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In this research study, a direct contact membrane distillation (DCMD) system was used in the concentration of raw brine from a full-scale reverse osmosis desalination plant for further zero-liquid discharge (ZLD) applications. Several operating conditions such as feed inlet temperature (Tf), feed (Qf) and permeate (Qp) flow rate, and feed concentration (Cf) were tested to obtain the optimum permeate flux across the membrane, salt rejection and specific thermal energy consumption (STEC). The highest flux of 16.7 LMH, salt rejection of 99.5% and STEC of 152 kWh/m3 were achieved at Tf, Qf, Qp, and Cf of 85 °C, 75 L/h, 48 L/h and 57,500 ppm, respectively. Furthermore, this study was carried out for a long term operation of 77 h in which the membrane was found to be prone to significant fouling thereby resulting in a flux decline across the membrane of 69%. To mitigate fouling, novel membranes were prepared through the surface coating of commercial membranes with graphene nanoplatelets (GNPs) at 0.08, 0.16 and 0.2 wt%. Over a 10 h operation, membranes coated with 0.08 and 0.16 wt% GNP reduced membrane fouling by 59 and 78%, respectively.

Recently, thermosiphon has been considered as an economically competitive approach for the withdrawal of thermal energy from molten salt. This feature of thermosiphon is particularly attractive for concentrated solar power (CSP) technology because molten salt can be used both as the direct receiver and thermal energy storage material, and pumping requirements can be minimized. However, the thermosiphon loop must be properly designed; otherwise the heated molten salt can flow in the reverse direction or solidify before heat exchange is fully carried out. In this paper, the dependence of important molten salt flow characteristics such as temperature, velocity and friction factor on the thermosiphon loop dimensions is theoretically investigated. The model is carried out for the withdrawal of 1 MW of thermal energy from the molten salt. The economic assessment of the conversion of this energy to electricity for reverse osmosis desalination is also carried out. It is observed that by using the minimum possible value of leg length and maximum possible values of diameter and pressure head, the lowest decline of temperature and highest velocity of flow can be achieved along the loop. Fresh water production is more valuable than electricity and steam production by 460% and 480%, respectively.

Reject brine is the product from desalination processes containing high salinity, high temperature, and at many times, dissolved chemicals. With the growing demand of water, increasing amounts of brine are being produced from the desalination plants leading to significant adverse impacts on the environment. It is necessary therefore to effectively manage desalination reject brine in order to ensure more efficient disposal and reuse. This review gives a general idea on the recent and currently devised brine management processes, which have been employed to reduce the environmental issues related to concentrate dumping. Those management approaches consist of minimization techniques that can be divided into membrane-based, thermal-based and emerging technologies. Moreover, this critical review gives an overview of the various applications of brine and some sustainability aspects of the reject brine disposal and reuse. The most obvious sustainable improvements in reject brine management are based on minimization techniques or reuse that can be achieved through the recovery of valuable materials such as salts, metals, and chemicals. Many new research works in this field have been introduced and scientists have continued to devise reject brine reuse strategies and minimization technologies leading to very low quantities of residual brine.

Electrokinetic cells with three different electrode arrangements were supplied with raw seawater collected from the Gulf. The electrode arrangements included anode-cathode (A-C), anode-cathode-cathode-anode (A-C-C-A), and cylindrical (three cathodes surrounded by an anode) configurations. The electrokinetic cells were tested at different current densities ranging from 0.05 to 0.2 mA/cm2 for 6 h. The results showed that inorganic ions and bacteria removal increased with increasing current density. For example, at a current density of 0.2 mA/cm2, 78, 76, and 91% of the Mg2 + ions were removed by the A-C, A-C-C-A, and cylindrical configurations, respectively, whereas these cells removed 64, 63, and 51% of the Mg2 + ions, respectively, at a current density of 0.1 mA/cm2. In addition, the A-C, A-C-C-A, and cylindrical cells removed 21, 40, and 44% of the Ca2 + ions, respectively, and 47, 79, and 79% of the SO42 − ions, respectively, at a current density of 0.2 mA/cm2. The removal efficiencies obtained with the A-C, A-C-C-A, and cylindrical cells were 15, 18, and 13%, respectively, for Ca2 + and 47, 26, and 22%, respectively, for SO42 − at a current density of 0.1 mA/cm2. Furthermore, nearly all of the bacteria were removed under the tested operating conditions (total bacteria count (TBC) was zero).

In this paper, the current and most recent applications of direct contact membrane distillation (DCMD) are discussed. Apart from its rapidly increasing use for the desalination of highly saline feed water, the DCMD is gradually becoming a preferred technology for produced water treatment, purification of groundwater, reclamation of industrial process water, removal of micropollutants from drinking water, juice concentration, and production of chemical products. The fundamentals of the DCMD and governing equations (from heat and mass transfer principles) that describe performance parameters are first explained. Current issues in the DCMD operations such as the influence of membrane type, membrane fouling, and operating conditions on the DCMD performance or productivity are also discussed in this paper. Hybrid systems and renewable energy integration with DCMD systems have been presented as viable solutions that would enhance the sustainability of the DCMD operations.

Humidification–dehumidification (HDH) desalination technology with the use of recovered photovoltaic (PV) thermal energy could be viable for the production of small-capacity sustainable water and improvement of PV electric power generation efficiency. This paper investigates the technical feasibility and environmental friendliness of an air-cooled PV system integrated with ambient seawater inflow into a HDH desalination system. The technical analysis of the PV-HDH desalination process was carried out through the modeling of the physical and thermodynamic properties involved in the recovery of PV thermal energy and determination of the effect of this recovery on water produced under the environmental conditions of Abu Dhabi, UAE. The results showed that the heat recovered from the PV resulted in the production of a daily average of 2.28 L of fresh water per m 2 of PV. On the other hand, the environmental impact assessment of this PV-HDH power and desalination technology was also carried out for the first time in order to determine its viability for small-scale sustainable water and energy production. The PV-HDH system resulted in 83.6% decrease in environmental impacts when compared with PV-Reverse Osmosis (PV-RO) system. In conclusion, the integrated PV-HDH desalination technology is promising and expected to play a key role in the field of water desalination.

Given their unique structural and morphological features, nanomaterials have gained considerable attention for their applications in membrane desalination. Recent advances in nanomaterial-incorporated membranes have resulted in membranes with very high water flux and salt rejection, both being sought after in membrane desalination. Nevertheless, the economic feasibility of scaling up such membranes remains questionable. The present paper surveyed the recent published literatures and current studies on nanomaterials and their applications in membrane desalination. The goal of this work was to reveal, through reviewing experimental and computational studies, the potential of nanomaterials in desalination. The paper reviewed three of the most studied nanomaterials in membrane desalination namely; carbon nanotubes, zeolites, and graphene. The investigation included preparation and synthesis of nanomaterial membranes, their properties with respect to desalination, and their applications in membrane desalination. This includes different membrane processes, and opportunities and challenges of those materials in desalination applications. The environmental and economic sustainability of nanomaterials in desalination for future prospects has also been presented.

Recent research reports have underlined reverse osmosis (RO) as the most optimized technology for water desalination related applications. However, implementing this technology to seawater desalination is facing challenges of membrane fouling. This includes membrane biofouling, organic and inorganic fouling which adversely affect the process performance and overall treatment cost. To overcome these issues, pretreatment units ahead of the RO system are necessary to reduce RO membrane fouling and enhance its operational efficiency. This article aimed at reviewing the literature and summarizing relevant methods, mechanisms and novel developments which improve the performance of the RO systems when coupled with either conventional or non-conventional pretreatment units. Several studies suggested that the non-conventional pretreatment units were more efficient than the conventional systems for producing better water quality and minimizing the overall treatment cost. Ultrafiltration appeared to be a cost effective and efficient method of removing suspended solids (SS) and bacteria. The advent of nanostructured membranes nanofiltration has the potential of becoming preferred non-conventional desalination pretreatment over a wide range of salinity, total dissolved solids (TDS), inorganics, viruses, etc.