Indicator Systems for Assessing Public Health Risk in Waters Public
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For over one hundred years, indicator organisms such as coliforms have been measured as an index of public health risk from transmission of waterborne diseases. Even so, waterborne disease outbreaks have occurred in systems with negative coliform results, many traced to viral or protozoan etiologies. Conversely, no discernible public health outcomes have occurred in systems with positive coliform results. These inconsistencies arise because coliforms, as bacteria, respond differently to environmental stressors and engineered treatment processes than protozoan and viral pathogens. Recent reviews of four decades of indicator and pathogen monitoring indicated that coliphages are more highly correlated to pathogen presence in a variety of waters than coliforms. Therefore, the goal of this research was to re-examine a variety of traditional and novel indicator systems to determine their value as indicators, either singly or as a toolbox. We collected samples of animal feces, wastewaters, source waters and treated drinking waters. Samples were collected from four geographical regions of the United States (Northeast, South, Midwest and West) to assess spatial variability and in all four seasons to assess temporal variability. Samples were monitored for total coliforms, E. coli, male-specific and somatic coliphages, and other physical and chemical water quality parameters including organic carbon, pH and turbidity. The detection of coliforms and E. coli in this studyâ€™s drinking waters suggests fecal contamination and supports the need for indicator monitoring in drinking water systems. The strength of bacterial indicators (coliforms and E. coli) was supported in this study by the fact that there was no seasonal variance in wastewaters or drinking waters. In addition, coliforms and E. coli did not vary by region in drinking waters. Male-specific and somatic coliphages proved to be promising indicators. In this study, male-specific coliphages correlated to bacterial indicators in animal feces. Both coliphages were able to survive various environmental conditions, wastewater treatment, and drinking water treatment processes. Neither of the coliphages varied by season in untreated drinking waters. An area of concern for both male-specific and somatic coliphages was the high level of non-detects. The thermotolerance of male-specific coliphages is also an area of concern for its use as a good universal indicator.
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