Does an unknown mechanism accelerate chemical chloramine decay in nitrifying waters?

Most chloraminated water distribution systems experience accelerated chloramine loss after the onset of severe nitrification. It is commonly believed that nitrification (largely the nitrite and pH changes induced by nitrification) is the major cause of chloramine loss. The experiments described in this article showed that nitrite and pH or other known mechanisms are not sufficient to explain the decay observed in severely nitrifying bulk waters. By separating the microbial and chemical decay using the microbial decay factor method, the authors found that an unknown mechanism - suspected to be soluble microbial products - was responsible for accelerated chloramine decay. It is necessary to understand the basic mechanisms of accelerated chloramine decay in nitrified waters before control mechanisms are implemented. The findings of this study suggest that water providers dealing with accelerated chloramine decay should target the production and control of soluble microbial products released by microbes in addition to nitrification.