An activated sludge model for biological N- and P-removal was developed, wh
ich describes anoxic and aerobic P-uptake based on bacterial metabolism. Th
is model was tested in practice on two wastewater treatment plants, which a
re BCFS(R)-processes, which contain activated sludge with a high fraction o
f denitrifying P-removing bacteria (DPB's). The model appeared to be able t
o give an adequate description of the performance of these treatment plants
under different conditions. If the process parameters are well defined alm
ost no calibration of the biokinetic parameters was necessary. In the simul
ation of Dalfsen wwtp, which has a complex control scheme, it was possible
to give an adequate simulation of the control actions and the concentration
profiles in a rather simple way, showing that detailed simulation of these
controllers was not necessary. With the calibrated model it was possible t
o analyse bottlenecks and give suggestions for upgrading of the concerned t
reatments plants. The simulation results were used in decisions on investme
nts. (C) 1999 IAWQ Published by Elsevier Science Ltd. All rights reserved.