Biostimulation of soils contaminated with petroleum products using wastewater sludge: The effect of dehydrogenase activity.

Abstract

The objective of this study was to evaluate the removal efficiencies of total petroleum hydrocarbons (TPH) from soil contaminated with used engine oil and crude oil (doses of 0.5 % and 5%) and to determine the fate of TPH at different temperatures (18 C-omicron and 28 C-omicron) for an incubation period of 12 months. The results of the incubation study indicated that TPH removal percentages in soils contaminated by used engine oil at 18 C-omicron were 69% and 72%, for doses of 0.5% and 5%, respectively. Incubation at 28 C-omicron resulted in higher TPH removals with values of 81% (dose of 0.5%) and 87% (dose of 5%). Higher TPH removal percentages were obtained in a crude oil contamination trial at 18 C-omicron, with values of 88% and 84%, for doses of 0.5 and 5%, respectively. Incubation at 28 C-omicron resulted in higher TPH removals with values of 86% (dose of 0.5%) and 91% (dose of 5%). Dehydrogenase activity levels in used engine and crude oil contaminated soils were apparently lower than those in control soil. Application of wastewater sludge accelerated the DHA levels for all treatment. Based on the first order kinetics model, a high dose of (5%) used engine oil contaminated soil amended with wastewater sludge showed the highest biodegradation rate of 0.00563/day and had a half-life of 123.07 days at the end of incubation period for 28 C-omicron. For crude oil, a high dose of (5%) crude oil contaminated soil amended with wastewater sludge showed a biodegradation rate of 0.00511/day and a half-life of 135.54 days.