Abstract

This paper reports a study that measured the effect of some heavy metals at different concentrations (Lead 0.86 ppm, Copper <0.001 ppm, Manganese 0.05 ppm, and Nickel <0.001 ppm) in well water contaminated with petroleum hydrocarbon on biodegradation by a consortium of hydrocarbon utilizing bacteria and fungi, using distilled water amended with 5% bonny light crude oil and varying concentrations of the salts of the heavy metals described earlier, either singly or combined. Also the effects of these heavy metals on the physicochemical characteristics of the treatments were analysed after 14 days. The control (no heavy metal addition) had the highest percentage of total petroleum hydrocarbon reduction (81.66%). There was no significant difference in total petroleum hydrocarbon  reduction in Copper, Nickel, Lead and the combination of the heavy metals Copper, Nickel, Manganese and Lead at P≥0.05, while percentage of total petroleum hydrocarbon  degraded of  well water and Manganese was 35.29 and 59.67%, respectively and showed significant difference (P≤0.05) from the control. Electrical conductivity, salinity, temperature, total dissolved solid, dissolved oxygen and pH in various treatments showed no significant difference (P≥0.05), but Biological Oxygen Demand of Lead was significantly different (P≤0.05) from the control. These results suggest that the heavy metals present interfere with the extent of biodegradation of petroleum hydrocarbons in water.

Key words: Well water, petroleum hydrocarbons, heavy metals, bacteria and fungi consortia, biodegradation.