Seawater Reverse Osmosis Desalination Research Articles

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.

Performance fluctuations and evaluation of a piston type integrated high pressure pump-energy recovery device

The development of energy recovery device (ERD) is a decisive factor for the recent prevalence of reverse osmosis (RO) technology in the seawater desalination field. Unlike broadly studied large scale ERDs, the investigations of small scale ERDs are scarcely reported, especially on the performance fluctuations under variable operating conditions. Based on an authors’ exploratory research on a piston type integrated high pressure pump-energy recovery device (HPP-ERD), further performance exploitation of the HPP-ERD is conducted. With a constructed experiment platform, the influences of inlet seawater temperature, inlet seawater salinity, as well as the operating frequency on the performance of the HPP-ERD coupled with seawater reverse osmosis (SWRO) desalination system are investigated. The temperature and salinity of the inlet seawater are numerically correlated with the specific energy consumption (SEC) of the HPP-ERD. With the correlated equation, the marine hydrological data of two observatories acquired from a national authoritative database, and the annualized life cycle cost approach incorporated, annual performance assessment is proposed for an SWRO desalination system equipped with the HPP-ERD in the light of energy and economic indices. The study results indicate that the proposed HPP-ERD is competent under various operating conditions for SWRO desalination systems.

Advanced coagulation with liquid ferrate as SWRO desalination pretreatment during severe algal bloom. Process performance, environmental impact, and cost analysis

Harmful algal bloom (HABs) events represent a major operational challenge for seawater reverse osmosis (SWRO) desalination plants, leading to severe membrane fouling, increased chemical consumption and plant shutdowns. Current pretreatment practice applying conventional coagulation, flocculation, and sedimentation (CFS) with ferric chloride has shown limited capability in reducing seawater fouling potential during HABs events. The use of in-situ generated liquid ferrate (Fe(VI)) has recently been proposed for CFS pretreatment due to its capability of acting simultaneously as a coagulant, oxidant, and disinfectant. In this study, the use of ferric chloride (conventional coagulation) was compared to liquid ferrate (advanced coagulation) during HABs events, in terms of process performance, life-cycle assessment (LCA) and cost analysis. Results show that a 10 times lower concentration of Fe salt was required in advanced coagulation compared to conventional coagulation to achieve a similar performance in terms of turbidity and TOC removal. Using liquid ferrate also resulted in a higher total ATP removal (>99%) and lower dissolved Fe concentration. The advanced coagulation reduced dry sludge production by 88%, resulting in a significant decrease in environmental impacts and operational costs.

Modeling and Structural Optimization of MSF-RO Desalination System.

Based on the mathematical modeling and operational optimization studies of reverse osmosis (RO) and multistage flash (MSF) desalination, the structural optimization of the hybrid process was specially studied in this work with the consideration of reducing comprehensive expenses under given operational conditions. Firstly, according to the process mechanism and flowchart of the RO and MSF seawater desalination technologies, seven hybrid structures with different feed conditions were designed, and their connection equations were established for numerical calculation. Then, in order to evaluate the economic performance of the hybrid systems with different structures, the hourly average operational cost equations of RO and MSF processes were established and formulated as the comprehensive evaluation indicators. Next, with a given water production requirement, simulation calculations of the hybrid system with seven different structures were performed. The results show that the hybrid system with the fourth structure has the lowest operational cost of 4.6834 CNY/m3, and at the same time it has the lowest blowdown. However, if we take GOR or production water temperature as the target, the optimal structure of the hybrid system is the fifth or the seventh option. The obtained results are helpful in structural optimization of the hybrid system with aspects of operational cost reduction, maximum GOR, or minimizing the wastewater discharge.

Ultraviolet light-activated peroxymonosulfate (UV/PMS) system for humic acid mineralization: Effects of ionic matrix and feasible application in seawater reverse osmosis desalination

The use of membrane-based technology has evolved into an important strategy for supplying freshwater from seawater and wastewater to overcome the problems of water scarcity around the world. However, the presence of natural organic matter (NOM), including humic substances affects the performance of the process. Here, we present a systematic report on the mineralization of humic acid (HA), as a model for NOM, in high concentration of salts using the ultraviolet light-activated peroxymonosulfate (UV/PMS) system as a potential alternative for HA elimination during membrane-based seawater desalination and water treatment processes. Effects of various parameters such as PMS concentration, solution type, pH, anions, and anion-cation matrix on HA mineralization were assessed. The results show that 100%, 78% and 58% of HA (2 mg/L TOC) were mineralized with rate constants of 0.085 min−1, 0.0073 min−1, and 0.0041 min−1 after 180 min reaction time at pH 7 when 0.5 mM PMS was used in deionized water, sodium chloride solution (35,000 ppm) and synthetic seawater, respectively. The reduced efficiency under saline conditions was attributed to the presence of anions in the system that acted as sulfate and hydroxyl radicals’ scavengers. Furthermore, the safety of the treated synthetic seawater was evaluated by analyzing the residual transformed products. Overall, pretreatment with the UV/PMS system mitigated fouling on the RO membrane.

Energy utilisation strategy in an offshore floating wind system with variable production of fresh water and hybrid energy storage

ABSTRACT Renewable energy sources increase their share in the energy mix and, therefore it is important to accommodate variability in energy production. In this study, a hybrid approach is evaluated where a combination of batteries and compressed air are used together with seawater reverse osmosis in order to match renewable energy against electricity and water needs. Especially in remote islands renewable energy-powered desalination is an attractive option. These technologies are tested on a semi-submersible floating platform, accommodating an offshore wind turbine, a photovoltaic system and a reverse osmosis seawater desalination. The floating offshore system can deliver both fresh water and electricity in a dynamic configuration. Simulations of different operating strategies have been examined and show that sustainable solutions can be achieved.

Renewable Energy-Driven Desalination: New Trends and Future Prospects of Small Capacity Systems

New trends and future prospects for small capacity systems of Renewable Energy-driven DESalination (REDES) are reviewed and assessed in this paper over a nominal desalination capacity range of 3–1000 m3/d. A thorough literature review is reported in order to evaluate current research and developing activities. Outstanding commercial prospects in the near future are identified for two off-grid REDES technologies under development. First, wave energy converters with direct coupling to seawater desalination. Second, solar micro gas turbines with biofuel backup coupled to reverse osmosis (RO) desalination and/or zero liquid discharge water treatment. These systems, as well as mature REDES plants (namely PV/RO and wind turbines/RO), will benefit from forthcoming advances in energy efficiency in the RO process itself. The Closed Circuit RO desalination (CCROTM) concept may be a key configuration for enhancing RE-driven RO desalination. Additionally, opportunities for innovation in seawater RO desalination with variable power consumption are highlighted. On the other hand, our conclusions highlight opportunities for developing novel portable REDES systems based on solar membrane distillation with a portable linear Fresnel concentrator manufactured by SOLATOM. Additionally, the concept of portable systems could foster the commercial development of microbial desalination cells combined with solar PV energy and RO powered by tidal currents.

Biodegradability of antiscalants used in seawater reverse osmosis desalination and their effect on microbial diversity - Suppl. Material

Biodegradability of antiscalants used in seawater reverse osmosis desalination and their effect on microbial diversity - Suppl. Material

Can Aggregate-Associated Organisms Influence the Fouling in a SWRO Desalination Plant?

This pilot study investigates the formation of aggregates within a desalination plant, before and after pre-treatment, as well as their potential impact on fouling. The objective is to provide an understanding of the biofouling potential of the feed water within a seawater reverse osmosis (SWRO) desalination plant, due to the limited removal of fouling precursors. The 16S and 18S rRNA was extracted from the water samples, and the aggregates and sequenced. Pre-treatment systems, within the plant remove < 5 µm precursors and organisms; however, smaller size particles progress through the plant, allowing for the formation of aggregates. These become hot spots for microbes, due to their nutrient gradients, facilitating the formation of niche environments, supporting the proliferation of those organisms. Aggregate-associated organisms are consistent with those identified on fouled SWRO membranes. This study examines, for the first time, the factors supporting the formation of aggregates within a desalination system, as well as their microbial communities and biofouling potential.

Exploring energy-saving potentials in seawater desalination engineering from the energy-water nexus perspective

With the rapid population growth and economic development, the necessity to explore energy-saving potentials in typical seawater desalination project is increasingly essential. Taking the Reverse Osmosis (RO) seawater desalination project in Hebei Province, China as a case, this study performed systematic accounting framework combining the direct and indirect energy consumption from the energy-water nexus perspective, and carried out the energy-saving potential assessment and systematical optimization configuration. From the results, the total direct energy consumption of the project was 2.23 × 106 kWh, and the total embodied energy consumption was 2.18 × 107 kWh. Define the embodied energy consumption (ESE) as an evaluation index of energy saving potentials, the energy consumption degree before optimization is 79.54%, which could be reduced to 26.30% after optimization. The results showed that the systematic accounting framework in this study can greatly improve the accuracy of energy consumption measurement in the project, and the systematical optimization configuration can significantly reduce energy consumption and improve the energy-saving design under the minimum investment in the seawater desalination projects.

Can Large-Scale Offshore Membrane Desalination Cost-Effectively and Ecologically Address Water Scarcity in the Middle East?

The Middle East will face tremendous water scarcity by 2050, which can only be mitigated by large-scale reverse osmosis seawater desalination. However, the coastal land in the region is rare and costly, so outsourcing the desalination facility to artificial islands could become a realistic scenario. This study investigated the ecological and economic challenges and possible advantages of that water supply option by analysing conceptual alternatives for offshore membrane-based desalination plants of up to 600 MCM/y capacity. Key environmental impacts and mitigation strategies were identified, and a detailed economic analysis was conducted to compare the new approach to state-of-the-art. The economic analysis included calculating the cost of water production (WPC) and discussing the differences between offshore alternatives and a conventional onshore desalination plant. In addition, the study investigated the impact of a changing energy mix and potential carbon tax levels on the WPC until 2050. The results indicate that offshore desalination plants have ecological advantages compared to onshore desalination plants. Furthermore, the construction cost for the artificial islands has a much lower effect on the WPC than energy cost. In contrast, the impact of potential carbon tax levels on the WPC is significant. The specific construction cost ranges between 287 $/m2 and 1507 $/m2 depending on the artificial island type and distance to the shoreline, resulting in a WPC between 0.51 $/m3 and 0.59 $/m3. This work is the first to discuss the environmental and economic effects of locating large-scale seawater desalination plants on artificial islands.

Desalination using pressure or electric field? A fundamental comparison of RO and electrodialysis

Reverse osmosis (RO) is the dominant desalination technology today since it is the most economical. Electrodialysis (ED) is a competing technology that removes ionic solutes using an applied electric field. An analogy is derived between the flux of water in RO (pressure-driven) and salt in ED (in the form of an electric current), which helps define appropriate conversion factors for direct comparison between equivalent terms, e.g., electrical conductivity of ED and permeability of RO. Optimized batch and single-stage configurations of both technologies are considered for cross-comparison. The ratio of specific costs (per unit system area) of ED and RO to achieve similar overall cost of pure water is inversely proportional to the feed salinity squared, resulting in ED's relative advantage for lower-salinity/brackish-water desalination. This study provides a guideline on the competitiveness of ED for various desalination applications as a function of technology (membrane, channel resistance) and commercial (cost, plant life, interest rate) factors. For example, to outperform RO for seawater desalination, the amortized cost of ED or the overall cell pair resistance has to be reduced by a factor of around 20 relative to values reported in the literature.

Jellyfish swarm impair the pretreatment efficiency and membrane performance of seawater reverse osmosis desalination

Circumstantial evidence has suggested that jellyfish swarms impair the operation of seawater reverse osmosis desalination facilities. However, only limited information is currently available on the pretreatment efficiency of jellyfish and their effects on reverse osmosis (RO) membrane performance. Here, we have comprehensively tested the pretreatment efficiency of a dual-media gravity filter and cartridge micro-filtration following the addition of jellyfish into the feedwater. Concurrently, the fouling propensity and performance of the RO membranes were examined. We show that jellyfish demise resulted in seawater eutrophication that triggered a significant increase in bacterial biomass (∼50-fold), activity (∼7-fold), and release of transparent exopolymer particles (∼5-fold), peaking three days after the addition of jellyfish into the feedwater. In parallel, a significant reduction in permeate water flux was recorded (∼10%) while trans-membrane pressure sharply increased (15%), reaching the operation pressure limit of our system (75 bar) after five days. At the conclusion of the experiments, the membrane surface was heavily covered by large chunks of organic-rich material and multilayered biofilms. Our results provide a holistic view on the operational challenges of seawater reverse osmosis (SWRO) desalination triggered by jellyfish swarms in coastal areas. Following the above, it can be inferred that freshwater production will likely be halted three days after drawing the jellyfish into the pretreatment system. Outcomes from these results may lead to the development of science-based operational protocols to cope with growing occurrence of jellyfish swarms around the intake of SWRO desalination facilities worldwide.

Field-enhanced water transport in sub-nanometer graphene nanopores

It is greatly important to improve water transport efficiency while maintaining strong salt rejection for nanoporous graphene membranes used in reverse osmosis seawater desalination. In this work, molecular dynamics simulations were applied to investigate water transport through sub-1 nm diameter graphene nanopores with different geometries under external electric fields. It was found that water concentration inside the nanopore with armchair edges increases with the electric field intensity. From analysis in micro-characteristics, water molecules become more structured and polarized near the nanopore armchair edges with a higher electric field intensity, indicated by the narrower distribution of water orientation, the longer water residence time and more hydrogen bonds per water molecule. With a specially designed armchair-edged graphene nanopore, the efficiency in reverse osmosis desalination was explored under external electric fields. Significantly enhanced water permeability was obtained that ~40 times higher than the existing desalination membranes while still remaining a complete salt rejection due to the accumulation of water and its improved transport velocity inside the nanopore.

Thermodynamics, isotherms, and mechanisms studies of lithium recovery from seawater desalination reverse osmosis brine using roasted and ferrocyanide modified date pits

In this study, the adsorption isotherms and thermodynamic studies of lithium ions from seawater reverse osmosis (SWRO) desalination brine were investigated. Three adsorbents were utilized namely, roasted date pits (RDP), potassium copper, and nickel hexacyanoferrate-date pits (RDP-FC-Cu and RDP-FC-Ni). The prepared adsorbents showed enhanced morphological and chemical structures such as high porosity, carbonaceous composition, larger pore and volume sizes, smaller particle sizes as well as the presence of unique functional groups on their surface. The adsorption of lithium ions onto the three adsorbents was enhanced with an increase in solution temperature and initial lithium concentration. The temperature that showed the highest adsorption of lithium ions onto the three adsorbents was 45 °C. The adsorption of lithium ions onto the three adsorbents was the highest at an initial lithium concentration of 100 mg/L. The three adsorbents achieved an adsorption capacity of around 99 mg/g at the optimum temperature and initial concentration. On the other hand, RDP-FC-Cu achieved the highest adsorption capacities for lithium ions at all the studied initial concentrations. The thermodynamic study showed that the adsorption process of lithium ions onto the adsorbents is endothermic, spontaneous, and favorable at all the studied temperatures (25 °C, 35 °C, and 45 °C). Moreover, the adsorption of lithium ions onto the three adsorbents followed the Langmuir, Freundlich, Dubinin–Radushkevich, and Temkin adsorption isotherm models differently at each studied temperature. For RDP, the adsorption process followed the Freundlich adsorption isotherm model at 25 °C, while it was more fitted to the Langmuir isotherm model at 45 °C and all models at 35 °C. The adsorption of lithium ions onto RDP-FC-Cu followed Langmuir adsorption isotherm model at 25 °C and 35 °C, while it fitted all models at 45 °C. On the other hand, Langmuir and Dubinin–Radushkevich isotherm models were best fit for the adsorption of lithium ions onto RDP-FC-Ni at 25 °C and 35 °C. The desorption study presented 99% desorption percentages of lithium ions from all the adsorbents, which showed the great regeneration potential of the adsorbents. Furthermore, the selectivity study showed that RDP-FC-Cu achieved 99.9% adsorption removal of lithium ions from the SWRO brine while RDP-FC-Ni and RDP achieved 99.8% and 99.3% adsorption removals, respectively. Finally, the cost analysis revealed that the total cost for the preparation of the adsorbent was 29.81 USD. • Three adsorbents were prepared to study the adsorption thermodynamics of lithium. • The prepared adsorbents showed high porosity, larger pore and volume sizes. • The adsorption capacity was increased by temperature and metal concentration. • Adsorption process of lithium onto the adsorbents was endothermic and spontaneous. • Desorption study presented 99% of lithium ions from all the adsorbents.

Development of a computational tool for the design of seawater reverse osmosis desalination systems powered by photovoltaics for crop irrigation

Access to fresh water is a major human right as mankind existence depends on it. The balance between fresh water supply and actual water demand for agricultural purposes (irrigation) relies on the availability of fresh water in the underground aquifers or surface water resources. Water resources are under great pressure due to the high demand for irrigation to sustain crop productivity and cover domestic use as a result of demographic growth. Desalination of sea or brackish water is one of the solutions to provide water for irrigation in remote areas of limited freshwater reserves. In such areas, if desalination is powered by renewable energy sources, then it can become a lot more sustainable. This paper presents the development of an innovative computational tool for the optimal (economically and technically) design of seawater reverse osmosis desalination systems for sustainable water production for crop irrigation. In order to further reduce the cost of water produced, an energy management and control system was also designed and included in the computational tool to ensure the optimal operation of the desalination plant. This system allows the seawater reverse osmosis unit to operate at variable load and determines its optimal operation point using computational intelligence techniques based on fuzzy cognitive maps. According to the results, the implementation of the computational tool for the design of PV-SWRO system presents the lowest cost as compared to the system designed with the conventional methodology.

Coupling of electromembrane processes with reverse osmosis for seawater desalination: Pilot plant demonstration and testing

Reverse osmosis (RO) is the most widespread technology to produce drinking water from seawater (SW). However, the integration of different membrane processes offers interesting alternatives. In this work, electromembrane processes were integrated with RO to desalinate real seawater in a pilot plant with 25 m3/day capacity. Electrodialysis (ED, either two-stage or single stage), shortcut reverse electrodialysis (scRED) and assisted reverse electrodialysis (ARED) pre-desalinated seawater before RO with the ED-ED-RO, ED-RO, and scRED-ARED-RO process schemes. Treated wastewater was used as salt sink in the scRED-ARED tests. The performance of the pilot plant can be summarized as follows: water recovery of ~27–51%, productivity of ~7–14 L/(m2 h) in the electromembrane processes and of ⁓19–31 L/(m2 h) in the RO process, energy consumption of 3.5–8.4 kWh/m3. The ED-RO configuration yielded the maximum productivity of the electromembrane step, while the scRED-ARED-RO integration reached the minimum energy consumption. Overall, the energy performance of the pilot plant (especially in the ED-RO and scRED-ARED-RO schemes) was comparable to that of a standalone SWRO system. The field tests demonstrated that the coupling of electromembrane processes with RO is feasible and suggest the possibility to develop alternative and competitive industrial pants for seawater desalination.

Characterization of the water mass dynamic changes surrounding a seawater reverse osmosis desalination plant on the east coast of the Kingdom of Bahrain

Characterization of the water mass dynamic changes surrounding a seawater reverse osmosis desalination plant on the east coast of the Kingdom of Bahrain

A MILP-based operational decision-making methodology for demand-side management applied to desalinated water supply systems supported by a solar photovoltaic plant: A case study in agricultural industry

In the field of water management, desalination industry has faced various economic and environmental challenges. Renewable energies and the incorporation of operational strategies such as demand-side management have been able to contribute with the aim of facing them. Nonetheless, it is necessary to continue studying demand-side management for water supply systems emphasising it as a strategic tool to make operational decisions. This article presents a methodology based on a novel Mixed-Integer Linear Programming model in order to program the operation of a seawater reverse osmosis desalination plant with one pumping station for a desertic remote agricultural zone, in accordance with the principles of demand-side management. A photovoltaic solar plant connected to the grid is considered as a renewable energy source. The mathematical model aims to establish the optimal hourly operating load of the system that minimises the daily margin of purchased electricity costs minus sales income of generated electricity. The case study where the methodology is tested is an agricultural area in Northern Chile. The proposed methodology in this paper establishes the basis for future research and industrial applications, considering that it can be generalised to other geographical situations, as well as being modifiable to be adapted for more complex water supply systems and/or other renewable energy sources.

Optimization of ultrafiltration as pre-treatment for seawater RO desalination

Ultrafiltration (UF) is increasingly used as pretreatment for reverse osmosis (RO) desalination, as an alternative to granular filtration. To ensure a sustainable and cost-effective operation of UF, key operational parameters must be optimized. In the present study we used a pilot UF system to optimize filtration flux, length of filtration cycle, coagulant dosing, and membrane cleaning procedure. Filtration flux of 82 LMH resulted in reversible fouling, which could be completely removed during chemically enhanced backwash, and did not affect filtration performance. Increasing the flux to 85 LMH on the other hand, resulted in the formation of irreversible fouling, which rapidly deteriorated UF operation. Filtration time of 35 min between backwashes did not affect filtration, whereas, at longer filtration time of 45 min, (hydraulically) irreversible fouling was formed. Addition of Ferric chloride coagulation prior to UF (up to 0.6 mg/L-Fe) improved the removal of reversible fouling during backwash (BW), through the formation of pinflocs. In parallel, high ferric chloride concentrations generated ferric-based irreversible fouling, which could only be removed by chemical cleaning. Finally, the study proposes a unique analysis of the trans membrane pressure (TMP) curve shape, for the optimization of coagulation and hydraulic cleaning during UF.