Stimulated biodegradation of waste lubicating oil in soil, using water hyacinth and goat droppings

Abstract

Funmilayo Doherty, Idowu Aneyo, Nimota shobowale

Background: Soil contamination with used engine oil is becoming a major environmental problem due to uncontrollable disposal, particularly in developing countries. Eichhornia Crassipes (water hyacinth) has been recognized as the world’s most harmful weed. The aim of this research is therefore to determine the potentials of water hyacinth and goat droppings in enhancing biodegradation of used engine oil in soil. Materials and methods: Water hyacinth plants were chopped, sun dried and ground into powder. It was autoclaved at 1210C for 15 minutes. 200g of Soil was placed in vessels labelled A,B and C, 2.5% of used lubricating motor oil was added, pulverised, and left undisturbed. After 2 days 10% of each organic waste (ground water hyacinth and goat droppings) was added to each vessel of oil polluted soil, labeled A and B. Vessel C with only soil and used lubricating oil served as control. Periodic sampling was carried out at 15 days interval for 75 days. Soil samples were collected from different areas of the microcosm for isolation and enumeration of bacteria and determination of total petroleum hydrocarbon. Results: Microbial growth was highest in contaminated soil amended with water hyacinth with total heterotrophic bacteria count ranging from 20×107 to 68×107 cfu/g and total hydrocarbon utilizing bacteria count ranging from 10×106 to 40×106cfu/g. This was closely followed by soil amended with goat droppings with total heterotrophic bacteria count ranging from 18.8×107 to 60×107cfu/g and hydrocarbon utilizing bacteria count ranging from 8.5×106 to 38×106cfu/g. Unamended soil had the lowest microbial count with total heterotrophic bacteria count ranging from 4.0×107 to 7.2107cfu/g and 7.5×106 to 20×106cfu/g for hydrocarbon utilizing bacteria count. 91% loss in hydrocarbon was observed in the water hyacinth amended soil. Conclusion: The biostimulative effect was observed with the increase in microbial population count in contaminated soil amended with water hyacinth. This study confirms that water hyacinth and goat droppings have the potential to stimulate bioremediation of hydrocarbon polluted soil.