1. Process Development Group, Department of Chemical Engineering and Chemistry, Eindhoven University of Technology, P.O. Box 513, 5600 MB Eindhoven, The Netherlands, Mesa+ Research Institute, Transducer Science Technology Group, University of Twente, P.O. Box 217, 7500 AE Enschede, The Netherlands, and Aquamarijn Microfiltration BV, Beatrixlaan 2, 7255 DB Hengelo, The Netherlands