In the framework of the EU-funded TTP-UPM project (Technology Transfer Proj
ect - Urban Pollution Management) the waste water treatment plant (WWTP) of
Tielt was modelled with the recently issued IAWQ ASM No. 2d model. Up to 4
1 % of the total COD load is originating from a textile industry. A measure
ment campaign was conducted during a period with industrial discharge and a
period with only domestic sewage. The stop of the industrial discharge res
ulted in a highly dynamic response of the system. Based on an expert-approa
ch the calibration was obtained changing only four parameters (anaerobic hy
drolysis reduction factor eta (fe), reduction factor for denitrification et
a (NO3) the decay rate of autotrophs b(AUT) and the decay rate of the bio-P
organism building blocks b(PAO), b(PHA), b(PP)). Influent fractionation re
mains a critical step within the model calibration. A proven procedure to c
haracterise the influent determinants by standard physical chemical analysi
s failed to assess the influent COD fractions when the textile waste water
is discharged to the WWTP. Selected bench-scale experiments, instead, succe
eded in providing the adequate influent characterisation accuracy. For char
acterising the readily biodegradable COD fraction respirometry is to be pre
ferred.