Bioremediation of diesel-contaminated soils by natural attenuation, biostimulation and bioaugmentation employing Rhodococcus sp. EH831

Three bioremediation methods, natural attenuation (NA), biostimulation (BS) and bioaugmentation (BA) were applied to remediate diesel-contaminated soil, with their remediation efficiencies and soil microbial activities compared both with and without surfactant (Tween 80). BA treatment employing Rhodococcus sp. EH831 was the most effective for the remediation of diesel-contaminated soil at initial remediation stage. On the addition of surfactant, no significant effect on the remediation performance was observed. A negative correlation was found between the dehydrogenase activity (DHA) and residual concentration of total petroleum hydrocarbons (TPHs) at below 20,000 mg-TPHs·kg-dry soil ^-1, as follows: DHA μg-TPF(Triphenylformazan)·g-dry soil^-1 d^-1) = -0.02 x TPHs concentration (mg-TPHs·kg-dry soil^-1)+ 425.76 (2500 ≤ TPHs concentration ≤ 20000, p < 0.01).