Citation:

Kempisty, D., R. Summers, G. Abulikemu, N. Deshpande, J. Rebholz, K. Roberts, AND J. Pressman. Granular Activated Carbon Adsorption of Carcinogenic Volatile Organic Compounds at Low Influent Concentrations. AWWA Water Science. John Wiley & Sons, Inc., Hoboken, NJ, 1(2):e1128, (2019). https://doi.org/10.1002/aws2.1128

Impact/Purpose:

In 2011, the USEPA introduced a drinking water strategy to enhance public health protection by going beyond the traditional framework that regulates one contaminant at a time. Specifically, one of the strategies is to accelerate advancement of drinking water protection by addressing contaminants as a group (USEPA 2011). Additionally, with an MCLG of zero for the regulated carcinogenic volatile organic compounds (cVOCs), recent improvements in the analytical techniques provided an opportunity to assess if the MCLs of these compounds can potentially be lowered because MCLs need to be set as close to the MCLG as is feasible with the use of the best technology. These two drivers have led to interest in developing a group regulation for cVOCs that included both regulated and the emerging cVOCs. To assess technical feasibility to treat cVOCs to potential lower quantitation levels, this study was conducted to determine whether the designated Best Available Technologies (BATs) will cost-effectively treat these compounds to potential new quantitation levels. The BATs for the currently regulated cVOCs are granular activated carbon (GAC) and packed tower aeration (PTA). This research will be of interest to Regions, States, and water utilities that have cVOC contamination that requires treatment.

Description:

The effectiveness of granular activated carbon (GAC) for carcinogenic volatile organic compounds (cVOCs) has not been evaluated in the low- to sub- microgram per liter range. Rapid small scale column tests (RSSCTs) were employed to determine the GAC performance at empty bed contact times (EBCTs) of 7.5 and 15 minutes for 13 cVOCs at a target influent concentration of 5 µg/L in a typical groundwater matrix. Breakthrough was assessed for vinyl chloride, dichloromethane, 1,1-dichloroethane, 1,2-dichloroethane, 1,2-dichloropropane, carbon tetrachloride, 1,3-butadiene, 1,1,1,2-tetrachloroethane, 1,2,3-trichloropropane, trichloroethylene and tetrachloroethylene. Performance could not be assessed for benzene which degraded and for 1,1,2,2-tetrachloroethane because of trichloroethylene contamination. The throughput to breakthrough was found to be linearly correlated to capacities calculated with single-solute equilibrium isotherm parameters. Modest decreases, 9 to 13% on average, in throughput to 50% and 75% breakthrough were found when the EBCT was increased from 7.5 to 15 minutes. The carbon use rate (CUR), when scaled to simulate full-scale adsorption, indicated that GAC would be a viable technology for seven of the 11 VOCs evaluated, with a CUR threshold less than 0.2 lbs/1000 gal.

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