Simple Model for Coupled Hydraulic Flocculation-Sedimentation Performance
Publication: Journal of Environmental Engineering
Volume 149, Issue 12
Abstract
Because coagulation and flocculation do not remove suspended particles but condition particles for removal downstream, performance of these processes is assessed by relative removal of particles and organic matter in downstream processes. Predictive models of coagulation and flocculation performance do not include information about downstream processes, but they could be more generally applied if they did. In this paper, the AguaClara hydraulic flocculation model is modified so that a fitting parameter, , becomes a function of sedimentation capture velocity. Experimentally, tap water with 90 NTU of kaolinite clay was treated with six PACl doses of as Al, a hydraulic flocculation residence time of 6.5 min with a dimensionless flocculation product of 62,200, and six tube settler detention times of 8.4–1.4 min for capture velocities of 0.1 to , achieving settled turbidities of 0.21–82.5 NTU. The analysis revealed an exponential relationship between and the sedimentation capture velocity, which appears related to the shape of typical particle size distributions. An addition to the model that incorporates capture velocity lowered the normalized root mean square error of the data from 0.414 to 0.113 logarithmic performance ratio units. The updated model is more readily applied to water treatment plant design and analysis and allows for design trade-offs to be made when considering hydraulic flocculation and sedimentation process parameters.
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Data Availability Statement
Some or all data, models, or code, including the aggregated data and model algorithm, that support the findings of this study are available from the corresponding author upon reasonable request.
Acknowledgments
The authors are grateful to Dr. Karen Swetland for her assistance in interpreting the data she generated prior to this study, which were used to test the model. This material is based upon work supported by the National Science Foundation under Award no. 1437961 and by the National Science Foundation Graduate Research Fellowship Program under Grant no. DGE-1144153. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the National Science Foundation.
References
Argaman, Y., and W. J. Kaufman. 1970. “Turbulence and flocculation.” J. Sanitary Eng. Div. 96 (2): 223–241. https://doi.org/10.1061/JSEDAI.0001073.
Boller, M., and S. Blaser. 1998. “Particles under stress.” Water Sci. Technol. 37 (10): 9–29. https://doi.org/10.2166/wst.1998.0367.
Bordlemay Padilla, C. L. 2018. “2018 drinking water quality report.” In AWQR. Ithaca, NY: Cornell Univ.
Bratby, J., M. W. Miller, and G. V. R. Marais. 1977. “Design of flocculation systems from batch test data.” Water SA 3 (4): 173–182.
Bridgeman, J., B. Jefferson, and S. Parsons. 2008. “Assessing floc strength using CFD to improve organics removal.” Chem. Eng. Res. Des. 86 (8): 941–950. https://doi.org/10.1016/j.cherd.2008.02.007.
Bridgeman, J., B. Jefferson, and S. A. Parsons. 2010. “The development and application of CFD models for water treatment flocculators.” Adv. Eng. Software 41 (1): 99–109. https://doi.org/10.1016/j.advengsoft.2008.12.007.
Camp, T. R., and P. C. Stein. 1943. “Velocity gradients and internal work in fluid motion.” J. Boston Soc. Civ. Eng. 30 (4): 219–237.
Casson, L. W., and D. F. Lawler. 1990. “Flocculation in turbulent flow: Measurement and modeling of particle size distributions.” J. Am. Water Works Assoc. 82 (8): 54–68. https://doi.org/10.1002/j.1551-8833.1990.tb07010.x.
Chakraborti, R. K., and J. F. Atkinson. 2020. “Settling velocity analysis of natural suspended particles using fractal approach.” J. Environ. Eng. 146 (12): 04020138. https://doi.org/10.1061/(ASCE)EE.1943-7870.0001821.
Du, Y., W. H. Pennock, M. L. Weber-Shirk, and L. W. Lion. 2019. “Observations and a geometric explanation of the effects of humic acid on flocculation.” Environ. Eng. Sci. 36 (5): 614–622. https://doi.org/10.1089/ees.2018.0405.
Fair, G. M., and R. S. Gemmell. 1964. “A mathematical model of coagulation.” J. Colloid Sci. 19 (4): 360–372. https://doi.org/10.1016/0095-8522(64)90037-6.
Garland, C., M. Weber-Shirk, and L. W. Lion. 2017. “Revisiting hydraulic flocculator design for use in water treatment systems with fluidized floc beds.” Environ. Eng. Sci. 34 (2): 122–129. https://doi.org/10.1089/ees.2016.0174.
Haarhoff, J., and H. Joubert. 1997. “Determination of aggregation and breakup constants during flocculation.” Water Sci. Technol. 36 (4): 33–40. https://doi.org/10.2166/wst.1997.0080.
Haarhoff, J., and J. J. van der Walt. 2001. “Towards optimal design parameters for around-the-end hydraulic flocculators.” J. Water Supply Res. Technol. AQUA 50 (3): 149–160. https://doi.org/10.2166/aqua.2001.0014.
Hudson, H. E. 1965. “Physical aspects of flocculation.” J. Am. Water Works Assoc. 57 (7): 885–892. https://doi.org/10.1002/j.1551-8833.1965.tb01476.x.
Jarvis, P., B. Jefferson, J. Gregory, and S. Parsons. 2005. “A review of floc strength and breakage.” Water Res. 39 (14): 3121–3137. https://doi.org/10.1016/j.watres.2005.05.022.
Kawamura, S. 2000. Integrated design and operation of water treatment facilities. 2nd ed. New York: Wiley.
Liu, J., M. Crapper, and G. L. McConnachie. 2004. “An accurate approach to the design of channel hydraulic flocculators.” Water Res. 38 (4): 875–886. https://doi.org/10.1016/j.watres.2003.10.014.
Loth, E. 2008. “Drag of non-spherical solid particles of regular and irregular shape.” Powder Technol. 182 (3): 342–353. https://doi.org/10.1016/j.powtec.2007.06.001.
Moruzzi, R. B., J. Bridgeman, and P. A. G. Silva. 2020. “A combined experimental and numerical approach to the assessment of floc settling velocity using fractal geometry.” Water Sci. Technol. 81 (5): 915–924. https://doi.org/10.2166/wst.2020.171.
Pennock, W. H., F. C. Chan, M. L. Weber-Shirk, and L. W. Lion. 2016. “Theoretical foundation and test apparatus for an agent-based flocculation model.” Environ. Eng. Sci. 33 (9): 688–698. https://doi.org/10.1089/ees.2015.0558.
Pennock, W. H., L. W. Lion, and M. L. Weber-Shirk. 2021. “Design algorithm for vertically-baffled flocculators.” Environ. Eng. Sci. 38 (7): 592–606. https://doi.org/10.1089/ees.2020.0288.
Pennock, W. H., M. L. Weber-Shirk, and L. W. Lion. 2018. “A hydrodynamic and surface coverage model capable of predicting settled effluent turbidity subsequent to hydraulic flocculation.” Environ. Eng. Sci. 35 (12): 1273–1285. https://doi.org/10.1089/ees.2017.0332.
Roth, E. J., M. E. Mont-Eton, B. Gilbert, T. C. Lei, and D. C. Mays. 2015. “Measurement of colloidal phenomena during flow through refractive index matched porous media.” Rev. Sci. Instrum. 86 (11): 113103. https://doi.org/10.1063/1.4935576.
Schulz, C. R., and D. A. Okun. 1984. Surface water treatment for communities in developing countries. New York: Wiley.
Smoluchowski, M. 1917. “Versuch einer mathematischen Theorie der Koagulationskinetik kolloider Lösungen.” Z. Phys. Chem. 92 (2): 129–168.
Swetland, K. A., M. L. Weber-Shirk, and L. W. Lion. 2014. “Flocculation-sedimentation performance model for laminar-flow hydraulic flocculation with polyaluminum chloride and aluminum sulfate coagulants.” J. Environ. Eng. 140 (3): 04014002. https://doi.org/10.1061/(ASCE)EE.1943-7870.0000814.
Swift, D. L., and S. K. Friedlander. 1964. “The coagulation of hydrosols by Brownian motion and laminar shear flow.” J. Colloid Sci. 19 (7): 621–647. https://doi.org/10.1016/0095-8522(64)90085-6.
Tambo, N., and Y. Watanabe. 1979. “Physical characteristics of flocs—I. The floc density function and aluminium floc.” Water Res. 13 (5): 409–419. https://doi.org/10.1016/0043-1354(79)90033-2.
Tse, I. C., K. Swetland, M. L. Weber-Shirk, and L. W. Lion. 2011. “Fluid shear influences on the performance of hydraulic flocculation systems.” Water Res. 45 (17): 5412–5418. https://doi.org/10.1016/j.watres.2011.07.040.
Walski, T., K. Minnich, C. Sherman, L. Strause, and B. Whitman. 2017. “Can there be a law of conservation of turbidity.” Procedia Eng. 186 (Mar): 372–379. https://doi.org/10.1016/j.proeng.2017.03.233.
Weber-Shirk, M. L., and L. W. Lion. 2010. “Flocculation model and collision potential for reactors with flows characterized by high Peclet numbers.” Water Res. 44 (18): 5180–5187. https://doi.org/10.1016/j.watres.2010.06.026.
Weber-Shirk, M. L., and L. W. Lion. 2015. “Fractal models for floc density, sedimentation velocity, and floc volume fraction for high Peclet number reactors.” Environ. Eng. Sci. 32 (12): 978–982. https://doi.org/10.1089/ees.2015.0302.
Yan, M., D. Wang, J. Yu, J. Ni, M. Edwards, and J. Qu. 2008. “Enhanced coagulation with polyaluminum chlorides: Role of pH/alkalinity and speciation.” Chemosphere 71 (9): 1665–1673. https://doi.org/10.1016/j.chemosphere.2008.01.019.
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© 2023 American Society of Civil Engineers.
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Received: Mar 27, 2023
Accepted: Aug 21, 2023
Published online: Oct 16, 2023
Published in print: Dec 1, 2023
Discussion open until: Mar 16, 2024
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