Abstract
Solidification/stabilization (S/S) treatment is used to treat hazardous wastes for
disposal and in the remediation/site restoration of contaminated land. S/S is also an
increasingly popular technology for brownfields (industrial property) redevelopment,
since treated wastes can often be left on-site and to improve the soil for subsequent
construction. This article discusses the applicability of the technology to various
wastes, basic cement chemistry relating to S/S, tests used to design treatability studies
and to verify treatment, basics on implementation of the technology in the field, and
two examples of S/S: one allowing the redevelopment of port-side property, another
allowing the reuse of dredged material.
Introduction
Solidification/stabilization (S/S) is a widely used treatment for the
management/disposal of a broad range of contaminated media and wastes;
particularly those contaminated with substances classified as hazardous in the United
States. The treatment involves mixing a binding reagent into the contaminated media
or waste. The treatment protects human health and the environment by immobilizing
contaminants within the treated material. Immobilization within the treated material
prevents migration of the contaminants to human, animal and plant receptors. S/S
treatment has been used to treat radioactive wastes since the 1950s and hazardous
waste since the 1970’s. [Conner 1990] S/S continues as a cornerstone treatment
technology for the management of radioactive waste, hazardous waste, and site
remediation and Brownfield redevelopment.
The U.S. Environmental Protection Agency (EPA) considers S/S an established
treatment technology. S/S is a key treatment technology for the management of
industrial hazardous wastes. These wastes are regulated in the United States under the
Resource Conservation and Recovery Act (RCRA). RCRA hazardous wastes are
grouped into two classes: RCRA-listed and RCRA-characteristic. RCRA-listed
hazardous wastes are wastes produced by industry that are generally known by the
EPA to be hazardous. These wastes are “listed” in RCRA regulations and must be
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treated, stored, and disposed according to RCRA hazardous waste management
regulations. RCRA-listed wastes destined for land disposal are required to be treated
in order to reduce hazards posed by the wastes after land disposal. EPA has identified
S/S as Best Demonstrated Available Technology (BDAT) for 57 RCRA-listed
hazardous wastes.[USEPA June 1993] RCRA-characteristic wastes are less routinely
produced wastes that are found to be hazardous due to a characteristic of the waste.
For RCRA-characteristic wastes, S/S can often be used to eliminate the hazardous
characteristic. With the hazardous characteristic addressed the treated waste can be
disposed at a lower cost or re-used.
S/S treatment is used to treat contaminated media during remediation of contaminated
properties. The permitting requirements for hazardous waste management facilities
under RCRA include requirements for owners of these facilities to remediate
previously contaminated areas at the facility. This is known as RCRA Corrective
Action and S/S can be applied to address these contaminated areas. However, the
best-known and documented remediation program in the United States is conducted
under the Comprehensive Environmental Response, Compensation, and Liability Act
(CERCLA). The CERCLA program is used to remediate abandoned or uncontrolled
properties where hazardous substances have been released and pose an endangerment
to human health and the environment. The remediation program conducted under
CERCLA is funded by a tax collected from petroleum and chemical manufacturers
and by potentially responsible parties that caused the contamination, commonly
called the “Superfund” program. S/S is the most frequently selected treatment
technology for controlling the sources of environmental contamination at Superfund
program remediation sites. Twenty-five percent of selected remedies for these sites
include the use of S/S (see Figure 1).[