales that adhered to the membrane surface. This study has valuable implications for the development of efficient and effective silica scale cleaning solutions, providing insights into the complex interplay between GA and silica scaling mechanisms.

Electron Beam Radiation Coupled to the Reverse Osmosis Membrane Process for Advanced Treatment of Coking Wastewater

Electron Beam Radiation Coupled to the Reverse Osmosis Membrane Process for Advanced Treatment of Coking Wastewater

Advancements in Water Desalination Through Artificial Intelligence: a Comprehensive Review of AI-Based Methods for Reverse Osmosis Membrane Processes

Advancements in Water Desalination Through Artificial Intelligence: a Comprehensive Review of AI-Based Methods for Reverse Osmosis Membrane Processes

Efficacies and mechanisms of different cleaning strategies for NF and RO membranes in a full-scale zero liquid discharge system

Membrane fouling conditions can be distinct for multi-step nanofiltration (NF) and reverse osmosis (RO) membrane processes in zero liquid discharge (ZLD) system. Customizing cleaning procedures according to fouling characteristics is imperative to improve the overall cleaning efficiency of the system. Herein, we performed four different “alkaline + acid” cleaning procedures, including alkaline solution (NaOH), acid solution (citric acid), metal chelating agents (Na2EDTA), and surfactants (SDS), on five fouled NF and RO membranes from a full-scale ZLD system for cold-rolling wastewater brine treatment. The“alkaline + acid” cleaning procedures were effective for organic and inorganic combined fouling removal in two-stage NF process, but failed to remove SiAl complex scaling completely for the 2nd RO process. Due to the slight membrane fouling, both performance and surface properties of 1st and 3rd pass RO membranes did not change significantly after the cleaning. The high pH-induced solubilization were the major mechanism for the removal of the SiAl complex. Na2EDTA/SDS addition caused the decrease of foulant-foulant and foulant-membrane interactions. Customizing membrane cleaning procedures based on membrane fouling characteristics can facilitate the stable operation of hybrid membrane system for the practical industrial wastewater ZLD treatment.

Investigations on membrane performance for coconut water concentration under pressure and by osmotically driven process

AbstractBACKGROUNDCoconut water has grown in popularity among people as a ready‐to‐drink healthy beverage. Nevertheless, its future export expansion is restricted by high operating costs as large volumes of coconut water have to be handled during exporting and for its storage. Besides, large coconut water volumes also consume high energy during the pasteurization/sterilization process. Thus, in this work, we evaluated the potential of employing polymeric membranes for the concentration of coconut water at room temperature via either a pressure‐driven or osmotically driven process.RESULTSOur results indicated that the membrane that was tested under reverse osmosis (RO) mode at 25 bar could significantly concentrate coconut water by reducing its original volume by up to half, with negligible loss of ions/minerals. Upon completion of the RO process, Brix and conductivity of the coconut water were increased by 90% and 61.4%, respectively. As a comparison, the membrane tested under pressure‐retarded osmosis (PRO) mode was only able to reduce the volume of coconut water by ~12%. Although coconut water concentration via PRO operation does not require an external driving force, this process suffers from several significant drawbacks, including reverse draw solute flux and the requirement for draw solution generation.CONCLUSIONBased on the results obtained, it can be concluded that the RO membrane process is still the most reliable and practical method of concentrating fruit juice, and its performance could be further enhanced using a high‐flux polymeric membrane or through process optimization. © 2023 Society of Chemical Industry (SCI).

The Effect of Organic Matter on Heavy Metals Removal from Simulated Wastewater using a Reverse Osmosis Membrane Process

AbstractThe reverse osmosis (RO) technique is an effective method for producing potable water. It is commonly employed in water treatment facilities because of its lower cost and simplicity compared to other methods. The main challenge to the RO process is fouling, which leads to higher operating pressure, flux decline, and shortened membrane life. In this study, different simulated wastewater samples were used as feedwater to a lab‐scale RO membrane system to investigate the effect of organic matter on the removal of heavy metals. In addition, the effect of individual salts, heavy metals, and oil on scaling formation was studied. Experimental data showed that when various pollutants were added to the feedwater, the permeate flux dropped from 142.86 LMH to 45.91 LMH, and the percentages of rejection for Na+, Ca+2, Mg+2, Cu+2, Cr+3, and oil were 96.56 %, 87.5 %, 95.5 %, 100 %, 100 %, and 99.96 %, respectively. The Scanning Electron Microscope (SEM) images showed a thin fouling layer that partially covered the membrane surface where the feedwater contained only NaCl salt. In contrast, it showed a thick layer of organic fouling that entirely covered the membrane surface when the feedwater contained all the other contaminants. Moreover, the Atomic Force Microscopy (AFM) showed that when oil was added to the feedwater, numerous pores were plugged and the surface roughness of the fouled membrane was reduced to 0.91 nm. Overall, the findings showed that oil in the feedwater enhanced the removal percentages of salts and heavy metals because the removal efficiency exceeded 96 %. Furthermore, Cr+3 and oil were observed to reduce the permeate flux by 43 % and 49 %, respectively.

Membrane fouling behaviors in a full-scale zero liquid discharge system for cold-rolling wastewater brine treatment: A comprehensive analysis on multiple membrane processes

The challenge of water scarcity drives zero liquid discharge (ZLD) treatment to maximize reuse of industrial wastewater. Deciphering the characteristics and mechanisms of membrane fouling in the membrane-based ZLD system is crucial for the development of effective fouling control strategies. However, current studies only focused on the membrane fouling of single step, lacking in-depth understanding on the ZLD systems using multiple membrane processes. Herein, membrane fouling characteristics and mechanisms in a full-scale ZLD system for cold-rolling wastewater brine treatment were investigated via a comprehensive analysis on multiple nanofiltration (NF) and reverse osmosis (RO) membrane processes. The membrane fouling behaviors showed distinct characteristics along the wastewater flow direction in the ZLD system. Increasing amounts of foulants were deposited on the membrane surfaces with the sequence of the 1st pass RO, 1st stage NF, and 2nd stage NF processes. The organic fouling and silica scaling were more intensive in the 1st stage NF and 2nd stage NF for treating the brine of the 1st pass RO, as the foulants were rejected and concentrated by previous membrane processes. Severe inorganic fouling, containing amorphous SiO2, Al2O3, and Al2SiO5, occurred on the membrane surface of the 2nd pass RO membrane, due to the recirculated high-concentration silica, high water recovery, and concentration polarization. For the 3rd pass RO process, both the amounts of organic and inorganic foulants decreased dramatically, due to the low foulant concentration in its influent. This work provides a comprehensive understanding of membrane fouling in a membrane-based ZLD system, facilitating the development of membrane fouling control strategies for multiple membrane processes.

Ionic fluid as a novel cleaning agent for the control of irreversible fouling in reverse osmosis membrane processes

While a variety of chemical cleaning strategies has been studied to control fouling in membrane-based water treatment processes, the removal of irreversible foulants strongly bound on membrane surfaces has not been successful. In this study, we firstly investigated the diluted aqueous solutions of ionic fluid (IF, 1-ethyl-3-methylimidazolium acetate) as a cleaning agent for three model organic foulants (humic acid, HA; bovine serum albumin, BSA; sodium alginate, SA). The real-time monitoring of cleaning progress by optical coherence tomography (OCT) showed that fouling layer was dramatically swelled by introducing IF solution and removed by shear force exerted during cleaning. This phenomenon was induced due to the pre-existing interactions between organic foulants were weakened by the intrusion of IF into the fouling layer, which was analyzed by the measurement of adhesion forces using atomic force microscopy (AFM). In the experiments with model foulants and wastewater effluent, IF was added to alkaline cleaning agents (NaOH) to verify the applicability to be supplemented in commercial cleaning agents, and resulted in the significantly enhanced control of irreversible membrane fouling. Implication of utilizing recyclable IF with negligible volatility is that environmental effects of membrane cleaning solutions could be minimized by decreasing usage of cleaning chemicals, while increasing the cleaning efficiency.

Numerical simulations of the effect of spacer filament geometry and orientation on the performance of the reverse osmosis process

Momentum and mass transfer in reverse osmosis membrane modules must be optimized to design efficient and economical designs. The feed spacers are used to improve mixing, to minimize fouling and concentration polarization. This computational study analyses fluid flow, mass transfer, concentration polarization and pressure drop in the feed channel of a reverse osmosis membrane module with different spacer filament geometry (cylindrical, diamond, pentagonal, and triangular), orientation and Reynolds numbers. The computational model solves three-dimensional fluid flow and mass transfer while considering the complex water and solute flux boundary conditions. The cylindrical spacer filaments configurations showed the lowest water flux, followed by pentagonal, diamond, and triangular spacer filaments configurations. The concentration boundary layer thickness was high near the spacer surface due to the stagnant velocity zone. The results indicated that the concentration polarization on the membrane surface increases with a decrease in Reynolds numbers. The channel containing triangular filament spacers gave the maximum water flux and minimum concentration polarization. The spacer configurations with an attack angle of 45° and a transverse angle of 135° showed the highest water flux; however, the pressure drop was also high. The channel containing triangular spacer filament (T1A0) showed the least CP. However, the concentration boundary layer thickness was higher at the bottom side of the channel. The developed model could be useful for predicting the reverse osmosis membrane process performance.

Data driven identification of industrial reverse osmosis membrane process

A dynamic artificial neural network (ANN) is developed for the identification of an industrial reverse osmosis membrane process under fouling effect. 4-year historical data on feed properties and measured process variables in the plant were used for the ANN training and validation. The ANN considers the current and previous week's online measurements as inputs and provides one-week and two-week ahead permeate flow predictions. A sensitivity analysis is provided at various periods to determine the variables with high impact on the permeate flow, and thus the plant performance. Based on the sensitivity analysis, cartridge filter pressures and pH have the highest impact on the output. Plant operating window is also calculated under such complex multivariable and nonlinear nature. The results show quantitative and intuitive conclusions, parallel to existing literature, and provide significant insight on the identification of industrial and large-scale reverse osmosis processes.

Composition and Accumulation of Fouling during Leachate Reverse Osmosis Membrane Treatment in both a Typical Incineration Plant and a Landfill

Reverse osmosis (RO) membrane process has been extensively used for leachate treatment both in incineration plants and landfills. However, operation and maintenance costs caused by membrane pollution limit the wide application of RO membrane. In order to further understand membrane fouling, this study analyzes the influent, effluent, concentrated liquid pollutants and membrane fouling of typical waste incineration plants and landfills in Chongqing, a city in the west of China based on the comparison of three-dimensional excitation and emission matrix fluorescence (3DEEM) and nanometer particle size. In addition, this paper discusses the change law of chemical oxygen demand (COD) and main pollutants in membrane fouling in the disc tube reverse osmosis (DTRO) system in a single operation cycle, analyzes the main components of membrane fouling, and draws the accumulation of RO membrane pollutants, in order to provide a reference for understanding the composition, formation and control of membrane fouling.

Application of Nanofiltration and Reverse Osmosis in Wastewater Treatment Containing Ethylene Glycol from South Pars Gas Complex Wastewater

Today, industrial wastewater discharge has become one of the serious problems of governments. Industrial wastewater contains harmful and dangerous compounds that can endanger human health and the environment. In addition, in the oil, gas, and petrochemical industries, ethylene glycol is used for various purposes, and its removal from wastewater has become a challenge. Industries located on the shores of the Persian Gulf are one of the sources of production of this type of wastewater. In this study, the performance of Nanofiltration (NF) and Reverse Osmosis (RO) membrane processes for treatment of wastewater containing ethylene glycol (EG) from South Pars Gas Complex (SPGC) are investigated and compared. Various process parameters such as pressure, flowrate, and EG removal percentage as well as performance and characteristics of the membrane such as flux and fouling are discussed. It has been observed RO has better performance and less fouling than NF. However, the NF membrane has higher flux due to less compression. RO process achieved 80-99% and NF achieved 60-80% EG rejection during various pressure and flowrates.

Water recovery from yarn fabric dyeing wastewater using electrochemical oxidation and membrane processes.

This study intended to evaluate and compare the efficiency of electrochemical oxidation (EO), nanofiltration (NF), and reverse osmosis (RO) membranes processes in the treatment of yarn fabric dyeing wastewater (YFDW) in terms of chemical oxygen demand (COD) removal, color removal, salinity reduction, and conductivity removal. EO tests of the textile effluent were conducted under various current densities and solution pH conditions employing a graphite electrode. Membrane filtration experiments were conducted using two different NF membranes: NP010 and NP030 and two distinct RO membranes: BW30 and SW30 flat-sheet membranes. The experimental results showed that NF membrane process is not suitable for yarn fabric wastewater treatment showing low removal efficiencies for COD, color, and conductivity. However, both EO and RO membranes could reduce COD and color to high removal performances. EO results showed more than 99% of color removal and 80% of COD elimination at pH = 6 and current density of 50 mA/cm2 after 180 min of reaction. Using RO membrane for yarn fabric wastewater treatment demonstrated relatively complete removal of color concentration and 98% of COD elimination. However, EO process showed less performance in conductivity removal efficiency compared to the RO membranes. EO treatment of YFDW decreased conductivity by 31.2%, whereas RO membrane process reduced conductivity to a greater extent and recorded 97.1% of removal elimination percentage. Therefore, the treated water by RO membrane could be recycled back to the process such as washing and dyeing, in that way offering economic profits by decreasing water consumption and wastewater treatment cost. PRACTITIONER POINTS: Electrochemical oxidation and membrane filtration processes were combined for the treatment of yarn fabric dyeing wastewater (YFDW). A 100% color removal of color and 98.5% COD elimination efficiencies were obtained for the electrochemical oxidation (EO) + RO combined process. EO treatment of YFDW decreased conductivity by 32.7%, whereas the RO membrane process reduced conductivity to a greater extent and recorded 97.7% of removal elimination percentage.

A Review on Ion-Exchange Membranes Fouling during Electrodialysis Process in Food Industry, Part 2: Influence on Transport Properties and Electrochemical Characteristics, Cleaning and Its Consequences.

Ion-exchange membranes (IEMs) are increasingly used in dialysis and electrodialysis processes for the extraction, fractionation and concentration of valuable components, as well as reagent-free control of liquid media pH in the food industry. Fouling of IEMs is specific compared to that observed in the case of reverse or direct osmosis, ultrafiltration, microfiltration, and other membrane processes. This specificity is determined by the high concentration of fixed groups in IEMs, as well as by the phenomena inherent only in electromembrane processes, i.e., induced by an electric field. This review analyzes modern scientific publications on the effect of foulants (mainly typical for the dairy, wine and fruit juice industries) on the structural, transport, mass transfer, and electrochemical characteristics of cation-exchange and anion-exchange membranes. The relationship between the nature of the foulant and the structure, physicochemical, transport properties and behavior of ion-exchange membranes in an electric field is analyzed using experimental data (ion exchange capacity, water content, conductivity, diffusion permeability, limiting current density, water splitting, electroconvection, etc.) and modern mathematical models. The implications of traditional chemical cleaning are taken into account in this analysis and modern non-destructive membrane cleaning methods are discussed. Finally, challenges for the near future were identified.

Investigating techno-economic feasibility of biologically pretreated textile wastewater treatment by electrochemical oxidation process towards zero sludge concept

Reverse osmosis (RO) membrane process is extensively employed in the hybrid zero liquid discharge (ZLD) based textile wastewater treatment plants to recover water for reuse in the dyeing processes. RO membrane fouling has been the major challenge due to the existence of organic foulants in the RO feed stream as it often affects the efficiency of the RO system. To fix this issue, an electrochemical oxidation (EO) technique was attempted to remove COD and colour from the biologically pre-treated textile wastewater as an advanced oxidation process. This study was performed using a small reactor setup with titanium (Ti) and stainless steel (SS 304) as an anode and cathode respectively. Reduction in COD and colour was obtained as 64% and 90% respectively at an electrolysis time of 3 min. The specific energy (Esp) consumption was estimated to be 19.16 kW h/ kg COD and 3.06 kW h/ m3 of influent. Cost-benefit analysis with factors like capital expenditure (Capex), operating expenditure (Opex), savings and pay-back period was carried out. The gross and net unit treatment costs of EO were 0.56$/m3 and 0.20$/m3 of influent respectively with the pay-back period of 1.90 years. Similarly, the gross and net treatment costs of EO on processing cost of dyed fabric were estimated to be 0.028$/kg and 0.011$/kg respectively. Cost analysis showed a considerable savings in costs associated with wastewater treatment and dyed fabric production, while zeroing of solid waste was achieved by adopting the EO process.

Parallel study on removal efficiency of pharmaceuticals and PFASs in advanced water treatment processes: Ozonation, GAC adsorption, and RO processes

We aimed to assess the removal efficiencies of four pharmaceuticals (carbamazepine, crotamiton, metformin, and sulfamethoxazole) and four poly- and perfluoroalkyl substances (PFASs) (PFHxA, PFHxS, PFOA, and PFOS) by lab-scale ozonation, granular activated carbon (GAC) adsorption, and reverse osmosis (RO) membrane processes under varying operating conditions. Ozonation and GAC adsorption processes were conducted at two temperatures (5 and 25°C) and three pH conditions (3, 7, and 11). The membrane process was performed using an unstirred cell with two different RO membranes. The most pharmaceuticals were effectively removed by ozonation, whereas metformin and PFASs were unaffected due to their stable chemical structures. In the GAC process, metformin was hardly removed under acidic conditions but it was enhanced by over 90%. PFASs were effectively removed by GAC adsorption and RO membrane processes. The RO membrane for brackish water treatment showed higher rejection than that for residential water treatment. Moreover, the rejection of PFAS increased as the molecular weight increased. A strategy was found to effectively remove the remaining metformin in most advanced water treatment processes. Chemically persistent PFASs were hardly removed by the ozonation process but were effectively removed by physical treatments such as GAC adsorption and RO membrane processes.

Irrigation with permeates to upgrade the quality of red pepper: a case study in Arava region, Israel

ABSTRACT Management of environmental resources presents challenges across agricultural production. In the case of the semi-arid region of Arava Valley in Israel, irrigation with groundwater brackish water is a widespread practice that has severe limitations. In this research studies are taking place for brackish groundwater upgrading for unrestricted use for the irrigation and sustainable agricultural production. The treatment system applies two main treatment stages: nanofiltration and reverse osmosis membrane process and, the pilot system with a capacity of around 1 m3/hr. Different mixtures of nanofiltration and reverse osmosis, Brackish and potable permeates are then applied for the irrigation of pepper crops. The field results with the graphical visualization approach using total ranking, multi-dimensional scaling, and clustering technique show that the conventional brackish feed water produces good results of relaxation time, total soluble solids and Vitamin C content. Treatment system using hybrid nanofiltration and reverse osmosis technology improves product quality related to the relative fruit colour red shade.

Preliminary investigation into the claims of the IBROM system

Abstract Membrane filtration is commonly applied to reduce dissolved organic carbon (DOC) to control the formation of trihalomethanes (THMs); however, high levels of DOC can cause severe fouling of reverse osmosis membranes. The integrated biological and reverse osmosis membrane (IBROM) process is a combination of biological filters and reverse osmosis membranes. The IBROM process claims to remove biodegradable dissolved organic carbon (BDOC), which apparently should result in reduced membrane fouling. The goal of this research was to conduct a preliminary investigation into the claims of the IBROM system, using water collected from the Herbert water treatment plant (Saskatchewan). The plant is utilizing the IBROM for the treatment of a dugout and groundwater blend (DOC of 17.5–22.7 mg/L). The results demonstrated that BDOC concentrations did not change significantly throughout the plant. Optimized laboratory-scale coagulation with polyaluminium chlorohydrate achieved 58% removal of BDOC. Oxidation with permanganate increased the concentration of BDOC (from 5.7 to 8.8 mg/L). Overall, BDOC was effectively removed by optimized coagulation rather than the IBROM system. Moreover, the results show an inverse relationship between BDOC and THMs formation potential (THMFP) in both coagulated and oxidized water. For all concentrations, more biodegradable DOC had less tendency to form THMs based on the lower THMFP.