Towards a Dynamic Compartmental Model of a Lamellar Settler

Abstract

Lamellar settlers are widely used in solid separation due to their relative high surface area paired with a small tank volume. Settlers exposed to high load variations may change their settling properties based on the variation of the flow pattern. Applying the critical point theory and coherent structure concept, a flow topology analysis was performed with the help of computational fluid dynamic simulations. The compartments were determined by the fluid flow, and the dynamic behavior of the compartments was taken into account. Under normal diurnal load variation, the architecture of the compartments did not change, in contrast to the mass transport between the zones, whereas the sludge removal process made significant changes in the architecture. The results showed two main flow zones with significant internal recirculation in the first zone. The hydraulic surface loading was examined in each zone, and the study revealed that the actual hydraulic load could be from 1.5 to 4.5 times much higher than that in individual zones due to recirculation eddies in the reactor tanks. The design hydraulic loading rate did not consider the local flow pattern. The discrete phase model approximation provided acceptable results, and the extent of the recirculation zone changed stepwise with different loads.