Reverse Osmosis Membrane System Research Articles

Down flow jet-loop reactor with NF-RO membrane system for the treatment of textile wastewater

Textile industries are significant consumers of fresh water, extensively using it for washing and dyeing processes. The effluent from these operations contains various chemicals, including complex synthetic dyes, NaCl and Na2SO4 necessitating efficient treatment before discharge into water bodies. Zero Liquid Discharge (ZLD) technology facilitates complete water recovery but leads to substantial solid waste accumulation, which poses challenges for reutilization. This study introduces an innovative approach using a Downflow Jet Loop Reactor combined with ozone and activated carbon to effectively remove color and Chemical Oxygen Demand (COD) from textile effluent. Furthermore, a combination of Nanofiltration (NF) and Reverse Osmosis (RO) membrane systems ensures comprehensive purification by effectively separating inorganic salts. Experimental results demonstrated a maximum color removal of 81.25 % from the textile effluent. The fabricated PSF/PVDF NF membrane exhibited exceptional capacity for rejecting divalent salts. Additionally, the RO reject, which is a concentrated solution of salts and contaminants, was successfully reused in a dye bath for cotton fabric dyeing. This approach highlights the practicality, sustainability, and resource conservation potential within the textile production cycle. It underscores the importance of a comprehensive water treatment strategy for achieving sustainable textile production.

Application of Online Flow Cytometry for Early Biofouling Detection in Reverse Osmosis Membrane Systems

Biofouling poses a significant challenge to reverse osmosis (RO) membrane systems, necessitating timely detection for effective control. This study evaluated the efficacy of flow cytometry (FCM) for early biofilm detection in comparison to conventional system performance indicators. Feed channel pressure drop and total cell concentration in the Membrane Fouling Simulator (MFS) flowcell cross-flow outlet water were monitored over time as early biofouling indicators. The results demonstrated the potential of increased bacterial cell concentration in cross-flow outlet water as a reliable indicator of biofouling development on the membrane. Water outlet monitoring enabled faster biofouling detection compared to feed channel pressure drop. Membrane autopsy confirmed biofilm presence prior to the pressure drop increase, highlighting the advantage of early detection in implementing corrective measures. Timely intervention reduces operational costs and energy consumption in membrane-based processes.

Insights of membrane fouling under scale inhibitor synergistic condition monitored by ultrasonic phased array: Fouling spatial and density characteristics

Achieving accurate dosing of scale inhibitors in full reverse osmosis (RO) membrane systems for industrial applications is a critical challenge due to a lack of understanding of membrane fouling characteristics. To address this, this study investigated membrane performance at different inhibitor concentrations and proposed a method using ultrasonic phased arrays (UPA) to evaluate the fouling layer's spatial and density characteristics. The study also examined the relationship between fouling reversibility and compaction, and the results showed a clear conversion process from inhibition to exacerbation of membrane fouling by scale inhibitors. Additionally, the fouling layer distribution characteristics were opposite at different concentrations. At insufficient concentrations, the scaling layer forms near the outlet and spreads to the far-end with a continuously decreasing thickness. Conversely, at surplus concentrations, the opposite effect was observed. At sufficient concentrations, the fouling layer thickness and range exhibited a discontinuous distribution. The high-density layer was dominant on the membrane surface and showed low fouling reversibility. However, scale inhibitors were found to minimize fouling density by interfering with ion deposition, reducing the ion content and significantly increasing its reversibility. These findings have significant implications for scale inhibitor efficiency evaluation and scientific application, which can improve industrial membrane system performance.

Performance and fouling characteristics in a pilot-scale reverse osmosis membrane system for microelectronic wastewater treatment

The microelectronic industry faces the significant challenge of managing vast volumes of wastewater containing toxic and harmful pollutants. While the Ultrafiltration-Reverse Osmosis (UF-RO) system has gained recognition as a potential solution for the reclamation and reuse of such wastewater, there is a lack of comprehensive understanding on its performance and membrane fouling conditions in the context of actual microelectronic wastewater. In this study, we continuously monitored the performance of a pilot-scale UF-RO system treating microelectronic wastewater. The RO membrane was subject to autopsy characterization at the end of its operation. The UF pretreatment performance remained consistent, with the UF-RO system showcasing high removal efficiency (>99.5 %) for tetramethylammonium hydroxide (TMAH), the primary pollutant in the microelectronic wastewater. Inorganic, organic, and biofouling were identified on the membrane surface, with the biofouling as the predominant form. A microbial community analysis showed that Proteobacteria and Bacteroidetes were the dominant bacteria on the membrane surface at the phylum level, while Alicycliphilus, Chryseobacterium, and Flavobacterium were predominant at the genus level. Fouling characteristics and degrees varied across the four stages, with the fouling in the 2nd stage being the most severe. Interestingly, an increased concentration of TMAH in the influent of the 4th stage seemed to inhibit the development of biofouling to some extent. This study offers valuable insights into the practical performance of the pilot-scale UF-RO technology when treating microelectronic wastewater and lays the groundwork for developing strategies to address membrane fouling concerns within the microelectronics industry.

Reverse osmosis desalination combining feed flow reversal with permeate flush for mitigation of mineral scaling

The performance of a spiral-wound reverse osmosis (RO) membrane system, operating in a cyclic mode of normal feed flow (NFF)-feed flow reversal (FFR), was evaluated for desalting feed water of high gypsum mineral scaling potential. The membrane system, with six membrane elements in series, was operated without antiscalant dosing at the condition of gypsum supersaturation at the membrane surface of the tail RO element. Automated NFF/FFR switching was triggered by an optical membrane monitoring system (MMS) installed at the last membrane element. This element alternated from being the tail to lead element at NFF and FFR modes, respectively. Multicycle NFF/FFR operation demonstrated partial cycle-to-cycle restoration of the permeate flux. However, progressive flux decline was noticeable with increased NFF/FFR cycles. Complete restoration of element productivity (in terms of permeate flux) was attained via permeate flushing (at the early membrane scaling stage) owing to gypsum scale dissolution. The study results suggest that NFF/FFR RO operation under conditions of high mineral scaling potential can be effectively combined with periodic permeate flushing. However, establishing the long-term approach feasibility will require a strategy for optimizing the frequency of NFF/FFR switching and permeate flushing in relation to the feed water quality and desalting operating conditions.

CFD simulation of hydrodynamics and concentration polarization in osmotically assisted reverse osmosis membrane systems

Osmotically assisted reverse osmosis (OARO) has been recently suggested as an alternative to improve water recovery of reverse osmosis (RO) for applications in which RO has reached its limit. To elucidate the physics, a computational fluid dynamics (CFD) methodology is developed that describes all important physical phenomena occurring in the feed, porous and draw sides of OARO. The CFD model shows good agreement with the reported experimental data and predicts the water flux better than a simplified analytical model. This paper reveals that external concentration polarization (ECP) at the feed side is more important than internal concentration polarization (ICP) within the porous support layer, especially for a system with a high transmembrane pressure, Δp (≥40 bar). In contrast to conventional RO, where concentration polarization (CP) at the permeate side is negligible, OARO experiences a non-negligible ECP at the draw (permeate) side, particularly in cases with high Δp. This analysis also found that both counter-current and co-current configurations show similar flux performance at module scale.

Optimizing cleaning strategies for biofouling in reverse osmosis membrane systems: A comparative study using a self-formed instrument

Membrane biofouling poses a serious challenge in reverse osmosis (RO) plants used for water recovery, which cannot be addressed by traditional chlorine-based cleaning agents. To accommodate this problem and enhance membrane performance while maintaining high-quality water production, various cleaning strategies have been applied. It remains however challenging to identify optimal cleaning agents, as tests require discontinuation of production to evaluate the effect. This study introduces a self-formed instrument that mimics industrial RO plants on a small scale to compare the cleaning agents in a fast, affordable and feasible approach. The setup was demonstrated using three cells operating in parallel and a thorough comparison of these. Specifically, the online cleaning efficiency of a typical biofouling cleaner, a solution of NaOH/sodium dodecyl sulfate (SDS), and the commonly used non-oxidizing biocide, 2,2-dibromo-3-nitrilopropionamide, were compared to validate the system performance when fed with membrane bioreactor effluent. The effectiveness of the cleaning process was evaluated using a combination of hydrodynamic operation and membrane autopsy to estimate the biofoulant amount and composition. During a 7-day operating period, it was observed that treated membranes demonstrated higher flux rates compared to untreated membranes. The normalized flux increased more than double in the membrane after it had been cleaned with NaOH/SDS solution. CLSM analysis clearly showed the distinct effects of the two cleaning solutions on the amount and spatial structure of the biofilm layer. Cleaning with DBNPA was able to reduce the load of living bacteria, but not necessarily remove the biofilm components completely. Comparative analyses of membranes revealed that NaOH/SDS exhibited the highest cleaning efficiency during the online cleaning operation mode. This benchmark highlights the versatility of the system, which can be assembled at relevant sites and assist in the identification of efficient and eco-friendly agents that promote the lifespan of membranes. With the distribution of this instrument, it will be possible to accelerate the investigation of multiple cleaning strategies and also analyze interactions among cleaning agents in an attempt to reduce water shortage.

Pemberdayaan Masyarakat Berbasis Teknologi Melalui Penerapan Mesin Reverse Osmosis (RO) pada Usaha Depot Air Isi Ulang BUMDesa Unggul Sari

This service activity aims to empower the community through the introduction of PDAM water treatment technology into suitable water for consumption in the form of applying Reverse Osmosis (RO) 200 GDP to BUM refill water depot businesses in Unggul Sari Village, Wonosari Village, Bengkalis Regency. The method of implementing this service used participatory training and mentoring. Evaluation of this service used was the Community Service Management standard listed in Permenristekdikti Number 44 of 2015. This community service activity resulted in the realization of a BUM Unggul Sari Village BUM refill water depot business, Wonosari Village, with a refillable water production capacity of 65 gallons per day. In addition, partners could operate technology with a Reverse Osmosis membrane system.

An advanced treatment process for 3-high wastewater discharged from crude oil storage tanks.

The wastewater discharged from crude oil storage tanks (WCOST) contains high concentrations of salt and metal iron ions, and high chemical oxygen demand (COD). It belongs to "3-high" wastewater, which is difficult for purification. In this study, WCOST treatments were comparatively investigated via an advanced pretreatment and the traditional coagulation-microfiltration (CMF) processes. After WCOST was purified through the conventional CMF process, fouling occurred in the microfiltration (MF) membrane, which is rather harmful to the following reverse osmosis (RO) membrane unit, and the effluent featured high COD and UV254 values. The analysis confirmed that the MF fouling was due to the oxidation of ferrous ions, and the high COD and UV254 values were mainly attributable to the organic compounds with small molecular sizes, including aromatic-like and fulvic-like compounds. After the pretreatment of the advanced process consisting of aeration, manganese sand filtration, and activated carbon adsorption in combination with CMF process, the removal efficiencies of organic matter and total iron ions reached 97.3% and 99.8%, respectively. All the water indexes of the effluent, after treatment by the advanced multi-unit process, meet well the corresponding standard. The advanced pretreatment process reported herein displayed a great potential for alleviating the MF membrane fouling and enhanced the lifetime of the RO membrane system in the 3-high WCOST treatment.

Fouling of reverse osmosis membrane: Autopsy results from a wastewater treatment facility at central park, Sydney

Membrane fouling is an inevitable phenomenon and common issue in Reverse Osmosis (RO) membrane systems used for water reclamation. Severe membrane fouling in RO system could consequently increases the operation cost as it requires frequent membrane chemical cleaning process thus consuming more chemical agents and shorten lifespan of RO membrane module. In this study, potential foulants of RO membranes that are used at Sydney's urban wastewater recycling facility which treated for domestic and commercial wastewaters, were investigated via membrane autopsy method. The three-year-old spiral wound RO membrane modules were taken from the site for membrane autopsy and to investigate major fouling factors as well as in-depth study of fouling mechanisms throughout various characterization methods. Additionally, a flux recovery rate of fouled RO membranes via the chemical cleaning was also examined using different kind of chemical cleaning agents to find a most effective chemical cleaning combination.

Financial, Economic, and Environmental Analyses of Upgrading Reverse Osmosis Plant Fed with Treated Wastewater

One of the most effective strategies to mitigate water shortages worldwide is to reuse treated wastewater for freshwater production employing reverse osmosis (RO) technology. This strategy is appropriate in urban areas of arid or semi-arid regions as it can provide a sustainable and reliable water source close to the consumers. One of the drawbacks of RO is the high variability of production costs due to the electricity intensity. In addition, depending on the electricity source, it can also result in substantial environmental costs. This study showed that upgrading pumping and RO membrane systems of a wastewater reuse plant in Cyprus can significantly alleviate these drawbacks in terms cost, water recovery rate, and air pollution. The water-recovery rate of the upgraded RO plant increased from 43.2 to 75 percent, which resulted in a substantial net financial benefit due to the reduction in the quantity of wastewater purchased and the increase in potable water produced. The upgraded system also reduced the electricity requirement from 3.63 kWh/m3 to 1.92 kWh/m3. Pollution emissions decreased substantially because of the reduction in electricity requirements. The beneficiaries of these lower emission costs are the residents of Cyprus and global society. Overall, the benefit of upgrading the plant is highly attractive with more than 65 percent annual real internal rates of return in financial and economic terms. Positive net present values are realized for all the scenarios considered.

Efficacy testing of non-oxidizing biocides for polyamide membrane biofouling prevention using a modified CDC biofilm reactor

AbstractBiofouling is one of the most challenging obstacles faced by reverse osmosis (RO) membrane systems to supply potable water. Currently, biofouling is imperfectly handled by RO feed water pre-chlorination, which is associated with the production of carcinogenic disinfection by-products. To propose a safer alternative to control biofouling in RO drinking water applications, this study investigates the efficacy of five biocides to prevent and remove Pseudomonas aeruginosa biofilms from RO membranes: 2-methyl-4-isothiazolin-3-one (MIT); 2,2-dibromo-3-nitrilopropionamide (DBNPA); sodium bisulfite (SBS); sodium benzoate (SB); and ethyl lauroyl arginate (LAE). Experiments were conducted on the Center for Disease Control (CDC) Biofilm Reactor (CBR) with biocidal dosing estimated on 96-well microtiter plates. Confocal Scanning Laser Microscopy (CLSM) and Scanning Electron Microscopy (SEM) were used to analyze the biocides' anti-biofilm efficacies under dynamic conditions relative to minimum biofilm inhibitory and eradication concentrations. The results in this study indicated that LAE presented the best anti-biofilm efficacies in treating P. aeruginosa biofilms when compared to all studied biocides; it not only prevented biofilm formation (>98%) but also it effectively removed pre-established biofilms (>99%) from RO membrane coupons. Therefore, due to safety and efficacy, LAE is an excellent candidate for controlling biofouling in drinking water RO membrane systems.

Supercomputing and machine learning-aided optimal design of high permeability seawater reverse osmosis membrane systems

Concentration polarization (CP) should limit the energy and cost reducing benefits of high permeability seawater reverse osmosis (SWRO) membranes operating at a water flux higher than normal one. Herein, we propose a multiscale optimization framework coupling membrane permeability, feed spacer design (sub-millimeter scale) and system design (meter scale) via computational fluid dynamics and system level modeling using advanced supercomputing in conjunction with machine learning. Simulation results suggest energy consumption could be reduced by 27.5% (to 1.66 kWh m−3) predominantly through the use of high permeability SWRO membranes (12.2%) and a two-stage design (14.5%). Without optimization, CP approaches 1.52 at the system inlet, whereas the optimized CP is limited to 1.20. This work elucidates the optimized permeability, module design, operating scheme and benefits of high permeability SWRO membranes in seawater desalination.

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.

Operation of Different Reverse Osmosis (RO) Membrane Modules for the Treatment of High-Strength Wastewater to Enhance the Recovery of Clean Water—A Case Study in Bac Ninh, Vietnam

In this study, a wastewater treatment plant (WWTP) in Vietnam receiving high-strength wastewater with COD of about 30,000 mg/L and various heavy metals from industries was treated by different RO membrane modules in order to meet the stringent national discharge standard and recover wastewater for reuse. The Fenton and coagulation pre-treatments were employed based on optimal conditions, which were experimentally pre-determined. For the RO membrane system, the two-stage treatment employed a plate frame RO (PFRO) followed by spiral wound RO (SPRO) to obtain high-quality permeate, while the high-pressure PFRO (HP PFRO) module was employed for the recovery of concentrated streams from the PFRO unit. As a result, a significant COD removal efficiency of 99.62% was achieved in the SPRO module. The heavy metal concentrations (i.e., Cu, Fe, Zn, Mn, Cr) measured in the output mostly met the standards for discharge levels. A significant decrease in electrical conductivity (EC) to below 250 µS/cm was achieved. In addition, high rates of water recovery were achieved from the RO modules (i.e., PFRO 63%, HP PFRO 9–12%, SPRO > 80–90%). The high-quality treated wastewater was thus suitable for reuse purposes. This study highlights the feasibility of RO membranes for practical treatment of high-strength wastewater and provides valuable data for the WWTP operator.

Impact of large-scale effects on mass transfer and concentration polarization in Reverse Osmosis membrane systems

We present well-resolved computational fluid dynamics simulations of a large-scale reverse osmosis membrane-spacer configuration (∼ 1 m). Our computational model solves the flow and transport equations with variable solute-dependent properties. We utilize a high resolution computational mesh to resolve all relevant length scales associated with spacer-induced mixing and thin concentration boundary layers. An important contribution of this work is the development of a modified mass-transfer correlation that accounts for the development of the concentration boundary layer along the channel. A set of 2D axisymmetric simulations were performed for a spiral wound module layer with varying cross-flow conditions and spacer diameters which indicate a significant entrance length effect for concentration profile development at lower flow rates while mixing effects dominate at higher flow rates. The mass-transfer correlations at higher flow rates compare well with published correlations while a surrogate model for Sherwood number was obtained that depends on an additional similarity variable that accounted for entrance length effects at lower flow rates. Finally, a large-scale membrane-spacer design relevant to high-pressure reverse osmosis is studied with a non-uniform arrangement of spacers, which indicate a substantial saving in pressure drop (∼ 40%) compared to traditional uniformly spaced pattern with minor variations (∼ 2%) in concentration polarization, product water quality (∼ 1%) and water recovery (∼ 7%) compared to a uniform spacer pattern.

Monitoring and Evaluation of the Performance of Reverse Osmosis Membrane Systems for the Treatment of the Central Danone Plant

The objective of the present work is to monitor and control the physicochemical quality of the osmosis water that feeds the dairy industry in our case the Danone plant (DP) "Factory of Salé", for good production and use without no risk. The drilling water treatment and purification technique applied in the Danone plant is reverse osmosis. The approach of this membrane technique at a pressure gradient, allows obtaining good quality water for use in the various activities of the plant. During a 30-day period, we tested the pH, conductivity, alkalinity, hydrometric title, total alkalinity, chlorides content and chlorine content on water drawn from the borehole, the 1μ filter output, the treated output A and the treated water. The results of the experimental analyzes generally comply with the standards imposed within the plant, with the exception of a few days where cleaning of the membranes is necessary.

Reverse osmosis membrane biofouling: causes, consequences and countermeasures

Biofouling has been referred to as “the Achilles heel” of reverse osmosis (RO) membrane technology; the main cause being polyamide RO membranes lack of chlorine tolerance. Biofouling increases the operating cost of water treatment by increasing RO system feed pressure (i.e., energy demand) and increasing membrane cleaning frequency, which increases downtime and reduces membrane useful life. For waters with known high biofouling potential, plant designs also may require more extensive pretreatment, which increases capital and operating costs as well as the footprint of a desalination plant. It is known from the literature that the three keys to fending off biofouling in RO systems and/or recovering from biofouling once it takes root include (1) understanding site-specific processes governing biofilm formation, (2) implementing effective biofouling pretreatment ahead of RO membranes, and (3) monitoring biofouling to enable more proactive and effective RO membrane cleaning. Herein, we present four case studies of RO membrane biofouling in seawater, municipal wastewater, brackish groundwater and industrial wastewater. Next, we describe what is known about the causes and consequences of bacterial biofilm formation and growth through a process level RO membrane biofouling model. Finally, we review common biofouling control methods including pre-treatment, chemical cleaning and the most common strategies for monitoring biofouling in RO membrane systems.

High-efficiency contaminant removal from hospital wastewater by integrated electrocoagulation-membrane process

In this work, high removal of contaminants in hospital wastewater has been achieved using an integration of electrocoagulation (EC) with ultrafiltration (UF) and reverse osmosis (RO). In EC system, Al electrodes were arranged in a monopolar-parallel and bipolar configuration. There are two parameters studied in the EC system, i.e., the configuration of electrodes (2A-2C-2B and 4A-2C-2B) and current densities. The EC-UF system with a configuration of 4A-2 C-2B and a current density of 88.5 A.m−2 resulted in high removal of TSS, TDS, BOD, and COD by 95.12 %, 97.53 %, 95.18 %, and 97.88 %, respectively. The effluent quality of the EC-UF was improved by substituting UF with RO membrane. The TSS, TDS, BOD, and COD removal were enhanced to 97.64 %, 99.85 %, 97.88 %, and 98.38 %, respectively. The permeate flux decline in UF membrane system was 47.83 % during 60 min of filtration time due to cake layer fouling on the membrane surface, while in the RO membrane system was 29.49 %. Since the EC-UF and EC-RO showed high efficiency in contaminants removal, these configurations could be used as clean technology to produce clean water for water reuse purposes. At a wastewater capacity of 5 m3.day−1, the operating cost for the EC-UF system was 3.92 US$.m−3, while the EC-RO system was 4.02 US$.m−3. The increase of wastewater capacity to 50 m3.day−1 reduced the operating cost to 0.89 US$.m−3 for the EC-UF system and 0.93 US$.m−3 for the EC-RO system.

Design and Testing of a Separation and Desalination Device for Farmland Saline-Alkaline Water in Arid Areas.

To solve the problem of soil salination and to desalinate saline–alkaline water in arid areas, this study involved the design and testing of a separation and desalination device for farmland saline–alkaline water that is suitable for arid areas. The results of this study indicate that after the pretreatment of farmland saline–alkaline water, the water yielded by the pretreatment device had a mean turbidity of <1 and a mean silt density index (SDI) of <3, which met the working conditions of nanofiltration (NF) and reverse osmosis (RO) membranes. When used to filter saline–alkaline water, the composite NF–RO membrane system achieved a desalination rate of 97.06%, a total hardness removal rate of 97.83%, and a Cl− removal rate of 99.65%, which satisfied the standard for irrigation water quality. Some indicators of the yielded water reached the hygienic standard for drinking water, thus successfully reutilizing water resources. The circulating solar collector tube of the device was designed with a collection area of 6 m2, which could basically satisfy the heat demand of the flash tank for distillation. The design of the flash tank and the shell-and-tube circulating condenser met the requirements for vapor condensation. The crystals in the solar salt box precipitated under solar action. X-ray diffraction was used to identify the primary compound of the crystals as NaCl, suggesting that the precipitates have potential value as industrial salts. This study offers new technical references and helpful engineering guidance for arid saline–alkaline enrichment areas facing the problem of saline farmland irrigation water.