1Drinking Water Treatment

Lyon, Pollutec 2008

Fine Bubbles, Big Effect

Deacidification of Drinking Water

Dr. Andreas Dülberg

2Drinking Water Treatment

Market Leader in Germany

Over 400 installations

flow-rates between 5 and 5000 m³/h

3Drinking Water Treatment

Cooperation

Aquadosil®

Essen

Germany

Andreas Dülberg

CIFEC

Neully s. Seine

France

Luc Derreumaux

Cooperation

4Drinking Water Treatment

Contents

1. Problem, Regulations

2. Theoretical Basics

3. Deacidification Methods

4. The Aquadosil® System (fine bubbles …)

5Drinking Water Treatment

Problem

• Heavy Metal Incorporation Copper (Cu), Zinc (Zn), Lead (Pb)

• ‘Redwater’ (Rusty Water), Turbidity

• Microbiology

• Loss of Water Due to Leaks

• Damage of Pipes And Indoor Installations

Corrosion

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Regulations

European requirements:

“Water should not be aggressive“

!Binding for all members of the European Community!

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Regulations

pH corrosion

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Contents

1. Problem, Regulations

2. Theoretical Basics

3. Deacidification Methods

4. The Aquadosil® System (fine bubbles …)

9Drinking Water Treatment

Theoretical Basics

1) CO2 + H2O ↔ H2CO3 k0 = 1 x 10-5

2) H2CO3 ↔ H+ + HCO3- k1 = 5 x 10-7

3) HCO3- ↔ H+ + CO3

2- k2 = 5 x 10-11

4) H2O ↔ H+ + OH- k3 = 1 x 10-14

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Theoretical Basics

Titration with NaOH to pH = 4,3 → HCO3- (bicarbonate)

Titration with HCl to pH = 8,2 → CO2 (carbon dioxide)

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Theoretical Basics

?How does Calcite come into play?

Computation of the equilibrium values with iterative procedures

5) (CaCO3)solid ↔ Ca2+ + CO32- kL = 4.8 x 10-9

6) CaCO3 + CO2 + H2O ↔ Ca2+ + 2(HCO3-)

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Theoretical Basics

Parameters related to calcite / carbonic acid equilibrium

pHL: Equlibrium by removal of CO2 from aggressive water

pHC: Equlibrium by adding of calcite to aggressive water

CO2

equil: equilibrium value

computed values of water data

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Theoretical Basics

Descriptions of the Deviation of the Equilibrium (Selection)

SI: Saturation Index: pH - pHL

metered value

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Theoretical Basics

CO2

aggressive: CO2 – CO2

equil

metered value

SI: Saturation Index: pH - pHL

Descriptions of the Deviation of the Equilibrium (Selection)

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Theoretical Basics

Descriptions of the Deviation of the Equilibrium (Selection)

Dc: theoretical ability of a water, to dissolve calcite (in mg/l)

So, what does it mean: “… should not be aggressive“?

computed values of water data

SI: Saturation Index: pH - pHL

CO2

aggressive: CO2 – CO2

equil

16Drinking Water Treatment

Theoretical Basics

… should not be aggressive …

has led to the following regulations:

in Germany: Dc ≤ 5 mg/l

in France: SI: ≥ 0 (pH ≥ pHL)

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Theoretical Basics

Water A (soft) Water B (hard)measured valuespH [-] 7,0 7,0

HCO3- [mmol/l] 1,7 5,7

Calcium [mg/l] 40 102

Hardness [ofH] 14 30CO2 [mg/l] 19 59

computed valuespHL [-] 8,0 7,2

DC [mg/l] 33 19

CO2 equilib

[mg/l] 1,7 41

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Theoretical Basics

0

5

10

15

20

25

30

35

40

45

50

55

60

6,8 6,9 7,0 7,1 7,2 7,3 7,4 7,5 7,6 7,7 7,8 7,9 8,0

pH

CO

2 [m

g/l]

Water 'A'; HCO3 = 1,7 mmol/l

Water 'B'; HCO3 = 5,7 mmol/l

hard

soft

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Contents

1. Problem, Regulations

2. Theoretical Basics

3. Deacidification Methods

4. The Aquadosil® -System (fine bubbles …)

20Drinking Water Treatment

3) Deacidification Methods

1. Neutralisation with chemicalsCO2 + NaOH NaHCO3

2. Filtration (marble or neutralite)

CO2 + CaCO3 + H2O Ca(HCO3)2

3. Stripping (removal of CO2 by air)

H2CO3 CO2 + H2O

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Deacidification Methods Stripping

a) Thermodynamics

Distribution Equlibrium:

Cwater = KHenry x Cair x P

concentrations

Henry‘s constant

pressure

Cwater (min) = 0,7 mg/l (10 oC)

with infinite amounts of air

22Drinking Water Treatment

Methods for Deacidification Stripping

b) Kinetics

diffusion-controlled reaction:

dCwater/dt = A/Z x D x (ΔCwater)

flow

thickness of the reaction layer

exchange surface

concentration gradient

diffusion coefficient

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Contents

1. Problem, Regulations

2. Theoretical Basics

3. Deacidification Methods

4. The Aquadosil® -System (fine bubbles …)

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Stripping Aquadosil®-System

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Aquadosil®-System: fine bubbles

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Aquadosil®-System: fine bubbles

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Aquadosil®-System: flat construction

WiesbadenFeed [m³/h]: 500

CO2 [mg/l]: 38 < 2

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Aquadosil®-System: easily retrofitted

DüsseldorfFeed [m³/h]: 1000

CO2 [mg/l]: 20 5

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Aquadosil® -System: high performance

Wiesbaden

Progress of CO2-Removal

02468

10121416182022242628303234363840

0 10 20 30 40 50 60 70 80 90 100Distance [%]

CO

2Cle

anw

ater [

mg/

l]

2 mg/l !

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Aquadosil® -System: high performance

Bicarbonate[mmol/l]

Calcium[mg/l]

Hardness[ofH]

pH[ - ]

Dc

[mg/l]SI

[ - ]

≥ 2,0 40 10 8,2 (equi) 0 0

≥ 1,5 30 7,5 ≥ 7,9 ≤ 2,5 ≥ -0,2

≥ 1,0 20 5 ≥ 7,7 ≤ 5 ≥ -0,7

pH values after physical deacidification CO2 concentration ≤ 2 mg/l:

cleanwater

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Aquadosil® -System: adjustable

BaselFeed [m³/h]: 2000

CO2 [mg/l]: 20 < 2

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Aquadosil® -System: adjustable

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• fine bubbles - high efficiency; CO2 cleanwater < 2 mg/l ! - adjustable

• flat construction - easily retrofitted

• inert sinter ceramic aeration elements - mechanically and chemically stable

- no microbiological growth- low-maintenance operation

Aquadosil® -System: Summary

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fin

Merci beaucoup pour votre attention!