Abstract
Groundwater quality is often evaluated using microbial indicators. This study examines data from 12 international groundwater studies (conducted 1992–2013) of 718 public drinking-water systems located in a range of hydrogeological settings. Focus was on testing the value of indicator organisms for identifying virus-contaminated wells. One or more indicators and viruses were present in 37 and 15% of 2,273 samples and 44 and 27% of 746 wells, respectively. Escherichia coli (E. coli) and somatic coliphage are 7–9 times more likely to be associated with culturable virus-positive samples when the indicator is present versus when it is absent, while F-specific and somatic coliphages are 8–9 times more likely to be associated with culturable virus-positive wells. However, single indicators are only marginally associated with viruses detected by molecular methods, and all microbial indicators have low sensitivity and positive predictive values for virus occurrence, whether by culturable or molecular assays, i.e., indicators are often absent when viruses are present and the indicators have a high false-positive rate. Wells were divided into three susceptibility subsets based on presence of (1) total coliform bacteria or (2) multiple indicators, or (3) location of wells in karst, fractured bedrock, or gravel/cobble settings. Better associations of some indicators with viruses were observed for (1) and (3). Findings indicate the best indicators are E. coli or somatic coliphage, although both indicators may underestimate virus occurrence. Repeat sampling for indicators improves evaluation of the potential for viral contamination in a well.
Highlights
Groundwater is an important source of drinking water in both developed and developing countries
None of the indicators were associated with PCRmeasured viruses at the sample level, and only total coliforms, E. coli, and somatic phage were associated with PCR-viruses at the well level
All the indicators tended to have low sensitivities and positive predictive values, but high specificity and negative predictive values, which means groundwater that tests negative for the indicators is unlikely to be virus contaminated, but positive indicator tests do not necessarily mean there is virus contamination
Summary
Groundwater is an important source of drinking water in both developed and developing countries. It constitutes about 95% of the world’s accessible freshwater (Chilton and Seiler 2006; Howard et al 2006; McKay 2011) and is often used with little or no treatment (Pedley et al 2006). Contamination of groundwater with human enteric viruses is a global issue (Blaschke et al 2016; Gotkowitz et al 2016; Hynds et al 2014; USEPA 2006a, b), as consumption of contaminated water can result in elevated rates of endemic illness and waterborne disease outbreaks in affected communities (Beer et al 2015; Borchardt et al 2011; Cho et al 2014; Guzman-Herrador et al 2015; Hilborn et al 2013; Jack et al 2013; Wallender et al 2014; Zhou et al 2012). Waterborne viruses cause a wide range of illnesses, including gastroenteritis, paralysis, aseptic meningitis, conjunctivitis, diabetes, fevers, herpangina, rash, myocarditis, and respiratory illness, (Kitajima and Gerba 2015; WHO 2011).
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
