Granular Activated Carbon Adsorption of Carcinogenic Volatile Organic Compounds at Low Influent Concentrations.
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. 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 VOCs evaluated, with a CUR threshold less than 0.2 lbs/1000 gal. It may be possible to use 1,1 DCA and 1,2 DCA as surrogates for assessing chemicals near the feasibility limit.