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Chloramine Concentrations within Distribution Systems and Their Relationship on Heterotrophic Bacteria (HPC), Nontuberculous Mycobacteria (NTM) and Disinfection Byproducts (DBPs)
Citation:
Pfaller, S., M. Donohue, D. Wahman, J. Pressman, J. Mistry, D. King, G. Abulikemu, AND M. Alexander. Chloramine Concentrations within Distribution Systems and Their Relationship on Heterotrophic Bacteria (HPC), Nontuberculous Mycobacteria (NTM) and Disinfection Byproducts (DBPs). Presented at WQTC, Cincinnati, OH, November 13 - 17, 2022.
Impact/Purpose:
EPA conducted a research study to understand how maintaining various drinking water distribution system disinfectant residual concentrations (affected by water age or operational practice) corresponded to the microbial communities (heterotrophic bacteria and Mycobacteria) found in the water, and the formation of disinfection byproducts (trihalomethanes (THMs) and haloacetic acids (HAAs)). This presentation builds upon previous work presented at WQTC titled: “Understanding Impacts and Meaning of Maintaining Detectable Residuals in Distribution Systems” by Mr. Mistry, Dr. Pressman and Dr. Wahman. Sampling was conducted at four utilities at the following four locations representing: (1) system entry point (EP), (2) near a storage tank, (3) state residual monitoring site or average residence time (ART), and (4) maximum residence time (MRT). Samples were analyzed for pathogens, disinfectant residual, THM, and HAA. Culture analyses were conducted for nontuberculous mycobacterium (NTM) and heterotrophic bacteria (HPC). In addition, qPCR was used to detect the following NTM species M. abscessus, M. intracellulare, and M. avium. Heterotrophic bacteria and NTM were detected in all four water utility distribution systems during the four sampling events. Microbial control of HPC and NTMs were immediately lost at locations beyond the EP. Microbial control in this study is define as maintain HPC values below 500 CFU/mL and NTM counts below 600 CFU/500mL. Detections correlated with residual loss (i.e., lowest microbial concentrations in the entry point and becoming higher with increasing distance within the distribution system). Disinfectant residuals were not enough to control for the occurrence of Mycobacterium abscessus and Mycobacterium intracellulare/chimaera which was detected by qPCR in > 50% of samples, nor controlled for other clinically relevant mycobacteria like M. mucogenicum, which was frequently isolated by culture. There was no relationship between the microbial concentration and THM/HAA formation. Overall, the project provides data on the occurrence of pathogens and DBPs in four different water systems with varying chloramine residual concentrations.
Description:
EPA conducted a research study to understand how maintaining various drinking water distribution system disinfectant residual concentrations (affected by water age or operational practice) corresponded to the microbial communities (heterotrophic bacteria and Mycobacteria) found in the water, and the formation of disinfection byproducts (trihalomethanes (THMs) and haloacetic acids (HAAs)). This presentation builds upon previous work presented at WQTC titled: “Understanding Impacts and Meaning of Maintaining Detectable Residuals in Distribution Systems” by Mr. Mistry, Dr. Pressman and Dr. Wahman. Sampling was conducted at four utilities at the following four locations representing: (1) system entry point (EP), (2) near a storage tank, (3) state residual monitoring site or average residence time (ART), and (4) maximum residence time (MRT). Samples were analyzed for pathogens, disinfectant residual, THM, and HAA. Culture analyses were conducted for nontuberculous mycobacterium (NTM) and heterotrophic bacteria (HPC). In addition, qPCR was used to detect the following NTM species M. abscessus, M. intracellulare, and M. avium. Heterotrophic bacteria and NTM were detected in all four water utility distribution systems during the four sampling events. Microbial control of HPC and NTMs were immediately lost at locations beyond the EP. Microbial control in this study is define as maintain HPC values below 500 CFU/mL and NTM counts below 600 CFU/500mL. Detections correlated with residual loss (i.e., lowest microbial concentrations in the entry point and becoming higher with increasing distance within the distribution system). Disinfectant residuals were not enough to control for the occurrence of Mycobacterium abscessus and Mycobacterium intracellulare/chimaera which was detected by qPCR in > 50% of samples, nor controlled for other clinically relevant mycobacteria like M. mucogenicum, which was frequently isolated by culture. There was no relationship between the microbial concentration and THM/HAA formation. Overall, the project provides data on the occurrence of pathogens and DBPs in four different water systems with varying chloramine residual concentrations.