Bioremediation of Aged Contaminated Soils and Drill Cuttings in a Large-Scale Field Study Under Tropical Conditions

Abstract Hydrocarbons (HC) introduction into the soil environment can accidentally occur. About 500 m3 of a 20-year old crude oil polluted soil were excavated then transported to a bioremediation plant. Initial content of hydrocarbons was approximately 40 g HC kg−1 dry soil. Fresh drill cuttings, containing 14 g HC kg−1 dry soil, were collected from a rig and transferred to the treatment area. The polluted soil was mixed with drill cuttings in different ratios. Soils and cuttings were treated by bioremediation in windrows periodically tilled. Composting in windrows constituted the first part of the research program (Indonesian Pilot of Oily Waste Composting, IPOC). Infrared spectrometry and gas chromatography determined hydrocarbon concentrations in the materials. Bacterial counts were regularly performed. Up to 70% of the initial content in HC were removed through biological processes in 365 days. Gas chromatography analyses demonstrated the rapid biodegradation of linear and branched alkanes. Polyaromatic hydrocarbons were undetectable after treatment. Residual HC were saturated cyclic compounds poorly biodegraded and strongly trapped on the organo-mineral matter. Low levels of HC were detected in the leachates on day 365. The concentrations were below national standards. The decontaminated materials were recycled on-site as bulk material and successfully vegetated. The field experiment demonstrated the potential to use on site bioremediation for soil pollution and drill cuttings treatment.