Microbial Bioremediation of Wastewater: Mechanisms, Applications, Challenges, and Emerging Trends

Wastewater contamination resulting from rapid industrialization, urbanization, and agricultural activities has become a major global environmental and public health concern. Conventional physicochemical treatment technologies are often limited by high operational costs, incomplete pollutant removal, and the generation of secondary pollutants. Consequently, microbial-based wastewater treatment and bioremediation have emerged as sustainable, cost-effective, and environmentally friendly alternatives. This review comprehensively examines the role of microorganisms and microbial consortia, in the biodegradation, detoxification, and removal of organic pollutants, heavy metals, nutrients, pathogens, and emerging contaminants from wastewater. The major biological mechanisms involved, including biosorption, bioaccumulation, bioleaching, biotransformation, bio-volatilization, biomineralization, and bioaugmentation, are critically discussed alongside their underlying metabolic pathways. The review further highlights the application of microbial technologies in activated sludge systems, anaerobic digestion, nitrification-denitrification, enhanced biological phosphorus removal. Recent advances in molecular biotechnology, microbial consortia engineering, nano-bioremediation, and CRISPR-assisted microbial enhancement are also explored as promising approaches for improving remediation efficiency. Furthermore, current challenges such as pollutant bioavailability, environmental variability, scale-up limitations, and ecological risks are examined, supported by selected international and Nigerian case studies. Overall, microbial bioremediation represents a promising strategy for sustainable wastewater management and environmental restoration. Future research should focus on integrating advanced biotechnology, systems biology, and process optimization to enhance large-scale implementation and contribute to achieving global water sustainability goals.