Abstract
This study focuses on biological removals of petroleum hydrocarbons from an oilfield-produced water generated in Naft Shahr resource by natural attenuation, biostimulation, and bioaugmentation processes. The results of the natural attenuation experiments indicated low population of existing environmental bacterial cells which could not remove total petroleum hydrocarbon (TPH) and initial chemical oxygen demand (COD) at 30 °C and 180 rpm. However, biostimulation by adding nitrogen, sulfur, and phosphorus sources resulted to 19.9% removal of TPH, mainly corresponding to the low chain n-alkanes, and 15.9% removal of COD in 6 days. Degradation of hydrocarbons with longer chain than C20 was limited mainly due to the low solubility of the hydrophobic compounds in the process. Bioaugmentation with the locally-isolated biosurfactant-producing Candida catenulata provided a companionship of the yeast with existing bacterial environmental cells and resulted in increase of the biodegradability of TPH by 16.1% even in the absence of the additional nutrient. A uniform degradation for all hydrocarbon fractions was only observed in the combination of biostimulation with bioaugmentation processes. The study on initial pH yielded the highest removals of 93.39% of TPH and 66.85% of COD in the combined process when initial pH was set at 5.0.
Published Version
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