Remediation of Petroleum Refinery Waste Contaminated Soil at Alesa-Eleme, River State

Soil contamination by hydrocarbons and trace metals has led to adverse environmental and ecological impacts globally. As with the case in most third-world countries like Nigeria, where legal and illegal oil refineries do not follow or implement the national policies and guidelines for the treatment of industrial waste products before these waste products are disposed of into the environment. In this study, petroleum wastes contaminated soil at Alesa, Eleme resulting from the different production processes of petroleum products, was investigated to know the extent of contamination by heavy metals such as Iron (Fe), Zinc (Zn), Lead (Pb), Sulphates (SO4), Phosphates (PO4) and organic hydrocarbons like Phenols which are very dangerous to the environment and how they can be remediated by chemical and biological remediation methods and finding out which method is more cost-effective and environmentally friendly and sustainable. The extent of contamination of the soil was determined by the collection of soil samples from randomized sample points with coordinates 290223.14N 527592.55E, 290260.98N 527694.41E and 290326.19N 527622.51E at the affected area using a Standard Soil Auger at a depth of 15 – 30 cm (subsoil), the soil was then pretreated and their physiochemical properties were determined and later analyzed for the presence of heavy metals under a laboratory controlled experiment. High concentrations of heavy metals and hydrocarbons were found to be present in the soil from the affected area, this could also be seen in a common dominant shrub locally known as stubborn grass (Sida acuta) which was also analyzed for the presence of heavy metals. Chemical remediation (using EDTA/Oxalic acid) and biological remediation methods (phytoremediation) using Sunflower (Helianthus annus) were carried out to treat the contaminated soil and the rate of removal of contaminants through phytoremediation was calculated at 6 weeks and 9 weeks intervals to know the extent to which the contaminants were removed from the soil. The remediation methods were proofed to be very effective. The results of one-way analysis of variance of the contaminated soil at 6 weeks and 9 weeks during the phytoremediation process were 3.014 and 49.2 respectively and this revealed that there was a significant difference between the concentrations of contaminants with an F value of 0.575 which is greater than the F-Critical value for the alpha level selected (0.05). It was recommended that the Government’s Ministry of Environment at all levels, should adopt and enforce sound waste management practices for refinery wastes and phytoremediation should be considered in reviving soil contaminated by refinery waste