Stimulated Biodegradation of Spent Lubricating Motor Oil in Soil Amended with Animal Droppings

Abstract

The potentials of organic wastes from animal droppings as bioremediation alternative for soils spiked with waste-lubricating motor oil (spent oil) was evaluated. The rate of biodegradation of the spent oil was studied for a period of 6 months under laboratory condition. The result of the microbial counts for soils spiked with 5000 mgkg-1(0.5%) spent oil has its total heterotrophic bacterial count in unamended control soil ranging from 2.71±0.09 to 7.21±0.25 x 106 CFU/g of soil, while those of soil amended with cow droppings (CD) ranged from 16.0±1.01 to 47.90±0.36x 106 CFU/g of soil and those of soil amended with goat droppings (GD) and poultry manure(PM) ranged from 16.6±0.6 to 57.9±0.15 x 106 and 18.00±0.20×106 to 60.80± 1.19 ×106 CFU/g of soil respectively. The counts of hydrocarbon-utilizing bacteria (HUB) in unamended control soil ranged from 0.93±0.11 to 2.10±0.15 ×106 CFU/g of soil. The count of HUB in PM amended soil was significantly higher than those amended with goat droppings (GD), while those of goat dropping were higher than those of cow dung. The HUB count in GD amended soil ranged from 8.07± 0.12x106 to 67.70±0.68 x 106 cfu/g of soil. The THB and HUB counts for soils spiked with 25000 mg/kg (2.5%) spent oil exhibited a similar trend as was observed for soil spiked with 0.5% spent oil. Evaluation by the first-order kinetic model which utilized combined data for the entire period revealed that PM with biodegradation rate constant of 0.2332 day-1 and half-life of 2.97days was better in stimulating biodegradation of oil at higher concentration, while GD with a biodegradation constant of 0.3253day-1 and half-life of 2.13 days performed better at low pollution when compared to that of PM and CD.