1. 205 Webster Street Bethlehem, PA 18015 888-610-2562 www.cdgenvironmental.comwww.cdgenvironmental.com An Overview of Chlorine Dioxide Usage in Water Dean Gregory CDG Environmental, LLC

2. 22 205 Webster Street Bethlehem, PA 18015 888-610-2562 www.cdgenvironmental.comwww.cdgenvironmental.com Agenda Background Chlorine dioxide (ClO 2 characteristics) Regulatory concerns ClO 2 vs. free chlorine ClO 2 applications in water treatment Bench/full-scale data Analytical requirements (chlorite) ClO 2 generating systems

3. 33 205 Webster Street Bethlehem, PA 18015 888-610-2562 www.cdgenvironmental.comwww.cdgenvironmental.com Background Chlorine dioxide (ClO 2 ) Used in drinking water treatment > 50 years First used in U.S. for T&O control (Niagara Falls, NY) A primary alternative to free chlorine for oxidation and disinfection Generally not used for secondary disinfection 205 Webster Street Bethlehem, PA 18015 888-610-2562 www.cdgenvironmental.comwww.cdgenvironmental.com

4. 44 205 Webster Street Bethlehem, PA 18015 888-610-2562 www.cdgenvironmental.comwww.cdgenvironmental.com Background 1st ClO 2 application point 2nd ClO 2 application point

5. 55 205 Webster Street Bethlehem, PA 18015 888-610-2562 www.cdgenvironmental.comwww.cdgenvironmental.com Background General Characteristics Highly soluble in water (10x more than Cl 2 ) Volatile & subject to photo-decomposition Unstable at high concentrations (>15%) and under pressure ~ must be generated onsite Oxidizes, does not chlorinate, using selective one-electron transfer Does not react with ammonia Unaffected by pH over broad range (4-8)

6. 66 205 Webster Street Bethlehem, PA 18015 888-610-2562 www.cdgenvironmental.comwww.cdgenvironmental.com Background Demand/Decay Characteristics TOC = 5.1 mg/L pH = 6.6 Mn 2+ < 10 μ g/L TOC = 1.2 mgl/L

7. 205 Webster Street Bethlehem, PA 18015 888-610-2562 www.cdgenvironmental.comwww.cdgenvironmental.com Background Demand/Decay Characteristics TOC = 5.6 mg/L Mn 2+ = 250 μ g/L TOC = 1.4 mgl/L Mn 2+ = 0 μ g/L

8. 88 205 Webster Street Bethlehem, PA 18015 888-610-2562 www.cdgenvironmental.comwww.cdgenvironmental.com Regulations of Concern Ct Disinfection Targets (20°C) 2-log Giardia lamblia: 10mg/L*min 2-log virus: 2.1mg/L*min 0.5-log Crypto (20°C): 58mg/L*min 0.5-log Crypto (10°C): 138mg/L*min D/DBP Rule (MCL) TTHM: 0.08 ppm HAA: 0.06 ppm Chlorite: 1.0 ppm

9. 99 205 Webster Street Bethlehem, PA 18015 888-610-2562 www.cdgenvironmental.comwww.cdgenvironmental.com Regulations of Concern Chlorite ion (ClO 2 ) Must be measured daily at POE Monthly samples from distribution system Amp. titration ≈ 30 min. with experience LGB method Requires laboratory technician Colorimetric Provides ClO 2 and ClO 2 residuals

10. 10 205 Webster Street Bethlehem, PA 18015 888-610-2562 www.cdgenvironmental.comwww.cdgenvironmental.com Chlorine Dioxide vs. Chlorine No THM/HAA formation Giardia Ct requirements significantly lower Superior manganese oxidation Typical ClO 2 dose ~ 0.6 - 1.7 ppm Typical Cl 2 dose ~ 2.0 - 5.0 ppm

11. 11 205 Webster Street Bethlehem, PA 18015 888-610-2562 www.cdgenvironmental.comwww.cdgenvironmental.com Chlorine Dioxide vs. Chlorine Reactions with Natural Organic Matter HOCl + NOMTTHM, HAA ClO 2 + NOMClO 2 + Low MW organic compounds ClO 2 reacts ONLY through a one-electron oxidative pathway

12. 12 205 Webster Street Bethlehem, PA 18015 888-610-2562 www.cdgenvironmental.comwww.cdgenvironmental.com Water Treatment Applications TTHM/HAA Precursor Destruction Greater impact on TTHM precursors Manganese Oxidation Taste & Odor Control (algae, diatoms) Inactivates Giardia and viruses CT for 2-log Giardia inactivation: 10mg/L-min at 20°C CT for 2-log virus inactivation: 2.1mg/L-min Pre-ox.

13. 13 205 Webster Street Bethlehem, PA 18015 888-610-2562 www.cdgenvironmental.comwww.cdgenvironmental.com Water Treatment Applications Impact on TTHM/HAA-5 Formation Raw TOC = 4.3 mg/L

14. 14 205 Webster Street Bethlehem, PA 18015 888-610-2562 www.cdgenvironmental.comwww.cdgenvironmental.com Water Treatment Applications Impact on TTHM/HAA-5 Formation Raw TOC = 5.1 mg/L

15. 15 205 Webster Street Bethlehem, PA 18015 888-610-2562 www.cdgenvironmental.comwww.cdgenvironmental.com Water Treatment Applications Impact on TTHM/HAA-5 Formation Raw TOC = 6.2 mg/L

16. 16 205 Webster Street Bethlehem, PA 18015 888-610-2562 www.cdgenvironmental.comwww.cdgenvironmental.com Water Treatment Applications Impact on TTHM/HAA-5 Formation Raw TOC = 7.8 mg/L

17. 17 205 Webster Street Bethlehem, PA 18015 888-610-2562 www.cdgenvironmental.comwww.cdgenvironmental.com Water Treatment Applications Mn 2+ Oxidation Raw TOC = 6.3 mg/L pH = 6.8 mg/L Contact time = 5 min.

18. 18 205 Webster Street Bethlehem, PA 18015 888-610-2562 www.cdgenvironmental.comwww.cdgenvironmental.com Water Treatment Applications Impact of ClO 2 on Chlorophyll-a Pilot Results (presented at ’05 WQTC) DateRaw Water Chlor-aPost-ClO 2 Chlor-aReduction μg/L % August 20210100 August 2431095 September 290100 September 14220100 September 2450100 September 30180100 October 5710100 October 717092 October 1290100 October 22300100 October 26200100 November 8110100 November 1680100 November 1860100 November 22110100

19. 19 205 Webster Street Bethlehem, PA 18015 888-610-2562 www.cdgenvironmental.comwww.cdgenvironmental.com Full-Scale Case Study ClO 2 for Pre-ox. and Disinfection Raw water Clearwell Water Quality (TX Utility) Raw TOC = 4.3 mgl/L (lower Rio Grande) pH = 7.2, T = 23° Pre-ox ClO 2 : 0.85 mg/L Post-filt. ClO 2 : 0.85 mg/L

20. 20 205 Webster Street Bethlehem, PA 18015 888-610-2562 www.cdgenvironmental.comwww.cdgenvironmental.com Full-Scale Results Texas Utility (6 mgd) Total ClO 2 dose = 1.6 - 1.8 mg/L

21. 21 205 Webster Street Bethlehem, PA 18015 888-610-2562 www.cdgenvironmental.comwww.cdgenvironmental.com Water Treatment Issues Chemical sequencing Avoid NaOH/High-pH conditions pH > 9 = instant destruction Avoid simultaneous application with NH 2 Cl 0.2 - 0.4 mg/L decrease in ClO 2 residual Interference from coagulant possible Pre-ox. DT > 5 min. is optimum

22. 205 Webster Street Bethlehem, PA 18015 888-610-2562 www.cdgenvironmental.comwww.cdgenvironmental.com Analytical Methods Amperometric titration Manual and semi-automatic systems Ion chromatography Expensive, requires highly-trained technician, turnaround time Colorimetric (forming or removing a color)

23. 23 205 Webster Street Bethlehem, PA 18015 888-610-2562 www.cdgenvironmental.comwww.cdgenvironmental.com Amperometric Titration Hach™ AutoCat 9000 Amperometric Titrator

24. 24 205 Webster Street Bethlehem, PA 18015 888-610-2562 www.cdgenvironmental.comwww.cdgenvironmental.com ClO 2 Generation Systems Solution-based systems Chlorine Gas/25% Sodium Chlorite (NaClO2) Solution Most common Sulfuric Acid: Chlorate/Hydrogen Peroxide Solution (Purate) Electrochemical (small systems) Acid-chlorite (less efficient) Solid-based systems (CDG Gas: Solid™)

25. 25 205 Webster Street Bethlehem, PA 18015 888-610-2562 www.cdgenvironmental.comwww.cdgenvironmental.com Generation Systems NaClO 2(aq) : Cl 2(gas) 2ClO 2 + Cl 2 2ClO 2 + 2Cl Efficient mixing of reagents improves purity and yield (95% attainable) High-concentration solution can be batched and fed from day tank Most efficient with chlorine overdose

26. 26 205 Webster Street Bethlehem, PA 18015 888-610-2562 www.cdgenvironmental.comwww.cdgenvironmental.com Generation Systems NaClO 2(aq) : Cl 2(gas) 2ClO 2 + Cl 2 2ClO 2 + 2Cl Effluent must be analyzed regularly to ensure efficiency i.e. addition amp. titration required frequent re-calibration possible Disruption in Cl 2(g) feed may cause ClO 2 spike Sodium chlorite storage/leaks are biggest safety concern

27. 27 205 Webster Street Bethlehem, PA 18015 888-610-2562 www.cdgenvironmental.comwww.cdgenvironmental.com Generation Systems Sulfuric Acid: NaClO 3(aq) 2NaClO 3 + H 2 O 2 + H 2 SO 4 2ClO 2 + Na 2 SO 4 + O 2 Effluent must be analyzed regularly to ensure efficiency Bulk storage of sodium chlorate and 73% sulfuric acid required Purate®

28. 28 205 Webster Street Bethlehem, PA 18015 888-610-2562 www.cdgenvironmental.comwww.cdgenvironmental.com CDG Gas:Solid™ Process Cl 2 + 2NaClO 2 2ClO 2 + NaCl Chlorine GasSolid Sodium Chlorite SAF-T-CHLOR™ Chlorine Dioxide GasSolid Sodium Chloride

29. 29 205 Webster Street Bethlehem, PA 18015 888-610-2562 www.cdgenvironmental.comwww.cdgenvironmental.com CDG Gas:Solid™ Plant-Scale ClO 2(g) Generators Cl 2 + 2NaClO 2 2ClO 2 + 2NaCl

30. 30 205 Webster Street Bethlehem, PA 18015 888-610-2562 www.cdgenvironmental.comwww.cdgenvironmental.com

31. 31 205 Webster Street Bethlehem, PA 18015 888-610-2562 www.cdgenvironmental.comwww.cdgenvironmental.com CDG Gas:Solid™ Process Produces pure ClO2 gas, minimizes chlorite ion Relatively simple operation: Cl2(g) feed only Flow-paced: Generator production changes with plant capacity w/o need for re-calibration No need for additional titrations of generator effluent Safety

32. 32 205 Webster Street Bethlehem, PA 18015 888-610-2562 www.cdgenvironmental.comwww.cdgenvironmental.com CDG Gas:Solid™ System Safety Considerations Chemical handling Sodium chlorite shipped in sealed cartridges w/ quick disconnects Maximum operator safety ~ no contact with the chemical No liquid chemical storage & handling Safety interlocks Low vacuum Low air flow Excessive chlorine gas flow Combustible gas presence

33. 33 205 Webster Street Bethlehem, PA 18015 888-610-2562 www.cdgenvironmental.comwww.cdgenvironmental.com CDG Gas:Solid™ System Safety Considerations Saf-T-Chlor™ Thermally Stable Sodium Chloride Specially formulated Minimizes possibility of ignition source Absorbs and dissipates heat Does not propagate and ignite Sealed cartridges with ceramic internal components

34. 34 205 Webster Street Bethlehem, PA 18015 888-610-2562 www.cdgenvironmental.comwww.cdgenvironmental.com New Option for ClO 2 Applications CDG Solution 3000 ® Stabilized ClO 2 solution - 3000 mg/L Ideal for small systems, pilot plants Available in 55g drums, 275g totes

35. 35 205 Webster Street Bethlehem, PA 18015 888-610-2562 www.cdgenvironmental.comwww.cdgenvironmental.com CDG Consultative Programs Water Treatability Studies Protocols dependent on program objectives Testing done on actual raw water Trial programs Production unit installed at water plant Limited financial exposure

36. 36 205 Webster Street Bethlehem, PA 18015 888-610-2562 www.cdgenvironmental.comwww.cdgenvironmental.com Questions? CDG Environmental, LLC. 205 Webster Street Bethlehem, PA 18015 888-610-2562 www.cdgenvironmental.com