Use of Wastewater from Legume Cooking in Bioremediation of Crude-Oil Polluted Soil

Abstract

Wastewaters generated from the cooking of foods contain nutrients. Such wastewaters may have the potential to be used as nutrients in bioremediation of hydrocarbon polluted environments. In this study, use of wastewaters generated from the cooking of two legumes as nutrient source during bioremediation of hydrocarbon polluted soil was investigated. Crudeoil polluted soils were treated with wastewater from cooking of cowpea (setup B), wastewater from cooking of groundnut-pods (setup G), a mixture of the wastewaters (setup B+G), and tap-water (control setup: setup C). Selected microbial group and physicochemical parameters were determined at seven days interval. The results obtained showed that the extent of hydrocarbon degradation in setup B, G, B+G, and C were 45.5, 23.2, 1.3, and 37.9 % respectively. There was decrease in total organic carbon (TOC), phosphorus, and nitrogen in the setups. However, in setup G there was increase in TOC. Setup C and B had the highest decrease in phosphorus, and setup B had the highest decrease in nitrogen. There was decrease and subsequent increase in percent hydrocarbon-utilizing bacteria in all the setups; the subsequent increase was highest in setup B. There was generally a decrease in percent hydrocarbon-utilizing fungi, except in setup C. The hydrocarbon utilizing microorganisms isolated from the treated soils include Bacillus, Micrococcus, Acinetobacter, Staphylococcus, Pseudomonas, Penicillium, Aspergillus, Candida and Fusarium. Their presence indicates that hydrocarbon degradation was due to biodegradation. It is concluded that wastewater from cooking of cowpeas can be applied in bioremediation of crude-oil polluted soil.