Influence of Spent Lubricating Oil Spiked Compost on Microbial Counts and Hydrocarbon Degradation Rate in Soils

This study evaluated the influence of organic fertilizers produced from spent lubricating oil (SLO) spiked aerobic composting technique on hydrocarbon degradation rate in soils. The compost windrows (Ft2 and Ft4), consisting of kitchen and agricultural wastes, were spiked with varying concentrations (2% and 4%) of SLO. The resultant organic fertilizers were employed as amendment in pollution simulated potted soils laid out in a complete randomized block design with three replications for 90 days. Results revealed higher counts of hydrocarbon utilizing microbes (HUB: 4.2±0.02×104cfu/g in Ft2, 3.0±0.02×104cfu/g in Ft4; HUF: 3.9±0.2×104cfu/g in Ft2, 2.5±0.02×104cfu/g in Ft4) in spiked compost compared to the control, Ft0 (HUB: 7.9±0.02×103cfu/g; HUF: 6.0±0.2×103cfu/g). Mean count in amended soils reflected a dose-dependent increase which followed the trend: Ft2 ˃ Ft0 ˃ Ft4 for the 5% (3.7×108 cfu/g), 10% (9.2×107 cfu/g) and 15% (6.9×107 cfu/g) levels of fertilizer treatments respectively. There was a significant (P<0.05) reduction in the TPH content of soils after 90days treatment with organic fertilizers. Generally, remediation efficiency followed the order: Ft2 ˃ Ft0 ˃ Ft4, with the highest (11.51%) achieved at 5% Ft2 application. Spiking technique was responsible for the higher counts of hydrocarbon utilizing microbes and enhanced bioremediation associated with the use of fertilizers Ft2.