Lead Corrosion: Lessons Learned and New Approachesnysawwa.org/docs/pdfs/1474902762.pdfLead Corrosion: Lessons Learned and New Approaches George Rest, PE | Michelle McEntire, PE –Tifft

OBG PRESENTS:

Lead Corrosion: Lessons Learned and New ApproachesGeorge Rest, PE | Michelle McEntire, PE – Tifft Water Supply Symposium – September 22, 2016

http://www.obg.com/

AGENDABasics of Lead in Drinking Water

Reasons Behind Lead Non-Compliance

Questions

2

3

BASICS OF LEAD IN DRINKING WATER

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


8

Lead compliance challenges are usually the result of particulate lead



Classical lead solubility: pH, DIC (alkalinity), buffering capacity




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

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50

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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


12








Benefits of Chlorine Residual

13

Source: WRF Proj. #4409

Chlorine residual also supports formation

of hard scale in lead service lines

Impacts of Biofilms

14


15








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

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80

90

Jul 2

000

- Jun

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1

Jul 0

1 - J

un 0

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- Jun

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Jul -

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Jul -

Dec

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Jan

- Jun

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Jul -

Dec

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Jul -

Dec

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Jul -

Dec

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Jul -

Dec

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Jul -

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Jul -

Dec

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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

18

THE REASONS BEHIND LEAD NON-COMPLIANCE

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


21




DC WaterIncreased



lower DBPs

ProvidenceChange in


lead unleashed iron






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


23




DC WaterIncreased



lower DBPs

ProvidenceChange in


lead unleashed iron






Providence History of Lead Compliance (1997 – 2005)

1996 – Treatment Optimization at pH >10

Lead Action Level = 15 ppb LCR Compliance Samples = 90th percentile

pH versus Theoretical Lead Solubility

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


28




DC WaterIncreased



lower DBPs

ProvidenceChange in


lead unleashed iron







29




DC WaterIncreased



lower DBPs

ProvidenceChange in


lead unleashed iron






Acknowledgements

30

Abigail CantorConsultant

Marc Edwards, PhDVirginia Tech

Michael SchockUSEPA Office of Research &

Development

Providence Water

DC Water

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Documents

Lead Corrosion: Lessons Learned and New Approachesnysawwa.org/docs/pdfs/1474902762.pdfLead Corrosion: Lessons Learned and New Approaches George Rest, PE | Michelle McEntire, PE –Tifft