1. Kiwa Water Research, Department of Microbiological Water Quality and Health, P.O. Box 1072, 3430 BB , Nieuwegein, the Netherlands (E-mail: hans.vrouwenvelder@kiwa.nl)
2. Delft University of Technology, Department of Biotechnology, Environmental Biotechnology Group, Julianalaan 67, 2628 BC , Delft, the Netherlands (E-mail: hans.vrouwenvelder@wetsus.nl)
3. Vitens, P.O. Box 23, 6880 BC , Velp, the Netherlands
4. Ecole Nationale de Supérieure de Chimie, Rennes, France
5. Ecole Supérieure d'Ingénieur de Poitier, France
6. PWN Water Supply Company North-Holland, P.O. box 2113, 1990 AC , Velzerbroek, the Netherlands