Computational fluid dynamics study on attainable flow rate in a lamella settler by increasing inclined plates

Abstract

In the construction or renovation of settling tanks for water treatment systems, installing lamella baffles is a promising alternative to reduce the footprint. Conventionally, the increasing flow rate in a lamella settling tank is calculated based on the contribution of the entire projected area of inclined plates to lamella settler capacity. However, this design criterion is not fully verified. In this study, computational fluid dynamics (CFD) was used to simulate the sedimentation tank and lamella settling tank under different flow rates. Simulation results indicated that, at the targeted suspended solids (SS) removal efficiency of 82%, which corresponded to the original linear velocity of 1 m3/(m2·h), a 1.5-fold increase in flow rate required no less than a 6.2-fold increase in settling area using inclined plates. The actual effectiveness of baffles (α) on increased flow rate was estimated to be a maximum of 7.9%. Inclined plates had different influences on the SS removal efficiency of each particle group. Further, the baffle configuration was proven to influence the flow pattern and therefore the performance of the tanks. Using CFD, the SS removal efficiency in settling tanks and lamella setting tanks could be predicted accurately and their design could be significantly optimized.