A Model for Characterizing the Process of Activated Sludge Compression Settling

Based on batch settling tests, a model describing the compression settling stage was developed and validated by experimental data. A equation determining the critical point when the compression settling stage commences, and a new velocity function for compression settling process were deduced from the model. It was shown that compression settling velocity, time and sludge concentration of the critical point occurrence depend on the initial sludge concentrations, the initial sludge blanket height and the sludge characteristic. Dividing the entire settling process of activated sludge into the zone settling and compression settling stages, and describing them by respective velocity models was more reasonable for characterizing the entire settling behaviour of activated sludge. The method was applied to predict the sludge blanket height during batch settling tests, and the results showed that the settling processes could be simulated well.