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Analysis of the microbiological safety of drinking water. Experiences with handling records 2006-7

Analyse microbiologische veiligheid drinkwater. Ervaringen dossierbehandeling 2006-7

Synopsis

Based on historic data from drinking water companies in the Netherlands, in most cases a complete infectious risk assessment could be performed for the consumption of uncooked drinking water. According to Dutch legislation, the concentrations of the so-called index pathogens - enteroviruses, Campylobacter, Cryptosporidium and Giardia - in drinking water should be low enough not to exceed an infection risk of one person per ten thousand per annum. Using the numbers of index pathogens in the source waters for drinking water production and the reduction by treatment processes, a quantitative microbial risk assessment (QMRA) can be performed to assess whether the risk requirement are met. To this end, drinking water companies in the Netherlands collected historic data in records that were sent to the Regional Environmental Inspectorate. The National Institute for Public Health and the Environment (RIVM) evaluated these records and performed an provisional QMRA. Of the fourteen drinking water production locations that use surface water as their source, eight locations met the risk requirement for enteroviruses, nine for Campylobacter, nine for Cryptosporidium and nine for Giardia. For five locations it was unknown whether or not the risk requirement for enteroviruses had been met due to a lack of measurements and for one location the risk requirement was insufficiently demonstrated. For Campylobacter the risk requirement was insufficiently demonstrated in two locations and not met in three locations. For Cryptosporidium and Giardia the risk requirement was insufficiently demonstrated in two locations and not met in three locations. For Cryptosporidium and Giardia the risk requirement was insufficiently demonstrated in three locations and not met in two locations. Of a total of 197 groundwater production locations, 39 (20%) were reported as possibly vulnerable to contamination. A risk inventory of the groundwater wells resulted in the formulation and implementation of measures to improve groundwater well integrity.
 

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