William L. Troxler and Thomas W. Brankley

Abstract

The Landfill Directive in the United Kingdom will severely restrict the disposal of untreated wastes from manufactured gas plant (MGP) sites in landfills after July 15, 2006. Clean-up levels for benzene, toluene and some polynuclear aromatic hydrocarbons (PAHs) may be in the low mg/kg range or less. Thermal desorption has demonstrated the capability to achieve extremely low treatment standards for organic contaminants in soil to allow for site redevelopment. Conservative risk-based screening levels from the US EPA are summarized and compared to values that are typically used by the Environment Agency (EA) in the UK. This paper also describes different types of thermal desorption systems that have been used to treat MGP wastes. It also presents a summary of the various factors that affect the capability of thermal desorption systems to achieve different levels of clean-up standards, including: (1) chemical and physical characteristics of the waste material; (2) geotechnical properties of the soils being treated; (3) design characteristics of thermal desorption systems; and (4) system process operating parameters. To demonstrate achievable treatment levels, soil treatment results from six full-scale thermal desorption projects are summarized. Finally, cost implications of key factors in providing thermal treatment services are summarized.

Key words: clean-up standards, manufactured gas plant, PAHs, redevelopment, thermal desorption