Reliable and high-quality drinking water is essential to the continued growth and prosperity of the American south-west. For the 245,000 residents of Scottsdale, Arizona, one of the region’s most important tourist and shopping destinations, the 2,330-kilometer Colorado River is the main water resource.

In 2009, supplies of safe drinking water came under threat. As part of the Central Arizona Project (CAP), water from the Colorado River is channelled to the Water Treatment Plant, where it is cleansed of harmful contaminants. However, the plant was no longer compliant with newly introduced federal rules, which regulate the amount of disinfection by-products (DBPs) in drinking water even more stringently.

Malcom Pirnie was invited to engineer a post-filtration treatment facility that incorporated granular activated carbon (GAC) adsorption technology – the most effective way to reduce contaminants in water. The result was the creation of one of the largest GAC facilities in the United States. The plant holds over 4 million pounds of GAC and has not only safeguarded the drinking water supply but also enabled cost savings by reducing chlorine usage by around 25%.