Improving microbial activity in high-salt wastewater: A review of innovative approaches

The Zero discharge technology has become an important pathroute for sustainable development of high salt wastewater treatment. However, the cohabitation of organic and inorganic debris can cause serious problems such membrane clogging and the formation of hazardous impurity salts that further restrict the recovery of all salt varieties by evaporating and crystallizing. In highly salinized wastewater, biological treatments offer advantages in terms of cost and sustainability when used as a pre-treatment step to eliminate organic debris. On the other hand, high salinity is always a major obstacle to microbial diversity, abundance, and activity, which can result in low organic matter removal effectiveness or the failure of the microbial treatment system. Biofortification techniques can attenuate the negative effects of salt stress and other unfavourable conditions on microorganisms, while the regulation mechanisms of microbial and community collaboration by fortification methods have been an open question. Therefore, a comprehensive summary of the types, mechanisms, and effects of the major biofortification techniques is proposed. This review dialyzes the characteristics and sources of hypersaline wastewater and the main treatment methods. Then, the mechanisms of microbial salt tolerance are summarized and discussed based on microbial characteristics and the protective effects provided by the processes. Finally, the research and application of the main bioaugmentation methods are developed in detail, describing the characteristics, advantages and disadvantages of the different enhancement methods in their implementation. This review provides a more comprehensive perspective on the future engineering applications of bioaugmentation technology, and explores in depth the possibilities of applying biological methods to high-salinity wastewater treatment.