AWWA JAW18747

Free and combined chlorine react with phenols adsorbed on granular activated carbon (GAC) to produce a series of oxidation products not formed in the absence of carbon. The potential for desorption of these products was examined in this study by introducing a strongly adsorbed product into the effluent of a GAC column and monitoring the concentration of the product throughout the column. Some of the products, e.g., p-benzoquinone, can be displaced into the effluent by the introduction of a strongly adsorbed compound, e.g., 2,4-dichlorophenol, into the influent. Other products, e.g., 4,4'-dihydroxybiphenyl, are very strongly adsorbed and occupy adsorption sites that would otherwise be available for removal of other compounds in the influent. In view of these findings and other undesirable effects of prechlorination, the authors recommend that processes resulting in the contact of chlorine with GAC be reevaluated. Includes 17 references, tables ,figures.