Vermiremediation of engine oil contaminated soil employing indigenous earthworms, Drawida modesta and Lampito mauritii.

Engine oil consists of hazardous substances that adversely affect the environment and soil quality. Bioremediation (employing organisms) is an appropriate technique to mitigate engine oil pollution. In the present study, the earthworm species, Drawida modesta (epigeic) and Lampito mauritii (anecic) were used to restore the soil polluted with polycyclic aromatic hydrocarbons (PAHs) and total petroleum hydrocarbons (TPHs) from used engine oil. Four treatments were set up in addition to positive and negative controls. A maximum of 68.6% PAHs and 34.3% TPHs removal in the treatment with soil (1 kg), cow dung (50 g), used engine oil (7.5 mL) and earthworms was recorded after 60 days. Undoubtedly, earthworms effectively removed PAHs and TPHs from the oil-contaminated soil. PAHs were more strongly accumulated in D. modesta (16.25 mg kg-1) than in L. mauritii (13.25 mg kg-1). Further, histological analysis revealed the epidermal surface irregularity, cellular disintegration, and cellular debris in earthworms. The pH (6.3%), electrical conductivity (12.7%), and total organic carbon (35.4%) were significantly (at P < 0.05) decreased after 60 days; while, total nitrogen (62%), total potassium (76.2%), and total phosphorus (19.2%) were substantially increased at the end of the experiment. The seed germination assay with fenugreek indicates that germination percentage (95%), and germination index (179), were dramatically increased in earthworm inoculated treatments when compared to the negative control (without earthworms). The results reveal that there is a great scope for utilizing the earthworms, D. modesta and L. mauritii for the bioremediation of soils contaminated with PAHs and TPHs.