DENVER, CO, Dec. 18, 2014 -- The Water Research Foundation (WRF), a sponsor of research supporting the water community, and the Soquel Creek Water District (SCWD) of California have collectively completed bench- and pilot-scale testing that explores water treatment process efficacies for removing hexavalent chromium (Cr(VI)) from the District's groundwater supplies.
The primary goals of the study were to evaluate Cr(VI) removal performance of strong base anion exchange (SBA-IX) and to compare and validate commercially available SBA-IX resin performance in terms of Cr(VI) exchange capacity, regeneration quality and frequency requirements. These tests also investigated innovative brine management techniques, including brine reuse and treatment methods, which would render the spent brine waste less hazardous and reduce expenses due to costly disposal.
In July of 2014, the California State Water Resources Control Board Department of Drinking Water adopted the nation's first maximum contaminant level (MCL) for Cr(VI) in drinking water, which has been demonstrated to be a human carcinogen when inhaled at elevated levels. SCWD represents one of the many districts heavily impacted by this new MCL and the potential implications of increased treatment process costs. Together with WRF, a research study was developed to explore full-scale treatment design and answer key operational questions that may impact utility capital and lifecycle costs.
The study was broken into two phases. The first phase -- SBA-IX testing at a bench-scale level -- addressed three primary goals:
- Determining optimal empty bed contact time to conduct subsequent experiments
- Screening SBA-IX resins to identify the best-performing resin for SCWD's wells
- Demonstrating SBA-IX treatment performance through multiple loading and regeneration cycles
The second phase -- on-site pilot-scale testing -- was conducted at SCWD's San Andreas well site and addressed its own unique set of goals:
- Demonstrating bench-scale results that could be replicated at pilot-scale
- Determining the feasibility of reusing the sodium chloride regenerant brine
- Generating sufficient brine to conduct treatment investigations at bench-scale
Research conducted with water from the San Andreas well proved that SBA-IX can be effective for Cr(VI) treatment under the given water quality conditions. At bench and pilot-scales, commercially available SBA-IX resins were able to achieve a high treatment capacity. The feasibility of direct brine reuse was also proven at pilot-scale. High treatment capacities along with brine reuse and treatment approaches reduce the typical challenges associated with SBA-IX treatment, namely large volumes of spent brine requiring costly disposal.
These results are encouraging for other water utilities, particularly those in California with similar raw water quality conditions that may soon be impacted by the final Cr(VI) MCL. "This research project demonstrated a viable treatment method for hexavalent chromium and developed an innovative method to minimize residuals," said Rob Renner, WRF executive director. "These results will be extremely valuable to utilities in California and states considering regulating hex chrome."
The research report, "Hexavalent Chromium Treatment with Strong Base Anion Exchange" (Project #4488), can be accessed through the WRF website. A related article is also included in the current edition of Advances in Water Research magazine, and additional information on hexavalent chromium can be found as a state of the science document also on the WRF website.
See also:
"CA sets final drinking water standard for hexavalent chromium"
"Hex Chrome in Drinking Water: A Review of Regulations and Testing Procedures"
About the Water Research Foundation
The Water Research Foundation is an internationally recognized leader in sponsoring research that supports the water community in holistically and cooperatively managing water from all sources to meet social, environmental, and economic needs. WRF’s research provides reliable and relevant solutions to the most critical challenges facing the water community today and into the future. Founded in 1966, WRF is a 501(c)(3) non‐profit organization that has sponsored nearly 1,500 research projects and serves more than 1,000 subscribing organizations. For more information, visit www.WaterRF.org.
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