Applied Environmental Research

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Physical and chemical methods of remediating contaminated soils are less environment-friendly compared to the biodegradation method. This study investigated the ability of selected organic wastes to enhance biodegradation of Spent Engine Oil (SEO) contaminated soil. One kilogram of uncontaminated soil was thoroughly mixed with 10% (w/v) SEO in seven treatments with two replicates. Spent Fruit Residues (SFR), Cassava Peel (CP) and a combination of Bean Husk and Chromolaena odorata(BHC) were added at 10% and20% (w/w), with an untreated control. Total Heterotrophic Bacterial Count (THBC), Total Fungal Count (TFC), Total Hydro-carbon Degrading Bacterial Count (THDBC) and Total Hydrocarbon Degrading Fungal Count (THDFC) of the contaminated and uncontaminated soils were determined using standard micro-biological methods. Isolates were screened for SEO utilization using 2,6-dichlorophenol indo-phenol indicator. Hydrocarbon contents of the soils were determined using Gas Chromatography-Mass Spectrometry (GC-MS). The data obtained were subjected to statistical analysis. The THBC ranged from 1.3x106to 2.9x106CFU g-1, TFC ranged from 5.4x104to 2.0x105CFUg-1, THDBC ranged from 0.5x103to 1.9x104CFUg-1while THDFC ranged from 2.0x103to 1.0x104CFUg-1. The isolated bacteria were Pseudomonas spp., Bacillus spp., Klebsiella spp., Proteus mirabilis, Burkholderia cepacia, Micrococcus luteus, Providencia rettgeri, Enterococcus faecalis, Streptococcus bovisand Enterobacter cloacaewhile the isolated fungi were Candida spp., Aspergillus niger, Saccharomyces cerevisae, Penicillium chrysogenumand Trichophyton sp. Pseudomonas aeruginosaand Aspergillus nigerutilized the oil better than other isolates with absorbance of 0.26 and 0.49 at 600 nm, respectively. The GC-MS revealed that SFR 20% (w/w) treatment had the highest percentage degradation of 70.5%. This study confirms that spent fruit residues can enhance biodegradation of spent engine oil contaminated soil.

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