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. (penru@angel.qui.ub.es , Tel: (+34) 934 021 293, Fax: +34 934 021 291) 2Degrémont SA, France. Paris, May 25, 2011, IOA-IUVA World Congress

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 Paris, May 25, 2011, IOA-IUVA World Congress 1 / 13

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 Paris, May 25, 2011, IOA-IUVA World Congress 2 / 13

 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: 1.5 10-3 Chloride catalyser of Bromide oxidation: Toxic and carcinogenic compounds!  Seawater ozonation leads to Bromide oxidation 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: N2 O2 O3 Generator O3 Gas Analyzer KI Vent O3 dissolved sensor P Paris, May 25, 2011, IOA-IUVA World Congress 5 / 13

 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 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 matter A272 Aromatic organic matter without sulphide interference A330 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 Initial cellular/total ATP ratio: Ratio variation with sampling day Mainly > 50%  high content of living cells Cambiar grafica 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. 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 Changer graphiques Paris, May 25, 2011, IOA-IUVA World Congress 11 / 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 = - Paris, May 25, 2011, IOA-IUVA World Congress 12 / 13

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 13 / 13

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. (penru@angel.qui.ub.es , Tel: (+34) 934 021 293, Fax: +34 934 021 291) 2Degrémont SA, France. Paris, May 25, 2011, IOA-IUVA World Congress