Optimizing Modern Oxidation Processes for Effective Water and Soil Decontamination

The present research is focused on deepening the knowledge and practical application of advanced oxidation processes (AOPs) for cleaning up polluted water and soil. AOPs are a modern set of treatment techniques that work by generating highly reactive oxidizing agents, mainly hydroxyl radicals (•OH), directly at the site of contamination. These powerful species are effective in breaking down stubborn organic pollutants commonly found in Indian environmental conditions. In this study, the effectiveness of various AOP methods—including Fenton, photo-Fenton, hydrogen peroxide with UV light (H₂O₂/UV), ozone (O₃), ozone with hydrogen peroxide (O₃/H₂O₂), ozone with UV (O₃/UV), and a combination of ozone, hydrogen peroxide, and UV (O₃/H₂O₂/UV)—was assessed by determining the reaction rates for the removal of nitro-phenols. The primary aim was to optimise these processes for better pollutant removal, making them suitable for large-scale implementation in Indian scenarios. Experimental results demonstrated that ozonation induced the formation of quinone-based intermediates, while the mineralization of organically bound nitrogen to nitrate ranged from 50% to 100%, contingent upon the applied treatment conditions. The AOPs substantially enhanced the biodegradability of nitrophenol-laden waters and concurrently reduced their toxicity, thereby establishing their efficacy as effective pre-treatment methods preceding conventional biological filtration processes. Moreover, the application of AOPs, particularly ozonation and Fenton-based treatments, achieved effective remediation of recalcitrant contaminants such as nitrophenols, polycyclic aromatic hydrocarbons (PAHs), diesel, shale oil, and transformer oil within soil matrices. Treatment outcomes exhibited dependency on soil composition; sandy soils facilitated higher contaminant removal efficiencies relative to peat soils, which exhibited enhanced chemical retention and consequent reduction in treatment efficacy. Notably, Fenton-like reactions were operable at native soil pH levels, wherein endogenous iron content catalyzed hydrogen peroxide decomposition without necessitating exogenous ferrous ion supplementation. Critically, synergistic treatment strategies combining chemical oxidation (via ozonation or Fenton chemistry) with biological remediation—employing low-dose oxidants to stimulate microbial degradation—yielded superior contaminant removal compared to either approach employed independently. Economic analyses identified Fenton treatment as the most cost-effective modality for integrated water purification and soil remediation.