California water agencies could be required to spend millions of dollars to remove hexavalent chromium if the California Office of Environmental Health Hazard Assessment draft health goal of 0.06 parts per billion is adopted.
A study by the California Dept. of Health Services survey of 7,000 drinking water sources showed a third contained levels of at least 1 microgram per liter of chromium 6, a possible carcinogen made famous by a lawsuit successfully argued by environmental activist attorney Erin Brockovich.
According to James Borchard, vice president and water technology expert for the Southern California office of MWH Americas, Inc., an ultra-low level could lead to widespread treatment requirements beyond the aerospace and manufacturing areas currently screening for chromium. “As many as 30% of wells could be impacted,” Borchard said.
If the goal is adopted in the next two years, that could lead to the California Dept. of Public Health (CDPH) setting drinking water maximum contaminant level standards “as close to the corresponding Public Health Goal as is economically and technically feasible.” This could occur by 2013. The regulation would take effect immediately, but the time allowed for each agency to comply would depend on the size of the problem and the impact to the community.
This would be the first chromium 6-specific regulation in the country. The federal government currently only regulates total chromium levels at 100 parts per billion. The state limit is 50 parts per billion. Russell Ford, vice president and principle technologist for CH2M Hill in Colorado, said other states — and countries — are watching what California does. “California often leads when it comes to regulation,” Ford said.
Not all agencies are waiting for the rules to be set. Glendale Water and Power built two demonstration plants that are expected to start processing water by the end of September. A Weak-Base Anion (WBA) system will push 425 gpm of water through a pair of lead/lag pressure vessels installed in series with upstream acid addition. A Reduction Coagulation Filtration system adds excess ferrous iron to 100gpm of water to break down chromium 5 to chromium 3, which is then precipitated along with the resulting ferric iron. Filtration removes floc after aeration and coagulation. Although the sediment must still be disposed of efficiently.
“Small volumes are easily treated, it is larger system that cost more to operate,” said Peter Kavounas, Glendale Water and Power assistant general manager for water.
Current processes for removing chromium 6 include in situ treatment of groundwater, including geochemical fixation, permeable reactive barriers and reactive zones. Electrokinetics and phytoremediation could also play a role in the future. Treatment for water already above ground include anion exchange, chemical reduction and membrane screening. All of these treatments are used to remove other materials, but would have to be optimized for chromium 6 as this low level if already in place.
Borchard estimated testing, studying, designing and constructing a treatment facility can take two to four years. “The cost can be substantial,” Borchard said. “To reach these levels could cost several million dollars per wellhead and a half million dollars annually in operation costs.”
