You are here:
Monitoring of Microbes in Drinking Water
Citation:
ASHBOLT, N. Monitoring of Microbes in Drinking Water. Presented at 2007 International Society for Exposure Analysis Annual Meeting, Raleigh, NC, October 15 - 18, 2007.
Impact/Purpose:
Presented at the 2007 International Society for Exposure Analysis Annual Meeting, October 15, 2007 in Raleigh, NC.
Description:
Internationally there is a move towards managing the provision of safe drinking water by direct assessment of the performance of key pathogen barriers (critical control points), rather than end point testing (i.e. in drinking water). For fecal pathogens that breakthrough the various barriers in a drinking water supply system, a residual chlorine concentration may provide further health protection. However, short-term failures (the most likely in systems) are likely to overwhelm the chlorine residual. Of even greater concern is the view that short-term failures are unlikely to be detected by either compliance-type routine monitoring of drinking waters or by pathogen-specific monitoring, such as monthly and more frequent for Cryptosporidium oocysts. On the other hand, a rapid drop in chlorine residual (preferably measured on-line) provides a good trigger for follow-up investigation, well ahead of results from routine microbiological assessment. An emerging issue, however, is the role of distribution system biofilms, which are ubiquitous and a potential site for pathogen accumulation and growth post water treatment. Biofilms are largely extracellular bacterial mucilage that can protect the microbial inhabitants from a residual disinfectant. Further, amoeba that predate on biofilm bacteria are known hosts for the selection of opportunistic bacterial pathogens, such as strains of Legionella, Mycobacterium and other pathogens. The role of biofilms/amoeba for antibiotic gene amplification/transfer has yet to be quantified. Hence, within the risk management paradigm for water system monitoring, assessing biofilm-pathogens deserves greater attention. In addition, we need to move on from only assessing diarrheal impact and include more severe and longer-lasting diseases (sequelae), such as arthritis and various cancers possibly caused by waterborne pathogens. In the future, perhaps we would be better protected by monitoring biofilms via a more metagenomic approach seeking to identify changes in community ecology and key genes? Views expressed are not necessarily those of the US-EPA.