1. Systems and Control group, Wageningen University, Bornse Weilanden 9, P.O. Box
17, 6700 AA Wageningen, The Netherlands,
2. Sub-department of Environmental
Technology, Wageningen University, Bornse
Weilanden 9, P.O. Box 17, 6700 AA Wageningen, The Netherlands,
3. Laboratory of Microbiology, Wageningen University, Dreijenplein 10, 6703 HB Wageningen,
The Netherlands, and
4. Shell, Kesslerpark 1, 2288 GS, Rijswijk, The Netherlands