Author ORCID Identifier
0009-0009-7277-6354
Document Type
Dissertation
Date of Award
5-31-2025
Degree Name
Doctor of Philosophy in Environmental Engineering - (Ph.D.)
Department
Civil and Environmental Engineering
First Advisor
Taha F. Marhaba
Second Advisor
Monroe Weber-Shirk
Third Advisor
Michel Boufadel
Fourth Advisor
Lisa Axe
Fifth Advisor
David Katoshevski
Abstract
Flocculation and clarification are two essential processes to deliver safe water at a reasonable cost to consumers. There are two major thrusts to the research presented in this dissertation. The first is to better characterize the physics and mixing parameters used for the design of hydraulic flocculators in the context of drinking water treatment plants. The second major thrust is to investigate floc filtration as a mechanism for the removal of primary particles during floc blanket clarification.
The intensity of mixing in environmental and chemical engineering applications is often characterized by the Camp and Stein velocity gradient. This parameter has come under significant criticism due to its imposition of two-dimensionality on a fundamentally three-dimensional quantity. The resulting simplification considers the shear components of the strain rate tensor without accounting for the normal components. A derivation of the pure shear form of the strain rate tensor is presented using mathematical arguments, and some discussion is presented regarding the applicability of the various forms of this tensor to mixing problems, such as flocculation.
The minor loss associated with the flow around baffles has historically had significant uncertainty. An improved understanding of the physics governing this flow can improve minor loss estimates for the hydraulic design of flocculators. Computational fluid dynamics (CFD) simulations are examined together with a dimensionally homogeneous physics-based model to predict minor loss as a function of flow rate and baffle geometry. Measurements of minor loss in plant-scale flocculators are presented together with CFD data to validate this model. Additionally, the uniformity of mixing intensity within a flocculator is discussed and a dimensionless parameter to scale the Camp and Stein velocity gradient is presented for various flocculator configurations.
To date, no mechanistic model has been proposed to describe floc blanket clarification. Of particular interest is a description of the degradation of removal performance with maturation of flocs within the clarifier. A simple physics-based population balance model (PBM) of floc blanket clarification is developed in light of a hypothesized floc filtration mechanism thought to be responsible for the removal of primary particles within floc blanket clarifiers. This model accounts for performance degradation by considering the limited capacity of flocs to capture primary particles. A series of pilot-scale fluidized bed clarifier (FBC) experiments are presented to demonstrate the applicability of the proposed floc filtration PBM. While some model tuning is required to fit the data from these experiments, experimental data and model fitting offer some key insights into how coagulant dose impacts the physics of floc filtration. The limitations of the PBM are discussed, and some additional avenues of future exploration are offered based on the current understanding of floc filtration.
Recommended Citation
Pennock, Andrew P., "An inquiry into the physics of mixing and floc filtration" (2025). Dissertations. 1837.
https://digitalcommons.njit.edu/dissertations/1837
Included in
Aerodynamics and Fluid Mechanics Commons, Environmental Engineering Commons, Physical Chemistry Commons
