Bioremediation of Petroleum Hydrocarbon Contaminated Soil by Balanites aegyptiaca (L) Del and its Rhizospheric Bacteria

Abstract

Phytoremediation is an emerging technology for cleaning crude-oil-contaminated soil. The aim of this study was to test the leguminous plant Balanites aegyptiaca (L.) Del. for its efficiency in remediating soil polluted with 0.5%, 1.0%, 1.5% and 2.0% (w/w) crude oil and its ability to enhance the activity of soil microorganisms. Standard methods were used to measure plant parameters, degradation percentage, total petroleum hydrocarbons and bacterial count. The results showed that crude oil concentration did not adversely affect plant growth, indicating the potential success of the phytoremediation process. Shoot length was not negatively affected by oil, compared with the control plant, up to a concentration of 1.5% for six months. Crude oil degradation percentages ranged from 49% to 74%. The highest degradation percentage was recorded in soil collected from beneath Balanites aegyptiaca (L.) Del. seedlings (74%). Viable microorganism counts in oil-contaminated soil at all tested concentrations were significantly (P <= 0.01) higher than those in oil-free soil at each sampling interval. The high biodegradation efficiency achieved using Balanites aegyptiaca (L.) Del. indicates a possible plant-associated mechanism for remediating crude-oil-contaminated soil. Balanites aegyptiaca could be used to clean up oil-contaminated soil after further testing under field conditions.