A simple methodology to evaluate influence of H 2O 2 and Fe 2+ concentrations on the mineralization and biodegradability of organic compounds in water and soil contaminated with crude petroleum

Abstract

Simple measurements of H 2O 2 concentration or CO 2 evolution were used to evaluate the effectiveness of the use of Fenton's reagent to mineralize organic compounds in water and soil contaminated by crude petroleum. This methodology is suitable for application in small treatment and remediation facilities. Reagent concentrations of H 2O 2 and Fe 2+ were found to influence the reaction time and temperature, as well as the degree of mineralization and biodegradability of the sample contaminants. Some H 2O 2/Fe 2+ combinations (H 2O 2 greater than 10% and Fe 2+ greater than 50 mM) resulted in a strong exothermic reaction, which causes peroxide degradation and violent gas liberation. Up to 75% TOC removal efficiency was attained in water and 70% in soil when high H 2O 2 (20%) and low Fe 2+ (1 mM) concentrations were used. Besides increasing the degree of mineralization, the Fenton's reaction enhances the biodegradability of petroleum compounds (BOD 5/COD ratios) by a factor of up to 3.8 for contaminated samples of both water and soil. Our experiments showed that low reagent concentrations (1% H 2O 2 and 1 mM Fe 2+) were sufficient to start the degradation process, which could be continued using microorganisms. This leads to a decrease in reagent costs in the treatment of petroleum-contaminated water and soil samples. The simple measurements of H 2O 2 concentration or CO 2 evolution were effective to evaluate the Fenton's reaction efficiency.