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Abstract Increased water demand and increased drought episodes in the Middle East and other regions necessitate an expansion in desalination projects and create a great market opportunity for photovoltaics PV. Fthenakis, Vasilis, Atia, Adam A. New prospects for PV powered water desalination plants: case studies in Saudi Arabia: New prospects for PV powered water desalination plants.
United States: N. Copy to clipboard. United States. Among the developments in material science which has got application through membrane-based desalination is the innovation of nanoparticles and nanocomposites that demonstrated an attractive desalination potential. These developments are being realized through the incorporation of conventional nanomaterials such as metal oxides, silica and zeolites to the conventional membrane systems.
Further, the emergence of carbon nanotubes and graphene-family nanomaterials are hoped to contribute to the sustainability of membrane-based desalination technology through their water flux enhancing and exceptional salt rejection property.
Mathematically, water flux across a membrane is inversely proportional to its thickness. Consequently, sustainable membranes are envisaged to be produced from advances in engineered nanomaterials including graphene Goh et al. In addition, Kwon et al. Schematic illustrating the process for the inclusion of controlled pores in a monolayer graphene membrane by ion bombardment followed by chemical oxidation Homaeigohar and Elbahri Scanning electron microscopy image of a porous, b dense, c asymmetric and d symmetric inorganic membrane Kayvani Fard et al.
Studies on produced water PW treatment using various ceramic membranes Kayvani Fard et al. Yet, researches are in progress to advance membrane materials to fit to the existing challenges.
Pathways and challenges for efficient solar-thermal desalination | Science Advances
Most of the researches are geared toward cost minimization, making it more environmentally friendly and efficient. Thus, surface coating on the active layer of an existing membrane, changing the synthesis material, enhancing antifouling and elevating surface hydrophilicity are some of the modifications to membranes Zou et al. The inadequate rejection of ions and small neutral solutes by polyamide RO membranes necessitated extensive post-treatment. Based on the literature, types of membrane fouling vary depending on the source of feed water Sachit and Veenstra The categories of foulants so far reported include colloids, inorganic particles, biological as well as other chemical species like iron, calcium and manganese, oil, and natural organic matter NOM , whose effect depends on the pH and electron potential of feed.
Thus, such raw water properties rose the interest on the mode of coupling. Continuous geometries of IXRs can be applied to pretreat water before membrane desalination. However, the most established industrial scale is the removal boron from RO permeate. In relation to that the regeneration of resin is relevant in coupling IX with membranes for desalination.
In this regard, the type of resin used determines the regeneration potential of the resin. Generally, the intensity and selectivity of a separation process is influenced by the type and specification of the product required to fit to the end user. In water treatment, advanced technologies are sought over the conventional separation technologies so as to meet the desired quality of the product or to selectively remove trace pollutants from the feed water.
For instance, the concentrations of boron and arsenic in geothermal water are much higher than the permissible limits for drinking purpose which required subsequent treatment to avoid the associated toxicity problem to consumers. According to Kabay et al. In addition to that, sorbents include zeolites also showed arsenic removal from geothermal water Kabay et al. Furthermore, emerging pollutants are not easily removed by the conventional wastewater treatment processes which include phenols and other pharmaceutical as well as cosmetic ingredients that are released to the wastewaters which ultimately end up in natural waters.
These recalcitrant pollutants are increasingly in use either as therapeutic or personal care products such as antiepileptics carbamazepine , tranquillizers diazepam , analgesics ibuprofen, naproxen, diclofenac , antibiotics roxithromycin, erythromycin, sulfamethoxazole, trimethoprim and three polycyclic musk fragrances galaxolide, tonalide, celestolide Reif et al. In view of that, there is a pressing need for developing novel technologies that can remove existing or emerging pollutants in water or wastewater and that are able to meet the stringent environmental discharge limits or the tightening water quality regulations.
For instance, the selective removal of boron that usually occurs as boric acid H 3 BO 3 cannot be removed by the conventional water treatment systems.
As a result, the need for the application of hybrid systems is on the rise by both the industry and academia Eumine Suk and Matsuura Consequently, there are numerous studies that evaluate either the performance or the cost of a particular membrane technique. For instance, a recent review by Wang et al. A related work by Miyoshi et al. These researchers showed a reduction in surface water color to 0. Regarding the enhancement of transport or flux in desalination, Humplik et al. Choi et al. An earlier study by Taniguchi et al.
Abdulgader et al. These scholars argued that the ion-exchange resin IXR coupled with RO and UF membranes showed a synergistic effect in removing trace pollutants in water through improving efficiency and operational costs. Though they directed at further research especially on robustness and feasibility of such technique, they declared the promising future of such integration for reduction in desalination costs and membrane scaling Abdulgader et al.
Cornelissen et al. Venkatesan and Wankat In fact, boron separation is not the only focus in desalination. Li et al. While using NF in the presence of Na 2 SO 4 and NaCl at high concentration, negative chloride rejection is observed which is an opportunity on one side. Thus, NF concentrate has been applied to regenerate an exhausted IX resin that reportedly reduced the energy and cost implications of membrane processes especially that of RO Hilal et al.
Kabay et al. Further Kabay et al. Additionally, Kabay et al.
Besides the effect of amount of resin, the functional group of the resin is a significant factor in IX desalination pretreatment processes together with the feed salt concentration based on laboratory- and pilot-scale studies Hilal et al. The future of hybrid technology appears promising even beyond desalination.
As time goes, ion-exchange membrane process is modifying especially depending on the particular type of pollutant to be removed. A recent study by Siekierka et al. These test level study demonstrated not only a reduction in energy but also membrane area consumption. Further process optimization is not multivariate in most case, and much of the studies are conducted on a batch system at a laboratory scale. Therefore, multivariate optimization on a continuous flow mode, using regenerable resin is a challenge to be tackled in the future.
Furthermore, Al-Mamun et al. The review reports that simultaneous electrical energy generation is possible during microbial desalination through bioelectrochemical oxidation of organics present in wastewater. However, practically membrane fouling problem persisted with other technical issues Al-Mamun et al. Furthermore, a life cycle assessment of the microbial desalination cell technology argued the high environmental impact of the technology particularly due to its global warming potential Yang et al.
Ion-exchange—membrane hybrid separation is a full-scale process by application especially for potable water supply. Ion-exchange coupled membrane processes are effective in removing hardness, nitrate, heavy metals and other emerging pollutants from water and wastewater at least on a pilot scale including boron. The membrane—ion-exchange pairing studies done so far are encouraging with regard to the cost implication of such hybrid processes especially in solving membrane fouling problem.
Further, the hybrid system is favorable regarding energy consumption and space use as compared to MFs alone including the double-pass RO. However, the real implication of the laboratory-scale studies on sustainability and feasibility needs further investigation that includes the cost of IX resin regeneration.
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Skip to main content Skip to sections. Advertisement Hide. High distilled water quality, high unit capacity and high heat efficiency are its most obvious characteristics [ 18 , 19 ]. In addition, MED has traditionally been used in the industrial distillation sector for the evaporation of juice from sugarcane in the production of sugar and in the production of salt using the evaporative process. The MED process, like MSF, takes place in a series of vessels or evaporators called effects, and it also uses the principle of evaporation and condensation by reducing the ambient pressure in the various effects.
This process permits the seawater feed to undergo multiple boiling without supplying additional heat after the first effect. The seawater enters the first effect and is raised to the boiling point after being preheated in tubes. The seawater is sprayed onto the surface of the evaporator tubes to promote rapid evaporation. The evaporator tubes are heated by externally supplied steam, normally from a dual-purpose power plant.
Multi-effect distillation plant [ 30 ]. The MED plant's steam economy is proportional to the number of effects.
Status of hybrid membrane–ion-exchange systems for desalination: a comprehensive review
The total number of effects is limited by the total temperature range available and the minimum allowable temperature difference between one effect and the next effect. Only a portion of the seawater applied to the tubes in the first effect is evaporated. The remaining feed water is fed to the second effect, where it is again applied to a tube bundle. These tubes are in turn heated by the vapours created in the first effect. This vapour is condensed to form the fresh water product, while giving up heat to evaporate a portion of the remaining seawater feed in the next effect.
The process of evaporation and condensation is repeated from effect to effect, each at a successively lower pressure and temperature. This continues for, typically, 4—21 effects and a performance ratio between 10 and 18 is found in large plants [ 20 ]. This minimizes tube corrosion and the potential of scale formation around the tube surfaces [ 6 ].
The quality of the feed water is not as important as in the RO system technology.