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Irwa Presentation 2009

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Chlorine Dioxide Presentation for Illinois Rural Water Association

Chlorine Dioxide Presentation for Illinois Rural Water Association


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  • 1.  
  • 2. OVERVIEW
    • Chlorine Dioxide use & attributes
    • Review of ClO 2 generation used in drinking water applications:
      • 3-Chem (12.5% Bleach +25% NaClO 2 +15%HCL Acid)
      • 2-Chem (Cl 2 gas + 25%NaClO 2 )
      • Electrochemical (25%NaClO 2 + H 2 O)
    • Results from ClO 2 pre-disinfection applications
  • 3. ClO2 Molecular Attributes
    • Lowest Oxidation-Reduction Potential
    • Selective Oxidizer Which Does Not React With Background Organics
    • Effective For the Removal of Bio-Film
    • Works Over a Broad pH Range
    • Readily Reacts With Iron & Manganese
  • 4. Oxidation/Reduction Potentials Compound ORP (Volts) Oxidation Capacity Ozone (O3) 2.07 2 Electrons Hydrogen Peroxide (H2O2) 1.76 2 Electrons Hypochlorous Acid (HOCl) 1.49 2 Electrons Chlorine (Cl2) 1.36 2 Electrons Hypobromus Acid (HOBr) 1.33 2 Electrons Chlorine Dioxide (ClO2) 0.95 5 Electrons
  • 5. Comparison of Disinfectant Oxidation Potentials (EOP) of Various Oxidants ClO 2 reacts by oxidation, but is not a strong oxidizer Why does ClO 2 work so well at low doses?
  • 6. Does Not React With Background Organics
    • Does Not React With
      • Aldehydes Ethers
      • Ammonia Fats
      • Acids Glycols
      • Alkanes Ketones
      • Alkynes Polysaccharides
      • Alcohols Saccharides
      • Amines Unsaturated Fatty Acids
      • Carbohydrates Unsaturated Aromatics
  • 7. ClO 2 Efficacy from Chemical Selectivity
    • HOCl, H 2 O 2 and O 3 Are Indiscriminant Oxidants
      • React with nearly any organic or inorganic species present
      • Consumed by useless side-reactions
    • Chlorine Dioxide Reacts Selectively
      • Reacts rapidly with sulfides (S 2- )
      • Reacts rapidly with aromatic hydroxides (phenols)
      • ClO 2 less effected by organic contamination
  • 8. Bacterial Biofilm… What is it?
    • Sessile microorganisms embedded in a gelatinous matrix.
    • Anchored to a surface by polymeric sugars (polysaccharides).
    • Factors affecting biofilm formation include nutrient availability hydrodynamics, composition of microbial community, and cellular transport .
  • 9.
    • Aerobic Bacteria
      • Slimers - Pseudomonads, Mucoids
      • Spores - Bacillis Subtilis
      • Fecal - Enterobacter
      • Ubiquitous - Anabena, Asterionella
    • Anaerobic Bacteria
      • Sulfate Reducing Bacteria – Desulfovibrio
      • Iron Reducing Bacteria – Gallionella
    • Protozoa
      • Consume bacteria
    Types & Kinds of Micro-organisms
  • 10. Heterogeneity of Biofilm structure and function
  • 11. Interpretation of Biofilm Diversity
    • Aerobic and anaerobic species capable of co- existing.
    • Proliferating and dormant species co-exist.
    • Single layer to 3 dimensional structures.
    • Unicellular to multi-cellular.
    • Biofilm remediation indicates that a weaker disinfectant, (if it penetrates) will easily outperform a strong disinfectant that fails to penetrate
  • 12. 3 step Biofilm life cycle
  • 13.
    • Good planktonic control does not always correlate with good biofilm control
    • A biofilm under low continuous stress may persist and continue to grow slowly
    • Typically monitor planktonic counts, leaving us with a false sense of security
    • High stress can “shock” biofilm off walls, resulting in more complete disinfection
    • Therefore, best practice for biofilm elimination is not continuous feeding of disinfectant, but shock treatment of the films
    Biofilm vs. Planktonic Control
  • 14. Attachment Surface Bulk Water ClO 2 S-S ClO 2 - ClO 2 H + Catalytic ClO 2 Chemistry in Biofilm Sodium Chlorite/Chlorate Sodium Chlorite/Chlorate
  • 15. Dissociation vs. pH pH 100 90 80 70 60 50 40 30 20 10 0 7 8 9 10 1 1 12 13 14 HOBr OBr - HOCl OCl- Percent Hypohalous Acid ClO 2 pH % HOBr % HOCl % ClO 2 7.5 8.0 8.5 9.0 94 83 60 33 48 22 9 3 100 100 100 98 2 ClO 2 ClO 2 - + ClO 3 -
  • 16. Chlorine Dioxide-Manganese Reaction
    • 2Cl0 2 + Mn 2+ +2H 2 O  2Cl0 2 - + MnO 2 + 4H +
    • Theoretical Consumption
    • 2.45 mg of Cl0 2 per mg of Mn 2+
  • 17. Chlorine Dioxide-Iron Reaction
    • Cl0 2 + Fe 2+  Fe 3+ + Cl0 2 -
    • Fe 3+ + 3 OH -  Fe(OH) 3
    • Theoretical Consumption
    • 1.2 mg of Cl0 2 per mg of Fe 2+
  • 18.
    • Dual Wet Chem Generators
    • Chlorine Gas
    • Sodium Chlorite (dry or liquid)
    • Three Wet Chem Generators
    • 12.5% Sodium Hypo-chlorite
    • 15% Hydrochloric Acid
    • 25% Sodium Chlorite
    Traditional ClO 2 Generation Methods
  • 19. Traditional ClO 2 Generation Methods
    • Cumbersome
    • Increased chemical handling
    • and management
    • Difficult to optimize CLO 2
    • conversation
    • CLO 2 external batch tank
    • required
    • Complicated
    • Difficult to operate, troubleshoot
    • and repair
    • Impure Product
    • need to over feed acid and
    • bleach for a higher percent
    • conversation
    • increases more unwanted
    • by-products
  • 20. Electrochemical ClO 2 Generation
    • SIMPLE
    • Turnkey installation
    • Fully automated
    • Color touch screen PLC controller
    • interface
    • Flow paced feed
    • SAFE
    • single precursor technology
    • (PureCide 25 TM solution)
    • reliable operation
    • multiple safety interlocks
    • and alarm features
    • PURE
    • 99.5% pure CLO2 gas
    • CLO 2 gas diluted with water into
    • adsorption column
  • 21. PureLine ® HP-Series Generators Electrochemical ClO 2 Production: Anode: ClO 2 -  ClO 2 + e - + Na + Cathode: H 2 O + e -  1/2 H 2 + OH - Na + + OH -  NaOH
  • 22. PureLine ™ HP-Series Electro-chemical ClO 2 Generator Electrochemical Production of Chlorine Dioxide: Anode: ClO 2 - ----> ClO 2 + e - Cathode: H 2 O + e - ---> 1/2 H 2 + OH - (0.1%H 2 ) Na + + OH - ---> NaOH
  • 23.  
  • 24. Electrochemical CIO 2 Advantages
    • Provides 99.5% Pure ClO 2
    • Single Precursor (PureCide 25 TM solution)
    • On-Demand Feed Control
    • No External Water Pretreatment Required
    • ClO 2 Production Capacity Up To 80 lbs/day
    • DCS Capable/Automated Feed Control
  • 25. Electrochemical CIO 2 Operational Costs Electrical Consumption Per Pound of ClO 2 55 watts per lb. Chlorine Dioxide $0.085/KWH = $7.14 per day electrical usage PureCide 25 TM solution Consumption 6.6 lbs Per Pound of ClO 2
  • 26. DBP Monitoring
    • Greenville, Il:
    • Testing Started in 1990
      • 101 ppb TTHM (1 st Quarter Average)
      • 47 ppb TTHM (2 nd Quarter Average)
      • 123 ppb TTHM (3 rd Quarter Average)
      • 107 ppb TTHM (4 th Quarter Average)
    What To Do? What are my choices?
  • 27. Ways to Minimize DBPs
    • Upgrade to Micro-Filtration
    • Move Back the Cl2 Pre-Disinfection Point
    • Pre-Disinfect with Ozone or UV
    • Pre-Disinfect with
    • Chlorine Dioxide
  • 28. Ways to Minimize DBPs
    • Microfiltration
      • Very effective, non-chemical means to remove suspended particulates down to sub-micron levels
      • Very expensive: ~ $8-$10 MM fully installed for 2.5 MM GPD
      • Requires extensive
      • maintenance
  • 29. Ways to Minimize DBPs
    • Move Back the Cl 2 Pre-Disinfection Point
      • Reduction in CT- credits
      • Increased corrosion if an increased Cl 2 dose is required for CT-credit
      • pH sensitive
  • 30. Ways to Minimize DBPs
    • Pre-Disinfect with Ozone
    • - Increases the potential for biodegradable organic matter, creating a requirement for a biologically active filter.
      • Complex operation requires significant training and maintenance
      • Capital costs estimated at $0.5 to $1 MM
      • No THMs or HAAs, but potential for bromate formation (10 ppb MCL)
      • Bromate formation occurs faster than pathogen inactivation, Bromate increase with increase of O 3 dosage feed.
      • High efficacy at low dose
      • Must be produced on-site
      • Energy intensive
      • No residual
  • 31. Ways to Minimize DBPs
    • Pre-Disinfect with Chlorine Dioxide
      • More efficacy at a lower dose than Cl 2 (CT-values)
      • Not sensitive to pH
      • No THM or HAA production
      • No bromate production
      • Must be produced on-site
      • Effective for taste and odor
      • Effective for turbidity reduction
      • Minimal capital cost expenditure
  • 32. ClO 2 On-Site Generation
    • Prefer the chemistry of ClO 2 , but are concerned about:
    • storing and handling multiple chemical precursors
    • purity of the ClO 2 generated
    • monitoring and maintaining ClO 2 and NaClO 2 residuals below the MCLs
    • reliability and simplicity of the generation and feed system
  • 33. ClO 2 Regulatory Status
    • MRDL of 1.0 mg/L – Chlorite/Chlorate Ion
    • MCL of 0.8 mg/L – Chlorine Dioxide
  • 34. Chlorine Dioxide, Chlorite, Chlorate Analytical Methods
    • Compliance monitoring for measuring residual Chlorine Dioxide
    • A) DPD Standard Method 4500-CLO 2 D
    • B) Amperometric Titration Method II
    • Standard Method 4500-CLO 2 E
    • Compliance monitoring for measuring residual Chlorite/Chlorate Ion
    • A) Amperometric Titration
    • Standard Method 4500-CLO 2 E,
    • B) Ion Chromatography EPA Method 300.0 & 300.1
    • Amperometric Titration may be used for routine daily monitoring of Chlorite at the entrance to the distribution system.
  • 35. Typical ClO 2 Feed Point SOURCE WATER SILT & MUD TANK PRIMARY SETTLING BASIN SECONDARY SETTLING BASIN FLOCCULATION BASIN (SLOW MIXER) COAGULATION BASIN (FLASH MIXER ) CLEAR WELL COAL & SAND FILTER BAR SCREENS CHLORINE DIOXIDE LOW LIFT PUMPS SLUDGE DISPOSAL TO CANAL SLUDGE RETURNED TO CANAL CHLORINE HIGH LIFT PUMPS TO DISTRIBUTION SYSTEM LIME IRON CARBON POLY-ELECTROLYTES
  • 36. Pure ClO 2 Results
    • Use of pure ClO 2 for pre-disinfection
    • provided several benefits:
    • Improved disinfection
    • Improved DBP reduction
    • Improved turbidity reduction
    • Improved taste and odor
    • Improved safety
  • 37. Pure ClO 2 Results Improved Disinfection and DBP Reduction
    • Addition of Chlorine Dioxide allowed the plant to discontinue Carbon & KMnO4
    • Chlorite residuals remained well below the MCLs in the distribution system
    • 82% DBP reduction in 2008 Q2 levels vs. 2007 Q2 levels
    • 76% DBP reduction YTD 2008 vs. 2007
  • 38. Pure ClO 2 Results
  • 39. Chlorine “Chlorinates”, Chlorine Dioxide “Oxidizes” HOCl + Organic  Cl-Organic (THM/HAA/AOX) ClO 2 (O=Cl=O) + Organic  O-Organic (-) O 3 (O-O-O) + Organic  O-Organic (-)
  • 40. Pure ClO 2 Results – Taste & Odor
    • Taste & Odor greatly improved even with the discontinued use of Carbon & KMnO4
    • Oxidation of metals and organics to make more negatively charged particles that readily bond to the cationic coagulant
    • “ People in town were asking what had changed. The water tasted more like bottled water.”
  • 41. Pure ClO 2 Results – Improved Safety Greenville, Il
    • Cl 2 gas cylinder usage reduced by 50%
    • Automated feed system provided operator-free operation
    • KMnO4 & Carbon elimination resulted in reduced operator exposure to chemicals
  • 42. Conclusions The City of Greenville was faced with unacceptably high concentrations of DBPs due to pre- and post-chlorination of surface water.
  • 43. Conclusions ClO 2 chosen over alternatives: - increased CT-credits - improved DBP reduction - eliminated KnMnO4 & Carbon - improved operator safety - simplicity of feed
  • 44. Conclusions Pre-disinfection with pure ClO 2 provided a very cost-effective means for dramatically reducing DBP levels while improving the microbial control, turbidity, taste and odor with a reduction in chemical use resulting in a 3.5 – 4 year ROI.
  • 45. Conclusions Use of Pure CIO 2 Resulted in :
    • increase in CT credits
    • 82% TTHM reduction Q2 2008 vs. Q2 2007
    • 76% TTHM reduction in 2008 vs. 2007
    • 50% reduction in use of Cl2 gas
    • Improved taste & odor
  • 46. Questions? PureLine Treatment Systems www.pureline.com