AWWA WQTC64071

Water treatment is an important barrier against pathogenic microorganisms in drinking water. Since testing the produced water for the absence of indicators is insufficient to verify water safety, Quantitative Microbiological Risk Assessment is now applied to better determine drinking water safety. Data from twelve treatment systems was analyzed in this study to develop methods to quantify pathogen reduction by a treatment system. Four approaches were evaluated. Applying triangular distributions based on reported reduction in literature instead of point estimates reduced uncertainty. Monitoring surrogates allowed a refinement of this triangular distribution. Microbiological sampling provided the most accurate estimate of nominal reduction, but could only be applied in the first stages of treatment. Modelling processes based on process conditions was most appropriate for disinfection processes. Simulations showed that the monitoring frequency can have a large impact on the outcome of the assessment. Thus, the presented QMRA methods provided input for verification of compliance to health based targets, risk identification, risk prioritization and designing monitoring in the water safety plan. Includes 38 references, figures.