11 – Arsenic Removal Facility

Meeting Standards Early

Our Arsenic Removal Demonstration Plant is the largest of its kind in the world. The plant, located in an area rich in arsenic-laden volcanic rock, was completed in 2007. It was built in response to tougher United States EPA regulations in 2001 that decreased allowable arsenic levels in drinking water from 50 ppb to 10 ppb.

The plant uses ferric chloride to bind the arsenic, which can then be strained out of the water using micro-filters that are housed in 210 tubular modules. The micro-filters, which look like bundles of spaghetti, are actually membranes with pores 10 times smaller than a bacterium. The surface area of these membranes totals about 2.5 acres. Water entering the plant is typically about 30 ppb, but it is less than 4 ppb when it leaves.
The cleaned water, about 4.8 million gallons per day, is sent to west side reservoirs where it is combined with water from the Rio Grande as part of the San Juan – Chama Drinking Water project. This dual approach allowed the Water Authority to bring its entire service area into compliance with the new EPA regulations ahead of schedule.