The Effect of Groundwater Temperature and DOM on Adsorption of cVOCs by GAC Adsorption

摘要

The U.S. EPA is investigating the possibility of modifying regulations that deal withrncarcinogenic volatile organic compounds (cVOCs). Changes could include reducing existingrnmaximum contaminant levels (MCLs) and creating standards for currently unregulatedrncompounds. Granular activated carbon (GAC) filters have been proven to be an effectiverntreatment strategy for cVOCs, but have not been studied at the proposed limits or with newrncompounds. The effect of temperature on GAC adsorption has not been studied in depth, but itrncould be an important factor in the kinetics of adsorption to GAC. Lab scale data has beenrngenerated at room temperature, which may not be accurate when using lab data for predictions ofrnGAC effectiveness for colder waters. In addition, the dissolved organic matter (DOM) in naturalrnwaters is also adsorbed by GAC filters, fouling them for cVOC adsorption, thereby increasingrncarbon use rates. This study examined the effectiveness of cVOC adsorption to GAC atrnmicrogram per liter limits, at 7℃, and the influence of background DOM.rnGroundwater temperatures vary between different regions, and the effects of temperaturernon GAC adsorption are not known. If there is an appreciable difference between the kinetics ofrn20℃ and 7℃ adsorption, prediction of GAC capabilities in colder waters needs adjustmentrnfrom lab temperature data. Using rapid small-scale column tests (RSSCTs), cVOC adsorptionrnwas studied using a natural groundwater with a DOM concentration of 1.5 mg/L. The coldrnRSSCT used groundwater refrigerated to 7℃. cVOCs studied were 1,1 dichloroethane, 1,2rndichloropropane, and 1,2,3 trichloropropane.