Seawater Reverse Osmosis Plant Research Articles

Multi-criteria analysis for sustainable and cost-effective development of desalination plants in Chile

In Chile, there is an increasing demand for freshwater supply for human consumption, agriculture, and industrial activities. In this sense, the country is highly threatened by climate change, which is drastically affecting the availability of water resources in the north-central region due to desertification processes. Therefore, seawater reverse osmosis (SWRO) desalination is becoming one of the most feasible alternatives to address current and future challenges regarding water scarcity in the country. This investigation aims to evaluate potential locations for a sustainable and cost-effective installation of desalination projects; the latter, under a multi-criteria and geographic information system (GIS)-model. The model was tested in the highly water scarcity-threatened Valparaiso Region, Chile, as a case study. The model was developed integrating economic and socio-environmental criteria involved in the development and/or construction of desalination projects. The results of the multi-criteria analysis show that the Valparaıso Region presents optimal areas for developing SWRO projects. Both the northern and central areas of the Region show appropriate locations for installing SWRO plants and their freshwater distribution lines, ensuring short- and long-term water supply, especially for agriculture and population consumption. The results obtained in this study could be extrapolated as a tool to assess the desalination projects development in other world regions to make future desalination projects more viable and sustainable for addressing global water demands.

Energetic Comparison of Flow-Electrode Capacitive Deionization and Membrane Technology: Assessment on Applicability in Desalination Fields.

Flow-electrode capacitive deionization (FCDI) is a promising technology for sustainable water treatment. However, studies on the process have thus far been limited to lab-scale conditions and select fields of application. Such limitation is induced by several shortcomings, one of which is the absence of a comprehensive process model that accurately predicts the operational performance and the energy consumption of FCDI. In this study, a simulation model is newly proposed with initial validation based on experimental data and is then utilized to elucidate the performance and the specific energy consumption (SEC) of FCDI under multiple source water conditions ranging from near-groundwater to high salinity brine. Further, simulated pilot-scale FCDI system was compared with actual brackish water reverse osmosis (BWRO) and seawater reverse osmosis (SWRO) plant data with regard to SEC to determine the feasibility of FCDI as an alternative to the conventional membrane processes. Analysis showed that FCDI is competent for operation against brackish water solutions under all possible operational conditions with respect to the BWRO. Moreover, its distinction can be extended to the SWRO for seawater conditions through optimization of its total effective membrane area via scale-up. Accordingly, future directions for the advancement of FCDI was suggested to ultimately prompt the commercialization of the FCDI process.

Optimize and analyze a large-scale grid-tied solar PV-powered SWRO system for sustainable water-energy nexus

The lack of clean water and access to energy are two major obstacles to global sustainable systems. The development of solar photovoltaic (PV) technology gained the attention of water desalination projects due to its cost decline, carbon-free emission, and the on-site energy production. However, studies on in-depth analysis of the performance of these systems remain rare. This study performs a comprehensive a design optimization and seven-factor analysis (energy, exergy, economic, environmental, energoeconomic, exergoeconomic, enviroeconomic - 7E) of a grid-tied PV system powering a large-scale seawater reverse osmosis (SWRO) plant. First, an optimal design model is developed based on real hourly measured data for the SWRO load demand and renewable resources, while considering net energy metering mechanism. The objective function is delineated to diminish the energy cost of the system, concomitant with the imposition of operational constraints. Second, an analytical model is established to perform exergetic calculations for the optimal design. Third, a sensitivity analysis is conducted to show how the model parameters affect the system design and costs. The results show that the optimal system relies on a 4.25 MW solar PV array and a 3.125 MW grid-tied inverter. This configuration reduces the levelized cost of energy by 48.3 % and carbon emissions by 50 % compared to a grid-only system. The implementation of net-metering has also maximized the designed system's revenues to 263,834 $/year. Further, the optimally designed system achieves a lower levelized cost of water (0.2217 $/m3), minimal capacity shortage, and negligible unmet load ratios (0.048 %) despite grid outages. From the exergetic assessment, the proposed system has a high exergy efficiency (9.3 %) which can be achieved despite the high value of the exergy loss. Moreover, the energoeconomic and exergoeconomic indicators have recorded tiny values (3.35E-5 kWh/$ and 0.0311 kWh/$, respectively), which are considered a desired outcome. Notably, a profit of 4285.4$ is achieved through the sale of carbon emissions reduction. The sensitivity analysis revealed an increase in the system's total cost of 4.91 % and 9.36 % and the system's energy cost of 4.91 % and 8.7 % if the energy purchase price raised by 10 % and 20 %, respectively. Also, it indicates that a fall in the electricity sellback rate of 10 % would remarkably raise the system's energy cost by 47.3 %. Finally, reducing the PV-Inverter costs by 15 % would drop the system's net present and energy costs by 51.4 % and 60 %, respectively. Overall, the insights from this study have the potential to expedite the realization of sustainable development goals 6, 7, and 13, particularly in developing nations abundant in solar energy resources.

Combination of activated carbon/ultrafiltration as pre-treatment for seawater reverse osmosis plants

Seawater Reverse Osmosis (SWRO) is a common technology to treat seawater to comply high freshwater demand. Currently, the main issue of seawater/brackish water as the potential sources for drinking water is vulnerable to organic pollutants. An effective pre-treatment is crucial to maintain the efficiency of SWRO for sustainable operation. Optimization of the process could be performed by a hybrid membrane combination using commercial Activated Carbon (AC) with based material coconut shell/coal and Ultrafiltration membrane (UF). For hybrid process, the activated carbon was continuously dosed into the pilot scale filtration employing PES Hollow Fiber membrane with active area of 4 m² and average pore size of 10 nm that represents a real operation filtration process (i.e., filtration flux, filtration time, backwashing, and cleaning in place), and was performed until 8 filtration cycle sequence. This study investigated membrane performance with combination technique PAC/UF and GAC/UF in Pilot scale experiments within resistance membrane and retention membrane. Combination of Activated Carbon/Ultrafiltration showed synergistic effects in the removal of organic content for COD 40%-96%, UV-VIS 43%-92% and Turbidity 73%-99%. High removal of organics pollutants (COD, UV-VIS and Turbidity) was attributed to small average pore distribution of Activated Carbon (<10 µm) that increase adsorption process. Moreover, hybrid Activated Carbon/UF adsorption kinetics can reduce filtration times to achieved optimal retention. Related to membrane performance, hybrid AC/UF resulted in less permeability declines almost double in first two filtration cycle and slightly less permeability decline until fifth cycle in comparison with single UF process. Better membrane performance can furtherly be explained from less irreversible fouling in case of AC/UF. Combination AC/UF enhanced the control of Irreversible fouling and resulted in better filtration performance as well as higher organic substance removal. Therefore, hybrid AC/UF could be seen as an effective system as pretreatment for SWRO.

A theoretical analysis on upgrading desalination plants with low-salt-rejection reverse osmosis

Brackish water/seawater reverse osmosis (RO) desalination is a key solution to global freshwater scarcity. However, the water recovery (Rw) in conventional RO desalination plants is limited by the operating pressure (∆P). As a novel staged RO technology, low-salt-rejection RO (LSRRO) can potentially enhance the Rw in the desalination plants. In this study, we perform process modeling and techno-economic analysis to evaluate the viability of upgrading current RO desalination plants with LSRRO. Based on the results from process modeling, in typical brackish water RO (BWRO) and seawater RO (SWRO) desalination plants, adding an LSRRO stage can effectively enhance the Rw by 21 and 53 %, respectively, and the energy efficiencies are not compromised with the enhanced Rw. From techno-economic analysis, upgrading RO desalination plant with LSRRO is highly viable. Specifically, after adding an LSRRO stage in a BWRO plant, the Rw can be enhanced from 71 to 81 % without notably increasing the levelized cost of water (LCOW), and adding an LSRRO stage in the SWRO plant with zero brine discharge can reduce the LCOW by 30 %. The findings in our study highlight the vast potential of adopting LSRRO in brackish water/seawater desalination plants, and shed lights on the design of future desalination plants.

Review on an integrated pre-treatment system to reduce membrane accelerated biofouling during red tide occurrences in Oman

The increasing pressure on available freshwater resources to meet the demand for all human activities raised the importance of finding new water resources. Desalination of seawater and water reuse considered the most reliable sources of fresh water. Seawater desalination is a high-powered consuming process therefore seawater reverse osmosis desalination is currently the most widely implemented technology because of its lower power consumption compared to thermal desalination also it requires less footprint, generates less waste, and has reliable performance. To ensure preserving high performance of Seawater reverse osmosis (SWRO) plants, there is a need for an active pre-treatment system to deliver a continuous good quality feed for the RO membranes. Among various issues faces the use of RO membranes like chemical attack and scaling of membrane, but membrane fouling is the most challenging issue. As per the literature study, there are various pre-treatment systems implemented worldwide in SWRO plants and they are classified as conventional technologies including coagulation, sedimentation, media filtration, and flotation or membrane-based technologies like microfiltration, ultrafiltration, and nanofiltration. Conventional systems are more complex to design & operate, require a high footprint, and are better option when seawater has high contents of oil and organic matters. While membrane-based systems have less space requirements, simple to operate, and more effective for particulate matter removal but they are costly and sensitive for algal bloom. This comprehensive review study focusses on feasibility of utilizing Dissolved Air Flotation (DAF) in an integrated system that combines conventional and membrane pre-treatment systems to provide a decent quality feed water for SWRO. Integrated system is proposed as a pre-treatment system because dissolved air flotation characterized by high organic foulants removal and membrane-based pre-treatment are reliable and have high permeate flux.

Effectiveness of ceramic ultrafiltration as pretreatment for seawater reverse osmosis

The Gulf Cooperation Council (GCC) region's considerable reliance on seawater reverse osmosis (SWRO) for freshwater production is amplifying with increasing population and industrial growth. Nonetheless, harsh seawater conditions in the region coupled with ineffective pretreatment have triggered frequent SWRO plant shutdowns, premature RO membrane and cartridge filter replacements, and low plant availability. To improve plant performance and sustainability, an effective pretreatment is needed; a promising option is the use of ceramic membranes. To investigate their effectiveness for handling variable seawater conditions experienced in the region — specifically harmful algal blooms (HAB) — this work presents a pilot scale ceramic UF (CUF) pretreatment study. Operational reliability and treated water quality of CUF was evaluated against existing polymeric MF and UF pretreatment in adjacent SWRO plants. CUF operated at full capacity during HAB season, compared to 30–40 % reduction for the MF/UF plants. Furthermore, it produced superior permeate quality, despite variations in feedwater conditions — for instance, it removed over 5× more Dissolved Organic Carbon (DOC) and 1.5× more Transparent Exopolymer Particles (TEP) than the polymeric membranes. These results indicate the potential for CUF as an effective pretreatment for SWRO to minimize plant downtime and ensure consistent permeate quality during all seawater conditions.

Intelligent framework for coagulant dosing optimization in an industrial-scale seawater reverse osmosis desalination plant

Efficient and reliable desalination through seawater reverse osmosis (SWRO) mandates optimized pre-treatment strategies to minimize organic and inorganic fouling. Coagulation, the process of agglomerating colloidal particles using chemical coagulants, in combination with media filtration to reduce colloidal fouling on reverse osmosis membranes is commonly used in seawater pretreatment. Due to its inherent complexity and the absence of physical models to quantify the efficiency of coagulation, overdosing of coagulants is ubiquitously observed to maintain filtered water quality. To address this problem, we use Artificial neural networks (ANNs) to optimize coagulant dosing by predicting the SDI after chemical dosing. The model is developed by using large-scale plant data comprising of different seawater physical parameters and plant operational data including pH, SDI, turbidity, coagulant dosing rate, and flocculant dosing rate. By using feature engineering, selection, and our domain knowledge, new input parameters are derived, irrelevant parameters are eliminated, and these are used as inputs to train the model. The developed ANNs model achieved a prediction accuracy of 95% also outperforms other machine learning methods, and upon industrialization it reduced annual coagulant consumption by 11.7% when implemented in a commercial SWRO plant producing 216,000 m3/day of desalinated water.

Materials and Corrosion in Seawater Reverse Osmosis Plants: A Review

Desalination is emerging as one of the most promising solutions to extraction and increasing global demand for drinking water. A water purification process called reverse osmosis (RO), in which dissolved solids are separated from solutions by partially permeable membranes. Advances in membrane technology have resulted in the removal of up to 99% of salts in seawater. However, the process and system of seawater treatment RO are associated with many problems, such as scaling and fouling of the membranes, corrosion of the pumps, valves and piping system due to the highly concentrated salt solution and high chemical consumption. Nowadays, these problems have become very critical as they severely affect the desalination process and also massively deteriorate the performance and lifetime of the system components and materials. To ensure that the desalination process is always the best option for a low-maintenance, highly efficient and cost-effective system and process, a comprehensive study of these problems is essential. Therefore, this article addresses the characteristics of metallic materials and corrosion problems in the reverse osmosis process of seawater desalination, as well as the best solutions to focus on and evaluate for an optimal seawater desalination process, and the selection of the category of duplex stainless steels suitable for seawater desalination plants to reduce maintenance, avoid plant shutdown and ensure plant safety.

DESIGN AND EVALUATION OF A SEAWATER REVERSE OSMOSIS DESALINATION PLANT USING COMPUTER SOFTWARE

Seawater and brackish desalination using reverse osmosis (RO) has been a pragmatic approach to mitigating fresh water shortage in many water-stressed areas worldwide. Compared with other desalination technologies, RO has several attributes including high energy efficiency and system modularization. To achieve these notable attributes, for large-scale seawater RO plants, it is critical to accurately design and evaluate the RO process before plant installation and operation. In this study, the IMSDesign software is applied to design a seawater RO plant with a capacity of 100 m3 of fresh water per hour. The software allows to customize the design parameters and operating conditions of the RO plant to meet the design requirements. After inputting design parameters and operating conditions, the RO plant operation can be simulated to obtain its performance indexes for plant design evaluation. The evaluation results reveal that the RO plant with membrane trains arranged in 2-passes configuration can obtain high quality permeate that meets the required standards for drinking water at energy consumption and water cost of 10.66 kWh/m3 and 2.48 USD/m3, respectively.

SWRO Brine Characterisation and Critical Analysis of Its Industrial Valorisation: A Case Study in the Canary Islands (Spain)

The most recent years of research have shifted the perception of desalination brine from being waste to a high-value resource, in consonance with a circular economy perspective. The Canary Islands, containing the largest number of desalination plants per square kilometre in the world, are a perfect location to study its characteristics and evaluate its potential. A total of 10 heterogeneous seawater reverse osmosis plants were selected to determine the brine’s physicochemical characterisation, comprising 37 parameters, and its correlation to the technical and operational aspects of the desalination plants. The results show a stable narrow range of the percentage of major ions concentration in relation to the total dissolved solids (55% Cl−, 29.5% Na+, 8% SO42−, 4% Mg2+, 1.5% Ca2+, 1.2% K+, 0.5% HCO3−, and 0.2% Br−) irrespective of specific differences between plants. The results obtained in this study are highly beneficial to industrial suppliers and future users of desalination brine valorisation (DBV) technologies, allowing an estimation of the chemical composition of a brine through knowledge only of its conductivity. Such information is crucial before investing in and optimizing DBV technologies. Nonetheless, from an environmental, economic, operational, energy-based, and R&D point of view, several improvements are required to promote their large-scale feasibility and viability.

Analysis of Operational Parameters in Acid and Base Production Using an Electrodialysis with Bipolar Membranes Pilot Plant

In agreement with the Water Framework Directive, Circular Economy and European Union (EU) Green Deal packages, the EU-funded WATER-MINING project aims to validate next-generation water resource solutions at the pre-commercial demonstration scale in order to provide water management and recovery of valuable materials from alternative sources. In the framework of the WATER-MINING project, desalination brines from the Lampedusa (Italy) seawater reverse osmosis (SWRO) plant will be used to produce freshwater and recover valuable salts by integrating different technologies. In particular, electrodialysis with bipolar membranes (EDBM) will be used to produce chemicals (NaOH and HCl). A novel EDBM pilot plant (6.4 m2, FuMa-Tech) has been installed and operated. The performance of EDBM for single pass under different flowrates (2-8 L·min-1) for acid, base and saline channels, and two current densities (200 and 400 A·m-2), has been analyzed in terms of specific energy consumption (SEC) and current efficiency (CE). Results showed that by increasing the flowrates, generation of HCl and NaOH slightly increased. For example, ΔOH- shifted from 0.76 to 0.79 mol·min-1 when the flowrate increased from 2 to 7.5 L·min-1 at 200 A·m-2. Moreover, SEC decreased (1.18-1.05 kWh·kg-1) while CE increased (87.0-93.4%), achieving minimum (1.02 kWh·kg-1) and maximum (99.4%) values, respectively, at 6 L·min-1.

Elevation-distributed multistage reverse osmosis desalination with seawater pumped storage

A seawater reverse osmosis (RO) plant layout based on multistage RO with stages located at different elevations above sea level is described. The plant uses the weight of a seawater column from pumped storage as head pressure for RO (gravity-driven multistage RO) or to supplement high-pressure pumps used in RO (gravity-assisted multistage RO). The use of gravitational force reduces the specific energy for RO compared to using high-pressure pumps. By locating the RO stages at different elevations based on demand sites, the total specific energy consumption for RO and permeate transport to different elevations above sea level is reduced from that for locating the RO process entirely at sea level followed by lifting the desalinated water. A final RO stage at sea level uses seawater pressurized by energy recovery from the residual energy of the brine generated from the preceding RO stage. Examples of the plant layout that do not include pump inefficiency and head losses in pipes are described for South Sinai, Egypt, which is a mountainous region that suffers from water scarcity. A gravity-driven multistage RO with a storage tank at 660 m above sea level is considered. For five RO stages located 316–57 m above sea level with 10% recovery at each stage, the specific energy is ~ 32% lower than that for a plant located at sea level operating at the minimum specific energy followed by lifting the same quantity of desalinated water to the elevations of the distributed RO stages. For two stages located at 222 and 57 m above sea level with 30 and 20% recovery, respectively, the reduction in specific energy is ~ 27%. For gravity-assisted five-stage RO with the first stage at 260 m above sea level, while the last stage is at sea level with 10% recovery at each stage the reduction in specific energy is ~ 32%. The proposed RO plant layouts can be adapted to other regions with comparable topography.

A scalable method to fabricate high-performance biomimetic membranes for seawater desalination: Incorporating pillar[5]arene water nanochannels into the polyamide selective layer

In this work, we explored the practicability of a nanochannel-based biomimetic membrane (NBM) incorporating pillar[5]arene water channels for seawater reverse osmosis (SWRO) desalination. Two classes of peptide-attached biomimetic channels, (pR)-pillar[5]arenes (pRPH) and (pS)-pillar[5]arenes (pSPH) were integrated into the selective layer of SWRO membranes via interfacial polymerization on the top side of a polysulfone (PSf) support membrane. Here, pSPH is a non-identical stereoisomer of pRPH and was used as a negative control to pRPH to elucidate the flux enhancement effect contributed by pRPH. The optimized NBM presented a water permeability of 2.52 L m-2 h-1 bar-1 and 99.5% rejection under SWRO testing conditions of 50 bar applied pressure and 32,000 mg/L NaCl as feed solution. The 62% permeability increment with reference to the control membrane is hypothesized to originate from hybrid polyamide layers that were rougher with more voids (higher effective surface area and lower hydraulic resistance for water transport) as well as the conceivable water transport pathways provided by the pRPH channels. The simulation results from module-scale modelling suggest that the optimized NBM could lead to 7.2% savings in specific energy consumption of the membrane unit stage (or reduce the required membrane area by 25%) with respect to the commercial SWC4-LD membrane. The performance of the optimized NBM was further assessed in a one-week desalination test using an actual seawater feed gathered from an SWRO plant in Singapore. The robust NBM exhibited stable performance and ∼28% higher water flux (42 L m-2 h-1) than SWC4-LD with a comparable rejection of 99.3%, suggesting the feasibility of pillar[5]arene-based biomimetic membranes for seawater desalination.

Performance model for reverse osmosis

To meet the increasing global demand for freshwater, seawater reverse osmosis (SWRO) has become a widely used technology to produce freshwater from seawater. A SWRO system consists of different components such as pumps, membranes, valves, and energy recovery devices. While it may be simple for process designers to understand the individual performance of each piece of equipment, the performance of an entire SWRO system can be complex and counter-intuitive. Furthermore, SWRO processes are energy-intensive; thus, to minimize the Specific Energy Consumption (SEC) of the process, it is of utmost importance that the performance of the system is monitored in real-time. Due to periodic changes in seawater quality and weather conditions, the operating parameters in a SWRO plant need continuous tweaking to minimize energy consumption and optimize the use of chemicals such that product water quality requirements are met. This calls for the need of a performance monitoring and optimization tool for SWRO. Since the advent of RO in 1950, such a system has never existed. Here, we present the first performance model for reverse osmosis (PMRO) for monitoring and optimizing the performance of SWRO assets;the developed model predicts the SEC of an operating SWRO plant with 93 % accuracy.

Life cycle assessment and cost of a seawater reverse osmosis plant operated with different energy sources

Seawater desalination plants consume significant amounts of energy sourced primarily from fossil fuels, leading to significant environmental impact. Life Cycle Assessment has been applied to desalination systems powered by a single renewable energy source with the underlying assumption of sufficiency of power supply. However, in several locations in the world the intermittent nature of these renewable sources prevents a full reliance on a single source and necessitates a combined fossil fuel-renewable energy mix. This study addresses this issue by performing life cycle assessment and preliminary costing analysis for different renewable-energy-grid combinations (photovoltaic-grid, wind-grid and anaerobic digestion-grid). Whilst the grid-anaerobic digestion and grid-photovoltaic scenarios provided significant improvements in all environmental impact categories, the grid-wind energy option resulted in the highest reduction whereby a 60% decrease in carbon footprint was observed. The unit product cost for the environmentally optimum grid-anaerobic digestion scheme was the lowest at 0.94 $/m3, while the unit product cost for the grid-photovoltaic scheme was the most expensive at 1.47 $/m3. An integrated photovoltaic-wind-anaerobic digestion scheme may offer further reduction in environmental impact and a potentially lower unit product cost.

Energy and water without carbon: Integrated desalination and nuclear power at Diablo Canyon

A seawater reverse osmosis (SWRO) desalination plant collocated with an existing nuclear plant would have low electricity costs, could share the power plant’s seawater intake and outfall, and would have zero carbon footprint during operation. Unlike thermal desalination technologies, electrically-driven SWRO is ideal for retrofitting existing power plants because the turbines and condensers would not need expensive modifications. Here, we evaluate the techno-economic feasibility of collocating a large-scale SWRO plant with an existing nuclear power plant, specifically the 2.2 GWe Diablo Canyon Nuclear Power Plant on California’s central coast. The seawater that cools the nuclear plant’s condensers provides the feed water for desalination. The desalination brine is diluted with the remaining condenser coolant before being discharged to the ocean. A brushed-screen intake structure, serving both the nuclear power plant and the desalination plant, can comply with strict California regulations protecting marine organisms. This coproduction arrangement has a significant cost advantage relative to a stand-alone desalination plant. The levelized cost of water (LCOW) ranges from US$0.77 to US$0.98 per m3 of fresh water, with water distribution to offtakers adding US$0.02 to US$0.21 per m3 over 20–185 km. In comparison, California’s largest desalination plant, in Carlsbad, has an LCOW of about US$1.84 per m3. These cost savings result from reduced power costs (about US$0.054 per kWh) and from sharing some expensive infrastructure. Further, nuclear electricity allows a Carlsbad-size SWRO to avoid 47 kt/y of CO2 emissions relative to grid electricity. Examination of substantially larger desalination plants introduces additional considerations. This study is the first to show that collocated SWRO and nuclear power are strongly coupled and have a significant economic advantage over seawater desalination at other sites. These benefits should apply to dozens of existing nuclear power plants worldwide.

A thermally-driven seawater desalination system: Proof of concept and vision for future sustainability

Since the 1970s, commercial-scale thermally-driven seawater desalination plants have been powered by low-grade energy sources, drawn either with low-pressure bled-steam from steam turbines or the solar renewable energy harvested that are supplied at relatively low temperatures. Despite the increasing trend of seawater reverse osmosis plants, the role of thermal desalination methods (such as multi-stage flashing and multi-effect distillation) in GCC countries is still relevant in the Arabian Gulf, arising from higher salinity, the frequent algae blooms of seawater and their ability to utilize low temperature heat sources. Given the urgent need for lowering both the capital and operating costs of all processes within the desalination industry and better thermodynamic adaptation of low-grade heat input from renewable sources, the present paper addresses the abovementioned issues by investigating the direct contact spray evaporation and condensation (DCSEC) method. A DCSEC system comprises only hollow chambers (devoid of membranes or tubes, minimal use of chemical and maintenance) where vapor generation (flashing) utilizes the enthalpy difference between the sprayed feed seawater and the saturated vapor enthalpy of the vessels. Concomitantly, vapor is condensed with spray droplets of cooler water (potable) in adjacent condenser vessels, employing a simple design concept. We present detailed design and real seawater experiments data of a DCSEC system for the first time. The water production cost is calculated as $0.52/m 3 , which is one of the lowest figures reported compared to commercial processes presented by Global Water Intelligence.

Off-grid SeaWater Reverse Osmosis (SWRO) desalination driven by hybrid tidal range/solar PV systems: Sensitivity analysis and criteria for preliminary design

This paper deals with innovative renewable energy (RE) - powered seawater reverse osmosis (SWRO) plants based on tidal range/PhotoVoltaic (PV) systems as a hybrid technology with interesting prospects to promote the RE desalination at medium to large capacity ranges. Key features to enhance solar PV with tidal range energy are the good temporary complementarity of both options and the predictable water production pattern that the tidal range plant allows, along with ensuring water production at night. Once the basic sizing of a power plant referred to a 20 MW turbine is conducted, the sensitivity analysis of main performance parameters of the hybrid solar/tidal desalination system is carried out through yearly simulations. With this analysis, an extension of the knowledge about the performance of hybrid tidal/solar desalination is gained in such a way that three useful design criteria are derived from the results: i) total investment cost per unitary water production, ii) energy consumed in desalination to total energy production, and iii) energy non-useful for desalination. Recommended designs are provided under each of these three criteria for given yearly freshwater demand with SWRO plants of 3.5 and 4.8 kWh/m3 of specific energy consumption. Results proves that off-grid SWRO desalination powered by hybrid tidal/PV systems in a favorable location achieves actual water production of one half of nominal production with adequate selection of design parameters. Recommended sizing of the energy generator for minimizing capital costs corresponds to 20 MW tidal/25–27 MWp PV per 12 MW of SWRO consumption. Additionally, in absence of realistic costs data, the recommended design criterion for the plant sizing relies on the ratio of energy used by the desalination plant to that produced by the hybrid tidal/PV generator. Results at an exemplary plant location show that 14.1 × 106 m3/y of fresh water obtained with desalination consumption of 3.5 kWh/m3 needs 2.0 MW tidal/26.9 MWp PV. This energy system would produce 10 × 106 m3/y considering 4.8 kWh/m3 of specific consumption.

Biofouling of seawater reverse osmosis membranes caused by dispersal of planktonic particulate bacterial aggregates (protobiofilms) from rotary energy recovery devices

A seawater reverse osmosis (SWRO) plant in the Arabian Gulf region showed serious membrane biofouling that appeared to be due to the presence of planktonic particulate bacterial aggregates that can be termed as “protobiofilms”, which possessed the same characteristics of surface-attached biofilms. This SWRO plant utilized dissolved air flotation and ultrafiltration for pretreatment, high permeable SWRO membranes for desalination and incorporated rotary energy recovery devices (RERD). During the first year of operation, a slow steady increase in TMP and channel ∆P was observed that appeared due to membrane biofouling from either colloidal small bacterial aggregates or individual bacterial cells. After the first year of operation, the TMP and channel ∆P increased at an accelerated rate that appeared due presence of planktonic particulate bacterial aggregates. An internal membrane hybridization (IMH) program was initiated after the second year of operation by replacing the two highly fouled high permeable membranes in the feed-end of the pressure vessel with new low permeable membranes to lower the flux and concentration polarization (CP) of the feed-end membranes and to lower the membrane fouling potential. Biofouling of these new low permeable membranes in the IMH program resulted in an immediate and an accelerated increase in both TMP and channel ∆P, which was attributed to the presence of significant concentration of planktonic particulate bacterial aggregates that appeared due to dispersal of a biofilm from the RERD. An important factor that contributed to the dispersal of bacterial aggregates into the RO feed water was the flow velocity through the RERD. Decreasing the flow velocity into and cleaning of the RERD resulted in a significant decrease in the rate of RERD biofilm dispersal and biofilm formation on the SWRO modules.