1. Disinfection of seawater: Application of UV and Ozone
Ywann Penru1, Andrea R. Guastalli1,2, Santiago Esplugas1, Sylvie Baig2
1Department of Chemical Engineering, University of Barcelona, Spain. , Tel: (+34) , Fax: )
2Degrémont SA, France.
Paris, May 25, 2011, IOA-IUVA World Congress

2. Results and Discussions
Overview
Introduction
Seawater disinfection, why?
UV, Ozone and seawater chemistry
Materials and Methods
UV254 irradiation: 2 devices for 2 objectives
Ozone: a 2-step process
Analytical tools
Results and Discussions
UV254 irradiation
Ozone
Conclusions
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3. Introduction: Seawater disinfection, why?
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
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4.  Seawater ozonation leads to Bromide oxidation
Introduction: UV254, Ozone and seawater chemistry
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:
Chloride catalyser of Bromide oxidation:
Toxic and carcinogenic compounds!
 Seawater ozonation leads to Bromide oxidation
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5. 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
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6. 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: N2 O2 O3
Generator
O3 Gas
Analyzer KI
Vent
O3 dissolved
sensor P
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7.  Complete disinfection = Cellular ATP elimination
Material and methods: Analytical tools
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
Direct sample analysis:
Analysis after filtration (0.22µm):
 Total ATP measurement
 Measurement of Free ATP
 Complete disinfection = Cellular ATP elimination
Paris, May 25, 2011, IOA-IUVA World Congress
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8. 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
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9. 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 matter
A272
Aromatic organic matter without sulphide interference
A330
BrO- absorption peak (ɛ = 340 L mol-1 cm-1)
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10. 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
Initial cellular/total ATP ratio:
Ratio variation with sampling day
Mainly > 50%  high content of living cells
Cambiar grafica
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11. 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.
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12. 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
Changer graphiques
Paris, May 25, 2011, IOA-IUVA World Congress
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13. - = 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.
Changer graphiques
Respiration sample with residual oxidant
Microorganism endogenic respiration
Modified BOD7 = -
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14. UV Reduction ≠ Ozone  Increase.
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.
Changer graphiques
Paris, May 25, 2011, IOA-IUVA World Congress
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15. Disinfection of seawater: Application of UV and ozone
Changer le logo d ingeniera quimica + logo Sostaqua + logo degremont
THANKS FOR YOUR ATTENTION
Ywann Penru1, Andrea R. Guastalli1,2, Santiago Esplugas1, Sylvie Baig2
1Department of Chemical Engineering, University of Barcelona, Spain. , Tel: (+34) , Fax: )
2Degrémont SA, France.
Paris, May 25, 2011, IOA-IUVA World Congress