CONTAMINANT CONTAINMENT/PARTIAL REMOVAL PROCESSES

ERDC TN-DOER-T2

December 2000

Glass Aggregate. The Plasma Vitrification Technology is marketed by Global Plasma Systems

Corporation, Washington, DC, in partnership with Westinghouse Plasma Corporation. Plasma

vitrification is a high-temperature thermal process for converting waste to energy and

decontaminating wastes including dredged sediments, wastewater sludge, and biosolids. Using this

technology, dredged sediments can be transformed into molten glass and cooled to form glass

aggregate. The aggregate can be used as a raw material in the manufacture of architectural tile, glass

fiber, sandblasting grit, roadbed aggregate, and roofing granules. During the process, organic

contaminants are destroyed by combustion with destruction efficiencies greater than 99 percent

achieved. Heavy metals, along with mineral phases, are fused into glass, thus limiting their mobility

and meeting TCLP regulatory criteria.

In operation, the dredged sediment is screened and partially dewatered using conventional

techniques. Desalination of the sediment is conducted using an unidentified process. The sediment

is then injected in front of a plasma torch with temperatures in excess of 5,000 C. Fluxes are added

to modify the properties of the final product. The molten material is collected in an associated

chamber and passed through a quench chamber from which the vitrified product is collected. The

glass aggregate is shipped offsite to conventional manufacturing operations where the final products

are produced.

Lightweight Aggregate. The HarborRock Technology is marketed by HarborRock Holdings,

Glen Mills, PA. HarborRock is a thermal process for decontaminating dredged sediments and

producing a marketable product. Using this process, dredged sediment can be transformed into

lightweight aggregate for use in building material applications. During the process, organic

contaminants are thermally destroyed with destruction efficiencies greater than 99 percent. Heavy

metals are immobilized in the aggregate, thus limiting their mobility and meeting TCLP regulatory

criteria.

In operation, the dredged sediment is screened to remove large stones and debris, and then

dewatered using mechanical and thermal processes. The dewatered sediment is then processed in a

combined grinding and thermal drying process to achieve a uniform consistency. After cooling, the

material is mixed with water and extruded into pellets approximately 13 mm (0.5 in.) in diameter by

25 mm (1 in.) long. The pellets are then fed into a kiln for firing at a temperature in excess of 982 C

(1,800 F) where they expand to about 1.3 times their original size. The aggregate is then cooled and

stockpiled. Off-gas from the kiln is cooled, with the heat recovered, recycled, and used elsewhere in the

process, and passed through a final cleanup process prior to discharge. Residue from screening is

landfilled.

CONTAMINANT CONTAINMENT/PARTIAL REMOVAL PROCESSES

Flowable Fill. The Flowable Fill technology presented is marketed by Pohlman Materials

Recovery, Cary, IL. This technology is a nonthermal, mixing process using chemical additives to

transform dredged sediments into a flowable construction fill 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 of two to three orders of

magnitude is not unusual depending on the contaminant species.