Impact of biomass on the stability of HAAs and THMs in a simulated distribution system

This article addresses the biostability of trihalomethanes (THMs) and haloacetic acids (HAAs) in simulated distribution systems (annular reactors). The annular reactors were placed in two parallel trains at the effluent of a full‐scale treatment plant: one train received chlorinated water, and the other received chloraminated water. Each train was composed of two annular reactors in series. The upstream annular reactor received water with a disinfectant residual, and the downstream annular reactor received dechlorinated or dechloraminated water. In warm water (17–22°C) and in the absence of a disinfectant residual, the dihalogenated HAA species degraded in the downstream annular reactors of both trains (by ~75% in the chlorinated train and ~60% in the chloraminated train). These HAAs were not degraded, however, in cold water (12–14°C) or in the presence of a disinfectant residual. The THMs and the trihalogenated HAAs were not observed to degrade under the experimental conditions (i.e., 12‐h retention time in each annular reactor).