What is Chlorine Dioxide and Why You Should Learn About It Now?

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1 What is Chlorine Dioxide and Why You Should Learn About It Now? Ken Gibson and Dustin Kauffman World Aquatic Health Conference Charleston, SC October 11 th, 2018 Topics of the Day Chlorine dioxide What is it? How does it work? Different ways to generate chlorine dioxide Common applications of chlorine dioxide in other industries Potential applications of chlorine dioxide in recreational aquatics venues 9/25/ Properties of Chlorine Dioxide O Cl O O Cl O Unpaired electron, considered to be a free radical: high reactivity for oxidation and disinfection ClO 2 + e - ClO - 2 (Chlorite) E 0 = 0.95 V Soluble in water as a gas - reactivity independent of ph - able to penetrate cellular membranes - able to kill and remove biofilm Much smaller molecule than chlorine 9/25/

2 Physical Properties of Chlorine Dioxide Yellow-green gas, cannot be stored or compressed, has to be freshly produced Soluble in water as a gas, off-gassing at: increasing temperature solution s agitation Aqueous solution is stable for a few days Solubility affected by water temperature Detect odor at ppm Can be an irritant >4.5 ppm 9/25/ Chlorine Dioxide is not Chlorine No ph dependency Leaves no taste or odor concerns Leaves residual for days Increases shelf life of food products Does not form THM s or other DBP s Penetrates bacteria walls and destroys membranes and biofilms Does not chlorinate Does not react with water 9/25/ Reactions with Organic Substances Chlorine dioxide reacts only as an oxidant Chlorine dioxide does not chlorinate no formation of THM s (trihalomethanes, e.g. chloroform) no formation of chlorophenols no formation of AOX (absorbable organic halides) no reaction with ammonia no taste or odor concerns 9/25/

3 Reaction with Inorganic Substances Iron, Manganese precipitates and has to be filtered 1 mg Iron consumes 1.2 mg ClO 2 Fe 2+ + ClO H 2 O Fe(OH) 3 + ClO H + 1 mg Manganese consumes 2.5 mg ClO 2 Mn 2+ + ClO H 2 O MnO 2 + ClO H + Nitrite is oxidized to Nitrate, Sulfide to Sulfate + Sulfur 1 mg Nitrite consumes 2.9 mg ClO 2 NO ClO 2 + H 2 O NO ClO H + 1 mg Sulfide consumes 2.1 mg ClO 2 2 S ClO 2 SO S + 2 Cl - 9/25/ Chlorine dioxide disinfection efficacy research 1940s 1960s Multiple studies in 1940s and 1950s found ClO 2 more effective than chlorine for killing bacteria at 1-5 PPM dosages Benarde MA et al (1965, 1967) found the E. coli killed at rate of ~99.99% within 30 seconds at 20 C using 0.75 PPM ClO 2 ClO2 comparison with chlorine Not as reactive with organic compounds, ammonia Hoffman et al (1997): ClO2 effective against giardia and crypto 9/25/2018 Above info reference from Hill WAHC 2017 chlorine dioxide disinfection in CYA-stabilized water 8 Ways to Generate Chlorine Dioxide On-site Chemicals: sodium chlorite (NaClO2) hydrochloric acid (HCl) 4 HCl + 5 NaClO2 4 ClO2 + 5 NaCl + 2 H2O 85-90% yield (purity depends on pre-cursors) chlorine-free solution of chlorine dioxide by-products: chlorite and chlorate no handling of chlorine or chlorine gas does not react with bromides 9/25/

4 Other Generation Methods Sodium Chlorite, Chlorine Gas Adding chlorine into process Chance for THM, DBP, TCP formation Store chlorine gas Sodium Chlorite, HCl, Sodium Hypochlorite Adding chlorine into process Chance for THM, DBP, TCP formation Purchase 3-chemicals 9/25/ Other Generation Methods Stabilized Chlorine Dioxide Buffered sodium chlorite solution Decent disinfectant Chlorine Dioxide Sachets (tea bags) Affected by impurities in water Good for specific quantities of water 9/25/ Other Generation Methods Chlorate, Acid, Peroxide Method Uses sodium chlorate, sulfuric acid and H2O2 Good for large quantities of ClO2 Need three chemicals Electro-Chemical Generates ClO2 on-site Water quality is key Undesired by-products (hydrogen, caustic) 9/25/

5 Monitoring Chlorine Dioxide in Your Water Sensors and controllers that can monitor and/or control PPM of chlorine dioxide and/or chlorite Many options for test kits to manually track the chlorine dioxide levels as well. Methods include test strips, DPD test kits, and photometric test kits. 9/25/ On-site Generator Safety Chemicals need to be separated Level switches in chemical tanks Relays on level switches Generator shuts down if tank is empty Flow sensors on pumps to ensure the correct proportion of chemical flow Generator shuts down if pump does not detect flow 9/25/ On-site Generator Safety - continued Flow sensor on bypass water line adjusts the amount of chlorine dioxide generated If water flow is disrupted, generator shuts down Chlorine dioxide is injected into the bypass water flow ClO2 output can be controlled by a chlorine dioxide residual controller 9/25/

6 On-site Generator Safety - continued ClO2 isolated in an enclosed reactor Only a 2% solution is generated (20,000 ppm) Reactor chamber is always full of solution not gas!! 9/25/ Chlorine Dioxide Applications Drinking water Legionella control - hospitals Breweries - CIP - bottle washing Soft drink Dairy industries Wash waters - fruits - vegetables - seafood meat processing plants Horticulture Cooling water Air scrubber Fountain water treatment Recreational Water??? 9/25/ Biofilm - a Universal Problem Slimy coatings of microorganism and extracellular compounds in pipelines and tanks Pathogenic germs as E.coli, Staph and Legionella are living in biofilms Biofilms are extremely resistant against disinfectants Protective cover allows growth Chlorine dioxide and ozone are the only suitable disinfectants able to kill and remove biofilms in water pipes and tanks 9/25/

7 Biofilm - a Universal Problem Biofilms create H2S and HCl The HCl corrodes pipe walls, forming tubercles (blisters) Tubercles create more incubation sites Biofilm is spread through aspiration 9/25/ Resistance of Biofilms Coliform germs survive in biofilms even with 12 ppm of free chlorine Biofilms have even been found on the interior surface of disinfectants piping such as cooling towers and spray misters Chlorine dioxide destroys biofilm in hours ClO2 excellent bactericidal, virucidal, sporicidal, algicidal 9/25/ Chlorine Dioxide for Legionella Control Treatment of the complete cold water - Preventive action for sanitized piping - Degradation of the biofilm in the piping, thus protection against re-infection - Protection against other critical germs such as Pseudomonas 9/25/

8 Treatment of Filters during Backwash with Chlorine Dioxide DIN Disinfection of back wash filter water Min 1 PPM chlorine or 0.6 PPM chlorine dioxide Standard Procedure 5 min filter backwash with 5-6 PPM ClO 2 10 min reaction time in the filter 10 min filter back wash 1 min of normal filtration with dosing of 1 PPM of ClO 2 Back to normal filtration without dosing ClO 2 9/25/ Crypto Treatment Guidelines per CDC Non CYA pools standard hyperchlorination 20 PPM chlorine for hours If CYA in Pool > 15 PPM, standard hyperchlorination not an option Dump water to get 15 PPM then 20 PPM chlorine for 28 hours 9/25/ Crypto VS Chlorine Dioxide No CYA Present Crypto inactivation times and CT values for 5 PPM ClO 2 when no CYA present 3-log CT ClO 2 Conc. Avg FC Conc. 1-log Inact. 2-log Inact. 3-log Inact. Value (mg min/l) log 10 crypto inactivation possible within 3-5 hours ClO 2 Conc. Avg FC Conc. 1-log Inact. Time (hr) 2-log Inact. Time (hr) 3-log Inact. Time (hr) Chlorine dioxide treatment was as effective, or more effective, than hyperchlorination 9/25/2018 Source: Murphy JL et al Environ Sci&Technol, 48:

9 Crypto VS Chlorine Dioxide with CYA Present Preliminary CDC ClO 2 -CYA-Cl disinfection results * CYA ClO 2 Free Chlorine 1-log Kill 2-log Kill 3-log Kill ~6-7 *Study performed using same experimental set-up as described by Murphy et al (2014), except used C. parvum Maine isolate (not Iowa) N = 6 for each condition; ph = ; ClO 2 decay varied (roughly mg/l per hour), requiring statistical modeling 9/25/ What Does All this Mean to Me? Stay up to date on ongoing studies Look at how other industries utilize chlorine dioxide and what can we learn from them Look at how other countries regulate and use chlorine dioxide to keep their patrons as safe as possible Be ready to take advantage of new opportunities to maximize safety and minimize down time at your facilities based on CDC studies and approvals as well as worldwide partner agencies 9/25/ Questions? Thank you for your attention Ken Gibson ProMinent - Inside Sales Manager gibson.ken@prominent.com Dustin Kauffman ProMinent - Aquatics Sales Manager kauffman.dustin@prominent.com 9