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Chloramine Concentrations within Distribution Systems and Their Effect on Heterotrophic Bacteria, Mycobacterial Species, and Disinfection Byproducts
Citation:
Pfaller, S., D. King, J. Mistry, M. ALEXANDER, G. Abulikemu, J. Pressman, D. Wahman, AND M. Donohue. Chloramine Concentrations within Distribution Systems and Their Effect on Heterotrophic Bacteria, Mycobacterial Species, and Disinfection Byproducts. WATER RESEARCH. Elsevier Science Ltd, New York, NY, 205:117689, (2021). https://doi.org/10.1016/j.watres.2021.117689
Impact/Purpose:
Background: Chloramine is a disinfectant used to maintain microbial control throughout a public water suppliers’ distribution system. This current study investigated the relationship between chloramine concentration and heterotrophic plate counts (HPC) and nontuberculous mycobacteria (NTM) isolates in drinking water. Method: Water samples (64 total) collected on four occasions from four chloraminated systems at four locations; entry point (EP), average residence time (ART), near a tank (TANK), and maximum residence time (MRT) were analyzed for total chlorine and monochloramine. Traditional culture methods were applied for heterotrophic bacteria and NTMs, and specific quantitative polymerase chain reaction (qPCR) assays were used for the detection and quantification of Mycobacterium avium, M. intracellulare, and M. abscessus. Results: Total chlorine and monochloramine concentrations decreased between the EP (4.7 and 3.4 mg Cl2/L) to MRT (1.7 and 1.1 mg Cl2/L). Results showed that HPC and NTM control was lost by the time the water reached the ART location. Samples’ microbiological detection frequencies were: 86% (55/64) NTMs, 66% (42/64) heterotrophic bacteria, 64% (41/64) M. abscessus, 48% (31/64) M. intracellulare, and 2% (1/64) M. avium. Conclusion: This study shows that HPC and NTM were weakly correlated with disinfectant residual concentration. The results also demonstrate that chloramine is a weak disinfectant for NTM and several of its clinically relevant species. These data fill a critical knowledge deficiency regarding chloramine’s impact on HPC and NTM survival within public drinking water distribution systems.
Description:
Background: Chloramine is a disinfectant used to maintain microbial control throughout a public water suppliers’ distribution system. This current study investigated the relationship between chloramine concentration and heterotrophic plate counts (HPC) and nontuberculous mycobacteria (NTM) isolates in drinking water. Method: Water samples (64 total) collected on four occasions from four chloraminated systems at four locations; entry point (EP), average residence time (ART), near a tank (TANK), and maximum residence time (MRT) were analyzed for total chlorine and monochloramine. Traditional culture methods were applied for heterotrophic bacteria and NTMs, and specific quantitative polymerase chain reaction (qPCR) assays were used for the detection and quantification of Mycobacterium avium, M. intracellulare, and M. abscessus. Results: Total chlorine and monochloramine concentrations decreased between the EP (4.7 and 3.4 mg Cl2/L) to MRT (1.7 and 1.1 mg Cl2/L). Results showed that HPC and NTM control was lost by the time the water reached the ART location. Samples’ microbiological detection frequencies were: 86% (55/64) NTMs, 66% (42/64) heterotrophic bacteria, 64% (41/64) M. abscessus, 48% (31/64) M. intracellulare, and 2% (1/64) M. avium. Conclusion: This study shows that HPC and NTM were weakly correlated with disinfectant residual concentration. The results also demonstrate that chloramine is a weak disinfectant for NTM and several of its clinically relevant species. These data fill a critical knowledge deficiency regarding chloramine’s impact on HPC and NTM survival within public drinking water distribution systems.
URLs/Downloads:
DOI: Chloramine Concentrations within Distribution Systems and Their Effect on Heterotrophic Bacteria, Mycobacterial Species, and Disinfection Byproducts
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