(Alkalinity) Waters

43 Pages·2017·5.57 MB·English

Corrosion of Distribution System Materials
in Low Dissolved Inorganic Carbon
(Alkalinity) Waters
Darren A. Lytle
U.S. Environmental Protection Agency
ORD, NRMRL, WSD
Cincinnati, Ohio 45268
[email protected]
Iron
Experimental
• 90 year old cast iron pipe section (volume,
diameter)
• Sample from center of pipe after 23.5 hours
stagnation (72 hrs)
• Measure REDOX, pH, DO, iron, metals (ICAP)

• Slowly fill with adjusted deionized water (2
liters)
• pH 8, DIC 10 and 50 mg C/L, 0 and 150 mg
SO /L, and 0 and 100 mg Cl/L
4
Iron Release
10 mg C/L 10 mg C/L
150 mg SO /L 150 mg SO /L
4 4
10 mg C/L
50 mg C/L
10 mg C/L 150 mg SO4/L 10 mg C/L 10 mg C/L 100 mg Cl/L
150 mg SO /L
3.0 4
2.5
2.0
L
/
g
m
, n
o 1.5
r
I
l
a
t
o
T
1.0
0.5
0.0
0 40 80 120 160
Elapsed Time, days
Iron Release, Cont’d (and Larson’s Index)
10 mg C/L 10 mg C/L

150 mg SO/L 150 mg SO/L

4 4
100 mg Cl/L 100 mg Cl/L 10 mg C/L

10 mg C/L 10 mg C/L 10 mg C/L
150 mg SO4/L 100 mg Cl/L 150 mg SO4/L 50 mg C/L
10 mg C/L 50 mg C/L 100 mg Cl/L
10 mg C/L 10 mg Cl/L 50 mg C/L 100 mg Cl/L 150 mg SO4/L
3.0 8
7
2.5
6
L 2.0 x
g/ 5 de
m n
I
on, 1.5 4 n's
r o
I s
al ar
t L
o 3
T
1.0
2
0.5
1
0.0 0
240 280 320 360 400 440 480 520 560 600

Elapsed Time, days
Iron Release Stagnation Profile
3.0
10 mg C/L, 100 mg Cl/L
10 mg C/L, 150 mg SO/L, 100 mg Cl/L
4
10 mg C/L, 150 mg SO/L
2.5 4

L 10 mg C/L
/
g 50 mg C/L
m
50 mg C/L, 150 mg SO/L
, 4
n 2.0 50 mg C/L, 150 mg SO/L, 100 mg Cl/L
o 4
i
t
a
r
t
n
e
c 1.5
n
o
C

n
o
1.0
r
I

l
a
t
o
T
0.5
0.0
0 10 20 30 40 50 60 70
80
Standtime, hours
The Effect of Chloride and Orthophosphate

on Iron Release
4

0 mg/L ­
100 mg/L Cl
­ ­ ­ ­
Cl 100 mg/L Cl 100 mg/L Cl 0 mg/L Cl
3 mg PO4/L
3

L
/
g
m

,
n
o 2

r
i

l
a
t
o
T
1

1- day stand
0
0 20 40 60 80 100 120 140 160 180 200 220

Elapsed time, days
The Effect of Chloride and

Orthophosphate on Turbidity
25

0 mg/L ­
100 mg/L Cl
­ ­ ­ ­
Cl 100 mg/L Cl 100 mg/L Cl 0 mg/L Cl
3 mg PO4/L
20

t
i
n
u

U
15

T
N

,
y
t
i
d 10

i
b
r
u
T
5

1- day stand
0
0 20 40 60 80 100 120 140 160 180 200 220

Elapsed time, days
Key Iron Observations
• Chloride and sulfate increased RATE of iron release
(23.5 hour samples)
 Diffusion, corrosion, dissolution rate?
• Chloride and sulfate impact was NOT additive
• Sulfate did not impact final iron release levels following
long stagnation times; chloride had little impact (ie.,
iron level did not appear to be impacted)
• DIC countered impact of chloride and sulfate
• DIC appeared to reduce iron solubility (impacted the
nature of the iron minerals within the pipe scale)
• Orthophosphate reduced iron release and associated
turbidity
Copper Pitting