LINKING COLLOID DEPOSIT MORPHOLOGY AND CLOGGING

95 Pages·2013·2.19 MB·English

LINKING COLLOID DEPOSIT MORPHOLOGY AND CLOGGING:
INSIGHTS BY MEASUREMENT OF DEPOSIT FRACTAL DIMENSION
by
ERIC JAMES ROTH
B.F.A. University of Colorado Boulder, 2002
B.S. University of Colorado Denver, 2011

A thesis submitted to the
Faculty of the Graduate School of the
University of Colorado in partial fulfilment
of the requirements for the degree of
Master of Science
Civil Engineering Program
2013
This thesis for the Master of Science degree by
Eric James Roth
has been approved for the
Civil Engineering Program
by

David C. Mays, Chair

James C.Y. Guo

Tim C. Lei

November 12, 2013
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Roth, Eric James (M.S., Civil Engineering)
Linking Colloid Deposit Morphology and Clogging: Insights through Categorization by Fractal
Dimension
Thesis directed by Assistant Professor David C. Mays
ABSTRACT
Clogging is an important limitation to essentially any technology or environmental process
involving flow in porous media. Examples include (1) groundwater remediation, (2) managed or
natural aquifer recharge, (3) hydrocarbon reservoir damage, (4) head loss in water treatment filters,
(5) fouling in porous media reactors, and (6) nutrient flow for plants or bacteria. Clogging, that is, a
detrimental reduction in permeability, is a common theme in each of these examples. Clogging
results from a number of mechanisms, including deposition of colloidal particles (such as clay
minerals), which is the focus of this research.
Colloid deposits reduce porosity, which is recognized to play an important role in clogging, as
expressed in the Kozeny-Carman equation. However, recent research has demonstrated that colloid
deposit morphology is also a crucial variable in the clogging process. Accordingly, this thesis reports
a series of laboratory experiments with the goal of quantifying deposit morphology as a fractal
dimension, using an innovative technique based on static light scattering (SLS) in refractive index
matched (RIM) porous media. For experiments conducted at constant flow, with constant influent
suspension concentration, and initially clean porous media, results indicate that increased clogging is
associated with colloid deposits having smaller fractal dimensions, that is, more dendritic and space-
filling deposits. This result is consistent with previous research that quantified colloid deposit
morphology using an empirical parameter.
Clogging by colloid deposits also provides insight into the more complex clogging
mechanisms of bio clogging, mineralization, and bio mineralization. Although this line of work was
originally motivated by problems of clogging in groundwater remediation, the methods used and the
insight gained by correlating clogging with fractal dimension are expected to have relevance to other
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areas where flow in porous media overlaps with colloid science: Hydrogeology, petrology, water
treatment, and chemical engineering.

The form and content of this abstract are approved. I recommend its publication.
Approved: David C. Mays

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DEDICATION

This thesis is dedicated to scientists who aren’t afraid to take on insurmountable odds in the
effort to create a more balanced world. Also to those who realize that natural systems are complex,
and that a complete understanding of natural processes may ultimately be unattainable… but it’s
worth a shot.
Importantly, I would like to dedicate this thesis to my family. Thanks to my parents Jim and
Vera, my brother Paul, and my girlfriend Sarah for support and inspiration. In particular, I dedicate
this thesis to my daughter Ivy, with the hopes that insights gained through my research might improve
the natural environment that will someday be her inheritance.

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ACKNOWLEDGEMENTS

This research has passed through many hands before reaching mine. First, I must thank Dr.
David C. Mays, the Principal Investigator for this project. David kept the fire burning through almost
a decade of research which was sometimes extremely frustrating and always difficult. I couldn’t have
done my phase of the research without the efforts of my predecessors and collaborators: Asnoldo
Benitez, Kevin Kennedy, Kevin Harris, Adam Kanold, Orion Cannon, Ryan Taylor, and Michael
Mont-Eton. I would also like to thank Dr. Tim Lei for his optics expertise, Dr. Benjamin Gilbert for
his unparalleled knowledge of fractals and their measurement, and Ken Williams for his much
appreciated help at the Old Rifle field site. The U.S. Department of Energy Subsurface Biochemical
Research program provided funding for this research which was essential.

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TABLE OF CONTENTS
Chapter
1. Introduction……...….……………………………………………………………………………….1
1.1 Motivation…………………………………………………………………………………1
1.1.1 Groundwater Remediation……………………………………………………...1
1.1.2 Other Applications……………………………………………………...………2
1.1.3 Problems with Current Models…………………………………………………2
1.2 Background……...…………..…………………………………………………………….4
1.2.1 Flow Through Porous Media...…………………………………………………4
1.2.2 Colloids and Clogging………………………………………………………….6
1.2.3 Fractal Dimension……………………………………………………………....7
1.3 Overview…...……………………………………………………………………………....8
1.3.1 Type of Research……………………………………………………………….8
1.3.2 Problem Statement…………………………………………………………....…8
1.4 Research Scope………………………………………………………………………….…9
1.5 Experimental Framework…………………………………………………………………..9
2. Literature Review………....……………………………………………………………………...…11
3. Experimental Methods….……....…………………………………………………………………..13
3.1 Summary of the Experimental Approach……………………………………….………..13

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3.2 Apparatus Components………………………………………………………………...…14
3.2.1 Fluid Flow System…………………………………………………….……….14
3.2.2 Static Light Scattering Bench……………………………………………….…14
3.2.3 Head Data System……………………………………………………….……..15
3.3 Porous Media and Index Matched Fluid……………………………………………….…15
3.4 Colloids and Aggregation……………………………………………………………...…16
3.5 Other Measurements……………………………………………………………………...16
3.5.1 Specific Deposit………………………………………………………….…….16
3.5.2 Porosity………………………………………………………………….……..16
3.5.3 Critical Coagulation Concentration……………………………………….…...17
3.5.4 Collection and Analysis of Rifle Field Samples……………………………….17
3.6 Running the Experiments…………………………………………………………….…...17
3.7 Data Analysis……………………………………………………………………………..18
3.7.1 Fractal Dimension……………………………………………………………...18
3.7.2 Data Reduction..……………………………………………………………….19
4. Summary of Results………………………………………………………………………………..20
4.1 Critical Concentration and Porosity…………………………………………...………….20
4.2 Individual Samples………………………………………………………………..………20
4.3 Sample Sets………………………………………………………………………...……..29
5. Conclusion and Discussion…...……………………………………………………………...…….43
5.1 Individual Samples………………………………………………………………………..43
5.2 Sample Sets……………………………………………………………………………….43
5.3 Overall Conclusions………………………………………………………………………43
5.4 Discussion……………………………………………………………………………..….44
References……………………………………………………………………………………………..45

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Appendix
A. Experimental Data and Results……………………………………………………...……46
B. Additional Method Information………………………………………………………......75

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LIST OF FIGURES
Figure
1.1 Clogging by colloidal aggregates with different deposit morphology…………………..…6
1.2 Fractal dimension of aggregate structures…………………………………………………7
3.1 Experimental summary…………………………………………………………………...13
3.2 Experimental summary…………………………………………………………………...14
3.3 Flow cell during operation…………………………………………………….………….14
3.4 Flow cell schematic………………………………………………………………….……14
3.5 Static light scattering setup…………………………………………………………..…...15
3.6 IQ plot for determination of fractal dimension……………………………………..…….18
4.1 IQ plot for middle region………….……………………………………………………...21
4.2 Linear region of IQ plot with slope equal to fractal dimension………………………..…21
4.3 Head loss data during deposition and clear flow………………………………………....22
4.4 Specific deposit data……………………………………………………………………...22
4.5 Fractal dimension during deposition and clear flow…………………………………..….23
4.6 Fractal dimension versus normalized hydraulic conductivity…………………………....24
4.7 Fractal dimension versus pore flow velocity……………………………………………..24
4.8 Fractal dimension versus ionic strength……………………………………………..……25
4.9 Fractal dimension versus pore volumes eluted…………………………………………...25
4.10 Fractal dimension versus specific deposit…………………………………………….…26
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