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A Quantitative Microbial Risk Assessment (QMRA) model was developed for contamination events after mains repairs. The sensitivity analysis showed that the contamination concentration is the most important parameter, next to the pathogen dose response relation. The time of opening valves and of consumption are also important parameters. The event location within the network and the amount of consumption are of smaller importance. Issuing a boil water advice and opening only one valve before “releasing” the entire isolation section are effective measures to reduce the number of infected people per event by a factor of 2 to 4. [ABSTRACT FROM AUTHOR]

The design and evaluation of cost-effective treatment systems that produce safe drinking water with respect to Cryptosporidium and Giardia is based on the collection of quantitative information on: 1. theiroccurrence at abstraction points, which is used to set treatment goals or as design criterion, and 2. the elimination of surrogate parameters (spores) by treatment processes, which is used to demonstrate ifthe treatment goal is met under full-scale conditions. Both pathogenconcentrations in source water and the efficiency of a treatment process vary considerably over time. Multiple barriers in water treatment not only increased the overall treatment efficiency, but also reduced the variation in drinking water quality and thereby the probability of pathogen breakthrough. [ABSTRACT FROM AUTHOR]