Upper Valley Water Treatment Plant
Arsenic is the twelfth most common element found in the human body and twentieth most common in the Earth's crust. The presence of arsenic in El Paso's groundwater is a result of the water coming into contact with arsenic-bearing rocks and gravel over time.
Since 1943, the maximum amount of allowable arsenic in U.S. drinking water has been set at 50 parts per billion (ppb). In January of 2001, the Environmental Protection Agency (EPA), announced a revision to that regulation to change the standard to 10 ppb effective January 2006. In order to comply with that standard with regards to the Mesilla Bolson, where El Paso obtains 19% of its water, the El Paso Water Utilities designed and constructed the Upper Valley Water Treatment Plant.
The Upper Valley Water Treatment Plant removes naturally occurring arsenic found within the 21 groundwater wells that make up the Canutillo well field. The plant will treat up to 30 million gallons per day (MGD) of groundwater for blending with up to another 30 MGD of untreated groundwater to produce a finished product with an arsenic concentration of 8 ppb or less.
Arsenic reacts very strongly to iron, so an iron salt is used to attract the arsenic as part of the removal process. Once reacted with the iron, the resulting precipitate settles and is filtered from the water, leaving arsenic-free water behind. This treated water is blended with untreated water; then other compounds are added for pH adjustment, corrosion control and final disinfection. The finished water is sent to the Canutillo Booster Pump Station where it is then distributed to the upper valley, west side and areas beyond the city limits, such as Canutillo, Vinton and Westway.
The Upper Valley Water Treatment Plant is one of the largest facilities in the nation that was constructed as a result of the EPA's revision to the federal regulation on arsenic concentration in drinking water.