You are here:
Chloramine Utility Maintenance - Is Free-Chlorine Conversion Helpful
Citation:
Donohue, M. Chloramine Utility Maintenance - Is Free-Chlorine Conversion Helpful. EPA-CDC NTM quarterly meeting, Cincinnati, OH, January 31, 2024.
Impact/Purpose:
To inform on NTM and DBPs changes that happen throughout a chlorine burn.
Description:
Many public utilities that use chloramine as a secondary disinfectant have adopted an annual maintenance practice called chlorine-burn. Chlorine-burn is a practice whereby free chlorine is permitted to flow through the distribution network for two to eight weeks. The purpose of a chorine-burn is to remove nitrifying bacteria and biofilm that cause nitrification. Nitrification is the buildup of nitrite and nitrate in the water supply. Nitrite and nitrates can have a cascading impact on water quality including residual levels, microbial concentrations, and disinfection byproducts (DBP). A Regional Applied Research Effort (RARE) study was conducted in EPA Region 6 to evaluate the impact of chlorine-burn on physiochemical water quality parameters, microbial concentrations, and disinfection byproducts (DBP) in distribution. The outcome of a chlorine-burn was assessed by collecting weekly samples from a relevant utility, over 15 weeks, covering 4 weeks pre-burn, 6 weeks free-chlorine treatment period, and 5 weeks post-burn. Physiochemical parameters (free chlorine, monochloramine, nitrite, nitrate, and free ammonia), microbial concentrations (heterotrophic bacteria [HPC], nontuberculous mycobacteria [NTM], M. abscessus and M. intracellulare), and disinfection byproducts (four trihalomethanes [THM4], and nine haloacetic acids [HAA9]) were measured. The microbial results shown no difference between pre- and post- burn; HPC: 7 x 104 vs 2 x 105 CFU/L, t-test: P= NS, NTM: 4 x 102 vs 5 x 102 CFU/L, t-test: P= NS, M. abscessus: 7 x 103 vs 9 x 103 GU/L, t-test: P= NS, and M. intracellulare: 2 x 102 vs 1 x 102, t-test: P= NS. The DBP results showed no difference between pre- and post- burn; THM4: 23.6 vs 26.4 µg /L, t-test: P= NS, and HAA9 ug/L 16.5 vs 26.3 µg/L, t-test: P= NS. The data showed that the post-burn results were not significantly different from the pre-burn results. Thus, for this utility, for the time-period and parameters evaluated, the chlorine-burn was not beneficial.