Remediation of crude-oil contaminated groundwater by Fenton-Oxidative method

Water contamination is a major global problem which requires ongoing evaluation and revision of water resources policy at all levels. It has been suggested that it is the leading worldwide cause of disease and deaths; it accounts for the death of more than 14,000 people daily. Groundwater samples were obtained by grab sampling technique from the tap of chemistry department, Delta state University, Abraka, that has its source from a borehole located within the University. Pollution was simulated in the laboratory by contaminating 90 ml of the groundwater samples with 10 ml of crude-oil in plastic microcosm to produce 10% contamination. Optimum conditions obtained for the Fentonoxidative method employed in the study were 250,000mg/l H₂O₂ and 200mg/l FeSO₄ at ambient temperature (28–32°C). At the end of the chemical remediation experiment, the Fentonoxidative method was found to be extremely rapid, with the reaction been exothermic and following second order kinetics. The rate constant of the reaction was 0.00052 mol⁻¹dm³hr⁻¹ with half-life of 0.38 hour. 86.10% removal efficiency of total petroleum hydrocarbon as crude-oil was achieved after six hours. Control experiment was a microcosm that contained contaminated groundwater sample without the treatment chemical solution. Only about 2.83.2% reduction of total petroleum hydrocarbon as crude oil was observed that may be due to evaporation. The Fenton-oxidative method for crude oil-contaminated groundwater gave remediation efficiency of 24.35%(Cd); 31.63%(Pb); 32.58% (Ni) 44.3%; (Cr);98.84%(V). Except for vanadium, where chemical leaching of the metal in acidic medium was very effective, other heavy metal concentrations were higher than maximum permissible levels recommended by World Health Organization (W.H.O). This suggests that Fenton-oxidative method is not effective in the removal of Cd, Pb, Ni and Cr from groundwater polluted with crude-oil. The remediated polluted groundwater sample was found to have most of its physicochemical parameters as close match with the unpolluted groundwater sample and World Health Organization (W.H.O) permissible limits. The overall implication is that crude-oil polluted groundwater remediated by Fentonoxidative method needs post-treatment to improve on its portability for drinking/domestic and agricultural uses.