AWWA ACE63221

Monochloramine reduction in fixed-bed reactors (FBRs) was quantified at three empty-bed contact times (EBCTs) using five types of granular activated carbon (GAC) and two background waters (lake water and synthetic organic-free water). For a given set of influent conditions, chosen to mimic that of drinking water utilities that practice chloramination, steady-state monochloramine effluent concentrations were reached following a period of higher removal. Steady-state monochloramine reduction varied with background water and GAC type. The deleterious impact of natural organic matter (NOM) was found to be directly related to the GAC surface area contained within pores greater than 2 nm in width, which indicated predominantly microporous GACs were suitable for monochloramine reduction in FBRs. While all GACs showed intrinsic catalytic capability for monochloramine reduction, such properties were enhanced with decreasing GAC acidity and the presence of nitrogen-containing functional groups such as lactams and imides. Includes 20 references, tables, figures.