NUTRIENT-ASSISTED MICROBIAL REMEDIATION OF HYDROCARBON-CONTAMINATED SOIL IN MECHANIC VILLAGE, UYO, AKWA IBOM STATE, NIGERIA

Abstract

Nutrient boosted microbial breakdown of total petroleum hydrocarbons (TPHs) and heavy metals in soil contaminated by spent engine oil in a mechanic village, Uyo, Akwa Ibom State, Nigeria was assessed for one year. Seven kilograms each of sieved, sterilized spent engine oil impacted soil collected randomly 50 metres apart from 8 locations 0-20 cm deep in the mechanic village, were stored in 8 sterile polythene bags labeled A-H, respectively. Samples A-C were supplemented with 1 kg each of sterile NPK fertilizer, poultry manure, and cow dung, respectively, and D to F were augmented with 2 kg each of the corresponding nutrients. Experimental stands G and H were not boosted with nutrients and served as controls. One thousand milliliters each of microbial consortium was inoculated in A to G accordingly, mixed, and kept. Monitoring for bioremediation of TPHs and heavy metal constituents of the soil was done at a 2-month interval. The results revealed a significant decrease (P<0.05) of TPHs in all nutrient boosted stands when compared to the controls. There was a significant decrease (P <0.05) of TPHs in poultry manure-added soils when compared to soils supplemented with other nutrients. NPK fertilizer augmented stands recorded a significant decrease (P <0.05) of TPHs when compared to cow dung added stands. No significant difference (P>0.05) of TPHs was found in stands supplemented with 1 kg nutrients when compared to 2 kg added stands. Zinc, Iron, Chromium, Nickel, Barium, and Manganese showed significant increase (P<0.05) in stands A to F in the twelfth month of bioremediation when compared to the first month. Lead and copper showed significant decrease (P<0.05) in the sixth and twelfth months, respectively, when compared to the first month. These results implied that the microbial consortium used in this study exhibited degradation potential for TPHs, lead, and copper in spent engine oil-impacted soil boosted with nutrients.