Process modelling at Oldham sewage-treatment works using WRc STOAT

STOAT, which is a whole-process package, was used to examine the operation of an activated-sludge process. Initially, it was calibrated at low flow co nditions using data collected during a special 24-h survey together with ox ygen-transfer data and tracer-study results from earlier studies. The calib rated model was then used to (a) predict the values of the main operational characteristics for the plant, and (b) compare them with the data collecte d during a second special survey which, by chance, coincided with high flow conditions. This comparison showed that, to achieve a reasonable match bet ween the modelled and measured data, it was necessary to adjust some of the model parameters.