1. EAWAG, Swiss Federal Institute for Environmental Science and Technology Ueberlandstr. 133, PO Box 611, CH-8600 Duebendorf, Switzerland, (E-mail: hansruedi.siegrist@eawag.ch or leiv.rieger@modeleau.ca)
2. ifak, Institute f. Automation and Communication, Barleben, Germany, (E-mail: jens.alex@ifak-md.de)