On-Site Bioremediation Systems Reduce Crude Oil Contamination

Abstract

Summary. Oilfield properties frequently have areas where soils contain concentrationsof crude oil. These soils can be either"hazardous wastes" or"designated wastes" under regulatory guidelines. As a result, propertyowners and financial institutions face potential liabilities when oilfieldproperties are transferred to new operators, abandoned, or converted to otheruses.Modern, well-designed soil bioremediation systems are cost-effective ways totreat soils that contain concentrations of crude oil, and these systems caneliminate an owner's subsequent liabilities. A modern on- sitebioremediation system requires significantly less surface area, results inlower operating costs, and provides more effective, expeditious results thantraditional land-farming practices. It also eliminates potential long-termliabilities and is typically more cost-effective than excavation and off-sitedisposal of oilfield soils. Case studies indicate that on-site bioremediationsystems have reduced crude oil contamination in soil to levels acceptable toregulatory agencies in less than 20 weeks (in some cases, less than 10 weeks). Total costs for on-site bioremediation range from $35 to $120/yd3oftreated soil, including excavation, depending on specific siterequirements.Introduction. During normal operation of oilfield properties, crude oil or other materialsfrequently leak or spill onto land surfaces. These degraded soils are commonlyassociated with oil wells, sumps and pits, tank batteries, gathering lines, andpump stations. Crude oil and drilling muds may also be found in these areasand, like the contaminated soil, they may be considered either hazardous wastesor designated wastes under current regulatory guidelines. The regulationspertaining to crude oil vary across the U.S. In California, for example, crudeoil is considered a designated waste and its off-site disposal is subject toregulations. If certain constituents (e.g., benzene) are present insufficiently high concentrations, the soil degraded by crude oil may beconsidered a hazardous wasteand subject to additional regulations. Crude oilsludge in an old sump typically contains oilfield treatment chemicals;therefore, the sludge is considered a hazardous waste.