What's New in Glendale: Chromium 6 Removal Research
The Metropolitan Water District of Southern California
02/15/2011
While the presence of chromium 6 in drinking water throughout Los Angeles County was making the evening news in the year 2000, Glendale started up the Glendale Operable Unit (GOU), a treatment facility that was part of the EPA Superfund to clean up the San Fernando Groundwater Basin from Volatile Organic Compounds (VOC). The public was concerned because trace amounts of chromium 6 were present in the groundwater and after a year of public debate, expert testimony, and studies of various alternatives, a self-imposed chromium 6 limit of 5 parts per billion (ppb) allowed the GOU to continue to operate.
Since then Glendale has conducted the only research of its kind to remove chromium 6 from groundwater. The research moved from bench-scale testing to pilot-scale and, eventually, demonstration. Today, two facilities in Glendale are effectively removing chromium 6: Weak-Base Anion (WBA) Exchange and Reduction-Coagulation-Filtration (RCF).
The WBA facility shown below treats a 425 gpm groundwater well that is part of the GOU. It has two exchange vessels in lead and lag, and a carbon dioxide feed system for pH control. The influent chromium 6 concentration is 40 ppb, the effluent is currently at 2 ppb, and resin change-out takes place when the effluent reaches 5 ppb.
The RCF facility shown in the next photo is a 100 gpm system with a ferrous sulfate feed for reduction, mixing and aeration tanks, polymer feed, and dual media filters. Backwash water uses a fabric filter media in a dewatering container for sludge densification. The influent chromium 6 concentration is 80 ppb with the effluent ranging from 1 to 6 ppb.
The effort has been supported by U.S. Senators Dianne Feinstein and Barbara Boxer and Rep. Adam Schiff (CA 29th District). Numerous partners have provided funding: U.S. EPA, the state of California, the Water Research Foundation, the National Water Research Institute, the Association of California Water Agencies, and the cities of Los Angeles, Burbank, and San Fernando, for a total of $5.6 million thus far. (Metropolitan has provided in-kind funding.)
When the study began, the goal was to reduce chromium 6 concentrations to less than 5 ppb. The state of California has recently issued a draft Public Health Goal of 0.02 ppb, which, while not enforceable, influences public opinion and may result in a lower Maximum Contaminant Level (MCL) than previously anticipated. For the treatment technologies being tested to consistently achieve levels below 1 ppb, it is necessary to evaluate microfiltration as part of the RCF system. Further, for the state of California to establish an MCL, it is necessary to understand the limits and cost of removal for the various technologies.
Glendale has already prepared the scope of the research needed to study the effectiveness of microfiltration and to understand the cost of treatment, and estimates this additional effort will cost about $1.6 million.
