ywann penru 1, andrea r. guastalli 1,2, santiago esplugas 1, sylvie baig 2 1 department of chemical...
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Ywann Penru1, Andrea R. Guastalli1,2, Santiago Esplugas1, Sylvie Baig2
1Department of Chemical Engineering, University of Barcelona, Spain. (penru@angel.qui.ub.es , Tel: (+34) 934 021 293, Fax: +34 934 021 291)
2Degrémont SA, France.
Disinfection of seawater:
Application of UV and Ozone
Paris, May 25, 2011, IOA-IUVA World Congress
1 / 13
Overview
I. Introduction
• Seawater disinfection, why?
• UV, Ozone and seawater chemistry
II. Materials and Methods
• UV254 irradiation: 2 devices for 2 objectives
• Ozone: a 2-step process
• Analytical tools
III. Results and Discussions
• UV254 irradiation
• Ozone
IV. Conclusions
Paris, May 25, 2011, IOA-IUVA World Congress
Introduction: Seawater disinfection, why?
Paris, May 25, 2011, IOA-IUVA World Congress
Nowadays, seawater disinfection is an issue in several areas:
• Ballast water: Prevention from the spread of harmful aquatic organisms carried by
ships' ballast water (International Maritime Organization, 2004).
• Marine recirculation aquaculture systems and seawater aquaria:
Prevention from microorganisms and viruses accumulation,
Prevention from organic and inorganic by-products accumulation.
Application of new technologies for seawater disinfection:
Ozone
UV254 irradiation
Membrane filtration
Acoustics or electric pulses
2 / 13
• Seawater, a peculiar chemistry:
High salt content Scaling formation on Quartz sleeves.
High Bromide and Chloride concentration: ≈ 64 mg/L and 19 g/L
• Bromide and Chloride reactivity:
Catalytic consumption of Ozone by Bromide
Hypobromous acid and bromate formation
Analogous reaction with chloride but kinetic constants much lower
• Seawater reactivity:
Seawater Bromide/Chloride ratio: 1.5 10-3
Chloride catalyser of Bromide oxidation:
Introduction: UV254, Ozone and seawater chemistry
BrOOBrO k23
1
BrOBrOO k23
2
323 22 3 BrOOBrOO k
4
2 3
kH O HOBr H O BrO
8kHOCl Br HOBr Cl
Seawater ozonation leads to Bromide oxidation
Toxic and carcinogenic compounds!
Paris, May 25, 2011, IOA-IUVA World Congress 3 / 13
Material and methods: UV254 irradiation, 2 devices for 2 objectives
• 1st Objective: Minimum UV254 dose requirement for total disinfection. Laboratory batch reactor.
2 L cylindrical glass reactor recovered by aluminium foil
3 submerged Hg-low pressure lamps
Photon flow = 9.0 µEinstein.s-1
UV doses applied: 0 – 500 J.L -1
• 2nd Objective: Impact of UV254 disinfection on organic matter.
Pilot reactor in continuous operation.
1.1 L tubular UV705 Trojan reactor
One central Hg-low pressure lamp
Photon flow = 34.2 µEinstein.s-1
Continuous feeding at 200 L.h-1
UV dose applied: 320 J.L-1
Seawater tank
UV reactor
Paris, May 25, 2011, IOA-IUVA World Congress 4 / 13
Material and methods: Ozone, a 2-step process
• Method:
1st Step: Ozone dose production
Reach Henry’s law equilibrium:
2nd Step: the disinfection reaction
Addition to seawater of the solution saturated with ozone.
• Materials:
Ozone generator unit: Ozat CFS, Ozonia
Ozone gaseous-phase analyser: BMT 693
Ozone dissolved sensor: ATI Q45H/64
• Experimental conditions:
ge3O2H
O2H*l3 O
He
TR
M
ρ][O
[O3]ge g O3/Nm3 13 26 40 88 136 170
[O3]l* mg O3/L 4.1 8.0 12.5 27.4 42.2 53.8
Ozone dose applied
mg O3/L 0.38 0.73 1.14 2.49 3.84 4.89
Paris, May 25, 2011, IOA-IUVA World Congress 5 / 13
N2
O2
O3 Generator
O3 Gas Analyzer
KI
Vent
O3 dissolvedsensor
P
• Disinfection quantification: Adenosine Tri-Phosphate (ATP) liberation
ATP: Bio-molecule present in all microorganisms involved in the energy generation
process.
Calculation:
Cellular ATP = Total ATP – Free ATP
Material and methods: Analytical tools
Direct sample analysis:
Total ATP measurement
Analysis after filtration (0.22µm):
Measurement of Free ATP
Complete disinfection = Cellular ATP elimination
Paris, May 25, 2011, IOA-IUVA World Congress 6 / 13
Material and methods: Analytical tools
• Oxidant / Oxidation potential
Oxidation Reduction Potential (ORP):
Total Residual Oxidant (TRO):
Quantification of total BrOH / BrO- (in mg Br2.L-1)
DPD colorimetric method
Bromate and Chlorate
Ionic chromatography
Dilution 1/10
Detection limit:
BrO3- = 10 µg.L-1
ClO3- = 200 µg.L-1
Paris, May 25, 2011, IOA-IUVA World Congress 7 / 13
Material and methods: Analytical tools
• Organic matter parameters
Total Organic Carbon (TOC)
High-temperature catalytic oxidation
UV absorbance at different wavelength (Aʎ)
Biochemical Oxygen Demand at seven days (BOD7)
Closed Bottle Method: BOD7 = [O2]day 0 - [O2]day 7
Autochthonous microorganisms
Residual oxidant quenching by sulphite
Modified BOD7:
No quenching of residual oxidant
A254 Aromatic organic matterA272 Aromatic organic matter without sulphide interferenceA330 BrO- absorption peak (ɛ = 340 L mol-1 cm-1)
Paris, May 25, 2011, IOA-IUVA World Congress 8 / 13
Results and discussions: UV254 irradiation
• Disinfection: Minimum UV254 dose required
UV254 irradiation decreases the cellular/total ATP ratio:
Elimination of cellular ATP Seawater disinfected
Minimum UV dose for complete disinfection = 320 J.L-1
0
20
40
60
80
100
0 80 160 240 320 400
rati
o of
Cel
lula
l ATP
/ to
tal A
TP (
%)
UV Dose applied per litre of seawater (J/L)
Exp n°1
Exp n°2
Exp n°3
Exp n°4
Exp n°5
Initial cellular/total ATP ratio:
Ratio variation with sampling day
Mainly > 50% high content of living cells
Paris, May 25, 2011, IOA-IUVA World Congress 9 / 13
Results and discussions: UV254 irradiation
• Organic matter parameters: UV254 dose applied = 320 J.L-1
UV254 irradiation interacts with seawater organic matter:
Low reduction of UV absorbance, TOC and BOD7
Low reduction of seawater aromaticity and biodegradability
Low interaction with organic matter
Radiation is mainly used for disinfection.
A254 TOC BOD7 SUVA254 BOD7/TOC
m-1 mg C.L-1 mg O2.L-1 L.mg C-1.m-1 mg O2.mg C-1
Seawater 0.64 0.97 0.71 0.66 0.73
UV treated 0.57 0.93 0.66 0.61 0.71
Removal (%) 11.7 4.2 7.0 7.8 3.0
Paris, May 25, 2011, IOA-IUVA World Congress 10 / 13
Results and Discussions: Ozone application• Disinfection: Minimum ozone dose required
• Oxidant formation
Complete disinfection by ozone
Minimum O3 dose:
Cellular ATP removal: 0.4 mg O3.L-1.
Total ATP removal: 1.1 mg O3.L-1.
Very fast dissolved O3 consumption
High ORP increases (> 700 mV)
Highly oxidative water
No proportional relation with O3 dose.
Formation of residual oxidant:
Proportional to O3 dose.
No bromate nor chlorate formation
Paris, May 25, 2011, IOA-IUVA World Congress 11 / 13
0 1 2 3 4 50
2,000
4,000
6,000
8,000
10,000
ATP Total
ATP cell
Ozone dose applied (mg O3.L-1)
AT
P (
RL
U)
0 1 2 3 4 50
200
400
600
800
0
4
8
12
16
20
ORP TRO measured TRO maximum
Ozone dose applied (mg O3.L-1)
OR
P (
mV
)
TR
O (
mg
Br2
.L-1
)
Results and Discussions: Ozone application• Organic matter:
Organic matter oxidation by ozone
UV absorbance removal up to 50%
Low mineralization, max: 10%.
BOD7 increases
Residual oxidants modify the activity of autochthonous microorganisms.
Modified BOD7 < conventional BOD7
Negative values for Modified BOD7
Potential use for microorganism inhibition in seawater.
Microorganism endogenic respiration
Modified BOD7 =
Respiration sample with
residual oxidant-
Paris, May 25, 2011, IOA-IUVA World Congress 12 / 13
0 1 2 3 4 50
10
20
30
40
50
60A 254 A 272 TOC
Ozone dose applied (mg O3.L-1)
Rem
oval
of a
bsor
banc
e an
d TO
C (%
)
0 1 2 3 4 5
-1.5
-1.0
-0.5
0.0
0.5
1.0
1.5
2.0
BOD7BOD7 modified
Ozone dose applied (mg O3.L-1)
BOD7
(mg
O2.
L-1)
13 / 13
Conclusions• Complete seawater disinfection obtained for both processes
Minimum dose: UV254 = 320 J.L-1, O3 = 0.4 mg O3.L-1
Ozonation leads to the formation of secondary oxidant :
Long term inhibition of autochthonous microorganisms.
No bromate formation (for the applied doses).
Interesting properties for ballast water treatment.
Post-treatment required after ozone application for aquaculture purposes (protection from toxic residual oxidant).
• Partial degradation of seawater organic matter by UV254 and ozone
Higher removals by ozone (up to 50% vs. 10% for A254).
Low mineralization in both cases (3 vs. 10%).
Opposite effect on biodegradability:
UV Reduction ≠ Ozone Increase.
Paris, May 25, 2011, IOA-IUVA World Congress
Ywann Penru1, Andrea R. Guastalli1,2, Santiago Esplugas1, Sylvie Baig2
1Department of Chemical Engineering, University of Barcelona, Spain. (penru@angel.qui.ub.es , Tel: (+34) 934 021 293, Fax: +34 934 021 291)
2Degrémont SA, France.
Disinfection of seawater:
Application of UV and ozone
THANKS FOR YOUR ATTENTION
Paris, May 25, 2011, IOA-IUVA World Congress
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