Search

A pilot-scale reverse osmosis (RO) followed behind a membrane bioreactor (MBR) was developed for the desalination to reuse wastewater in a PVC production site. The solution-diffusion-film model (SDFM) based on the solution-diffusion model (SDM) and the film theory was proposed to describe rejections of electrolyte mixtures in the MBR effluent which consists of dominant ions (Na+ and Cl-) and several trace ions (Ca2+, Mg2+, K+ and SO42-). The universal global optimisation method was used to estimate the ion permeability coefficients (B) and mass transfer coefficients (K) in SDFM. Then, the membrane performance was evaluated based on the estimated parameters which demonstrated that the theoretical simulations were in line with the experimental results for the dominant ions. Moreover, an energy analysis model with the consideration of limitation imposed by the thermodynamic restriction was proposed to analyse the specific energy consumption of the pilot-scale RO system in various scenarios.

The current status of small-scale desalination (produced water capacity 100 m3/day or less) is reviewed to provide an overview of the market segment. The use of energy-recovery devices in this market segment is also reviewed. We find that the Middle East accounts for the largest market share worldwide at present, and reverse osmosis is overwhelmingly dominant among the desalination technologies adopted. Implementation of energy-recovery devices at small scale is rare, which leads to relatively high energy consumption for small-scale seawater reverse osmosis desalination systems.

The forward osmosis (FO) and reverse osmosis (RO) hybrid process uses seawater and wastewater treatment plant effluent as the FO draw solution and feed water, respectively, and the diluted seawater by FO is used as the RO feed water resulting in the less energy consumption than the conventional seawater reverse osmosis applications. This work developed an optimal design approach of the hybrid process by finding the optimal RO recovery and FO permeate flow rate. The optimized RO recovery (e.g. 38.5–66.7% according to the FO permeate flow rate) determined by solving an optimization problem based on the mass balance in the FO-RO hybrid process, minimizes the RO energy consumption (1.86–3.49 kWh/m3 at 25°C and 2.41–3.86 kWh/m3 at 5°C). The RO energy consumption decreases as the RO recovery increases until it reaches an optimal value. The optimal FO permeate flow rate can be defined with three different perspectives: (1) to minimize the RO energy consumption, (2) to minimize the RO feed flow rate, and ...

This paper presents a performance evaluation and economic analysis of a reverse osmosis (RO) and pressure retarded osmosis (PRO) hybrid process to propose guidelines for its economic competitiveness use in the field. A model to predict the performance of a hybrid process using RO and PRO was developed based on a solution-diffusion model modified with film theory. The effects of external and internal concentration polarization (ICP) on PRO efficiency were considered in the model. Moreover, a simple cost model was applied to analyze the effects of seawater TDS and feedwater for the PRO process, water and salt permeability of PRO membrane, and membrane and energy cost on the RO-PRO hybrid process. The results show that the water transport coefficient, ICP, and seawater and feedwater TDS are important factors affecting the performance of the PRO process. On the other hand, the effect of the salt transport coefficient is not substantial. The RO-PRO hybrid process can be economically competitive with th...

Nowadays, the most important problems that affect the world are carbon footprint decrease, fossil fuel use, and climate change. As proof of that, all environmental international agencies impose different laws and rules related to greenhouse effect. European Union policy is a clear example, which is explained in the document “2020 Strategies (COM/2010/2020 final)” [1]. Water deficit is another question that produces a lot of problems around the World. About 1,100 million people lack access to safe drinking water, which represents 18% of the world population. Approximately 42% of the population is not able to access basic sanitation. The project raised different problems related to water and energy production. The primary goal is to achieve low carbon emissions. Moreover, these dual plants (desalination and thermal power plants) should be more efficient and flexible. The project’s main goal is to study water and energy cogeneration in half power thermal power plants through different docking ways. T...

The frontier of water treatment technologies is being defined by hybrid processes and thoughtful design integration within treatment trains. The use of increasingly sophisticated process trains is driven by the need to treat dramatically impaired water supplies while maintaining low cost, high utilization, and high operational flexibility. Integrating forward osmosis (FO) technology is one notable, emerging opportunity to realize substantial advantages in cost and performance compared to the use of either conventional membrane processes or thermal technologies. Reverse osmosis technology remains ideally suited to desalinate low fouling streams to moderate levels of recovery. Spray dryers or crystallizers employing mechanical or thermal vapor compression cycles are still best used to convert saturated or organic rich liquors to solid products. But what of the multitude of waters, especially industrial streams, that are too saline or high in foulants to be well treated by reverse osmosis and are not...

Reverse osmosis (RO) membranes have been widely applied to seawater desalination and wastewater reclamation, and many large RO plants (>100,000 m3/d) have been constructed since 2000. Energy efficiency is indispensable for large plants, especially for future mega-ton scale seawater reverse osmosis (SWRO) plant (1,000,000 m3/d). In order to reduce energy demand in RO operation, high-efficient low-pressure RO membrane, energy recovery device (ERD), and pressure-retarded osmosis (PRO) which would recover power from salinity gradient between freshwater and concentrated brine were studied in the “Mega-ton Water System” project. A PRO hollow fiber membrane module was newly developed, and a practical continuous operation has been examined at a prototype plant for one year. The maximum 13.5 W/m2 of membrane power density using 10-inch module was established at our prototype PRO plant. As the results of the plant cost estimation and the financial impacts on the energy saving operation at the mega-ton scale...

Due to increasing industrial and human water consumption, as well as increasing water and wastewater disposal costs, recycling of industrial wastewater is of growing importance. The textile wet processing industry discharges a significant volume of wastewater with considerable organic contamination and residuals. In Yunus Textile Mills (YTM) in Pakistan, we successfully recycled textile wastewater using a membrane bioreactor (ultrafiltration) followed by reverse osmosis (RO). This textile wastewater recycling plant is the first of its kind in Pakistan and is an important benchmark for all future developments in textile wastewater treatment (WWT). In YTM, wastewater was treated with a series of environmentally friendly processes including heat recovery from hot wastewater using a custom-designed heat exchanger with an operating efficiency of 65.9% and reducing the wastewater temperature from 70 to 43°C. Neutralization of wastewater was achieved by mixing power plant exhaust emissions, thereby reduc...

Groundwater desalination could be a possible solution to Egypt’s water scarcity problem through applying state-of-the-art desalination technologies. This work investigated a recently developed sustainable desalination technology which is fertilizer drawn forward osmosis (FDFO). In this work, ammonium sulfate was selected as a draw solution being a commercial, inexpensive, and efficient Egyptian fertilizer. Three commercially available Forward Osmosis (FO) membranes were tested for baseline flux. The best membrane was selected for further experimentation. A real Egyptian brackish groundwater sample from El Tor in Sinai was used as the feed solution. Performance has been assessed by the water flux, reverse permeation, and the forward rejection of the feed solutes. Porifera’s commercial FO membrane proved to be the best membrane with respect to baseline flux. It was chosen for further experimentation. Water flux and ammonium sulfate concentration can be correlated logarithmically. Further increase in...

Water resources in North Africa are limited and do not meet the future water demand. The water shortage is very severe in Libya which is located in a semi-desert region. The available water resources in Libya are mainly the groundwater which is not enough to meet its people needs due to many reasons, among them is seawater intrusion. Desalination of seawater is one of the main alternatives for the substitution of water shortage in Libya and other North African countries. Despite the fact that desalination technology is an important option for providing potable/industrial water, it has some negative impacts on environment. High concentrated brine discharges from desalination plant is the main cause of negative impacts. Noise, visual impact, air pollution, impact on the aquifer, and disturbance of recreation areas are other environmental impacts on a more local scale. The aim of this study was to highlight the environmental impacts of Tajoura reverse osmosis desalination plant on the local environme...

Water resources available in the island of Fuerteventura come mostly from small-scale capacity seawater desalination plants. Desalted water demand in the island has grown considerably in the last decade forcing managers to adapt desalinated water supply constantly. Additionally, the operating cost of the plants is relevant. The staff, chemical consumption, cartridge filter, and membrane replacement cost are essential in order to establish more efficient operation conditions of a reverse osmosis desalination plant. This article aims to study and compare the mentioned cost of six different seawater reverse osmosis desalination plants with the same production of 600 m3/d in the island of Fuerteventura. The results show for each of the six cases how costs can be reduced and the essential role of automation dealing with the staff cost with the particular capacity of 600 m3/d.

Forward osmosis has found numerous applications in water treatment, water reuse, and other sectors e.g. desalination, concentration of wastewater, landfill leachate treatment, controlled drug release, emergency water treatment kit, etc. because of its low pressure operation and low fouling. The present paper demonstrates that the fertilizers can function as draw solution and be employed for drawing water from the brackish water. The proposed process eliminates the recovery step and the diluted draw solution can directly be utilized in fields for fertigation. We have selected fertilizers as a draw solution which provides nutrients to the crops for their basic growth. The domestic reverse osmosis membrane element has been converted to forward osmosis membrane element in a novel approach. The performance of each fertilizer is accounted in terms of experimentally obtained flux by comparing it with theoretically estimated flux. It has been found that there is a significant difference in experimentally ...

With increasing water demand and growing scarcity of potable water, the reuse of water recovered from low salinity water like sewage or surface water is becoming an important issue from both technical and economic points of view. The reverse osmosis (RO) membrane processes widely used for water recovery inevitably produce RO concentrate having very high concentrations of salts and other materials of concern. Disposal to nature or feeding back into the recovery facility can be an option, but may have an impact on environment and raise legal problems. This study deals with the biological treatment of RO concentrate produced during water reclamation processes. The RO concentrate studied had low BOD5 and T-P, but high T-N and COD concentrations. The sequencing batch reactor (SBR) process and the modified Ludzack-Ettinger (MLE) process were compared in controlled lab-scale experiments. The pilot-scale plant was operated to evaluate the performance of the SBR process under more realistic conditions. Kin...

Our earth is a water planet; nearly two thirds of the earth’s surface is covered by ocean water. But the shortage of fresh water is a major problem in many areas, especially in rural villages near to the sea or islands. Now, renewable energy-based desalination system is rising around the world due to the adverse environmental effect and high-energy requirements of the conventional fuel-based desalination system. This paper describes the prospect of an off-grid stand-alone wave-powered reverse osmosis desalination system for those areas. A simulation model for the prediction of the wave power delivered for a given value of the wave height and period is adopted. Based on the availability of the wave data, the amount of the water produced at different sites of Malaysia can be calculated in this paper. In addition, this paper deals with an economical analysis of wave energy production for reverse osmosis desalination system.

The purpose of this paper was to develop and present a process suitable for the purification of the so-called produced waters, a by-product of crude oil extraction, by devising a treatment train aimed at industrial and agricultural water reuse. If compared to municipal wastewaters, produced waters have a very high salinity that requires specific attention for designing and managing the specific treatment device. Membranes, commonly used in the production of desalted water, appear to be a suitable technique to deal with these issues. In this paper, we propose a comprehensive process scheme for produced water treatment train: A Vibratory Shear Enhanced Processing (VSEP) membrane system is in charge of the secondary treatment, whereas a reverse osmosis (RO) unit realizes the tertiary treatment. Material and energy balances are carried out on the whole process, while the RO process is simulated by the IMSDesign Software by Hydranautics. We analyzed three different scenarios, at increasing produced wat...

Forward osmosis (FO) is a natural process, occurring in the cells of all living things when liquids of differing solute concentrations are separated by a semipermeable membrane at ambient temperatures. FO differs from reverse osmosis (RO) in that natural osmotic pressure, resulting from the difference in solute concentration in the two liquids, is the sole driving force for the transport of water across a membrane. The purpose of this paper is to illustrate the energy/cost of water trade-offs when comparing RO and FO technology for water purification. Trials of the FO system were conducted by a third party consulting firm, Carollo Engineers and the US Navy to monitor energy consumption, with results demonstrating the feasibility of operating an FO plant at one-sixth the electrical energy of current RO systems, i.e. 0.8 kilowatt hours per cubic meter of water. The FO process uses “waste” or low-grade thermal heat to drive the systems energy requirements of

Despite the fact that desalination is an important technology for providing desalted water, it has some disadvantages that have not been taken seriously into consideration. Such technology can have undesirable effect on the environment. Environmental related impact could occur from the early days of plant construction and, subsequently, when the plant is in operation. Tajoura reverse osmosis desalination plant is the largest desalination plant of its kind in Libya. It has been under operation for nearly three decades without serious consideration of its impact on the environment. This paper is the first attempt in that direction. The main objective of this study is to measure the chemical components of brine concentrate discharged from Tajoura plant, and to highlight their impact on the environment. This study was conducted in the Water Desalination Department in Tajoura Nuclear Research Center. Samples were collected from feed source (seawater), and from reject stream (brine discharge point). Sam...

A modified reverse osmosis (RO) system with zero wastewater was developed, and its performance was tested against allowable limits of total dissolved solids (TDS) in Jordan. New components were added to the typical single- and double-membrane RO systems used in private homes to re-direct the amount of saline water rejects to drainage. Instead, this water is mixed with input water from the source. Then, the mixed water is used for domestic household purposes other than drinking. The TDS values of output fresh water and mixed water were tested and found to be within safe limits. The new components can be fitted to existing systems with a small amount of extra space. The reuse of saline water after mixing does not require human interaction, and the system can be fully utilized for safe and continuous operation. The newly modified system produced huge water savings relative to existing systems. The implementation of modified RO plants could save a country like Jordan, 18 million cubic meters of supplied input water annually, based on 500,000 RO units operating in Jordanian homes, with 100% water recovery.

Forward osmosis (FO) has emerged as a method for desalting saline water and power production. It utilizes a chemical potential difference, or a salinity gradient to permeate fresh water through membranes. This paper investigates the feasibility of using the FO process for seawater (SW) desalination in terms of consumed energy, capital costs, water recovery, operation & maintenance, water quality, and the final product water cost. The study covers FO by itself, and when combines with other desalting systems such as reverse osmosis, multi stage flash (MSF), and multi effect distillation as pretreatment method. This paper reviews first the principles of fluid and solutes flow in the FO membranes, concentration polarization, the difference between the FO, pressure retarded osmosis processes, draw solutions, and the solutes involved in these draw solutions. Then, the main characteristics of the FO membranes and their commercial availability are presented. Previous experimental work and a commercial plant using FO for desalination are also given. The use of FO as pretreatment for other desalting methods is presented in light of two proposed research projects. The first research project proposes utilizing FO as pretreatment for processing treated wastewater and SW in one system. The second project utilizes FO as pretreatment for a once-through MSF desalting method. The analysis proved energy reduction in the energy consumption of both desalting systems by more than 50 and 18%, respectively.

Seawater reverse osmosis (SWRO) is the most cost-effective, practical, and widely used desalting system. Its energy consumption, for Arabian Gulf seawater conditions is in the range of 5–6 kWh/m3. These are less than 1/3 of the equivalent mechanical energy of the thermal desalination systems presently used in Qatar. Besides, these thermal systems consume 2–4 kWh/m3 for pumping. Therefore, using SWRO system in Qatar can save up to 75% of the desalination energy cost. For Qatar, current desalting water production using thermal methods is 480 Mm3/year at $0.1–1.2/kWh energy price; the energy cost is at least one Billion US dollars per annum. A SWRO pilot plant is to be built in Qatar prior to building a full size desalting plant (DP) in order to determine site-specific treatment guidelines and to provide a full range of performance information to be used in the design of a full-scale plant. The pilot plant will be tested when the feedwater quality is good, and when there are major storm events or alg...

Desalination of seawater can provide an almost inexhaustible source of freshwater if it can be made affordable. This work is part of an innovative approach aimed at improving the seawater desalination cost through the development of a new method which is more efficient than the existing processes in use. A benchmarking study and a literature analysis were realized, and the results helped us in orientating research study toward the development of an industrial hybrid system coupling freezing and reverse osmosis (RO). The freezing process is proposed as a method of seawater pre-treatment for the RO membranes. It is coupled with a heat pump system which freezes the seawater inside a crystallizer and melts the ice in a melting chamber. By combining freezing and membrane desalination processes, the hybrid system has been successfully improved. The evaluation of the proposed systems’ energy consumption shows energy savings of approximately 25%, and an improvement of the quality of osmotic water for abou...

The selection of a proper pretreatment for reverse osmosis (RO) systems is essential to produce a high-quality feed water in order to ensure a more sustainable and reliable operation. Traditionally, seawater RO installations have been operated with conventional pretreatments based on single- or two-staged media filtration, and occasionally preceded by coagulation/flocculation processes. In recent years, however, hollow fiber ultrafiltration (UF) technology has increasingly gained acceptance as a viable pretreatment alternative for seawater desalination, due to advantages such as greater capability to cope with fluctuations and high solid loads in raw waters (typical of open intakes), smaller footprint, higher and more consistent filtrate water quality, and higher environmental sustainability, ultimately demonstrating lower total water cost in the long-term operation. In this article, design and operational aspects of the country’s largest integrated UF and RO system to treat seawater in a remote i...

The cost of desalinated water is likely one of the most relevant indicators to characterize and compare the desalination methods with other technical options to supply water for urban, industrial and agricultural purposes. Obviously, costs of producing desalinated water vary from facility to facility due to factors such as location, facility design, plant size and available technology. This work reports on the technical and economical comparison of reverse osmosis (RO) and nanofiltration (NF) in the desalination of the underground brackish water of Moroccan Region. The capital and operating costs for both processes are determined on the basis of a real industrial and economical data. The study was carried out for a production capacity of 3,000 m3/d corresponding to water consumption for 30,000 capita following the Moroccan considerations (consumption for domestic use of 100 l/per capita per day). Technically and economically, the work shows that in this case, the NF process appears more convenient...

Desalination of brackish groundwater has emerged as a major option to overcome water scarcity, since quantity and quality of surface water is not appropriate for the continuously growing water demand of two-thirds of the world’s population. Photovoltaic (PV) solar energy powered reverse osmosis (RO) system can be the best option in secluded and isolated areas of the world that are suffering from a shortage of electricity energy and drinking water. This technique is likely to be the lowest energy demanding technology among other desalination techniques. Further, adopting measures like energy recovery devices, hybrid pretreatment process, and battery-less system reduces overall cost of the system. But, the capital cost of the system is still too high to support this technology competitively in the market. In the present paper, a review of the PV-RO systems employed for drinking water treatment in non-electrified rural areas of developing countries has been provided. The status of development in the last few...

Sea water reverse osmosis (SWRO) desalination constitutes a successful technology for covering local fresh water supply shortage in many areas of the world and especially in isolated areas such as islands and coastal regions. SWRO units can be combined with renewable energy (RE) technologies such as photovoltaic and wind generators. Small-scale SWRO units combined with energy recovery devices can decrease drastically the energy consumption of the SWRO units. Furthermore, it is proven that the operation of a desalination unit in part-load conditions can result in lower specific energy consumption compared to continuous full-load operation. This paper presents an experimental comparison between two small-scale SWRO units equipped with different energy recovery devices in order to lower the specific energy consumption. The first SWRO unit consists of a hydraulic energy recovery device of the Clark pump type which plays also the role of the high-pressure pump in a conventional reverse osmosis unit. Th...

The desalination market based on reverse osmosis is a growing market thanks to much lower energy consumption compared to thermal desalination. This leading position implies that a lot of efforts should be done to improve both its acceptability and cost to thwart its detractors. For those reasons, the further improvement of the energy consumption is a key factor and one of the main objectives of the desalination community. It is well known that temperature has an impact on membranes’ feed pressure. For equivalent feed water quality and operational conditions, high temperature water will require less pressure to produce the same amount of permeate. Based on this reality, some projects are considering the opportunity to recover cooling waters from cooling towers or MSF/MED cooling system as seawater feed to RO plants to reduce electrical consumption, in particular on hybrid, IWPP, or co-location projects. But temperature has also an adverse effect on the permeate water quality that could result in in...

Many remote communities lack access to a reliable water supply. They often have access to brackish groundwater or seawater, making reverse osmosis desalination a possible solution. However, reverse osmosis desalination is an energy-intensive process and many remote communities are off the electrical grid. Determining the most economic reverse osmosis system configuration and electrical power source for a given remote community is a challenge due to their unique resource availabilities. This paper presents an optimization-based approach to compare the economics of different small-scale reverse osmosis systems and power sources for remote communities. In this approach, physical models describe the performance of electrical power systems composed of photovoltaics, wind turbines, diesel generators, batteries, and hybrid systems. These power system models are coupled to a reverse osmosis system model to determine the water production. An optimization is performed to determine the most economic power sy...

Solar-powered reverse osmosis desalination (Photovoltaic-powered reverse osmosis [PVRO]) is a technically feasible method of providing fresh water to many remote communities with saline water sources. To be practical, these systems must be well operated and maintained by non-experts. Their productivity is a complex function of their locations, water chemistry and demand, and the solar radiation history at their locations, which is quite variable with time. A key aspect of the maintenance program is the cleaning of the reverse osmosis (RO) membranes, including system flushing and chemical cleaning. Guidelines for cleaning from membrane manufacturers do not consider the complex, variable operating conditions for these small solar-powered systems. Local operators do not have the expertise to determine how and when cleaning should be done. While cleaning will generally improve clean water production, it is costly, requires the system to be shut down, and uses some of the clean water produced. Here, si...

A major drawback of Reverse Osmosis (RO) desalination units is their poor performance at off-design conditions. On the other hand, they can operate with low specific energy consumption and produce high-quality fresh water when they are supplied with almost constant power, according to their design and nominal operating conditions. This aspect brings additional effort when there is the need to desalinate seawater or even brackish water using unsteady power sources, such as renewable energy systems powered by, for example, solar or wind energy. In order to overcome this issue, an alternative small-scale RO unit is investigated here, whose major advantage is that it can operate with almost constant specific energy consumption and produce high-quality fresh water with low Total Dissolved Solids (TDS) for a wide range of power input. Such unit is suitable to be combined with small-scale energy systems, which can have a very high variety on their power output, such as PV, wind turbines, or even solar Or...

This paper proposes a simple design method of the RO system in RO brackish water desalination plants. This method is based on the application of maximum available recovery without scaling of any of the compounds present in the water as silica, calcium carbonate, calcium sulfate, barium sulfate, strontium sulfate, and calcium fluoride, and membrane manufacturer design guidelines, and the plant production. It is a continuation of the paper “A design method of the RO system in reverse osmosis brackish water desalination plants (procedure)” presented at the conference on Membranes in Drinking and Industrial Water Production, Leeuwarden, The Netherlands, 10–12 September 2012. Although the method was originally conceived for application to subterranean brackish waters in the Canary Islands, Spain (principally Gran Canaria, Fuerteventura and Tenerife), it can be extrapolated to other types of region and water treatable with RO systems. The required input data are the chemical composition of the feed wate...

Sea water reverse osmosis (SWRO) desalination constitutes a successful technology for covering the potable water needs of islands and coastal regions. SWRO units can be combined with renewable energy technologies such as photovoltaic and wind generators. Conventional small scale SWRO units are not often combined with energy recovery devices; however, these devices can decrease drastically the energy consumption of the SWRO units. Furthermore, in the literature there are references which prove that the operation of a desalination unit in part-load conditions can result in lower specific energy consumption compared to full-load operation. This paper presents the simulation and the experimental investigation under full- and part-load conditions of an existing SWRO desalination unit (50 mS/cm feed water) in order for the desalination unit to be optimally utilized in a polygeneration microgrid topology which uses advanced energy management algorithms. The experimental operation of the SWRO Unit in part...

Water reuse is receiving increasing attention worldwide as a means of sustainable water management. The Sulaibiya Wastewater Treatment and Reclamation Plant in Kuwait was established with a design capacity of 425,000 m3/d to be the world’s largest membrane-based water reclamation facility. These plants use ultrafiltration (UF) and reverse osmosis (RO) for reclamation of secondary-treated wastewater. Statistical analysis of plant data during 2012 revealed that the UF/RO was capable of producing effluents that satisfy water quality requirements for various reuse applications. It showed high stability and minimal response to seasonal variations in water temperature and to about 13% increase in inflow over its design capacity. The plant achieved almost 99% removal of common pollutants along the treatment stages by removing traces of residual pollutants such as BOD, TSS, nitrogen, phosphorus, and coliforms in the reclamation stage. Also, RO lowered the total dissolved solids of plant effluent considera...

The economic evaluation of defluoridation of Sahara groundwater is presented for three processes: electrodialysis, reverse osmosis and the electrochemical bipolar reactor (EBR). The economic study was accomplished for a drinking water unit production of 100 m3/h. One of the findings was that the costs per cubic metre of treated water obtained with different processes were not too costly for the states of the North African region. The results also indicated that the most efficient process uses the EBR, followed by the electrodialysis and reverse osmosis process. However, the water produced by the first process does not have the required quality for drinking water; therefore, it has to be utilised for agricultural purposes. On the other hand, the electrodialysis unit do produce quality drinking water and appears to be an interesting solution to the fluorisis disease. Reverse osmosis method technique provides higher quality of drinking water with a salinity not exceeding 0.1 gsalts/l.

Osmotic backwash is a physical cleaning method based on water back flow from the permeate side to the feed side driven by osmotic pressure difference across reverse osmosis (RO) membrane. The concept of osmotic backwash was already introduced and verified in laboratory-scale experiments by a few previous studies. In this study, osmotic backwash observed in an RO pilot plant isdiscussed. The pilot plant was originally designed to demonstrate industrial water production with the capacity of 250 m3/d and the recovery rate of 95.5%. Osmotic backwash was observed accidentally when the plant was stopped, fixed, and re-operated by an unpredictable failure. Osmotic backwash started at the stop of RO operation when applied pressure was dropped below the osmotic pressure. An RO performance analysis with normalized parameters was used to quantify the effect of osmotic backwash. The reduction of fouling was quantified before and after osmotic backwash, but it was limited to remove all the foulants on the RO m...

The production of freshwater from seawater is a growing necessity throughout the world. In arid areas with high temperature and salinity seawater, thermal desalination and power plants (dual-purpose/cogeneration plants) are often employed for the production of power and water. In other areas, reverse osmosis is commonly employed. However, both technologies are inherently challenged with economic and performance issues. As a response to these issues, hybrid desalination, that is, employing both thermal and mechanical desalination methods, has been increasingly utilized over thermal desalination plants alone. In this article, an overview of thermal desalination, seawater reverse osmosis (SWRO), and co-generation of power and water is presented, specifically with regards to the motivation for utilizing hybrid plants, for example, process limitations and areas of potential improvement. In addition, a review of the considerations for design and economics of hybrid desalination plants is presented, for...

Water desalination is one of the most important factors that can help in developing remote areas and the desert. A critical technical parameter of desalination applications is the way the system is powered. This decision is taken according to the selected method of desalination and the characteristics of the candidate area. Nowadays, the method of reverse osmosis dominates globally; it requires only electricity, has a quite low specific energy demand, and can cooperate with technologies of renewable energy sources such as wind turbine and photovoltaics. Hence, renewable energy-powered reverse osmosis systems are promising technologies for brackish and seawater desalination in remote regions as they exhibit low energy consumption and can be designed according to water demand and energy resource. This study analyzes the feasibility of using wind energy to power brackish water reverse osmosis desalination units proposed for the development of the southern region of the case study country of Algeria. A revers...

This study proposes a simple design method of the Reverse osmosis (RO) system in RO brackish water desalination plants. This method is based on the application of maximum available recovery without scaling of any of the compounds present in the water as silica, calcium carbonate, calcium sulfate, barium sulfate, strontium sulfate, and calcium fluoride, and membrane manufacturer design guidelines, and the plant production. Although the method was originally conceived for application to subterranean brackish waters in the Canary Islands, Spain (principally Gran Canaria, Fuerteventura and Tenerife), it can be extrapolated to other types of region and water treatable with RO systems. The required input data are the chemical composition of the feed water, pH, temperature, silt density index membrane manufacturer design guidelines, and the plant production. The programmed method then determines the design of the RO system. The method whose procedure is described graphically and analytically can be used...

Providing clean water to small communities using renewable energy (RE) has long posed as a humanitarian challenge. Reverse osmosis (RO) desalination has been proven as a mature technology for supplying fresh water for different domestic, industrial, and agricultural usages. On the other hand, RE is the targeted future alternative that can drive RO desalination process in many parts of the world. A lot of work has been done on operating desalination processes using either wind or solar energy individually or both energy sources alongside one another. In this paper, a numerical model which would allow finding the optimal design of a hybrid solar-wind power that would drive a small-sized RO desalination plant is presented. The optimized design variables are the number of solar Photovoltaics modules, the number of wind turbines, height of the wind tower, radius of the rotor blade, and the desalination plant capacity. The objective is to obtain a design which would allow us to produce a given amount o...

This paper presents the results of research work conducted as part of a doctoral thesis and undertaken with the aim of resolving the problem of accelerated fouling of reverse osmosis membranes (made from spiral-wound polyamide), as a result of the deposition of colloidal particles (particulate fouling), the precipitation of inorganic salts (scaling) and the accumulation of living and/or dead biological matter (biofouling). The reverse osmosis modules affected form part of the Las Palmas III (LP3) desalination plant run by the company EMALSA (Spanish initials: Empresa Mixta de Aguas de Las Palmas). This plant is located on the island of Gran Canaria (Spain) and supplies potable water to around half a million people.

Closed Circuit Desalination (CCD™) technology is an emerging platform for reverse osmosis (RO) water treatment and desalination. It lowers the feed pressure requirement, improves the membrane performance, increases the operational flexibility, and eliminates the need for energy recovery devices using only standard RO equipment. For industrial water treatment and brackish water desalination applications, CCD technology achieves maximum recovery in single-stage units while saving energy. Alternately, a CCD unit can be added to a conventional RO process to concentrate brine and raise recovery. Over 97% recovery has been demonstrated in a single-stage operation. The recovery rate of a CCD unit can be adjusted at the control panel without modification of system hardware, limited only by the scaling characteristics of the feedwater. Maximum recovery operation and high flexibility have significant cost-cutting implications for industrial water treatment and inland brackish desalination, where both feedw...

To ensure correct operation of any facility that uses membrane treatment technology (ultrafiltration, reverse osmosis, etc.) requires a set of maintenance and cleaning operations, which allow correct operation and optimum duration of membranes, and also ensure the quality of water produced. In 2009, the existing drinking water treatment plant in Sant Joan Despi started operating a treatment combining ultrafiltration and reverse osmosis technologies to ensure compliance with the health limits set by the Spanish Royal Decree RD140/2003. Specific antiscalant was developed especially for controlling calcium carbonate, calcium phosphate, and barium sulfate scales, which are the most problematic insoluble species in the brine of the reverse osmosis at the water treatment plant in Sant Joan Despi. Specific software was developed to calculate the optimum dose of antiscalant based on the feedwater chemistry, the temperature, and the RO plant’s conversion, thus minimizing operating costs. Furthermore, Adic...

The boiler water in certain power plant is produced by chemical decarbonization, sand filtration, and ion exchange. Process ends with mixed bed ion exchange. The current boiler water treatment process is analyzed in terms of achieved water quality, quantity and quality of wastewater, and amount of chemicals needed. The main disadvantage of current process is consumption of large amount of chemicals. Ion exchange process could be replaced with the reverse osmosis, but pretreatment (decarbonization and filtration) should be retained. Since the permeate quality does not meet quality requirements, it would be advisable to use mixed bed ion exchange. If reverse osmosis is used, quantity of water that enters the treatment and wastewater would be for about 17.5 and 150% larger, respectively, but content of salt in wastewater would be about 20–30-fold less. Nevertheless, final decision on which technique to apply should be based on further economical considerations.

We introduce the present article with the intention to define the most efficient production line for reverse osmosis seawater desalination plants. We show the relationship between the cost of desalinated water per cubic meter according to the production capacity, verifying a scale economy as the production rises significantly. The destination of this article is within the reach of small desalination plants in the range between 500 and 15,000 m3/day in the Canary Islands Autonomous Community. Specified range is the most established in the Autonomous Community. Approximately, more than about the 90% of the desalination plants have a production capacity corresponding to the selected range. The methodology used consists of calculating each one of the costs involved in the seawater desalination process, applying actual prices, and obtaining a graphic serial according to prices tolerance, from −5% to a value of +5%. Concerning staff costs, we have recovered data from the iron and steel industrial secto...

Reverse osmosis is a widely used and rapidly growing desalination technology. Despite the many benefits the technology has to offer, still challenging to all desalination plants is the environmentally sensitive effects attributed to the discharge into the sea of the rejected brine, which can very often severely damage the receiving environment, and air pollutant emissions attributed to the energy demand of the process. The list of potential impacts can be extended; however, the available information on the marine discharges alone indicates the need for environmental mitigation measures. In order to safeguard a sustainable use of the desalination technology, there is a need to develop, in the short term, new management proposals to achieve a minimization of the impact and valorization of brine. These alternatives should be both economically viable and effective, not only for new setting up plants, but also for those already installed. An adequate treatment sequence has been proposed and developed ...

Reverse osmosis (RO) is a widely accepted and applied process for the purification of a variety of raw water sources, especially when there is a need for removing the bulk of the dissolved salts and other impurities present in the feed streams. Since its first applications and references, the technology has progressively been refined and improved, up to the current mature status, where, even if innovations are still to come, a solid base frame exists already. This paper will review and analyze long-term operation data from medium and large-size projects, including two different seawater desalination plants examples. It will focus on the long-term stable and reliable performances of DOW FILMTEC™ RO elements, by comparing the expected performance to the current operation data, with special emphasis on the long life of elements, and thus low replacement rates. These two installations are of particular interest given the time they have been successfully producing the required amount of drinking water...

Although reverse osmosis (RO) is a membrane seperation process which leads to the desalination market for both seawater and brackish water desalination, other newly developed membranes processes are emerging to be well applicable for the production of fresh water by desalination. The newly developed membrane processes such as membrane distillation (MD) and forward osmosis (FO) claim to have the potential to strongly be competitive to the commercial RO. MD and FO are now under development either on a pilot test unit’s scale or small-sized commercial units. This paper presents a technical review and assessment of MD, and addresses the latest development in MD configurations, membranes, integration with other processes and the process modeling

The development and exploitation of sustainable and environment-friendly energy resources are required in order to resolve global energy shortages. Recently, salinity gradient power (SGP) has been considered a feasible candidate, with high potential to become a substitute for the current use of fossil fuels due to benefits such as less periodicity, abundance and no emission of carbon dioxide. In this paper, one SGP, pressure-retarded osmosis (PRO) system, was reviewed in terms of its mechanism, limitations and available applications. In the PRO system, water permeates through a semipermeable membrane from the feed solution to the draw solution, and energy is generated by depressurizing the permeated flow through a hydro turbine. Models for understanding its mechanism and for improving of its performance were reviewed. In addition, applications of sea water reverse osmosis (SWRO), wastewater treatment (WWT) and PRO hybrid process were introduced in order to develop new water-energy nexus processes...

Energy consumption is a key factor which influences the freshwater production cost in reverse osmosis (RO) process. Energy recovery and reuse options have already been very well explored in the current desalination industry. Achieving minimum theoretical specific energy consumption for water recovery is not feasible due to effects of concentration polarization, membrane fouling and hydraulic resistance to permeate flow. Due to these limitations, energy recovery along with water recovery can be a better alternative to improve energy consumption and economics of the RO process both in small and large scale applications. This paper reviews currently available process configurations, operating strategies, and discusses potential pathways to recover and recycle energy and water to improve the performance of the RO process.

As the role of desalination in providing water is broadened, it has come under increasing scrutiny due to its perceived impact on the marine environment and its energy intensity. Desalination’s increasing popularity is due to lower cost technologies such as reverse osmosis along with the need to supply water to populations are moving towards the coast. Sustainable desalination is feasible when desalination projects are combined with demand management to ensure that the water is effectively used. There is appreciable scope to lower its energy demand through new technologies and approaches and by adopting desalination techniques wastewater can be recovered for potable and non potable use. Desalination can also play a positive role in relieving pressure on low flow rivers.

In recent years, there has been an increasing thrust towards zero-discharge operation of waste-water treatment plants. This has been driven by increasingly stringent discharge standards, as well as financial benefits stemming from the recycling of water around such facilities. The molasses-based fermentation industry is associated with high consumption of water and a high generation of high-strength effluent, due to the widespread use of molasses feeds. Traditional biological treatment for this effluent is incapable of meeting stringent discharge and reuse standards; therefore it must be supplemented with tertiary treatment options. The main options for water recovery are reverse osmosis (RO) membrane filtration and evaporation. The main problems for these treatment options is the high energy consumption associated with their use and the requirement for pre-treatment leading up to the RO stages. This paper will compare potential treatment options for high water recovery from the high-strength effluent gen...