Forward Osmosis-reverse Osmosis Research Articles

Impact of temperature and forward osmosis membrane properties on the concentration polarization and specific energy consumption of hybrid desalination system.

This study investigates how temperature and forward osmosis (FO) membrane properties, such as water permeability (A), solute permeability (B), and structural parameter (S), affect the specific energy consumption (SEC) of forward osmosis-reverse osmosis system. The results show that further SEC reduction beyond the water permeability of 3 LMH bar-1 is limited owing to high concentration polarization (CP). Increasing S by 10-fold increases FO recovery by 177.6%, causing SEC decreases by 33.6%. However, membrane with smaller S also increases external CP. To reduce SEC, future work should emphasize mixing strategies to reduce external CP. Furthermore, increasing the temperature from 10 to 40 °C can reduce SEC by 14.3%, highlighting the energy-saving potential of temperature-elevated systems. The factorial design indicates that at a lower temperature, increasing A and decreasing S have a more significant impact on reducing SEC. This underlines the importance of developing advanced FO membranes, particularly for lower-temperature processes.

Transforming the Water-Energy Nexus in Gaza: A Systems Approach.

The acute water and electricity shortages in Gaza necessitate comprehensive solutions that recognize the interconnected nature of these vital resources. This article presents pragmatic solutions to align supply with fundamental needs in both domains, offering viable pathways for achieving strategic water-energy security in Gaza. Baseline data reveals a deficit in the current water supply, falling below the international minimum of 100 L per capita per day, while the reported 137-189 MW per day electricity supply significantly lags behind the estimated 390 MW per day peak demand. To meet projected 2024 residential, commercial, and industrial demands, this study proposes actionable measures including expanding wastewater treatment to enable over 150 MCM per year tertiary effluents for agricultural reuse and adopting energy-efficient forward osmosis-reverse osmosis and osmotically assisted reverse osmosis desalination methods to increase potable water supply to 150 MCM per year. Electricity supply strategies include scaling renewable capacity towards 110 MW per day, exploring regional cooperation to unlock over 360 MW of power per day, and potentially recovering up to 60 MW per day through system efficiencies. These recommendations aim to prevent exacerbated scarcity and alleviate hardships in Gaza.

An efficient data-driven desalination approach for the element-scale forward osmosis (FO)-reverse osmosis (RO) hybrid systems

Freshwater shortages are a consequence of the rapid increase in population, and desalination of saltwater has gained popularity as an alternative water treatment method in recent years. To date, the forward osmosis-reverse osmosis (FO-RO) hybrid technology has been proposed as a low-energy and environmentally friendly next-generation seawater desalination process. Scaling up the FO-RO hybrid system significantly affects the success of a commercial-scale process. However, neither the ideal structure nor the membrane components for plate-and-frame FO (PFFO) and spiral-wound FO (SWFO) are known. This study aims to explore and optimize the performance of SWFO-RO and PFFO-RO hybrid element-scale systems in the desalination of seawater. The results showed that both hybrid systems could yield high water recovery under optimal operating conditions. The prediction of the system performance (water flux and reverse salt flux) by artificial intelligence was considerably better (R > 0.99, root mean square error <5%) than that of conventional mass balance models. A Markov-based decision tree successfully classified the water flux level in hybrid systems. An optimal set of operational conditions for each membrane system was proposed. For example, in RO, a combination of the feed solution (FS) flow rate (≥17.5 L/min), FS concentration (<17,500 ppm), and operation pressure (<35 bar) would result in high water permeability (>40 LMH). In addition, five SWFO elements and four PFFO elements should be the optimal numbers of FO membranes in the hybrid FO-RO system for effective seawater desalination, especially for long-term operation.

Analysis of the effect of advanced FO spacer on the specific energy consumption of hybrid RO desalination system

Research involving hybrid forward osmosis-reverse osmosis (FO-RO) desalination has gained attention recently due to its potential to reduce energy consumption compared to traditional RO. This paper aims to understand the degree of the impact of advanced spacers in the FO process on the overall specific energy consumption (SEC) of FO-RO systems. The SEC for a representative advanced spacer is simulated and analysed under standard recovery and operating conditions. The results show that advanced spacers can significantly reduce SEC by up to 9.27% under the operating conditions considered. The results also show that placing an advanced spacer on the FO membrane draw side has a greater effect in reducing SEC compared to placing it on the feed side, due to the larger extent of ECP. It was found that FO channel pressure drop has insignificant impact on the SEC. The performance of advanced spacers in SEC reduction is most effective if the contribution of external concentration polarisation (ECP) to transmembrane osmotic pressure is high, if the contribution of internal concentration polarisation (ICP) is low, and if the effective transmembrane osmotic pressure is low. Optimal mixing in FO systems is therefore crucial to reduce SEC, especially for systems with severe ECP.

Multi-criteria decision making for a holistic assessment of sustainable alternatives in SWRO desalination: A case study

Water authorities have been constructing an increasing number of small-scale desalination treatment plants to provide drinking water for remotely located communities. Each location has a different situational context and community priorities, meaning that the treatment solutions should be selected considering a range of criteria and sub-criteria covering technical, economic, environmental, and health aspects. In this study, a comparison of three possible desalination alternatives was made using a multi-criteria decision-making (MCDM) tool in a rural area of Queensland, Australia. The studied alternatives encompassed standalone reverse osmosis (RO); forward osmosis (FO) coupled with RO (FO–RO), and ultrafiltration coupled with RO (UF–RO). The hybrid alternatives have the potential to significantly reduce energy consumption and environmental impact and to increase the efficiency of pathogenic removal and contaminations. The weights for the criteria were developed by integrating a multi-criteria feasibility assessment with a new survey that was responded by SWRO experts. Following this, the desalination alternatives were ranked using the TOPSIS method (technique for ordering preference by similarity to ideal solutions). A sensitivity analysis was conducted to see how the results would vary by changing the weights of preferences. The resulting MCDM framework ranked the UF-RO hybrid system as the best performing alternative with consistently high efficiency levels for stakeholders. The results showed that the performances of the FO-RO hybrid system and of the RO standalone system were similar, with FO-RO showing a marginal superiority in most of criteria.

Design and simulation of reverse osmosis process in a hybrid forward osmosis-reverse osmosis system

Reverse Osmosis (RO) is one of the widely adopted methods for water desalination to mitigate shortage of freshwater for domestic, irrigation and industrial consumption. Recently RO is also used as a draw solution regeneration step for most hybrid Forward Osmosis-Reverse Osmosis (FO-RO) systems used for water desalination. Accurate model is required which is more flexible and reliable, to design and operate RO treatment plants for producing freshwater from various water resources. However, most models do not represent multi element field scale RO systems accurately. Plant engineers widely use the available commercial programs for the design of multi element RO systems where the computational code is not provided, which makes the program inflexible. This work presents a computational tool developed on the python platform for the prediction and analysis of the RO process employed in a hybrid FO-RO system. A steady state model based on the solution-diffusion and film theory is established by employing concentration polarization, pressure drop and average solution properties in the computational calculations of the RO process. The model is used to design and estimate the performance parameters of an entire RO system having multiple membrane elements installed in a pressure vessel. A comparison between the outputs obtained by the model and membrane manufacturers software shows good agreement.

FO-MD setup analysis for acid mine drainage treatment in Chile: An experimental-theoretical economic assessment compared with FO-RO and single RO

Contamination of water bodies by acid mine drainage (AMD) from mining industries is affecting global freshwater availability, especially in arid zones like northern Chile. A real AMD from a contaminated Chilean river was used in this study. This work aimed to evaluate an economic projection of a Forward Osmosis–Membrane Distillation (FO-MD) process versus a Forward Osmosis–Reverse Osmosis (FO-RO) for an AMD treatment. FO-MD continuous assays (12 h) were performed using AMD solution as feed and NaCl as draw solution, achieving an initial flux of 25 LMH with FO and a stable flux around 10 LMH for MD. Different FO-MD economic models were developed using steam and thermal-fluid as heat-source. The cost assessment showed that thermal-fluid FO-MD has a payback period of 1.8 years with a water cost of 3.36 $/m3 while FO-RO's investment return was one year with a water cost of 1.47 $/m3. A Monte Carlo modeling results identified the membrane cost and the thermal energy expense as the elements with the highest impact on the economic indicators. Nevertheless, the economic assessment revealed that if waste-heat is available, the FO-MD operation cost would be lower than FO-RO's (1.29 $/m3), even with today's high FO/MD membrane cost.

Removal of Pathogens and Chemicals of Emerging Concern by Pilot-Scale FO-RO Hybrid Units Treating RO Concentrate, Graywater, and Sewage for Centralized and Decentralized Potable Reuse

This study evaluated the water quality produced by forward osmosis-reverse osmosis (FO-RO) treatment at pilot scale of RO concentrate generated at centralized potable reuse facilities and of graywa...

Influence of hydrodynamic operating conditions on organic fouling of spiral-wound forward osmosis membranes: Fouling-induced performance deterioration in FO-RO hybrid system

The forward osmosis-reverse osmosis (FO-RO) hybrid process has been extensively researched as part of attempts to reduce the high energy consumption of conventional seawater reverse osmosis in recent years. FO operating conditions play a substantial role in the hybrid process, dictating not only the performance of the entire system but also the propensity for fouling, which deteriorates performance in long-term field operations. Therefore, determining the optimal FO operating conditions with regard to membrane fouling may promote sustainable operation through efficient fouling control. This study thus evaluated the influence of each hydrodynamic operating condition (feed flowrate, draw flowrate, and hydraulic pressure difference) and their synergistic effects on fouling propensity in a pilot-scale FO operation under seawater and municipal wastewater conditions. Fouling-induced variation in water flux, channel pressure drop, diluted concentration, and the resulting specific energy consumption (SEC) were comparatively analyzed and utilized to project performance variation in a full-scale FO-RO system. Fouling-induced performance reduction significantly varied depending on hydrodynamic operating conditions and the resultant fouling propensity during 15 days of continuous operation. A high feed flowrate demonstrated a clear ability to mitigate fouling-induced performance deterioration in all conditions. A high draw flowrate turned out to be detrimental for fouling propensity since its high reverse solute flux accelerated fouling growth. Applying additional hydraulic pressure during FO operation caused a faster reduction of water flux, and thus feed recovery and water production; however, these drawbacks could be compensated for by a 10% reduction in the required FO membrane area and an additional reduction in RO SEC.

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).

Techno-economic analysis of combining forward osmosis-reverse osmosis and anaerobic membrane bioreactor technologies for municipal wastewater treatment and water production

The economic feasibility of combining forward osmosis (FO), reverse osmosis (RO) and anaerobic membrane bioreactor (AnMBR) technologies for municipal wastewater treatment with energy and water production was analysed. FO was used to pre-concentrate the AnMBR influent, RO for draw solution regeneration and water production, and AnMBR for wastewater treatment and energy production. The minimum wastewater treatment cost was estimated at 0.81 € m−3, achieved when limiting the FO recovery to 50% in a closed-loop scheme. However, the cost increased to 1.01 and 1.27 € m−3 for FO recoveries of 80% and 90%, respectively. The fresh water production cost was estimated at 0.80 and 1.16 € m−3 for an open-loop scheme maximising water production and a closed-loop scheme, respectively. The low FO membrane fluxes were identified as a limiting factor and a sensitivity analysis revealed that FO membrane fluxes of 10 LMH would significantly improve the competitiveness of FO-RO + AnMBR technology.

An empirical determination of the whole-life cost of FO-based open-loop wastewater reclamation technologies

Over the past 5–10 years it has become apparent that the significant energy benefit provided by forward osmosis (FO) for desalination arises only when direct recovery of the permeate product from the solution used to transfer the water through the membrane (the draw solution) is obviated. These circumstances occur specifically when wastewater purification is combined with saline water desalination. It has been suggested that, for such an “open loop” system, the FO technology offers a lower-cost water reclamation option than the conventional process based on reverse osmosis (RO).An analysis is presented of the costs incurred by this combined treatment objective. Three process schemes are considered combining the FO or RO technologies with membrane bioreactors (MBRs): MBR-RO, MBR–FO–RO and osmotic MBR (OMBR)-RO. Calculation of the normalised net present value (NPV/permeate flow) proceeded through developing a series of empirical equations based on available individual capital and operating cost data. Cost curves (cost vs. flow capacity) were generated for each option using literature MBR and RO data, making appropriate assumptions regarding the design and operation of the novel FO and OMBR technologies.Calculations revealed the MBR–FO–RO and OMBR-RO schemes to respectively offer a ∼20% and ∼30% NPV benefit over the classical MBR-RO scheme at a permeate flow of 10,000 m3 d−1, provided the respective schemes are applied to high and low salinity wastewaters. Outcomes are highly sensitive to the FO or OMBR flux sustained: the relative NPV benefit (compared to the classical system) of the OMBR-RO scheme declined from 30% to ∼4% on halving the OMBR flux from a value of 6 L m−2. h−1.

An optimization strategy for a forward osmosis-reverse osmosis hybrid process for wastewater reuse and seawater desalination: A modeling study

The reduction of energy consumption in the reverse osmosis (RO) process is critical. The forward osmosis (FO)-RO hybrid process can be suggested to reduce RO energy consumption. In this study, a numerical FO-RO process model was developed to analyze the FO-RO hybrid process. The performance of the FO-RO hybrid process was compared with the stand-alone RO process. In addition, the impacts of the control parameters for operation, and the intrinsic membrane parameters, were analyzed using sensitivity analysis. In conclusion, the FO-RO hybrid process involves less RO energy consumption than the stand-alone RO process. The FO draw flow velocity and the RO applied pressure were derived as the major factors for controlling the FO-RO process. In addition, the control parameters for operation were found to be more important than the intrinsic membrane parameters in the minimization of RO energy consumption. Subsequently, the FO elements installed in front of the RO process should be configured with a parallel connection, in order to minimize RO energy consumption. The results in this study could be used to develop guidelines for the optimal design of the FO-RO hybrid process.

Serially connected forward osmosis membrane elements of pressure-assisted forward osmosis-reverse osmosis hybrid system: Process performance and economic analysis

Due to the improved dilution of draw streams, employing pressure-assisted forward osmosis (PAFO) to the hybrid system of forward osmosis (FO) followed by reverse osmosis (RO) for seawater desalination has been expected to reduce the overall economics. However, replacing FO with PAFO causes an additional energy cost in the seawater dilution step which inevitably leads to a question that PAFO-RO hybrid is truly an economically beneficial option. More importantly, though serial connection of FO elements improves the dilution of initial draw water, this economic benefit is also compensated with the additional membrane. To rationalize its overall performance and economic benefit, thorough performance and economic evaluations were conducted based on actual pilot-scale PAFO operations for serial connection of up to three 8040 FO elements. The results showed the FO-RO hybrid is not an economically feasible option unless a significant unit FO element cost cut-down is guaranteed. Meanwhile, PAFO-RO showed benefits with regards to target RO recovery and unit FO element cost, particularly when two FO elements are serially connected (SE2). It was found that PAFO-RO, indeed, has higher economic potential than FO-RO. A graphical overlapping method suggested in this work can help determine optimal serial configuration and operating conditions of PAFO-RO.

Hybrid forward osmosis-reverse osmosis for wastewater reuse and seawater desalination: Understanding the optimal feed solution to minimise fouling

Abstract To enhance the seawater desalination energy efficiency forward osmosis – reverse osmosis (FO-RO) hybrid system has recently been developed. In this process, the FO “pre-treatment” step is designed to use seawater (SW) as draw solution to filter the wastewater (WW) while reducing the seawater osmotic pressure. Thereby reducing the operating pressure of the RO to desalinate the diluted SW. However, membrane fouling is a major issue that needs to be addressed. Proper selection of suitable WWs is necessary before proceeding with large-scale FO-RO desalination plants. In this study, long-term experiments were carried out, using state-of-the-art FO membrane, using real WW and SW solutions. A combination of water flux modelling and membrane characterisation were used to assess the degree of membrane fouling and the impact on the process performance. Initial water flux as high as 22.5 Lm−2 h−1 was observed when using secondary effluent. It was also found that secondary effluent causes negligible flux decline. On the other hand, biologically treated wastewater and primary effluent caused mild and severe flux decline respectively (25% and 50% of flux decline after 80 hours, compared to no-fouling conditions). Ammonia leakage to the diluted seawater was also measured, concluding that, if biologically treated wastewater is used as feed, the final NH4+ concentration in the draw is likely to be negligible.

A Study on Scale Determination of FO-RO Hybrid Process Based on FO Recovery Rate

ABSTRACT Kim, G.-Y.; Jeong, J.-W.; Kim, M.-G.; Kim, H.-S.; Kim, J.-H., and Kim, H.-S., 2017. A study on scale determination of FO-RO hybrid process based on FO recovery rate. In: Lee, J.L.; Griffiths, T.; Lotan, A.; Suh, K.-S., and Lee, J. (eds.), The 2nd International Water Safety Symposium. Journal of Coastal Research, Special Issue No. 79, pp. 75–79. Coconut Creek (Florida), ISSN 0749-0208. Recent studies have been actively conducted on forward osmosis-reverse osmosis hybrid process combining seawater desalination and wastewater reuse technology. It uses seawater as draw solution and reclaimed wastewater as feed solution in the FO process. Although it is possible to save operating costs in forward osmosis-reverse osmosis hybrid process, organic matter contained in treated water of forward osmosis may have a negative effect on the coastal environment. Therefore, studies are needed to evaluate the removal efficiency of organic matter in forward osmosis process and to enable the commercialization of forwa...

The Outlook for Forward Osmosis-Reverse Osmosis (FO-RO) Hybrid Desalination Market

Seawater desalination market after global economic crisis has been stalled due to the market uncertainties and decreased demand in desalination. It is important to review the status of the market and to estimate the appropriate share of Forward osmosis-Reverse Osmosis (FO-RO) hybrid desalination technology by figuring out the outlook of the desalination market. Main part of the desalination market will still be MENA (Middle East and North Africa) in the near future due to the fast population increase and high dependency of fossil fuel in the region. The market for FO-RO hybrid technology, however, might be smaller than the conventional SWRO desalination market anyway because of aesthetic issues from using wastewater as raw water and higher costs associated with capex. Therefore, it is essential to improve FO membrane performance and system operation technologies in order to make the hybrid technology attractive compared to the conventional SWRO technology.

Efficiently Combining Water Reuse and Desalination through Forward Osmosis-Reverse Osmosis (FO-RO) Hybrids: A Critical Review.

Forward osmosis (FO) is a promising membrane technology to combine seawater desalination and water reuse. More specifically, in a FO-reverse osmosis (RO) hybrid process, high quality water recovered from the wastewater stream is used to dilute seawater before RO treatment. As such, lower desalination energy needs and/or water augmentation can be obtained while delivering safe water for direct potable reuse thanks to the double dense membrane barrier protection. Typically, FO-RO hybrid can be a credible alternative to new desalination facilities or to implementation of stand-alone water reuse schemes. However, apart from the societal (public perception of water reuse for potable application) and water management challenges (proximity of wastewater and desalination plants), FO-RO hybrid has to overcome technical limitation such as low FO permeation flux to become economically attractive. Recent developments (i.e., improved FO membranes, use of pressure assisted osmosis, PAO) demonstrated significant improvement in water flux. However, flux improvement is associated with drawbacks, such as increased fouling behaviour, lower rejection of trace organic compounds (TrOCs) in PAO operation, and limitation in FO membrane mechanical resistance, which need to be better considered. To support successful implementation of FO-RO hybrid in the industry, further work is required regarding up-scaling to apprehend full-scale challenges in term of mass transfer limitation, pressure drop, fouling and cleaning strategies on a module scale. In addition, refined economics assessment is expected to integrate fouling and other maintenance costs/savings of the FO/PAO-RO hybrid systems, as well as cost savings from any treatment step avoided in the water recycling.

Evaluation of forward osmosis membrane performance by using wastewater treatment plant effluents as feed solution

AbstractCurrently, there is a growing emphasis on seawater desalination and wastewater reuse around the world. Reverse osmosis (RO) is typically used for both seawater desalination and wastewater reuse. As an alternative technology of RO, forward osmosis–reverse osmosis (FO–RO) hybrid system has recently attracted attention. To select suitable membrane and feed water for this process, the performance of forward osmosis (FO) membrane according to the types of membrane and feed water quality was evaluated in this study, including three types of FO membrane (membrane I/II/III) and three types of feed water (1st/2nd/3rd wastewater treatment plant effluents, WWTP Efs). Despite high structural parameter, membrane II showed the highest water permeability (5.37 LMH/bar) with highest water flux (around 27.1 LMH) using draw solution of 0.5 M NaCl (feed solution: 5 mM NaCl). In fouling test, there was severe water flux decline when 1st WWTP Ef was used as feed solution compared to the case when 2nd/3rd WWTP Efs was ...

Fouling characteristics and their implications on cleaning of a FO-RO pilot process for treating brackish surface water

In this study, a laboratory pilot scale forward osmosis-reverse osmosis (FO-RO) hybrid system was used to desalinate both actual and spiked brackish surface water (BSW). An overall performance evaluation was conducted and the membrane foulings were characterised by comprehensive techniques. Severe flux decline was observed during the treatment of high scaling/fouling potential feed solutions. It was found that when the raw BSW was used as feed, the flux can be completely recovered by hydraulic cleaning. When the raw BSW was spiked with nutrients and/or scaling ions for accelerated scaling and biofouling, more severe flux decline was observed. Inorganic scaling caused by calcium and phosphate, and their interactions with organic constituents in the feed solutions were the dominant cause of the declined system performance. For the spiked feed water, the combined physical and chemical cleaning using two chemical agents was not able to restore reduced flux to its initial value. This study identified the need for implementing a sufficient cleaning strategy targeting different membrane foulants, particularly for inorganic scalants; as well as confirms the need of fouling-resistant membrane.