The La Puente Valley County Water District

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Since it was first settled in 1841, the San Gabriel Valley has hosted a variety of industries, ranging from walnut packing to rocket fuel manufacturing. Along with other contaminants, industrial development has left a significant portion of the Valley’s groundwater contaminated with:

- N-nitrosodimethylamine (NDMA) and
- 1,4-Dioxane.

NDMA entered the groundwater in the San Gabriel Valley as a by-product in the production of liquid rocket fuel. 1,4-Dioxane is primarily used as a stabilizer in chlorinated solvents such as trichloroethylene (TCE) or 1,1,1-trichloroethane. Both NDMA and 1,4-dioxane readily leach into groundwater, are highly mobile, and are resistant to biodegradation. Both resist treatment with traditional water treatment methods such as carbon adsorption or air stripping. However, Trojan’s optimized treatment solution, employing direct UV-photolysis and UV-oxidation, effectively destroys both chemicals. The La Puente Valley County Water District (LPVCWD), a water company in the San Gabriel Valley, is using Trojan’s low-energy UV solution to remove these contaminants from the drinking water it provides to its customers.

The Trojan Solution

Trojan was asked in the spring of 2001 to provide a more cost-effective UV treatment system for NDMA and 1,4-dioxane at the LPVCWD. Due to the substantial O&M cost savings, the Trojan solution replaced a competitor's existing UV system installed in 1998. After testing the site’s water and optimizing the UV system based on the site’s water quality parameters, permit testing was performed on the full-scale system. Results showed excellent NDMA and 1,4-dioxane destruction while reducing electricity consumption by approximately 80per cent when compared to the UV system it replaced.

The facility, including the Trojan UV system, has been approved for drinking water delivery by the California Department of Health Services, and has been in operation since May, 2002. The LPVCWD is one of five Trojan projects in the San Gabriel Valley that will remove NDMA and 1,4-dioxane from over 50 million gallons of drinking water per day.

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