Pyrolytic treatment offers the potential for rapid remediation of contaminated soils. However, soil fertility restoration can be highly variable, underscoring the need to understand how treatment conditions affect soil detoxification and ability to support plant growth. We report here the first pilot-scale study of pyrolytic remediation of crude-oil contaminated soil using a continuously-fed rotary kiln reactor. Treatment at 420oC with only 15-min residence time resulted in high removal efficiencies for both total petroleum hydrocarbons (TPH) (99.9%) and polycyclic aromatic hydrocarbons (PAHs) (94.5%), and restored fertility to clean soil levels (i.e., <i>Lactuca sativa</i> biomass dry weight yield after 21 days increased from 3.0±0.3 mg for contaminated soil to 8.8±1.1 mg for treated soil, which is similar to 9.0±0.7 mg for uncontaminated soil). Viability assays with a human bronchial epithelial cell line showed that pyrolytic treatment effectively achieved detoxification of contaminated soil extracts. As expected, TPH and PAH removal efficiencies increased with increasing treatment intensity (i.e., higher temperatures and longer residence times). However, higher treatment intensities decreased soil fertility, suggesting there is an optimum system-specific intensity for fertility restoration. Overall, this study highlights tradeoffs between pyrolytic treatment intensity, hydrocarbon removal efficiency and fertility restoration while informing the design, optimization, and operation of large-scale pyrolytic systems to efficiently remediate crude-oil contaminated soils.

Pilot-scale pyrolytic remediation of crude-oil contaminated soil in a continuously-fed reactor: treatment intensity tradeoffs

2019 Spring National Meeting

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