George Rest PE Michelle McEntire PE Tifft Water Supply Symposium September 22 2016 AGENDA Basics of Lead in Drinking Water Reasons Behind Lead NonCompliance Questions 2 3 Basics of Lead in Drinking Water ID: 594095
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Slide1
Lead Corrosion: Lessons Learned and New Approaches
George Rest, PE | Michelle McEntire, PE – Tifft Water Supply Symposium – September 22, 2016Slide2
AGENDA
Basics of Lead in Drinking Water
Reasons Behind Lead Non-Compliance
Questions
2Slide3
3
Basics of Lead in Drinking Water
Slide4
Sources and Contributors
to
Lead
4
Faucet aeratorGalvanized 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 plumbingSlide5
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
5Slide6
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
c
apacity
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
Slide7
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 StableSlide8
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 Slide9
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 fittingsSlide10
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 2013Slide11
Lead Profiles
11
Iron and lead levels
have similar trend
Studies conducted in homesSlide12
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 Slide13
Benefits of Chlorine Residual
13
Source: WRF
Proj
. #4409
Chlorine residual
also supports formation of hard scale in
lead service linesSlide14
Impacts of Biofilms
14Slide15
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 Slide16
DC Water – Impact of Using Orthophosphates
16
Orthophosphates were introduced in 2004 for corrosion
control
Immediate reduction in the lead level Continued improvement since 2004Slide17
A Holistic Approach is Required For Reliable Lead Control
17
Maintain a chlorine residual
to minimize biofilms and
promote a strong lead scaleOptimize 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 barrierEffective for iron and lead
Improves chlorine residualOngoing research on use at high pHSlide18
18
The Reasons Behind Lead
Non-ComplianceSlide19
Why Utilities Exceed the Lead Action Level
19Slide20
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 Slide21
Why Utilities Exceed the Lead Action Level
21Slide22
22
Free chlorine was increased from 2.2 to
3.2 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 WaterSlide23
Why Utilities Exceed the Lead Action Level
23Slide24
Providence
History of Lead Compliance
(1997 – 2005)
1996
– Treatment Optimization at pH >10Lead Action Level = 15 ppb
LCR Compliance Samples = 90
th percentileSlide25
pH versus Theoretical Lead Solubility Slide26
pH Adjustment to 9.7; Release of Particulate Iron and Lead
November 2005 Adjustment to pH ~ 9.7
Lead Action Level = 15 ppb
LCR Compliance Samples = 90
th
percentile
2006 - Action Level exceededSlide27
Holistic Approach Has Brought PW Back Under Action Level
November 2005 Adjustment to pH ~ 9.7
Lead Action Level = 15 ppb
LCR Compliance Samples = 90
th
percentile
2006 - Action Level exceeded
March 2013 Adjustment to pH ~ 10.2Slide28
Why Utilities Exceed the Lead Action Level
28Slide29
Why Utilities Exceed the Lead Action Level
29Slide30
Acknowledgements
30
Abigail
Cantor
Consultant Marc Edwards, PhDVirginia Tech Michael Schock
USEPA Office of Research & Development
Providence WaterDC Water Slide31
Questions?
George.Rest@obg.com - (301) 731-1162 | Michelle.McEntire@obg.com - (585) 295-7713