Evaluating the Effects of Inlet Geometry on the Limiting Flux of Secondary Settling Tanks with CFD Model and 1D Flux Theory Model
Publication: Journal of Environmental Engineering
Volume 145, Issue 10
Abstract
The effects of the McKinney baffle on the limiting flux of secondary settling tanks (SSTs) are evaluated by comparing the predictions of the maximum solids loading rate (SLR) determined by a Fluent-based, two-dimensional computational fluid dynamics (CFD) model with limits calculated by one-dimensional idealized flux theory (1DFT). SLR stress tests are simulated using three different stress testing methods to adjust flow rate, SLR, recycle ratio, and concentration of mixed liquor suspended solids. For each method, different flow conditions are used as the starting points for the CFD stress test. Limiting fluxes of the SST without and with the McKinney baffle are compared, and the SSTs failure mechanisms are analyzed. The simulations show that the McKinney baffle improves SST limiting flux by 1.4–2 times over the limiting of the original SST. Also, different (1) baffling structures; (2) stress testing methods; and (3) initial flow conditions for CFD stress tests influence the prediction of the limiting SLR. Therefore, routinely assuming a flux rating of 80% of the 1DFT limit is not recommended for all SSTs.
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Published In
Journal of Environmental Engineering
Volume 145 • Issue 10 • October 2019
Copyright
©2019 American Society of Civil Engineers.
History
Received: Dec 14, 2018
Accepted: Mar 1, 2019
Published online: Aug 6, 2019
Published in print: Oct 1, 2019
Discussion open until: Jan 6, 2020
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