569 research outputs found
Membrane desalination and water re-use for agriculture: State of the art and future outlook
Membrane-based desalination technologies for agricultural applications are widely applied in many countries around the world. Sustainable and cost-effective desalination technologies, such as reverse osmosis (RO), membrane distillation, forward osmosis, membrane bioreactor, and electrodialysis, are available to provide treated water, but the pure water product does not contain the required level of nutrients to supply agricultural fields. This can be overcome by the use of blended water to meet the required quality of irrigation water for crop production, which is expensive in areas lacking in freshwater resources. The adoption of a hybrid system offers many advantages, such as generating drinking water and water enriched with nutrient at low cost and energy consumption if natural power is used. This review focusses on summarizing the current and recent trends in membrane desalination processes used for agricultural purposes. The challenges being faced with desalinating seawater/brackish water and wastewater are discussed. A specific focus was placed on the viability of hybrid desalination processes and other advanced recovery systems to obtain valuable irrigation water. A comparison between various membrane desalination technologies in terms of treatment efficiency and resource recovery potential is discussed. Lastly, concluding remarks and research opportunities of membrane technologies are analyzed. We concluded that the ED process can be utilized to minimize the energy requirements of other membrane technologies. The MD coupled with ED system can also be utilized to generate high quality irrigation water at low energy requirement. The FO-ED hybrid system exhibited excellent performance and very low energy consumption as compared to other hybrid systems
Unlocking the application potential of forward osmosis through integrated/hybrid process
Study of forward osmosis (FO) has been increasing steadily over recent years with applications mainly focusing on desalination and wastewater treatment processes. The working mechanism of FO lies in the natural movement of water between two streams with different osmotic pressure, which makes it useful in concentrating or diluting solutions. FO has rarely been operated as a stand-alone process. Instead, FO processes often appear in a hybrid or integrated form where FO is combined with other treatment technologies to achieve better overall process performance and cost savings. This article aims to provide a comprehensive review on the need for hybridization/integration for FO membrane processes, with emphasis given to process enhancement, draw solution regeneration, and pretreatment for FO fouling mitigation. In general, integrated/hybrid FO processes can reduce the membrane fouling propensity; prepare the solution suitable for subsequent value-added uses and production of renewable energy; lower the costs associated with energy consumption; enhance the quality of treated water; and enable the continuous operation of FO through the regeneration of draw solution. The future potential of FO lies in the success of how it can be hybridized or integrated with other technologies to minimize its own shortcomings, while enhancing the overall performance
Forward osmosis membranes and processes: A comprehensive review of research trends and future outlook
Recently, Forward Osmosis (FO) desalination process has been widely investigated as a potential technology that could minimize the drawbacks of traditional desalination processes. To review the past, current, and future research scope of the FO desalination process, a statistical analysis that gives insights on the FO topics of interest is needed to assist researchers in the development of the FO technology. The main objective of this work is to conduct a survey highlighting the general and specific research trends in FO technology topics. The level of research interest is quantified based on the number of publications in each area collected from Science Direct and Scopus databases from 1999 to 2020. This survey indicated an increasing number of publications on the FO processes and membranes technology. The topics of interest are fouling phenomenon, draw solutions, membrane fabrication and modification. Some potential research areas highlighted in this review to help researchers to further advance the FO technology. This review reveals that recycling the draw solution and energy consumption are the most important research areas that have shown growth in the number of publications over the last eight years. An increase of publications was also found in the treatment of the organic matter over the last decade. To further promote FO process in industry, developing FO membranes, optimizing the energy consumption, and establishing an effective recovery system are the most essential topics. Thus, the interest in this process is expected to be continued in the future
GreenPRO: A novel fertiliser-driven osmotic power generation process for fertigation
© 2018 This study introduces and describes GreenPRO, a novel concept involving fertiliser-driven osmotic energy generation via pressure retarded osmosis (PRO). The potential of GreenPRO was proposed for three objectives: (a) power generation, (b) water pressurisation for fertiliser-based irrigation, and (c) water treatment, as a holistic water-energy-food nexus process. Three pure agricultural fertilisers and two commercial blended fertiliser solutions were used as the draw solution and irrigation water as feed to test this concept for power generation. Theoretical thermodynamic simulation of the maximum extractable Gibbs energy, was first performed. After which, a series of bench-scale experiments were conducted to obtain realistic extractable energy data. The results showed that concentrated fertilisers potentially have 11 times higher energy than seawater. Even after accounting for the irreversibility losses due to constant pressure operation, the investigated pure fertilisers were found to have between 2.5 and 4.6 Wh/kg of energy. The outcomes from the flux and power density modelling were then validated with real experimental data. This study has successfully demonstrated that concentrated fertilisers can release a substantial amount of chemical potential energy when diluted for fertigation. This energy could be harnessed by transforming it into electric energy or pressure energy via PRO
Groundwater desalination using forward Osmosis in Egypt
Rapid population growth is putting huge stress on limited fresh water sources in Egypt. Agriculture is considered the major consumer of fresh water in Egypt, consuming more than 80% of fresh water available. Creating new freshwater sources for irrigation purposes becomes inevitable to meet the increasing demand. Groundwater desalination could be the solution to this problem. If a low-cost sustainable desalination technology is realized, impact on the agricultural sector would be remarkable for water stressed country like Egypt. Forward Osmosis (FO) is an innovative membrane separation technology that can be applied to efficiently desalinate groundwater. FO desalination relies on the theory of natural osmotic pressure driven by concentration difference instead of hydraulic pressure in RO (Reverse Osmosis). Thus, desalination can be achieved using significantly low energy. FO desalination process involves the use of a concentrated draw solution (DS), generating elevated osmotic pressure, flowing on one side of a semi-permeable FO membrane, and a feed solution (FS), with a lower osmotic pressure, flowing by the other side. Fresh water leaves the FS and enters the DS by natural diffusion. The diluted DS is then separated from the fresh water and draw solutes are recovered. One application of FO process is Fertilizer Drawn Forward Osmosis (FDFO). This application offers a unique advantage as separation and recovery of draw solute is not essential since the draw solution adds value to the end product. The convenience of FDFO desalination is that produced water can be directly utilized for fertigation because fertilizers are needed anyway for the plants avoiding the need for separation and recovery of draw solutes. However, FDFO desalination has some limitations that should be considered. Novel draw solutions and capable FO membranes are the main concern of most FO researchers as both greatly affect overall process efficiency. The high nutrient content in product water is another limitation making meeting irrigation water quality standards a challenge. Applying FDFO technology in Egypt for augmenting irrigation water by desalinating abundant brackish groundwater is investigated in this work. As Egypt is a groundwater-rich country, application of FDFO desalination technology would lead to a revolutionary platform where unutilized brackish groundwater can be efficiently made use of to generate valuable nutrient-rich irrigation water. Egyptian irrigation schemes and mapping of groundwater aquifers in Egypt have been carefully investigated. Based on a carefully studied selection criteria, two proposed locations are suggested for this application in Egypt: 1) Nile Valley and Delta region and 2) Red Sea coast in Eastern Desert and Sinai region. In Nile valley and Delta region, it is suggested to apply FDFO technology coupled with localized irrigation instead of flood irrigation. The suggested technique could possibly cultivate 1 million feddan using renewable groudnwater. Proposed scheme will lead to a healthier Nile River and is expected to eventually minimize further soil salinization being a reported problem in the area which negatively affects crop yield In Red Sea coast in Eastern Desert and Sinai region, FDFO desalination is a promising technology to help alleviate the severe water scarcity problem inhibiting the area’s development. Already existing RO facilities could be easily integrated to the suggested FDFO technology. In this study it is suggested to have decentralized small-scale farms, instead of hundreds of thousands of feddan as is common in Delta and Nile valley regions. This will minimize water losses and keep the desalinated water at a competitive price. FDFO desalination success is greatly affected by the choice of a suitable draw solution. This study focused only on nitrogenous-based fertilizers being by far the most dominant class of fertilizers used in Egypt. Four nitrogenous Egyptian fertilizers have been closely evaluated with respect to their availability, economics and performance. The three factors played a major role in the fertilizer selection. Ammonium Sulpahte was selected to be the most suitable fertilizer draw solution exhibiting high osmotic pressure, being non-expensive, non hygroscopic, resistant to valorization, highly soluble in water and containing sulphur which is needed by the plant. Performance of ammonium sulphate DS was then tested experimentally. The FO membrane used was thin film composite (TFC) membrane supplied by Woongjin, Korea and fhe FS was synthetic salty water prepared using different concentrations of NaCl. A bench-scale FO setup was used to run the experiments. The performance was assessed based on water flux, reverse permeation and feed ions rejection at different DS concentration. It is concluded that there is a logarithmic correlation between flux and ammonium sulphate concentration where any additional increase in ammonium sulphate concentration inhibits water flux due to dilutive internal concentration polarization (DICP) effects. Increasing FS concentration leads to flux decline due to the drop in the differential bulk osmotic pressures between DS and FS. Specific Reverse Solute Flux (SRSF) values at flux less than 10 Lm-2h-1 is significantly higher than that for flux more than 10 Lm-2h-1. As a result, it is recommended to operate the process at a flux exceeding 10 Lm-2h-1 to avoid undesired loss of draw solute by reverse permeation. SRSF is almost constant irrespective of ammonium sulphate DS concentration. For the same DS concentration, flux and SRSF are inversely proportional. Except when operated at low ammonium sulphate concentration and high FS concentration, the TFC membrane used in this study exhibited high rejection of FS ions for almost all DS concentrations (more than 90%). To sensibly test the efficiency of the ammonium sulphate draw solution, a real brackish Egyptian groundwater sample was collected, analyzed and used as FS. Being available, three FO membrane samples were assessed in this part of the study and the best membrane was selected for further investigations. In comparison to HTI’s Cellulose Triacetate (CTA) and Woongjin TFC membranes, Porifera’s commercial membrane proved to be best membrane with respect to baseline flux, where DS was NaCl and FS was DI water. Having the smallest structural parameter (S), internal concentration polarization (ICP) is minimized yielding highest flux. Different concentrations of ammonium sulphate were used as DS using the BGW sample. Like previously, the performance was assessed based on water flux, reverse permeation and feed ions rejection. A logarithmic relation was drawn between water flux and ammonium sulphate concentration. Same relation existed between ammonium sulphate concentration and water flux due to DICP effects. However, in this study, SRSF values did not exceed 0.18 g/l for both NH4+ and SO42- ions, indicating high membrane selectivity. At flux exceeding 20 Lm-2h-1, NH4+ ion reported higher SRSF values than that of SO42− ion.. Again, SRSF came out to be almost constant irrespective of ammonium sulphate concentration. While increasing draw solution concentration lead to increasing Na+ ion rejection, it caused a significant decline in Cl- ion rejection. This phenomenon could be probably associated to an ion exchange mechanism and reversal of membrane surface charge. In conclusion, FDFO is a promising technology that could possibly alleviate the water scarcity problem in Egypt. Not only is FDFO a sustainable desalination technology, but also it has numerous advantages over conventional desalination technologies. Abundant brackish groundwater could be efficiently exploited to produce valuable nutrient-rich irrigation water, being the major fresh water consumer in Egypt. The scheme studied demonstrated that ammonium sulphate is an efficient DS for FDFO process, especially using Porifera’s commercial FO membrane, exhibiting high osmotic pressure, low reverse solute permeation and remarkable rejection of feed solute. The proposed scheme could lead to a technology platform that would supply supplementary irrigation water, reduce soil salinity, manage fertilizer application and close the irrigation – brackish water – drainage vicious loop
Environmental sustainability of forward osmosis: The role of draw solute and its management
Forward osmosis (FO) is a promising technology for the treatment of complex water and wastewater streams. Studies around FO are focusing on identifying potential applications and on overcoming its technological limitations. Another important aspect to be addressed is the environmental sustainability of FO. With the aim to partially fill this gap, this study presents a life cycle analysis (LCA) of a potential full-scale FO system. From a purely environmental standpoint, results suggest that significantly higher impacts would be associated with the deployment of thermolytic, organic, and fertilizer-based draw solutes, compared to more accessible inorganic compounds. The influent draw osmotic pressure in FO influences the design of the real-scale filtration system and in turn its environmental sustainability. In systems combining FO with a pressure-driven membrane process to recover the draw solute (reverse osmosis or nanofiltration), the environmental sustainability is governed by a trade-off between the energy required by the regeneration step and the draw solution management. With the deployment of environmentally sustainable draw solutes (e.g., NaCl, Na2SO4), the impacts of the FO-based coupled system are almost completely associated to the energy required to run the downstream recovery step. On the contrary, the management of the draw solution, i.e., its replacement and the required additions due to potential losses during the filtration cycles, plays a dominant role in the environmental burdens associated with FO-based systems exploiting less sustainable draw solute, such as MgCl2
On the potential of forward osmosis to energetically outperform reverse osmosis desalination
We provide a comparison of the theoretical and actual energy requirements of forward osmosis and reverse osmosis seawater desalination. We argue that reverse osmosis is significantly more energy efficient and that forward osmosis research efforts would best be fully oriented towards alternate applications. The underlying reason for the inefficiency of forward osmosis is the draw-dilution step, which increases the theoretical and actual energy requirements for draw regeneration. As a consequence, for a forward osmosis technology to compete with reverse osmosis, the regeneration process must be significantly more efficient than reverse osmosis. However, even considering the optimisation of the draw solution and the benefits of reduced fouling during regeneration, the efficiency of an optimal draw regeneration process and of reverse osmosis are unlikely to differ significantly, meaning the energy efficiency of direct desalination with reverse osmosis is likely to be superior
Fertilizer drawn forward osmosis process for sustainable water reuse to grow hydroponic lettuce using commercial nutrient solution
© 2017 Elsevier B.V. This study investigated the sustainable reuse of wastewater using fertilizer drawn forward osmosis (FDFO) process through osmotic dilution of commercial nutrient solution for hydroponics, a widely used technique for growing plants without soil. Results from the bench-scale experiments showed that the commercial hydroponic nutrient solution (i.e. solution containing water and essential nutrients) exhibited similar performance (i.e., water flux and reverse salt flux) to other inorganic draw solutions when treating synthetic wastewater. The use of hydroponic solution is highly advantageous since it provides all the required macro- (i.e., N, P and K) and micronutrients (i.e., Ca, Mg, S, Mn, B, Zn and Mo) in a single balanced solution and can therefore be used directly after dilution without the need to add any elements. After long-term operation (i.e. up to 75% water recovery), different physical cleaning methods were tested and results showed that hydraulic flushing can effectively restore up to 75% of the initial water flux while osmotic backwashing was able to restore the initial water flux by more than 95%; illustrating the low-fouling potential of the FDFO process. Pilot-scale studies demonstrated that the FDFO process is able to produce the required nutrient concentration and final water quality (i.e., pH and conductivity) suitable for hydroponic applications. Coupling FDFO with pressure assisted osmosis (PAO) in the later stages could help in saving operational costs (i.e., energy and membrane replacement costs). Finally, the test application of nutrient solution produced by the pilot FDFO process to hydroponic lettuce showed similar growth pattern as the control without any signs of nutrient deficiency
An integrated fertilizer driven forward osmosis- renewables powered membrane distillation system for brackish water desalination: a combined experimental and theoretical approach
Utilization of an integrated forward osmosis-solar powered membrane distillation system can provide a promising method for brackish water desalination. In this study, the brackish water feed and fertilizer draw solutions were operated in a forward osmosis process to generate irrigation water for agriculture. Forward osmosis was also selected as membrane distillation pre-treatment to avoid fouling and wetting of the membrane distillation membrane. Subsequently, the diluted draw solutions were treated in the membrane distillation system to recover the initial osmotic pressure and to obtain a final distillate permeate. The experimental results revealed that the modified forward osmosis membrane exhibited slightly better performance in terms of maximum water flux, minimum reverse solute flux and high water recovery of 53.5%. In the membrane distillation process, an optimum water flux of about 5.7 L/m2. hr and high rejection rate of about 99.55 % were achieved at an optimum temperature of 60 oC. Modelling was applied to investigate the feasibility of using a solar collector to power the membrane distillation system and hence limit energy costs. By using renewable energy, we calculate that the energy consumption of the hybrid system could be reduced by 67%. Membrane distillation-solar powered system can achieve optimum energy consumption recoded as 1.1 kWh. We concluded that the diluted fertilizer draw solution can be used as an irrigation water after further dilution by an available water source. By using forward osmosis prior to membrane distillation process, the membrane distillation membrane showed less fouling and wetting leading to excellent rejection rate and acceptable distillate permeate. The energy consumption of the forward osmosis-solar powered membrane distillation system was lower than that for reverse osmosis stand-alone system. The findings of this work could be used to develop guidelines for the optimal design of industrial forward osmosis-membrane distillation system
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