The effect of filter cake viscoelasticity on filtration: a study of activated sludge dewatering

Wastewater is usually treated biologically, and a by-product from this treatment is waste-activated sludge with high water content. Sludge is therefore often filtrated to reduce the volume for handling and disposal, and to minimise the water content before incineration of the sludge. However, it is difficult to use the existing mathematical filtration models to simulate and optimise the filtration process. Activated sludge as well as synthetic model particles has been filtrated in this project. The study shows that compression of the formed filter cake is a time dependent process, and not only a function of pressure as assumed when using the conventional models. Moreover, it is shown how the existing filtration models can be modified and the filtration process for activated sludge simulated.