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The harmful effects arisen from the discharge of saline wastewater have become more evident in recent years and therefore drawn much public concerns. Saline wastewater, including produced water, tannery wastewater, textile wastewater and aquaculture wastewater, contains various organic pollutants and inorganic dissolved ions. These saline wastewaters can be treated, not only to meet the discharge standard but also to offer the opportunities for water reuse and nutrient recovery. Membrane technology is a promising technology that offers attractive solutions for effective saline wastewater treatment and resource recovery. With the tremendous development made in this realm, this review is set to provide a frame of state-of-the-art approaches for saline wastewater treatment based on membrane technology and stimulate ideas to enhance the treatment efficiency and sustainability in these related works. The unique features, strengths and limitations of pressure-driven, osmotically-driven, thermally-driven and electrically-driven membrane processes in treating saline wastewater and resource recovery are discussed. This review aims to consolidate the literature related to membrane technology as a versatile tool for saline wastewater treatment, as well as to identify the current research gaps and areas of improvement related to this field. • Various membrane-based separation processes for saline wastewater treatment and resource recovery are discussed. • Pressure-driven membrane processes are reliable and effective for saline wastewater treatment and recovery. • Forward osmosis, membrane distillation and electrodialysis are feasible alternatives. • Integrations among membrane processes or with conventional treatment processes provide more holistic solutions. • The current research gaps and the future directions are highlighted. [ABSTRACT FROM AUTHOR]

• PW handling with conventional technologies is compared with MD highlighting constraints. • Advances in energy sourcing for MD incorporating solar energy, waste heat and microwave heating. • More insight on fouling and mitigation strategies peculiar to MD of PW. • Competitiveness of MD as an alternative for desalination of PW amidst environmental concern. • Beneficial reuse of PW for irrigation agriculture. Membrane distillation (MD) has proved worthwhile in treatment of hypersaline feeds demonstrating near complete rejection of dissolved solutes without any effect on the process conditions. This makes it potential treatment option for hypersaline oilfield produced water (PW) with salinity level far greater than that of seawater. Polymeric membranes have recently garnered more attention than their ceramic counterparts in oily wastewater treatment owing to ease of synthesis and relative cost advantage. However, lower mechanical durability and the propensity for fouling of these membranes due to presence of low surface energy organics in PW ultimately affects MD performance in its treatment. Studies elucidating the mechanism of fouling between PW feed and membranes in MD is scarcely reported in the literature. Various fouling mitigation approaches have shown promise towards the realization of MD as a viable option for PW treatment. Hybridization of MD, use of (super)hydrophobic MD membranes with feed pre-treatment using other technologies and/or membrane post-cleaning, integrated MD systems and recently omniphobic and Janus modifications of MD membranes have all been reported for treatment of PW showing more promise towards achieving ultrapure-distillate treatment. In this article, the performance of these polymeric MD membranes used in PW treatment in comparison to the other conventional treatment options as well as advances in MD as a cost-effective alternative for beneficial re-use of PW is reviewed, highlighting the areas requiring further study for this line of research. Because MD is still largely energy inefficient, several efforts to realize it as an all-round competitive technology focusing on long-term stability, brine handling capacity and potentials for cost savings with alternative and rather sustainable energy source are also discussed. [ABSTRACT FROM AUTHOR]

[Display omitted] • Boron doped TNT immobilized on the outer layer of a dual layered PVDF hollow fiber membrane. • A finger-like structure on both outer and inner layer, sandwiching a dense interlayer. • PVDF-L2% exhibited a maximum flux of 39.62L/m2h and colour removal of 79.42%. • Membrane recovered more than 95% of performance after 4 filtration cycles, exhibiting antifouling propensity. • Long term study confirms membrane usability over 20 days. The emergence of hybrid photocatalytic membranes has provided a new direction in search of efficient technologies to separate and degrade pollutants present in wastewaters. Colour pigments originated from different sources including agricultural waste pose serious threats towards water bodies as their presence will lead to multiple environmental problems. This study investigated the potential of a photocatalytic dual layered hollow fiber membrane (DLHFM) incorporated with boron doped titania nanotubes (TNT-B) photocatalyst for the photodegradation and removal of colour pigment molecules present in aerobically treated palm oil mill effluent (AT-POME). The colour removal efficiencies and separation performance of the DLHFM were evaluated through a submerged membrane photo reactor (SMPR) system driven by visible light. Polyvinylidene fluoride-based DLHFM loaded with 2% of photocatalyst (PVDF-L2%) exhibited the best membrane performance with a flux of 39.62 L/m2h and colour removal efficiency of 79.42%. The controlled distribution of photocatalysts as well as the synergistic combination of membrane filtration and photodegradation concertedly contributed to the improvement in membrane's performance. 95% of flux and colour removal efficiency were sustained after four filtration cycles. The membrane exhibited efficient performance in terms of consistent flux and colour removal efficiency after 20 days of continuous photocatalytic filtration, implying their high long-term stability. This study highlights the efficiency and potential of visible light photocatalytic membranes in treating colour laden wastewaters. [ABSTRACT FROM AUTHOR]