•Techno-economic analysis is conducted with mass-transfer and cost models.•Closed-loop PRO can significantly reduce the CapEx and OpEx of seawater desalination.•FO pre-dilution can dilute the ...seawater feed to RO and reduce the RO pressure and OpEx.•Important to make PRO/FO membranes cost-friendly and endurable.
Pressure retarded osmosis (PRO) and forward osmosis (FO) have been proposed to integrate with seawater reverse osmosis (RO) in order to reduce the overall energy consumption of desalination. However, their economic advantages in comparison to conventional RO have not been validated. This study aims to use well-developed mass transfer and economic models to investigate the technical and economic feasibilities of four potential RO and PRO/FO hybrid processes. They are (1) RO and open-loop PRO (referred to as RO+oPRO) to harvest the osmotic energy using energy recovery devices (ERDs), (2) RO and closed-loop PRO (RO+cPRO) to harvest the osmotic energy and recycle the pressurized and diluted brine as seawater feed to RO, (3) RO and FO post-dilution (RO+FO) to dilute and recycle the RO brine, and (4) seawater feed pre-dilution by FO before entering RO (FO+RO) to reduce the RO operating pressure. RO+oPRO takes advantage of the osmotic energy and reduces the RO operating expenditure (OpEx), but requires huge additional capital expenditure (CapEx) that renders it uneconomical. RO+cPRO reduces both OpEx and CapEx because it eliminates the need of additional ERDs and downsizes the seawater intake, pretreatment and brine discharge units. RO+FO achieves the same CapEx saving as RO+cPRO but at an increased OpEx. FO+RO dilutes the seawater, reduces the RO operating pressure and significantly lowers OpEx, especially at a high RO recovery. Based on the analysis, we believe that RO+cPRO and FO+RO are the two most economical and promising processes to reduce both OpEx and CapEx of seawater desalination.
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.
Display omitted
•SEC analysis for FO advanced spacer under typical recovery and operating condition.•Advanced spacer works well if ECP contribution to Δπop is high and ΔπEffOP is low.•Placing advanced spacer on FO draw side is more effective than on the feed side.•SEC is most affected by changes in FO recovery rate.•Optimal mixing in FO is crucial especially for systems with severe ECP.
The water content in the recycled alginate solutions from aerobic granular sludge was nearly 100%. Forward osmosis (FO) has become an innovative dewatering technology. In this study, the FO ...concentration of sodium alginate (SA) was investigated using calcium chloride as a draw solute. The reverse solute flux (RSF) of calcium ions in FO had a beneficial effect, contrary to the findings of previous literature. The properties of the concentrated substances formed on the FO membrane on the feed side were analyzed by Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy, verifying that calcium alginate (Ca-Alg), which can be used as a recycled material, was formed on the FO membrane on the feed side owing to the interaction between SA and permeable calcium ions. Water flux increased significantly with the increase in calcium chloride concentration, while the concentration of SA had little influence on the water flux in FO. Based on this discovery, we propose a novel method for the concentration and recovery of alginate, in which the RSF of calcium ions is utilized for recovering Ca-Alg by FO, with calcium chloride as a draw solute.
Display omitted
•Forward osmosis concentration of calcium alginate was investigated.•Reverse salt diffusion of calcium ion has a beneficial effect.•Concentrated substance formed on forward osmosis membrane is verified.•Fourier transform infrared and X-ray photoelectron spectroscopies are used.•Novel design of forward osmosis membrane is crucial for research and development.
Forward osmosis (FO) is a competitive alternative of thermal process for food liquid concentration. In this work, highly concentrated pear juice (TSS >60 °Bx, concentration factor ∼ 6.5-fold) was ...successfully produced by a single-run FO process using sodium lactate (NaLA) as the draw solute, and the properties of concentrates were compared with those produced by vacuum evaporation. The evolution of water flux, process resistance as well as the key physicochemical properties of pear juice over time during FO were assessed. The rheological properties of pear juice concentrates and salt accumulation during concentration were also analyzed. The results suggest that NaLA is a powerful draw solute as it can not only provide sufficient driving force to concentrate the pear juice from TSS 9.6 °Bx to 62 °Bx by a single-run treatment without any recharge of draw solute, but also deliver pear juice concentrates of better quality with higher antioxidant capacity, non-browning delightful color and richer aroma and flavor compared to those produced by vacuum evaporation. This work offers a reference of both theoretical and practical aspects for liquid food processing in the future.
•Sodium lactate could be a promising draw solute for juice concentration.•Pear juice could be concentrated to 62 °Bx (6.5-fold) by a single-run FO process.•Overall concentrate quality of FO is much better than vacuum evaporation.
The global focus on water desalination using solar energy is particularly pronounced today. Previous studies have affirmed the efficiency of the Forward Osmosis (FO) and Membrane Distillation (MD) ...hybrid desalination system. The Photovoltaic Thermal (PVT) solar system, which generates both thermal and electrical energy, is complemented using Phase Change Material (PCM). PCM, known for storing and releasing significant heat during phase change, is used in the evening to meet the thermal needs of the system. Additionally, an integrated battery system stores the electrical energy generated by PVT, ensuring the system's electricity requirements are sustained during the night. A comprehensive numerical model, PVT-PCM-FO-MD, has been developed to analyze the proposed system. Operating seamlessly under natural conditions for a typical day on March, June and September, the proposed system can produce freshwater continuously over a 24-hour period. To assess system performance, three PCM thicknesses (2 cm, 4 cm, and 6 cm) were employed. Designed for small-scale applications, this system is well-suited for brackish water desalination in remote areas. Notably, the highest water production recorded was 213.25 L during a 24-hour operation and the MD unit exhibited an impressive 83.78 % evaporation efficiency during the typical day on June, with nighttime efficiency reaching 37.07 %, specifically at 3 am, utilizing a 2 cm PCM thickness in the solar energy system and it was 37.22 % at the same hour and PCM thickness in September. This study further explores the impact of initial brackish water salinity on water production after 24 h and investigates the influence of the initial draw solution concentration in the draw tank on desalinated water production. The study found that despite varying initial salinity levels, the difference in water produced at the end of the day was not exceeding 1.6 L.
In this study, the FO/crystallization/RO hybrid process was analyzed comprehensively, including experimentation, modeling, and energy and cost estimation, to examine and improve its feasibility to ...seawater desalination. A new operating strategy by heating the FO process to 45 °C was suggested, and a detailed process design was conducted. A comparative analysis with the conventional seawater reverse osmosis (SWRO) process was performed in terms of specific energy consumption (SEC) and specific water cost (SWC). The hybrid process can produce fresh water with SWC of 0.6964 $/m3, electrical SEC of 2.71 kWh/m3, and thermal SEC of 14.684 kWh/m3. Compared to the conventional SWRO process (SWC of 0.6890 $/m3 and electrical SEC of 2.674 kWh/m3), the hybrid process can produce water with comparable cost and energy consumption. An economic feasibility study that utilized the waste heat and the developed FO technology was also carried out to investigate future developments of the hybrid process. The SWC can be reduced to 0.6435 $/m3 with free waste heat energy. The permeate water quality of the hybrid process was about half that of the conventional SWRO process on molar basis. The results revealed that the FO/crystallization/RO hybrid process can be utilized as a competitive process for seawater desalination with high recovery and high water quality.
Display omitted
•New operation mode of FO/crystallization/RO hybrid process suggested.•Applicability of FO/crystallization/RO hybrid process experimentally confirmed.•This hybrid process confirmed as cost-competitive for seawater desalination.•Utilizing waste heat, water produced at 7% lower cost than that with SWRO.•Permeate water quality approximately half of the conventional SWRO on molar basis.
•Black odorous water was concentrated by aquaporin biomimetic membrane for further treatment.•TN rejection ratio was largely dependent upon the NH4+-N/TN ratio.•AOB community affected NH4+-N ...transformation and caused TN rejection fluctuation.•The elements P, Na and the blackening metals Fe and Mn accumulated in the fouling layer.•Water flux decline was not observed with physical cleaning only.
This study aimed to investigate pollutant concentration and membrane fouling characteristics of a forward osmosis (FO) process using aquaporin biomimetic membrane (ABM) for concentrating black odorous water. The membrane cells were operated in active layer facing feed solution (ALFS) mode with 2 M NaCl solution as the draw solution. The system was continuously performed for 64 batch cycles, and each cycle duration was 24 h. At the end of each cycle, physical cleaning with deionized water was employed as the membrane recovery strategy. The results showed that the rejection ratios of chemical oxygen demand (COD), total phosphorus (TP) and nitrate (NO3−-N) could reached 97.2%, 98.0%, and 85.0%, respectively, while most NH4+-N penetrated into the draw solution due to cation exchange. The total nitrogen (TN) rejection ratio was largely dependent upon the NH4+-N/TN ratio. At high NH4+-N/TN ratio, the successions of ammonia oxidizing bacteria (AOB) communities enriched in the biofouling layer in different experimental stages would affect the transformation degree of NH4+-N, and thus lead to much fluctuations of TN rejection. The average initial water flux reached 9.84 L/(m2·h), and the average water flux of each cycle kept stable especially in the later stage of the experiment. In the biofouling layer, polysaccharides enhanced while proteins decreased in the later period. P, Mn, Fe and Na also accumulated on the surface. Norank_f__Reyranellaceae, Erythrobacter, SM1A02, Pirellula, and Hydrogenophaga were the predominant genera enriched in the fouling layer, which would lead to complex pollutants transformations, especially nitrogen transformation, during the FO process.
Classical purification of pharmaceuticals is energy-intensive and employs toxic solvents that are discarded, calling for more sustainable methods. Here, we purified tetracycline by organic solvent ...forward osmosis using ionic liquids. Results show the osmotic enrichment of feed solutions containing different concentrations of tetracycline in methanol. The solvent flux during the filtration process is mainly influenced by solvent properties, such as molecular size, viscosity, polarity, and the solvent–membrane interaction. We evaporated the diluted draw solution to recover the draw solute for reuse. Overall ionic liquids appear as suitable draw solutes for organic solvent forward osmosis for pharmaceutical compound enrichment with draw solute recovery and reuse.
An effective and scalable hydrodynamic interfacial polymerization approach was developed for engineering dense/porous Janus thin-film composite membranes for forward osmosis (FO) applications. The ...resulting Janus composite FO membrane experiences a smaller diffusion resistivity (K = 1.7×105 s/m) and minimises reverse solute flux (RSF ≤ 1 g m−2h−1) to deliver a significantly higher (by 1073.5%) perm-selectivity than that of the conventional polyamide-based FO membrane.
Display omitted
•An effective and scalable approach was proposed for engineering Janus FO membrane.•Dynamic interfacial shear was created for forming a thin, dense, and smooth PA layer.•The resulting Janus membrane experiences smaller diffusion resistivity and minimises RSF.•The FO membrane delivers a significantly high perm-selectivity.
Limited by their intrinsic features, conventional forward osmosis (FO) membranes suffer from defect-triggered selectivity losses and blockage-induced low permeabilities. Herein, we developed a hydrodynamic interfacial polymerization (DIP) strategy for fabricating highly permselective thin-film composite (DTFC) membranes with dense/porous Janus structure. The dynamic fluid flow of reactant monomers at the immiscible liquid–liquid interface creates shear forces that enhance polyamide (PA) polymerization on the surface of a three-dimensional (3D) porous spinning skeleton. Computational fluid dynamics simulations confirm that interfacial shear flow acting on PA crystals induces the epitaxial growth of a dense, continuous, thin, and smooth PA layer. The resulting DTFC membrane showcased a significantly enhanced water/salt flux ratio (Jw/Js), exceeding that of static thin-film composite (STFC) membrane by a substantial 1073.5 %, thus embodying exceptional permselectivity. This superior performance is attributable to a smaller diffusion resistivity (K = 1.7×105 s/m) and an ultralow reverse solute flux (RSF ≤ 1 g m−2h−1). These findings provide new insight into the role of interfacial control in regulating TFC structure and FO performance.
Pressure retarded osmosis (PRO) is an emerging technology to harvest the renewable salinity-gradient energy. However, its performance can be significantly limited by severe membrane fouling if a real ...waste effluent is used as the feed solution. To tackle this, we have experimentally demonstrated that forward osmosis (FO) can be used as a pretreatment means to extract water from the wastewater stream to the inter-loop solution. Subsequently, the diluted inter-loop solution could serve as a clean feed to the PRO unit at negligible fouling tendency. As a result, the newly developed FO-PRO hybrid system is capable of sustaining osmotic power generation with the advantages of FO such as (1) low fouling propensity, (2) easy membrane cleaning, and (3) minimal external energy required. Model simulations of full-scale analyses reveal that, by choosing the salinity of the inter-loop solution to PRO as 0.1 M, it is possible to reach a power density greater than 5 W/m2 set by Statkraft as the commercially viable benchmark. Meanwhile, the concentrated brine draw solution of PRO can be diluted back to the seawater level for easy disposal or reuse. Under this condition, FO possesses a comparable water flux with conventional pretreatment methods using pressure driven membrane processes. A simple design strategy is also provided in detail for the integration of FO and PRO units.
Display omitted
•A novel FO-PRO hybrid system is developed for sustainable osmotic power generation.•A real waste effluent from a water recycling plant serves as the feed solution.•The FO unit shows superior fouling resistance with a water flux of 10–15 LMH.•The PRO unit can reach a power density greater than 5 W/m2 at 50% dilution of SWBr.•A simple design strategy is provided for the integration of FO and PRO units.
