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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
6Drinking Water Treatment
Regulations
European requirements:
“Water should not be aggressive“
!Binding for all members of the European Community!
8Drinking Water Treatment
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
10Drinking Water Treatment
Theoretical Basics
Titration with NaOH to pH = 4,3 → HCO3- (bicarbonate)
Titration with HCl to pH = 8,2 → CO2 (carbon dioxide)
11Drinking Water Treatment
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-)
12Drinking Water Treatment
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
13Drinking Water Treatment
Theoretical Basics
Descriptions of the Deviation of the Equilibrium (Selection)
SI: Saturation Index: pH - pHL
metered value
14Drinking Water Treatment
Theoretical Basics
CO2
aggressive: CO2 – CO2
equil
metered value
SI: Saturation Index: pH - pHL
Descriptions of the Deviation of the Equilibrium (Selection)
15Drinking Water Treatment
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)
17Drinking Water Treatment
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
18Drinking Water Treatment
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
19Drinking Water Treatment
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
21Drinking Water Treatment
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
23Drinking Water Treatment
Contents
1. Problem, Regulations
2. Theoretical Basics
3. Deacidification Methods
4. The Aquadosil® -System (fine bubbles …)
27Drinking Water Treatment
Aquadosil®-System: flat construction
WiesbadenFeed [m³/h]: 500
CO2 [mg/l]: 38 < 2
28Drinking Water Treatment
Aquadosil®-System: easily retrofitted
DüsseldorfFeed [m³/h]: 1000
CO2 [mg/l]: 20 5
29Drinking Water Treatment
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 !
30Drinking Water Treatment
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
33Drinking Water Treatment
• 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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