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Fluidised bed crystalliser and air gap membrane distillation as a solution to geothermal water desalination* 1
Abstract
Tunisia has five major geothermal districts. Recorded hot spring temperatures range from 294 to 340 K with flow rates 0.1–10 2 L/s. In southern parts available groundwater resources are mostly hard and brackish (3 g/L). Recently, Tunisia has resorted to this resource for agriculture and potable water uses. Cooling towers have been built to lower down the temperature and hardness. Cooled brackish water irrigates greenhouses and feeds desalination plants. The cooling operation of groundwater rejects an important quantity of thermal energy in the atmosphere. However, energy requirements of thermal desalination plants are too excessive to be supplied by a geothermal resource. Membrane distillation (MD) is an emerged desalination technology, which can be driven by a thermal energy at low enthalpy (less than 363 K) as geothermal energy, and a fluidised bed crystalliser can ensure reduction of an important portion of hardness without significant loss of temperature. MD is realised by means of a microporous hydrophobic membrane separating a warm solution from the cooling chamber, which contains either liquid or gas. A fluidised bed crystalliser permits production of from it of a granular crystal calcium carbonate from the consumption rates of calcium ions, using aragonite or sand as seeding materials. The purpose of this paper is to realise experimental assembly constituted of fluidised bed crystalliser (FBC) and a cell of air gap membrane distillation (AGMD). It presents preliminary results related to characterisation of fluidised bed, growth of seeded particles size of CaCO 3 and operating parameters of AGMD. In laboratory scale, the technical feasibility has been shown. More investigation is needed to prove the efficiency and availability of coupled AGMD with FBC.
... Gude [31] also suggests that some desalination processes benefit not only from using waste heat from plants as a source of thermal energy but also from the possibility of using the thermal water itself as a feed stream. The concept of thermal water as a heat transmission medium and feed stream was applied to the membrane distillation process and reported by some authors, such as Bouguecha and Dhahbi [32] and Sarbatly and Chiam [9]. Despite being favorable to the MD-Fluished bed crystallizer (FBC) integration for thermal water desalination, the results of the work developed by Bouguecha and Dhahbi [32] indicate that only the sensible heat of geothermal wells is not enough to achieve high recovery values. ...
... The concept of thermal water as a heat transmission medium and feed stream was applied to the membrane distillation process and reported by some authors, such as Bouguecha and Dhahbi [32] and Sarbatly and Chiam [9]. Despite being favorable to the MD-Fluished bed crystallizer (FBC) integration for thermal water desalination, the results of the work developed by Bouguecha and Dhahbi [32] indicate that only the sensible heat of geothermal wells is not enough to achieve high recovery values. Therefore, it is suggested that increased efficiency can be achieved by complementing the supply of thermal energy through solar heating sources or by integrating it with other membrane processes such as reverse osmosis [32]. ...
... Despite being favorable to the MD-Fluished bed crystallizer (FBC) integration for thermal water desalination, the results of the work developed by Bouguecha and Dhahbi [32] indicate that only the sensible heat of geothermal wells is not enough to achieve high recovery values. Therefore, it is suggested that increased efficiency can be achieved by complementing the supply of thermal energy through solar heating sources or by integrating it with other membrane processes such as reverse osmosis [32]. ...
Membrane distillation (MD) is a promising process for high-quality water reclamation mainly due to its high capacity to retain non-volatile components and operate without the need for hydraulic pressure. However, its low energy efficiency limits its widespread use. With that in mind, this paper critically summarizes the different engineered configurations of membrane distillation coupled with renewable energy sources and waste heat, namely: solar, geothermal, and waste heat, to overcome the limitations associated with low energy efficiency commonly reported. From all sources, solar-driven processes are preferred due to the greater technological maturity related to flat plate collectors (FPCs), evacuated tube collectors (ETCs), compound parabolic concen-trators (CPCs), salt-gradient solar ponds (SGSPs), and solar stills. The integration with renewable energy sources represents one of the leading solutions for energy consumption, proving to be a decisive choice for the system's economic viability. The summarized studies suggest membrane distillation's potential to be economically competitive with the classical membrane separation process (ultrafiltration, nanofiltration, and reverse osmosis) when waste heat is considered for wastewater treatment. Even under these conditions, alternative energy sources have a few shortcomings to be investigated in future studies, such as short periods of solar radiation and the intermittence of waste heat sources. These factors still represent obstacles to an uninterrupted and large-scale operation of membrane distillation and must be overcome in a near future. Even so, successful case studies on full-scale systems that integrate membrane distillation and solar energy sources suggest the process's potential for widespread use in the near term.
... Compared with solar-powered systems, geothermal energy-driven MD can offer fresh water at lower production costs, and the process operation is less susceptible to intermittence, which is a typical issue for solar energy. However, the geothermal MD process has not been widely developed [3], and so far there have been only few studies on the MD desalination process powered by geothermal energy [48,49]. For example, Sarbatly et al. [48] evaluated the possibility of the geothermal energy-powered MD process for desalination purposes. ...
... The experimental results and economic analysis manifested that the MD process fed with geothermal saline water could produce drinking water with TDS below 119 ppm at the production cost of $0.5/m 3 , and using geothermal saline water feed helped reduce 90% of the MD process energy consumption. In another study, Bouguecha et al. [49] applied a hybrid MD-fluidised bed crystalliser process for the treatment of geothermal springs in Tunisia. The low-grade heat of the geothermal springs (i.e. ...
... temperature in the range 30-70°C) was exploited to thermally power the MD process, and the fluidised bed crystalliser was applied to reduce the hardness of the Additional heating to generate a 'T = 5 o C Fig. 2 Schematic diagram of the modified MD configurations with internal heat recovery. The latent heat of water vapour condensation is used to preheat the feed water stream prior to the evaporator channels, thus reducing the external thermal energy requirement geothermal springs [49]. The experimental results showed that the geothermal spring's hardness constrained the MD process water recovery due to the high risk of membrane scaling [49]. ...
Purpose of Review
Membrane distillation (MD) has been known as a promising water treatment process for many years. However, despite its advantages, MD has never been able to compete with other processes for industrial water treatment and supply. Instead, it has been orientated towards several unique strategic water treatment applications. This review aims to uncover the opportunities and technical challenges pertinent to the MD process and the current status of its strategic water treatment applications most notably including decentralised small-scale desalination for fresh water provision in remote areas, hybridisation with forward osmosis (FO) for treatment of challenging polluted waters, regeneration of liquid desiccant solutions for air conditioning, and treatment of acid effluents for beneficial reuse.
Recent Findings
Pilot and small-scale MD systems have been demonstrated for decentralised desalination using various renewable energy sources to supply fresh water in remote, rural areas and on ships where other desalination processes are inefficient or unfeasible. For this strategic desalination application, MD is technically viable, but more works on configuration modification and process optimisation are required to reduce the process energy consumption and water production costs. For the three other strategic applications, the technical viability of the MD process has been proved by extensive lab-scale researches, but its economic feasibility is still questionable due to the lack of large-scale evaluation and the uncertain costs of MD systems.
Summary
The orientation of MD towards strategic water treatment applications is clear. However, huge efforts are required to facilitate these applications at commercial and full scale.
... Many authors proposed the exploitation of residual geothermal brines to recover additional energy and/or water and minerals [13][14][15][24][25][26][27][28]. From the energy recovery point of view, the most concrete answer is offered by the organic Rankine cycles (ORCs), well-established systems capable of achieving acceptable efficiencies at low temperatures [29][30][31]. ...
... From the resource recovery point of view, many desalination processes (mainly thermal-based to exploit low-enthalpy sources) have been applied to geothermal brines, mainly for research and development purposes [14][15][16][17][18][25][26][27][28]. Thermal processes can be perfectly integrated with the residual heat from the geothermal plant. ...
... Depending on the composition and the recovery ratio, membrane processes face significant problems of scaling and fouling. Multi-effect evaporation/distillation (MED), multistage flash distillation (MSF), thermal and mechanical vapor compression (TVC/MVC) are the most studied processes; at lower temperature, membrane distillation and humidification-dehumidification can be interesting alternatives [17,[26][27][28][34][35][36][37][38]. ...
Geothermal brines can be a resource of energy, freshwater and minerals. Even when rejected after their exploitation to produce energy in a power plant, the brines can be a source of freshwater and minerals, and can have a residual enthalpy that can be recovered to produce additional power. The different reuse scenarios of these wasted brines depend on the composition and temperature at which they must be reinjected into the wells. On this basis, geothermal energy production is a perfect case study to investigate the water–energy nexus and to optimize the integrated energy- and water-production processes. In this paper, two case studies of brine reuse for both energy and water production are presented with the related process analysis, basic design and technical–economic analysis. A methodology to evaluate the exergy efficiency of the processes is presented by analyzing minimum work of separation, the maximum achievable work and the additional primary energy required for integrated production. The novel approach to estimate the process efficiency for integrated geothermal energy and desalination plants is applied to the case studies and discussed in light of literature results.
... This expectation is because geothermal systems do not need an energy converter [165]. However, there are few studies of geothermal-powered MD [165,166]. As an example, a simplified scheme of a MD system driven by geothermal energy is shown in Fig. 9. ...
... Bouguecha and Dhahbi [166] combined a fluidized bed crystallizer (FBC) with AGMD, with the aim of geothermal desalting. Although they obtained favorable preliminary results, they showed that the MD recovery fraction is not able to reach high values when using only the sensible heat from geothermal energy. ...
... Nonetheless, additional work needs to be done to demonstrate the reliability of MD powered by geothermal energy. Some of the challenges that need to be addressed are the effect of the feed solution chemistry (e.g., hardness) on the systems performance [167], and the investigation of long-term operation [166]. ...
... First, Lakerveld [66] demonstrated that energy consumption of membrane assisted crystallization is lower than that of conventional evaporative crystallization. Furthermore, the energy consumption of the MCr process can be reduced, for instance by integrating with solar energy, geothermal energy or other low-grade heat sources in the heating system [53,67,68]. ...
... It is evident the important contribution of the thermal supply needed in the membrane distillation and crystallization units, that significantly impacts the configurations where both brines are treated. Nevertheless, as proved also in other works [53,67], if the thermal energy is available freely, the SEC can be reduced to 1.96 kWh/m 3 and the water cost up to 0.54 $/m 3 thus, confirming the applicability of the desalination process with MCr units from both economical and energetic point of views. The beneficial effect of having thermal energy available in the system can also be found on the increase in exergy efficiency. ...
The fast growing of membrane systems in industrial applications suggests the dissemination of last results, particularly in the areas of strategic interest. In this contribution, the role of membrane engineering for more sustainable industrial cycles, following the Process Intensification strategy, is reported. The development of Membrane Crystallizers (MCr) with specific focus on their application to the treatment of brines is presented, together with the use of molecular dynamic simulation to help in the selection of the most appropriate membrane material. The potential of membrane reactors for CO2 valorization through new designs is also highlighted. Moreover, tools like exergy analyses and new metrics to compare the performance of membrane operations to conventional ones in the logic of Process Intensification are discussed.
... For each experiment, the feed water temperature is the one displayed on Figure 10. Parametric studies from the literature show that feed fluid temperature and flow rates have a significant effect on the MD permeate flux [52,53]. As shown in Figure 9, a direct interplay exists between these two parameters due to the coupling of the heat pump and the MD unit. ...
... Under these operating conditions, there is an optimal flow rate to produce fresh water. studies from the literature show that feed fluid temperature and flow rates have a significant effect on the MD permeate flux [52,53]. As shown in Figure 9, a direct interplay exists between these two parameters due to the coupling of the heat pump and the MD unit. ...
Heat pump systems can simultaneously produce cooling energy for space cooling in hotels, office and residential buildings and heat for desalination using membrane distillation (MD). The MD technique uses a heat input at a temperature compatible with the levels of heat pump condensers (<60 °C). A heat pump prototype coupled with an air-gap membrane distillation unit was constructed and tested. This paper presents the experimental study on a lab-scale prototype and details the two operating modes “continuous” and “controlled” simulating an air conditioning system and a food storage, respectively. The experimental results enable to analyze the performance of the prototype and the physical phenomena involved. Finally, the study shows that this system could be a promising solution to help supplying freshwater to people in hot regions of the world.
... In contrast to solar energy, there is a negligible daily or seasonal shift associated with a geothermal energy source; however, it is quite variable depending upon the geographical location. There are very few studies that presented the concept of either geothermal energy driven MD system or MD for geothermal water purification using DCMD, AGMD and VMD [72]- [75]. Geothermal energy driven MD systems are specified for the locations where geothermal fields are present, and there is a need to obtain potable water and/or water for crop irrigation (due to critical water shortage and contaminated available water). ...
... Geothermal energy driven MD systems are specified for the locations where geothermal fields are present, and there is a need to obtain potable water and/or water for crop irrigation (due to critical water shortage and contaminated available water). The temperature range for geothermal energy can be between 40-95 • C. The considered locations include Cerro Prieto in Mexico, Momotombo in Nicaragua and Lake Poopó in Bolivia [72]; Ranau, Sabah in Malaysia [73]; Masson Greenhouse in New Mexico [74] and Tunisian geothermal springs [75], [76]. Considering warm geothermal water can save up to 95% of the total energy consumption of the MD system [73]. ...
The European Union has placed a high priority on reaching the goals described in the 2030 Agenda for Sustainable Development. This aim has provided added momentum to member-state environmental regulatory authorities to further tighten the discharge limits of industrial wastewater. These measures strongly influence existing industrial practices as many traditional wastewater treatment methods cannot achieve these strict release limits. Moreover, industrial sectors are encouraged to employ a zero liquid discharge strategy for advanced wastewater management, particularly for process water reuse. Emphasis is thus now placed on improved water treatment systems to recover, reuse and release water in a manner that protects natural resources, guarantees stringent regulatory constraints and ensures financial viability. In this context membrane distillation (MD) is a
promising industrial wastewater treatment technology capable of meeting these requirements while utilizing low-grade heat sources.
This thesis focuses on experimental investigations and techno-economic analysis of waste heat driven MD systems for water purification in two water-intensive industries: nano-electronics facilities and cogeneration plants. Samples collected at relevant facilities were tested in an air gap MD bench unit and a semi-commercial pilot plant, with a focus on separation efficiency and potential for achieving high recovery ratios. For the techno-economic analysis of the industrial scale system, the performance of the chosen semi-commercial unit was considered to evaluate the full-scale system operation in terms of thermal energy demand and expected water purification cost. Various thermal integration approaches were investigated while considering locally available heat sources to realize the energy requirements of the specific MD system. The selected case studies include: removal of tetramethylammonium hydroxide (TMAH) from photolithography process wastewater in nano-electronics industries; treatment of chemical mechanical planarization (CMP) process wastewater in nano-electronics industries; and water recovery through advanced flue gas condensate treatment from municipal solid
waste incineration and biofuel fired cogeneration plants.
The results from nano-electronics wastewater treatment tests showed that high quality
permeate could be recovered while observing good to excellent separation efficiencies of analyzed contaminants. Moreover, the proposed advanced flue gas condensate treatment is also proved successful while removing the pollutants up to the concentration levels of parts per billion. The proposed pretreatment step, pH adjustment of MD feeds, enhanced ammonia removal efficiency in all cases. Compared to current practices, the separation efficiencies of the considered MD based processes are improved. The simulation results indicate that the required thermal energy for operating large scale MD systems is readily available via internal waste heat sources of nano-electronics facilities for handling typical
volumes of the mentioned wastewaters. In cogeneration plants, district heating supply and return lines are well suited as the heat source and heat sink to manage industrial-scale MD systems effectively. The process economy shows that the unit water treatment cost is mainly constrained by thermal energy cost. In case when the price of heat is considered negligible, the unit water treatment cost is significantly lower than the competing technologies.
... MD units are well suited to be coupled with geothermal fluids; however, geothermal energy has rarely been examined in MD (Sarbatly and Chiam, 2013). Technical feasibility of assembly constituted of fluidized bed crystallizer (to reduce hardness) and a cell of AGMD driven by geothermal energy has been demonstrated in lab-scale (Bouguecha and Dhahbi, 2003). However, MD recovery fraction was unable to reach a high value using only a sensible heat from a geothermal well (Bouguecha and Dhahbi, 2003). ...
... Technical feasibility of assembly constituted of fluidized bed crystallizer (to reduce hardness) and a cell of AGMD driven by geothermal energy has been demonstrated in lab-scale (Bouguecha and Dhahbi, 2003). However, MD recovery fraction was unable to reach a high value using only a sensible heat from a geothermal well (Bouguecha and Dhahbi, 2003). To address this issue, two options can be envisaged. ...
One of the rapidly advancing areas in water treatment is membrane distillation which is a hybrid separation process, enjoying thermal evaporation and membrane separation advantages simultaneously. Recently, by the rapid progress in membrane science, membrane distillation has attracted a surge of interest in academia by numerous experimentalists and theoreticians. The highlight of membrane distillation technique is the potential to implement as a renewable energy-driven operating system, mostly solar and geothermal energy. This is an intelligent approach to mitigate the energy consumption of the process since water scarcity coincides with the abundant of solar and geothermal power in many arid and semi-arid areas. This chapter covers membrane distillation principles and its major characteristics as well as presenting a state-of-the-art review on integrating membrane distillation technique with solar collectors and geothermal technology for water treatment applications.
... Particularly, thermal energy need not be stored. Bouguecha and Dhahbi [15] experimentally studied the effect of feed conditions on the unit performance achieved using a fluidized bed crystallizer and AGMD driven by geothermal energy. AGMD exhibited a low recovery fraction compared with RO, suggesting that the use of MD with geothermal energy should be further studied. ...
... Fig. 10 depicts the simulation results for this configuration obtained using a Q p value of 2 L/m and the thresholds given by Eqs. (14) and (15). ...
A previously validated model for direct contact membrane distillation (DCMD) was used to analyze the performance of a process for desalinating geothermal saline water. The water recovery rate for a single DCMD unit is extremely low. Using several MD units arranged in series and array patterns increases pure water production. Another advantage of the cascade structure is that most of the geothermal energy associated with brackish water is utilized. The number of units that can be used in a series pattern is determined by the temperature difference between the exit brine and inlet permeate streams of an MD unit. The number of stages that can be used in an array pattern is determined by the temperature difference between the exit permeate and brine streams through out the stage. Simulations indicated that 51% water recovery can be achieved when 40 MD units are used in an array pattern. The analysis revealed a16% increase in water recovery when the feed salinity is reduced from 3.7% to 0.2%. In addition, the gained output ratio can reach a value of 9 when the entire exit permeate stream is recycled to the MD unit as a feed stream at the expense of additional waste of heat.
... It was proved that inorganic fouling not only altered the membrane's properties but also the MD performance (i.e., permeate flux and salt rejection) [41]. In order to prevent inorganic fouling, desalination can be carried out using a hybrid process, namely membrane crystallization, that combines both crystallization of salts and MD [70,[72][73][74][75]. In this hybrid process crystallization of salts is carried out in a separate tank and the formed crystals are eliminated leading to a conversion rate very close to 100% [73]. ...
... For the aerobic bacteria (pseudomonas faecalis) the operating conditions such as the high temperatures applied in MD are unfavorable to its growth. However, in the case of anaerobic bacteria (Streptococcus faecalis) and fungi (Aspergillus fungi) the high temperatures applied In order to prevent inorganic fouling, desalination can be carried out using a hybrid process, namely membrane crystallization, that combines both crystallization of salts and MD [70,[72][73][74][75]. In this hybrid process crystallization of salts is carried out in a separate tank and the formed crystals are eliminated leading to a conversion rate very close to 100% [73]. ...
Various membrane separation processes are being used for seawater desalination and treatment of wastewaters in order to deal with the worldwide water shortage problem. Different types of membranes of distinct morphologies, structures and physico-chemical characteristics are employed. Among the considered membrane technologies, membrane distillation (MD), osmotic distillation (OD) and osmotic membrane distillation (OMD) use porous and hydrophobic membranes for production of distilled water and/or concentration of wastewaters for recovery and recycling of valuable compounds. However, the efficiency of these technologies is hampered by fouling phenomena. This refers to the accumulation of organic/inorganic deposits including biological matter on the membrane surface and/or in the membrane pores. Fouling in MD, OD and OMD differs from that observed in electric and pressure-driven membrane processes such electrodialysis (ED), membrane capacitive deionization (MCD), reverse osmosis (RO), nanofiltration (NF), ultrafiltration (UF), microfiltration (MF), etc. Other than pore blockage, fouling in MD, OD and OMD increases the risk of membrane pores wetting and reduces therefore the quantity and quality of the produced water or the concentration efficiency of the process. This review deals with the observed fouling phenomena in MD, OD and OMD. It highlights different detected fouling types (organic fouling, inorganic fouling and biofouling), fouling characterization techniques as well as various methods of fouling reduction including pretreatment, membrane modification, membrane cleaning and antiscalants application.
... Membrane distillation (MD) coupled with crystallization (MDC) process is an important ZLD method which has attracted the interest of many scholars and institutes [3][4][5][6][7][8][9]. Membrane distillation modules are able to enrich the brine to a higher concentration than RO modules. ...
... Although the cooling crystallizers were used in all the previous MDC process research [3,[5][6][7][8][9]20] owing to the easy operation and low temperatures (close to room temperature), the salt and water production rate are quite low due to the insensitive variation of NaCl solubility against temperature as shown in Fig. 1. Reducing temperature can only slightly decrease the NaCl solubility. ...
... MD utilizes low-grade energy in the form of heat; therefore, renewable energy resources can supplement the energy required for MD. Numerous studies have combined MD with renewable energy resources, such as solar [4][5][6][7][8][9][10][11] and geothermal energy [12,13]. However, wind energy requires less capital and investment compared to other renewable energy sources, and large-capacity wind turbines are economically suitable for installation in arid regions, owing to their low land cost [14]. ...
In this study, various configurations involving parallel and series multi-stage direct contact membrane distillation (MSDCMD) were used to harness the waste heat of a wind turbine for freshwater production. A circulating fluid, which flowed around the wind turbine to cool its components, was heated as it flowed out of the wind turbine. The heat from the circulating fluid was transferred to seawater in a heat exchanger. The outlet seawater was utilized in parallel and series MSDCMD systems to retrieve freshwater and waste heat. Four configurations were proposed: Configuration 1 (a series MSDCMD with 1 × 15 modules), Configuration 2 (a parallel MSDCMD with 15 × 1 modules), Configuration 3 (a series–parallel MSDCMD with 3 × 5 modules), and Configuration 4 (a series–parallel MSDCMD with 5 × 3 modules). Configuration 1 achieved the highest permeate flux and water production, in the ranges of 13.4–70.5 kg/m²h and 1927–10,158 kg/h, respectively. However, Configuration 3 is the optimum configuration for achieving a higher gain output ratio (GOR) and evaporation efficiency (EE) and lower energy consumptions. In addition, the effects of the wind speed on the output parameters, that is, the permeate flux, water production, gain output ratio, evaporation efficiency, specific energy consumptions, and recovery ratio, were evaluated.
... MDC is generally used at temperatures ranging from 30 to 85°C, which is below conventional distillation 138 . This offers the possibility to use low-grade heat (e.g., solar and geothermal) or waste heat (e.g., surplus heat from industrial processes) for operation 139,140 , which can reduce the cost of the process significantly and also offers a "carbon-neutral" technique for processing different streams 141 . ...
The ocean has often been announced as a sustainable source of important materials for civilization. Application of the same extraction processes to desalination concentrate, rather than to unconcentrated seawater, will necessarily be more energetically favorable, so the expansion of seawater desalination in recent decades brings this dream closer to reality. However, there is relatively little concrete commercial development of ‘concentrate mining’. This review assesses the technical and economic prospects for utilization of commercially viable products from seawater. The most important technologies for economic use of products from desalination plant concentrate are technologies for more economic separation and technologies for more economic concentration. The most promising separation technologies are those, such as nanofiltration, which separate brine into streams enriched/depleted in entire classes of constituents with minimal input of energy and reagents. Concentration is becoming more economic due to rapid advances in Osmotically-Assisted RO technology. Despite very active research on many aspects of desalination concentrate utilization, it is likely that commercial development of the non-NaCl components of desalination brine will depend on the available market for NaCl, as the challenges and costs of extracting the other mineral components from bitterns in which they are highly enriched are so much less than those faced in direct treatment of brines.
... A system comprising a fluidized bed crystallizer (FBC) and an AGMD cell has provided new insights into the characterization of the fluidized surface, the development of the CaCO 3 seed particle size and the AGMD operational parameters. The technological viability has been demonstrated on the experimental scale (Bouguecha & Dhahbi, 2003). The effectiveness of two separate scale management strategies has been evaluated: a higher pH preconditioning system; and with an anti-scalant (AS) application, for RO concentration reduction in the laboratory-level AGMD. ...
The present water and energy crisis facing the world at
large with the ever-growing population is one that
demands careful attention by the research community.
The treatment of seawater and brackish water by
integrating renewable energy technologies into desalination
processes holds a promising future for availing
freshwater in areas of water scarcity across the globe.
This chapter captures the different desalination technologies
(such as thermal and membrane technologies) and
different renewable energy technologies (like solar, wind
and geothermal energies) that can be integrated into the
process of water treatment for salt removal. Utilizing
renewable energy technologies in desalination systems
will serve as alternative where grid electricity is not
available, reduce environmental pollution and cost.
... A system comprising a fluidized bed crystallizer (FBC) and an AGMD cell has provided new insights into the characterization of the fluidized surface, the development of the CaCO 3 seed particle size and the AGMD operational parameters. The technological viability has been demonstrated on the experimental scale (Bouguecha & Dhahbi, 2003). The effectiveness of two separate scale management strategies has been evaluated: a higher pH preconditioning system; and with an anti-scalant (AS) application, for RO concentration reduction in the laboratory-level AGMD. ...
Despite covering approximately 70% of the earth’s surface, the limited supply of clean water remains one of the major issues affecting the survival of humanity and the entire living beings and ecosystem. High salt content, high turbidity and salinity make water unsuitable for drinking and general use. Many technologies have been developed to attain clean and pure water appropriate for consumption. Desalination, a technique to remove salt and mineral components present in water, is an effective method in water treatment. Recently, membrane distillation that involves the utilization of hydrophobic membrane to accomplish filtration and purification across the membrane has gained huge attention. Divided into four major categories—direct contact, sweep gas, air gap and vacuum, membrane distillations are now commonly employed and effective for water desalination. Many innovative membrane hybrid systems have been developed to further improve the efficiencies and resolve the challenges especially to meet the needs of clean water-scarce region.
... Table 2 represents the en- Table 1 Scaling tendencies of various inorganic components present in mining brine (Nathoo and Randall, 2016 ergy requirements and mass balance of an MDCr system for achieving ZLD for seawater desalination under moderate operating conditions with a plant capacity of 3600 m 3 /h (1 m 3 /s) of seawater (Creusen et al., 2013). The high SEC associated with MDCr technology can be reduced by integrating heating modules with alternative energy sources such as geothermal energy, solar energy, or any other low-grade waste heat (Bouguecha and Dhahbi, 2003;Charcosset, 2009;Hogan et al., 1991). The cooling technique of crystallization commonly used in MDCr technology due to ease of convenience, when combined with MD, results in higher operational cost since MD operates at a temperature much higher than the cooling crystallization technology (Chen et al., 2014a;Creusen et al., 2013;Edwie and Chung, 2012;Julian et al., 2016). ...
Water resources are getting limited, which emphasises the need for the reuse of wastewater. The conventional waste(water) treatment methods such as reverse osmosis (RO) and multi-effect distillation (MED) are rendered limited due to certain limitations. Moreover, the imposition of stringent environmental regulations in terms of zero liquid discharge (ZLD) of wastewater containing very high dissolved solids has assisted in developing technologies for the recovery of water and useful solids. Membrane distillation crystallization (MDCr) is an emerging hybrid technology synergising membrane distillation (MD) and crystallization, thus achieving ZLD. MDCr technology can be applied to desalinate seawater, treat nano-filtration, and RO reject brine and industrial wastewater to increase water recovery and yield useful solids. This manuscript focuses on recent advances in MDCr, emphasizing models that account for application in (waste)water treatment. MDCr has dual benefits, first the environmental conservation due to non-disposal of wastewater and second, resources recovery proving the proverb that waste is a misplaced resource. Limitations of standalone MD and crystallization are discussed to underline the evolution of MDCr. In this review, MDCr's ability and feasibility in the treatment of industrial wastewater are highlighted. This manuscript also examines the operational issues, including crystal deposition (scaling) on the membrane surface, pore wetting phenomenon and economic consequences (energy use and operating costs). Finally, opportunities and future prospects of the MDCr technology are discussed. MDCr technology can amplify natural resources availability by recovering freshwater and useful minerals from the waste stream, thus compensating for the relatively high cost of the technology.
... A system comprising a fluidized bed crystallizer (FBC) and an AGMD cell has provided new insights into the characterization of the fluidized surface, the development of the CaCO 3 seed particle size and the AGMD operational parameters. The technological viability has been demonstrated on the experimental scale (Bouguecha & Dhahbi, 2003). The effectiveness of two separate scale management strategies has been evaluated: a higher pH preconditioning system; and with an anti-scalant (AS) application, for RO concentration reduction in the laboratory-level AGMD. ...
The present water and energy crisis facing the world at large with the ever-growing population is one that demands careful attention by the research community. The treatment of seawater and brackish water by integrating renewable energy technologies into desalination processes holds a promising future for availing freshwater in areas of water scarcity across the globe. This chapter captures the different desalination technologies (such as thermal and membrane technologies) and different renewable energy technologies (like solar, wind and geothermal energies) that can be integrated into the process of water treatment for salt removal. Utilizing renewable energy technologies in desalination systems will serve as alternative where grid electricity is not available, reduce environmental pollution and cost.
... A system comprising a fluidized bed crystallizer (FBC) and an AGMD cell has provided new insights into the characterization of the fluidized surface, the development of the CaCO 3 seed particle size and the AGMD operational parameters. The technological viability has been demonstrated on the experimental scale (Bouguecha & Dhahbi, 2003). The effectiveness of two separate scale management strategies has been evaluated: a higher pH preconditioning system; and with an anti-scalant (AS) application, for RO concentration reduction in the laboratory-level AGMD. ...
Several investigations have established that due to population expansion and land use, fresh water scarcity has increased tremendously placing immense burden on desalination process as the major alternative remedy to freshwater supply. The increase in problems related to energy across the globe due to exhaustibility of fossil fuels. Hence, there is a need to search for other sources of energy to meet up with the growing demand. Globally, the existing methods of desalination are not cost effective; hence, scientists are searching for alternative ways to reduce the financial burden in the setup of water desalination techniques. One of the suggested areas is in the utilization of microorganisms. One of the suggested methods is in the area of energy conservation, when using water to produce energy via utilization or engaging the use microbial desalination. Therefore, this chapter intends to provide comprehensive information on the application of microorganisms for the water desalination. Several types of microorganisms that could be applied for water desalination were also highlighted. The modes of action through which they exhibited their action were also discussed. The principles involved in the process of desalination were also elucidated.
... A system comprising a fluidized bed crystallizer (FBC) and an AGMD cell has provided new insights into the characterization of the fluidized surface, the development of the CaCO 3 seed particle size and the AGMD operational parameters. The technological viability has been demonstrated on the experimental scale (Bouguecha & Dhahbi, 2003). The effectiveness of two separate scale management strategies has been evaluated: a higher pH preconditioning system; and with an anti-scalant (AS) application, for RO concentration reduction in the laboratory-level AGMD. ...
... Water vapour passes across the membrane from the hot-brine side to the cool-permeate side. Bouguecha and Dhahbi [95] integrated AGMD with a fluidized bed crystallizer (FBC) to remove salt from geothermal water. They expressed their concerns over the low recovery fraction despite favourable results using geothermal energy. ...
Water and energy are critical components for human, and govern the growth and progress of societies. Desalination is an important process to meet ever-increasing water demand, although it is an energy-intensive alternative compared to conventional water treatment techniques. Demand for desalination has been expanded rapidly as traditional water sources are getting overexploited. Membrane distillation (MD) is a promising water treatment process for highly saline water, including reject from the reverse osmosis plants. To compensate for high energy requirement for the MD process, low-grade heat sources (such as waste heat or renewable sources) can be used. Limitations of other desalination processes are discussed in this review to underline evolution and tweaking of alternatives for making them optimal. In this review, we examine the suitability of the MD process for harnessing energy from different types of low-grade heat sources to make it cost-effective. Financial aspects of the MD process for different heat sources are also highlighted. A summary of studies focusing on hybrid MD systems is also provided. Finally, challenges, opportunities and current implementation of the MD process by using low-grade heat-based MD systems are discussed.
... An exception is an installation located in Greece, which desalts brackish water. The highest water desalination efficiency is characteristic for the installation based on membrane distillation and multi-effect distillation technologies located in Tunisia, for which the capacity is 1382 m 3 /day [87]. The second installation in Tunisia uses the humidification-dehumidification process (HDH), but the details are not known for it. ...
RE use in desalination of geothermal water for irrigation is reviewed. • A novel approach that integrates RESs into agri-food chain is presented. • Specific cases of geothermal water desalination from Turkey and Poland are given. • Possible new generation RESs in desalination by capacitive deionization are explored. • Advantages/disadvantages of RE use in geothermal water desalination are discussed. A B S T R A C T The agricultural sector, which is highly dependent on water, is urged to build on improved water management practices and explore available options to match supply and demand because of the water scarcity risks and a sustainable and productive agri-food chain. Geothermal water is an energy source used to generate electricity and/or heat. After harnessing its energy, the remaining water can be used as a water source for irrigation following treatment because of its high ionic content. Geothermal fields are mostly located in rural areas where agricultural activities exist. This would be a good match to decrease the transportation cost of irrigation water. The energy demand of the desalination process for agriculture is higher, requiring additional post-treatment processes. Fossil fuels to fulfill the energy requirements are becoming expensive, and greenhouse gas emissions are harmful to the environment. Thus, efforts should be directed towards integrating renewable energy resources into desalination process. This work focuses on presenting a comprehensive review of geothermal water desalination which is powered by renewable energy and provides specific cases from Turkey and Poland. Furthermore, possible new generation renewable energy systems in desalination are introduced, considering their potential application in the desalination of geothermal water for agricultural irrigation.
... An exception is an installation located in Greece, which desalts brackish water. The highest water desalination efficiency is characteristic for the installation based on membrane distillation and multi-effect distillation technologies located in Tunisia, for which the capacity is 1382 m 3 /day [87]. The second installation in Tunisia uses the humidification-dehumidification process (HDH), but the details are not known for it. ...
The agricultural sector, which is highly dependent on water, is urged to build on improved water management practices and explore available options to match supply and demand because of the water scarcity risks and a sustainable and productive agri-food chain. Geothermal water is an energy source used to generate electricity and/or heat. After harnessing its energy, the remaining water can be used as a water source for irrigation following treatment because of its high ionic content. Geothermal fields are mostly located in rural areas where agricultural activities exist. This would be a good match to decrease the transportation cost of irrigation water. The energy demand of the desalination process for agriculture is higher, requiring additional post-treatment processes. Fossil fuels to fulfill the energy requirements are becoming expensive, and greenhouse gas emissions are harmful to the environment. Thus, efforts should be directed towards integrating renewable energy resources into desalination process. This work focuses on presenting a comprehensive review of geothermal water desalination which is powered by renewable energy and provides specific cases from Turkey and Poland. Furthermore, possible new generation renewable energy systems in desalination are introduced, considering their potential application in the desalination of geothermal water for agricultural irrigation.
... The application of geothermal energy to power HDH and MD in Tunisia were reported in Refs. [119,120] respectively. Energy can also be converted to mechanical and electrical power for use in membrane desalination processes. ...
Reverse osmosis (RO) desalination has become a prominent desalination method for fresh-water production from either saline seawater or brackish water to meet the ever-growing demand for water, especially in water-scarce regions. Its integration with renewable energy sources (RES) reduces the environmental impact of carbon emission by conventional fossil fuel energy sources. The optimisation of the RES-RO desalination system is intended mainly to minimise total system cost and energy requirements and to guarantee system reliability. In this study, an extensive review of the optimisation of the RES-RO desalination system is presented based on optimal system sizing, optimal system operation and optimal thermodynamic analysis. RES such as geothermal, ocean, wind and solar energy and their hybrids were considered alongside desalination methods. Important findings of the review were discussed, and recommendations made for future work. Key recommendations of this study include the suggestion that extensive optimisation and analysis of a RES-RO system should utilise optimisation approaches that combine the sizing, operation and thermodynamic effect of the system. Future work should furthermore incorporate both economic and reliability indices in the formation of objective functions. Finally, demand response programmes can be introduced to the RES-RO system for demand side management. This has the potential of minimising system cost while maximising fresh-water production.
... Membrane distillation (MD) has served as a sustainable technology for the treatment of super-saline or brine wastewater generated largely from seawater reverse osmosis desalination plants [1][2][3][4][5], which is commonly discharged to sea, thus increasing pollution of the marine environment [6][7][8]. The performance of MD during brine treatment is influenced mostly by membrane wetting and loss of hydrophobicity [9,10] by membrane scaling and fouling on the top surface and interior pores [11,12]. ...
A robust dual-layer superhydrophobic and omniphobic electrospun nanofiber membrane was developed for membrane distillation application, especially with feed that contains surfactant and dissolved organic compounds. 1H, 1H, 2H, 2H-Perfluorooctyltriethoxysilane (FAS) functionalising of the electrospun polyvinylidene fluoride-co-hexafluoropropylene (E-PVDF-HFP) membrane, followed by surface grafting with FAS-functionalised zinc oxide (ZnO) nanoparticles, achieved low membrane water sliding angle with re-entrant morphologies on the membrane surface. Field-emission scanning electron microscopy with energy-dispersive X-ray images revealed the regular and uniform formation of re-entrant structures due to the ZnO nanoparticles. The optimised 25% w/w ZnO (ePFP-25Z) membrane achieved the highest contact angles for water (>161°), oil (131.5° ± 1.8°), ethanol (131° ± 2.9°), had the lowest surface energy (0.75 ± 0.43 mN m⁻¹) and high surface roughness (3.26 μm). The ePFP-25Z membrane maintained a stable membrane distillate flux and salt rejection (>99.9%) even after 80 h operation with 0.1 mM sodium dodecyl sulphate in super-saline solution (1 M NaCl). Anti-scaling and anti-wetting properties were illustrated in the presence of the dissolved organic compounds humic acid and alginate in super-saline feed.
... Multiple efforts have been made by different researcher to make this integration technically and economically optimized, to aware the society and to bring this geothermal driven desalination technology in competition with other renewables' driven [195À198]. As a result of these efforts, some geothermal driven desalination plants have been installed around the world: G MED and MSF desalination plant in Baja California, Mexico [199]; G A two stage MED in Kimolos, Greece [192]; G A HDH in Tunisia [200]; G MD coupled with multiple effect distiller in Tunisia [185]; G MED/VTE (2 effects) in Salton sea/ Imperial; MED/VTE (15 effects) Valley, United States [181,201]. ...
Energy, water and environment nexus is the backbone of sustainable future. Addressing these three nexus elements is a need of the time in concern with increasing threat of water scarcity, fuel depletion and CO2 emissions. Renewable energy (RE) resources are being integrated to power infrastructure. Similarly the process adopted to satisfy the drinkable water demand called desalination is needed to be driven by RE resources. This chapter starts with highlighting the importance and types of desalination. The global status of desalination technology in terms of installed capacity and research trends to make the systems more efficient is elaborated. The importance of energy, especially RE resources for desalination technology and desalination techniques driven by different RE resources are elaborated. Discussion is concluded with increased brine production associated with more drinkable produced water and reduced environmental emission due to the integration of RE resources with desalination techniques.
... with multiple effect distiller in Tunisia[185]; G MED/VTE (2 effects) in Salton sea/ Imperial; MED/VTE (15 effects) Valley, United States[181,201]. ...
In the past, attention has been created to use solar energy due to increased environmental pollution. Solar energy utilization through photovoltaic (PV) and thermal technologies is required to replace the conventional use of fossil fuels across the globe. Different types of solar PV (SPV) technologies utilizing the photons as input are driving the life of people. On the other hand, utilizing the solar heat for various applications is categorized as the solar thermal application which includes desalination, heating, cooling, cooking and power generation. Hence the objective of this work is to discuss the fundamentals, recent advancements and applications of different solar utilization technologies. The chapter is categorized into two major sections namely solar PV techniques and solar thermal techniques. In the first section SPV techniques, the principle, operation and recent advancements in the SPV system have been covered. In the second section solar thermal techniques, the principle, construction, working mechanism and current state of the art in recent research on solar collectors, solar cooling techniques, solar pond, solar cooking techniques and solar desalination have been addressed.
... with multiple effect distiller in Tunisia[185]; G MED/VTE (2 effects) in Salton sea/ Imperial; MED/VTE (15 effects) Valley, United States[181,201]. ...
Although renewable energy resources are more commonly used in the near future, there arises a requirement of integrating alternative storage options. Storing energy in terms of chemicals presents a promising approach for several reasons such as transportability, minimal losses and storage practices. In this aspect, hydrogen and ammonia are two of the carbon-free energy carriers, which can be used for energy storage purposes. Currently, hydrogen, and ammonia are dominantly produced by steam reforming of natural gas in the world. Hydrogen can also be produced through electrolysis or electrochemical processes. The Haber–Bosch process is the most common method to produce ammonia, whereas there are recently new alternatives to reduce the required temperature and pressure of the reaction through electrochemical cells. Ammonia as a sustainable fuel can be used in several kinds of combustion engines, gas turbines, burners with only small modifications and directly in fuel cells which is a very significant advantage compared to other types of fuels. In this work emerging hydrogen and ammonia production pathways, namely electrolysis and photoelectrochemical routes, are assessed in terms of sustainability by considering their (1) efficiencies, (2) environmental impact and (3) cost. Electrolysis is performed using either hydropower or wind power routes, whereas solar energy is used for photoelectrochemical hydrogen and ammonia production. In addition, the obtained results are compared with the conventional steam methane reforming method to signify the importance of emerging options.
... Bouguecha published the first literature on using a renewable energy source with an AGMD system. Large numbers of geothermal resources were intended to solve the irrigation and potable water issue by combining AGMD and a fluidized bed crystallizer (FBC) 168 together. Amali et al. suggested that there is less need for energy in AGMD systems and it is more adaptable than other configurations. ...
Membrane distillation provides a feasible and optimal solution to potable water issues. The literature contains a number of studies and research studies that aim to understand the behavior of membrane distillation systems and to provide the best possible solutions under different conditions. The purpose of this article is to discuss the air gap membrane distillation (AGMD) specifically and its development to date. The areas for future research in the field of AGMD are suggested. Membranes used in AGMD were discussed, including nanocomposite membranes and graphene membranes. In addition, the long-term performance issues regarding membrane fouling and scaling and the ways to prevent and to reduce them were discussed. Performance parameters that have not been explored sufficiently, such as energy efficiency and performance ratio, are discussed. Evolution of new membrane distillation processes from AGMD, such as the material gap and permeate gap, and conductive gap membrane distillation, is discussed. A generalized theoretical model for heat and mass transfer is presented for air gap membrane distillation systems. Coupling AGMD to form a hybrid combination with renewable energy sources is considered as a good answer to energy specific issues. Hybrid renewable energy systems with AGMD are discussed in detail. Novel designs for coupling AGMD systems with different forms of renewable energies are suggested, which presents an excellent area to be considered for developing advanced hybrid AGMD systems. It is suggested that future research should include economic studies, long-run system performance, operational problems and maintainance requirements, and related issues for better understanding and better acceptance of AGMD systems for industrialization.
... Among all potential energy resources used in MD, the geothermal was least explored and is less competitive in terms of current cost [47,206,207]. Hence, more intensive effort is needed to improve the process efficiency and decrease the WPC. ...
This chapter contains sections titled: Introduction Solar Desalination Direct Solar Desalination Indirect Solar Desalination Non‐Conventional Solar Desalination Solar Integration and Environmental Considerations Nomenclature
... Among all potential energy resources used in MD, the geothermal was least explored and is less competitive in terms of current cost [47,206,207]. Hence, more intensive effort is needed to improve the process efficiency and decrease the WPC. ...
This chapter contains sections titled: Introduction MD Concepts and Historic Development MD Transport Mechanisms Strategic Development for An Enhanced MD System Energy and Cost Evaluation in MD Innovations on MD Application Development Concluding Remarks and Future Prospects
... A geothermal resource was utilized for MD plant size of 17 l/day to reduce the unit production cost. The estimated cost was 13 $/m 3 [186]. In addition, geothermal water was filtered by VMD [187]. ...
Membrane distillation (MD) is a promising technology for treating saline water and wastewater with high rejection factors, which cannot be accomplished by conventional technologies. MD is a thermally driven separation process in which only the vapor molecules pass through a microporous hydrophobic membrane. The driving force in the MD process is the vapor pressure difference induced by the temperature difference across the membrane surface. This chapter provides a comprehensive study of MD. The first part gives an introduction, including general information about water problems, existing water technology, and historical review for MD. MD configuration and modules, membrane properties, and membrane characterization will be illustrated in the second and third parts. The transport phenomena relating to mass and heat transfer for different MD types are also presented. Operating parameters and MD application are covered in this chapter.
... A geothermal resource was utilized for MD plant size of 17 l/day to reduce the unit production cost. The estimated cost was 13 $/m 3 [186]. In addition, geothermal water was filtered by VMD [187]. ...
... In another work, a hybrid fluidized bed crystallizer (FBC) with AGMD was conducted for desalination of geothermal water [256] at a pilot plant level. A maximum flux value of 7.5 kg/m 2 h was obtained which is lower than the flux obtained from RO process (75 kg/m 2 h). ...
Membrane distillation (MD) is a promising thermally driven membrane separation technique. In MD,
water vapor is being separated from the hot feed water solution using a microporous hydrophobic
membrane, due to the difference in temperature, and hence vapor pressure, across the membrane.
Air gap membrane distillation (AGMD) process is one of the common configurations of applying the
MD process for water desalination and other applications. In AGMD, a stagnant air gap is introduced
between the membrane and a condensation surface within the membrane module to reduce the conduction
heat loss through the membrane. In this review article, design characteristics and operating
conditions of AGMD and its modified designs to enhance the productivity and reduce the energy
consumption are surveyed and discussed. Previous work on pilot AGMD systems and multi-stage or
multi-effect systems with energy saving modules is highlighted. Membrane materials and developments
used with the AGMD modules are presented with discussion of membrane fouling and scaling
problems. In addition, modeling techniques based on the heat and mass transfer equations and simulation
approaches of the AGMD process are presented. The merits of operating the AGMD systems
with solar and other renewable energies are discussed along with the economic aspects. The future
research directions of AGMD are highlighted in this review. This will help researchers to direct their
research without repetition of previous known studies.
... Greece Kimolos MED BW 80 [130] Tunisia Tunisia HDH SW $-$ [131] Tunisia Tunisia MD & MED SW 1382 [132] USA Salton sea MED/VTE(2) SW 18.9 [133] USA Salton sea ED/VTE(15) SW 79.5 [134] M.A. Abdelkareem et al. Desalination xxx (xxxx) xxx-xxx ...
Rapid population growth and industrial development have propelled water resources to the forefront of challenges facing modern societies. While water covers about two thirds of the surface of earth, <. 1% is suitable for domestic and industrial use. Conventional fossil-fuel powered desalination techniques consume extensive amounts of energy and have highly damaging impact on the environment. Abundant cheap and clean renewable energy sources are a promising alternative for powering modern desalination processes. In this work we review latest developments in the renewable energy systems to power desalination plants. The review focuses on desalination processes powered by solar, geothermal, wind, and ocean energy. Towards the end, the work also outlines existing challenges and makes recommendations about future directions.
... Eltawil et al. [17] stated that the main benefits of geothermal energy are related to its continuous and predictable supply. Bouguecha and Dhahbi [18] examined the influence of feed conditions on the performance of a fluidized bed crystallizer coupled with air gap membrane distillation (AGMD) powered by geothermal energy. A review of benefits of geothermal energy and potential applications is reported by Barbier [19]. ...
Membrane distillation (MD) is a newly emerging technology that receives growing attention in the water desalination and purification industries. A mathematical model for MD unit is validated using experimental data. The mass and energy balances were simultaneously calibrated against the collected distillate production rate and measured temperature of the reject permeate stream. The validated model is utilized to evaluate the performance of the process using energy and exergy analysis. This analysis tool will help in process design and operating condition selection that saves energy and improve performance. It is revealed that the exiting warm permeate is responsible for great amount of exergy losses if disposed to the environment. Repeated recycling the outlet permeate to successive MD units arranged in parallel improves the thermal energy effectiveness and increases the production rate. In fact, recovery ratio is increased from 6 to 25% and the exergy lost from the system with exiting permeate is reduced from 1.2 kW to almost null.
... Several studies have been conducted to investigate the performance of geothermal sources coupled with desalination units. Examples of these studies are those of Bourouni et al. [29], Mohamed and El Minshawy [30] and Mahmoudi et al. [31] (HDH process), Koroneos and Roumbas [32] (MED process), Loulatidou and Arafat [33] (MED and RO), Bouchekima [34] (solar stills), Bouguecha and Dhabi [35] (MD process). Sarbatly and Chiam [36] evaluated the energy utilization of VMD modules corresponding to three types of lab-fabricated membranes and one commercial membrane. ...
Geothermal energy has been widely used in power generation and heating. However, its utilization in water desalination is not common due to several barriers and limitations including the saline water quality to be treated and the high cost of such a combined process. Some brackish desalination plants using reverse osmosis (RO) membranes are constructed and under operation. In some of these plants, the raw water is first cooled by damping its heat into the atmosphere using cooling towers. The cooled brackish water is then pumped to the RO membranes. This work discusses several configurations of using geothermal energy to drive desalination of brackish waters. It focuses on the modeling and simulation of a direct contact membrane distillation (DCMD) unit powered by geothermal energy sources. The performance of the whole system composed of the geothermal energy source and the desalination unit is modeled using balance equations of mass, energy and species. Hybrid desalination linking membrane distillation (MD) and RO units is also investigated. The results illustrate the benefits of combining the MD-RO and geothermal energy source in terms of enhancement of the plant recovery ratio. They show in particular that the overall recovery ratio for low salinity feed solutions (lower than 2,000 ppm) is high. The simulations show that it can be around 79% and 67% when the feed salinity equals 800 and 2,000 ppm, respectively.
... Recently, the full integration of MED-AD systems has been suggested as a means of reducing the energy consumption and overall cost of thermal desalination [47,48]. MD is another thermal desalination system that requires relativity low feedwater temperatures for successful operation [34,[49][50][51][52][53]. The MD process could also be used in the downstream thermal desalination processes as a substitute for AD or along with AD. ...
A new process combination is proposed to link geothermal electricity generation with desalination. The concept involves maximizing the utilization of harvested latent heat by passing the turbine exhaust steam into a multiple effect distillation system and then into an adsorption desalination system. Processes are fully integrated to produce electricity, desalted water for consumer consumption, and make-up water for the geothermal extraction system. Further improvements in operational efficiency are achieved by adding a seawater reverse osmosis system to the site to utilize some of the generated electricity and using on-site aquifer storage and recovery to maximize water production with tailoring of seasonal capacity requirements and to meet facility maintenance requirements. The concept proposed conserves geothermally harvested latent heat and maximizes the economics of geothermal energy development. Development of a fully renewable energy electric generation-desalination-aquifer storage campus is introduced within the framework of geothermal energy development.
... A fluidized bed crystallizer and an air-gap membrane distillation (AGMD) unit were investigated for the suitability of geothermal energy sources by Bouguecha and Dhabi [51]. The membrane surface area in the AGMD was 64 7 0.04 cm 2 per cell in a three-cell AGMD unit. ...
Direct use and power generation based on geothermal sources are growing at a steadfast pace around the world. Although available abundantly in many parts of the world, geothermal energy sources have been under-utilized in desalination applications. Geothermal sources have the potential to serve as excellent heat sources for thermal desalination processes. Since thermal desalination processes require large quantities of heat sources, geothermal based energy source represents a feasible, sustainable, and an environmentally friendly option. The advantage with geothermal source is that it can act as a heat source and a storage medium for process energy utilization. If these water sources have high dissolved solids, then they can serve as feed water for the desalination process. Since external energy consumption is minimized except for the mechanical energy requirements, geothermal enabled desalination processes could have less environmental impacts when compared to other nonrenewable energy driven desalination processes. Cogeneration schemes for simultaneous water and power production are also possible with geothermal sources as well as poly generation with multiple process benefits involving cooling and heating applications. This paper provides the present state-of-the-art of geothermal desalination with discussion on the benefits of geothermal desalination over other renewable and nonrenewable energy driven desalination configurations. Present status of the worldwide geothermal desalination and the potential for future developments in this technological area were discussed in detail with case studies for Australia, Caribbean Islands, Central America (Coasta Rica, El Salvador, Guatemala, Honduras, Nicaragua, and Panama), India, Israel, the Kingdom of Saudi Arabia, UAE, USA, and Sub-Saharan Africa.
... Therefore, the potential applications of MD is not only for the production of high-purity water, but also the concentration and crystallization of ionic, colloid or other non-volatile aqueous solutions and removal of trace volatile organic compounds (VOCs) from wastewater (Drioli et al., 1987;Lawson and Lloyd, 1996;Cabassud and Wirth, 2003;Jiao et al., 2004;Khayet et al., 2005;Cath et al., 2005;Gryta, 2002Gryta, , 2006Gryta, , 2007a. MD may offer various advantages in comparison to the traditional distillation and pressure-driven membrane processes if low-grade or waste heat, such as industrial heat streams, geothermic water or even solar energy are provided (Khayet et al., 2003;Bouguecha and Dhahbi, 2003;Ding et al., 2005). ...
Green Membrane Technology Towards Environmental Sustainability covers experimental and theoretical aspects of greener membranes and processes. The book fills the gap in current literature and offers a platform that introduces and discusses new routes in fabricating green membranes and processes for developing green membranes. Although membranes and membrane processes have decades of history, rapid development in membranes manufacturing and emerging membrane driven markets is requiring new and more sustainable engagement of manufacturers, membrane operators and scientists.
This book is written for chemical and polymer engineers, materials scientists, professors, graduate students, as well as general readers at universities, research institutions and R R&D departments in industries who are engaged in sustainable engineering and practical strategies in circular economy.
Membrane distillation (MD) is a sustainable approach for the treatment of challenging saline water by effective removal of non-volatile compounds at high water recovery, offering near-to-zero liquid discharge to environment. Progressive efforts have been made in recent literature to mitigate membrane fouling and enhance the wetting resistance of MD for long-term stable operation; however, extensive energy consumption is the key constraint that hinders MD to become an economically sustainable solution for industrialization. This review represents the evaluation of energy consumption in MD in comparison with other existing advanced water treatment technologies (e.g., reverse osmosis). An up-to-date review of low-energy MD utilization to minimize energy consumption is provided in this work. High energy consumption in MD can be compensated by the effective utilization of renewable energy sources such as solar energy, geothermal energy, or waste heat. However, due to the sporadically unequal distribution and unstable availability of these low-grade sources, the dependence on the abundance of these energy sources may limit the flexibility in commercial MD applications. A recent approach to reduce specific thermal energy through direct heating of the membrane or spacer is also discussed in this review. The development of the membrane materials/configurations was highlighted for mitigating the effects of temperature polarization and improving energy efficiency by localized heating at/near the membrane surface by using photothermal, electrothermal, or induction materials.
In membrane distillation (MD), the membrane as a separating agent can be used for separating a mixture with close boiling point or forming azeotrope, but this separating agent doesn’t need to be recycled. The separation principle of MD is based on the selectivity of a membrane material to components with different structures and properties. For example, for a hydrophobic membrane, volatile organic compounds are more preferential than water to pass through the membrane. As a special distillation process, an outstanding advantage of MD is energy saving, but more work is needed before it is extensively applied in the industry.
The last decade has seen a worldwide increase in the use of alternative energy sources, especially renewable energy (RE), including its application in desalination. In the past many experimental and pilot investigations were presented which allowed the costs and effectiveness of such integrated solutions to be estimated. The present review describes experience related to the use of solar thermal technologies (solar collector and concentrated solar power technologies), solar electricity (photovoltaic and concentrator photovoltaics), wind, hydroelectric (hydropower, tidal, wave and ocean thermal energy), biomass and geothermal energy (power and thermal) as well as hybrid systems. The costs relating to energy and desalinated water production are investigated in the case of various technological processes used in desalination. The main directions for development of the RE systems investigated are discussed and their advantages and disadvantages are assessed. Such a comprehensive review showed that the expansion of the effective use of RE sources is still hampered by several techno-economic aspects. The paper focuses on the main concerns of the need to optimise energy processes, especially by creating more energy-efficient and economically effective solutions, energy storage, energy recovery and the expansion of off-grid systems. As a result of the analysis it was concluded that, despite some disadvantages, the combining of RE with desalination processes requires further intensive research and demonstration units for longer term performance. Regulations to develop less energy-intensive desalination technologies are also still needed.
This chapter contains sections titled: Introduction Renewable Energy Powered Desalination Geothermal Energy Utilization Around the World The Rationale – Why Geothermal Desalination? Global Geothermal Desalination Potential Geothermal Desalination – State of the Art Desalination Process Selection Challenges and Considerations for Geothermal Desalination Implementation Techno‐Economics of Geothermal Desalination Summary
Desalination technologies can utilize various forms of energy to produce freshwater. The first law of thermodynamics (energy) analysis is used commonly to determine the process efficiency, which is not a true measure of the process performance because it does not account for all losses of energy. The second law of thermodynamics (exergy) is an efficient tool to evaluate the performance of desalination systems. This method accounts for all forms of available energy in the process streams and energy sources with a reference environment to identify the major losses of exergy destruction to aid in resource-efficient desalination system design. Due to changing climate concerns and dwindling conventional energy sources, renewable energy has been identified as a sustainable alternative to supply the energy demands for desalination processes. Desalination processes can be powered by solar, wind, geothermal, and tidal energy sources depending on the process type and configuration. This paper elaborates on use of exergy tools to evaluate renewable energy powered desalination processes to evaluate their thermodynamic efficiency. Illustrations are provided to identify the major components and process streams that contribute to major exergy destruction and to suggest suitable operating conditions that minimize exergy losses. Well-established MSF, MED, RO, Solar distillation and membrane distillation technologies were discussed with case studies to illustrate their exergy performances. Single (water only) and dual (water and power) purpose desalination plants were discussed. Cogeneration, trigeneration (water, power, and heating/cooling) and polygeneration schemes and their exergy performance were also included.
Different chemical pretreatment strategies followed by direct contact membrane distillation (DCMD) process were adopted for the processing of reverse osmosis (RO) brine. CPT with Na2CO3 + NaOH allowed scale reduction, removing both permanent calcium hardness and temporary calcium hardness whereas the chemical pretreatment with BaCl2 permitted to remove sulfate ions from RO brine. This last chemical pretreatment was found to be the most efficient pretreatment improving the DCMD performance because of the corresponding highest permeate flux, lowest permeate flux decline and best permeate quality. However, it is relatively an expensive pretreatment not recommended for consumption because of the toxic residual barium. The brine was concentrated up to 37 wt% of salts in water, which is above the limiting salt (NaCl) saturation concentration. Therefore, the volume of discharged RO brine can be reduced considerably facilitating its efficient management.
Theoretical and experimental validation of a water gap membrane distillation (WGMD) process has been proposed and successfully tested for seawater desalination. It has been observed that, employing water in the air gap between the membrane and condensation plate of an air gap membrane distillation (AGMD) module, there is a significant enhancement of the water vapor flux, reaching 800 %. A detailed investigation on the influence of thickness of the water gap has been carried in this study. Water vapor flux enhancement in the WGMD process has been described with the help of a theoretical explanation of heat and mass transfer mechanisms through the membrane and water gap. Heat and mass transfer resistance in the air gap during an AGMD process is the major limiting factor for the lower water vapor flux. It was observed that employing water in the air gap of an AGMD module eliminates the heat and mass transfer resistance in the air gap and results in increased water vapor flux. Temperature polarization is another phenomenon which adversely affects all MD processes and causes a significant decrease in the water vapor flux. During the WGMD process, occurrence of natural convection in the water gap helps to decrease the temperature polarization and provide a synergistic effect along with the sensible heat transfer to enhance the water vapor flux. A theoretical explanation of the natural convection during the WGMD process will be described in this paper.
This paper examines the feasibility of a solar powered membrane distillation plant for the supply of domestic drinking water in the arid/rural regions of Australia. The plant differs from conventional solar powered devices in its capacity to recover large proportions of the latent heat of vapourisation using conventional heat-exchange devices. The plant has been designed and constructed using data obtained from a computer simulation of the process. Preliminary tests have shown the plant capable of achieving the required production capacity. An economic sensitivity analysis has been used to select the optimum heat recovery.
Aqueous solutions of alcohol (ethanol, methanol or isopropanol) have been experimentally investigated in air gap membrane distillation (AGMD), for a wide range of operating conditions. The effects of the relevant process parameters on the permeate flux have been studied. On the basis of a temperature polarisation model — which takes into account the mass and heat transfers across the hydrophobic membrane — the equivalent film heat transfer coefficient and the overall membrane mass transfer coefficient can be obtained from the experimental data. Also the alcohol and water membrane transfer coefficients have been obtained assuming the validity of Graham’s diffusion law for multicomponent mixtures. From these coefficients the temperature and composition in the liquid–vapour interfaces are evaluated, taking into account the temperature polarisation and concentration polarisation models. Finally, the effect of the Reynolds number on the permeate flux has been discussed using the temperature polarisation model and the heat transfer correlation given by Sieder and Tate.
The pellet reactor is an interesting example of a clean technology. Contrary to conventional water treatment processes, no waste sludge is produced which has to be dumped. Instead, pure, solid grains are produced that can be reused in industry. For the water softening process, a state-of-the-art review is presented of the fundamental theory, including model calculations. Moreover, attention is paid to nonideal behavior, such as short-circuiting, erosion of pellets and homogeneous nucleation. Finally, the practical experience gained with softening in the pellet reactor at Dutch waterworks is reviewed.
A combined system made of a one-stage multieffect distiller, working at atmospheric pressure, and a membrane distillation module were studied. The relatively hot brine rejected in the multieffect distiller is used as feed in the membrane module. In this way, the production of distilled water is increased about 7.5% and the GOR of the whole system is improved by about 10%.
This paper provides a state-of-the-art review of the separation process known as membrane distillation, MD. An introduction to the terminology and fundamental concepts associated with MD as well as a historical review of the developments in MD are presented. Membrane properties, transport phenomena, and module design are discussed in detail. A critical evaluation of the MD literature is incorporated throughout this review.
L'expérience tunisienne en matière de dessalement est amplement enrichie avec la mise en service de la Station de Dessalement de Gabès en juin 1995. L'exploitation de cette station, de capacité 22,500 m3/j extensible à 30,000m3/j, durant plusque cinq ans a contribué considérablement dans la maîtrise de la technique membrannaire d'osmose inverse, l'amélioration de la phase prétraitement, la réduction de la consommation en énergie et par conséquent le rehaussement des performances de cette unité. Trois aspects phares illustrent sans équivoque les performances de cette station qui traitent les eaux saumâtres de la nappe Continentale Intercalaire de salinité 3.2 g/l. Le premier aspect se traduit par le fait qu'aucun module de 1188 en polyamide spiralé que comporte la station n'a été remplacé après cinq ans de production quoique le taux annuel habituel de replacement dans les stations de dessalement à travers le monde soit de 10%. Le second aspect consiste dans la stabilité de la salinité d'eau osmosée qui demeure au-dessous de 200 ppm garantie par le constructeur pour une période maximale de trois ans ce qui a facilité la constance de la salinité de mélange automatique des eaux osmosées avec l'eau saumâtre distribuées aux 200,000 citoyens de la région de Grand Gabès, Ouedhref Metouia et El Hamma. Le Troisième volet intéresse la réduction du coût de mètre cube d'eau osmosé produit qui a été ramené de 777 millimes/m3 en 1995 à 500 en l'an 2000 y compris l'amortissement soit une réduction de 40%. Ces performances enregistrées malgré le problème de biofouling rencontré la première année s'explique essentiellement par la bonne exploitation de station, l'efficacit'e du prétraitement, un entretien sans faille, la qualification du personnel et un encardrement judicieux. De surcroît, il était possible d'augmenter la capacité de la station durant la saison estivale à 25,500m3/j sans ajouter aucun module et retarder parconséquent des investissments lourds en différant la réalisation de la quatrième ligne.
Different possible desalination techniques are proposed in association with wind, tidal, and solar energy sources. Combined wind or tidal power-desalination systems include vapor compression, reverse osmosis, electrodialysis and freezing-melting techniques. However, solar systems incorporate, in addition, multi-effect flash and multi-effect evaporation. In every case the energy source units are matched to the desalination equipment to set possible practical operating limits. Analysis of each system is undertaken to set limits of useful operation. Effect of the main operating conditions for each system on fresh water productivity and required energy is obtained. Coupled charts for the renewable energy source and the desalination technique assigned to it are presented. The charts cover wide operational ranges and are beneficial in the initial design stages of such systems. The application ranges used show the extent of possible useful operation under various operating conditions.
An experimental study has been made of the gasification of poplar bark particles exposed to a helium/water vapor atmosphere in a fixed-bed reactor at 873–973 K. with and without silica catalyst. The effect of temperature on gas yields, calorific value and carbon conversion was evaluated for the pyrolytic conversion and steam-char gasification stages. The kinetics of the production of various gases in catalytic steam-char reaction has been studied.
On a fait une étude expérimental de la gazéification de particules d'écorce de peuplier exposées à une atmosphère d'hélium et de vapeur d'eau, dans un réacteur à lit fixe à une température variant entre 873 K et 973 K en présence et en l'absence d'un catalyseur à base de silice. On a évalué l'effet de la température sur les rendements en gaz, le pouvoir calorifique et la conversion du carbone, pour les étapes de conversion pyrolytique et de gazéification par réaction de la vapeur d'eau sur le produit carbonisé. On a étudié la cinétique de la production de divers gaz lors de la réaction catalytique de la vapeur d'eau sur le charbon de bois.
Today there are many reverse osmosis (RO) plants in operation all over the world for desalination processes. The operating costs for both seawater and brackish water desalination are already competitive with those of thermal operations. These costs are mainly related to the costs of the pretreatment steps, which for seawater desalination might reach 60% of overall costs. By introducing integrated membrane operations, a possible reduction might be possible with an increase of water quality. For example, cross-flow microfiltration (MF), ultrafiltration (UF) and eventually nanofiltration (NF) units might be introduced in the pretreatment line for purifying and clarifying the feed streams and for reducing bivalent ions concentration. If the removal of dissolved gases (CO2, O2, etc.) is suggested, the possibility of also introducing membrane contactors before the RO treatment might be considered. Moreover, the recovery factor of the RO process could be enhanced by introducing membrane distillation (MD) units to treat the RO brine. In the present work, integrated membrane operations such as the ones described above are analyzed for a seawater desalination system. Preliminary experimental results will be discussed confirming the possibility of reaching a seawater recovery factor of 87%.
Jet-spouted beds characterised by high velocity gas jets (above 1.7 Umsl), and shallow bed depths H0 of around 2 D1 were investigated on laboratory scale beds and industrial scale beds and the results obtained thereof are correlated and presented in this work. Compared with the classical spouted beds, important differences in bed structure, solid movements and basic hydrodynamic characteristics were observed. The minimum spouting velocity, bed voidage and pressure drop during stabilized spouting are described in terms of dimensionless equations. Bed expansion was used as the basis for the classification of different jet-spouting regimes (incoherent spouting, fast spouting, pneumatic conveying) and changes in the slope of the bed expansion curve are correlated with regime changes. This classification could be useful in the optimization of industrial scale jet-spouted beds. A typically applicable regime of fast spouting was identified.
An integrated reverse osmosis (RO) + membrane distillation (MD) system where MD operates on the RO brine is considered for desalination processes. In particular, an energy and exergy analysis of the RO unit alone and coupled to the MD unit is presented in order to determine the energy requirements related to the integrated system with respect to the RO one. This energetic analysis coupled to the analysis of the overall performance of the two different systems led to an evaluation of the potentialities of the integrated membrane processes in desalination operations. The analysis has been tentatively extended to a complete membrane integrated system where nanofiltration (NF) has been also considered in the RO feed pretreatment.
The growth kinetics of calcite crystals are studied in a batch-fluidized-bed crystallizer, which is maintained at a constant pH. The growth experiments are conducted in the metastable region explored as part of this research. The crystal growth rates are evaluated from the consumption rates of calcium ions, using the cured natural calcite or silica sand as seeding materials. Several operation variables are investigated, including supersaturation, pH, ionic strength, superficial velocity, and particle size and type of seed. The significant factors that affect the crystal growth rate are identified. Then the crystal growth data of constant pH and ionic strength are analyzed by the two-step growth model. The mass-transfer coefficients are obtained and compared at various crystal sizes and superficial velocities. Finally, a growth-rate equation of calcite crystal, which is based on the two-step growth model, is proposed for design purposes.
Aqueous solutions can be concentrated and pure water prepared via a thermal membrane separation process. Membranes used for this purpose must be microporous and hydrophobic. A temperature difference causes a vapour transfer from the warmer to the colder side. Modules for this process are, for practical reasons, counterflow devices with capillary membranes that have good flow conditions outside a capillary bundle, too. This requires special capillary arrangements and module constructions.
Potential renewable energy sources, which can be harnessed toward brackish and seawater desalination in Tunisia, have been evaluated. These sources of energy, mainly: solar, wind and geothermal, have been identified throughout the country and their suitability for coupling with different desalting technologies have been investigated. Renewable energies are expected to have a flourishing future and an important role in the domain of brackish and seawater desalination. Of special interest, are small desalination plants which can be operated with small quantities of energy. Small-scale renewable energy driven desalination plants might be the most economical solution for providing portable water to remote and isolated communities where the electric grid and the proper infrastructure are lacking. By exploiting renewable energies for fresh water production, three main problems can be addressed: fresh water scarcity, fossil energy depletion and environmental degradation due to gas emissions and hydrocarbon pollution.
A new segmented flow tubular reactor for the continuous production of powders was used to synthesize calcium carbonate by precipitation. This new reactor uses a nonmiscible phase (air in most cases) to create individual microvolumes of the reacting mixture or suspension ensuring that a plug-flow regime is maintained. In a microvolume, poor micromixing can be avoided and the homogeneity in reaction conditions is increased better than in larger volumes, leading to a better control of powder characteristics. Calcium carbonate with controlled characteristics could be precipitated continuously using this new segmented flow tubular reactor. Pure calcite could be obtained in the tubular reactor by segmenting a Ca2+ solution with a reactive CO2/NH3 gas mixture. This synthesis process is very promising for industrial production since the scale-up should easily be achieved by multiplying the number of tubes working in parallel.
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