The Effects of Enrichment Nutrients on the Growth of Indigenous Bacteria Species in Spent Lubricating Oil Contaminated Water

Aim: This study was conducted to compare the effects of enrichment nutrients, NPK (Nitrogen, Posphorus, Potassium) and organic wastes on the growth of indigenous bacterial species in spent lubricating oil contaminated water. Six bacterial species which were isolated from spent lubricating oil impacted soils (Pseudomonas sp., Bacillus sp., Actinomyces sp., Acinetobacter sp., Enterobacter sp., and Micrococcus sp.,) and showed profuse utilization of spent lubricating oil on screening, were used for this study.

Place and Duration of Study: The study was conducted in the laboratory of the Department of Environmental Management and Toxicology, Federal University of Petroleum Resources, Effurun, between 2018 and 2019.

Methodology: The study and was conducted using Mineral Salts Medium broth, spent lubricating oil substrate and NPK (20:10:10), Chicken droppings and Cow dung as nutrient sources (biostimulants). The effect of the biostimulants on the growth of the bacterial isolates was assessed weekly for 14 days by measuring the turbidity, bacterial counts and pH.

Results: Pseudomonas sp. recorded the highest count of 1.16E+19 CFU/ml, 2.53E+17 CFU/ml and 1.74E+14 CFU/ml for biostimulation with NPK, Chicken droppings and Cow dungs respectively. The treatment with NPK enhanced the bacterial isolates most, of the three treatments used at the end of the test period. The pH values obtained for the test cultures at the end of the study, ranged from 6.52±0.02 for Enterobacter sp. in Cow dung treated cultures to7.85±0.03 for Pseudomonas sp.in NPK treated cultures. The values were within the optimum biodegradation range of 6.50 -8.50. There was significant difference between the bacterial counts obtained with the cultures treated with NPK and Chicken droppings (P=0.006), between NPK and cow dungs (P = 0.031) and between NPK and the control (P = 0.033). The study affirms the benefits of using organic wastes in the bioremediation process of hydrocarbon contaminated sites; it enhances the nutrients required by the bacteria for the remediation process and it’s a waste management strategy for disposing these organic wastes at very minimal costs and in an ecofriendly manner.