Membrane Distillation (MD) is a membrane-based, temperature-driven water reclamation process. While research emphasis has been largely on membrane design, upscaling of MD has prompted advancements in energy-efficient module design and configurations. Apart from the four conventional configurations, researchers have come up with novel MD membrane module designs and configurations to improve thermal efficiency. While membrane design has been the focus of many studies, development of appropriate system configurations for optimal energy efficiency for each application has received considerable attention, and is a critical aspect in advancing MD configurations. This review assesses advancements in modified and novel MD configurations design with emphasis on the effects of upscaling and pilot scale studies. Improved MD configurations discussed in this review are the material gap MD, conductive gap MD, permeate gap MD, vacuum-enhanced AGMD/DCMD, submerged MD, flashed-feed MD, dead-end MD, and vacuum-enhanced multi-effect MD. All of these modified MD configurations are designed either to reduce the heat loss by mitigating the temperature polarization or to improve the mass transfer and permeate flux. Vacuum-enhanced MD processes and MD process with non-contact feed solution show promise at the lab-scale and must be further investigated. Hollow fiber membrane-based pilot scale modules have not yet been sufficiently explored. In addition, comparison of various configurations is prevented by a lack of standardized testing conditions. We also reflect on recent pilot scale studies, ongoing hurdles in commercialization, and niche applications of the MD process.

Membrane technology has shown a promising role in combating water scarcity, a globally faced challenge. However, the disposal of end-of-life membrane modules is problematic as the current practices include incineration and landfills as their final fate. In addition, the increase in population and lifestyle advancement have significantly enhanced waste generation, thus overwhelming landfills and exacerbating environmental repercussions and resource scarcity. These practices are neither economically nor environmentally sustainable. Recycling membranes and utilizing recycled material for their manufacturing is seen as a potential approach to address the aforementioned challenges. Depending on physiochemical conditions, the end-of-life membrane could be reutilized for similar, upgraded, and downgraded operations, thus extending the membrane lifespan while mitigating the environmental impact that occurred due to their disposal and new membrane preparation for similar purposes. Likewise, using recycled waste such as polystyrene, polyethylene terephthalate, polyvinyl chloride, tire rubber, keratin, and cellulose and their derivates for fabricating the membranes can significantly enhance environmental sustainability. This study advocates for and supports the integration of sustainability concepts into membrane technology by presenting the research carried out in this area and rigorously assessing the achieved progress. The membranes’ recycling and their fabrication utilizing recycled waste materials are of special interest in this work. Furthermore, this study offers guidance for future research endeavors aimed at promoting environmental sustainability.

While phenomenal strides are being made on the technological front, the water industry lags behind other sectors in the adoption of innovative techniques. Contributing factors include long lifetimes and costs of previous water infrastructure, risk aversion due to public health concerns surrounding water access, and low financing for innovation. While many professionals see the need for innovation, they prefer traditional tried and tested routes. Regulations may be useful in accelerating the transition to sustainable technologies. Furthermore, the literature emphasizes the role of environmental, social, and political actors, as well as their interplay in realizing innovation in the water sector.

Limitations in existing anion exchange membranes deter their use in the efficient treatment of industrial wastewater effluent. This work presents an approach to fabricating novel anion-conducting membranes using epoxy resin monomers like hydrophobic or hydrophilic diglycidyl ether and quaternized polyethyleneimine (PEI). Manipulating the diglycidyl ether nature, the quantitative composition of the copolymer and the conditions of quaternization allows control of the physicochemical properties of the membranes, including water uptake (20.0–330%), ion exchange capacity (1.5–3.7 mmol/g), ionic conductivity (0.2–17 mS/cm in the Cl form at 20 °C), potentiostatic transport numbers (75–97%), as well as mechanical properties. A relationship was established between copolymer structure and conductivity/selectivity trade-off. The higher the quaternized polyethyleneimine, diluent fraction, and hydrophilicity of diglycidyl ether, the higher the conductivity and the lower the permselectivity. Hydrophobic diglycidyl ether gives a much better conductivity/selectivity ratio since it provides a lower degree of hydration than hydrophilic diglycidyl ether. Different mesh and non-woven reinforcing materials were also examined. The developed membranes demonstrate good stability in both neutral and acidic environments, and their benchmark characteristics in laboratory electrodialysis cells and batch-mode dialysis experiments are similar to or superior to, commercial membranes such as Neosepta© AMX, FujiFilm© Type1, and Fumasep FAD-PET.

Membrane distillation (MD) is a versatile low-temperature separation process used for desalinating saline solutions with high salt rejection rates. Its current drawbacks include low flux and high energy demand. This study presents localized electrically induced heating using ceramic-coated metallic spacers to improve MD performance. We coated Ni-Cr spacers with MgO via electrolytic deposition and calcination, optimizing for a crack-free protective surface. Smaller wire diameter Ni-Cr exhibited superior heating. When a periodic current of 0.2 A cm⁻² was applied, permeate flux increased by 15% although energy consumption only increased by 4%. Continuous supply of high-grade electrical energy added no further performance improvement as compared to periodic application. Our work highlights a spacer-based approach for localized Joule heating in MD systems without compromising membrane structure, while exploring coating systems to protect conductive spacers and optimizing schemes for electrically controlled performance.