1. Laboratory for Microbiological Health Protection, RIVM, P.O. Box 1, 3729BA Bilthoven, The Netherlands
2. Delft University of Technology, Civil Engineering & Geosciences, Delft, The Netherlands
3. PWN Waterworks, JW Lucasweg 2, 2031BE Haarlem, The Netherlands
4. Kiwa Research & Consultancy, P.O. Box 1072, 3430BB Nieuwegein, The Netherlands