AWWA WQTC65873

Removal of groundwater contaminants, including arsenic, perchlorate, and total dissolved solids(TDS) in a high-silica groundwater using electrodialysis reversal (EDR) was evaluated. Pilotstudy results showed EDR as a viable treatment alternative for the Magna Water Company's(MWC) groundwater supply. Removal of perchlorate from the EDR concentrate usingbiofiltration was also evaluated.The MWC provides potable water to approximately 28,000 customers in the northwest section ofSalt Lake County, Utah. MWC water comes from two sources: groundwater from the Barton andHaynes Wellfields; and, treated surface water purchased from a neighboring water district.Groundwater contains arsenic ranging from 8 to 18 ug/L; TDS from 770 to 1350 mg/L; and silicanear 70 mg/L. Perchlorate has been measured at 14 ug/L in Barton Well No. 5 (BW5) and isexpected to impact additional wells in the near future.Perchlorate was first detected in BW5 in 1997. A six-month pilot study conducted in 1999 and2000 determined that EDR was a viable treatment alternative for perchlorate removal andshowed promise in removing arsenic. Studies in 2001 through 2003 evaluated separate treatmentalternatives of perchlorate and arsenic.A second pilot study conducted in 2004 and 2005 confirmed the use of EDR for multicontaminantremoval. The study showed that a two-stage EDR system removed perchlorate toless than 4 ug/L at feed concentrations of 10 and 25 ug/L. A four-stage system removedperchlorate to less than 4 ug/L at feed concentrations of 50 to 60 ug/L. At arsenic feedconcentrations of 10 ug/L, two-stage operation removed arsenic to less than 2 ug/L. The percentremoval of TDS was near 88 percent throughout piloting. Silica levels remained constant in feedand treated water, indicating silica was not impacting treatment.Removal of perchlorate from the EDR concentrate stream prior to discharge was also evaluatedusing an innovative biological treatment process (BIOBROx). EDR concentrate was blendedwith municipal wastewater and treated in a fixed-bed bioreactor. Piloting showed sustained,complete perchlorate destruction at a 10-minute empty-bed contact time without the addition ofan exogenous carbon source or nutrients. Alternative biological processes require 6 to 24 hoursof contact time and high concentrations of ethanol or acetic acid to achieve the same perchlorateremoval results in a concentrate stream.The simultaneous removal of arsenic, perchlorate, and TDS by EDR, followed by thebiodestruction of perchlorate in the concentrate stream represents a unique approach to acomplex water quality problem. Design of the full-scale EDR treatment system and biofiltrationsystem was completed in May 2007 and construction began in June 2007. This paper detailsarsenic, perchlorate, and TDS removal results from the 2005 to 2005 pilot study and describes thedesign approach used in full-scale implementation. Includes tables, figures.

Product Details

Edition:

Vol. - No.

Published:

11/01/2007

Number of Pages:

13

File Size:

1 file , 150 KB