Stormwater treatment: examples of computational fluid dynamics modeling

Abstract

Control of rainfall-runoff particulate matter (PM) and PM-bound chemical loads is challenging; in part due to the wide gradation of PM complex geometries of many unit operations and variable flow rates. Such challenges and the expense associated with resolving such challenges have led to the relatively common examination of a spectrum of unit operations and processes. This study applies the principles of computational fluid dynamics (CFD) to predict the particle and pollutant clarification behavior of these systems subject to dilute multiphase flows, typical of rainfall-runoff, within computationally reasonable limits, to a scientifically acceptable degree of accuracy. The Navier-Stokes (NS) system of nonlinear partial differential equations for multi-phase hydrodynamics and separation of entrained particles are solved numerically over the unit operation control volume with the boundary and initial conditions defined and then solved numerically until the desired convergence criteria are met. Flow rates examined are scaled based on sizing of common unit operations such as hydrodynamic separators (HS), wet basins, or filters, and are examined from 1 to 100 percent of the system maximum hydraulic operating flow rate. A standard turbulence model is used to resolve flow, and a discrete phase model (DPM) is utilized to examine the particle clarification response. CFD results closely follow physical model results across the entire range of flow rates. Post-processing the CFD predictions provides an in-depth insight into the mechanistic behavior of unit operations by means of three dimensional (3-D) hydraulic profiles and particle trajectories. Results demonstrate the role of scour in the rapid degradation of unit operations that are not maintained. Comparisons are provided between measured and CFD modeled results and a mass balance error is identified. CFD is arguably the most powerful tool available for our profession since continuous simulation modeling.

Keywords

stormwater / unit operations and processes (UOPs) / hydrodynamic separation / filtration / adsorption / computational fluid dynamics (CFD) / turbulence modeling / discrete phase model / particle separation / detention/retention basins / clarification

References

[1] Sansalone J J. Physical and chemical nature of stormwater pollutants. In: Field R, Sullivan D, eds. Wet Weather Flow in the Urban Watershed. Boca Raton: CRC Press, 2002, 43–66

[2] Andoh R Y G, Saul A J. The use of hydrodynamic vortex separators and screening systems to improve water quality. Water Science and Technology, 2003, 47(4): 175–183

[3] USEPA. Stormwater technology fact sheet – Hydrodynamic Vortex Separators. EPA 832–99–017. 1999

[4] Kim J Y, Sansalone J J. Event-based size distributions of particulate matter transported during urban rainfall-runoff events. Water Science and Technology, 2008, 42(10–11): 2756–2768

[5] Sansalone J J. Adsorptive infiltration of metals in urban drainage—media characteristics. Science of the Total Environment, 1999, 235(1–3): 179–188

[6] Geldof G, Jacobsen P, Fujita S. Urban storm water infiltration perspectives. Water Science and Technology, 1994, 29(1–2): 245–254

[7] Wilson M A, Gulliver J S, Mohseni O, Hozalski R M. Assessing the effectiveness of proprietary stormwater treatment devices. In: Proceedings of World Environmental & Water Resources Conference, Tampa, FL, USA, 2007

[8] Rossman L A. Stormwater Management Model Users Manual, Version 5.0, USEPA/600/R-05/040, Cincinnati, OH, USA, 2007

[9] Huber W C, Dickinson R E. Storm Water Management Model User’s Manual, Version 4, EPA/600/3–88/001a (NTIS PB88–236641/AS). U.S. Environmental Protection Agency, Athens, GA, USA, 1988

[10] Huber W C. BMP Modeling Concepts and Simulation. EPA/600/R-06/033, U.S. Environmental Protection Agency, Washington D C, USA, 2006

[11] Weib G J. Vortex separator: proposal of a dimensioning method. Water Science and Technology, 1997, 36(8–9): 201–206

[12] Paul T C, Sayal S K, Sakhuja V S, Dhillon G S. Vortex-settling basin design considerations. Journal of Hydraulic Engineering, 1991, 117(2): 172–189

[13] Keblin V, Barrett M, Malina J, Charbeneau R. The effectiveness of permanent highway runoff controls: sedimentation/filtration systems. CRWR Online Report 97–4, University of Texas at Austin, 1997

[14] Curtis J S, van Wachem B. Modeling particle-laden flows: a research outlook. American Institute of Chemical Engineers, 2004, 50(11): 2638–2645

[15] Dickenson J A, Sansalone J J. Discrete phase model representation of particulate matter (PM) for simulating PM separation by hydrodynamic unit operations. Environmental Science & Technology, 2009, 43(21): 8220–8226

[16] Pathapati S S, Sansalone J J. Can a stepwise steady flow computational fluid dynamics model reproduce unsteady particulate matter separation for common unit operations? Environmental Science & Technology, 2011, 45(13): 5605–5613

[17] Stovin V R, Saul A J. Efficiency prediction for storage chambers using computational fluid dynamics. Water Science and Technology, 1996, 33(9): 163–170

[18] Stovin V R, Saul A J. A computational fluid dynamics (CFD) particle tracking approach to efficiency prediction. Water Science and Technology, 1998, 37(1): 285–293

[19] Naser G, Karney B W, Salehi A A. Two-dimensional simulation model of sediment removal and flow in rectangular sedimentation basin. Journal of Environmental Engineering, 2005, 131(12):1740–1749

[20] Jayanti S, Narayanan S. Computational study of particle-eddy interaction in sedimentation tanks. Journal of Environmental Engineering, 2004, 130(1): 37–49

[21] Faram M G, Harwood R. A method for the numerical assessment of sediment interceptors. In: Proceedings of 3rd international Conference on Sewer Processes and Networks, Paris, France, 2002

[22] Tyack J N, Fenner R A. Computational fluid dynamics modeling of velocity profiles within a hydrodynamic separator. Water Science and Technology, 1999, 39(9): 169–176

[23] Guo Q, England G, Johnston C E. Development of certification guidelines for manufactured stormwater BMPs. ASCE/EWRI task committee on guidelines for certification of manufactured stormwater best management practices (BMPs). In: Proceedings of World Environmental and Water Resources Congress EWRI, 2008

[24] Gulliver J S, Guo Q, Wu J S. Scaling relations for manufactured stormwater BMPs. ASCE/EWRI Task Committee on Guidelines for Certification of Manufactured Stormwater Best Management Practices (BMPs). In: Proceedings of World Environmental and Water Resources Congress, 2008

[25] USEPA. Urban stormwater BMP performance monitoring. A Guidance Manual for Meeting the National Stormwater BMP Database Requirements, EPA-821-B-02–001, 2002

[26] Annandale G W. Scour Technology. New York: McGraw-Hill Professional, 2005, 24–25

[27] Pathapati S, Sansalone J. Application of CFD to Stormwater Clarification Systems. In: Proceedings of World Environmental and Water Resources Congress EWRI, 2007

[28] Rushton B. Broadway outfall stormwater retrofit project (Phase II – Monitoring CDS unit and constructed pond). Draft Report to EPA and Southwest Florida Water Management District (SFWMD), 2006, 124

[29] American Society for Testing and Materials (ASTM). Standard test method for determining sediment concentration in water samples. Annual Book of Standards, Designation: D 3977–97, Vol. 04.08, Philadelphia, 2000, 395–400

[30] American Society for Testing and Materials (ASTM). Standard practice for dry preparation of soil samples for particle size analysis and determination of soil constants. Annual Book of Standards, Designation: D 421–85. Vol. 04.08, Philadelphia, 1993, 8–9

[31] Finlayson-Pitts B J, Pitts J N. Chemistry of the Upper and Lower Atmosphere –Theory, Experiments and Applications. CA: Academic Press, 2000, 365–368

[32] American Society for Testing and Materials (ASTM). Automated Pore Volume and Pore Size Distribution of Porous Substances by Mercury Porosimetry (ASTM Designation: BMP578–02). West Conshohocken, PA, USA, 2003

[33] Kim J Y, Ma J, Pathapati S, Sansalone J. Continuous deflective separation of non-colloidal particulate matter in rainfall-runoff. In: Proceedings of the 3rd Annual North American Surface Water Quality Conference and Exposition, Forrester Communications. CA: Palm Desert, 2004

[34] Sheng Y, Ying G, Sansalone J J. Differentiation of transport for particulate and dissolved water chemistry load indices in rainfall-runoff from urban source area watersheds. Journal of Hydrology (Amsterdam), 2008, 361(1–2): 144–158

[35] Urbonas B R. Recommended parameters to report with BMP monitoring data. Water Research, 1995, 121(1): 23–34

[36] Versteeg H, Malalasekera W. An Introduction to Computational Fluid Dynamics: The Finite Volume Method Approach. London: Prentice Hall, 1995

[37] Nowakowski A F, Cullivan J C, Williams R A, Dyakowski T. Application of CFD to modeling of the flow in hydrocyclones. Is this a realizable options or still a research challenge? Minerals Engineering, 2004, 17(5): 661–669

[38] Statie E C, Salcudean M E, Gartshore I S. The influence of hydrocyclone geometry on separation and fibre classification. Filtration and Separation, 2001, 38(6): 36–41

[39] Petty C A, Parks S M. Flow predictions within hydrocyclones. Filtration and Separation, 2001, 38(6): 28–34

[40] Launder B E, Spalding D B. The numerical computation of turbulent flows. Computer Method in Applied Mechanics, 1974, 3(2): 269–289

[41] Elghobashi S E. Particle laden turbulent flows: direct simulation and closure models. Applied Scientific Research, 1991, 48(3–4): 301–314

[42] Morsi S A, Alexander A J. An investigation of particle trajectories in two-phase flow systems. Journal of Fluid Mechanics, 1972, 55(02): 193–208

[43] Qi D, Lin W. TGrid: a new grid environment. In: Proceedings of First International Multi-Symposiums on Computer and Computational Sciences Conference (IMSCCS’06), 2006

[44] Barth T J, Jespersen D. The design and application of upwind schemes on unstructured meshes. In: Proceedings of AIAA 27th Aerospace Sciences Meeting, 1989

[45] Patankar S. Numerical Heat Transfer and Fluid Flow. Atlanta, USA: Hemisphere Publishing Corporation, 1980

[46] Ranade V V. Computational Flow Modeling for Chemical Reactor Engineering. London: Academic Press, 2002

RIGHTS & PERMISSIONS

2014 Higher Education Press and Springer-Verlag Berlin Heidelberg