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The study presents an innovative solar-assisted dual-tank direct contact membrane distillation (DCMD) system designed to enhance the operational stability and efficiency of solar-powered desalination. The proposed system integrates a dual thermal storage tank configuration, allowing for continuous operation by alternating between two tanks that store pre-heated water, thereby mitigating the impact of solar energy fluctuations. The dynamic modeling approach used in this study predicts the system's performance under varying solar conditions, focusing on key parameters such as permeate flux, evaporation efficiency, and specific thermal energy consumption. The simulation results show that the system achieves an average permeate flux of 14.4 L/h m² and a thermal efficiency of 53.3 % at a hot water temperature of 60 °C, with a corresponding average specific thermal energy consumption of 1567 kWh/m³. These findings highlight a substantial improvement in both thermal efficiency and water production compared to conventional single-tank systems.The dual-tank DCMD system is particularly suited for deployment in remote or arid regions where stable and efficient freshwater production is critical. This research provides a comprehensive analysis of a novel solar-assisted desalination technology, contributing to the advancement of sustainable water resources management by providing a reliable and scalable solution that can maintain high operational efficiency even in remote areas with variable solar conditions.

Membrane desalination (MD) is an efficient process for desalinating saltwater, combining the uniqueness of both thermal and separation distillation configurations. In this context, the optimization strategies and sizing methodologies are developed from the balance of the system’s energy demand. Therefore, robust prediction modeling of the thermodynamic behavior and freshwater production is crucial for the optimal design of MD systems. This study presents a new advanced machine-learning model to obtain the permeate flux of a tubular direct contact membrane distillation unit. The model was established by optimizing a long-short-term memory (LSTM) model by an election-based optimization algorithm (EBOA). The model inputs were the temperatures of permeate and the feed flow, and the rate and salinity of the feed flow. The optimized model was compared with other optimized LSTM models by sine–cosine optimization algorithm (SCA), artificial ecosystem optimizer (AEO), and grey wolf optimization algorithm (GWO). All models were trained, tested, and evaluated using different accuracy measures. LSTM-EBOA outperformed other models in predicting the permeate flux based on different accuracy measures. LSTM-EBOA had the highest coefficient of determination of 0.998 and 0.988 and the lowest root mean square error of 1.272 and 4.180 for training and test, respectively. It can be recommended that this paper provide a useful pathway for sizing parameters selection and predicting the performance of MD systems that makes an optimally designed model for predicting the freshwater production rates without costly experiments.

Unlike steam turbines, electricity production in gas turbines is inherently independent of freshwater consumption. However, the thermal efficiency of gas turbines decreases as the temperature of input air increases. As a result, many methods of cooling the inlet air require the use of fresh water. Moreover, when it comes to humid gas turbine technology, the practice of injecting steam or humid air into the turbine to improve its thermal efficiency and output power consumes a substantial amount of freshwater. Therefore, reducing the use of fresh water to enhance the output power and thermal efficiency of gas turbines can be a necessary option, especially in hot and dry regions. Alternatively, considering the significant amounts of waste heat in gas turbines, one solution to reduce fresh water consumption is to connect them to thermal desalination units. However, conventional thermal desalination is only practical for seawater desalination in coastal areas. Therefore, this study explores the possibility of linking a direct contact membrane distillation (DCMD) unit to a Steam-injected gas turbine (STIG), which can use high salinity water sources like reverse osmosis (RO) brine in inland regions. The freshwater generated by the DCMD is used to chill the input air to the compressor and produce steam injected within the turbine. Simulation results show that this connection can raise the net output power by [9 to 17.2] MW and thermal efficiency by [3.3 to 15.6] % for compressor pressure ratios between [5 to 30], when compared to a simple gas turbine.

Biofouling in membrane distillation (MD) has several repercussions, including reduced efficiency of the MD process and limiting membrane life. Additionally, the evaluation of MD biofouling using treated effluents from wastewater treatment plants remains an unexplored area. Thus, biofouling formation and development in a long term MD process (15 days) using treated effluent from a wastewater treatment plant was explored in this study. The results revealed that flux decline occurred in four phases: i) initial decline (0-1 d), ii) gradual decline (1-5 d), iii) progressive decline (5-10 d), and iv) rapid decline (10-15 d). Liquid Chromatography-Organic Carbon Detection (LC-OCD) analysis demonstrated that the treated effluent contained humic-like substances, which deposited on the membrane surface in phase 1. Whereas biopolymers development on the membrane surface in phase 2 and 3 was linked to biofouling. Microbial community analysis revealed that the initial colonisers were predominantly thermophilic bacteria, which were different from the microbial community of the treated effluent. The biofilm-forming bacteria included Schlegelella, Meiothermus, and Vulcaniibacterium. These microorganisms proliferate and release excessive extracellular polymeric substances (EPS), leading to the development of mature biofilm on membrane surface. This helped in the deposition of organics and inorganics from the bulk feed, which led to microbial community succession in phase 4 with the emergence of the Kallotenue genus. The results suggested that organic substances and microbial communities on membrane surface at different stages in a long-term MD process had a significant influence on MD performance for high-quality wastewater reuse., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 The Authors. Published by Elsevier Inc. All rights reserved.)

Membrane distillation (MD) is a standalone process to generate fresh water and is especially attractive when low-grade waste heat or renewable thermal energy is available. Surface wetting hinders the commercialization of Membrane distillation (MD) technology by deteriorating the permeate quality, thermal efficiency, and transmembrane flux. There is still a lack of understanding on how and to what extent the partially wetted membranes affect the performance of direct contact MD (DCMD) systems. It is of great importance to optimize the operating conditions under such conditions. The DCMD performance was addressed in the literature by considering non-wetted or fully wetted membranes. This study for the first time proposes a computational model to investigate the effect of membrane surface wetting ratio (R = Lwet/Ltotal) on the transmembrane (J) and thermal efficiency (η) of a DCMD module. Parametric and sensitivity analyses were performed to display the effect of system parameters (feed temperature, feed velocity, permeate temperature, permeate velocity, membrane thickness, and membrane surface wetting ratio) on the Key Performance Indicators (KPIs) of the DCMD module. The obtained results indicate that the permeate side temperature has more effect (more than twice) on KPIs in wetted membranes (∼30% and ∼15% rise in J and η) compared to the non-wetted ones (∼15% and ∼5% enhancement in J and η), and the negative effect of membrane surface wetting could be minimized by adjusting the permeate side operational conditions. The effect of membrane wetting ratio on the performance of the DCMD module in thin membranes (≤0.2 mm) and thick membranes (≥0.25 mm) strongly depends on the permeate and feed temperatures. The parametric and sensitivity analysis performed in this study will be beneficial to optimizing the operational conditions of MD systems for maximizing their performance and could serve as valuable guidelines in the development of efficient water desalination systems.

Membrane distillation (MD) is considered as a promising and attractive technology due to its effective production of fresh water. However, the low permeability and easy wetting of MD membranes limit its practical applications. Herein carbon nanotubes (CNTs) and polyvinylidene fluoride-co-hexafluoropropylene (PcH) were used to fabricate nanofiber membranes by electrospinning. Effects of heat-press temperature and CNTs concentration on the morphology and performance of the as-fabricated membranes were systematically investigated. Dye rejections of CNTs/PcH membranes were also studied and role of CNTs played in the as-prepared MD membranes were analyzed. Results suggest that heat-press treatment effectively improved the mechanical strength as well as liquid entry pressure of membranes, and the optimal heat-press temperature was 150 °C. CNTs were proved to be successfully blended in nanofibers. Hydrophobicity and mechanical strength of membranes increased with CNTs incorporation. The 0.5 wt % CNTs loaded membrane heat-pressed at 150 °C exhibited the highest permeate flux (16.5-18.5 L m -2 h -1 ), which signified an increase of 42-50 % compared to the commercial MD membrane (11-13 L m -2 h -1 ) when 35 and 70 g L -1 NaCl solutions were used as feed solutions, respectively. It was noteworthy that salt rejection efficiencies of tested membranes achieved more than 99.99 %. When CNTs/PcH nanofiber membrane was applied to the treatment of dyeing wastewater, the removal rates of acid red and acid yellow reached 100 %. The removal rates of methylene blue and crystal violet were 99.41 % and 99.91 %, respectively. The present study suggested that the as-prepared membranes showed high potential towards MD application., (Copyright © 2021 Elsevier Inc. All rights reserved.)