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Research considerations for more effective groundwater monitoring
Citation:
STELMA, G. N. AND L. J. WYMER. Research considerations for more effective groundwater monitoring. JOURNAL OF WATER AND HEALTH. IWA Publishing, London, Uk, 10(4):511-521, (2012).
Impact/Purpose:
Edberg et al (2000) pointed out that one of the central questions of public health protection is: should one monitor the safety of drinking water for pathogens or indicators? They concluded that the answer in the year 2000 was the same as it had been in 1900: “Monitoring for indicators better protects human health than monitoring for specific pathogens”. This conclusion is as valid in 2011 as it was in 2000. Monitoring for individual pathogens is too difficult because we don’t know which of the many waterborne fecal pathogens will be present at any given time or place and it would be far too expensive to test or all of them. Furthermore, the methods used to measure pathogens are often difficult and costly to perform. Indicator monitoring could be made more effective by increasing sample volumes and/or sampling frequency and sampling at times when the source waters are most vulnerable to incursions by fecal contamination. Use of a suite of indicators or of qPCR instead of culture methods could also potentially make monitoring more effective. It should be kept in mind that monitoring alone is not sufficiently protective. The periodic sanitary surveys and hydrogeologic assessments required by the GWR are also critical in identifying and eliminating sources of pollution.
Description:
Since numerous pathogens can occur in feces, water has traditionally been monitored for fecal contamination by detecting fecal indicator organisms rather than the pathogens themselves. Although this approach is backed up by health effects data in recreational waters, it has been questioned when used for drinking water, particularly groundwater. Most outbreaks attributed to groundwater have occurred in systems that have not violated the US EPA’s maximum contaminant limit (MCL) for total coliforms in the 12 month period before the outbreak. In addition, more environmentally stable viruses and parasites have often been detected in drinking water samples in which indicators were not detected. Recent detections of E. coli O157:H7 and Campylobacter jejuni in groundwaters in the apparent absence of fecal indicators have also cast some doubt on the value of indicators for identifying water contaminated by bacterial fecal pathogens. Individual pathogen monitoring is now technically achievable but due to the large number of possible pathogens to monitor and the costs involved, it is currently not reasonable. There are several alternatives to pathogen monitoring that could significantly reduce the frequency at which pathogens occur in waters testing negative for indicators. These include: (i) increasing the sample volume used to detect indicators, (ii) increasing the frequency of monitoring, (iii) using a suite of indicators rather than a single indicator, (iv) using a more conservative PCR method rather than culturing, (v) sampling at times when fecal contamination is most likely present or (vi) any combination of these options.
