title: Examining the effect of length/width ratio on the hydro-dynamic behaviour in a DAF system using CFD and ADV techniques.
abstract: Dissolved air flotation (DAF) is a solid-liquid separation system that uses fine bubbles rising from the bottom to remove particles in water. In this study, we investigated the effect of L/W(L; length, W; width) on the hydrodynamic behavior in a DAF system using CFD (computational fluid dynamics) and ADV (acoustic Doppler velocimetry) technique. The factual full-scale DAF system, L/W ratio of 1:1, was selected and various UW ratio conditions (2:1, 3:1,4:1 and 5:1) were simulated with CFD. For modelling, 2-phase (gas-liquid) flow equations for the conservation of mass, momentum and turbulence quantities were solved using a Eulerian-Eulerian approach based on the assumption that a very small particle is applied in the DAF system. Also, for verification of CFD simulation results, we measured the actual velocity at some points in the full-scale DAF system with the ADV technique. Both the simulation and the measurement results were in good accordance with each other. We concluded that the L/W ratio and outlet geometry play an important role for flow pattern and fine bubble distribution in the flotation zone. In the ratio of 1:1, the dead zone is less than those in other cases. On the other hand, in the ratio of 5:1, the fine bubbles were more evenly distributed.
authors.affiliation: International Water and Wastewater Research Center, Korea Water Resources Corporation, Daejeon, South Korea.
authors.forename: S B
authors.initials: SB
authors.lastname: Kwon
authors.forename: N S
authors.initials: NS
authors.lastname: Park
authors.forename: S J
authors.initials: SJ
authors.lastname: Lee
authors.forename: H W
authors.initials: HW
authors.lastname: Ahn
authors.forename: C K
authors.initials: CK
authors.lastname: Wang
mesh_terms: D014865:Waste Disposal, Fluid / Q000379:methods*; D018508:Water Purification / Q000379:methods*