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205 Webster Street Bethlehem, PA 18015 888-610-2562 www.cdgenvironmental.comwww.cdgenvironmental.com Application of Chlorine Dioxide in Drinking Water.

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Presentation on theme: "205 Webster Street Bethlehem, PA 18015 888-610-2562 www.cdgenvironmental.comwww.cdgenvironmental.com Application of Chlorine Dioxide in Drinking Water."— Presentation transcript:

1 205 Webster Street Bethlehem, PA Application of Chlorine Dioxide in Drinking Water

2 Webster Street Bethlehem, PA Introduction Chlorine dioxide (ClO 2 ) Powerful, selective oxidant Drinking water treatment > 50 years Must be produced on site A leading alternative to chlorine for oxidation and disinfection

3 Webster Street Bethlehem, PA Chlorine Dioxide Very volatile and reactive Unstable at high concentrations Gas highly soluble in water Oxidizes, does not chlorinate Selective, one-electron transfer Does not react with ammona

4 Webster Street Bethlehem, PA Chlorine Dioxide Potable water Odor and taste control Metals removal THM reduction/elimination Removal of chlorine-resistant pathogens Mollusk control Zebra mussels Process-water Biocide Metals removal Wastewater Oxidation of waste products Color removal Gas sterilization of medical products Decontamination

5 Webster Street Bethlehem, PA Drinking Water Issues Health effects Chlorinated organics (THM, HAA) Chlorine-resistant pathogens (Cryptosporidium, Gardia lamblia) Water quality Taste, odor & color Dissolved metals Regulations EPA-M/DBP Rule (Phase 1) requires compliance by December 15, 2001

6 Webster Street Bethlehem, PA ClO 2 Benefits Does not form chlorinated DBPs (THM, HAA) Does not oxidize bromide ion to bromate ion Broad spectrum microbiocide Inactivates Giardia & Cryptosporidium Improves sedimentation and filtration Lowers turbidity

7 Webster Street Bethlehem, PA ClO 2 vs. Chlorine No cancer-causing by-products formed Kills chlorine-resistant pathogens Superior manganese oxidation Typical ClO 2 dose ~ ppm Typical Cl 2 dose ~ ppm

8 Webster Street Bethlehem, PA ClO 2 vs. Ozone Fewer by-products (e.g., bromate) Lower cost (capital, power) Superior manganese oxidation Minimal power requirements

9 Webster Street Bethlehem, PA Inefficient and unreliable generators Difficult and complicated analytical methods Odor problems “at the tap” Toxicology “data gaps” Unclear regulatory prospects Chlorine Dioxide Historical Limitations

10 Webster Street Bethlehem, PA Drinking Water Regulations Cryptosporidium: 99% removal Giardia lamblia: 99.9% removal Bromate: 0.01 PPM Chlorite: 1 PPM TTHM: 0.08 PPM HAA: 0.06 PPM Toxicology Data Pathogen Regulations DBP Regulations

11 Webster Street Bethlehem, PA Chlorine Dioxide Generation Methods Sodium chlorate (NaClO 3 ) Paper pulp bleaching Very large-scale production Sodium Chlorite (NaClO 2 ) Drinking water treatment, since 1944 Wastewater treatment Industrial process water treatment Medical device sterilization Decontamination

12 Webster Street Bethlehem, PA Chlorine Dioxide Sodium Chlorite-based Generation Methods Acid : Chlorite Solution Chlorine Solution : Chlorite Solution Chlorine Gas : Atomized Chlorite Solution Chlorine Gas:Solid TM Chlorite Process

13 Webster Street Bethlehem, PA Chlorine Dioxide Chlorite Solution Generation Method Oldest sodium chlorite generation method Maximum yield limited to 80% Chlorine dioxide concentration in product variable based on: Sodium chlorite solution concentration Acid concentration pH of reaction Presence of chloride ion Highly inefficient and unreliable

14 Webster Street Bethlehem, PA Chlorine Dioxide Chlorine Solution : Chlorite Solution Excess chlorine is needed to neutralize NaOH in product High conversion, but yield limited to 80% to 90% Very corrosive effluent due to low pH Multiple feed chemical systems required (chlorine gas, chlorine solution or hypochlorite and chlorite solution) Slow mixing of reagents increases chlorite and chlorate production while decreasing yield

15 Webster Street Bethlehem, PA Chlorine Dioxide Chlorine Gas : Vaporized Chlorite Solution State of the art technology prior to Gas:Solid TM system introduction Rapid mixing of reagents improves purity and yield Frequent adjustment, re-calibration and cleaning required to minimize chlorite and chlorate production Liquid chemical feed system Difficult to apply in small applications Chlorite and chlorate in product make analysis difficult

16 Webster Street Bethlehem, PA Chlorine Dioxide Generator Historic Limitations Poor turndown capabilities Re-calibration required when shut down and restarted Unsuited for small plants Generators operated with excess chlorine to create the appearance of high yield

17 Webster Street Bethlehem, PA Chlorine Dioxide Generator Historic Limitations Feedstock/chlorites deteriorate, requiring constant analysis Accurate yield/efficiency/purity analysis required-5-step titration of product By-product concerns

18 Webster Street Bethlehem, PA Chlorine Dioxide Generator Historic Limitations Yield calculation must account for ALL Oxy-chlorine species Chlorine Dioxide + Chlorite + Chlorate + Chlorine Chlorine Dioxide

19 Webster Street Bethlehem, PA Chlorine Dioxide Chlorine Gas:Solid TM Chlorite Process Developed by CDG Technology, Inc. Most advanced generation technology available Product is pure chlorine dioxide gas No chlorite or chlorate ions produced by generator Infinite turndown capability without need for re-calibration Effluent analysis need account only for chlorine dioxide and chlorine

20 Webster Street Bethlehem, PA Chlorine Dioxide Generator Historic Limitations “...this [ Gas:Solid ] process resolves essentially all of the problems associated historically with chlorine dioxide generation...” —George Clifford White, Handbook of Chlorination and Alternative Disinfectants, 4th Edition, 1999

21 Webster Street Bethlehem, PA Gas:Solid TM Plant-Scale Chlorine Dioxide Generators Cl 2 + 2NaClO 2 2ClO 2 + 2NaCl Chlorine Sodium Chlorite Chlorine Dioxide Sodium Chloride

22 Webster Street Bethlehem, PA Gas:Solid TM Plant-Scale Chlorine Dioxide Generators

23 Webster Street Bethlehem, PA Gas:Solid TM Plant-Scale Chlorine Dioxide Generators Model No.GS 8GS 20GS 50GS 100GS 200GS 400 ClO 2 Output (lbs./day) Cl 2 Feed (lbs./day) Panelblend / control / air flowb / c / af Width (in)24 / 17 / / 17 / 12 Height (in)31 / 18 / / 18 / 48 Depth (in)14 / 11 / 9 18 / 11 / 9 Weight (lbs)65 / 25 / / 25 / 28 Power Requirement115V - 5 amps MountingWall EjectorIncluded Manual Cl 2 Rate ValveIncluded OptionsMultiple Cartridge Configuration, Cl 2 Gas Breakthrough Detector

24 205 Webster Street Bethlehem, PA Chlorine Dioxide Generation Method Considerations Chlorine dioxide by-products Chlorite ion: ClO 2 Chlorate ion: ClO 3 Two sources of by-products Inherent with chlorine dioxide use Un-reacted sodium chlorite feedstock

25 Webster Street Bethlehem, PA Chlorine Dioxide Generation Method Considerations Chlorite/Chlorate ion avoidance and removal Generator maintenance and calibration: All except Gas:Solid TM process Generator selection: type, size, etc. Reducing agents - ferrous salts, sulfite Limit amount of contaminants in feedstock (liquid systems) Limit chlorine over-feed (liquid systems)

26 Webster Street Bethlehem, PA Unstable under pressure and in high concentrations (>15%) Never stored or shipped Strong aqueous solutions will release chlorine dioxide gas OSHA maximum exposure limit over 8 hrs. in 0.1 ppm-also odor threshold Chlorine Dioxide Safety Considerations

27 Webster Street Bethlehem, PA Chlorine Dioxide Conventional Generator Safety Considerations Chemical feed systems Materials of construction (storage tanks, pumps, piping) Containment and spill protection Personnel protective equipment Contact with chemicals Generator Operation Proper calibration and adjustment of feed chemicals Personnel protective equipment Contact with chemicals

28 Webster Street Bethlehem, PA Chlorine Dioxide Gas:Solid TM Generator Safety Considerations Chemical handling Process designed to eliminate contact with chemical Sodium chlorite shipped in sealed cartridges Maximum worker safety Safety interlocks Low vacuum Low air flow Excessive chlorine gas flow Low ambient temperature Combustible gas presence Solid sodium chlorite formulation

29 Webster Street Bethlehem, PA Sodium Chlorite Safety Considerations Fuel Fire Ignition SourceOxidant Triangle Sodium chlorite is a strong oxidizer

30 Webster Street Bethlehem, PA Sodium Chlorite Gas:Solid TM Generator Safety Considerations Fuel exclusion Sealed chemical cartridges Ceramic internal cartridge components No external handling after production Air and chlorine gas pass through ultra filtration Combustible gas detector Sodium chlorite formulation

31 Webster Street Bethlehem, PA Sodium Chlorite Gas:Solid TM Generator Safety Considerations CDG Saf-T-Chlor TM sodium chlorite Specially formulated Minimizes possibility of ignition source Absorbs and dissipates heat Does not propagate and ignite

32 Webster Street Bethlehem, PA Gas:Solid TM Generator Safety Review Vacuum feed System shuts down with loss of vacuum Saf-T-Chlor TM does not auto-degrade under excessive heat conditions No direct contact with chemical Closed system No chemical mixing No chemical leaks

33 Webster Street Bethlehem, PA Chlorine Dioxide Summary Guidelines Set clear ClO 2 treatment goal THM & HAA avoidance Taste, odor & color control Disinfection CT Oxidation (iron & manganese) Define use conditions pH Temperature Contact time

34 Webster Street Bethlehem, PA chlorine dioxide, pure and simple


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