Suspended solid removal efficiency of plate settlers and tube settlers analysed by CFD modelling

Removal of suspended solids from raw water is one of the essential processes in water and wastewater treatment plants. The conventional sedimentation tanks in the water treatment plants occupy a large area and become expensive in urban areas. The use of plate settlers or tube settlers in sedimentation tanks to increase the efficiency and hence to reduce the footprint of sedimentation tanks is an economical solution in the water treatment industry. This study investigated the effectiveness of plate and tube settlers compared to the plain settlers in a water treatment plant. A three-dimensional computational fluid dynamics (CFD) model was set up using ANSYS-CFX 17.2. Seven cases of plain settlers, plate settlers, and tube settlers were analysed for the comparison of tube settler performances. The maximum removal efficiencies of all solid classes were approximately equal in both plate settlers and tube settlers, and they are around 100, 67, 28, and 9% for the solid classes with particle diameters of 41, 17, 9.5, and 5.0 mu m, respectively. The settling efficiency remained unchanged with the increase of the plate settling area beyond 60% of the plain settler area. The tube cross section shape does not affect the particle removal efficiency of a tube settler.