ABSTRACT
Solidification refers to techniques that encapsulate hazardous waste into a solid material of high structural integrity. Encapsulation involves either fine waste particles (microencapsulation) or a large block or container of wastes (macroencapsulation) [1, p. 2]. 2 Stabilization refers to techniques that treat hazardous waste by converting it into a less soluble, mobile, or toxic form. Solidification/Stabilization (S/S) processes, as referred to in this chapter, utilize one or both of these techniques.
S/S technologies can immobilize many heavy metals, certain radionuclides, and selected organic compounds while decreasing waste surface area and permeability for many types of sludge, contaminated soils, and solid wastes. Common S/S agents include: Type 1 portland cement or cement kiln dust; lime, quicklime, or limestone; fly ash; various mixtures of these materials and various organic binders (e.g., asphalt). The mixing of the waste and the S/S agents can occur outside of the ground (ex situ) in continuous feed or batch operations, or in the ground (in situ) in a continuous feed operation. The final product can be a continuous solid mass of any size, or of a granular consistency resembling soil. During in situ operations, S/S agents are injected into and mixed with the waste and soil up to depths of 30 to 100 feet using augers.
Treatability studies are the only means of documenting the applicability and performance of a particular S/S system. Determination of the best treatment alternative will be based on multiple site-specific factors and the cost and efficacy of the treatment technology. The EPA contact identified at the end of this chapter can assist in the location of other contacts and sources of information necessary for such treatability studies.
It may be difficult to evaluate the long-term (>5 year) performance of the technology. Therefore, long-term monitoring may be needed to ensure that the technology continues to function within its design criteria.
This chapter provides information on technology applicability, the limitations of the technology, the technology description, the types of residuals produced, site requirements, the process performance data, the status of the technology, and sources for further information.
