Different bioremediation techniques (natural attenuation, biostimulation and bioaugmentation) in
contaminated soils with two oily sludge concentrations (1.5% and 6.0%) in open and closed microcosms
systems were assessed during 90 days. The results showed that the highest biodegradation rates were
obtained in contaminated soils with 6% in closed microcosms. Addition of microbial consortium and
nutrients in different concentrations demonstrated higher biodegradation rate of total petroleum hydrocarbons
(TPH) than those of the natural attenuation treatment. Soils treated in closed microcosms
showed highest removal rate (84.1 ± 0.9%) when contaminated at 6% and bacterial consortium and
nutrients in low amounts were added. In open microcosms, the soil contaminated at 6% using biostimulation
with the highest amounts of nutrients (C:N:P of 100:10:1) presented the highest degradation
rate (78.7 ± 1.3%). These results demonstrate that the application of microbial consortium and nutrients
favored biodegradation of TPH present in oily sludge, indicating their potential applications for treatment
of the soils impacted with this important hazardous waste.