PNNL-13501 - Pacific Northwest National Laboratory

Study Control Number: PN00054/1461
In Situ Destruction of Contaminants Using Ozone
Tyler Gilmore, Kirk Cantrell
This project addresses remediation of organic contamination in the soil. The project was specifically focused on the
treatment of TNT explosive, which has the potential for contaminating aquifers.
Project Description
Ozone was used to degrade the organic contaminant, TNT
(trinitrotoluene), on unsaturated soil. Several soil
columns were run where the degradation of TNT over
time was measured. The results indicated that 50% of the
TNT was degraded in 2 hours with 80% degraded in 16
hours. A nitrate balance indicated the TNT was
essentially completely oxidized. The major degradation
products of TNT oxidation are carbon dioxide and nitrate.
This study provided proof-of-principle testing in support
of a new environmental remediation technology for
treating contaminated soil in the vadose zone.
Introduction
This research provides the technical basis for in situ
destruction (or treatment) of contaminants in the vadose
zone by oxidation using ozone. Ozone has been shown to
be very effective at oxidizing a range of contaminants
from chlorinated solvents (perchloroethylene,
trichloroethylene) to energetic compounds (TNT) in
groundwater. This research will extend the application of
ozone to unsaturated soil in the vadose zone. We focused
on the contaminant TNT because of the heightened
concerns of explosive contamination in regional aquifers.
Approach
A series of soil column experiments were conducted in
which ozone at a concentration of approximately 10%
oxygen was passed through soil contaminated with TNT
(Figures 1 and 2). Two types of soils were used in the
columns: Pasco sands from Washington State, and
alluvium from the White Sands Missile Range, New
Mexico. The silty, sandy alluvium from White Sands was
spiked with approximately 50 µg/Kg TNT and the Pasco
sands were spiked with approximately 10 µg/Kg. The
soils were spiked by soaking them in water solutions of
TNT. The water was mixed into the soil and then allowed
to air dry to a moisture content of approximately 5 to
10 % by weight, or the typical moisture content
228 FY 2000 Laboratory Directed Research and Development Annual Report
Figure 1. Experimental setup with ozonator
Figure 2. Soil column