IMPACT OF GALVANIC CORROSION ON LEAD RELEASE AFTER

168 Pages·2013·2.32 MB·English

IMPACT OF GALVANIC CORROSION
ON LEAD RELEASE AFTER
PARTIAL LEAD SERVICE LINE
REPLACEMENT

by

Emily Mi Zhou

A thesis submitted in conformity with the requirements
for the degree of Master of Applied Science
Graduate Department of Civil Engineering
University of Toronto
© Copyright by Emily Mi Zhou 2013
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IMPACT OF GALVANIC CORROSION ON LEAD RELEASE AFTER PARTIAL
LEAD SERVICE LINE REPLACEMENT

Emily Mi Zhou
Master’s of Applied Science, 2013
Graduate Department of Civil Engineering
University of Toronto

ABSTRACT

The EPA Lead and Copper Rule set action limits for lead and copper concentrations in
drinking water, but accelerated corrosion of lead in distribution systems due to a galvanic
connection to copper. Prior research has demonstrated that the effects of galvanic corrosion
can be controlled by water chemistry. This study not only investigated the main effects of
alkalinity, natural organic matter (NOM), nitrate, disinfectant and inhibitor to galvanic
corrosion, but also the interplay between these factors. A 2-level factorial (2 5-1) design was
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adopted which resulted in 16 testing conditions.

Results of bench-scale experiments using static pipes with lead and copper segments
demonstrated that alkalinity, disinfectant, inhibitor and alkalinity-inhibitor interaction had a
significant impact on galvanic current. The significant factors affecting total lead release
were alkalinity, NOM, disinfectant, alkalinity-inhibitor interaction, NOM-nitrate interaction,
NOM-disinfectant interaction, NOM-inhibitor interaction, nitrate-disinfectant interaction
and disinfectant-inhibitor interaction.

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ACKNOWLEDGEMENTS
Above all, I honor God his abundant love and mercy given to me unconditionally and the
continuous guidance and strength he has provided.
I am exceptionally appreciative to Prof. Robert Andrews and Prof. Ron Hofmann, my
supervisors, who were fundamental in my advancement, and was supportive throughout my
studies. Jim Wang was very helpful when dealing with equipment in the lab. Thanks also to
the rest of the Drinking Water Research Group for their help and support.
I give special thanks to my parents for their love and support.

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TABLE OF CONTENTS
ABSTRACT .................................................................................................................................... ii
ACKNOWLEDGEMENTS ........................................................................................................... iii
TABLE OF CONTENTS ............................................................................................................... iv
LIST OF TABLES ........................................................................................................................ vii
LIST OF FIGURES ......................................................................................................................... x
NOMENCLATURE ..................................................................................................................... xvi
1 Introduction ................................................................................................................................. 1
1.1 Background .......................................................................................................................... 1
1.2 Objectives ............................................................................................................................ 3
2 Literature Review ....................................................................................................................... 4
2.1 The Impact of Water Chemistry on Lead Corrosion ........................................................... 4
2.1.1 Chloride to Sulfate Mass Ratio ................................................................................ 4
2.1.2 Orthophosphate ........................................................................................................ 5
2.1.3 Disinfectant .............................................................................................................. 6
2.1.4 Natural Organic Matter ............................................................................................ 8
2.1.5 Nitrate ...................................................................................................................... 9
2.1.6 Sodium Silicate ...................................................................................................... 10
2.2 Aged Lead Pipes ................................................................................................................ 11
2.3 Relationship between Galvanic Current, Galvanic Corrosion and Lead Release ............. 12
3 Experimental Design ................................................................................................................ 14
3.1 Impact of Alkalinity, Nitrate, NOM, Disinfectant, Inhibitor on Lead Release after
Partial Lead Pipe Replacement .......................................................................................... 15
4 Materials and Methods ............................................................................................................. 19
4.1 Test Water Preparation ...................................................................................................... 19
4.1.1 NOM ...................................................................................................................... 19

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4.1.2 Nitrate .................................................................................................................... 20
4.1.3 Inhibitor ................................................................................................................. 20
4.1.4 CSMR .................................................................................................................... 21
4.1.5 Alkalinity ............................................................................................................... 21
4.1.6 pH .......................................................................................................................... 22
4.1.7 Disinfectant ............................................................................................................ 22
4.2 Analysis Methods .............................................................................................................. 23
4.2.1 Total Organic Carbon (TOC) ................................................................................ 23
4.2.2 pH .......................................................................................................................... 25
4.2.3 Chlorine and Monochloramine Residual ............................................................... 26
4.2.4 Oxidation-Reduction Potential .............................................................................. 26
4.2.5 Galvanic Current ................................................................................................... 26
4.2.6 Analysis of Silica, Phosphorus, Nitrate, Sulfate and Chloride .............................. 27
4.2.7 Lead Analysis ........................................................................................................ 27
4.3 Pipe Rig ............................................................................................................................. 28
5 Results ....................................................................................................................................... 30
5.1 Chlorine and Monochloramine Demand Test ................................................................... 30
5.1.1 Chlorine Demand Tests ........................................................................................ 30
5.1.2 Monochloramine Demand Tests ............................................................................ 36
5.1.3 Impact of Alkalinity and Inhibitor on Chlorine Demand ...................................... 41
5.2 Significant Factors Affecting Galvanic Current after Partial Lead Pipe
Replacement ...................................................................................................................... 45
5.2.1 Factors that Affect the Size of Galvanic Current .................................................. 45
5.2.2 Conductivity of Synthetic Water ........................................................................... 47
5.2.3 Significant Factors Affecting Galvanic Current .................................................... 50

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5.3 Water Quality Factors Affecting Total Lead Release after Partial Lead Pipe
Replacement ...................................................................................................................... 58
5.4 Water Quality Factors Affecting Dissolved Lead Release after Partial Lead Pipe
Replacement ...................................................................................................................... 77
5.5 Galvanic Current and Lead Release Relationship ............................................................. 87
5.6 Conclusions ....................................................................................................................... 91
6 Reference List ........................................................................................................................... 93
7 Appendices ............................................................................................................................. 100
7.1 Sample Calculations ........................................................................................................ 100
7.1.1 Chlorine Dose Required to Give a Specific Residual Concentration at the
Desired Time ....................................................................................................... 100
7.2 Experimental Procedures ................................................................................................. 101
7.2.1 Chlorine/monochloramine Demand Test............................................................. 101
7.2.2 pH Control by the Addition of Carbon Dioxide .................................................. 105
7.2.3 Measure Concentrations of Silica, Phosphorus, Nitrate, Sulfate and
Chloride ............................................................................................................... 107
7.3 Raw Data ......................................................................................................................... 117
7.3.1 Chlorine/monochloramine Demand Test............................................................. 117
7.3.2 Galvanic Current Data ......................................................................................... 124
7.3.3 Total Lead Data ................................................................................................... 125
7.3.4 Dissolved Lead Data ............................................................................................ 127
7.3.5 Test Water Parameters ......................................................................................... 128
7.3.6 Inhibitor Residual and Disinfectant Residual in the Weekly Composite
Water ................................................................................................................... 130
7.4 Preliminary Results ......................................................................................................... 133

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LIST OF TABLES
Table 1-1: Standard electromotive force potentials (reduction potentials) .............................. 2
Table 3-1: Quantities of water condition factors tested in past studies .................................. 15
Table 3-2: 2 5-1 factorial design for water chemistry factors .................................................. 17
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Table 4-1: Filtered stock solution preparation outline............................................................ 20
Table 4-2: Total organic carbon reagents ............................................................................... 25
Table 4-3: Total organic carbon instrument conditions ......................................................... 25
Table 4-4: Total organic carbon method outline .................................................................... 25
Table 5-1: Test conditions for the chlorine demand test ........................................................ 30
Table 5-2: Values of parameters k, a, e and f as calculated for Equation 5-3 and 5-4, for
various initial chlorine concentrations in the time interval 4 hr to 11 days............................ 35
Table 5-3: Test conditions for the monochloramine demand test .......................................... 36
Table 5-4: Values of parameters k, a, e and f as calculated for Equations 5-3 and 5-4 for
various initial monochloramine concentrations in the time interval 4 hours to 11 days ........ 40
Table 5-5: Test conditions to examine the influence of alkalinity and inhibitor .................... 41
Table 5-6: The average, standard deviation and variance values for chlorine residual on the
9th day ..................................................................................................................................... 43
Table 5-7: T-test results .......................................................................................................... 44
Table 5-8: Conductivity approximation based on the major ion species in the water
(equivalent conductivity of ion (λ) data from (Harned and Owen, 1964)) ........................... 48
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Table 5-9: Analysis of variance table of total lead ................................................................. 61
Table 5-10: Analysis of variance table of dissolved lead ....................................................... 77

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Table 5-11: Summary table of significant factors .................................................................. 91
Table 5-13: Performance comparison of corrosion inhibitor ................................................. 92
Table 7-1: The amount of salt needed for preparing working solutions containing different
ions ....................................................................................................................................... 102
Table 7-2: The volume of working solution needed to prepare 2 L of test water ................ 103
Table 7-3: Free chlorine residual (mg/L Cl ) measured over 11 days.................................. 117
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Table 7-4: pH of chlorine demand test measured over 11 days ........................................... 120
Table 7-5: Monochloramine residual (mg/L Cl ) measured over 11 days ........................... 121
2
Table 7-6: pH of monochloramine demand test measured over 11 days ............................. 123
Table 7-7: Galvanic current data .......................................................................................... 124
Table 7-8: Measured total lead release in the weekly composite water ............................... 125
Table 7-9: Calculated maximum lead release using Equation 2-5 ....................................... 126
Table 7-10: Measured dissolved lead release in the weekly composite water ..................... 127
Table 7-11: Electric conductivity of test water .................................................................... 128
Table 7-12: OPR of test water .............................................................................................. 129
Table 7-13: Orthophosphate residual in the weekly composite water .................................. 130
Table 7-14: Silicate residual in the weekly composite water ............................................... 131
Table 7-15: Disinfectant residual in the weekly composite water ........................................ 132
Table 7-16: The test concentrations of the test waters ......................................................... 133
Table 7-17: The actual concentrations of the test waters ..................................................... 134

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Table 7-18: Total lead concentrations (µg/L) measured by ICP-MS ................................... 135
Table 7-19: Weekly composite waters ................................................................................. 149
Table 7-20: pH and OPR ...................................................................................................... 150

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LIST OF FIGURES
Figure 1-1: Corrosion of (a) pure lead pipe (b) galvanically connected copper and lead ........ 2
Figure 4-1: Example total organic carbon calibration curve .................................................. 24
Figure 4-2: Total organic carbon quality control chart (3.0 mg/L) (July to December, 2012)
................................................................................................................................................ 24
Figure 4-3: Photo of a pipe rig set-up. .................................................................................... 28
Figure 4-4: The lead portion and copper portion are separated by an insulating spacer and
connected by an external wire ................................................................................................ 29
Figure 5-1: Free chlorine residual versus time (time = 0 to 11 day) for water samples dosed
with DOC at 0 mg/L, chlorine at 3.5 mg/L Cl . Note: the error bars represent one standard
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deviation of n=2. Some error bars were too small to see. ...................................................... 31
Figure 5-2: Free chlorine residual versus time (time = 0 to 11 day) for waters with different
levels of DOC and chlorine. Note: the error bars represent one standard deviation n =2.
Some error bars were too small to see .................................................................................... 32
Figure 5-3: Log-chlorine residual concentration versus time plots (time = 4 hr to 11 day) ... 33
Figure 5-4: Initial free chlorine concentration versus free chlorine residual concentration on
the 9th day ............................................................................................................................... 35
Figure 5-5: Monochloramine versus time (time = 0 to 11 day) for water samples dosed with
DOC at 0 mg/L, monochloramine at 6 mg/L Cl . Note: the error bars represent one standard
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deviation of n=2. Some error bars were too small to see. ...................................................... 37
Figure 5-6: Monochloramine residual versus time (time = 0 to 11 day) for waters with
different levels of DOC and monochloramine. Note: the error bars represent one standard
deviation of n=2. Some error bars were too small to see. ...................................................... 38
Figure 5-7: Log-monochloramine residual concentration versus time (time = 4 hr to 11 day)
................................................................................................................................................ 39

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