ROY F. WESTON, INC.

(Low Temperature Thermal Treatment System)

TECHNOLOGY DESCRIPTION:

The Roy F. Weston, Inc. (Weston), low temperature thermal treatment (LT³®) system thermally desorbs organic compounds from contaminated soil without heating the soil to combustion temperatures. The transportable system (see photograph below) is assembled on three flat-bed trailers and requires an area of about 5,000 square feet, including ancillary and support equipment. The LT³® system consists of three segments: soil treatment, emissions control, and water treatment.

Low Temperature Thermal Treatment (LT³®) System

The LT³® thermal processor consists of two jacketed troughs, one above the other. Each trough houses four intermeshed, hollow screw conveyors. A front-end loader feeds soil or sludge onto a conveyor that discharges into a surge hopper above the thermal processor. Hot oil circulating through the troughs and screws heats the soil to 400 to 500 F, removing contaminants. A second stage indirect heater is available to achieve 1,000 F discharge temperatures. Soil is discharged from the thermal processor into a conditioner, where a water spray cools the soil and minimizes dust emissions.

A fan draws desorbed organics from the thermal processor through a fabric filter baghouse. Depending on contaminant characteristics, dust collected on the fabric filter may be retreated, combined with treated material, or drummed separately for off-site disposal. Exhaust gas from the fabric filter is drawn into an air-cooled condenser to remove most of the water vapor and organics. The gas is then passed through a second, refrigerated condenser and treated by carbon adsorption.

Condensate streams are typically treated in a three-phase, oil-water separator to remove light and heavy organic phases from the water phase. The water phase is then treated in a carbon adsorption system to remove residual organic contaminants. Treated condensate is often used for soil conditioning, and only the organic phases are disposed of off site.

WASTE APPLICABILITY:

This system treats soils and sludges contaminated with volatile and semivolatile organic compounds (VOC and SVOC). Bench-, pilot-, and full-scale LT³® systems have treated soil contaminated with the following wastes: coal tar, drill cuttings (oil-based mud), No. 2 diesel fuel, JP-4 jet fuel, leaded and unleaded gasoline, petroleum hydrocarbons, halogenated and nonhalogenated solvents, VOCs, SVOCs, polynuclear aromatic hydrocarbons, polychlorinated biphenyls, pesticides, herbicides, dioxins, and furans.

STATUS:

The LT³® system was accepted into the SITE Demonstration Program in September 1991. In November and December 1991, the LT³® system was demonstrated under the SITE Program as part of a proof-of-process test for full-scale remediation of the Anderson Development Company (ADC) Superfund site in Adrian, Michigan. The system was tested on lagoon sludge from the ADC site. This sludge was contaminated with VOCs and SVOCs, including 4,4-methylene bis(2-chloroaniline) (MBOCA).

The Demonstration Bulletin (EPA/540/MR-92/019) and Applications Analysis Report (EPA/540/AR-92/019) are available from EPA.

DEMONSTRATION RESULTS:

During the demonstration, the system throughput was approximately 2.1 tons per hour. Six replicate tests were conducted, each lasting approximately 6 hours. The SITE demonstration yielded the following results:

• The LT³® system removed VOCs to below method detection limits (less than 0.060 milligram per kilogram [mg/kg] for most compounds).
• The LT³® system achieved MBOCA removal efficiencies greater than 88 percent; MBOCA concentrations in the treated sludge ranged from 3.0 to 9.6 mg/kg.
• The LT³® system decreased the concentrations of all SVOCs in the sludge, with the exception of phenol, which increased possibly due to chlorobenzene.
• Dioxins and furans were formed in the system, but the 2,3,7,8-tetra-chlorodibenzo-p-dioxin isomer was not detected in treated sludges.
• Stack emissions of nonmethane total hydrocarbons increased from 6.7 to 11 parts per million by volume during the demonstration; the maximum emission rate was 0.2 pound per day (ppd). The maximum particulates emission rate was 0.02 ppd, and no chlorides were measured in stack gases.

The economic analysis of the LT³® system's performance compared the costs associated with treating soils containing 20, 45, and 75 percent moisture. The treatment costs per ton of material were estimated to be $37, $537, and $725, respectively.

FOR FURTHER INFORMATION:

EPA PROJECT MANAGER:
Paul dePercin
U.S. EPA
National Risk Management Research Laboratory
26 West Martin Luther King Avenue
Cincinnati, OH 45268
513-569-7797
Fax: 513-569-7105
E-Mail: dePercin.Paul@epamail.epa.gov

TECHNOLOGY DEVELOPER CONTACT:
Mike Cosmos
Roy F. Weston, Inc.
1 Weston Way
West Chester, PA 19380-1499
610-701-7423
Fax: 610-701-5035