J Water Health 04 (2006) 297-312
Determination of protection zones for Dutch groundwater wells against virus contamination - uncertainty and sensitivity analysis
J. F. Schijven, J. H. C. Mülschlegel, S. M. Hassanizadeh, P. F. M. Teunis and A. M. de Roda Husman
Microbiological Laboratory for Health Protection, National Institute of Public Health and the Environment, P.O. Box 1, 3720, BA, Bilthoven, The Netherlands, Tel: +31 30 274 2994, Fax: +31 30 274 4434, E-mail: Jack.Schijven@rivm.nl
Centre for Inspectorate Research, Emergency Response and Drinking Water, National Institute of Public Health and the Environment, P.O. Box 1, 3720, BA, Bilthoven, The Netherlands, Tel: +31 30 274 3354, E-mail: Jan.Mulschlegel@rivm.nl
Hydrogeology Chair, Department of Earth Sciences, Utrecht University, Budapestlaan 4, P.O. Box 80021, 3508, TA, Utrecht, The Netherlands, Tel: +31 30 253 7464 (sec. +31 30 2535151), URL: http://www.geo.uu.nl/hydrogeology/majid.htmlE-mail: hassanizadeh@geo.uu.nl
Computerization and Methodological Consultancy Unit, National Institute of Public Health and the Environment, P.O. Box 1, 3720, BA, Bilthoven, The Netherlands, Tel: +31 30 274 2937, E-mail: Peter.Teunis@rivm.nl
Microbiological Laboratory for Health Protection, National Institute of Public Health and the Environment, P.O. Box 1, 3720, BA, Bilthoven, The Netherlands, Tel: +31 30 274 4325, E-mail: AM.de.Roda.Husman@rivm.nl
ABSTRACT
Protection zones of shallow unconfined aquifers in The Netherlands were calculated that allow protection against virus contamination to the level that the infection risk of 10−4 per person per year is not exceeded with a 95% certainty. An uncertainty and a sensitivity analysis of the calculated protection zones were included. It was concluded that protection zones of 1 to 2 years travel time (206–418 m) are needed (6 to 12 times the currently applied travel time of 60 days). This will lead to enlargement of protection zones, encompassing 110 unconfined groundwater well systems that produce 3 × 108 m3 y−1 of drinking water (38% of total Dutch production from groundwater). A smaller protection zone is possible if it can be shown that an aquifer has properties that lead to greater reduction of virus contamination, like more attachment. Deeper aquifers beneath aquitards of at least 2 years of vertical travel time are adequately protected because vertical flow in the aquitards is only 0.7 m per year.The most sensitive parameters are virus attachment and inactivation. The next most sensitive parameters are grain size of the sand, abstraction rate of groundwater, virus concentrations in raw sewage and consumption of unboiled drinking water. Research is recommended on additional protection by attachment and under unsaturated conditions.
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