Figure 4: Volume of activated sludge (VAS) in the cylinder as a function of cohesion coefficient according to the "classical" relation (constants: V0=30 mL; Vasc upload velocity=4 m/h). The figure shows that the sludge volume (and thus its height) in the cylinder is higher when K is small. The low cohesion leads to greater sludge expansion for (Vasc) equal ascending rate.