A Four-Step Biotreatability Protocol for Crude Oil Impacted Soil

Abstract

Bioremediation is often the preferred method for remediating crude oil impacted soil at exploration and production facilities because it is proven, cost-effective, robust, and performed on location. However, not all crude oil impacted soils are amenable. A four-step protocol, including predictive equations, has been developed to assess the feasibility of ex-situ bioremediation for crude oil impacted soil, enabling site managers to potentially forego expensive and time consuming biotreatability trials. First, representative samples are tested for conditions which could preclude bioremediation or necessitate pre-treatment, special management, or upfront lab treatability studies. The source crude and soil-based residual hydrocarbons are geochemically characterized to determine the inherent biodegradability of the crude and amount of hydrocarbon that has already been passively biodegraded or removed by an abiotic mechanism such as volatilization. A database of first-order rate constants characterizes the biotreatment kinetics. Compositional and rate data are used to estimate the duration of treatment and endpoint achievable by ex- situ bioremediation in steps 2 and 3. The predictive endpoint equation was derived from first principles, empirically corrected using field-scale data, and validated at full-scale for source condensates and crude oils ranging from 14° to 45° API. The degree of validation suggests the predictive equations are suitable for making decisions on bioremediation potential, thereby eliminating the need for lab and pilot treatability studies in many cases. If the duration and extent of removal predicted would fulfill the project's objectives, the final configuration (land treatment or composting) is selected in step 4 considering schedule and spatial constraints and the properties the bioremediated soil needs to possess to support the designated end use. As with any predictive methodology the practitioner must exercise caution to identify any confounding factors which could constrain the rate or degree of removal. This paper will present the biotreatability protocol, predictive equations for inferring bioremediation feasibility from compositional information, and other lessons learned from crude oil bioremediation projects performed over the last 20 years.

Use of a novel biomarker, botryococcane, to monitor biodegradation of two lacustrine‐sourced crude oils

“…Bioremediation of petroleum‐impacted soils at exploration and production (E&P) sites by indigenous microorganisms has been used as a soil remediation technology since the early 1970s (Salanitro et al, 1997). The ability to achieve regulatory‐defined remediation goals is dictated by the inherent biodegradability of the crude oil itself as well as the design and operational efficiency of the soil bioremediation system (Hoffmann, Berbier, Smith, & McMillen, 2010). The biodegradability of crude oil depends substantially on the proportions of more labile aliphatic and aromatic hydrocarbons relative to the more refractory polars and asphaltenes (Brassell, Eglington, & Mo, 1986; Infante, Morales, Ehrmann, Hernández‐Valencia, & Leon, 2010; McMillen, Magaw, & Carovillano, 2001; National Research Council, 2003; Tissot & Welte, 1984).…”