Brackish Water Reverse Osmosis Desalination Research Articles

Synthesis of high-performance biocompatible polymeric membranes incorporated with zirconium-based MOF for an enhanced brackish water RO desalination

A nanosized zirconium 1,4- dicarboxybenzene metal-organic framework (UiO-66-MOF) was synthesized and impregnated into cellulose acetate (CA) polymeric matrix to enhance the membrane characteristics for brackish water desalination. Phase inversion was used for the fabrication of CA/UiO-66 hybrid membranes (CAU-X), where X is the concentration of immobilized UiO-66 nanoparticles (UiO-66-NPs) into CA polymeric matrix. Morphological structure and functional groups were investigated through different characterization techniques to prove the successful synthesis of the prepared UiO-66-NPs, the blank CA membrane, and hybrid CAU-X membranes. For more CAU-X characteristics, porosity, contact angle, and tensile strength were measured. The obtained data demonstrated that the impregnation of zirconium-based-NPs had a positive influence on the blank CA membrane properties. Additionally, the performance of the fabricated membranes was investigated in reverse osmosis (RO) bench-scale unit. The performance results for the pristine CAU-0 membrane showed a high salt rejection (SR) of 99.8% and a permeate water flux (PWF) of 1.14 L/m2.h. In comparison to pristine CA membrane, CAU-X hybrid membranes have a slightly lower SR and a higher PWF. It was found that the hybrid CAU-0.02 membrane had almost a doubled PWF of 2.8 L/m2.h with only 2% sacrificed SR of 97.6% compared with CAU-0 membrane. Moreover, a much better PWF of 3.4 L/m2h and a sufficient SR of approximetly 92% were obtained by CAU-0.05 membrane. Thus, CAU-0.05 was selected to further test its performance under different operating parameters. Results revealed that the optimum parameters were recorded for a sodium chloride feed stock of 5000 ppm operating at 25 °C temperature and pressure up to 15 bar.Graphical

Innovative system for BWRO desalination powered by PV and pumped hydro storage – Economic and GHG emissions analysis

Brackish water reverse osmosis (BWRO) desalination driven by photovoltaic (PV) system as a primary energy source and pumped hydro storage (PHS) as an intermediate storage offers an energy-efficient and competitive solution to overcome freshwater scarcity. This innovative system for drinking water production from brackish groundwater was developed and technically analyzed in a prior work. In this paper, the entire system with two power supply scenarios: scenario 1 (PV, PHS and battery storage) and scenario 2 (PV, PHS and grid) is economically assessed and its greenhouse gas (GHG) emissions are analyzed. Thereafter, this system is compared with the state-of-the-art and BWRO systems powered by a conventional energy source (grid or diesel generator) to discuss and evaluate the future role of this innovative system in the BWRO desalination market. For off-grid operation, the innovative system with scenario 1 is the most economical system for drinking water production from brackish groundwater compared to the other examined systems as long as the diesel fuel price is equal to or more expensive than 0.58 US$/L. Moreover, the minimum specific GHG emissions produced per unit of drinking water production in scenario 1 is 46.8 % less than in the current system (PV and battery storage).

Hybrid BWRO/FO system for high recovery in-land brackish water desalination: techno-economic assessment

Several hybrid Forward osmosis (FO) systems for seawater and brackish water desalination have been developed in recent years. This study investigates two approaches of integrated systems comprising brackish water reverse osmosis desalination (BWRO) and forward osmosis (FO) systems. These approaches aim to minimize the environmental effect of inland reject brine disposal while enhancing total water recovery. Experiments were performed using different draw solution (DS) concentrations of KCl and MgCl2.6H2O (0.5, 1, 1.5 and 2 Molar) to reach maximum recovery. In scheme (A), feed water is directed to BWRO with recovery 45% and 97% rejection, while the brine water is directed to the FO system as FS stream. In scheme (B), the feed water is divided into two streams, one of which is directed to the BWRO with recovery 75% and 98% rejection and the other stream is sent to the FO unit as FS stream. KCl DS displayed higher flux rate of an average 28.5 L/(m2.h) using 2 M concentration, while MgCl2.6H2O 2M solution shows an average flux of 23.5 L/(m2.h) during the first 100 min of operation. Scheme A shows 81% total system recovery, while scheme B shows 78% total system recovery. The cost indicators for desalination system with small capacity of 10 m3/d showed that scheme (A) has lower capital cost 55,732$ for scheme (A), while total capital cost was 59,400 $ for scheme (B).

Raman spectroscopy for real-time concurrent detection of multiple scalants on RO membranes

In-situ monitoring techniques of reverse osmosis (RO) desalination systems, particularly those with chemical sensing capabilities, can provide the means for better understanding important scaling mechanisms as well as early scaling detection. In this work, both calcium sulfate and calcium carbonate scaling on RO membranes were detected concurrently in real time using Raman spectroscopy to provide a unique chemical fingerprint. Two different sampling methodologies (manual and automated) were employed, and their performance was evaluated by comparing the Raman detection times to concurrent values of flux decline. The manual sampling strategy resulted in the detection of calcium sulfate and calcium carbonate at mean permeate flux declines of 13 ± 10 % and 22 ± 3 %, respectively. The automated sampling strategy provided better performance, with detection of calcium sulfate and calcium carbonate at mean flux declines of 8 ± 5 % and 4 ± 3 %, respectively. The increased sensitivity and decreased variability of the automated sampling strategy provided valuable preliminary insights for the selection of optimized sampling strategies. The ability to identify the chemical composition of different scaling crystals including their polymorphs is an important step toward better understanding of the crystallization pathways of multi-component feed streams used in seawater and brackish water RO desalination.

Simulation and optimisation of a medium scale reverse osmosis brackish water desalination system under variable feed quality: Energy saving and maintenance opportunity

In this work, we considered model-based simulation and optimisation of a medium scale brackish water desalination process. The mathematical model is validated using actual multistage RO plant data of Al- Hashemite University (Jordan). Using the validated model, the sensitivity of different operating parameters such as pump pressure, brackish water flow rate and seasonal water temperature (covering the whole year) on the performance indicators such as productivity, product salinity and specific energy consumption of the process is conducted. For a given feed flow rate and pump pressure, winter season produces less freshwater that in summer in line with the assumption that winter water demand is less than that in summer.With the soaring energy prices globally, any opportunity for the reduction of energy is not only desirable from the economic point of view but is an absolute necessity to meet the net zero carbon emission pledge by many nations, as globally most desalination plants use fossil fuel as the main source of energy. Therefore, the second part of this paper attempts to minimise the specific energy consumption of the RO system using model-based optimisation technique. The study resulted not only 19 % reduction in specific energy but also 4.46 % increase in productivity in a particular season of the year. For fixed product demand, this opens the opportunity for scheduling cleaning and maintenance of the RO process without having to consider full system shutdown.

Reduction of Energy Consumption of Brackish Water Reverse Osmosis Desalination System Via Model Based Optimisation

Reverse Osmosis (RO) process is being engaged to yield fresh water from brackish water sources. However, the RO process is characterized by its high specific energy consumption (SEC) owing to high-pressure pumps. The current study focuses on reducing the SEC of the brackish water RO desalination plant using model-based optimization practice. The inlet conditions of RO process such as the feed pressure, flow rate (individual membrane module and total plant) and temperature, have a substantial influence on the performance indicators namely, water productivity, product concentration and SEC. Therefore, the optimisation of this study has been directed to determine optimal inlet conditions within feasible limits to minimise SEC. Arab Potash Company (APC) brackish water RO desalination plant has been considered as the case study. The optimal inlet conditions have resulted in a significant energy saving of 27.97% depending on the set of decision variables being considered at a fixed brackish water feed concentration.

Pumping-Induced Feed Water Quality Variation and Its Impacts on the Sustainable Operation of a Brackish Water Reverse Osmosis Desalination Plant, City of Hialeah, Florida, USA

Brackish water reverse osmosis (BWRO) desalination of groundwater is believed to be a sustainable method of providing municipal utilities with a high-quality supply in regions where freshwater sources are stressed and not sustainable. A key aspect of water management is the ability to evaluate an aquifer containing brackish water to ascertain future pumping-induced water quality changes and their impacts on the facility operation and economics. The city of Hialeah, Florida, has operated a BWRO facility for the last 9 years. The facility has a maximum design capacity of about 88,000 m3/d but is currently operating at about 33,000 m3/d. The facility was designed to treat water with a TDS of up to 10,000 mg/L. A detailed hydrogeologic investigation, including groundwater solute-transport modeling, suggested that the salinity of the source water would remain under 10,000 mg/L of TDS during the 30-year life expectancy of the facility. However, after 9 years of operation, it was found that the rate of salinity increase was much higher than predicted (27.5%), at the low rate of 33,000 m3/d. If the faculty was operated at the maximum capacity, the ability of the plant to treat the source water might be between 5 and 10 years. The conceptual model used to guide the solute transport modeling was not accurate for this site because it did not incorporate the apparent enhanced leakance through the basal confining unit below the aquifer. The greater leakance was likely caused by undetected, irregularly distributed fracturing of the underlying confining dolostones. The facility will require a major redesign to upgrade the process to be able to treat seawater at a TDS significantly above 10,000 mg/L in the future, should that occur. While the change will be costly, with a high capital cost to change the process, increased energy consumption, and overall higher water treatment cost, it is still more sustainable and has less environmental impact compared to other alternatives (e.g., treating tidal sources of seawater). The use of electricity from nuclear or solar generation could mitigate the environmental impacts of higher power consumption.

Simulation and Optimisation of a Medium Scale Reverse Osmosis Brackish Water Desalination System: Energy Saving and Maintenance Opportunity

Simulation and Optimisation of a Medium Scale Reverse Osmosis Brackish Water Desalination System: Energy Saving and Maintenance Opportunity

Techno-Economic Analysis of Selected PV-BWRO Desalination Plants in the Context of the Water–Energy Nexus for Low–Medium-Income Countries

Jordan was late in adopting seawater and brackish water desalination as a source until the late 1990s and early 2000s. However, ongoing studies are still discussing the technical, economic, and socio-political aspects of brackish water reverse osmosis (BWRO) desalination plants. In this study, the water–energy nexus was considered, in order to highlight the main challenges facing BWRO desalination. We discuss the use of photovoltaic (PV) technology, together with BWRO desalination, as an approach to compensate for ecological, financial, and social challenges in Jordan. For this purpose, the performance of nine existing BWRO desalination plants in the agricultural, domestic, and industrial sectors is assessed. The water performance is assessed based on water consumption, safe yield extraction, plant recovery rate (R, %), and compliance to local and international water quality standards; the Specific Energy Consumption (SEC, kWh/m3) is taken as the main evaluation criterion to assess the energy performance of the BWRO desalination plants; and economic performance is assessed based on the overall cost of water produced per cubic meter (USD/m3). The main environmental component is the brine disposal management practice utilized by each plant. Based on this assessment, the main challenges in BWRO desalination are the unsustainable patterns of water production, mismanaged energy performance, low recovery rates, and improper brine disposal. The challenges in domestic and industrial BWRO desalination, which are completely dependent on the electricity grid, are associated with critical energy and costs losses, as reflected by the high SEC values (in the range of 2.7–5.6 kWh/m3) and high water costs per cubic meter (0.60–1.18 USD/m3). As such, the use of PV solar panels is suggested, in order to reduce the electricity consumption of the assessed BWRO plants. The installation of PV panels resulted in significantly reduced energy costs (by 69–74%) and total costs (by 50–54%), compared with energy costs from the electricity grid, over the lifetime of the assessed BWRO desalination plants.

Optimal sizing of an integrated CHP and desalination system as a polygeneration plant for supplying rural demands

Simultaneous production of electricity, heat, and water is a global challenge for rural residential areas. In the present study, techno-economic optimization of a system including PV, wind turbine, generator, battery, and CHP system alongside brackish water reverse osmosis desalination system is investigated. The proposed polygeneration hybrid system provides the required loads of a village and health clinic in a rural area with a warm climate. This study aims to find the optimum energy cost of essential rural needs, including required electricity, heat, and water demands to improve remote areas' life quality. While previous studies often considered only one or two of these needs. Several sensitivity analyses based on the different economic and climate conditions are carried out. The grid breakeven distance, environmental aspects, and the developed hybrid energy system's technical performance are analyzed. The results demonstrate that the optimum system, including PV/WT/DG/CHP/Bat and reverse osmosis desalination unit has COE and NPC equal to 0.236 $/kWh and 428,246 $, respectively. Also, the CHP unit decreased the annual fuel consumption by about 224 m3/yr. Furthermore, the proposed hybrid system has a 58.4% lower CO2 emission than conventional natural gas-fired plants and less than 27 km of grid breakeven distance.

Assessing the potential of highly permeable reverse osmosis membranes for desalination: Specific energy and footprint analysis

The ultra-permeable membranes (UPMs) are expected to reduce the specific energy consumption (SEC) of desalination, but the potential of UPMs in hollow fiber configuration has not been well quantified. Herein, we analyse the SEC and footprints of UPM modules in three feed salinities: seawater reverse osmosis (SWRO), brackish water RO (BWRO) and low-pressure RO (LPRO). Through the modelling the fluid dynamics and mass transport of RO systems, we find that a tripling in spiral-wound SWRO membrane permeability (based on the current value of 1 L m−2 h−1 bar−1; LMH/bar) could result in 16% decrease in SEC. Contrastingly, the quadrupling of hollow fiber SWRO membrane permeability (based on the current value of 0.25 LMH/bar) could reduce the SEC by 23%. According to our analysis, hollow fiber and spiral-wound SWRO membranes with permeabilities up to 1 LMH/bar and 3 LMH/bar, respectively, can reduce the SEC of seawater desalination. On the other hand, membranes with permeabilities up to 9 LMH/bar and 12 LMH/bar can lead to SEC savings in BWRO and LPRO desalination, respectively. This study provides a general guidance to RO membrane researchers on the permeability upper-limit of which UPMs could bring about SEC and footprint savings at a system level.

Novel dynamic and cyclic designs for ultra-high recovery waste and brackish water RO desalination

There is a drive for ultra-high recoveries in waste and brackish water RO desalination due to high brine disposal costs. In this work, two novel dynamic and cyclic designs (i.e. feed reversal and retentate recycle with a time-varying ratio in stage 3, as well as stage rotation between 1 and 3) are proposed to achieve a 90% recovery while alleviating scaling potential. The designs are conducted following FilmTec's guidelines and are simulated using validated models published previously. It is shown that retentate recycle suppresses concentration polarization, despite a higher pressure drop. Feed reversal leads to a quick drop of salt concentration due to mixing of fresh feed and brine. However, if the feed reversal is applied to the same stage, the salt concentration on the other end may be higher than brine concentration for a short period of time. Such a behavior is not observed during rotations between stages 1 and 3, whether the feed is reversed or not. Interestingly, the designs at 90% recovery demand only a few percent more energy than traditional two-stage designs operated at 80% recovery. Moreover, cycle-to-cycle salt build-up in batch-type ROs is absent in both dynamic designs presented in this work.

Thermodynamic Limitations and Exergy Analysis of Brackish Water Reverse Osmosis Desalination Process.

The reverse osmosis (RO) process is one of the most popular membrane technologies for the generation of freshwater from seawater and brackish water resources. An industrial scale RO desalination consumes a considerable amount of energy due to the exergy destruction in several units of the process. To mitigate these limitations, several colleagues focused on delivering feasible options to resolve these issues. Most importantly, the intention was to specify the most units responsible for dissipating energy. However, in the literature, no research has been done on the analysis of exergy losses and thermodynamic limitations of the RO system of the Arab Potash Company (APC). Specifically, the RO system of the APC is designed as a medium-sized, multistage, multi pass spiral wound brackish water RO desalination plant with a capacity of 1200 m3/day. Therefore, this paper intends to fill this gap and critically investigate the distribution of exergy destruction by incorporating both physical and chemical exergies of several units and compartments of the RO system. To carry out this study, a sub-model of exergy analysis was collected from the open literature and embedded into the original RO model developed by the authors of this study. The simulation results explored the most sections that cause the highest energy destruction. Specifically, it is confirmed that the major exergy destruction happens in the product stream with 95.8% of the total exergy input. However, the lowest exergy destruction happens in the mixing location of permeate of the first pass of RO desalination system with 62.28% of the total exergy input.

Economics and Energy Consumption of Brackish Water Reverse Osmosis Desalination: Innovations and Impacts of Feedwater Quality.

Brackish water desalination, using the reverse osmosis (BWRO) process, has become common in global regions, where vast reserves of brackish groundwater are found (e.g., the United States, North Africa). A literature survey and detailed analyses of several BWRO facilities in Florida have revealed some interesting and valuable information on the costs and energy use. Depending on the capacity, water quality, and additional scope items, the capital cost (CAPEX) ranges from USD 500 to USD 2947/m3 of the capacity (USD 690–USD 4067/m3 corrected for inflation to 2020). The highest number was associated with the City of Cape Coral North Plant, Florida, which had an expanded project scope. The general range of the operating cost (OPEX) is USD 0.39 to USD 0.66/m3 (cannot be corrected for inflation), for a range of capacities from 10,000 to 70,000 m3/d. The feed-water quality, in the range of 2000 to 6000 mg/L of the total dissolved solids, does not significantly impact the OPEX. There is a significant scaling trend, with OPEX cost reducing as plant capacity increases, but there is considerable scatter based on the pre- and post-treatment complexity. Many BWRO facilities operate with long-term increases in the salinity of the feedwater (groundwater), caused by pumping-induced vertical and horizontal migration of the higher salinity water. Any cost and energy increase that is caused by the higher feed water salinity, can be significantly mitigated by using energy recovery, which is not commonly used in BWRO operations. OPEX in BWRO systems is likely to remain relatively constant, based on the limitation on the plant capacity, caused by the brackish water availability at a given site. Seawater reverse osmosis facilities, with a very large capacity, have a lower OPEX compared to the upper range of BWRO, because of capacity scaling, special electrical energy deals, and process design certainty.

Decentralized brackish water reverse osmosis desalination plant based on PV and pumped storage - Technical analysis

Photovoltaic driven decentralized reverse osmosis plants for brackish water desalination offer a sustainable and low-emission solution for water deficiency problems, especially in arid and semi-arid regions. However, the primary challenge for this combination is how a brackish water reverse osmosis desalination (BWRO) plant based on photovoltaics (PV) can be operated continuously with high energy efficiency. Therefore, this study presents an innovative concept for a BWRO plant operated 24 h/d with a constant drinking water production capacity based on PV and pumped storage as hydraulic energy storage. The latter is used to cover the hydraulic energy consumption of the BWRO process completely or partially in times when the necessary electrical power cannot be provided by the PV plant due to missing solar radiation. During the course of the year, only 2% of the hydraulic energy to be stored in the pumped storage is lost during charging and discharging. The overall efficiency (from PV electricity to used hydraulic energy) of the pumped storage in the investigated innovative system is 78.4%. This value is 2.4% higher than the overall efficiency for a battery system with a high pressure pump in the current designs for BWRO based on PV and battery.

A pre-treatment concept for increasing the recovery ratio of coastline BWRO plants, while providing Mg2+ in the product water

The maximal recovery ratio of brackish water RO desalination plants located on the coastline can be significantly increased by exchanging Ca2+ with Mg2+ and Na+ ions in the raw water by passing the water through a cationic ion-exchange (CIX) resin which is thereafter regenerated with seawater. The concept allows also enriching the product water with Mg2+, at no additional cost. The Ca2+ fraction (equivalent-based) attached to the CIX resin at equilibrium with seawater was merely ~10% of its total capacity, much lower than Na+ (59%) and Mg2+ (28%). The process was simulated on the Sabha-Eilat BWRO plant (Israel) water with the goal of reducing [Ca2+] from ~850 to ~450 mg/L using a breakthrough/seawater-regeneration sequence. The goal was met by applying a 60 bed-volume (BV) breakthrough-step followed by 20-BV seawater regeneration (HRT = 6 min). ~2% of the CIX-mended water bypassed the RO step to provide 10 mg Mg/L in the product water. Simulating the maximal recovery ratio showed that it could be raised to 89.2%. A general design and cost-analysis revealed that the cost of each additional m3 of desalinated water produced by the new method was ~$0.23, ~14% more water is produced and retentate production is ~50% lower.

Energy-water nexus in East Iraq: capacity potential analysis and spatial assessment for an integrated CSP solar power & RO brackish water desalination plant in Khanaqin area

Abstract In this research, an analysis of site suitability and potential desalination capacity for an integrated concentrated solar power (CSP) and reverse osmosis (RO) system can be established to overcome water-energy nexus problems such as water supply shortage, fossil fuel carbon emission, and increasing power consumption in Khanaqin area, East Iraq. Regarding various environmental and economic criteria, the analysis employed different methods and tools: analytical hierarchy process (AHP) method, additive weighting method for location selection (SL), and kriging interpolation with map algebra spatial analysis tools in ArcGIS software. The chosen criteria were assessed by using the rating method, and then the relative weight of each criterion was determined. Site suitability assessment results showed that only 0.05% of the study area, represented by thirteen sites, was highly suitable for the integrated CSP-RO system. Considering higher potential desalination capacity of the integrated CSP-RO system, the number of suitable sites was further refined, therefore only two plant sites were suggested for optimum desalination capacity. The current study helps to quantify factors related to establishing and operating combined CSP and RO plant, which aid for further insight investigations on solar and water resources availability of similar systems for different areas around the world.

Enhanced exergy analysis of a full-scale brackish water reverse osmosis desalination plant

Brackish water desalination by reverse osmosis membranes is energy-driven process. With the purpose of improving the energy performance of such unit a full-scale BWRO desalination plant located in Canary Island (Spain) has been working under intermittent operating conditions for 14 years was assessed with conventional and enhanced (exogenous and endogenous/avoidable and unavoidable exergy destructions) exergy analysis. The exergies across the major components of the plant are calculated. The conventional exergy analysis reveals that, largest irreversibilities were identified in the RO system (membrane modules), the high pressure pump and the feed pump which amounts to about 64.28%, 40.84% and 38.48% respectively. Results of advanced exergy analyses shows that 70.61%, 92.94% and 7.83% of the total exergy destruction in the high pressure pump, feed pump and the RO system respectively are avoidable. Moreover, the highest endogenous avoidable exergy destruction rate was determined owing to the feed and high pressure pumps. Using these findings, instructions were proposed to ensure optimal effectiveness of the RO system and to improve the exergy destruction in the pumps currently in use.

Performance evaluation of a medium-scale industrial reverse osmosis brackish water desalination plant with different brands of membranes. A simulation study

Brackish water can be considered an important source of fresh water, via desalination, especially for arid districts. Reverse Osmosis (RO) process has been successfully used to produce fresh water from brackish water sources. However, there is still the challenge of improving the performance of multistage RO desalination plants. From the selection of the RO configurations to the selection of the appropriate type of membranes and the operating conditions at the end determines the performance of RO process in terms of recovery, salt rejection, energy consumptions and ultimately the cost of production of freshwater. Using model-based simulation, this work attempts to investigate the most suitable types of membranes for an industrial scale RO plant from a set of different membrane brands that would attain the highest-performance at lowest specific energy consumption (SEC). As a case study, we considered a multistage multi-pass medium-scale RO plant (1200 m3/day) of Arab Potash Company (APC, Jordan) which produces high quality water for the boilers after pre-treatment stage. The simulation results confirmed that employment of the Filmtec BW30LE-440 would increase water recovery by about 22% besides reducing the product salinity and SEC by about 15% and 10%, respectively compared to the existing membrane.

Smart system management and techno‐environmental optimal sizing of a desalination plant powered by renewables with energy storage

The present study assessed the performances of a brackish water reverse osmosis desalination unit powered by (PV/Wind/Battery) system with hydraulic storage. The hybrid renewable energy system and the reverse osmosis desalination plant were modeled for a specific site in southern Tunisia using real meteorological and water consumption data for 1 year. A total of 8760 simulations were treated under a dynamic simulator coupled to a smart energy management strategy to reach the hourly water load demand. Although the recognized reliability of the hybrid renewable sources compared to one- power source, their design may still critical. Therefore, in this paper, the authors suggest applying the methodology of optimizing the presented unit using an integrated systemic meta-modeling which is built through the design of experiments tool and defined by an equation involving the decision variables of the optimization as its parameters. This equation outlines the objects of the optimum sizing. The selected optimal design of the proposed unit is predicted by the genetic algorithm NSGA-II based on minimizing two objectives in conflict: Embodied energy and hydraulic loss of power supply. The CPU time of the NSGA-II optimization via the meta-model reached only 15 minutes of treatment (with one day to build the design of experiments) compared to the classic optimization via dynamic simulation. The results of the optimum sizing show that it is possible to consider a low water shortage rate (0% ⩽ LPSP-H < 5%) for a marginal variation of embodied energy rate which does not exceed (7%).