Combined impacts of bioaugmentation and vermiremediation on crude oil-contaminated soil: Mitigating strategies for prospective environmental management

Abstract

This study aimed to address the remediation of crude oil-contaminated soil by employing four different factorial setups: I - used the earthworms (Eudrilus eugeniae) for vermiremediation, II – utilized the bacteria (Pseudomonas aeruginosa FA-7) for bioaugmentation, III – combined earthworms + bacteria to perform vermiremediation + bioaugmentation, and IV – served as abiotic control. Further, garden soil weighing 1 kg and 50 g of desiccated cow dung were introduced into the experimental groups and abiotic controls. Subsequently, different quantities of crude oil ranging from 5 to 20 mL were introduced. Based on the results, from 5 mL of oil-contaminated soil, the factorial setup-III removed the maximum proportion of total petroleum hydrocarbons (TPH) in V + B1 (58.06 %). The abiotic control treatments AC1 (1.11 %) exhibited the lowest TPH removal rate. The bioremediated soil had significantly (P < 0.05) different physicochemical properties than the initial crude oil contaminated soil. For instance, earthworm and microbial action resulted in considerable reductions in pH (4.72 %), total organic carbon (44.03 %), total nitrogen (42.42 %), total phosphorus (52.17 %), and total potassium (22.64 %) by the end of the day. On the 60th day of factorial setup-III, the bacterial population (386.470 ± 0.432 CFU × 106 g−1), actinomycetes (188.043 ± 0.246 CFU × 108 g−1), and fungi (16.603 ± 0.202 CFU × 105 g−1) were increased. The germination rates of Trigonella foenum-graecum seeds were increased by 86.6 % in factorial setup III (V + B1) when compared to other factorial setups. Hence, the incorporation of vermiremediation and bioaugmentation provides a distinctive platform for effective oil-contaminated soil remediation.