Real-time Multi-stream Cr(VI) Monitor Validates RCOF Treatment Process at California Water Utility

Tuesday, August 8, 2017: 3:10 p.m.
Tom Williams , Aqua Metrology Systems, Ltd., Sunnyvale, CA
Vladimir Dozortsev, Ph.D. , Aqua Metrology Systems, Ltd., Sunnyvale, CA

Utilities employing drinking water remediation techniques to address hexavalent chromium [Cr(VI)] contamination must measure influent and effluent chromium levels to adequately control and optimize water treatment and removal processes. High frequency, reliable and accurate data is essential to process validation, yet laboratory analysis can take up to two weeks to return results. A new water quality instrument was developed to facilitate the real-time analysis of Cr(VI) using a novel sensitive voltammetric detector that allows selective determination for hexavalent and total chromium.

The first commercial application of the real-time Cr(VI) monitor was undertaken at a California Water Utility obtaining eighty-five percent of their water supply from a groundwater source where hexavalent chromium [Cr(VI)] is a naturally occurring mineral. As a result of Cr(VI) dissolving into the water supply, 8 of their 12 inland water wells contain elevated levels of Cr(VI) exceeding the regulatory limit. Whereas the regulatory MCL has been set at 10 ppb, these 8 wells average 13 ppb of Cr(VI).

A Reduction/Coagulation/Oxidation/Filtration (RCOF) process was pilot tested under a variety of simulated operational conditions. The Cr(VI) monitor was used to provide real-time and multi-stream analysis of influent and effluent chromium levels during the pilot. During pilot testing the Cr(VI) monitor helped capture a high frequency data stream which was combined with other process data to simulate the impact of operational changes on contaminant levels and help validate the RCOF treatment methodology. Examples of operational changes include varying chemical feed dosing levels, contact time, and backwash frequencies. The real-time input on chromium levels helped to keep the pilot project on time and aid in a cost-effective effective treatment design suitable for full-scale implementation.

The methodology, validation, performance and application of the real-time Cr(VI) monitor that aided in process design and validation will be presented.

Tom Williams, Aqua Metrology Systems, Ltd., Sunnyvale, CA

Vladimir Dozortsev, Ph.D., Aqua Metrology Systems, Ltd., Sunnyvale, CA