Effect of sulphur species on the hydrocarbon biodegradation of oil sludge generated by a gas processing facility

Abstract

Oily sludge from gas processing facilities contains components that are major environmental pollutants. Biodegradation is an alternative treatment, but can be affected by other components of the sludge, such as sulphur compounds, so it is important to evaluate the effect of these on oil biodegradation in order to prevent negative impacts. This work studied the transformation of sulphur compounds in oily sludge biodegradation systems at the microcosm level. The predominant sulphur compounds in the original sludge were elemental sulphur and pyrite (9,776 and 28,705.4 mg kg -1 , respectively). In the biodegradability assays, hydrocarbon concentrations decreased from 312,705.6 to 186, 760.3 mg kg -1 after 15 days of treatment. After this time, hydrocarbon degrading activity stopped, corresponding with a decrease in hydrocarbon degrading bacteria. These changes were related to a reduction in pH that inhibits biodegradation. During the assay, sulphur compounds were gradually oxidized and transformed. The concentration of sulphate increased from 5,096 to 64,868.3 mg kg -1 after 30 days in the assay, although controls were unchanged. Therefore, it is important to determine changes to the main compounds of the waste in order to assess their impact.

Richness of drilling sludge taken from an oil field quagmire: potentiality and environmental interest

“…In addition, these indigenous microbial populations could be highly adapted to the toxic effects of petroleum or its degradation products (Wesp et al 2000). It is noteworthy that this significant amount of indigenous microorganisms favored in situ biological treatment processes of the drilling quagmire, which has been proved by previous works that showed the feasibility of hydrocarbon biodegradation of oil sludge by the native microbiota (Reyes-Avila et al 2013). It has been noted that the microbial properties affecting biodegradation of hydrocarbons concern genetic complement and the expression and regulation of microbial genes, surface hydrophobicity, metabolic diversity and flexibility, substrate uptake or adherence mechanisms, tolerance to solvent effects, adaptation to environmental conditions and competition with other microbes belonging to the same flora (Abbasnezhad et al 2011).…”

“…Indeed, Ni, Co and Cd concentrations were not representative, and those of Pb, Cr and Li were 46.8, 17.8 and 9.0 mg/kg, respectively (Table 3). These metals are generally present in the composition of drilling sludge (Agwa et al 2013;Reyes-Avila et al 2013). Ion and metal richness can be native to the solid matrix mineral dissolution, rain water or produced water.…”