It appears that the time span in which GAC will remove THMs can be measured in months - perhaps even years - at the Davenport, Iowa, water treatment facility. Research by EPA, the American Water Works Association, and other groups on the adsorptive capacity of granular carbon for trihalomethanes had indicated that removal of THMs by GAC is short-lived - measured in weeks. Therefore, it was of great interest to find the results at Davenport illustrated in Table 1. The THM reduction of 23 and 31 percent was achieved by an activated carbon* that had been on-line for more than 2 years and had processed more than 1 MG/cu.ft. of settled water. To check this result further, a pilot column was loaded with the spent carbon; tests (Table 2) again indicated a 25 percent reduction in THMs.
GAC Value Exceeds Expectation