Salt-Tolerance Mechanisms of Bacteria and Potential Strategies in Wastewater Treatment

The large amounts of high-salinity wastewater discharged by industrial production and other activities restrict the efficiency and stability of microbial wastewater treatment. Enhancing the salt tolerance of microorganisms can improve biological saline wastewater treatment performance and reduce treatment costs. Understanding the salt-tolerance mechanisms of microbes will improve their widespread application in treating saline wastewater. The objective of this work was to highlight the main salt-tolerance mechanisms in microorganisms, including osmotic regulation and Na+ extrusion, and the related metabolic pathways. Additionally, the role of extracellular polymeric substances and halophilic enzymes in salt tolerance was analyzed. Meanwhile, the mechanistic differences in salt tolerance between halotolerant and halophilic bacteria were comparatively analyzed, while providing a critical evaluation of their effectiveness. Strategies to improve the biological treatment efficiency of high-salinity wastewater, such as the addition of compatible solutes, genetic engineering of halophilic orientation for microorganisms, introduction of related proteins, and modification of biological enzymes, were proposed. These approaches have significant potential for the improvement of biological treatment of high-salinity wastewater. By summarizing the salt-tolerance mechanisms and related potential applications mapped to wastewater treatment, this article provides effective solutions for faster and more efficient high-salinity wastewater treatment.