Biostimulatory potentials of plantain skin on soils polluted with used motor oil

Bioremediation based only on the activity of microorganisms has repeatedly proven inadequate. This has necessitated the adoption of organic amendments/ organic wastes in stimulating the activities and growth of hydrocarbon degraders. The present study employed gravimetry in investigating the efficiency of plantain skin (PLS) in the bioremediation of 10% (v/w) used motor oil (UMO) polluted soil over a period of 42 days using n-hexane as an extractant. UMO polluted soil was treated with three different concentrations of PLS (5%, 10%, and 15% W/W). The effectiveness of the organic waste treatment in removing the UMO contaminant was determined using Seed Germination Toxicity test. After 42 days, 17.56% UMO loss was observed in the control set up (untreated UMO polluted soil), and 61% UMO loss was observed in the 15% PLS treated set up. Significant level of Hydrocarbon-utilizing bacteria (HUB) counts (P ≤ 0.05) were recorded in the PLS-treated options, ranging from 4×10⁷ to 19.1 ×10⁷ CFUg^-1 of soil, in comparison to the HUB counts in the untreated control set up, which ranged from 0.2×10⁷ to 7.1×10⁷ CFU g^-1. Furthermore, fungal colony counts in the PLS-treated options varied from 3.8×10⁵ to 5.3×10⁶ CFU g^-1, which were greater than the fungal counts in the control option with a range of 0.1×10⁵ to 6.4×10⁵. In addition, the treated options had a germination index (GI) ranging from 62.52% to 84.78%. Overall, the treated options had significantly higher (P ≤ 0.05) microbial growth, oil loss, and germination indices. Plantain skin therefore proved to be an alternative biostimulatory alternative organic waste for enhanced bioremediation of used motor oil polluted soils.