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Microbial pathogens in source and treated waters from drinking water treatment plants in the US
Citation:
Pfaller, S. Microbial pathogens in source and treated waters from drinking water treatment plants in the US. Ohio Chapter of the American Water Works Association Annual Meeting, 2017, Toledo, Ohio, September 26 - 29, 2017.
Impact/Purpose:
A major gap exists in our understanding of the ecology of waterborne pathogens, including their occurrence and potential inactivation or removal during drinking water treatment. This study was undertaken with the goal of obtaining occurrence information on microbial contaminants of known and emerging concern in source and treated drinking water. A secondary goal was to estimate removal of microbial contaminants from source waters by currently used drinking water treatment processes under typical plant operating conditions. Source and treated drinking water was collected from 25 drinking water treatment plants (DWTPs) located across the United States. Water samples were analyzed for the protozoa Giardia and Cryptosporidium (EPA Method 1623); the fungi Aspergillus fumigatus, A. niger and A. terreus (quantitative PCR [qPCR]); and the bacteria Legionella pneumophila (qPCR), Mycobacterium avium, M. avium subspecies paratuberculosis, and M. intracellulare (qPCR and culture). Treated waters were not tested for protozoa as they were rarely at detectable levels in source waters. Treatment was generally effective in reducing Aspergillus and Legionella to below detection levels. The exception is the mycobacteria, which were commonly detected in treated water, even when not detected in source waters.
Description:
An occurrence survey was conducted on selected pathogens in source and treated drinking water collected from 25 drinking water treatment plants (DWTPs) in the United States. Water samples were analyzed for the protozoa Giardia and Cryptosporidium (EPA Method 1623); the fungi Aspergillus fumigatus, A. niger and A. terreus (quantitative PCR [qPCR]); and the bacteria Legionella pneumophila (qPCR), Mycobacterium avium, M. avium subspecies paratuberculosis, and M. intracellulare (qPCR and culture). Cryptosporidium and Giardia were detected in 25% and in 46% of the source water samples, respectively (treated waters were not tested). Aspergillus fumigatus was the most commonly detected fungus in source waters (48%) but none of the three fungi were detected in treated water. L. pneumophila was detected in 25% of the source water samples but in only 4% of treated water samples. M. avium and M. intracellulare were both detected in 25% of source water, while all three mycobacteria were detected in 36% of treated water samples. Five species of mycobacteria, M. mucogenicum, M. phocaicum, M. triplex, M. fortuitum, and M. lentiflavum were cultured from treated water samples. Although these DWTPs represent a fraction of those in the U.S., the results suggest that many of these pathogens are widespread in source waters but that treatment is generally effective in reducing them to below detection limits. The one exception is the mycobacteria, which were commonly detected in treated water, even when not detected in source waters.