Investigating petroleum oil bioremediation strategies for crude oil contaminated mining sites in Mpumalanga, South Africa

Abstract

Industrialization has brought to the modern society the benefit of a comfortable modern lifestyle: health-giving pharmaceuticals, labor-saving households appliances, automobiles and ships, paints and detergents, synthetic fibers and polythene packaging, personal computers and televisions, just to name a few from an endless list of manufactured goods. However, behind the luxury and convenience of modern living lies the real price of this industrial production: the generation of hundreds of millions of tons of hazardous waste every year, leading to air, soil and water pollution due to the use of vast quantities of fossil fuels such as petroleum, coal and natural gas as energy sources. In Mpumalanga province, in South Africa, a coal mining company is currently conducting investigations to expand its mining operations near Ogies; the coal is situated below old oil bunkers where crude oil was historically stored. There are concerns that, since not all the crude oil has been removed from the underground storage bunkers, the proposed mining activities may pose a serious environmental threat to the underground and surface water resources in the event of an oil spill or seepage. Petroleum hydrocarbon contains hazardous chemicals such as benzene, toluene, xylenes and naphthalene that expose the local environment to great toxic dangers. Bioremediation, involving nutrient addition, being an economical and eco-friendly approach, has emerged as the most advantageous water clean-up technique for contaminated sites containing toxic metals and organic pollutants. This study investigated the effectiveness of nutrient application treatment compared to natural attenuation on two crude oils from the mine site bunkers: the Alpha bunker and the North and South bunkers. Results of the Alpha bunker crude oil experiments showed that both treatments conducted lead to the degradation of almost 100% of the oil after eight weeks of incubation, and a gradually decreased toxicity level in the water. The results suggested that the native microbial population was able to detoxify hazardous components of the crude oil. Due to the fast degradation rate observed with nutrient addition treatment, we recommended that biostimulation be considered as the in situ oil spill remediation strategy. And for the North and South bunkers crude oil, which responded less to treatments, probably due to its heavy nature, compared to the Alpha bunker crude oil, we suggested a combined treatment technique involving biosurfactants and nutrient addition.