According to the Environmental Protection Agency (EPA), solidification “involves the processes that encapsulate contaminated material to form a solid material and restricts contaminant migration by decreasing the surface area exposed to leaching and/or by coating the contaminated material with low hydraulic conductivity [movement of water] materials.” The EPA describes stabilization as “the process where chemical reactions occur between the reagents and contaminated material to reduce the leachability [ability to be removed or transported via contact with water] of contaminated material by creating a stable insoluble form.”
Both technologies can treat inorganic contaminants such as metals, including: arsenic, cadmium, chromium, copper, lead, mercury, nickel, selenium, uranium and zinc; and organic contaminants, including pesticides and hydrocarbons.
Before solidification/stabilization technologies are used to treat the contaminated solid waste, thorough treatability tests and studies are conducted so the right reagents are mixed and the proper equipment mobilized. The reagents generally either encapsulate the contamination or adsorb it, depending on the type of contamination. After solidification/stabilization technologies are applied, the material is tested. The entire process follows performance-related parameters and criteria that are established by state regulators.
Some of the most important indicators of successful solidification/stabilization applications involve the compressive strength of the resulting solid material and how well the process limits both the hydraulic conductivity and leachability of contaminants at the site. These criteria are achieved by the creation of monoliths.