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Posted 4/20/1993

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By Richard Broussard
Release no. 93-3


Hanover--Results of water quality tests following the startup of a temporary groundwater treatment plant at the Cold Regions Research and Engineering Laboratory show that the facility is no longer discharging trichloroethylene-laden (TCE) water into the Connecticut River.

Construction of the $300,000 treatment plant resulted from the discovery in December of 1990 of TCE in the industrial cooling water at CRREL After a 2-yearlong investigation of the problem the new plant has come on line and is successfully removing all detectable traces of the chemical from CRREL's water.

The temporary facility will continue in operation until a permanent plant is completed in January 1994. Construction of the water treatment system is a remedial action under the Department of Defense's Installation Restoration Program.

The recently completed facility is termed a "packed tower" groundwater treatment plant. It is designed to strip volatile organic gases, such as TCE, out of liquid water.

How the system works: First, TCE-contaminated water is introduced at the top of the tower, which is packed with plastic media (small, irregular-surfaced balls about the size of ping pong balls) that maximize the surface area of water. Then air is blown up from the bottom. This sets up a water/air counter-current flow which optimizes conditions for volitization or evaporation. TCE is forced out of the water and into the air. The water is now clean and can be used in CRREL's refrigeration systems and then discharged into the river. The air passes from the packed tower to a granular-activated carbon (GAC) unit. The GAC has many absorption surfaces where the TCE is absorbed out of the air by the carbon.
The air is finally clean and released. The GAC can be used for approximately a year until fully saturated; the carbon is then either regenerated by heating it until the TCE is destroyed, or replaced.
The permanent plant, which is now under construction by Barletta Engineering Corporation of Hampton, NH, will cost approximately $1.6 million ($240,000 has already been invested in equipment for the temporary plant). It will have an additional process called a "green sand filter" to remove iron and manganese that are common in area groundwater.

Once completed, the permanent facility will consist of two packed towers and two granular-activated carbon units in order that one unit can be shut down for maintenance while the other continues to filter the well water.

Next to the temporary treatment plant a building has been erected to house two other experimental methods for removing TCE from contaminated groundwater. The first is a shallow tray aerator unit being tested in cooperation with Northeast Environmental Products, Inc. This is a pilot study to test the effectiveness of the unit for TCE removal under low temperature conditions.

The second study, which is now in the planning stage, will evaluate the use of a fixed film bioreactor containing aerobic TCE-degrading bacteria. Exhaust gasses from the shallow tray aerator will be biologically degraded to nonhazardous end products in the reactors, eliminating the need for GAC treatment and further disposal of hazardous substances. This study is a cooperative effort among CRREL, EPA, University of West Florida, and SBP Technologies, Inc.

As part of the continuing groundwater remediation program at CRREL, a Phase II Remedial Investigation and Baseline Risk Assessment study will begin shortly. The overall purpose of the investigation is to evaluate the vertical and lateral extent of contaminant migration and rate of contaminant migration in the ground water in deep overburden and bedrock wells at specific locations of concern and to further define the local geology.

The baseline risk assessment is designed to evaluate the potential threat to human health and the environment in the absence of any other remedial action than the recently started water treatment system.