Yes / The reverse osmosis (RO) process is one of the most popular membrane technologies for the generation of freshwater from seawater and brackish water resources. An industrial scale RO desalination consumes a considerable amount of energy due to the exergy destruction in several units of the process. To mitigate these limitations, several colleagues focused on delivering feasible options to resolve these issues. Most importantly, the intention was to specify the most units responsible for dissipating energy. However, in the literature, no research has been done on the analysis of exergy losses and thermodynamic limitations of the RO system of the Arab Potash Company (APC). Specifically, the RO system of the APC is designed as a medium-sized, multistage, multi pass spiral wound brackish water RO desalination plant with a capacity of 1200 m3/day. Therefore, this paper intends to fill this gap and critically investigate the distribution of exergy destruction by incorporating both physical and chemical exergies of several units and compartments of the RO system. To carry out this study, a sub-model of exergy analysis was collected from the open literature and embedded into the original RO model developed by the authors of this study. The simulation results explored the most sections that cause the highest energy destruction. Specifically, it is confirmed that the major exergy destruction happens in the product stream with 95.8% of the total exergy input. However, the lowest exergy destruction happens in the mixing location of permeate of the first pass of RO desalination system with 62.28% of the total exergy input.

Yes / The desalination of saltwater is a viable option to produce freshwater. All the desalination processes are energy-intensive and can be carried out on a large scale. Therefore, producing freshwater using renewable energy sources is the most desirable option considering the current energy crisis and the effect that fossil-fuel-based energy has on our carbon footprint. In this respect, the tray-type still, one of several solar power desalination still varieties, is popular owing to its straightforward design, economic materials of construction, and minimal maintenance requirements, especially in isolated island regions with restricted energy and natural water supplies. The traditional tray-type solar power has a few drawbacks, such as the inability to recover latent heat from condensation, reduced thermal convection, a large heat capacity, and comparatively minimal driving power through evaporation. Therefore, the improvement of heat and mass transfer capabilities in tray-type stills has been the subject of many studies. However, there is a lack of a comprehensive review in the open literature that covers the design and operational details of multistage solar stills. The purpose of this paper is to present a thorough overview of the past research on multistage solar stills, in terms of configurations, capabilities, and cutting-edge options. In comparison to a unit without a salt-blocking formation, the review indicates that a multistage distillation unit may run continuously at high radiation and generate pure water that is around 1.7 times higher than a unit without a salt-blocking formation. The most effective deign is found to be “V”-shaped solar still trays that attach to four-stage stills, since they are less expensive and more economical than the “floor” (Λ-shape) design, which requires two collectors. Additionally, it can be stated that the unit thermal efficiency, solar percentage, and collected solar energy (over the course of a year) increase by 23%, 18%, and 24%, respectively, when the solar collectors are increased by 26% (at the constant inflow velocity of the water).

Yes / Clean water demand has significantly increased due to the rise in the global population. However, most water on the Earth has high saline content that cannot be consumed directly; only about one over forty of the total water source is freshwater. Desalinated water is one of the potential solutions to meet the growing demand for freshwater, which is highly energy intensive. This paper analyses the energy, economic and environmental performance of a 5 m3/day PV (photovoltaic) powered reverse osmosis (RO) desalination system. Three scenarios of PV-RO with and without battery storage and diesel generator hybrid systems have been analyzed and investigated for the annual estimate load, net present value, and payback period of the water and electricity production costs. Also, the CO2 avoidance over the lifetime operation of all scearios is evaluated. This study shows that the PV-RO system without battery with 6.3 kW PV panels installed and with a 2-days water storage tank system is the most profitable economically f. For this scenario, the Levelized Cost of Electricity (LCOE), Levelized Cost of Water (LCOW), and Payback Period (PBP) are found to be $0.154/kWh, $0.627/m3, and five years, respectively. In addition, for this scenario, the CO2 emissions avoidance was the maximum (111,690 kg.CO2eq per year) compared to other scenarios.

Yes / Desalination has become one of the obvious solutions for the global water crisis due to affording high-quality water from seawater and brackish water resources. As a result, there are continuing efforts being made to improve desalination technologies, especially the one producing high-quantity freshwater, i.e., thermal desalination. This improvement must be accomplished via enhancement of process design through optimization which is implicitly dependent on providing a generic process model. Due to the scarcity of a comprehensive review paper for modeling multi-effect distillation (MED) process, this topic is becoming more important. Therefore, this paper intends to capture the evolution of modeling the forward feed MED (most common type) and shed a light on its branches of steady-state and dynamic modeling. The maturity of the models developed for MED will be thoroughly reviewed to clarify the general efforts made highlighting the advantages and disadvantages. Depending on the outputs of this review, the requirements of process development and emerging challengeable matters of modeling will be specified. This, in turn, would afford a possible improvement strategy to gain a reliable and sustainable thermal desalination process.

Yes / Fresh water is crucial for life, supporting human civilizations and ecosystems, and its production is one of the global issues. To cope with this issue, we evaluated the performance and cost of a solar-powered direct contact membrane distillation (DCMD) unit for fresh water production in Karachi, Pakistan. The solar water heating system (SWHS) was evaluated with the help of a system advisor model (SAM) tool. The evaluation of the DCMD unit was performed by solving the DCMD mathematical model through a numerical iterative method in MATLAB software®. For the SWHS, the simulation results showed that the highest average temperature of 55.05 ◦C and lowest average temperature of 44.26 ◦C were achieved in May and December, respectively. The capacity factor and solar fraction of the SWHS were found to be 27.9% and 87%, respectively. An exponential increase from 11.4 kg/m2 ·h to 23.23 kg/m2 ·h in permeate flux was observed when increasing the hot water temperatures from 44 ◦C to 56 ◦C. In the proposed system, a maximum of 279.82 L/day fresh water was produced in May and a minimum of 146.83 L/day in January. On average, the solar-powered DCMD system produced 217.66 L/day with a levelized water cost of 23.01 USD/m3 / This research was funded by the Researcher’s Supporting Project Number (RSP-2021/269), King Saud University, Riyadh, Saudi Arabia.

In several areas around the world, clean water is a precious asset that at anytime, and mainly due to circumstances of weather and climate, can become scarce. Mainly in the dry and remote places, people suffer with lack of water. A solution for this suffering can be a water desalination system, which makes water potable and usable for industry. That solution inherently, brings the problem of power requirement, which is sometimes arduous to accomplish in such remote areas of difficult access and long distances to overcome to build the infrastructure required to operate an electric power plant. Texas and the USA also face this scenario for many regions, for which the government has been creating some programs and driving forward incentives, looking for solutions to support water desalination. Water desalination has future applications for municipalities water-consuming or for arid and remote regions, as well as for industries that rely on heavy water usage, such as natural gas drilling operations, for which millions of gallons are trucked overland to the site and also hauled away afterwards, when the waste water produced must be treated. This thesis created the concept of autonomy for water desalination plants replacing the actual power supply from fossil fuel to a renewable source from wind or sun, giving capacity to them to produce its own electricity to operate as an autonomous unit, as demonstrated in the business case done for the Brownsville water desalination facility.

The application of membranes in liquid and gas separation is attractive because of their energy efficiency. Synthesis of membranes with well-defined nanostructure is necessary to achieve highly permeability and selectivity for separation processes. Recently, carbon nanomaterials such as graphene oxide nanoplatelets (GONPs) and carbon nanodots (CNDs) have emerged as an interesting class of nanomaterials due to their unique properties and tailorable functionalities. Incorporation of these nanomaterials in the membranes has been shown to improve membrane selectivity, mechanical robustness, and chemical stability. This dissertation elaborates on developing CNDs or GONPs embedded thin film composite (TFC) membranes using layer-by-layer (LbL) synthesis technique. Regarding the water desalination applications, GONPs were used to enhance the TFC membranes’ selectivity, chlorine resistant properties, and surface hydrophilicity. Incorporation of GONPs in the polyamide layer via LbL method resulted in an increase of surface hydrophilicity and salt rejection properties. Upon exposure to chlorine, GONPs embedded membranes retained salt rejection performance better than the pristine membranes (without GONPs). The LbL assembly was used to synthesize CNDs based TFC membranes for organic solvent nanofiltration (OSN) applications. Using the LbL framework, amineunctionalized CNDs were covalently crosslinked with trimesoyl chloride monomer to obtain nanoscale membranes. The synthesized membranes manifested high selectivity (up to 90%) when tested for dye molecules such as brilliant blue and disperse red in methanol. As the CNDs synthesized here are fluorescent under UV light, the resultant film is also fluorescent. This property can be harnessed for diagnostic purposes, such as tracking mechanical failure and fouling of the membranes. Based on the results, it can be concluded that the incorporation of carbon nanomaterials in the polymeric membranes has enhanced the hydrophilicity, mechanical stability, and chlorine resistant properties of the membranes. Overall, the LbL platform can be considered as a modular method in embedding nanoparticles in TFC membranes.

Partial nitritation combined with the anaerobic ammonium oxidation (Anammox) process offers a way of replacing the conventional nitrogen removal process of nitrification-denitrification, lowering the need for oxygen and chemical input, as well as reducing the production of sludge. However, as a by-product of the biochemical reaction driven by anammox bacteria, it produces nitrate-nitrogen (NO3- - N) (16-26% nitrogen removed), which is problematic. Microbial desalination cells (MDCs) are a promising technology capable of converting biodegradable organics into electricity (by electroactive bacteria), providing for simultaneous desalination, and wastewater treatment. Despite being a promising technology, MDCs have limitations. The first-proof of-concept of MDC was demonstrated using acetate as the organic source, expensive platinum as a catalyst, and ferricyanide as an electron acceptor in the cathode that makes MDC costly, environmentally unfriendly, and unsustainable. This research investigated the integration of the anammox and nitration processes in MDCs as a long-term biocatalyst/biocathode for sustainable and energy-efficient nitrogen removal and electricity generation. A series of experiments were designed and performed to evaluate the performance of the anammox process as a biocatalyst in MDCs. The results concluded that the anammox process can be used as a biocatalyst to accept electrons in MDCs producing 444 mW/m3 of power density and 84% of ammonium nitrogen removal. Furthermore, the concept of using a one-stage nitritation anammox process as a biocathode in MDC was evaluated and produced a maximum power output of 1007 mW/m3. Two configurations of anammox MDCs (anaerobic-anammox cathode MDC (AnAmmoxMDC) and nitritation-anammox cathode MDC (NiAmoxMDC) were compared with an air cathode MDC (CMDC), operated in fed-batch mode. The NiAmoxMDC showed better performance in terms of power production and nitrogen removal. The co-existence of aerobic ammonium oxidizing bacteria (AOB) and anammox bacteria in the same biocathode of single-stage NiAmoxMDC concluded the resource-efficient wastewater treatment. Furthermore, two-stage nitritation anammox as a biocathode in MDC was evaluated and proved to be energy-efficient bioelectrochemical wastewater treatment by producing 1500 mW/m3 (300 mW/m2) of maximum power output. This research provides the first proof of concept that nitritation-anammox biocathode can provide a sustainable and energy-efficient nitrogen removal along with desalination and bioelectricity generation.

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Yes / In this work, an artificial neural network (ANN) model based on the experimental data was developed to study the performance of vacuum membrane distillation (VMD) desalination process under different operating parameters such as the feed inlet temperature, the vacuum pressure, the feed flow rate and the feed salt concentration. The proposed model was found to be capable of predicting accurately the unseen data of the VMD desalination process. The correlation coefficient of the overall agreement between the ANN predictions and experimental data was found to be more than 0.994. The calculation value of the coefficient of variation (CV) was 0.02622, and there was coincident overlap between the target and the output data from the 3D generalization diagrams. The optimal operating conditions of the VMD process can be obtained from the performance analysis of the ANN model with a maximum permeate flux and an acceptable CV value based on the experiment.