ABSTRACT

Biodegradation of used engine oil contaminated soil using bacteria from such soils was undertaken. Three principal bacteria species, Staphylococcus, Bacillus and Pseudomonas were selected from among the soil isolates and tested for their potency as biodegraders of engine oil in the contaminated soil over a period of 28 days. Results of the preliminary soil analysis showed sand fractions in the range of 64.53% to 68.83% silt 9.50% to 18.33% and clay 16.67% to 22.93%. the soil was also rich in organic matter 3.57% to 4.04% and average moisture content in the range of 21.70% to 23.96% during bioremediation with Bacillus innocula, the bacteria load varied between l.3x107cfu/g to 2.5x107cfu/g in the control soil of site A while the remediated soil for the same site were in the ranges of I .3x1 ü cfu/g to l.09x108cfu/g at the end of the remediation with a reduction of soil content from 4.67% to 2.39% representing 48.8% remediation. Similarly, remediation of 38.21% (2.80% to 1.73%) and 48.47% (4.27% to 2.20%) were recorded in site B and C respectively. The levels of remediation with Psetidomonas species were 53.30% (4.67% to 2.19%), 40% (2.80% to 1.68%) and 50.40% (4.27% to 2.12%) iii the soils of site A, B and C respectively. The bacteria load varied from I .7x10 cfu/g to 3.4x10⁷cfu/g in the control soil of site A while the remediated soil for the same site was in the range of 1.7x10⁷cfu/g tol.55x10⁸cfu/g. the bacteria load of the test soil of site B varied from 1.3x1⁰7cfu/g to 3.0x10⁷cfu/g while the remediated soil ranges from I .3x1 0 cfu/g to I .64x108cfu/g of soil in the same site, while that of site C varied from l.9x10⁷cfu/g to 3.1x10⁷cfu/g for control soil and 1.9x107cfu/g to l.71x10⁸cfu/g for the remediated soil. During bioremediation with Staphylococcus innocula, the bacteria load varied between 1.3x10⁷cfu/g to 2.4x10⁷cfu/g in the control soil of site A while the remediated soil for the same site was in the range of I .3x10 cfu/g to I .04x10⁸ cfu/g while bacteria load varied between 1.2x10⁷cfu/g to l.02x10⁸cfu/g in the control soil of site 4 B while the remediated soil for the same site was in the range of 1.2x10⁷cfu/g to 1.32x10⁸ cfu/g and the bacteria load of site C varied from 1.5x10⁷cfu/g to 3.5x10⁷cfu/g for the control soil while that of the remediated soil varied from I .5x10⁷ cfu/g to 1.23x10⁸cfu/g at the end of the remediation with a reduction of soil content from 4.67% to 3.46% representing 25% remediation for test soil from site A, similarly remediation of 31% (2.8% to 1.91%) and remediation of 33% (4.27% to 2.86%) were recorded for site B and C respectively. Slight but significant variations were recorded in the extent of bacteria biodegradation of the used engine oil contaminated soil with Pseudomonas species being more potent than the Bacillus species and Staphylococcus species as bioremediaters of the soil.