Treatment of saline wastewater using physicochemical, biological, and hybrid processes: Insights into inhibition mechanisms, treatment efficiencies and performance enhancement

The rapid increase in saline wastewater discharge has severely affected the aquatic environment. Furthermore, the presence of salinity in the wastewater severely limits the performance of many wastewater treatment techniques. In this context, the present review article has reported the sources of saline wastewater and its environmental impacts. Wastewater originating from agricultural fields, and various industries, such as aquaculture, tannery, petrochemical, pharmaceuticals, etc., contain a high degree of salinity. The performance of different physicochemical, biological, and hybrid systems in terms of treatment of saline wastewater has been investigated. High salinity levels were found to negatively impact the performance of various physicochemical processes (9 ± 41%) and biological treatment techniques (25 ± 31%). However, processes such as electrochemical oxidation and biological processes operating in the presence of salt-tolerant bacteria showed excellent performance in high salinity. High salinity showed minimal impact on the performance of hybrid systems, which were designed for treating saline wastewater. In this review, the effects of increased salinity on the controlling parameters of various processes have also been elucidated. Recommendations, such as the incorporation of additional pre-treatment units, augmentation of biological systems by salt-tolerant bacteria such as halophiles, etc., have been proposed, which may help to curb down the detrimental effects of high salinity. The present study circumscribes the different aspects of the treatment of saline wastewater, which may be helpful for environmental engineers and researchers working in this field.