Aerobic biodegradation of sludge with high hydrocarbon content generated by a Mexican natural gas processing facility

The biodegradation of oil sludge from Mexican sour gas and petrochemical facilities contaminated with a high content of hydrocarbons, 334.7 ± 7.0 g kg−1 dry matter (dm), was evaluated. Studies in microcosm systems were carried out in order to determine the capacity of the native microbiota in the sludge to reduce hydrocarbon levels under aerobic conditions. Different carbon/nitrogen/phosphorous (C/N/P) nutrient ratios were tested. The systems were incubated at 30 °C and shaken at 100 rpm. Hydrocarbon removals from 32 to 51% were achieved in the assays after 30 days of incubation. The best assay had C/N/P ratio of 100/1.74/0.5. The results of the Microtox® and Ames tests indicated that the original sludge was highly toxic and mutagenic, whereas the best assay gave a final product that did not show toxicity or mutagenicity.