Article

Energy Consumption of Water Recovery from Wastewater in a Submerged Forward Osmosis System Using Commercial Liquid Fertilizer as a Draw Solute

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Abstract

Using liquid fertilizer as a draw solute in forward osmosis (FO) to extract high-quality water from wastewater is of strong interest because it eliminates the need for regenerating draw solute, thereby requiring less energy input to system operation. However, energy consumption of such an approach has not been evaluated before. Herein, a submerged FO system with all-purpose liquid fertilizer as a draw solute was studied for energy consumption of water recovery from either deionized (DI) water or domestic wastewater. The results showed that a higher draw concentration led to higher water flux and lower energy consumption, for example 0.25 ± 0.08 kWh m⁻³ with 100% draw concentration, but reverse salt flux (RSF) was also more serious. Decreasing the recirculation flow rate from 100 to 25 mL min⁻¹ had a minor effect on water flux, but significantly reduced energy consumption from 1.30 ± 0.28 to 0.09 ± 0.02 kWh m⁻³. When extracting water from the secondary effluent, the FO system exhibited comparable performance of water flux and energy consumption to that of the DI water. However, the primary effluent resulted in obvious fouling of the FO membrane and higher energy consumption than that of the secondary effluent/DI water. This study has provided important implications to proper evaluation of energy consumption by the FO system using liquid fertilizer or other non-regenerating draw solutes.

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... Achili el a., 2010 showed that for experiment carried out at fixed S and under constant operating conditions, KCl and NH 4 Cl had the highest D D and generated the highest WF. Xiang et al. (2017) showed higher WF at high DS concentration due to the development of osmotic driving force through the membrane. The DS was continuously diluted by the transferred water from FS, leading to a decrease in OP and water flux. ...
... Such behavior is justified based on the direct relationship between the reverse solute diffusion through the membrane and the DS concentration difference across the membrane AL and not on the difference between bulk concentrations (Phuntsho et al., 2011. Xiang et al. (2017) observed that the RSF differs for different nutrients with the highest being total nitrogen (TN) and lowest being K þ and PO 3À 4 . The high RSF for TN is related to cross-membrane leakage of nitrogen compounds. ...
... The slight improvement in WF by changing flow rate of DS and FS can be related to the rapid movement of the permeated water through the membrane system leading to increase in the hydraulic shear force across the membrane and decreasing the effect of external concentration polarization (ECP) on AL and/or PL leading to more water diffusion . Xiang et al. (2017) showed that WF and %W recovery were enhanced for pressure driven process at high flow rates and the same trends could be applied for FO processes. This justifies the rise in water flux and %W recovery as flow rates of FS and DS increased from 1.6 LPM to 2.8 LPM. ...
... The water flux (J W ) was determined based on the mass variation of the DS over time and was calculated from Eq. (3) [26]: where J W (L/m 2 ·h) is the water flux, m DSt 1 (g) is the mass of the DS at recording time interval t 1 (h), m DSt 2 (g) is the mass of the DS at recording time interval t 2 (h), A m (m 2 ) is the effective membrane area, and t 1 and t 2 (h) is the recording time intervals, ρ (g/L) is the density of the solution. It is assumed that the change in mass of the DS is mainly attributed to the permeation of pure water. ...
... SEC was determined based on the theoretical work done by the circulation pump and was calculated using Eq. (7) [26]: ...
... As OP is a colligative property, an increase in DS concentration will lead to an increase in the OP which in turn produced an increased J w and R e which resulted in a reduction in SEC. A study by Xiang et al. [26] also reported a reduction in SEC with an increase in DS concentration whilst utilising a liquid fertiliser as DS and wastewater as an FS using a submerged FO system. concentration of 2 M and a flow rate of 400 mL/min. ...
Article
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Agriculture consumes approximately 70% of total freshwater worldwide. With limited freshwater resources, alternative water resources are required. This study investigated the performance of a fertiliser drawn forward osmosis (FDFO) system for water recovery from synthetic brackish water with repeated use of a cellulose triacetate (CTA) FO membrane under varying fertiliser draw solution (DS) concentrations (0.5, 1 and 2 M KCl); membrane orientations (FO vs PRO) and flow rates (100, 200 and 400 mL/min); with the corresponding effects on the specific energy consumption (SEC). Results demonstrated a robust CTA membrane with no damage. An increased DS concentration from 0.5 to 1 M KCl contributed to a three-fold increase in flux, followed by a 30 to 50% increase for 2 M KCl and a reduced SEC. Membrane orientation and flow rate had insignificant effects on performance, however, flow rate contributed to an SEC increase. FO mode at a lower flow rate combined with a higher DS concentration produced the lowest possible SEC. The study illustrated a potential lower energy process for water recovery from synthetic brackish water whilst at the same time producing a diluted fertiliser that could potentially be used for fertigation.
... Several fertilizers have been tested for their potential as DS in FDFO process. Inorganic fertilizers such as urea, ammonium sulfate, ammonium chloride, diammonium phosphate and potassium nitrate [1][2][3][4][5]; blend of various fertilizers [6,7]; and liquid fertilizers [8,9] have been used as DS for desalination. FDFO can draw water from other impaired water sources [6,9,10]. ...
... Inorganic fertilizers such as urea, ammonium sulfate, ammonium chloride, diammonium phosphate and potassium nitrate [1][2][3][4][5]; blend of various fertilizers [6,7]; and liquid fertilizers [8,9] have been used as DS for desalination. FDFO can draw water from other impaired water sources [6,9,10]. Practically the dilute draw solution generated needs further dilution to decrease the concentration level required for fertigation purposes [4]. ...
Article
Inorganic fertilizers, namely potassium chloride and monoammonium phosphate, have been used as draw solute for dewatering of brackish water and wastewater by forward osmosis (FO). A bench-scale unit with an ultra-low-pressure RO membrane was used. Moderate water flux was achieved for desalination of brackish water and wastewater concentration. Water flux using blended fertilizer was little lower than using individual fertilizers. Low reverse solute flux entailed negligible draw solute replenishment and eliminated eutrophication issues in feed disposal. Reversible fouling was observed with > 90% flux restoration. Partial recovery of draw solute by low-pressure nanofiltration process produced fertilizer solution with NPK content suitable for fertigation and hydroponics without any loss of precious draw solute. The integrated fertilizer-driven FO–NF system proved to be versatile and effective.
... The relative specific energy consumption (SEC-kWh/m 3 ) was calculated so as to evaluate the comparative performance during the long-term tests. Calculation is standard and accords with previous works [13,40,41]. Fouling-induced flux decline and increment of channel pressure drop leads to a variation in energy consumption for different operating conditions [42]. ...
... The present work suggests that 21 LMH is a sound guideline but to minimize membrane costs 25 LMH should be explored because elsewhere this value has been reported to be the critical flux, albeit at a higher value of CFV. However, increase of CFV will cause an increase in energy consumption [13,41]. Therefore in further work, critical flux behavior under different CFVs should be investigated so as to achieve an appropriate balancing of fouling mitigation and energy consumption. ...
Article
A strategy of using critical fluxes to control organic fouling of polyamide thin film composite (PA-TFC) forward osmosis (FO) membranes during wastewater reclamation was developed for FO mode. This work was a comprehensive investigation with various organic foulants covering complex mixtures as well as single foulants. The foulants were alginate (ALG), Humic acid (HA), and Bovine Serum Albumin (BSA) and the study covered different concentration (40; 80; 120; 160 mg/L). Our results indicated that there was a single value of critical flux, 35 LMH for 160 mg/L and single foulant. However the presence of mixed foulants i.e., ALG+BSA, ALG+HA, HA+BSA, at an overall foulant concentration of 160 mg/L gave rise to foulant-foulant-membrane interactions that caused a significant decrease in critical flux values to 25-30 LMH. Using these results as a guide, long-term tests in which there was no fouling or negligible fouling were successfully implemented. Operating below critical flux maintains a sustainable operation with the characteristic of full reversibility, which is vital if chemical cleaning is to be minimized. Characterization of fouling around critical values was made through physico-chemical analyses including SEM, EEM, aggregate size, zeta potential, and FTIR. It was found that FO fouling became irreversible when operated at a flux ≥ 35 LMH for single foulants and fluxes of 25 LMH and 30 LMH for ALG+BSA and HA+BSA foulants respectively, being a foulant concentration of 160 mg/L; such conditions are favorable for the formation of the cohesive and compact cake layer. Economic assessments based on specific energy consumption facilitated the production of guidelines for practical design and operation.
... To date, a few studies on the FDFO system demonstrated a comparison between different physical cleaning approaches to evaluate the system performance, whereas most studies on the FDFO system have employed one of the physical cleaning approaches depending on the type or source of FS. These studies reported that the hydraulic in situ flushing is suitable for the FDFO system operated with FS that has low salinity and negligible organic contaminates [23]. Accordingly, this study examined the effect of membrane fouling by using a CTA membrane oriented in FO mode (the active layer facing the FS) on the performance of the FDFO system. ...
... The type of FS has a major influence in determining the required cleaning approach for the FDFO system. Studies on the FDFO system have examined the process performance by using a very contaminated FS such as a sewage water and primary wastewater [23,33]. For such system, the hydraulic flushing was insufficient to recover water flux and they suggested the need to apply a pre-treatment to the FS. ...
Article
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Fertilizer-drawn forward osmosis (FDFO) has garnered immense attention for its application in the agricultural field and its potential to reuse wastewater sustainably. Membrane fouling, however, remains to be a challenge for the process. This study aims to investigate the influence of membrane fouling on the performance of the FDFO process. Synthetic wastewater (SWW) and multi-component fertilizer (MCF) were used as feed solution (FS) and draw solution (DS) with cellulose triacetate (CTA) forward osmosis (FO) membrane orientation. The performance was evaluated through water flux (WF), percentage recovery and percentage of salt reject. The WF declined from 10.32 LMH (L/m2·h) to 3.30 LMH when ultra-pure water as FS was switched with concentration FS indicating the dependence of the performance on the type of FS used. Accelerated fouling experiments conducted to verify the fouling behavior showed a decline in the water flux from 8.6 LMH to 3.09 LMH with SWW and 13.1 LMH to 3.42 LMH when deionized water was used as FS. The effects of osmotic backwashing and in situ flushing as physical cleaning methods of the foul membrane were studied through water flux and salt recovery percentage. Both cleaning methods yielded a WF close to the baseline. Osmotic backwashing yielded better results by eliminating foulant-foulant and foulant-membrane adhesion. The cleaning methods were able to recover 75% of phosphate and 60% of nitrate salts. Scanning electron microscopy (SEM), atomic force microscopy (AFM) and Fourier transform infrared (FTIR) results validated the effectiveness of the methods for the physical cleaning of foul membranes. This study underlines the importance of the FS used in FDFO and the effectiveness of osmotic backwashing as a cleaning method of FO membranes.
... Having differentiated between the operating principles of FO and RO, the net energy consumption of a FO process has to be taken into account where the recovery of draw solute/solution is an energy intensive step. If the process design allows for the diluted draw to be used as it is, viz fertilizers as draw solutions [36], the operational cost is much lower compared to pressure-driven RO [37]. The draw solution replenishment over the course of operations needs to be taken into account considering some losses as reverse soluted flux. ...
... FO could concentrate domestic wastewater containing high chemical oxygen demand (COD) and biological oxygen demand (BOD) from the produced sludge to an extent of ∼ 10-folds using 2.2 M MgCl 2 as draw solution. In efforts to optimize FO performance while dealing with domestic effluents, Xiang et al. [37] observed that higher concentration of draw would lead to higher water flux using submerged FO system, for which less energy was consumed. It is apparent that higher concentration of draw solution, higher osmotic pressure can exert across the membrane and higher concentration gradient, resulting in higher fluxes. ...
Article
Access to clean water resources has become a global challenge in recent times, especially in developing countries, where huge amounts of highly polluted industrial and municipal effluents are produced and discharged into the receiving environments. Applications of membrane technologies to deal with effluents from various origins have recently received a great deal of attention due to their inherent advantages, compared to other physico-chemical methods developed so far to this end. Forward osmosis (FO) is among the efficient membrane-based processes adopted by wastewater treatment facilities, with various configurations currently being transferred from laboratory and pilot-scales to large-scale applications. Still FO technologies are plagued with drawbacks such as fouling, internal concentration polarization (ICP), reverse solute flux and draw solution recovery, which invariably increases the cost of operation and restricts the feasibility for large-scale and long-term use because economic considerations are the most important sustainability criteria when selecting a wastewater treatment technique among the various alternatives. Several modifications have been introduced in recent years to overcome the existing limitations, such as incorporation of engineered nanomaterials onto the membrane surface to mitigate membrane fouling and to enhance their life-time, thereby minimizing the cleaning and (when necessary) replacement costs. Several FO based pre-treatment technologies have also been introduced for complex effluents treatment to minimize the operational costs arising from cleaning and replacement activities. Therefore, assessing the performance of such technologies according to sustainability indicators is the key to ensure long-term benefits from the application of FO technologies for the treatment of highly polluted effluents. In this review, sustainability criteria for the treatment of industrial effluents using FO technologies are discussed. The current states of the technologies regarding sustainability criteria are discussed. Scaling-up opportunities for the existing lab-scale modules have been evaluated and environmental footprint of the under-developed technologies are discussed. This review will therefore aid in selecting the most suitable configurations of FO technologies (standalone/hybrid) to deal with the highly polluted effluents for real world applications and to direct future studies in this emerging area. Perspectives and recommendations for future studies are also included.
... The energy consumption was evaluated on the whole system level (MEC-FO), and the consumption rate was normalized by unit treated wastewater (kWh m À3 ), unit reduced COD (kWh kg COD À1 ), unit removed or recovered NH 4 þ -N (kWh kg N À1 ), or unit obtained struvite (kWh kg À1 ). The energy consumption rate of the FO was normalized by unit extracted clean water (kWh m À3 ) (Xiang et al., 2017). The abovementioned specific energy consumptions (SEC), based on total energy input of major energy consumers (power supply and/or recirculation pumps) and output hydrogen gas, were provided in Supplementary Materials (Eqs. ...
Article
Recovery of nutrients, water, and energy from high-strength sidestream centrate offers benefits such as reusable resource, minimized discharge and cost-savings in mainstream treatment. Herein, a microbial electrolysis cell - forward osmosis (MEC-FO) hybrid system has been investigated for integrated nutrient-energy-water (NEW) recovery with emphasis on quantified mass balance and energy evaluation. In a closed-loop mode, the hybrid system achieved recovery of 54.2 ± 1.9% of water (70.4 ± 2.4 mL), 99.7 ± 13.0% of net ammonium nitrogen (8.99 ± 0.75 mmol, with extended N2 stripping), and 79.5 ± 0.5% of phosphorus (as struvite, 0.16 ± 0.01 mmol). Ammonium loss primarily from reverse solute flux was fully compensated by the reclaimed ammonium under 6-h extended N2 stripping to achieve self-sustained FO process. The generated hydrogen gas could potentially cover up to 28.7 ± 1.5% of total energy input, rendering a specific energy consumption rate of 1.73 ± 0.08 kWh m−3 treated centrate, 0.57 ± 0.04 kWh kg−1 COD, 1.10 ± 0.05 kWh kg−1 removed NH4+-N, 1.17 ± 0.06 kWh kg−1 recovered NH4+-N, or 5.75 ± 0.54 kWh kg−1 struvite. Recycling of excess Mg2+ reduced its dosage to 0.08 kg Mg2+/kg struvite. These results have demonstrated the successful synergy between MEC and FO to achieve multi-resource recovery, and encouraged further investigation to address the challenges such as enhanced hydrogen production, reducing nutrient loss, and optimizing MEC-FO coordination towards an energy-efficient NEW recovery process.
... The regeneration-free fertilizer-driven FO (FDFO) process [19] uses the self-diluted fertilizers as draw solutes, which can be directly used for agricultural irrigation without energy-intensive solute regeneration [20]. Commercial all-purpose liquid and solid fertilizers have been studied for osmotic dilution [21,22]. A pilot-scale fertilizer drawn forward osmosis and nanofiltration (FDFO-NF) was recently established and had been successfully operated for six months [23]. ...
... The FSF of NH 4 + -N, K + , Ca 2+ , Mg 2+ were 164.3 ± 12.2, 80.9 ± 13.9, 43.1 ± 1.8, 1.59 ± 0.3 mmol m −2 h −1 with loss percentages of 61.2 ± 4.5%, 41.5 ± 7.1%, 13.6 ± 0.6% and 2.3 ± 0.4%, respectively (Fig. 7D). It is obvious that multivalent ions, such as Mg 2+ and Ca 2+ , exhibited reduced loss rates (Xiang et al., 2017) and lower FSF due to larger hydrated radii (Mg 2+ : 4.4 Å and Ca 2+ : 4.2 Å), comparing with monovalent ions (NH 4 + : 3.31 Å and K + : 3.31 Å) (Nightingale, 1959). However, continuous loss of ions from the feed solution would cause undesirable pollution of the draw solution, requiring further purification for water reuse. ...
Article
Abstract Landfill leachate contains substances that can be potentially recovered as valuable resources. In this study, magnesium in a landfill leachate was recovered as struvite with calcium pretreatment; meanwhile, the leachate volume was reduced by using a submerged forward osmosis (FO) process, thereby enabling significant reduction of further treatment footprint and cost. Without pretreatment, calcium exhibited strong competition for phosphate with magnesium. The pretreatment with a Ca2 +: CO32– molar ratio of 1:1.4 achieved a relatively low loss rate of Mg2 + (24.1 ± 2.0%) and high Ca2 + removal efficiency (89.5 ± 1.7%). During struvite recovery, 98.6 ± 0.1% of magnesium could be recovered with a significantly lower residual PO43 −-P concentration (< 25 mg L− 1) under the condition of (Mg + Caresidual): P molar ratio of 1:1.5 and pH 9.5. The obtained struvite had a similar crystal structure and composition (19.3% Mg and 29.8% P) to that of standard struvite. The FO process successfully recovered water from the leachate and reduced its volume by 37%. The configuration of calcium pretreatment - FO - struvite recovery was found to be the optimal arrangement in terms of FO performance. These results have demonstrated the feasibility of magnesium recovery from landfill leachate and the importance of the calcium pretreatment, and will encourage further efforts to assess the value and purity of struvite for commercial use and to develop new methods for resource recovery from leachate.
... The FSF of NH 4 + was 1.86 mmol m −2 h −1 after 24 h, rendering a loss rate of 2.5%. Ion penetration via FSF could cause potential pollution on the feed side, requiring further treatment and increasing operation cost towards water reuse [25]. Multivalent ions with larger hydrated radii would be more difficult to diffuse through the FO membrane, presenting a reduced FSF and lower loss rate than that of the monovalent ions (NH 4 + ) [26]. ...
... Production of available freshwater, one of the biggest challenges in technological, social, and economical fields, is highly significant to 1/7 people, industry and agriculture under water shortage in the world [1]. To solve the problem, many efforts have been devoted on developing a cost-effective desalination technology over the past years, which is considered as one of the most practical solutions to overcome water shortage especially for the seaside cities [2,3]. However, the thermal processes (phase-change) or membrane processes used for water desalination have negative impacts on the energy storage and environment due to the huge energy consumption and the inevitable byproducts of the concentrated brine disposal [4]. ...
Article
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Carbonaceous materials, one of the most important electrode materials for sea water desalination, have attracted tremendous attention. Herein, we develop a facile and effective two-step strategy to fabricate hierarchical porous carbon nanotubes/graphene/carbon nanofibers (CNTs/G/CNFs) composites for capacitive desalination application. Graphite oxide (GO), Ni²⁺, and Co²⁺ are introduced into polyacrylonitrile (PAN) nanofibers by electrospinning method. During the annealing process, the PAN nanofibers are carbonized into CNFs felt, while the CNTs grow in situ on the surface of CNFs and graphite oxide are reduced into graphene simultaneously. Benefiting from the unique hierarchical porous structure, the as-prepared CNTs/G/CNFs composites have a large specific surface area of 223.9 m² g⁻¹ and excellent electrical conductivity. The maximum salt capacity of the composites can reach to 36.0 mg g⁻¹, and the adsorbing capability maintains a large retention of 96.9% after five cycles. Moreover, the effective deionization time of the CNTs/G/CNFs composites lasts more than 30 min, much better than the commercial carbon fibers (C-CFs) and graphene/carbon nanofibers (G/CNFs) composites. Results suggest that the designed hierarchical porous CNTs/G/CNFs architecture could enhance the capacitive desalination properties of electrode materials. And the possible adsorption mechanism of the novel electrode materials is proposed as well. © 2018 Springer Science+Business Media, LLC, part of Springer Nature
... on and produce clean water, were compared in the study byZhang, Song et al. (2017). The results of the study showed that TFC membranes exhibited a higher initial flux but more dramatic flux decline compared to CTA membranes and that all 30 TrOCs selected in the study were effectively removed by the OMBR-RO hybrid regardless of the FO membrane type.Xiang et al. (2017) used a submerged FO system with all-purpose liquid fertilizer as draw solution investigated the energy consumption of water recovery from either deionized (DI) water or domestic wastewater. They reported that a higher draw concentration (100%) led to higher flux and lower energy consumption (0.25±0.08 kWh/m 3 ) but reverse salt flux (RS ...
Article
This review, for literature published in 2017, contains information related to membrane processes for municipal and industrial applications. This review is a subsection of the Treatment Systems section of the annual Water Environment Federation literature review and covers the following topics: membrane bioreactor (MBR) configuration, design, nutrient removal, operation, industrial treatment, anaerobic membrane systems, reuse, microconstituents removal, membrane technology advances, membrane fouling, and modeling. Other sub-sections of the Treatment Systems section that might relate to this literature review include: Biological Fixed-Film Systems, Activated Sludge and Other Aerobic Suspended Culture Processes, Anaerobic Processes, and Water Reclamation and Reuse. The following sections might also have related information on membrane processes: Industrial Wastes, Hazardous Wastes, and Fate and Effects of Pollutants.
... Alternatively, DS that do not require regeneration would potentially address energy and cost issues (Zhao et al., 2012). For example, the fertilizer-driven FO employs the commercial fertilizers as DS Xiang et al., 2017;Zou and He, 2016), and diluted draw solution may be directly used for agricultural irrigation Phuntsho et al., 2016). Fig. 1. ...
Article
Forward osmosis (FO) has emerged as a potentially energy-efficient membrane treatment technology to yield high-quality reusable water from various wastewater/saline water sources. A key challenge remained to be solved for FO is reverse solute flux (RSF), which can cause issues like reduced concentration gradient and loss of draw solutes. Yet no universal parameters have been developed to compare RSF control performance among various studies, making it difficult to position us in this “battle” against RSF. In this paper, we have conducted a concise review of existing RSF reduction approaches, including operational strategies (e.g., pressure-, electrolysis-, and ultrasound-assisted osmosis) and advanced membrane development (e.g., new membrane fabrication and existing membrane modification). We have also analyzed the literature data to reveal the current status of RSF reduction. A new parameter, mitigation ratio (MR), was proposed and used together with specific RSF (SRSF) to evaluate RSF reduction performance. Potential research directions have been discussed to help with future RSF control. This review intends to shed more light on how to effectively tackle solute leakage towards a more cost-effective and environmental-friendly FO treatment process.
... As expected, significant reduction of E s,total from 1.103 ± 0.059 kWh kg À1 to 0.044 ± 0.002 kWh kg À1 was obtained with decreasing the recirculation rate from 60 mL min À1 to 10 mL min À1 . Although the estimate of energy consumption in a bench-scale system cannot fully reflect that of a full-scale system for practical application (Xiang et al., 2017), it does provide implications that, to achieve mitigated RSF, electrolysis did not require significant energy input, and optimizing the operation of the e-FO system such as recirculation could save energy and thus offset the energy input by electrolysis. In addition, the benefits brought by RSF mitigation may compensate the cost increase induced by exerting voltage. ...
Article
Forward osmosis (FO) has been widely studied for desalination or water recovery from wastewater, and one of its key challenges for practical applications is reverse solute flux (RSF). RSF can cause loss of draw solutes, salinity build-up and undesired contamination at the feed side. In this study, in-situ electrolysis was employed to mitigate RSF in a three-chamber FO system (“e-FO”) with Na2SO4 as a draw solute and deionized (DI) water as a feed. Operation parameters including applied voltage, membrane orientation and initial draw concentrations were systematically investigated to optimize the e-FO performance and reduce RSF. Applying a voltage of 1.5 V achieved a RSF of 6.78 ± 0.55 mmol m−2 h−1 and a specific RSF of 0.138 ± 0.011 g L−1 in the FO mode and with 1 M Na2SO4 as the draw, rendering ∼57% reduction of solute leakage compared to the control without the applied voltage. The reduced RSF should be attributed to constrained ion migration induced by the coactions of electric dragging force (≥1.5 V) and high solute rejection of the FO membrane. Reducing the intensity of the solution recirculation from 60 to 10 mL min−1 significantly reduced specific energy consumption of the e-FO system from 0.693 ± 0.127 to 0.022 ± 0.004 kWh m−3 extracted water or from 1.103 ± 0.059 to 0.044 ± 0.002 kWh kg−1 reduced reversed solute. These results have demonstrated that the electrolysis-assisted RSF mitigation could be an energy-efficient method for controlling RSF towards sustainable FO applications.
... Fertilizers as DS in FO is beneficial as it eliminates the DS regeneration after FO with the diluted DS being used for fertigation; this saves energy and hence cost [29]. Urea (NH 2 CONH 2 ) is the most commonly used fertilizer. ...
Chapter
As industrialization and urbanization are escalating, so is the water resources scarcity and pollution problem as well as energy demand. Urbanization and development have been a great threat to the water resources and play a major role in water pollution problem if not planned in a sustainable way. Nowadays, more focus is on water recycling and reuse. Forward osmosis (FO) is an emerging technology providing a great alternative approach compared to conventional water/wastewater treatment techniques. FO works on the principle of differential osmotic pressure of feed solution, FS (low osmotic potential) and draw solution, DS (high osmotic potential) with no hydraulic pressure and low fouling. FO has been applied in various industrial applications, viz. food and beverage, textile, oil and gas and pulp and paper, etc. Many FO membranes and DSs of desired characteristics have been developed and studied. But, still, there are many challenges and issues that need to be considered and resolve. This paper provides the information on the FO process, membrane fouling, DS concept and applicability of the FO/FO-hybrid technology in the various sectors.
... However, with the innovation of DS regeneration technologies, DS may become less energy-intensive. Previous studies showed that using commercial fertilizer as DS in the FO system can reduce energy cost because of no need for regeneration [42,43], which inspired us using commercial fertilizer instead of NaCl in the future to further reduce energy consumption. When FO membrane is used as the separation membrane instead of MF or UF membrane in the anaerobic bioreactors, AnOMBRs would achieve relatively higher D-CH 4 collection than other anaerobic bioreactors with lower energy consumption, which has significance for energy recovery and mitigation of greenhouse gas emission. ...
Article
Dissolved CH4 (D-CH4) rejection by forward osmosis (FO) membranes requires systematically investigate to mitigate anaerobic effluents pollution and energy loss. In this study, effects of membrane materials, orientations and alginate fouling on dissolved CH4, H2 and CO2 rejections were evaluated. FO was further connected with UASB effluent (FO-UASB) to recover D-CH4 for the first time. Results showed that D-CH4 rejections by CTA-ES and CTA-NW membranes were above 99.99% in the active layer facing feed solution (AL-FS) and active layer facing draw solution (AL-DS) orientations. Dissolved H2 rejections (87.5%-92.3%) achieved higher than dissolved CO2 rejections (52.5%-73.8%) in AL-FS orientation which was attributed to dissolved gas permeability through FO. Alginate fouling layer improved dissolved H2 rejection while concentrative internal concentration polarization aggravated dissolved CO2 rejection by fouled CTA-ES membrane in AL-DS orientation. D-CH4 was successfully collected by FO-UASB in the synergy effect of FO rejection and liquid-to-gas mass transfer. The maximum total CH4 collection rate was 599.0 mg COD/(L·d) and 603.4 mg COD/(L·d) at 35 °C and 25 °C in the FO-UASB.
... Whilst their findings indicated CPs became more serious as DS concentration increased, these effects may be mitigated to a certain extent with increasing cross-flow velocity (CFV) i.e., from 5.56 to 11.11 cm/s [27], from 2.11 to 36.40 cm/s [28]. It has been found that fouling diminished by elevating CFV i.e., from 10.7 cm/s (Re = 615) to 32.1 cm/s (Re = 1936) [11] or from 6 to 24 cm/s [29]; however, this option will cause an increase in energy consumption [8,30]. Although the effect of CPs has been analyzed for the FO membrane process, e.g. ...
Article
The long-term performance of forward osmosis during simulated wastewater reclamation was investigated for 120 h operation with a focus upon the influence of flux on flux decline and the synergistic effect of fouling on concentration polarization. Our comprehensive investigation focused on different fluxes (25; 30; 34 LMH) for simulated wastewater containing either a high protein or a low protein fraction. Compared to an initial flux of 25 LMH, operation at an initial 34 LMH favored the formation of a thicker and more compact cake layer which resulted in significant increase in both cake structural parameter (four-fold) and cake layer enhanced concentration polarization (ten-fold). After 40 h operation without physical cleaning the additional effect of cake layer enhanced concentration polarization and fouling resistance consumed 25% of the total driving force; the significant internal concentration polarization still had the greatest impact. In contrast operation at the lower flux of 25 LMH generated less fouling with a lower cake structural parameter (119 μm). The resultant flux decline was only 3% in contrast to the 15–18% found for the higher flux of 34 LMH. For operation above an initial 30 LMH it was found that FO fouling became irreversible if the wastewater contained a high protein fraction. Overall for a thin film composite membrane and a wastewater with a foulant concentration of 160 mg/L an initial flux of 25 LMH is the recommended threshold; this is 25% less that the critical value determined in earlier short-term studies.
... Recirculation pumps also consumed a large proportion of the SEC, which was estimated at 25-30% [101]. He et al. [7,104] found that the energy consumption for recirculation pumps could be reduced by decreasing the recirculation flow rate. However, the reduced water flux of the FO membrane and increased fouling caused by a lower recirculation flow rate should be considered when determining an optimal recirculation flow rate. ...
Article
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The application of membrane technologies for wastewater treatment to recover water and nutrients from different types of wastewater can be an effective strategy to mitigate the water shortage and provide resource recovery for sustainable development of industrialisation and urbanisation. Forward osmosis (FO), driven by the osmotic pressure difference between solutions divided by a semi-permeable membrane, has been recognised as a potential energy-efficient filtration process with a low tendency for fouling and a strong ability to filtrate highly polluted wastewater. The application of FO for wastewater treatment has received significant attention in research and attracted technological effort in recent years. In this review, we review the state-of-the-art application of FO technology for sewage concentration and wastewater treatment both as an independent treatment process and in combination with other treatment processes. We also provide an outlook of the future prospects and recommendations for the improvement of membrane performance, fouling control and system optimisation from the perspectives of membrane materials, operating condition optimisation, draw solution selection, and multiple technologies combination.
... where λ = 1.541 nm, n = 1, d is the crystal lattice spacing between interlayer ACTF sheets and θ is the peak of the diffraction angle (Xiang et al., 2017). ...
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Activated carbon thin film (ACTF) with a 3D laminated structure and single corn thickness shows the advantage of purifying water by stacking in a continuous membrane. However, it is necessary to find a suitable method for improving the separation quality of ACTF composite. The full-scale development process has also resulted in membrane damage, and consequentially, it has needed to be solved where it will be public economic problems. In this paper, an assembled ACTF thin-film composite membrane (CM) designated to succeed in the general performance of desalination in addition to nanocellulose filler will enhance the prepared membrane’s self-healing properties. The membrane was characterized by SEM, mechanical testing, FTIR, XRD, Raman spectroscopy, thermal analysis, AFM and wettability testing. The mechanical properties of the thin-film nanocellulose membrane (TFC@ACNCE membrane) were systematically investigated for their effects on the ACTF and nanocellulose content. The inserted ACTF thin-film CM gifted the channels using properties of the molecular sieving and, simultaneously, effectively extended the channel space of the membrane. Mechanical tests show that ACTF nanofillers are also enhanced by the addition of bending power, flexural modulus and Shore D composite membrane hardness. The improved damping, thermal and mechanical properties of the composite membrane may be due to the uniform distribution, by the three-dimensional interconnected porous network structure and by its strong interfacial adhesion at the nanofiller–matrix interface, of graphene sheets in the supporting matrix of polysulfones. The selective cellulose layer can adsorb water to allow the reaction of the cross-linking reaction autoself-healing. The prepared CM of ACTF and cellulose nanoparticles displays enhanced water flux (160 L m–2 h–1), which increased 34.5% than the blank membrane’s flux of water. That membrane shows a 99% rejection ratio that improved its anti-fouling efficiency. Moreover, the healed composite TFC@ACNCE membrane can desalinate seawater with enhanced flux stability at high pressures over blank membranes used to desalinate brackish water through a facile autoself-healing process.
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In this work, the feasibility of air bubbling for membrane fouling control in submerged direct forward osmosis system for treating municipal wastewater was systematically evaluated. The effect of air flow rate was first investigated and 3.0 m3/(m2·h) was identified as the optimum value in the experiments. After 52 days of operation, a significantly improved water flux performance was exhibited under air bubbling condition. In the absence of air bubbling, a dense fouling layer formed on the surface of membrane was containing large amounts of bacteria, organic matters and inorganics. However, when air bubbling was employed, substantially reduced accumulation of foulants on the surface of membrane was achieved. The results indicated that air bubbling underneath the membrane could alleviate the deposition of foulants and inhibit the formation and development of fouling layer on the surface of membrane effectively. Therefore, air bubbling could be considered as a simple and effective method for alleviating membrane fouling in submerged direct forward osmosis system.
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This study systematically investigated phenol removal from water and phenol fouling of membranes in forward osmosis (FO) using thin film composite (TFC) polyamide and AgCl mineralized thin film composite (MTFC) membranes. The influence of operating parameters (membrane orientation, phenol concentration, draw solution concentration, pH and ionic strength) on phenol rejection and phenol adsorption to membrane were investigated to elucidate the phenol transport behaviors in FO process. Overall, phenol rejection improved with increased draw solution concentration or feed solution pH. At a feed solution pH of 11, TFC membranes exhibited their highest phenol rejection of 97.0% and MTFC membranes exhibited their highest phenol rejection of 98.8%. Phenol adsorption on membrane surface may be related to the solute hydrophobic character, electrostatic interaction and reverse salt diffusion. Six-hour fouling experiments show that the phenol fouling of FO membranes is reversible and easily cleaned by physical flushing. Additionally, the MTFC membranes have an increased flux and rejection for phenol in FO than the TFC membranes.
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There has been increasing attention in osmotically driven membrane processes (ODMPs), which include forward osmosis (FO) and pressure retarded osmosis (PRO). They provide a sustainable solution against water and energy scarcity issues by utilizing the osmotic pressure difference between two water bodies, feed (low salinity) and draw solution (high salinity), across a semipermeable membrane. Indeed, their main applications, water treatment (e.g., desalination and wastewater treatment) and power generation, facilitate resource recovery from wastewaters. This review updates the recent development of FO and PRO by providing a comprehensive review on their fundamentals, membrane properties, potential applications as well as advanced techniques. In addition, economic analysis and environmental impacts are critically reviewed to highlight their feasibility and sustainability. Resource recovery from wastewaters (e.g., water, nutrient and energy) using FO and PRO is also discussed followed by their commercialization and future trends in order to push forward laboratory research to full-scale commercialization.
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The potential for concentrated fertilizer to drive water treatment, nutrient recovery, and/or power generation has received increased attention. Recently the concept of fertilizer-driven pressure retarded osmosis (or “Green PRO”) was introduced to the literature and experimentally validated. The limits of power from fertilizer osmosis however have not yet been established, and therefore the potential for this energy source to supply meaningful farm loads is uncertain. In this paper, a combination of analytical, numerical, and experimental methods are used to establish the thermodynamic and process limits of fertilizer energy conversion via PRO. The results indicate that up to 125 Wh/kg of energy is released from fertilizer when it is diluted in water. PRO process dynamics including operation at constant applied pressure, and the need to maintain high power levels throughout the batch process, limit the conversion to work to up to 14.9 Wh/kg. Further, experimentally-calibrated simulation results suggest that only up to 6.8 Wh/kg can be anticipated when considering non-ideal transport dynamics such as reverse solute flux and concentration polarization. The effect of feed source concentration and recovery ratio on batch process dynamics are investigated, and it is found that using wastewater as feed may be comparable to scenarios where high recovery of clean irrigation feed is used. The potential of common hydroponic plant crops is evaluated, and results indicate that advances in membrane technology may allow energy recovery to approach 5% of typical greenhouse electricity consumption.
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Forward osmosis as a water treatment option has been extensively studied in the recent past owing to its energy efficiency and enhanced performance. Even hybrid options of integrating forward osmosis with other separation technologies have been explored. In this article, forward osmosis has been comprehensively reviewed with reference to various process and engineering aspects viz., membranes, membrane fouling, contactors and their design, draw solutions, integration of forward osmosis with various other separation technologies and modeling and simulation. Every aspect has been thoroughly reviewed and discussed in terms of development trends besides presenting future challenges and prospects.
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Forward osmosis (FO) has attracted growing attention in the field of membrane-based separation technology over the last two decades. Despite recent advancements in various osmosis-assisted processes, few studies have succeeded in commercialization. This paper reviews the state-of-the-art developments of FO membrane, limitation analysis, and commercial proper applications. First, the development of FO technology in terms of FO membranes, FO draw solution (DS), and FO systems is reviewed. Based on a literature database survey spanning 1965-2020, current limitations of FO, particularly in terms of DS regeneration, energy consumption, and scale-up implementation, are identified to overcome the obstacles to commercialization. The key applications of the FO membrane process in commercial sectors are further classified into three configurations (i.e., osmotic dilution, osmotic concentration, and simultaneous osmotic dilution and concentration), and their successful applications are discussed. Since industrial demonstrations of simultaneous osmotic dilution and concentration are in progress, we believe that FO technology with no need for DS regeneration will be commercialized soon in the future.
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The potential for concentrated fertilizer to drive water recovery via forward osmosis has received increased attention in recent years. Questions remain however about the quantities of water that can be recovered from batch processes, and how significant recovery volumes are relative to the overall water balance of crops. In this study, we establish the thermodynamic and practical limits of recovering water from a fertilizer osmosis batch process, and thereby provide insights into the future prospects of this concept. It is shown that common fertilizers can recover between 112 and 138 l/kg via fertilizer osmosis from a municipal wastewater feed source while maintaining practical flux of at least 5 l m⁻² h⁻¹. The effects of membrane type, feedwater concentration, and permeate to feed recovery ratio are analyzed with a combination of analytical, numerical, and experimental methods. Water recovery limits are compared against the irrigation requirements of hydroponic crops. Between 32 and 99% of a plant's irrigation water can be supplied by fertilizer osmosis at competitive flux levels, provided that low concentration feed such as municipal or hydroponic wastewater is available. Such recovery volumes represent a significant portion of the plant water balance, and should justify future research in the area of fertilizer osmosis.
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Water scarcity is one of the main constraints for agriculture sector in many countries. It pushes the farm- ers to use wastewater for irrigation as an available alternate, especially in peri-urban areas of developing countries. One of the drawbacks of using wastewater for irrigation is heavy metal pollution in the soil and water along with the toxic elements which enter into the food chain. This study aims at to obtain information about the socio-economic reasons for using wastewater from the farmers’ perspective and analyze the accumulation of heavy metals in wastewater, canal water, underground water, soil and crops, irrigated with wastewater. Two contrasting views were observed among the farmers about wastewater irrigation. Over 90% preferred to use wastewater due to its low cost and rich source of nutrients. Although, farmers know that wastewater irrigation have serious negative effects on human health and the quality of the ground water, they prefer to use it for lowering the cost of production and overcome the scarcity of canal water. The findings of this study showed that, ground water and canal water have more accu- mulation of Cr, Mn, Pb and Zn than the recommended safe limits. None of the water samples collected from different sources was found to be safe for irrigation due to heavy metal contamination. Wastewater irrigated crops and vegetables were also analyzed to determine the bioaccumulation of heavy metals. Concentrations of Cr, Mn, Pb and Zn were observed more than safe limits in all the analyzed vegetables (spinach, cabbage, cauliflower, mustard leaves and round gourd) and crops (berseem, sorghum, maize, rice, wheat, lucerne, sugarcane). This study showed that poor economic conditions force the farmers to not only sacrifice their own health but also the health of consumers of these crops and vegetables by using wastewater for irrigation.
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Forward osmosis (FO) is one of the evolving membrane technologies in desalination with recent expanded new interest as a low energy process. The most significant parts of FO process are the membrane and draw solution since both play a substantial role in its performance. Hence, the selection of an appropriate membrane and draw solution is crucial for the process efficiency. Improvements in the development of membranes and draw solutes have been recorded recently. However, limitations such as fouling of FO membranes, reverse solute flux, concentration polarization, and low permeate flux in standalone FO systems. This work targets the review of recent progress in FO, aiming on the prospects and challenges. It starts with addressing the advantages of the FO process. The crucial part of this review is a thorough discussion of hybrid FO systems, different FO membranes, and draw solutes available coupled with their effects on FO performance. Finally, the future of FO for sustainable desalination is also discussed.
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This study investigates the performance of an integrated osmotic and microfiltration membrane bioreactor (O/MF-MBR) system for wastewater treatment and reclamation. The O/MF-MBR system simultaneously used microfiltration (MF) and forward osmosis (FO) membranes to extract water from the mixed liquor of an aerobic bioreactor. The MF membrane facilitated the bleeding of dissolved inorganic salts and thus prevented the build-up of salinity in the bioreactor. As a result, sludge production and microbial activity were relatively stable over 60days of operation. Compared to MF, the FO process produced a better permeate quality in terms of nutrients, total organic carbon, as well as hydrophilic and biologically persistent trace organic chemicals (TrOCs). The high rejection by the FO membrane also led to accumulation of hydrophilic and biologically persistent TrOCs in the bioreactor, consequently increasing their concentration in the MF permeate. On the other hand, hydrophobic and readily biodegradable TrOCs were minimally detected in both MF and FO permeates, with no clear difference in the removal efficiencies between two processes. Crown Copyright © 2015. Published by Elsevier Ltd. All rights reserved.
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With the world’s population growing rapidly, pressure is increasing on the limited fresh water resources. Membrane technology could play a vital role in solving the water scarcity issues through alternative sources such as saline water sources and wastewater reclamation. The current generation of membrane technologies, particularly reverse osmosis (RO), has significantly improved in performance. However, RO desalination is still energy intensive and any effort to improve energy efficiency increases total cost of the product water. Since energy, environment and climate change issues are all inter-related, desalination for large-scale irrigation requires new novel technologies that address the energy issues. Forward osmosis (FO) is an emerging membrane technology. However, FO desalination for potable water is still a challenge because, recovery and regeneration of draw solutes require additional processes and energy. This article focuses on the application of FO desalination for non-potable irrigation where maximum water is required. In this concept of fertiliser drawn FO (FDFO) desalination, fertilisers are used as draw solutions (DS). The diluted draw solution after desalination can be directly applied for fertigation without the need for recovery and regeneration of DS. FDFO desalination can make irrigation water available at comparatively lower energy than the current desalination technologies. As a low energy technology, FDFO can be easily powered by renewable energy sources and therefore suitable for inland and remote applications. This article outlines the concept of FDFO desalination and critically evaluates the scope and limitations of this technology for fertigation, including suggestions on options to overcome some of these limitations.
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Forward osmosis (FO) is a novel and emerging low energy technology for desalination. It will be particularly more attractive, if the draw solution separation and recovery are not necessary after FO process. The application of this new concept is briefly described here in this paper for the desalination of saline water for irrigation, using fertilizer as a draw agent. Instead of separating the draw solution from desalinated water, the diluted fertilizer draw solution can be directly applied for fertigation. We report the results on the commonly used chemical fertilizers as FO draw solution. Based on the currently available FO technology, about nine different commonly used fertilizers were finally screened from a comprehensive list of fertilizers and, their performances were assessed in terms of pure water flux and reverse draw solute flux. These results indicate that, most soluble fertilizers can generate osmotic potential much higher than the sea water. The draw solutions of KCl, NaNO3 and KNO3 performed best in terms of water flux while NH4H2PO4, (NH4)2HPO4, Ca(NO3)2 and (NH4)2SO4 had the lowest reverse solute flux. Initial estimation indicates that, 1kg of fertilizer can extract water ranging from 11 to 29L from sea water.
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Using fertilizers as draw solutes in forward osmosis (FO) can accomplish wastewater reuse with elimination of recycling draw solute. In this study, three commercial fast-release all-purpose solid fertilizers (F1, F2 and F3) were examined as draw solutes in a submerged FO system for water extraction from either deionized (DI) water or the treated wastewater. Systematic optimizations were conducted to enhance water extraction performance, including operation modes, initial draw concentrations and in-situ chemical fouling control. In the mode of the active layer facing the feed (AL-F or FO), a maximum of 324 mL water was harvested using 1-M F1, which provided 41% of the water need for fertilizer dilution for irrigation. Among the three fertilizers, F1 containing a lower urea content was the most favored because of a higher water extraction and a lower reverse solute flux (RSF) of major nutrients. Using the treated wastewater as a feed solution resulted in a comparable water extraction performance (317 mL) to that of DI water in 72 h and a maximum water flux of 4.2 LMH. Phosphorus accumulation on the feed side was mainly due to the FO membrane solute rejection while total nitrogen and potassium accumulation was mainly due to RSF from the draw solute. Reducing recirculation intensity from 100 to 10 mL min−1 did not obviously decrease water flux but significantly reduced the energy consumption from 1.86 to 0.02 kWh m−3. These results have demonstrated the feasibility of using commercial solid fertilizers as draw solutes for extracting reusable water from wastewater, and challenges such as reverse solute flux will need to be further addressed.
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Fresh water scarcity has led to increased use of reclaimed wastewater as an alternative and reliable source for crop irrigation. Beyond microbiological safety, concerns have been raised regarding contamination of reclaimed wastewater by xenobiotics including pharmaceuticals. This study focuses on carbamazepine, an anticonvulsant drug which is ubiquitously detected in reclaimed wastewater, highly persistent in soil, and taken up by crops. In a randomized controlled trial we demonstrate that healthy individuals consuming reclaimed wastewater-irrigated produce excreted carbamazepine and its metabolites in their urine, while subjects consuming fresh water-irrigated produce excreted undetectable or significantly lower levels of carbamazepine. We also report that the carbamazepine metabolite pattern at this low exposure level differed from that observed at therapeutic doses. This "proof of concept" study demonstrates that human exposure to xenobiotics occurs through ingestion of reclaimed wastewater-irrigated produce, providing real world data which could guide risk assessments and policy design to ensure the safe use of wastewater for crop irrigation.
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Water management is an integral part of coal mining operations. Due to the constraints on releasing saline water, coal mines require additional water storage facilities and therefore seek to minimise their inventory of saline water. Adopting efficient treatment technologies on-site would minimise the risk of wet season run-offs, freshwater contamination and allow segregation of different qualities of water to enable greater water recycling. This study aims to evaluate the application of an integrated forward osmosis (FO) and reverse osmosis (RO) system with three different actual coal mine waters, containing various concentrations of sulphates and silica that are generally associated with scaling and fouling of membrane systems. Three different FO draw solutions, di-sodium hydrogen phosphate (DHSP), sodium hexametaphosphate (SHMP) and sodium lignosulphonate (SLS) were evaluated. Two different modes of integrating the FO and RO systems were identified. The integrated system was able to concentrate the brackish mine waters, recovering more than 80% of the volume of mine water and obtaining dischargeable quality treated water. Simple physical cleaning with clean water circulation was found to be effective in restoring the FO water flux. The osmotic gradient between two mine waters was also utilised to adopt mine water as a draw solution. The effect of solution temperature on stand-alone and integrated FO and RO systems was also evaluated. The combination of FO with RO provided a better performance than individual FO or RO in treating coal mine wastewater. The FO unit served as an effective pre-treatment system prior to RO and the integrated FO-RO systems has a strong potential to successfully eliminate conventional pre-treatment processes for RO.
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This short review summarizes our understanding and perspectives on FO and PRO processes and meaningful R&D in order to develop effective and sustainable FO and PRO technologies for water reuse and osmotic power generation.
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This study focuses on the performance of an integrated forward osmosis (FO) and membrane distillation (MD) process for wastewater reuse. FO worked as a pretreatment barrier to remove most contaminants in the feed water and MD was used to recover the draw solutes from FO effluent and simultaneously produce high-quality reusable water. A unique three-channel FO–MD membrane module was designed and built to test water flux and contaminant removal in bench-scale experiments. It was found that the integrated FO–MD system possessed inherent flux balancing mechanism that enabled a stable and equal water flux for both FO and MD membranes for effective recovery of draw solution over long-term experiments. The FO–MD system was able to achieve more than 3 logs (>99.9%) removal of ammonium, COD, arsenic, and combined solutes in both synthetic and real wastewaters. Such a synergistic integration of FO and MD membrane processes offers three major advantages. First, the upstream FO process removes most contaminants and foulants from the feed solution, thus potentially diminishing the fouling and wetting problem for the downstream MD process. Second, the downstream MD process successfully recovers the draw solution for the FO process, enabling a constant water flux for FO. Third, the synergistic removal capability of FO and MD enabled the production of extremely high-quality product water. Additional benefits of the integrated process include ambient pressure operation and potential use of renewable low-grade heat as the energy source.
Article
Reverse flux of ammonium draw solute is a serious problem for applying forward osmosis (FO) in water/wastewater treatment. In this study, anaerobic ammonium oxidization (anammox) was synergistically linked to FO for removal of reverse-fluxed ammonium, thereby creating an osmotic anammox system. The feasibility of this system was demonstrated through both batch and continuous operation, and the anammox process was developed in two stages: sole anammox and nitritation-anammox. With addition of nitrite, the sole anammox process achieved an effluent ammonium concentration of 9.9±9.5mgNL-1. The nitritation-anammox maintained an ammonium concentration of 3.1±4.2mgNL-1, and increased the water flux to 2.46±0.24LMH (Lm-2h-1) compared with the sole anammox (1.90±0.14LMH). The nitritation-anammox process exhibited advantages over anammox process in assisting the FO with respect to water flux improvement and chemical savings. The osmotic anammox system can be linked to previously developed microbial electrolysis cells that recover ammonium from high-strength wastes as a draw solute for FO operation. The results encourage further investigation of this system for effects of organic residues, decreasing nitrate accumulation, understanding biofilm on the FO membrane, and long-term performance with actual waste.
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Forward osmosis (FO) is one of the evolving membrane technologies in desalination with recent expanded new interest as a low energy process. The most significant parts of FO process are the membrane and draw solution since both play a substantial role in its performance. Hence, the selection of an appropriate membrane and draw solution is crucial for the process efficiency. Improvements in the development of membranes and draw solutes have been recorded recently. However, limitations such as fouling of FO membranes, reverse solute flux, concentration polarization, and low permeate flux in standalone FO systems. This work targets the review of recent progress in FO, aiming on the prospects and challenges. It starts with addressing the advantages of the FO process. The crucial part of this review is a thorough discussion of hybrid FO systems, different FO membranes, and draw solutes available coupled with their effects on FO performance. Finally, the future of FO for sustainable desalination is also discussed.
Article
Osmotic membrane bioreactor (OMBR) is an emerging technology using water osmosis to accomplish separation of biomass from the treated effluent; however, accumulation of salts in the wastewater due to water flux and loss of draw solute due to reverse salt flux seriously hinders OMBR development. In this study, a hybrid OMBR-Electrodialysis (ED) system was proposed and investigated to alleviate the salinity buildup. The use of an ED (3 V applied) could maintain a relatively low conductivity of 8 mS cm-1 in the feed solution, which allowed the OMBR to operate for 24 days, about 6 times longer than a conventional OMBR without a functional ED. It was found that the higher voltage applied to the ED, the smaller area of ion exchange membrane was needed for salt separation. The recovered salts by the ED were successfully reused as a draw solute in the OMBR. At energy consumption of 1.88-4.01 kWh m-3, the hybrid OMBR-ED system could achieve a stable water flux of about 6.23 LMH and an efficient waste salt recovery of 1.26 kg m-3. The hybrid OMBR-ED system could be potentially more advantageous in terms of less waste saline water discharge and salt recovery, compared with an OMBR+RO system. It also offers potential advantages over the conventional OMBR+post ED treatment in higher water flux and less wastewater discharge.
Article
This study investigated membrane fouling and biomass characteristics during water extraction from mixed liquor of an aerobic bioreactor by a submerged forward osmosis (FO) system. As the sludge concentration in the reactor increased from 0 to 20 g/L, fouling of the FO membrane increased but was much less severe than that of the microfiltration membrane. The results also indicate that aeration can be used to effectively control membrane fouling. By increasing the draw solute concentration, as expected, the initial water flux was increased. However, there appears to be a critical water flux above which the higher initial water flux was associated with considerably more severe membrane fouling. A short-term osmotic membrane bioreactor experiment showed the build-up of salinity in the bioreactor due to the reverse draw solute transport and inorganic salts rejection by the FO membrane. Salinity build-up in the bioreactor reduced the permeate flux and sludge production, and at the same time, altered the biomass characteristics, leading to more soluble microbial products and less extracellular polymeric substances in the microbial mass. Additionally, the inhibitory effects of the increased salinity on biomass and the high rejection capacity of FO also led to the build-up of ammonia and ortho-phosphate in the bioreactor.
Article
The effects of feed solution pH and membrane orientation on water flux and the rejection of carbamazepine and sulfamethoxazole were investigated using a bench scale forward osmosis (FO) system. Water flux was pH-dependent in both membrane orientations. In addition, water flux increased while the specific reverse salt flux and hydrogen ion flux decreased with increasing feed solution pH. Water flux was lower in the normal FO mode compared to that in the pressure retarded osmosis (PRO) mode because osmotic pressure differential was reduced due to the internal concentration polarisation (ICP) phenomenon. The rejection of neutral carbamazepine was generally pH independent in both membrane orientations. The rejection of carbamazepine in the PRO mode was lower than that in the FO mode due to the higher concentration gradient caused by concentrative ICP in porous supporting layer. Steric hindrance was probably the main separation mechanism for the neutral carbamazepine in the FO process. On the other hand, the rejection of sulfamethoxazole was significantly affected by the feed solution pH in both membrane orientations. Variation in the rejection sulfamethoxazole could be attributed to the electrostatic repulsion between the negatively charged FO membrane surface and varying effective charge of the sulfamethoxazole molecule.
Article
Performance of forward osmosis (FO) process is significantly affected by factors such as membrane properties, concentration polarization (CP), and fouling. In this study, FO performance of a plate and frame type membrane is investigated via a numerical simulation based on mass conservation theorem. To evaluate the FO membrane performance, permeate flux and recovery rate are simulated according to membrane orientation, flow direction of feed and draw solutions, flow rate, and solute resistivity (K). In the case of membrane orientation, all-inside case, in which the draw solution faces the active layer, displays a relatively higher performance than all-outside and all-up cases. Notably, the membrane performance is highly affected by K indicating the extent of the internal CP. During the simulation approach, the spatial variation of the concentration profile was observed on a 2-dimensional membrane area; it was expected to cause a high diffusion load on a particular area of membrane, due to the relatively higher flux at that location. Moreover, it can result in unexpected fouling in a specific area on a membrane. Accordingly, the findings in this study suggest that the numerical simulation can be applied to optimize both physical properties and operation conditions, thereby ensuring cost-effective operation of FO processes.
Article
Forward osmosis (FO) is one of the emerging membrane technologies which has gained renewed interest recently as a low energy desalination process. The central to FO process is the draw solution (DS) and the membrane because both play a substantial role on its performance. Hence, the selection of an appropriate DS is crucial for the process efficiency. Many DS have been tested so far for a wide range of modern applications and this paper aims to review the various aspects of the DS in the process performance and provides valuable information regarding the selection criteria of suitable DS. Several general DS properties such as the osmotic pressure and the water solubility can affect the process performance. Other intrinsic properties to specific novel DS such as the emerging magnetic nanoparticles (MNPs) can also have an impact on the process efficiency and have to be evaluated. Separation and recovery of the DS are one of the major challenges facing the development of FO process. The recovery process should not be energy intensive, otherwise the FO process cannot be comparable with other pressure-driven processes. Thermolytic solutions such as ammonia carbonates are considered as the promising DS for desalination applications; however, their recovery process efficiency relies on the availability of low-grade heat. MNPs are emerging and effective DS for desalination and can be readily recovered by a magnetic field or conventional membrane processes. However, the aggregation of MNPs due to their magnetic properties has been issued. The vast numbers of studies on the use of NaCl as DS for the treatment of impaired water open up the possibilities of using seawater or reverse osmosis brine streams as suitable DS for such purpose. Fertilisers were also suggested as DS for seawater and wastewater treatment when the diluted DS can be used directly for irrigation. The development of an adequate and efficient DS coupled with a low-cost energy recovery system is crucial to the performance of the process and to achieve success for the large scale of FO.
Article
A model was developed for realizing the theoretically predicted performance of a forward osmosis (FO) system with an asymmetric membrane. The developed model has the capability to describe significant physical processes occurring in the FO system, such as reverse draw solute flux and internal (ICP) and external concentration polarization (ECP). The model was verified using existing experimental data and was used to investigate the effect of operating conditions such as cross-flow velocity and solute concentrations of both feed and draw solutions. It was found that the effects of the reverse draw solute flux and ECP were not negligible for predicting the water flux in some operating conditions, such as in a feed solution with a high solute concentration. However, previous FO modeling studies have generally assumed that their effects are insignificant. The effect of ECP increases with the solute concentration of the feed solution. The cross-flow directly affects the diffusion of the solute on the surface of the membrane and the ECP change could possibly affect ICP in the support layer. In this study, the simulation result confirmed the effect of the cross-flow on ECP, ICP, and water flux. These phenomena can simultaneously be simulated by the model developed in this study. © 2012 Elsevier B.V.
Article
Forward osmosis is recognized as one of the promising membrane based desalination process and viable alternative to reverse osmosis as a lower cost and more environmentally friendly desalination technology. The solution of ammonium bicarbonate was used as a draw solution to extract water from a feed containing 0.5 M sodium chloride. The water was transported from feed to draw solution and it can be recovered upon moderate heating of the draw solution, which is decomposed into ammonia and carbon dioxide gases producing pure water. The mechanism of water transport in the case of feed containing pure water or sodium chloride has been elucidated depending upon the orientation of the membrane. The concentrative and dilutive internal concentration polarizations played a major role in a situation when feed was towards support layer and feed was towards active layer, respectively. For the desalination applications, the feed towards support layer was found to be best mode to achieve higher flux. An increase in draw solution concentration from 1.0 to 3.6 M, resulted in an increase in flux values from 0.58 to 1.39 × 10− 6 m3m− 2 s− 1 at 30 °C. Further, an increase in temperature of the draw solution from 30 to 45 °C resulted in increase in transmembrane flux from 1.39 to 2.11 × 10− 6 m3m− 2 s− 1 at the highest draw solution concentration. It was concluded that forward osmosis can prove to be a feasible technique for the recovery of water from saline water.
Article
The purpose of this short communication is to share our perspectives on future R & D for FO processes in order to develop effective and sustainable technologies for water, energy and pharmaceutical production.Research Highlights► A review of current and future FO technologies for water, energy and pharmaceuticals.
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Osmosis is a physical phenomenon that has been extensively studied by scientists in various disciplines of science and engineering. Early researchers studied the mechanism of osmosis through natural materials, and from the 1960s, special attention has been given to osmosis through synthetic materials. Following the progress in membrane science in the last few decades, especially for reverse osmosis applications, the interests in engineered applications of osmosis has been spurred. Osmosis, or as it is currently referred to as forward osmosis, has new applications in separation processes for wastewater treatment, food processing, and seawater/brackish water desalination. Other unique areas of forward osmosis research include pressure-retarded osmosis for generation of electricity from saline and fresh water and implantable osmotic pumps for controlled drug release. This paper provides the state-of-the-art of the physical principles and applications of forward osmosis as well as their strengths and limitations.
Article
In fertilizer-drawn forward osmosis (FDFO) desalination, the final nutrient concentration (nitrogen, phosphorus, potassium (NPK)) in the product water is essential for direct fertigation and to avoid over fertilization. Our study with 11 selected fertilizers indicate that blending of two or more single fertilizers as draw solution (DS) can achieve significantly lower nutrient concentration in the FDFO product water rather than using single fertilizer alone. For example, blending KCl and NH(4)H(2)PO(4) as DS can result in 0.61/1.35/1.70 g/L of N/P/K, which is comparatively lower than using them individually as DS. The nutrient composition and concentration in the final FDFO product water can also be adjusted by selecting low nutrient fertilizers containing complementary nutrients and in different ratios to produce prescription mixtures. However, blending fertilizers generally resulted in slightly reduced bulk osmotic pressure and water flux in comparison to the sum of the osmotic pressures and water fluxes of the two individual DSs as used alone. The performance ratio or PR (ratio of actual water flux to theoretical water flux) of blended fertilizer DS was observed to be between the PR of the two fertilizer solutions tested individually. In some cases, such as urea, blending also resulted in significant reduction in N nutrient loss by reverse diffusion in presence of other fertilizer species.
Energy consumption of the FO system with three types of the feed solution: DI water, secondary effluent and primary Effluent. The draw was 25% fertilizer solution with a recirculation flow rate of 25 mL min À1. Error bars represent the standard deviation of three measurements
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Fig. 6. Energy consumption of the FO system with three types of the feed solution: DI water, secondary effluent and primary Effluent. The draw was 25% fertilizer solution with a recirculation flow rate of 25 mL min À1. Error bars represent the standard deviation of three measurements.