ESEL Paper Review_201307 24

By Hong Guo

Mail: hongguo@gist.ac.kr

Phone: (+82) (0)10 82276568

1, Title and Author

Title: Can a Stepwise Steady Flow Computational Fluid Dynamics Model

Reproduce Unsteady Particulate Matter Separation for Common Unit Operations?

Journal: Environ. Sci. Technol

Authors:

Pathapati SS, Sansalone JJ

Environmental Engineering and Sciences, University of Florida, 217 Black Hall, P.O. BOX 116450, Gainesville, Florida 32611

2. Summary of Paper

? This study examines if integrating a stepwise steady flow CFD model can reproduce PM separation by common unit operations loaded by unsteady flow and PM loadings, thereby reducing computational effort.

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3. Results

? Figure 3 illustrates the cumulative probabilities for PM mass separation by the VCF, PC, and HS as a function of PM diameter and influent flow rate. The maximum monitored flow rate for each unit is chosen as the upper limit. At high flow rates, the VCF and PC completely separate PM larger than 300 μm, while the HS separates PM larger than 2000 μm. At a low flow rate of 0.1 L/s the VCF and PC separate all PM larger than 30 μm.

? A gamma probability density function represents PM separation as a function of flow rate, Q, and particle diameter

? Variation of γ and β with flow is plotted in the right-hand column of Figure 3. Heterodispersivity of a PSD has been shown to be proportional to γ and inversely proportional to β.16 At a constant γ, an increasing β indicates a coarser PSD while for a constant β; an increasing γ indicates a finer PSD.

? Since PM separation is a function of the Unit’s appropriate form of surface are, surface area is utilized as primary design parameter and unit sizing index that is impacted by model error.

? The error generated by CFD modeling expresses the difference in PM separation from the measured PM separation. This difference is utilized to determine the additional SA required as a result of model error while achieving the same level of PM separation from the monitored physical model results.

? The SA increase that is generated from increasing model error (as RMSE) and illustrated as a factor of the existing unit SA is determined

through a linear correlation shown in Figure S3 of the Supporting Information.

? Table 2 summarizes event- based monitored and CFD modeled effluent PM mass. For Pm mass the error arising from the stepwise steady approach is lowest for the VCD and highest for the HS. At low flows, the stepwise steady model deviation from the full unsteady CFD model is lower than at high flows.

? The role of peak flow rate on the stepwise steady model error is pronounced for the PC and HS, in contrast to the VCF, where RMSE is low irrespective of flow.

? Figure 4 compares unsteady and stepwise steady models to monitored effluent PM mass. These intraevent results illustrate that the stepwise steady model for the VCF is relatively representative of monitored PM across each event.

? These intraevent results illustrate that the stepwise steady model for the VCF is relatively representative of monitored PM across each event. In comparison, there is increasing intraevent deviation from monitored PM results using the stepwise steady model for the PC and HS, respectively

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4. Contribution:

This research studies the behavior of activated sludge and the obtained profiles are very appropriate date for future studies.

5. Contact (Mail address): jd83@ufl.edu.