Thermal Desorption Treatment of Dioxin-Contaminated Soil at the Former Allied Feeds Site, Sydney, Australia

The former Allied Feeds site is located on the Rhodes Peninsula adjacent to Homebush Bay, in Sydney, Australia. The adjacent Lednez site was historically used for manufacturing a range of chemicals, including tar, explosives, and chlorinated compounds. Through these activities, both sites and the Homebush Bay were contaminated with dioxins/furans, chlorobenzenes, chlorophenols, and organochlorine pesticides. Both properties have been remediated for open space, medium- and high-density residential use, and commercial development. The Lednez-site remediation activities also include dredging and treating contaminated sediments from Homebush Bay. Combined, these projects represent the largest dioxin remediation project that has been undertaken in the world using a thermal treatment technology. On the Allied Feeds site, about 175,000 tonnes of dioxin-contaminated soil has been treated using a directly heated thermal desorption plant. The project is significant because (1) it is the first large-scale thermal remediation project conducted in Australia, (2) the project has been implemented at a time when local environmental regulations were evolving, (3) the feed material contains high concentrations of dioxins/furans and potential dioxin/furan precursor compounds (e.g., chlorophenols and chlorobenzenes), (4) the feed material contains a high proportion of fine-grained spent lime with a high moisture content, (5) the project is being conducted adjacent to a major waterway in a highly developed urban area, and (6) the site is being redeveloped for residential and commercial use concurrently with remediation activities. The project has included a number of regulatory, technical, and logistical challenges, including the development of best practice regulatory standards, control of fugitive emissions, processing of a difficult and complex feed material, and compliance with stringent environmental requirements. This article discusses a number of project issues, the results of the regulatory compliance test program, and the production operations phase of the project.