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Water 2018, 10(8), 1084; https://doi.org/10.3390/w10081084

Effect of Porous Baffles on the Energy Performance of Contact Tanks in Water Treatment

1
Department of Civil Engineering, Eskisehir Osmangazi University, Eskisehir 26480, Turkey
2
Civil Engineering Department, Bartın University, Bartın 74100, Turkey
*
Author to whom correspondence should be addressed.
Received: 18 July 2018 / Revised: 7 August 2018 / Accepted: 13 August 2018 / Published: 15 August 2018
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Abstract

Three-dimensional numerical simulations are performed to evaluate the effect of porous baffles on the efficiency of water treatment contact tanks. A second-order accurate numerical model is employed for the solutions of unsteady flow and tracer transport through the porous baffles. The flow through the porous medium is characterized while using the Darcy-Forchheimer relationship. Large Eddy Simulation (LES) model is used to simulate the instantaneous mixing of the tracer in the chambers of the contact tank. Three different porosities are considered to evaluate the effect of porosity on the hydraulic and mixing efficiencies of the contact tank. Simulated time-averaged flow field shows that porous baffles that are placed at the entrance of each chamber could successfully mitigate short-circuiting and yield plug-flow conditions through the system for low porosities. Flow in the contact tank becomes laminar as the flow velocities decrease due to viscous effects and inertial resistance in the porous zone. For this case, the tracer is transported with bulk flow through the system and leaves the contact tank with a high peak seen in the Residence Time Distribution (RTD) plot. Porous layer increases the hydraulic efficiency of the conventional design from “poor” to “good” according to the baffling factor and increases the overall efficiency from “compromising” to “good” according to the AD index. Comparison of the performance of the porous layer with the previously developed slot-baffle design shows that the slot-baffle design increases the efficiency of the tank with increasing dispersion effects, whereas the porous design increases hydraulic efficiency and reduces the dispersion effects. While the porous design reduces energy efficiency by 33% due to a drastic increase in drag in the flow through porous zone, the slot-baffle design increases the energy efficiency of the conventional design by 67%. View Full-Text
Keywords: water treatment; contact tank; energy performance; computational fluid dynamics (CFD); hydraulic and mixing efficiency; porous baffle; LES water treatment; contact tank; energy performance; computational fluid dynamics (CFD); hydraulic and mixing efficiency; porous baffle; LES
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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. (CC BY 4.0).
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Kizilaslan, M.A.; Demirel, E.; Aral, M.M. Effect of Porous Baffles on the Energy Performance of Contact Tanks in Water Treatment. Water 2018, 10, 1084.

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