AWWA JAW64971

Five commercially available granular activated carbons (GACs) and two background waters were used to evaluate steady-state monochloramine reduction. Operation at steady state is appealing because it eliminates the need to replace or regenerate the filter media. Previous studies had found that monochloramine-GAC reactions reached steady state in fixed-bed reactors but that impractically large contact times were required to achieve low effluent concentrations at steady state under drinking water conditions. These experiments demonstrated that monochloramine reduction is a function of GAC type and source water characteristics such as pH and the presence of natural organic matter. Furthermore, results indicated that the more recently developed GACs, when combined with practical contact times (5 to 8 minutes, depending on pH), could generate water of sufficient quality for use in kidney dialysis, which is currently the most stringent application in terms of monochloramine removal. Monochloramine reduction with GAC could be used to facilitate trihalomethane cometabolism in drinking water filters, providing utilities with another tool to meet disinfection byproduct regulations. Includes 17 references, tables, figures.