Degradation Rates for Petroleum Hydrocarbons Undergoing Bioventing at the Meso-Scale

Abstract

Bioventing can be effective for the remediation of soil contaminated with petroleum hydrocarbons. However, implementing laboratory results in field scenarios is difficult due to the lack of scale-up factors. Accordingly, laboratory bioventing experiments were undertaken at the meso-scale and then compared with previously completed micro-scale tests to evaluate the important scale-up factor. The developed meso-scale system holds 4 kg of soil, with bioventing conditions controlled from a nutrient, airflow, and water content perspective. Three soils were tested, and categorized as loamy sand, silt loam, and a mixture. Results over a 30-day period showed a two-stage degradation pattern that encompassed first-order degradation rates as compared with the single-stage first-order degradation rate determined in the micro-scale study. For the first stage (0-8 days), the degradation rate for loamy soil was 0.598 day −1 , with the silty soil at 0.460 day −1 , and mixed soil at 0.477 day −1 . After 8 days, the degradation rate constant for the loamy soil dropped to 0.123 day −1 , with the silty soil dropping to 0.075 day −1 , and the degradation rate for the mixed soil dropping to 0.093 day −1 . Comparison of the measured degradation rate values with the results from the micro-scale experiments gave scale-up factors varying from 1.9 to 2.7 for the types of soil considered in the current study. These differences in degradation rates between the two scales show the importance of scale-up factors when transferring feasibility study results to the field.

Large-scale bioventing degradation rates of petroleum hydrocarbons and determination of scale-up factors

“…For the analysis of synthetic gasoline samples a J&W scientific DB5 column was used. This column had previously used by Khan and Zytner, (2013) and Eyvazi and Zytner, (2010). The column was 30 m long with inner diameter of 0.32 mm and a film thickness of 1 μm.…”

“…For this research project two different types of soil were used. Soil from the Delhi Research Station, Delhi, Canada and the Elora Research Station, Elora, Canada were selected as they had been previously used in the bioventing soil vapour studies by Eyvazi and Zytner (2009) and Khan and Zytner (2013). Using the same soils allowed for a more accurate development of scale-up factors for bioventing SVE using the larger 80 kg reactors.…”

“…Drying the soil allows the microorganism populations to go dormant until reactivated when water was added to the soil prior to starting the experiments based on the protocols established by (Eyvazi and Zytner, 2009;Khan and Zytner, 2013). In addition to drying the soil, the soil was sifted to remove any large rocks or large pieces of organic matter that were unintentionally collected from the field.…”

“…The resulting scaleup factor was 1.8 ±0.5. In addition, a further refinement of the correlation developed by Eyvazi and Zytner (2009) came through the completion of Khan and Zytner's (2013) work on the 4 kg reactor bioventing soil remediation project.…”

“…This correlation was developed based on laboratory research and applied to the seven classes of soil that Eyvazi and Zytner (2009) studied, with each reactor holding 200 g of soil. Khan and Zytner (2013) used the correlation developed by Eyvazi and Zytner (2009) and conducted meso-scale experiments using 4 kg reactors which allowed for the development of a scale-up factor between the two experiments. The resulting scaleup factor was 1.8 ±0.5.…”