Comparing Chlorination and Chloramination for Controlling Bacterial Regrowth

The Greater Vancouver (B.C.) Water District compared chlorine and chloramine as secondary disinfectants and their effects on bacterial regrowth in a distribution system supplied with disinfected, unfiltered surface water. The selected section of the distribution system was divided into three areas: a control area that received no secondary disinfectant, an area that received free chlorine as the secondary disinfectant, and an area that received chloramine. Water samples were analyzed for chlorine residual, coliform bacteria, heterotrophic plate count (HPC) bacteria, and turbidity. Although both chlorine and chloramine were effective in reducing bacterial growth in the distribution system, chloraminated water had a lower HPC, less taste and odor, fewer positive coliforms, and a more stable residual.