RADIAN INTERNATIONAL LLC

(formerly DOW ENVIRONMENTAL, INC.)
(Integrated Vapor Extraction and Steam Vacuum Stripping)

TECHNOLOGY DESCRIPTION:

The integrated AquaDetox/soil gas vapor extraction/reinjection (SVE) system simultaneously treats groundwater and soil contaminated with volatile organic compounds (VOC). The integrated system consists of (1) an AquaDetox moderate vacuum stripping tower that uses low-pressure steam to treat contaminated groundwater, and (2) an SVE process to treat contaminated soil. The two processes form a closed-loop system that simultaneously remediates contaminated groundwater and soil in situ with virtually no air emissions.

AquaDetox is a high-efficiency, countercurrent stripping technology. A single-stage unit can remove up to 99.99 percent of VOCs in water. The SVE system uses a vacuum to treat VOC-contaminated soil, inducing a flow of air through the soil and removing vapor-phase VOCs with the extracted soil gas. Carbon beds remove the VOCs from the soil gas, which is then reinjected into the ground. The AquaDetox and SVE systems share a granulated activated carbon (GAC) unit that decontaminates the combined vapors from both systems (see photograph below). By-products of the system are a free-phase recyclable product and treated water. In addition, mineral regenerable carbon will require disposal after about 3 years.

A key element of the closed-loop system is the vent header unit. This unit collects noncondensable gases from the AquaDetox system for treatment in the GAC units. Conversely, the AquaDetox system condenses and treats the steam used to regenerate the GAC units.

WASTE APPLICABILITY:

This technology removes VOCs, including chlorinated hydrocarbons, in groundwater and soil. Sites with contaminated groundwater and soils containing trichloroethene (TCE), tetrachloroethene (PCE), and other VOCs are suitable for this on-site treatment process.

STATUS:

This technology was accepted into the SITE Demonstration Program in 1990. In September 1990, a SITE demonstration was conducted as part of an ongoing remediation at the San Fernando Valley Groundwater Basin Superfund site in Burbank, California. The Applications Analysis Report (EPA/540/A5-91/002) and Demonstration Bulletin (EPA/540/M5-91/002) are available from EPA.

The AquaDetox/SVE system had been used for over 3 years at the time of the SITE evaluation to treat groundwater and soil gas at the Lockheed Aeronautical Systems Company in Burbank, California. Contaminated groundwater was treated at a rate of up to 1,200 gallons per minute (gpm), while soil gas was removed and treated at a rate of 300 cubic feet per minute. The system occupied about 4,000 square feet. It was operational 95 percent of the time, with 5 percent downtime for scheduled and nonscheduled repairs.

DEMONSTRATION RESULTS:

During the SITE demonstration, the AquaDetox/SVE system achieved the following results:

• The technology treated groundwater and soil gas contaminated with VOCs.
• Efficiencies ranged from 99.92 to 99.99 percent for removal of VOCs from contaminated groundwater. VOC removal efficiencies for soil gas ranged from 98.0 to 99.9 percent when the GAC beds were regenerated according to the specified frequency (8-hour shifts).VOC removal efficiencies dropped to as low as 93.4 percent when the GAC beds were regenerated less frequently.
• The technology produced effluent groundwater that complied with regulatory discharge requirements for TCE and PCE (5 micrograms per liter for each compound).
• The GAC beds removed VOCs from contaminated soil gas even after 24 hours of continuous operation without steam regeneration.
• The system's steam consumption dropped with decreasing tower pressures. During the demonstration, the system was more efficient at lower operating tower pressures.
• The 500-, 1,000-, and 3,000-gpm systems are estimated to cost about $3.2, $4.3, and $5.8 million, respectively. The total annual operation and maintenance costs are about $410,000, $630,000 and $1,500,000 for the 500-, 1,000-, and 3,000-gpm systems, respectively.

Integrated Aqua/Detox SVE System

FOR FURTHER INFORMATION:

EPA PROJECT MANAGER:
Gordon Evans
U.S. EPA
National Risk Management Research Laboratory
26 West Martin Luther King Drive
Cincinnati, OH 45268
513-569-7684
Fax: 513-569-7787

TECHNOLOGY DEVELOPER CONTACT:
David Bluestein
Radian International LLC
1990 North California Boulevard, Suite 500
Walnut Creek, CA 94596
510-988-1125
Fax: 510-932-7130