OBG PRESENTS:
Lead Corrosion: Lessons Learned and New ApproachesGeorge Rest, PE | Michelle McEntire, PE – Tifft Water Supply Symposium – September 22, 2016
Sources and Contributors to Lead
4
Faucet aerator
Galvanized piping
Lead service lines
Old fixtures (kitchen faucets, water fountains) and lead solder
Kitchen faucet aerators
(routinely clean)
Brass installed prior to 2014 (EPA Lead-Free Act reduced
allowable lead in brass from 8% to 0.25%)
Galvanized iron service lines
Galvanized iron pipe in home plumbing
Adjust the water chemistry to produce stable water quality conditions that inhibit lead release
Remove service lines and plumbing materials that contain lead
pH and alkalinity adjustment
Corrosion inhibitor(typically orthophosphate)
Traditional Lead Compliance Strategies
5
Lessoned Learned and Observations from OBG Projects and Recent Research
6
Lead compliance challenges are often the result of particulate lead
Recent research and our experience draws a strong correlation between particulate iron and particulate lead
A holistic approach requires addressing:
Classical lead solubility: pH, DIC (carbonate alkalinity), buffering capacity
Particulate iron: From unlined cast iron water mains and galvanized piping
Biological activity in distribution mains: Both an indicator and potential cause of water quality problems
Corrosion inhibitors: Orthophosphate can control dissolved and particulate lead
Optimization of Soluble Lead
7
Source: Abigail Cantor, 2014 WQTC, “Theoretical Lead and Copper Release Into Drinking Water Versus Reality”
Waters With Higher DIC Found More Stable
Lessoned Learned and Observations from OBG Projects and Recent Research
8
Lead compliance challenges are usually the result of particulate lead
Recent research and our experience draws a strong correlation between particulate iron and particulate lead
A holistic approach requires addressing:
Classical lead solubility: pH, DIC (alkalinity), buffering capacity
Particulate iron: From unlined cast iron water mains and galvanized piping
Biological activity in distribution mains: Both an indicator and potential cause of water quality problems
Corrosion inhibitors: Orthophosphate can control dissolved and particulate lead
Water System Schematic – Source to Tap
9
Source: Sheldon Masters and Marc Edwards - WQTC 2013
Correlation Between Particulate Iron and Particulate Lead
Iron from galvanized pipe and fittings
0
1000
2000
3000
4000
5000
6000
SW SW+Fe
Lead
Co
nce
ntr
atio
n (
pp
b)
pH 8.3
pH 9.7
pH 10.3
230%> 54%>
Synthetic Water Synthetic Water with Iron
Water System Schematic – Source to Tap
10
Correlation Between Iron and Lead
Source: Sheldon Masters and Marc Edwards - WQTC 2013
Lead Profiles
11
Iron and lead levels
have similar trend
0
100
200
300
400
500
600
700
800
900
1000
0
10
20
30
40
50
60
Lead
(p
pb
)
Sample Liter
Lead Profile - 3/31/2015
Total Lead Total Iron
Household Plumbing
Water Service Pipe and
Household Plumbing
Water Main, Water Service Pipe, and Household Plumbing
Iro
n
(pp
b)
High flow samples
H1: 251 ppbH2: 97 ppb
Studies conducted in
homes
Lessoned Learned and Observations from OBG Projects and Recent Research
12
Lead compliance challenges are usually the result of particulate lead
Recent research and our experience draws a strong correlation between particulate iron and particulate lead
A holistic approach requires addressing:
Classical lead solubility: pH, DIC (alkalinity), buffering capacity
Particulate iron: From unlined cast iron water mains and galvanized piping
Biological activity in distribution mains: Both an indicator and potential cause of water quality problems
Corrosion inhibitors: Orthophosphate can control dissolved and particulate lead
Benefits of Chlorine Residual
13
Source: WRF Proj. #4409
Chlorine residual also supports formation
of hard scale in lead service lines
Lessoned Learned and Observations from OBG Projects and Recent Research
15
Lead compliance challenges are usually the result of particulate lead
Recent research and our experience draws a strong correlation between particulate iron and particulate lead
A holistic approach requires addressing:
Classical lead solubility: pH, DIC (alkalinity), buffering capacity
Particulate iron: From unlined cast iron water mains and galvanized piping
Biological activity in distribution mains: Both an indicator and potential cause of water quality problems
Corrosion inhibitors: Orthophosphate can control dissolved and particulate lead
DC Water – Impact of Using Orthophosphates
16
Orthophosphates were introduced in 2004 for corrosion control
Immediate reduction in the lead level
Continued improvement since 2004
0
10
20
30
40
50
60
70
80
90
Jul 2
000
- Jun
200
1
Jul 0
1 - J
un 0
2
Jan
- Jun
03
Jul -
Dec
03
Jan
- Jun
04
Jul -
Dec
04
Jan
- Jun
05
Jul -
Dec
05
Jan
- Jun
06
Jul -
Dec
06
Jan
- Jun
07
Jul -
Dec
07
Jan
- Jun
08
Jul -
Dec
08
Jan
- Jun
09
Jul -
Dec
09
Jan
- Jun
10
Jul -
Dec
10
Jan
- Jun
11
Jul -
Dec
11
Jan
- Jun
12
Jul -
Dec
12
Jan
- Jun
13
Jul -
Dec
13
Jan
- Jun
14
Jul -
Dec
14
Jan
- Jun
15
Jul -
Dec
15
Lead
Lev
el (p
arts
per
bill
ion)
Sampling Period
Lead Results
1st Draw Sample
2nd Draw Sample
EPA Action Level = 15 ppb
A Holistic Approach is Required For Reliable Lead Control
17
Maintain a chlorine residual to minimize biofilms and
promote a strong lead scale
Optimize DIC (alkalinity) to promote stable distribution
system water quality
Flush effectively to remove biofilms and loose iron deposits
Phosphates are a widely used and effective:
Secondary barrier Effective for iron and lead Improves chlorine residual Ongoing research on use
at high pH
Why Utilities Exceed the Lead Action Level
19
Unintended Consequences
Flint, MIDesire to save $: changed source and did not feed
corrosion control agent
DC WaterIncreased
chlorine to address coliform,
then changed disinfectant to
lower DBPs
ProvidenceChange in
corrosion control strategy to reduce
lead unleashed iron
VA UtilityChanged coagulant
to lower DBPs caused high
chloride/sulfate mass ratio
NYS UtilityWithout any lead services; Added new source for
growth, changing water chemistry
20
Flint, MI
Combination of lead and iron pipes in distribution system
Detroit Water & Sewerage Department
Phosphate corrosion inhibitor used
Mineral passivation layer on pipe wall
Flint River
No corrosion inhibitor used -> passivation layer dissolves
Low pH
High chloride levels
Why Utilities Exceed the Lead Action Level
21
Unintended Consequences
Flint, MIDesire to save $: changed source and did not feed
corrosion control agent
DC WaterIncreased
chlorine to address coliform,
then changed disinfectant to
lower DBPs
ProvidenceChange in
corrosion control strategy to reduce
lead unleashed iron
VA UtilityChanged coagulant
to lower DBPs caused high
chloride/sulfate mass ratio
NYS UtilityWithout any lead services; Added new source for
growth, changing water chemistry
22
Free chlorine was increased from 2.2 to3.2 mg/L
Lead scale formed -Pb (IV) species
Mid 1990s
pH fluctuated from 7 to 8.9
pH of 7 - not optimal for corrosion control
1992 – 2004 Converted from free
chlorine to chloramines
Lead scale changed -Pb (IV) to Pb (II) species
Increase in lead released from lead service lines
2000
DC Water
Why Utilities Exceed the Lead Action Level
23
Unintended Consequences
Flint, MIDesire to save $: changed source and did not feed
corrosion control agent
DC WaterIncreased
chlorine to address coliform,
then changed disinfectant to
lower DBPs
ProvidenceChange in
corrosion control strategy to reduce
lead unleashed iron
VA UtilityChanged coagulant
to lower DBPs caused high
chloride/sulfate mass ratio
NYS UtilityWithout any lead services; Added new source for
growth, changing water chemistry
Providence History of Lead Compliance (1997 – 2005)
1996 – Treatment Optimization at pH >10
Lead Action Level = 15 ppb LCR Compliance Samples = 90th percentile
pH Adjustment to 9.7; Release of Particulate Iron and Lead
0
5
10
15
20
25
30
35
November 2005 Adjustment to pH ~ 9.7
Lead Action Level = 15 ppb
LCR Compliance Samples = 90th percentile
2006 - Action Level exceeded
0
5
10
15
20
25
30
35
Holistic Approach Has Brought PW Back Under Action Level
November 2005 Adjustment to pH ~ 9.7
Lead Action Level = 15 ppb
LCR Compliance Samples = 90th percentile
2006 - Action Level exceeded
March 2013 Adjustment to pH ~ 10.2
Why Utilities Exceed the Lead Action Level
28
Unintended Consequences
Flint, MIDesire to save $: changed source and did not feed
corrosion control agent
DC WaterIncreased
chlorine to address coliform,
then changed disinfectant to
lower DBPs
ProvidenceChange in
corrosion control strategy to reduce
lead unleashed iron
VA UtilityChanged coagulant
to lower DBPs caused high
chloride/sulfate mass ratio
NYS UtilityWithout any lead services; Added new source for
growth, changing water chemistry
Why Utilities Exceed the Lead Action Level
29
Unintended Consequences
Flint, MIDesire to save $: changed source and did not feed
corrosion control agent
DC WaterIncreased
chlorine to address coliform,
then changed disinfectant to
lower DBPs
ProvidenceChange in
corrosion control strategy to reduce
lead unleashed iron
VA UtilityChanged coagulant
to lower DBPs caused high
chloride/sulfate mass ratio
NYS UtilityWithout any lead services; Added new source for
growth, changing water chemistry
Acknowledgements
30
Abigail CantorConsultant
Marc Edwards, PhDVirginia Tech
Michael SchockUSEPA Office of Research &
Development
Providence Water
DC Water
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