Critical analysis of enhanced microbial bioremediation strategies of PAHs contaminated sites: Toxicity and techno-economic analysis

Polycyclic aromatic hydrocarbons (PAHs) pose significant threats to environmental integrity and public health due to their high toxicity, persistence, and potential for bioaccumulation. In contaminated soils, PAH concentrations typically range from 1 to 100 mg/kg, with severely polluted areas reaching up to 1000 mg/kg. Conventional bioremediation techniques, limited to 30-50% efficiency, underscore the need for more effective solutions. This review highlights recent advancements in microbial bioremediation strategies, demonstrating removal efficiencies of 80-90% through the utilization of functional microorganisms, which metabolize PAHs into non-toxic compounds. Innovative techniques such as genetic engineering, microbial immobilization, and nanotechnology are shown to achieve over 90% pollutant removal. The review discusses key metabolic pathways and enzymatic processes driving PAH degradation, such as ring-hydroxylation and oxygenation. Technoeconomic assessments indicate up to 40% cost savings and improved energy efficiency compared to conventional methods, facilitating scalability for large-scale environmental restoration projects. Microbial solutions for groundwater pollution, where PAH levels often exceed the maximum contaminant level (MCL) of 0.2 mu g/L, are found to be highly effective in mitigating ecological risks and protecting public health. This comprehensive analysis highlights the promising role of advanced microbial bioremediation techniques in addressing PAH contamination across diverse ecosystems, including soils, sediments, and aquatic environments.