Microbial remediation of tannery wastewater

Abstract Tannery wastewater contains a diverse range of hazardous pollutants like acids, solvents, and heavy metals, particularly chromium, dyes, and many other organic and inorganic compounds. These compounds impart genotoxic, carcinogenic, and cytotoxic effects on life forms, which consume tannery wastewater mixed water for their living. Conventional methods such as electrocoagulation, advanced oxidation processes, electrochemical methods, membrane filtration, ozonation, several adsorbents, and precipitation have been used for the treatment of tannery wastewater. These methods are less preferred over biological methods as most of them are expensive and/or cause secondary pollution. Several biological methods such as treatment with biomass and biochar, activated sludge, microbial fuel cells, bioelectrochemical systems, microbial consortium, wetland systems, membrane bioreactors, phytoremediation, aerobic/digestion, and enzymes have been tested and reported to be cost effective as well as ecofriendly methods. The treatment with enzymes like protease immobilized on a catalyst has resulted in effective degradation of protein rich tannery effluent. Bioelectrochemical systems come with dual advantages of being cost-effective treatment method and simultaneously generating electricity by treating wastewater. Genetically modified organisms having high salt tolerance were created, which enhanced the wastewater treatment efficiency. Several biological strategies or combination of biological and physicochemical methods have been reported to treat tannery wastewater with higher efficiency. The present chapter discusses the characteristics of tannery wastewater, its impact on environment and life forms. It further offers an overview of physicochemical methods and describes in depth the microbial treatment strategies of tannery wastewater.