Inhibition of CaCO_3 Scaling in Reverse Osmosis System by Zinc Ion

Scaling of reverse osmosis (RO) membrane surface is one of the main problems in desalination proc- esses. To mitigate scales, organic anti-scalants are often used. If the dosages of anti-scalants are reduced, by using other much cheaper scale inhibitors, RO running cost will decrease greatly. The present paper investigated the inhi- bition of CaCO3 precipitation by zinc ions in RO system. The results show that the zinc ion concentration of 2mg?L-1 was able to exert a marked suppression effect on both bulk precipitation of CaCO3 and on membrane scaling on waters of moderate hardness.

Energy Recovery Device with a Fluid Switcher for Seawater Reverse Osmosis System

Energy recovery device （ERD） is an important part of the seawater reverse osmosis （SWRO） desalination system. There are principally two kinds of ERDs, the centrifugal type and the positive displacement （PD） type. The PD type is of extensive concern and is preferred in large-scale plants. In this article, an innovative fluid switcher was presented and a two-cylinder hydraulic energy recovery unit with a lab-scale fluid switcher was set up. Tap water was used as the working medium instead of the actual seawater and brine in SWRO desalination plants. Under steady state operating conditions, the experimental results were obtained on the variations of the pressure and flow rate to and from the energy recovery unit. The hydraulic recovery efficiency （En） of the energy recovery unit with the fluid switcher reached up to 76.83%.

Piloting Study on Biofouling Control of Reverse Osmosis System in Steel Mill Wastewater Reuse

The biofouling of RO （Reverse Osmosis） system is one of the most common problems in highly contaminated demineralization and wastewater reuse system. The biological fouling occurs due to the bacteria growth and proliferation under nutritive environment, resulting in a dramatic increase of dP （differential pressure） in the RO system, which requires frequent system shutdown for cleaning. This paper discusses the effectiveness of low-dP RO element and periodic flushing on the biofouling scheme of industrial steel mill wastewater reuse system. The low-dP RO element is able to provide low RO system dP, which is expressed to be lower biofouling starting point during the industrial system operation. However, the periodic flushing utilizes fresh water to remove the biofilm deposit along with feed channel. The long term operation performance demonstrated strong caustic is effective in removing the biofilm and recovering RO system performance. It is experimentally validated that, in the case of a high biofouling environment, low-dP RO element and periodic flushing is able to extend the cleaning cycles by 36.6% and 11.4%, respectively. Meanwhile, a joint application of both methods is proven to improve the biofouling control and extend the cleaning cycle by 62.5%, as compared to standard RO technology.

Impacts of Climate Change on Seawater Temperature and Total Dissolved Solids: Challenges and Sustainable Solutions for Reverse Osmosis Desalination in the Arabian Gulf Region

This article examines the influence of seawater temperature and total dissolved solids (TDS) on reverse osmosis (RO) desalination in the Arabian Gulf region, with a focus on the impact of climate change. The study highlights the changes in seawater temperature and TDS levels over the years and discusses their effects on the efficiency and productivity of RO desalination plants. It emphasizes the importance of monitoring TDS levels and controlling seawater temperature to optimize water production. The article also suggests various solutions, including intensive pre-treatment, development of high-performance membranes, exploration of alternative water sources, and regulation of discharges into the Gulf, to ensure sustainable water supply in the face of rising TDS levels and seawater temperature. Further research and comprehensive monitoring are recommended to understand the implications of these findings and develop effective strategies for the management of marine resources in the Arabian Gulf.

Microbial Removal from Secondary Treated Wastewater Using a Hybrid System of Ultrafiltration and Reverse Osmosis

The efficiency of advanced membranes towards removal of general and specific microbes from wastewater was investigated. The treatment included a subsequent system of activated sludge, ultrafiltration （hollow fibre membranes with 100 kDa cut-off, and spiral wound membranes with 20 kDa cut-off）, and RO （reverse osmosis）. The removal evaluation of screened microbes present in treated wastewater showed that hollow fibre membrane rejected only 1 log （90% rejection） of the TPC （total microbial count）, TC （total coliforms）, and FC （faecal coliforms）. A higher effectiveness was observed with spiral wound, removing 2-3 logs （99%-99.9%） of TPC and complete rejection of TC and FC. The RO system was successful in total rejection of all received bacteria. The removal evaluation of inoculated specific types of bacteria showed that the hollow membranes removed 2 logs （99%） of inoculated E. coli （10^7-10^8 cfu/mL inoculum）, 2-3 logs （99%-99.9%） of Enterococus spp. （10^7-10^10 cfu/mL inoculum）, 1-2 logs （90%-99%） of Salmonella （10^8-10^10 cfu/mL inoculum） and 1-2 logs （90%-99%） of Shigella （10^5-10^6 cfu/mL inoculum）. The spiral wound was significantly efficient in rejecting further 3 logs of E. coil, 5 logs of Enterococus spp., 4 logs of Salmonella, and a complete rejection of all received bacteria was accomplished by RO membrane. The results indicate that Gram positive bacteria were removed much more efficiently compared to the Gram negative ones, the rationale behind such behaviour is based on cell walls elasticity.

Performance Prediction of a Reverse Osmosis Desalination System Using Machine Learning

One of the major challenges that membrane manufacturers, commercial enterprises and the scientific community in the field of membrane-based filtration or reverse osmosis (RO) desalination have to deal with is system performance retardation due to membrane fouling. In this respect, the prediction of fouling or system performance in membrane-based systems is the key to determining the mid and long-term plant operating conditions and costs. Despite major research efforts in the field, effective methods for the estimation of fouling in RO desalination plants are still in infancy, for example, most of the existing methods, neither consider the characteristics of the membranes such as the spacer geometry, nor the efficiency and the day to day chemical cleanings. Furthermore, most studies focus on predicting a single fouling indicator, e.g., flux decline. Faced with the limits of mathematical or numerical approach, in this paper, machine learning methods based on Multivariate Temporal Convolutional Neural networks (MTCN), which take into account the membrane characteristics, feed water quality, RO operation data and management practice such as Cleaning In Place (CIP) will be considered to predict membrane fouling using measurable multiple indicators. The temporal convolution model offers one the capability to explore the temporal dependencies among a remarkably long historical period and has potential use for operational diagnostics, early warning and system optimal control. Data collected from a Desalination RO plant will be used to demonstrate the capabilities of the prediction system. The method achieves remarkable predictive accuracy (root mean square error) of 0.023, 0.012 and 0.007 for the relative differential pressure and permeates Total Dissolved solids (TDS) and the feed pressure, respectively.

Performance of Nanofiltration and Reverse Osmosis Membranes in Metal Effluent Treatment

The performance of different nanofiltration （NF） and reverse osmosis （RO） membranes was studied in treating the toxic metal effluent from metallurgical industry. The characteristics and filtration behavior of the processes including the wastewater flux, salt rejection and ion rejection versus operating pressure were evaluated. Then the wastewater flux of RO membrane was compared with theoretical calculation using mass transfer models, and good consistency was observed. It was found that a high rejection rate more than 95% of metal ions and a low Chemical Oxygen Demand （COD） value of 10 mg·L^-1 in permeate could be achieved using the RO composite membrane, while the NF rejection of the salt could be up to 78.9% and the COD value in the permeate was 35 mg·L^-1. The results showed that the product water by both NF and RO desalination satisfied the State Reutilization Qualification, but NF would be more suitable for large-scale industrial practice, which offered significantly higher permeate flux at low operating pressure.

Substrate matters:The influences of substrate layers on the performances of thin-film composite reverse osmosis membranes

Thin-film composite(TFC) reverse osmosis(RO) membranes are playing the dominating role in desalination.Tremendous efforts have been put in the studies on the polyamide selective layers. However, the effect of the substrate layers is far less concerned. In this review, we summarize the works that consider the impacts of the substrates, including pore sizes, surface hydrophilicity, on the processes of interfacial polymerization and consequently on the morphologies of the active layers and on final RO performances of the composite membranes. All the works indicate that the pore sizes and surface hydrophilicity of the substrate evidently influence the RO performances of the composite membranes. Unfortunately, we find that the observations and understandings on the substrate effect are frequently varied from case to case because of the lack of substrates with uniform pores and surface chemistries. We suggest using track-etched membranes or anodized alumina membranes having relatively uniform pores and functionalizable pore walls as model substrates to elucidate the substrate effect.Moreover, we argue that homoporous membranes derived from block copolymers have the potential to be used as substrates for the large-scale production of high-performances TFC RO membranes.

Study of reverse osmosis membranes fouling by inorganic salts and colloidal particles during seawater desalination

Fouling phenomenon is considered among the major reasons that cause significant increase of operating cost of desalination plants equipped with reverse osmosis(RO)membranes.This phenomenon is studied in the present work in the case of RO polyamide aromatic membranes using model seawater containing inorganic salts and colloidal compounds.Different solubility conditions of CaCO3 and CaSO4 were applied to study RO performances with and without colloid presence.During experiments,the membrane permeate fluxes were continuously monitored.Moreover,studies of chemical composition,structure,and morphology of the materials deposited on the membrane surface were conducted using energy dispersive microanalysis(EDS)X-ray diffraction and scanning electronic microscopy(SEM).Results show that in conditions of calcium carbonate oversaturation there is a reduction in the permeate flow of 11.2%due to fouling of the membrane by the precipitation of this compound.While in the same conditions of calcium sulphate oversaturation the reduction of the flow is 5%,so we can conclude that in conditions of oversaturation of both salts,calcium carbonate produces a greater fouling of the membrane that in its view causes greater decrease in the flow of permeate.All this based on the results of the test with both salts in oversaturated conditions.Resulting in the formation of calcite and gypsum crystals onto the membranes as XRD analyses stated.Additional presence of colloidal silica in those conditions intensifies strongly the fouling,leading until to 24.1%of permeate flux decrease.

Recent advances in nanofiltration,reverse osmosis membranes and their applications in biomedical separation field

In the face of human society's great requirements for health industry,and the much stricter safety and quality standards in the biomedical industry,the demand for advanced membrane separation technologies continues to rapidly grow in the world.Nanofiltration(NF)and reverse osmosis(RO)as the highefficient,low energy consumption,and environmental friendly membrane separation techniques,show great promise in the application of biomedical separation field.The chemical compositions,microstructures and surface properties of NF/RO membranes determine the separation accuracy,efficiency and operation cost in their applications.Accordingly,recent studies have focused on tuning the structures and tailoring the performance of NF/RO membranes via the design and synthesis of various advanced membrane materials,and exploring universal and convenient membrane preparation strategies,with the objective of promoting the better and faster development of NF/RO membrane separation technology in the biomedical separation field.This paper reviews the recent studies on the NF/RO membranes constructed with various materials,including the polymeric materials,different dimensional inorganic/organic nanomaterials,porous polymeric materials and metal coordination polymers,etc.Moreover,the influence of membrane chemical compositions,interior microstructures,and surface characteristics on the separation performance of NF/RO membranes,are comprehensively discussed.Subsequently,the applications of NF/RO membranes in biomedical separation field are systematically reported.Finally,the perspective for future challenges of NF/RO membrane separation techniques in this field is discussed.

Development and Extension of Seawater Desalination by Reverse Osmosis

Seawater desalination has been peoples fond dream since ancient times, the dream is now becoming a reality. This paper presents a brief development history of reverse osmosis. Much attention was paid to innovative development in membranes, modules, equipments and applied technology, including asymmetric and composite membranes, spiral-wound element and hollow fiber module, energy recovery equipments and different technological processes. The extension of reverse osmosis, such as desalination, pre-concentration, integrated processes and nanofiltration, is also briefly mentioned.

A Pilot-scale Demonstration of Reverse Osmosis Unit for Treatment of Coal-bed Methane Co-produced Water and Its Modeling

This study presents the first demonstration project in China for treatment of coal-bed methane(CBM) co-produced water and recycling.The work aims to provide a research and innovation base for solving the pollution problem of CBM extraction water.The reverse osmosis(RO) unit is applied to the treatment of CBM co-produced water.The results indicate that system operation is stable,the removal efficiency of the total dissolved solids(TDS) is as high as 97.98%,and Fe,Mn,and F-are almost completely removed.There is no suspended solids(SS) detected in the treated water.Furthermore,a model for the RO membrane separation process is developed to describe the quantitative relationship between key physical quantities-membrane length,flow velocity,salt concentration,driving pressure and water recovery rate,and the water recovery restriction equation based on mass balance is developed.This model provides a theoretical support for the RO system design and optimization.The TDS in the CBM co-produced water are removed to meet the "drinking water standards" and "groundwater quality standards" of China and can be used as drinking water,irrigation water,and livestock watering.In addition,the cost for treatment of CBM co-produced water is assessed,and the RO technology is an efficient and cost-effective treatment method to remove pollutants.

A Pilot-scale Study on Coal Gasification Wastewater Reclamation Using Pretreatment Alternatives Combined with Ultrafiltration and Reverse Osmosis

Aims to investigate the performance of the pilot-scale reclamation plant for coal gasification wastewater( CGW) using ultrafiltration and reverse osmosis with appropriate pretreatment alternatives,different pre-treatment alternatives- coagulation,adsorption,and ozonation methods were employed to treat the secondary effluent of coal gasification wastewater( SECGW) in a pilot-scale pressurized membrane system. The performance was compared to choose the most suitable pre-treatment alternative for the SECGW reclamation.Ozone reaction achieved highest COD removal efficiency( 79.6%- 91.0%),resulting in the stable normalized parameters of the subsequent ultrafiltration and reverse osmoses. In contrast,the coagulation and adsorption processes achieved only 32. 8%- 45. 7% and 53. 1%- 64. 6% decreases in COD,respectively. The residual organic pollutants in the reverse osmosis feed water led to an increase in normalized pressure drop and a decrease in normalized permeability( or membrane transference coefficient). The hydrophobic fraction was the main constituent( approx. 70% of DOC) in pretreated SECGW, and the hydrophobic-neutral fraction contributed mostly to the UV absorbance( 53%). Fluorescence excitation emission matrices revealed that ozonation removed most of the hydrophobic and aromatic proteins such as tyrosine and tryptophan which dominated in raw wastewater. The recalcitrant compounds such as phenolic compounds, heterocyclic compounds,especially long-chain hydrocarbons,which were easily attached to the membrane surface and contributed to organic fouling,could be oxidized and mineralized by ozone. Among the three pretreatments,ozonation showed highest removal efficiencies of hydrophobic and aromatic proteins,therefore resulting in highest normalized permeability.

STUDIES ON REVERSE OSMOSIS SEPARATION OF AQUEOUS ORGANIC SOLUTIONS BY PAA/PSF COMPOSITE MEMBRANE

The reverse osmosis (RO) separation of aqueous organic solutions, such as alcohols, amines, aldehydes, acids, ketones, and esters etc., by PAA (polyacrylic acid)/PSF (polysulfone) composite membrane has been studied. It was found that the separation results for aliphatic alcohols, amines and aldehydes are satisfactory, the solute rejection (R-a) and the volume fluxes of solutions (J(V)) for 1000 ppm ethanol, ethylamine and ethyl aldehyde are 66.2%, 61.0%, 84.0% and 0.90 x 10(-6), 0.35 x 10(-6), 0.40 X 10(-6) m(3)/m(2) . s, respectively, at 5.0 MPa and 30 degrees C. R-a increased with increasing molecular weights of alcohols, amines and aldehydes, and the R-a for n-amyl alcohol, n-butylamine and n-butyl aldehyde reached 94.3%, 88.6% and 96.0%, respectively. Satisfactory separation results (R-a > 70%) for ketones, esters, phenols and polyols have been obtained with the PAA/PSF composite membrane. The effect of operating pressure on the properties of reverse osmosis has also been investigated. Analysis of experimental data with Spiegler-Kedem's transport model has been carried out and the membrane constants such as reflection coefficient sigma, solute and hydraulic permeabilities omega and L-p for several organic solutes have been obtained.

Economic and Technical Analysis of a Reverse-Osmosis Water Desalination Plant Using DEEP-3.2 Software

Reverse osmosis （RO） is proved to be the most reliable, cost effective, and energy efficient in producing fresh water compared to other desalination technologies. It is the fastest-growing desalination technology with a greater number of installations around the world. The economic and technical performance of a medium-capacity RO desalination plant （2,000 m^3/day） proposed to be installed in Umm Qasr city south of Basra, Iraq is analyzed using DEEP-3.2 software created by the International Atomic Energy Agency （IAEA）. This port city is located on the Gulf shore and does not have any fresh water resources. The analysis shows that the cost of fresh water produced by this plant is US$0.986/m^3 with a good quality of fresh water （279 ppm）, which is a reasonable price for this remote area. The analysis also shows an increase in water production cost of about 12% at increased electricity price from 0.06 to 0.1 US$/kWh, 53% when the seawater salinity increased from 35,000 to 45,000 ppm, 2.5% when the seawater temperature decreased from 33 ℃ to 20 ℃, and 0.71% when the interest rate increased from 0% to 5%. Pumping fresh water from the Basra purification plant （located 175 km north of Umm Qasr） is 22.16 times the cost and 236.7% poorer quality than the fresh water produced by the RO plant.

Deep Learning Based Model Predictive Control for a Reverse Osmosis Desalination Plant

Reverse Osmosis (RO) desalination plants are highly nonlinear multi-input-multioutput systems that are affected by uncertainties, constraints and some physical phenomena such as membrane fouling that are mathematically difficult to describe. Such systems require effective control strategies that take these effects into account. Such a control strategy is the nonlinear model predictive (NMPC) controller. However, an NMPC depends very much on the accuracy of the internal model used for prediction in order to maintain feasible operating conditions of the RO desalination plant. Recurrent Neural Networks (RNNs), especially the Long-Short-Term Memory (LSTM) can capture complex nonlinear dynamic behavior and provide long-range predictions even in the presence of disturbances. Therefore, in this paper an NMPC for a RO desalination plant that utilizes an LSTM as the predictive model will be presented. It will be tested to maintain a given permeate flow rate and keep the permeate concentration under a certain limit by manipulating the feed pressure. Results show a good performance of the system.

Highly permeable reverse osmosis membranes incorporated with hydrophilic polymers of intrinsic microporosity via interfacial polymerization

Enhancing the water permeation while maintaining high salt rejection of existing reverse osmosis(RO)membranes remains a considerable challenge.Herein,we proposed to introduce polymer of intrinsic microporosity,PIM-1,into the selective layer of reverse osmosis membranes to break the trade-off effect between permeability and selectivity.A water-soluble a-LPIM-1 of low-molecular-weight and hydroxyl terminals was synthesized.These designed characteristics endowed it with high solubility and reactivity.Then it was mixed with m-phenylenediamine and together served as aqueous monomer to react with organic monomer of trimesoyl chloride via interfacial polymerization.The characterization results exhibited that more“nodule”rather than“leaf”structure formed on RO membrane surface,which indicated that the introduction of the high free-volume of a-LPIM-1 with three dimensional twisted and folded structure into the selective layer effectively caused the frustrated packing between polymer chains.In virtue of this effect,even with reduced surface roughness and unchanged layer thickness,the water permeability of prepared reverse osmosis membranes increased 2.1 times to 62.8 L·m^(-2)·h^(-1) with acceptable Na Cl rejection of 97.6%.This attempt developed a new strategy to break the trade-off effect faced by traditional polyamide reverse osmosis membranes.

Simulations of Tapered Channel in Multilayer Graphene as Reverse Osmosis Membrane for Desalination

Pressure-driven reverse osmosis membrane has important application in seawater desalination.Inspired by the structure of aquaporin,we established and studied the mechanism of the structure of multilayer graphene with tapered channels as reverse osmosis.The water flux of multilayer graphene with tapered channels was about 20%higher than that of parallel graphene channel.The flow resistance model was established,and the relationship between flow resistance and opening angles was clarified.The relationship between flow resistance and outlet size was also described.By means of molecular dynamics simulation,slip coefficients of multilayer graphene with tapered channel were obtained and verified by the contact angle of water.Results show that the permeability of graphene with tapered channel is about three orders of magnitude higher than that of commercial reverse osmosis membrane and the desalination rate is 100%.Temperature difference between the two sides of the tapered channel will promote the water flux positively.

One-Step Reverse Osmosis Based on Riverbank Filtration for Future Drinking Water Purification

The presence of newly emerging pollutants in the aquatic environment poses great challenges for drink-ing water treatment plants.Due to their low concentrations and unknown characteristics,emerging pol-lutants cannot be efficiently removed by conventional water treatment processes,making technically,economically,and environmentally friendly water purification technologies increasingly important.This article introduces a one-step reverse osmosis(OSRO)concept consisting of riverbank filtration(RBF)and reverse osmosis(RO)for drinking water treatment.The OSRO concept combines the relatively low-cost natural pretreatment of river water with an advanced engineered purification system.RBF pro-vides a continuous natural source of water with stable water quality and a robust barrier for contami-nants.With the pre-removal of particles,organic matter,organic micro-pollutants(OMPs),and microbes,RBF becomes an ideal source for a purification system based on RO membranes,in comparison with the direct intake of surface water.OSRO treatment removes almost 99.9%of the particles,pathogens,viruses,and OMPs,as well as the vast majority of nutrients,and thus meets the requirements for the chlorine-free delivery of drinking water with high biostability.The OSRO treatment is cost effective com-pared with the standard conventional series of purification steps involving sprinkling filters,softening,and activated carbon.Artificial bank filtration(ABF),which functions as an artificial recharge in combi-nation with a sand filtration system,is proposed as an alternative for RBF in the OSRO concept to supply drinking water from locally available resources.It is also suggested that the OSRO concept be imple-mented with wind power as an alternative energy source in order to be more sustainable and renewable.An OSRO-based decentralized water system is proposed for water reclaiming and reuse.It is suggested that future water treatment focus on the combination of natural and engineered systems to provide drinking water through technically efficient,financially feasible,resource reusable,and environmentally relevant means.

An Air Operated Domestic Brackish Water Reverse Osmosis Plant: Economically Sustainable Solution for Safe Drinking Water Supply for Chronic Kidney Disease of Unknown Etiology Affected Areas in Sri Lanka

Chronic Kidney Disease with unknown etiology (CKDu) is one of the crucial health issues in North Central, Uva, North Western, North, Central, and Eastern Provinces of Sri Lanka and incapacitates the kidney function. The main source for the CKDu has not yet been identified, though many scientists believed that the number of certain drinking water quality parameters is changed due to the contamination of water sources by agricultural activities. Hence, the government of Sri Lanka introduces electrically driven Brackish Water Reverse Osmosis (BWRO) plants with a capacity of 10 tones/day to supply safe drinking water for the impacted community though it is an energy-intensive process. Concurrently, a smaller version of an electrically driven BWRO plant was introduced to the rural farming community for their domestic use. However, it was not practically worked out due to various reasons such as high cost, unavailability of electrical power supply for those villages. In this study, an economical air operated domestic use BWRO plant with zero-emission was designed. This anticipated system significantly reduces the government expenditures to subsidize the water purification cost by 50% of the existing expenses. Besides, simple payback time was found to be 2.5 years, and the benefit-cost ratio to be more than 1. Evaluating the performance with the conventional values, it comprehends with more sustainable and economically viable system compared to the existing method of water purification.