Over 50 tonnes of heavy metal contaminated soil required treatment in order to meet disposal guidelines. The metals were a combination of copper, chromium and arsenic. Each had a very high leachable fraction, presenting a risk to the environment and to personnel undertaking the works.
The treatment approach was based on reducing the leachable fraction, as the metals themselves could not be removed from the soil matrix. The approach was based on a two-step process using reagent Heavy 33-90. The liquid component was mixed with the contaminated soil to create a low leachable form of the metal, and then binding it into a matrix that has a relatively neutral pH. This ensures that the amphoteric nature of the metals is managed, especially given the types of metals being treated.
Treatment occurred at the Southern Waste ResourceCo (SWR) treatment facility. Environmental aspects were managed within the facility such as dust and leachate generation. After treatment the results showed the process was a success and the material was disposed of to landfill.
The main disciplines undertaken included the following: