lead and copper corrosion 101: principles & guidance
TRANSCRIPT
Lead and Copper Corrosion 101 Principles amp Guidance
2
Darren A LytleEnvironmental Engineer
US Environmental Protection Agency
Rationale
bull The viewer will learn about the fundamental basics of lead and copper solubility and factors that impact levels in drinking water
bull The information presented during this webinar will help the viewer in making better decisions regarding lead and copper control in drinking water distribution systems
3
Learning Objectives
The viewers will obtainbull An understanding of basic relationships between lead and copper
concentrations and important water quality parameters in drinking water
bull An understanding of the importance of corrosion by-products and scale properties on lead and copper release
bull A basis for developing lead and copper corrosion control strategies bull Information to be better prepared to make decisions regarding lead
and copper issues
4
Acknowledgments
bull Micheal Schock USEPAbull Christy Muhlen USEPA
Disclaimer
5
This presentation has been reviewed in accordance with US Environmental Protection Agency (EPA) policy and approved for external presentation The views expressed are those of the author[s] and do not necessarily represent the views or policies of EPA
Agenda
bull Major Factors that Impact Copper (Cu) Release
- Oxidation-reduction potential (ORP)persistence of oxidants
- pHAlkalinityDissolved inorganic concentration (DIC) = solubility
- Aging (several variables)
- [Ortho]phosphate
- Stagnation time
bull Chlorine demand and copper corrosion
bull Pitting corrosion
6
ORP-pH Effects on Copper in WaterCu species = 13 mgL DIC = 96 mg CL
I=0 25oslashC
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14-150
-100
-050
000
050
100
150
E (
volts
vs
SHE)
CO2- 3
HCO 3
-
HCO 3
-
H CO
32
H
Cu(s)
Cu 2+
Cu O(s)2
Cu(OH) 3-
CuCO
3o Cu(OH) (s)2
Vulnerable to ORP or pH change
Copper Oxidation StateCu1+ or Cu(I)Cu2+ or Cu(II)
pH
Copper(II) Solubility at Different DIC Levels Compared to Copper(I) Solubility
pH6 7 8 9 10
mg Cu
L
0001
0010
0100
1000
10000
100000 48 mg Cl144 mg CL 96 mg CL
]Cu2O (s)
Cu(OH) (s)
Cu(I) solids
Cu(II) solids are several orders of magnitude moresoluble than Cu(I) solids
Cu(II) solids
Age Impacts Oxidant-Limited Cu Stagnation
Stagnation t ime hours0 10 20 30 40 50 60 70 80 90
0
1
2
3
4
5
6
7Cu 161-184 days
DO 161-184 daysCu 455-462 days
DO 455-462 days
Dissolved oxygen
Copper
Loss of oxygen (drop in ORP) during stagnation impacts Cu(II) and Cu(I) stability
Evolution of Scale Model for High DIC Low pH WatersCopper ldquoAgingrdquo
pH60 70 80
mg
CuL
0 01
01
1
10
100
Ideal Cu2(OH)2CO3 Film
Cu(OH)2 Fresh Scale
AgingReDeReCa
ye
CuO
Process (in theory)crystallizingcreasing surface areaacting with CO3 or HCO3
-
n take 20 30 or morears with high DIC
Impact of Plumbing Age on 2nd Draw Copper Concentrations
Year of Pipe vs Copper Level without questioned data points
0
500
1000
1500
2000
2500
3000
3500
1960 1965 1970 1975 1980 1985 1990 1995 2000 2005
Year of Pipe
Copp
er L
evel
(ug
L) 2ndDrawSample
Linear(2ndDrawSample)
Slope of the line is ~ -52 ugLyear
Data from MS Thesis of N Turek ldquoInvestigation of Copper Contamination and Corrosion Scale Mineralogy in Aging Drinking Water Distribution Systemsrdquo AFIT 2006