Challenge
Located in San Bernardino County, California, the West Valley Water District is comprised of five treatment plants, 360 miles of pipeline, 25 reservoirs, 17 wells, 20,000 service connections, and serves drinking water to approximately 66,000 residents. Approximately 51% of their water supply comes from the 17 wells.
The West Valley Water District (WVWD) has wells in the Rialto Colton Groundwater Basin that are contaminated with high levels of perchlorate. Perchlorate is both a naturally occurring and manufactured chemical anion that consists of one chlorine atom bonded to four oxygen atoms (ClO). Perchlorate is commonly used as an oxidizer in such things as rocket propellants, munitions, fireworks, airbag initiators for vehicles, matches, and signal flares. The water source is within a designated Superfund site, and a special A 97-005 permit was required for the direct domestic use of an extremely impaired water source.
In 2016, WVWD opened the nation’s first perchlorate treatment facility to bring clean water directly to ratepayers. WVWD needed to double the amount of water it treated for perchlorate and wanted a system that was energy efficient and did not generate large amounts of solid waste. The new treatment train needed to be constructed within a portion of an existing building that was originally constructed to house a different treatment process. The treatment system needed to be constructed without impacting treatment operations. However, exterior walls of the building needed to be removed to set the equipment. The degree of difficulty was further increased because WVWD needed the exterior wall to be removed and replaced within a 24-hour window.
Carollo Engineers, Inc. worked on multiple fronts—assisting in securing funds, managing a complex process treatment design, and sequencing and staging a complicated construction workflow. Carollo obtained a grant from the US Department of Defense to develop a conceptual level design system that could be piloted and developed into a full-scale system. At the end of successful piloting, Carollo then assisted WVWD in obtaining a grant from the State of California Water Board to fund the remaining cost of construction to take the project to full scale. Carollo incorporated their patented Biottta two-stage biological treatment system developed for perchlorate removal. Construction of the project was led by Carollo Engineers, with support from PCL Construction as a primary subcontractor.
Results
Carollo Engineers designed, permitted, and constructed this first-ever fixed-bed biological perchlorate treatment system. One hundred percent of the project costs were funded through grants obtained from the US DoD and California Water Board. The treatment process went through exhaustive testing and proved to destruct perchlorate to non-detect levels, allowing the treated water to be introduced directly into the WVWD water distribution system. The system also demonstrated its ability to treat the water for nitrates and trichloroethylene (TCE) contaminants commonly found in this region.
