Bioremediation potential of lime extract (Citrus aurantifolia) on mechanic workshop soil was studied for a period of 56 days. The microbial enumeration was carried out using serial dilution and pour plate method. The bacteria count ranged from 6.3×10 3 to 6.8×10 4 cfu/g for oil free soil (OFS), 0.8×10 3 to 9.8×10 4 cfu/g for mechanic workshop soil (MS) and 1.24×10 4 to 4.16×10 4 cfu/g for mechanic workshop soil amended with lime extract (MSAL). The fungal count ranged from 2.1×10 3 to 2.7×10 3 cfu/g for amended soil, 2.5×10 3 to 3.0× 10 4 cfu/g for unpolluted and 2.2×10 3 to 4.0×10 4 cfu/g for polluted soil. There were significant differences in both bacteria and fungi count at 5% probability level. Micrococcus sp, Staphylococcus sp, Pseudomonas sp, Bacillus sp, Proteus sp Mucor sp, Microsporum sp, Aspergillus niger, Aspergillus flavus, Saccharomyces sp, Rhizopus sp and Aspergillus fumigatus were isolated in this study. MSAL had higher moisture content, phosphorus, organic matter, organic carbon and nitrate compared to OFS and MS. There were significant differences (p<0.05) in the pH, phosphorus, organic matter, organic carbon between OFS, MS and MSAL. This study revealed that lime (Citrus aurantifolia) extract has a potential for remediating mechanic workshop soil.

Microbiological and physicochemical studies of spent lubricating oil contaminated soil amended with wood ash (10% amendment level) were carried out for a period of 56 days. The aim of this study was to evaluate the effect of wood ash in conditioning spent lubricating oil contaminated soil. Serial dilution and pour plate methods were used in enumerating microbial growth. The pH, nitrate, moisture, phosphorus, organic matter content were also determined. The heterotrophic bacteria count ranged from 1.0×10 4 to 2.1×10 4 cfu/g for the oil free soil (OFS), 1.3×10 4 to 2.7×10 4 cfu/g for the polluted control soil (PCS) and 2.1×10 4 to 2.3×10 4 cfu/g for the amended soil (AS) while the fungal count ranged from 4.0×10 3 to 4.7×10 4 cfu/g for OFS, 4.0×10 3 to 8.2×10 4 cfu/g for PCS and 4.0×10 3 to 10.8×10 4 cfu/g for AS. Higher microbial counts were found on the PCS and AS compared to the OFS. There were no significant differences at 5% probability level between the treatments. The organisms isolated were species of Bacillus, Staphylococcus, Micrococcus, Aspergillus, Mucor, Penicillium and Saccharomyces. There were no significant differences (p>0.05) in the moisture content, nitrate, organic matter content and electrical conductivity. However, there were significant differences in the pH, organic carbon and phosphorus contents of the soil samples at 5% probability level. The results obtained in this study demonstrate the potential of wood ash to considerably increase the organic carbon, phosphorus and pH of the soil to slightly alkaline condition which favours the biodegradation of the spent lubricating oil contaminated soil.

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An assessment of mechanic workshop polluted soil treated with 16.6% lime juice (MSAL), mechanic workshop polluted soil treated with lime powder (MSLP) and mechanic workshop polluted soil treated with inorganic lime fertilizer (MSLF) was conducted for a period of 56 days. The study revealed higher microbial counts in the treated soils compared to mechanic oil free soil (MFS). The total viable bacterial counts observed ranged from 1.6×104 cfu/g to 6.8×104 cfu/g for MSF, 2.2×104 cfu/g – 26.2×104 cfu/g for MSAL, 1.2×104 cfu/g -17.2×104 cfu/g for MSLP and 6.8× 104 cfu/g – 16.0 × 104 cfu/g for MSLF while fungi counts ranged from 2.5×104 cfu/g to 6.4×104 cfu/g for MFS, 4.0×104 cfu/g – 16.4×104 cfu/g for MSAL, 2.6×104 cfu/g -3.8×104 cfu/g for MSLP and 2.1× 104 cfu/g – 4.0 × 104 cfu/g for MSLF. Organisms isolated  in the course of the study includes Pseudomonas sp,  Staphylococcus sp, Bacillus sp, Micrococcus sp, Escherichia coli,  Proteus sp, Aspergillus niger, Aspergillus fumigatus, Aspergillus flavus, Mucor sp,  Saccharomyces sp, and Rhizopus sp. The physicochemical results showed that MSAL had higher moisture content, organic matter content, organic carbon, and nitrate than MSF, MSLP and MSLF. There were significant differences in pH, organic matter content, organic carbon, nitrate and phosphorus at 0.05 probability level, but there was no significant different in the moisture content of the soil undergoing treatment. This is an indication that Lime juice has a greater potential in bioremediation of mechanic workshop polluted soil compared to lime powder and inorganic lime fertilizer.