Treatment of NDMA & 1,4-dioxane in San Gabriel Valley, California

Since it was first settled in 1841, California’s San Gabriel Valley, east of Los Angeles, has hosted a wide variety of industries. However, industrial development has left a significant portion of the Valley’s groundwater contaminated with various organic contaminants, including N-nitrosodimethylamine (NDMA) and 1,4-dioxane. Because much of the Valley’s water supply is obtained from this groundwater, treatment facilities are required.

Volatile organic compounds were first discovered at the Valley County Water District in 1979. The plume now extends for approximately nine miles and underlies the cities of Azusa, Baldwin Park, West Covina, Industry, and Irwindale. NDMA was first discovered in the plume at the La Puente Valley County Water District in 1997. Its discovery led to the re-evaluation of treatment plans for impacted facilities. The aquifer in the San Gabriel Valley, in which the plume is located, provides drinking water to over one million residents in Los Angeles County.

NDMA and 1,4-Dioxane and UV-oxidation

While many of the contaminants can be removed with conventional contaminant treatment technologies such as air stripping and carbon adsorption, NDMA and 1,4-dioxane require more advanced technology. NDMA, produced as a by-product of rocket fuel manufacturing, is considered highly carcinogenic and is most cost-effectively removed by UV light. 1,4-Dioxane, a stabilizer used in industrial solvents, requires treatment by UV-oxidation (the combination of UV light with hydrogen peroxide).

General Contaminant Overview

N-nitrosodimethylamine (NDMA)
Potential Sources:
• Drinking water disinfection with chlorine or chloramine
• Printed circuit board manufacturing
• Pesticide manufacturing
• Pharmaceutical manufacturing
• Fish & seafood processing
• Rocket fuel manufacturing
Potential Sources:
• Chlorinated solvents manufacturing
• Plastic, lacquer, varnish & paint manufacturing
• Pesticide production
• Textile processing
• Paper manufacturing
• Probable human carcinogen
• Probable human carcinogen
NDMA is formed relatively easily in a variety of processes, including drinking water disinfection with chlorine or chloramine. This emerging contaminant, often associated with only rocket fuel contamination, is being detected in water supplies throughout North America.
1,4-Dioxane is most commonly used in industry as a stabilizer in chlorinated solvents such as trichloroethylene (TCE) and 1,1, 1-trichloroethane (TCA). 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.

The TrojanUVPhox installation in San Gabriel Valley, CaliforniaThe Trojan Solution

TrojanUV has supplied UV-oxidation treatment systems to all five groundwater treatment facilities in the Baldwin Park Operable Unit Superfund Site located in the San Gabriel Basin.

Four of the five systems use hydrogen peroxide in combination with UV (TrojanUV supplies NSF-grade hydrogen peroxide through USP Technologies). This turn-key solution includes full-service delivery of hydrogen peroxide to the plant.

The first TrojanUV system, at the La Puente Valley County Water District, replaced a competitor’s existing UV system based on the substantial operation and maintenance cost savings that the TrojanUV system provided. After testing the site’s water and optimizing the system based on the site’s water quality parameters, extensive permit testing was completed in November 2001.

This testing showed excellent NDMA and 1,4-dioxane destruction while reducing electricity consumption by over 80% when compared to the previous high-energy UV system. TrojanUV gained technology acceptance for use of its UV technology in drinking water at La Puente from the state regulator in January 2001. The system at the La Puente Treatment Facility has been delivering drinking water since May 2002.

These five systems help restore groundwater supplies that had been lost to contamination:

California Domestic Water Company

  • Flowrate: 14.4 MGD
  • Influent NDMA concentration: 200 ppt

San Gabriel Valley Water Company B5

  • Flowrate: 11.2 MGD
  • Influent NDMA concentration: 700 ppt

San Gabriel Valley Water Company B6

  • Flowrate: 11.2 MGD
  • Influent NDMA concentration: 900 ppt

Valley County Water District SA-1

  • Flowrate: 11.2 MGD
  • Influent NDMA concentration: 3,000 ppt

La Puente Valley County Water District

  • Flowrate: 3.6 MGD
  • Influent NDMA Concentration: 1,500 ppt
“Trojan was a great help in obtaining drinking water permit approval quickly from the California DHS – not to mention the fact that the reduction in power use with the Trojan system allowed us to negotiate a lower rate with the power company.”
Mike Berlien, Water District, Plant Manager
La Puente Valley County