Bioremediation of hydrocarbon contaminated soil using local organic materials and earthworms

• Published in: Environmental pollution (1987) 2022-12, Vol.314, p.120169-120169, Article 120169
• Main Authors: Nobili, Sofia, Masin, Carolina Elisabet, Zalazar, Cristina Susana, Lescano, Maia Raquel
• Format: Article
• Language: English
• Subjects: Bioremediation; Earthworms; Soil contamination; Total petroleum hydrocarbons
• ISSN: 0269-7491; 1873-6424
• DOI: 10.1016/j.envpol.2022.120169

Bioremediation technologies have demonstrated significant success on biological quality recovery of hydrocarbon contaminated soils, employing techniques among which composting and vermiremediation stand out. The aim of this study was to evaluate the efficiency of these processes to remediate diesel-contaminated soil, employing local organic materials and earthworms. During the initial composting stage (75 days), the substrate was made up using contaminated soil, lombricompost, rice hulls and wheat stubbles (60:20:15:5% w/w). Diesel concentration in the contaminated substrate was about 5 g kg−1, equivalent to a Total Petroleum Hidrocarbons (TPH) experimental concentration of 3425 ± 50 mg kg−1. During the later vermiremediation stage (60 days), the earthworm species Eisenia fetida and Amynthas morrisi were evaluated for their hydrocarbon degradation capacity. Physicochemical and biological assays were measured at different times of each stage and ecotoxicity assays were performed at the end of the experiments. TPH concentration reduced 10.91% after composting and from 45.2 to 60.81% in the different treatments after vermiremediation. Compared with TPH degradation in the treatment without earthworms (16.05%), results indicate that earthworms, along with indigenous microorganisms, accelerate the remediation process. Vermiremediation treatments did not present phytotoxicity and reflected high substrate maturity values (>80% Germination Index) although toxic effects were observed due to E. fetida and A morrisi exposure to diesel. Vermiremediation was an efficient technology for the recovery of substrate biological quality after diesel contamination in a short period. The addition of organic materials and suitable food sources aided earthworm subsistence, promoted the decontamination process and improved the substrate quality for future productive applications. [Display omitted] •Bioremediation was evaluated to recover biological quality of contaminated soil.•The vermiremediated substrates indicated maturity and no phytotoxicity.•Vermiremediation was an effective technology for hydrocarbons soil removal.•Composting was a necessary prior stage to enhance the substrate for earthworms.