TZW Karlsruhe Prüfstelle Wasser The Influence of Water Treatment on Corrosion of Materials in...

TZW Karlsruhe Prüfstelle Wasser

The Influence of Water Treatment

on Corrosion of Materials in Service

Lines

and Drinking Water Installations

Josef Klinger

TZW Karlsruhe



Why to change the Water Treatment?

Water quality problems

New raw water resources

Merger of small water utilities

Corrosion problems – desalination

Consumer complaints – central softening


Central Softening

Precipitation (NaOH, Ca(OH)2)

Addition of acids (cooling water)

Ion exchange

Membrane filtration (nanofiltration, reverse osmosis)


Membrane Filtration


Reverse Osmosis

1 Feed 3 Feed spacer 5 Membrane 7 Permeate header2 Permeate 4 Concentrate 6 Permeate spacer 8 Sealing to pressure pipe


Example out of the Practice

Raw water quality

Groundwater

Winter m³/d 500

Summer m³/d 4.000

Conductivity mS/m 165

pH - 7,3

KS4,3 mmol/L 5,1

Hardness °dH 26

Chloride mg/L 325

Sulfate mg/L 70

Arsenic mg/L 0,010

Selenium mg/L 0,030

Hardness

Corrosion

Limit value


Pilot Study for Water Treatment

Version A

Mixture of desalinated water and aeration

Version B

100 % RO and stabilisation of desalinated water with CaCO3


Parameters of the Test Waters in the Pilot Plant

El. ConductivitypH

Alkalinity (pH: 4.3)Acidity (pH: 8.2)

Ca2+ 2++ MgNa+

Cl-

SO42-

NO3-

PO43- (total)

SiDOC

S1

mS/m

mmol/Lmmol/Lmmol/L

mg/Lmg/Lmg/Lmg/Lmg/L

mg/L Simg/L C

Tap Waterwith Inhibitor

148 -1647.3 - 7.4

5.10.64.713031070301.2

50.6 - 1,8

2

SoftenedTap Water

55 - 597.6 - 7.9

1.60.051.645

1002010

0.012

0.42

RO Filtrate afterCaCO3 Filtration

13 - 188.2 - 8.5

1.20.020.6

63

< 12

0.010.1

0.2 - 0,4<< 1

Parameter Unit Test Water 1 Test Water 2 Test Water 3

Tap:30%, RO:70%


Closed Loop Device

for Corrosion Tests with Iron Pipes

Pump

Test PipeFlowMeter

CoolingSystem

Effluent Stopcock

Cooler

Valve

Fresh Water Effluent

T O2

pH

SamplingPoint, V2

V


Corrosion and Iron Migration Rates

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

4.5

5.0

Cor

rosi

on

Ra

te[g

/md

]Fe

2

0 50 100 150 200 250

Running Time [d]

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

Mig

ratio

nR

ate

[g/m

d]F

e2

0 50 100 150 200 250

Running Time [d]

a) b)

Testwater 1Testwater 2Testwater 3


Mechanical Stability and Iron Migration Rates

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

Mig

ratio

nR

ate

[g/m

d]F

e2

0 50 100 150 200 250

Running Time [d]

b)

Testwater 1Testwater 2Testwater 3

0

20

40

60

80

100

120

Sta

bilit

yP

aram

eter

[g/m

²d]

Fe

0 50 100 150 200 250

Running Time [d]

c)


Corrosion Rates with changed Water Quality


Example of a „Turner Diagram“

0

50

100

150

200

Chl

orid

eC

once

ntra

tion

[mg/

L]

300

0 1 2 3 4 5 6

Carbonate Hardness [mol/m ]3

No Dezincification

Borderlinefor MS 58

Borderline for CR Brass

Testwater 1: 310 m/L Cl

Testwater 3 Source: Seppelfricke

Testwater 2


Metallurgical Structure of Duplex Brass

CuZn39Pb3 (Wieland Z33)Source: Wieland-Werke AG


Metallographical Grindings of the test pieces

Running Time: 220 Days

200 µmCuZn40Pb2 Testwater 1




Tempered Brass Material: CuZn40Pb2Running Time: 220 DaysTest Water 3(100 % RO + stabilisation) 200 µmb) CuZn40Pb2(t) Testwater 3

111 µm

Tempered Brass Material: CuZn40Pb2Running Time: 220 DaysTest Water 1Tap Water with Inhibitor

200 µma) CuZn40Pb2(t) Testwater 1

422 µm

Metallographic Sections of the test pieces


The new Treatment Plant


Summary

The influence of a changed water quality on corrosion processes was assessed in a pilot plant

Corrosion assessment tools are available

Treatment plant is in service since two years

Corrosion processes are controlled as predicted

Prediction based on pilot plant tests were successful

Date post:	27-Mar-2015
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TZW Karlsruhe Prüfstelle Wasser The Influence of Water Treatment on Corrosion of Materials in...

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