Solidification/Stabilization

ERDC TN-DOER-T2

December 2000

Solidification/Stabilization.

The solidification/stabilization technology presented was

developed and used by the OENJ Cherokee Corporation, Bayonne, NJ, for cover at an old city

landfill in Elizabeth, NJ, using dredged sediment. This technology is a nonthermal, mixing process

using chemical additives to transform dredged sediments into a structural-cover product. During the

process, contaminants are not destroyed, but their mobility is reduced due to chemical stabilization

and incorporation in the physical matrix of the product. Reduction in mobility is dependent on the

contaminant and the type and amount of chemical additives used.

In operation, the dredged sediment is screened to remove large debris and then transferred to a pug

mill. Solidification additives (portland cement was used for this particular project) are added and

mixed into the sediment. The resulting mixture is transported to the work site where it is allowed to

dry and gain strength as a result of hydration of the additives. The material is then spread and

compacted to provide a smooth, hard surface.

SUMMARY: The focus of the Specialty Conference was on technologies that are generally

applicable to contaminated sediments and that have the potential to process large amounts of

sediments, that is, sediment quantities in excess of 764,555 cu m (1,000,000 cu yd). Essentially all

dredged material decontamination and treatment technologies that are capable of processing in

excess of 764,555 cu m (1,000,000 cu yd) of dredged material fall into one of two basic categories,

destruction technologies and technologies that separate/extract or stabilize contaminants.

Most destruction technologies are essentially thermal, since nonthermal-based destruction

technologies are generally not available for some contaminants. Sediment decontamination

technologies that are capable of processing large volumes of dredged material are designed to avoid

disposal costs of product materials. They are designed to produce a salable product material.

EVALUATIONS: The important information and features of the eight technologies presented

during the workshop are summarized in Table 1. Some of the information is incomplete because it

was not presented by the TDFs. In comparing technologies, it should be noted that the technologies

vary in their maturity and scale of demonstration. Capital and operation and maintenance costs are

highly dependent on specific site conditions, dredged sediment characteristics, and the product

produced.

Among the separation and stabilization technologies that have been proposed for contaminated

sediments are sediment washing and processes that seek to produce fill material in which the

contaminants are effectively contained. Soil washing technologies serve to reduce contaminant

levels by partial removal of fines and organic material containing contaminants. The net result is

contaminant reductions, by factors of 2-10, of the more soluble constitutents in the sediments.

Reductions in contaminant levels of less soluble components, such as polychlorinated biphenyls

(PCBs) or high-molecular-weight polycylic aromatic hydrocarbons (PAHs), are likely to be less

than a factor of two. In many situations, this may be insufficient to allow significantly expanded uses

of the treated material over the untreated dredged material. The goal of most soil washing

technologies is production of a soil for beneficial use.

Stabilization technologies introduce additives to the dredged material to produce flowable or solid

fill material. The contaminant levels are normally unchanged except for dilution due to the additives