In-pile thermal desorption of PAHs, PCBs and dioxins/furans in soil and sediment

Current overall treatment costs for soil and sediment heavily contaminated with semi-volatile organic compounds (SVOCs) such as polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs) and polychlorinated dibenzodioxins and furans (PCDD/Fs) can be as high as $550-770 per metric tonne. This paper focuses on an innovative thermal treatment method that is likely to be highly effective at full-scale costs of less than one-third ($110-330 per metric tonne depending on total volume). TerraTherm's in-pile thermal desorption (IPTD) technology is an ex-situ version of in situ thermal desorption (ISTD), by which TerraTherm utilizes simultaneous application of thermal conduction heating and vacuum to treat contaminated soil without excavation. With IPTD, the contaminated solids are placed in covered piles, interlayered with heater pipes and vapor extraction screens. The piles are then heated and treated using electrical heaters, which bring the temperature up to the target, typically around 330 degree C for SVOCs, depending on the nature of the contaminants. The applied heat volatilizes both water and organic contaminants within the soil/sediment, enabling them to be carried in the air stream toward vacuum extraction wells for destruction within the soil/sediment and transfer of the remaining vapor to an air quality control (AQC) unit. Based on demonstrated ISTD results of eight field-scale SVOC projects, very low or even non-detect concentrations are a feasible goal if required.