Seawater Reverse Osmosis Desalination Research Articles

Reverse Electrodialysis: Potential Reduction in Energy and Emissions of Desalination

Salinity gradient energy harvesting by reverse electrodialysis (RED) is a promising renewable source to decarbonize desalination. This work surveys the potential reduction in energy consumption and carbon emissions gained from RED integration in 20 medium-to-large-sized seawater reverse osmosis (SWRO) desalination plants spread worldwide. Using the validated RED system’s model from our research group, we quantified the grid mix share of the SWRO plant’s total energy demand and total emissions RED would abate (i) in its current state of development and (ii) if captured all salinity gradient exergy (SGE). Results indicate that more saline and warmer SWRO brines enhance RED’s net power density, yet source availability may restrain specific energy supply. If all SGE were harnessed, RED could supply ~40% of total desalination plants’ energy demand almost in all locations, yet energy conversion irreversibility and untapped SGE decline it to ~10%. RED integration in the most emission-intensive SWRO plants could relieve up to 1.95 kg CO2-eq m−3. Findings reveal that RED energy recovery from SWRO concentrate effluents could bring desalination sector sizeable energy and emissions savings provided future advancements bring RED technology closer to its thermodynamic limit.

Redox condition of saline groundwater from coastal aquifers influences reverse osmosis desalination process

Reverse osmosis (RO) seawater desalination is a widely applied technological process to supply potable water worldwide. Recently, saline groundwater (SGW) pumped from beach wells in coastal aquifers that penetrate beneath the freshwater-seawater interface is considered as a better alternative water source to RO seawater desalination as it is naturally filtered within the sediments which reduces membrane fouling and pre-treatment costs. The SGW of many coastal aquifers is anoxic – and thus, in a low redox stage – has elevated concentrations of dissolved manganese, iron and sulfides. We studied the influence of the SGW redox stage and chemistry on the performance - permeate flux and fouling properties - of RO desalination process. SGWs from three different coastal aquifers were sampled and characterized chemically, and RO desalination experiments were performed under inert and oxidized conditions. Our results show that all three aquifers have anoxic saline groundwater and two of them have intensive anaerobic oxidation of organic matter. Two aquifers were found to be in the denitrification stage or slightly lower and the third one in the sulfate reduction stage. Our results indicate that the natural redox stage of SGWs from coastal aquifers affects the performance of RO desalination. All SGW types showed better RO performance over seawater desalination. Furthermore, air oxidation of the SGW was accompanied with pH elevation, which increased the membrane fouling. Hence, keeping the feed water unexposed to atmospheric conditions for maintaining the natural reducing stage of the SGW is crucial for low fouling potential. The observed benefits of using naturally reduced SGW in RO desalination have significant implications for reduction in overall process costs.

Role of dissolved air flotation (DAF) and liquid ferrate on mitigation of algal organic matter (AOM) during algal bloom events in RO desalination

Harmful Algal Blooms (HABs) are considered a major contributor to membrane biofouling in Seawater Reverse Osmosis (SWRO) desalination plants. The presence of HABs in the raw feed water leads to an increase in membrane fouling rate, increase of chemical consumption, and can cause temporary shutdown of plants. Effective pretreatment can reduce the amount of organic foulants reaching the RO membrane and alleviate the problem of flux decline during RO operation and frequent membrane cleaning using chemicals. This study compared the effect of in-situ generated liquid ferrate and ferric chloride in combination with dissolved air flotation (DAF) as a pretreatment strategy to remove algal cells and algal organic matter (AOM) during algal bloom events. Experiments were performed using a bench-scale DAF unit. HABs conditions were simulated by harvesting AOM from cultivating Chaetoceros affinis (CA) in raw seawater to a concentration of around 10 mg C/L of dissolved organic carbon (DOC). The liquid ferrate was generated in-situ by wet oxidation of ferric chloride in an alkaline media. The best performance was achieved with the combined use of liquid ferrate and DAF, removing up to 100% of algal cells, 99.99% of adenosine tri-phosphate (ATP), and up to 92% of AOM.

Evaluation of environmental indicators of RO seawater desalination: case study coastal strip of Hormozgan province, Iran

Abstract In recent years, desalination has been turned into a fresh water supply as a solution in some areas which suffer from water shortage. Desalinated water as an industrial product causes environmental problems. The objectives of this study are investigating environmental sustainability indicators related to seawater desalination via reverse osmosis (SWRO) on the coastline of Hormozgan province to provide a better insight for current and future water and energy demands related to this alternative. The selected indicators are specific energy consumption, seawater withdrawal, and brine volume in desalination, fuel consumption, carbon emission and water withdrawal in electric power generation. Using a solution-diffusion model, the direct indicator of energy consumption was obtained as used to calculate indirect indicators from the energy generation sector. Analysis of results indicates that desalination can lead to out-of-area side effects resulting from fuel type consumed and the practical power of the power plant, in addition to the regional environmental effects that are mostly affected by total dissolved solids of feed water. Based on the results, the environmental issues should be considered for the regions where desalination was planned as the most feasible alternative for water supply. This result can help policymakers to manage water supply and demand for sustainable development appropriately.

Fault Detection and Isolation System Based on Structural Analysis of an Industrial Seawater Reverse Osmosis Desalination Plant

Currently, the use of industrial seawater reverse osmosis desalination (ISROD) plants has increased in popularity in light of the growing global demand for freshwater. In ISROD plants, any fault in the components of their control systems can lead to a plant malfunction, and this condition can originate safety risks, energy waste, as well as affect the quality of freshwater. This paper addresses the design of a fault detection and isolation (FDI) system based on a structural analysis approach for an ISROD plant located in Lima (Peru). Structural analysis allows obtaining a plant model, which is useful to generate diagnostic tests. Here, diagnostic tests via fault-driven minimal structurally overdetermined (FMSO) sets are computed, and then, binary integer linear programming (BILP) is used to select the FMSO sets that guarantee isolation. Simulations shows that all the faults of interest (sensors and actuators faults) are detected and isolated according to the proposed design.

Recovery of salinity gradient energy in desalination plants by reverse electrodialysis

Salinity gradient energy (SGE) capture by reverse electrodialysis (RED) is an emerging technology to advance the phaseout of conventional water-intensive energy sources in desalination industry. This paper assesses SGE recovery potential of an up-scaled RED system in seawater reverse osmosis (SWRO) desalination plants. Using a detailed RED system's model (i) we conducted a parametric evaluation of feed's concentration, feed's flow rate, and temperature to identify the optimal working conditions of an industrial-scale RED unit; (ii) we estimated SGE recovery of a RED plant in SWRO plants distributed worldwide, adopting a single-stage arrangement of the RED units; (iii) finally, to enhance energy yield, we examined different RED plant's layouts in a specific SWRO plant. The results underline the merits of this modelling tool to assist SGE-RED implementation in the utmost scenarios. Regarding RED plant's layout, findings reveal that the series-parallel arrangement of the RED units improves the power output and energy yield of the system but requires more RED units. Hence, a systematic evaluation through optimization of the hybrid process's configuration both at plant's scale and at RED unit's scale is needed to properly determine RED's SGE recovery potential from waste streams in SWRO plants.

Preliminary design of a hydraulic wind turbine drive train for integrated electricity production and seawater desalination

The integration of wind energy to desalinate seawater can address the freshwater scarcity issue and alleviate the environmental impact of desalination. This paper presents the use of the Delft Offshore Turbine, an unconventional wind turbine with hydraulic transmission which can be used to directly drive a seawater reverse osmosis desalination process and to produce electricity with a Pelton turbine. A steady-state model is used to identify the potential regions at which it is possible to operate the system and to propose a system settings for maximising water production. The results show that the proposed system provides up to 300 kW of electricity and can desalinate up to 25 m3/h, at rated operating conditions.

A Small RO and MCDI Coupled Seawater Desalination Plant and Its Performance Simulation Analysis and Optimization

To solve the problems of high specific energy consumption and excessive harmful ions in the water production of a small reverse osmosis (RO) plant, a desalination system coupling RO and membrane capacitive deionization (MCDI) is proposed in this study. Aiming at producing two cubic meters per day of fresh water with a salt concentration of less than 280 mg L−1, parameter matching optimization was carried out on two desalination system schemes of one-stage two-section RO and one-stage three-section RO coupled with MCDI. The results were compared with the parameter matching optimization results of the one-stage one-section RO and the one-stage two-section pure RO desalination system. The results show that compared with the pure RO desalination mode, the seawater desalination mode coupled with RO and MCDI reduces the specific energy consumption under the same effluent salt concentration. Moreover, it decreases the feed water pressure in front of the RO membrane, which can reduce the standard of high-pressure pump in a small seawater desalination plant. The energy consumption of the one-stage three-section RO and MCDI coupling system is lower than that of the one- stage two-section RO and MCDI coupling system, and the feed water pressure is also lower.

Modeling, design, and optimization of a cost‐effective and reliable hybrid renewable energy system integrated with desalination using the division algorithm

People in the Middle East are facing the problem of freshwater shortages. This problem is more intense for a remote region, which has no access to the power grid. The use of seawater desalination technology integrated with the generated energy unit by renewable energy sources could help overcome this problem. In this study, we refer a seawater reverse osmosis desalination (SWROD) plant with a capacity of 1.5 m3/h used on Larak Island, Iran. Moreover, for producing fresh water and meet the load demand of the SWROD plant, three different stand-alone hybrid renewable energy systems (SAHRES), namely wind turbine (WT)/photovoltaic (PV)/battery bank storage (BBS), PV/BBS, and WT/BBS are modeled and investigated. The optimization problem was coded in MATLAB software. Furthermore, the optimized results were obtained by the division algorithm (DA). The DA has been developed to solve the sizing problem of three SAHRES configurations by considering the object function's constraints. These results show that this improved algorithm has been simpler, more precise, faster, and more flexible than a genetic algorithm (GA) in solving problems. Moreover, the minimum total life cycle cost (TLCC = 243 763$), with minimum loss of power supply probability (LPSP = 0%) and maximum reliability, was related to the WT/PV/BBS configuration. WT/PV/BBS is also the best configuration to use less battery as a backup unit (69 units). The batteries in this configuration have a longer life cycle (maximum average of annual battery charge level) than two other configurations (93.86%). Moreover, the optimized results have shown that utilizing the configuration of WT/PV/BBS could lead to attaining a cost-effective and green (without environmental pollution) SAHRES, with high reliability for remote areas, with appropriate potential of wind and solar irradiance.

Life cycle cost of dilution desalination in off-grid locations: A study of water reuse integrated with seawater desalination technology

Seawater reverse osmosis (SWRO) desalination is a proven technology for augmenting water supply in remote areas with limited access to fresh water resources. Lowering the energy consumption of SWRO is crucial in such areas where the source of energy is often reliant on transported liquid fuels. This study presents a life cycle cost model for two diluted desalination processes using water reuse to dilute seawater, and reduce energy consumption. The economic model details the life cycle capital and operational costs of i) a baseline SWRO desalination, ii) alternative osmotic dilution desalination in a forward osmosis (FO)–reverse osmosis (RO) hybrid system, and iii) a mixed dilution desalination process in an ultrafiltration (UF)–RO system. The results reveal a 4–5% lower total water cost associated with the two alternative processes compared to conventional SWRO. Sensitivity analysis revealed that the FO–RO system is an economically viable alternative to standalone RO if a water flux ≥6 L·m−2 h−1 and a recovery rate >25% can be achieved. The sensitivity analysis showed that diluted desalination with UF–RO was economically preferable to SWRO even when the water flux and recovery rate of UF meet only minimum thresholds (18 L·m−2 h−1 and 55%, respectively).

Forward osmosis and pressure retarded osmosis process modeling for integration with seawater reverse osmosis desalination

Osmotically driven membrane processes such as forward osmosis and pressure retarded osmosis may hold key advantages when integrated with seawater reverse osmosis to form hybrid FO-RO and RO-PRO systems. In this work, module-scale modeling of these two processes was improved by accurately representing the features of a spiral-wound membrane. The model captures important characteristics such as the cross-flow stream orientation, membrane baffling, and channel dimensions unique to spiral-wound membranes. The new module-scale model was then scaled to the system-level to compare various system designs for FO-RO and RO-PRO systems, most notably, a multi-stage recharge design was defined. Results indicate that the multi-stage recharge design leads to an increase in wastewater utilization, as high as 90%, when compared to the single-stage designs. Additionally, the multi-stage recharge configuration can increase the specific energy recovery of pressure retarded osmosis by over 75%. The multi-stage recharge design is found to be not only advantageous but may be also necessary to the integration of osmotically driven membrane processes with seawater reverse osmosis.

Fouling investigation of a full-scale seawater reverse osmosis desalination (SWRO) plant on the Red Sea: Membrane autopsy and pretreatment efficiency

In this study, the membrane autopsy was performed on a full-scale seawater reverse osmosis (SWRO) desalination plant located on the Red Sea. Several techniques were employed to characterize the nature and the fate of the foulants in the process, including LCOCD, ICP-MS, SEM-EDS, TSS, and ATP. The efficiency of the pretreatment in removing the fouling potential was assessed by analyzing the seawater after the intake feed pump, after the spruce media filter (SMF) and after the cartridge filter (CF). The autopsy of the membrane modules and CF operated for long-term revealed the presence of a heterogeneous fouling layer. The organic fraction composition of the fouling layer depended on the module position in the vessel. The inorganic deposits embedded in the layer were mainly composed of aluminum, iron, and magnesium silicate. The inorganic sediments entered the plants from the shoreline seawater intake and accumulated on the CF filter and the membrane. The analysis of the pretreatment performance showed an increase of TSS and ATP after CF, highlighting the inappropriate CF filter replacement time.

Influences and impacts of biofouling in SWRO desalination plants

The ability to produce fresh potable water is an ever-growing challenge, especially with an increase in drought conditions worldwide. Due to its capacity to treat different types of water, reverse osmosis (RO) technology is an increasingly popular solution to the water shortage problem. The major restriction associated with the treatment of water by RO technology is the fouling of the RO membrane, in particular through biofouling. Membrane fouling is a multifaceted problem that causes an increase in operating pressure, frequent cleaning and limited membrane lifespan. The current paper summarizes the impact of biofouling of RO membranes used in seawater desalination plants. Following a brief introduction, the elements that contribute to biofouling are discussed: biofilm formation, role of extracellular polymeric substances (EPS), marine environment, developmental phases of biofouling. Following this, is a section on the implications of membrane biofouling especially permeate flux and salt rejection. The final section focuses on the new phenomenon of compression and hydraulic resistance of biofilms. Lastly, considerations on future research requirements on biofouling and its control in seawater reverse osmosis (SWRO) membrane systems are presented at the end of the article.

Improving energy efficiency of pretreatment for seawater desalination during algal blooms using a novel meshed tube filtration process

A new meshed tube filtration (MTF) process was developed and assessed as a low energy-consuming pretreatment process that withstands algal blooms (i.e., red tide). This process can potentially replace the dissolved air flotation (DAF) process in typical seawater reverse osmosis (SWRO) desalination plants. Two marine microalgae species, namely C. polykrikoides and T. suecica, were first cultivated and then utilized to simulate algal bloom conditions in the lab-scale filtration experiments. The algal matter was coagulated and circulated by aeration in the MTF system that was filled with cylindrical polypropylene meshed tubes with ciliary ends and had the ability to capture coagulated algae in an effective manner. The efficiency of the MTF process to remove algal cells was significantly enhanced by optimizing the coagulant dose and the aeration rate. In order to further verify the MTF performance, DAF experiments were conducted, under similar conditions, for the comparison of algal removal effectiveness and energy consumption rates. The results showed high removal rates of algal cells as well as turbidity for MTF, although only a limited reduction of algal organic matter (AOM) was observed. When DAF was operated at energy consumption levels equivalent to MTF, its algae removal rate was lower than that of MTF. Furthermore, under optimal operating conditions, MTF consumed approximately one-third of the energy needed for DAF operation, mainly due to the fact that MTF requires less aeration. For future improvements in the AOM removal process, an energy-efficient pretreatment process could be realized for SWRO desalination facilities facing potential algal blooms.

Energy Recovery in SWRO Desalination: Current Status and New Possibilities

Reverse osmosis (RO) technology requires high energy input in order to extract freshwater from seawater. Improvements in RO technology have led to seawater RO (SWRO) becoming the dominant form of large scale desalination around the world. However, the specific energy consumption (SEC) of SWRO remains substantially higher than that for surface water treatment and indirect potable recycling, making SWRO less cost effective than other alternatives for producing potable water. Furthermore, where non-renewable energy sources are used to supply SWRO energy demand, higher levels of greenhouse gas are emitted compared with lower energy alternatives. The purpose of this paper is to review the RO process configurations currently available and their impact on reducing SWRO energy consumption. This paper highlights the main factors contributing to SWRO energy consumption and presents some of the commonly adopted approaches to reducing SEC in SWRO plants. The use of energy recovery devices (ERDs) in SWRO is explored and the relative effectiveness of the various types of ERDs in reducing SEC presented.

The effect of energy recovery device and feed flow rate on the energy efficiency of reverse osmosis process

The energy requirements for reverse osmosis (RO) seawater desalination continue to be a major matter of debate. Previous studies have shown the dependence of optimum RO desalination energy on the RO recovery rate. However, they overlooked including the effect of Energy Recovery Device (ERD) and pretreatment on the power consumption. In this work, a computer model was used to analyze the energy requirements for RO desalination, taking into account the effect of ERD efficiencies and pretreatment. The specific power consumption (SPC) of the RO was found to increase with the increase of RO recovery rate when the ERD system was included. The optimum SPC became more dependent on the RO recovery rate when the pretreatment energy was added. The recovery for optimum desalination energy was 46%, 44%, and 40% for the RO system coupled with an ERD of 65%, 80%, and 95% efficiency, respectively. The results showed that RO process could be operated at lower recovery rate and still meet the projected desalination capacity by increasing the feed flow rate and coupling with high-efficiency ERD. A trivial decrease of the total desalination energy was achieved when the feed flow rate increased from 7m3/h to 8m3/h and recovery rate decreased from 46% to 44% by coupling the RO with an ERD of 95% efficiency. This suggests that the RO–ERD system can be operated at a high feed flow rate and low recovery rate without affecting the plant capacity.

A Novel RO/FO Hybrid Seawater Desalination System and Its Software Implementation

Seawater reverse osmosis (SWRO) desalination technology is being widely used in coastal countries to meet the supply demand of fresh water for living and industry using. Despite major advancements in SWRO technology, the desalination industry is still facing significant practical issues. Generation of higher volumes of pretreatment sludge and low overall water recovery are the two of the major issues. A novel hybrid reverse osmosis-forward osmosis (RO/FO) system is proposed to overcome the above two drawbacks. Mass balance calculations based on laboratory experiments have been used to predict increased water recovery and reduced pretreatment sludge volume arising from large scale (340,000 m3/day of intake) and small scale (15,000 m3/day of intake) hybrid SWRO desalination plants. After that, we developed a software for the RO/FO hybrid system in MATLAB, and different water flux values were studied to verify the system. It was packaged into executable files and it can run smoothly on computers without MATLAB installed. By setting different operating parameters in the RO/FO system software interface, the percentage reduction of pretreatment sludge volume, increase in overall RO water recovery, FO membrane area required and dilution in RO reject can be estimated quickly in a variety of different options.

Hydraulic turbocharger for energy recycling in the reverse osmosis seawater desalination system

In order to reduce the energy consumption of the reverse osmosis seawater desalination process, a hydraulic turbocharger is proposed to recycle the pressure energy of the brine. A high efficiency energy recovery hydraulic turbocharger is designed based on Computational Fluid Dynamic method and installed in the reverse osmosis seawater desalination system of Dagang Power Plant in Tianjin Development Zone, China. The actual operation results show that the hydraulic turbocharger has apressure energy recovery efficiency of up to 72%, and with high working stability and low noise, which may provide areliable reference for the design and application of pressure energy recovery devices.

Towards sustainable development in the MENA region: Analysing the feasibility of a 100% renewable electricity system in 2030

This research explores the feasibility of 100% renewable energy (RE) systems for the Middle East and North Africa (MENA) region for assumptions of the year 2030. The demand for three sectors are taken into account: power, non-energetic industrial gas and seawater desalination. Three strategical scenarios are discussed, namely Region, Area and Integrated, mainly differing in level of regional grid interconnection and sector coupling. Solar photovoltaics (PV) and wind energy are found to be the most cost-competitive RE sources with the highest potential in the region covering more than 90% of the generation capacity in all the considered scenarios. The variability of RE is solved via energy storage, surplus electricity generation and electricity grids. The estimated overall levelised cost of electricity (LCOE) lies between 40.3 and 52.8 €/MWh, depending on the scenarios. The total LCOE decreased by 17% as a result of sector coupling compared to the interconnected power sector alone. Power-to-gas technology not only functions as a seasonal storage by storing surplus electricity produced mainly from wind power and partially from solar PV, but provides also the required gas for the non-energetic industrial gas sector. Battery storage complements solar PV as a diurnal storage to meet the electricity demand during the evening and night time. Seawater reverse osmosis desalination powered by renewables could potentially be a proper solution to overcome the water challenges in the MENA region at affordable cost of 1.4 €/m3. A comparison with a BAU strategy shows that a 100% renewable energy-based power system is 55–69% cheaper than a BAU strategy without and with greenhouse gas emission costs.

Nanoclays‐Incorporated Thin‐Film Nanocomposite Membranes for Reverse Osmosis Desalination

AbstractA series of thin‐film nanocomposite (TFN) membranes with incorporation of Laponite nanoclays (NC‐LAP) is prepared and demonstrated for brackish water and seawater desalination. It is the first attempt to use poly(ethylene glycol) 200 (PEG200) assisted Laponite as nanofillers to improve the performance of TFN membranes for reverse osmosis (RO) seawater desalination. The influence of NC‐LAP loading and PEG200 as the dispersant on membrane properties is investigated. An increase in NC‐LAP loading results in an increase in water permeability without sacrificing the salt rejection. At the loading of 0.3 wt%, the TFN membrane shows a water permeability of 2.7 L m−2 h−1 bar−1 (LMH bar−1) and a salt rejection of 98.18% for brackish water desalination at 20 bar and 25 ± 1 °C. This water permeability is 53% higher than the conventional thin‐film composite (TFC) membrane. A steady water flux above 35 LMH is obtained when using seawater as the feed at 50 bar and 25 ± 1 °C. The existence of PEG200 to effectively disperse NC‐LAP nanoparticles is essential to fabricate the NC‐LAP incorporated TFN membranes for brackish water and seawater desalination.