In the early 1990’s, the volatile organic compounds (VOCs) tetrachloroethylene (PCE), and trichloroethylene (TCE) were discovered in the vicinity of several city water supply wells near the city of Stockton, California.
An aggressive hydraulic containment/water reinjection system was installed to contain the plume and protect the quality of the drinking water. For several years, a treatment system consisting of granular activated carbon and air stripping was used to remove VOCs from the reinjected water.
The 1,4-dioxane Discovery
The contaminant 1,4-dioxane was also discovered in the plume. 1,4-Dioxane is commonly used as a stabilizer in chlorinated solvents, and therefore is often present in VOC plumes. In particular, 1,4-dioxane contamination is commonly found at sites contaminated with 1,1,1-trichloroethane (TCA), a solvent that contains up to 15% 1,4-dioxane.
A semi-volatile contaminant with low volatility and low affinity for carbon materials, 1,4-dioxane resists removal from water by carbon or air stripping. The consulting engineer for the project, Dudek and Associates Inc., contacted Trojan Technologies for a treatment solution to remove this emerging contaminant.
Trojan worked closely with the engineers to provide an optimized low-energy ultraviolet light (UV) oxidation system to treat the 1,4-dioxane.
System Design Parameters
|Flow Rate||200 gallons per minute|
|Influent 1,4-Dioxane Concentration||110 parts per billion (ppb)|
|Effluent 1,4-Dioxane Concentration||<1.0 ppb|
|Oxidizer (for 1,4-Dioxane Treatment)||Hydrogen Peroxide|
The TrojanUV Solution
Trojan provided a pressurized, multi-lamp TrojanUVPhox™ reactor system to treat the 1,4-dioxane by UV-oxidation, a process that combines UV light and hydrogen peroxide.
To optimize the UV treatment system during the design phase, Trojan performed testing on groundwater collected at the site to determine its water quality parameters. The resulting TrojanUVPhox system was installed in the summer of 2001 and is still in operation today.
General Contaminant Overview
- Chlorinated solvents manufacturing
- Printed circuit board manufacturing
- Plastic, lacquer, varnish & paint manufacturing
- Dye, resin, wax & grease manufacturing
- Textile processing
- Pesticide production
- Tissue processing & biological labs
- Probable human carcinogen
California Department of Health Services (DHS)
- Action level – 3.0 parts per trillion (ppt)
- 1,4-Dioxane is most commonly used in industry as a stabilizer in chlorinated solvents such as TCE. Reported fractions of 1,4-dioxane in the host solvent range from 1% to 15%, depending on the manufacturer. For this reason, 1,4-dioxane is often found intermingled in groundwater solvent plumes. Due to its chemical properties, 1,4-dioxane migrates farther and persists longer than other contaminants in a groundwater plume.
- (1,4-Dioxane) 110 ppb
After TrojanUV Low-Energy Treatment
- (1,4-Dioxane) <1.0 ppb