Influence of Model Parameters and Inlet Turbulence Boundary Specification Methods in Secondary Settling Tanks: Computational Fluid Dynamics Study
Publication: Journal of Environmental Engineering
Volume 146, Issue 5
Abstract
Computational fluid dynamics (CFD) has been applied in secondary settling tank (SST) analysis for more than 30 years. Although great progresses has been achieved, there are still some uncertainties in CFD SST modeling. In this study, a numerical model is used to understand the effects of two model parameters: , accounting for particles with poor settling properties in the Takács settling model; and , the dry solids density. Both parameters are used in the user-defined functions to couple solids transport on settling velocity. Also, the differences in turbulence specification methods in prediction of SST performance are evaluated. The results show that the prediction of effluent suspended solids (ESS) is very sensitive to . The incorrect specification of may mask real improvements in SST geometry, and may even cause clarification failure prediction under the normal inflow conditions. The value of has less impact on ESS prediction, and its specification is less critical to maintain ESS prediction consistently with field data. Neither return activated sludge concentration (RAS) nor sludge blanket height (SBH) is sensitive to the effects of and . Additionally, the initial turbulent kinetic energy and turbulent dissipation rate specification methods produce only local effects on the hydrodynamics near the inlet boundary, and none of the performance indicators (ESS, RAS, or SBH) are sensitive to inlet boundary turbulence specification methods.
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Data Availability Statement
All data, models, and code generated or used during the study appear in the published article.
References
Bokil, S. D. 1972. “Effect of mechanical blending on the aerobic digestion of the waste activated sludge.” Ph.D. thesis, Dept. of Civil and Engineering, Univ. of Windsor.
Bürger, R., S. Diehl, and I. Nopens. 2011. “A consistent modelling methodology for secondary settling tanks in wastewater treatment.” Water Res. 45 (6): 2247–2260. https://doi.org/10.1016/j.watres.2011.01.020.
Burt, D. J. 2010. “Improved design of settling tanks using an extended drift flux model.” Ph.D. thesis, Dept. of Mechanical Engineering, Univ. of Bristol.
Daigger, G. T. 1995. “Development of refined clarifier operating diagrams using an updated settling characteristics database.” Water Environ. Res. 67 (1): 95–100. https://doi.org/10.2175/106143095X131231.
Das, S., H. Bai, C. Wu, J. H. Kao, B. Barney, M. Kidd, and M. Kuettel. 2016. “Improving the performance of industrial clarifiers using three-dimensional computational fluid dynamics.” Eng. Appl. Comput. Fluid Mech. 10 (1): 130–144. https://doi.org/10.1080/19942060.2015.1121518.
Deininger, A., E. Holthausen, and P. A. Wilderer. 1998. “Velocity and solids distribution in circular secondary clarifiers: Full scale measurements and numerical modelling.” Water Res. 32 (10): 2951–2958. https://doi.org/10.1016/S0043-1354(98)00072-4.
Ekama, G. A., J. L. Barnard, F. W. Gunthert, P. Krebs, J. A. McCorquodale, and E. J. Parker. 1997. Secondary settling tanks: Theory, modelling, design and operation. London: IAWQ.
Ekama, G. A., and P. Marais. 2004. “Assessing the applicability of the 1D flux theory to full-scale secondary settling tank design with a 2D hydrodynamic model.” Water Res. 38 (3): 495–506. https://doi.org/10.1016/j.watres.2003.10.026.
Gao, H., and M. K. Stenstrom. 2017. “Computational fluid dynamics applied to secondary clarifier analysis.” In Proc., World Environmental and Water Resources Congress 2017: Water, Wastewater, and Stormwater, Urban Watershed Management, and Municipal Water Infrastructure, edited by C. N. Dunn and B. VanWeele, 301–315. Reston, VA: ASCE. https://doi.org/10.1061/9780784480632.
Gao, H., and M. K. Stenstrom. 2018a. “Evaluation of three turbulence models in predicting of the hydrodynamics of a secondary sedimentation tank.” Water Res. 143 (Oct): 445–456. https://doi.org/10.1016/j.watres.2018.06.067.
Gao, H., and M. K. Stenstrom. 2018b. “Turbulence and inter-phase mass diffusion assumptions on performance of secondary settling tanks.” Water Environ. Res. 91 (2): 101–110. https://doi.org/10.1002/wer.1003.
Gao, H., and M. K. Stenstrom. 2019a. “Evaluating the effects of inlet geometry on the flux capacity of secondary settling tanks with computational fluid dynamics model and one-dimensional flux theory model.” J. Environ. Eng. 145 (10): 04019065. https://doi.org/10.1061/(ASCE)EE.1943-7870.0001582.
Gao, H., and M. K. Stenstrom. 2019b. “Generalizing the effects of the baffling structures on the buoyancy-induced turbulence in secondary settling tanks with eleven different geometries using CFD models.” Chem. Eng. Res. Des. 143 (Mar): 215–225. https://doi.org/10.1016/j.cherd.2019.01.015.
Gao, H., and M. K. Stenstrom. 2019c. “The influence of wind in secondary settling tanks for wastewater treatment—A computational fluid dynamics study. I: Circular secondary settling tanks.” Water Environ. Res. https://doi.org/10.1002/wer.1241.
Gao, H., and M. K. Stenstrom. 2019d. “The influence of wind in secondary settling tanks for wastewater treatment—A computational fluid dynamics study. II: Rectangular secondary settling tanks.” Water Environ. Res. https://doi.org/10.1002/wer.1244.
Griborio, A., and J. A. McCorquodale. 2016. “Lessons learned from 10 years of clarifier CFD modeling: The 2Dc experience.” In Proc., 89th Annual Water Environment Federation Technical Exhibition and Conf. (CD-ROM). Alexandria, VA: Water Environment Federation.
Guyonvarch, E., E. Ramin, M. Kulahci, and B. G. Plósz. 2015. “iCFD: Interpreted computational fluid dynamics-degeneration of CFD to one-dimensional advection-dispersion models using statistical experimental design: The secondary clarifier.” Water Res. 83 (Oct): 396–411. https://doi.org/10.1016/j.watres.2015.06.012.
Kinnear, D. J. 2002. “Biological solids sedimentation: A model incorporating in fundamental settling parameters.” Ph.D. thesis, Dept. of Civil and Environmental Engineering, Univ. of Utah.
Kleine, D., and B. D. Reddy. 2005. “Finite element analysis of flows in secondary settling tanks.” Int. J. Numer. Meth. Eng. 64 (7): 849–876. https://doi.org/10.1002/nme.1373.
Krebs, P., A. Stamou, J. L. Garcia-Heras, and W. Rodi. 1996. “Influence of inlet and outlet configuration on the flow in secondary clarifiers.” Water Sci. Technol. 34 (5–6): 1–9. https://doi.org/10.2166/wst.1996.0528.
Lakehal, D., P. Krebs, J. Krijgsman, and W. Rodi. 1999. “Computing shear flow and sludge blanket in secondary clarifiers.” J. Hydraul. Eng. 125 (3): 253–262. https://doi.org/10.1061/(ASCE)0733-9429(1999)125:3(253).
Larsen, P. 1977. On the hydraulics of rectangular settling basins: Experimental and theoretical studies. Lund, Sweden: Dept. of Water Resources Engineering, Lund Institute of Technology.
Li, B., and M. K. Stenstrom. 2014. “Research advances and challenges in one-dimensional modeling of secondary settling tanks: A critical review.” Water Res. 65 (Nov): 40–63. https://doi.org/10.1016/j.watres.2014.07.007.
McCorquodale, J. A., E. La Motta, A. Griborio, I. Georgiou, and J. Homes. 2004. Development of software for modeling activated sludge clarifier system. New Orleans, LA: Schielder Urban Environmental System Center, Univ. of New Orleans.
Patziger, M. 2016. “Computational fluid dynamics investigation of shallow circular secondary settling tanks: Inlet geometry and performance indicators.” Chem. Eng. Res. Des. 112 (Aug): 122–131. https://doi.org/10.1016/j.cherd.2016.06.018.
Patziger, M., H. Kainz, M. Hunze, and J. Jozsa. 2012. “Influence of secondary settling tank performance on suspended solids mass balance in activated sludge systems.” Water Res. 46 (7): 2415–2424. https://doi.org/10.1016/j.watres.2012.02.007.
Plósz, B. G., I. Nopes, L. Rieger, A. Griborio, J. D. Clercq, P. A. Vanrolleghem, G. T. Daigger, I. Takács, J. Wicks, and G. A. Ekama. 2012. “A critical review of clarifier modelling: State of the art and engineering practices.” In Proc., WWTmod2012—3rd IWA/WEF Wastewater Treatment Modelling Seminar, 27–30. Mont-Sainte-Anne, QC, Canada.
Ramin, E., D. S. Wagner, L. Yde, P. J. Binning, M. R. Rasmussen, P. S. Mikkelsen, and B. G. Plósz. 2014. “A new settling velocity model to describe secondary sedimentation.” Water Res. 66 (Dec): 447–458. https://doi.org/10.1016/j.watres.2014.08.034.
Ratkovich, N., W. Horn, F. P. Helmus, S. Rosenberger, W. Naessens, I. Nopens, and T. R. Bentzen. 2013. “Activated sludge rheology: A critical review on data collection and modelling.” Water Res. 47 (2): 463–482. https://doi.org/10.1016/j.watres.2012.11.021.
Rodi, W. 1980. Turbulent models and their application in hydraulics: A state of the art review. Delft, Netherlands: International Association for Hydraulics Research.
Saffarian, M. R., M. H. Hamedi, and M. Shams. 2010. “Comparison of various settling velocity functions and non-Newtonian fluid models in circular secondary clarifiers.” Korean J. Chem. Eng. 27 (5): 1497–1508. https://doi.org/10.1007/s11814-010-0253-0.
Saffarian, M. R., M. H. Hamedi, and M. Shams. 2011. “Numerical simulation of a secondary clarifier in a sewage treatment plant using modified Bingham model.” Can. J. Civ. Eng. 38 (1): 11–22. https://doi.org/10.1139/L10-106.
Samstag, R. W., J. A. McCorquodale, and S. P. Zhou. 1992. “Prospects for transport modeling of process tanks.” Water Sci. Technol. 26 (5–6): 1401–1410. https://doi.org/10.2166/wst.1992.0583.
Takács, I., G. G. Patry, and D. Nolasco. 1991. “A dynamic model of the clarification-thickening process.” Water Res. 25 (10): 1263–1271. https://doi.org/10.1016/0043-1354(91)90066-Y.
Tamayol, A., B. Firoozabadi, and M. A. Ashjari. 2009. “Hydrodynamics of secondary settling tanks and increasing their performance using baffles.” J. Environ. Eng. 136 (1): 32–39. https://doi.org/10.1061/(ASCE)EE.1943-7870.0000126.
Tarpagkou, R., and A. Pantokratoras. 2013. “CFD methodology for sedimentation tanks: The effect of secondary phase on fluid phase using DPM coupled calculations.” Appl. Math. Model. 37 (5): 3478–3494. https://doi.org/10.1016/j.apm.2012.08.011.
Vitasovic, Z. C., S. Zhou, J. A. McCorquodale, and K. Lingren. 1997. “Secondary clarifier analysis using data from the Clarifier Research Technical Committee protocol.” Water Environ. Res. 69 (5): 999–1007. https://doi.org/10.2175/106143097X125696.
Wahlberg, E. J., and T. M. Keinath. 1988. “Development of settling flux curves using SVI.” Water Pollut. Control Fed. 60 (12): 2095.
Wang, X., L. Yang, Y. Sun, L. Song, M. Zhang, and Y. Cao. 2008. “Three-dimensional simulation on the water flow field and suspended solids concentration in the rectangular sedimentation tank.” J. Environ. Eng. 134 (11): 902–911. https://doi.org/10.1139/l92-044.
Weiss, M., B. G. Plósz, K. Essemiani, and J. Meinhold. 2007. “Suction-lift sludge removal and non-Newtonian flow behaviour in circular secondary clarifiers: Numerical modelling and measurements.” J. Chem. Eng. 132 (1–3): 241–255. https://doi.org/10.1016/j.cej.2007.01.004.
Xanthos, S., M. Gong, K. Ramalingam, J. Fillos, A. Deur, K. Beckmann, and J. A. McCorquodale. 2011. “Performance assessment of secondary settling tanks using CFD modeling.” Water Resour. Manage. 25 (4): 1169–1182. https://doi.org/10.1007/s11269-010-9620-1.
Xanthos, S., K. Ramalingam, S. Lipke, B. McKenna, and J. Fillos. 2013. “Implementation of CFD modeling in the performance assessment and optimization of secondary clarifiers: The PVSC case study.” Water Sci. Technol. 68 (9): 1901–1913. https://doi.org/10.2166/wst.2013.280.
Xu, G., F. J. Yin, Y. J. Xu, and H. Q. Yu. 2017. “A force-based mechanistic model for describing activated sludge settling process.” Water Res. 127 (Dec): 118–126. https://doi.org/10.1016/j.watres.2017.10.013.
Zhou, S., and J. A. McCorquodale. 1992a. “Influence of skirt radius on performance of circular clarifier with density stratification.” Int. J. Numer. Meth. Fluid. 14 (8): 919–934. https://doi.org/10.1002/fld.1650140804.
Zhou, S., and J. A. McCorquodale. 1992b. “Mathematical modelling of a circular clarifier.” Can. J. Civ. Eng. 19 (3): 365–374. https://doi.org/10.1139/l92-044.
Zhou, S., and J. A. McCorquodale. 1992c. “Modeling of rectangular settling tanks.” J. Hydraul. Eng. 118 (10): 1391–1405. https://doi.org/10.1061/(ASCE)0733-9429(1992)118:10(1391).
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Published In
Journal of Environmental Engineering
Volume 146 • Issue 5 • May 2020
Copyright
©2020 American Society of Civil Engineers.
History
Received: May 29, 2019
Accepted: Oct 15, 2019
Published online: Mar 5, 2020
Published in print: May 1, 2020
Discussion open until: Aug 5, 2020
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