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.
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Published In
Journal of Environmental Engineering
Volume 149 • Issue 12 • December 2023
Copyright
© 2023 American Society of Civil Engineers.
History
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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