ON-LINE MONITORING OF TRIHALOMETHANE CONCENTRATIONS IN DRINKING WATER DISTRIBUTION SYSTEMS USING MEMBRANE-BASED ON-LINE PURGE-AND-TRAP GAS CHROMATOGRAPHY

摘要

Chlorination continues to be the most effective and cost efficient disinfection process in the world. An unfortunate drawback of this process is the formation of disinfection byproducts (DBPs). Since DBPs, like the trihalomethanes, present a possible health risk, they are regulated in drinking water. The USEPA established a maximum contaminant level for the four regulated THMs (THM4) at 0.080 mg/L. Chloroform (CHCl3), bromodichloromethane (CHBrCl2), dibromochloromethane (CHBr2Cl) and bromoform (CHBr3) concentrations are typically monitored in drinking water by four USEPA approved methods, which include 502.2, 524.2, 551 and 551.1. These methods are very reliable with low method detection limit (MDL), accuracy and precision values; however, they are only designed to meet quarterly or yearly sampling rates for compliance monitoring. Adapting these methods to on-line monitoring, specifically, 551 and 551.1, would be difficult and expensive to perform. Presently, there is attention being placed on the development of an “ideal analyzer” for on-line monitoring of THM4 concentrations in drinking water distribution systems.