The Suitability of Coliphage as an Indicator of Potential Fecal Contamination in Groundwater Systems
Sharon C. Long
Over the years aquifers have been considered a clean source of drinking water as the soil acts as a natural filter. It.has been realized that groundwater used as a source of drinking water can be subject to fecal contamination through a number of various sources. With almost half of the United States national domestic water supply originatng from groundwater, a system of monitoring for contamination should be implemented to ensure public health and safety. Monitoring water to assess its microbial safety has long relied on the detection of indicator microorganisms, total and fecal coliforms in particular. Coliform bacteria has exhibited many limitations in its use as an indicator, including a lack of a significant correlation with the presence of pathogens, as well as a lack of behavioral similarities to pathogenic viruses and protozoa. The fact that coliform bacteria and viruses demonstrate different behavior including fate and transport characteristics,particularly through groundwater environments, has prompted research attention towards the use of other microorganisms as indicators of fecal contamination in groundwater. Coliphage viruses display more similarities to human pathogenic viruses both morphologically and behaviorally than do coliform bacteria. The use of both a viral and bacterial indicator microorganism in monitoring groundwater for possible fecal contamination is thought to more efficiently protect public health and safety. The objective of this research was to study the suitability of coliphage viruses as well as coliform bacteria as indicator organisms in New England groundwaters, and also to evaluate the current methods for detection of coliphages in groundwater. Groundwater samples were collected from around New England, specifically Massachusetts, and analyzed for total coliforms, fecal coliforms, and E. coli, as well as Fspecific and somatic coliphages. Standard Methods 9221 and 9222 were used to detect, enumerate, and confirm total coliforms, fecal coliforms, and E. coli. EPA Methods 1601 and 1602 were used to detect and enumerate coliphages, respectively. The results of the research were analyzed statistically using kappa analyses as well as correlation analyses to compare indicator occurrence and enumerations. It was obserVed that the different indicators all occurred in the groundwater samples but, in various concentrations and also in different samples. The lack of a significant relationship between the indicators occurrence and concentrations was expected and consistent with the literature. These results support the position that using multiple indicators including both a coliphage indicator as well as a bacterial indicator, rather than measuring either one alone will more efficiently determine groundwater vulnerability to fecal contamination. The results also displayed that neither of the coliphage detection methods are errorproof as they produced different results on the same groundwater samples.