1. Compliance Strategies for Stage I & II DBPR 4 Case Studies William Bellamy CH2M HILL

2. DBP Compliance Case Studies Aurora Colorado - Chlorine dioxide Casper Wyoming - Enhanced coagulation and inline ozone Henderson Nevada - UV Denver Colorado - Optimized chlorination / chloramination

3. Case Study Aurora Colorado Direct filtration plant Chlorine primary disinfection Chloramine residual disinfectant Drivers THMs can be as high as 90 ug/L Disinfection with chlorine and chloramines is minimal

4. Disinfectant Evaluation - Chlorine Advantages Current practice – no change in technology required Does not form chlorite Does not form bromate Disadvantages Relatively weak disinfectant- not capable of providing Crypto inactivation Forms TTHMs and HAAs – Aurora may not be able to meet Stage 2 of D/DBPR Requires construction of post- filter disinfection contact basin Relatively no benefit for T&O control Pre-chlorination can not be practiced. Loss of pre-oxidant will degrade performance of filtration process.

5. Disinfectant Evaluation - Chlorine Dioxide Advantages Lowest capital cost (0 to $250,000) Minimal investment; nothing lost if ozone is implemented later. No construction of new contact basin (capital cost savings of $3,000,000) Does not form bromate Chlorite can be controlled to < 1 mg/L (for 1-log Giardia disinfection goal). Does not form TTHMs and HAAs. would meet anticipated Stage 2 D/DBPR regs Disadvantages Requires change in technology/operations Will probably require that the existing contact basin be covered to mitigate UV degradation. ($400,000) Requires handling of sodium chlorite, and higher attention to safety. Chlorite control might be required. Higher dosages (for possible future Cryptosporidium inactivation requirement) would produce chlorite concentrations above 1 mg/L.

6. Disinfectant Evaluation - Chlorine Dioxide (cont’d) Advantages Can provide 0.5-log inactivation of Cryptosporidium Strong oxidant – will help control Quincy T&O problems, and could eliminate KMNO 4 and PAC system. Will reduce manganese concentrations though oxidation/filtration Application to raw water will provide benefit to filtration performance (pre-oxidation) Disadvantages Could be more costly (operations) than ozone for Cryptosproidium inactivation. Some negative experience with taste and odor. Mainly with inefficient systems, that used free chlorine for residual disinfectant. Chlorine oxidized chlorite and formed ClO2 in the distribution system. (Not a problem if chloramine is used).

7. Master Plan Evaluation of Disinfectant Costs

8. Initial Demand and Decay Rate Determines ClO 2 Dosage & CT 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 051015 Time (min) ClO 2 (mg/L) Initial Demand ClO 2 Concentration Decay Area Under Curve Represents CT Achieved

9. Existing Contact Flocculation Basin Can Be Optimized for t 10

10. Chlorine dioxide contactor modifications

11. Why Isn’t ClO 2 More Common? Until recently, minimal regulatory incentive to increase disinfection Poor efficiency and performance of older style generators Toxicology gaps for ClO2 - and ClO 3 - –mclg for CLO 2 - was increased from 0.08 to 0.8 mg/L –No mclg for CLO 3 -

12. Aurora Conclusions ClO 2 can meet current disinfection requirements without construction of chlorine contact basin (saves $2.8 million) ClO 2 provides some taste and odor control

13. Conclusions (cont’d) ClO 2 can meet current disinfection requirements without chlorite control Implementation of ClO 2 preserves capital and provides time to: –Evaluate alternatives –Allow regulations to solidify

14. Casper Wyoming 52 mgd plant with conventional treatment for 27 mgd and 25 mgd wells Inadequate disinfection and DBPs approaching Stage I

15. Driving Factors for Casper’s Disinfection Evaluation GWDUI Apply Disinfectant to Ground Water & Surface Water Discontinue Chlorination Cost Estimates

16. Existing Surface Water Treatment System From North Platte River Screens Floc/Sed Alum Filters Transfer Pumping Chlorine Storage High Service Pumping To Distribution System Washwater Lagoons Sludge Lagoons Raw Water Pumping

17. Upgraded Surface Water Treatment Process From North Platte River Screens Actiflo Clarification SO4 FeCl3 Filters NaOCl NH4 Ortho-PO4 High Service Pumping To Distribution System Washwater Lagoons Sludge Lagoons Raw Water Pumping Settled Water Pumping Ozone Ozone Contactor

18. Level of Disinfection

19. Surface Water Ozone Demand

20. Surface Water Ozone Decay

21. Ozone Contactor Alternatives High-Pressure In-Line Contacting Low-Pressure In-Line Contacting Conventional Over-Under Baffled Contactor

22. Recommended Low-Pressure In-Line Ozone Contactor

23. Casper Conclusions Ozone will provide up to 2 log Cryptosporidium inactivation THMs and HAAs will be reduced to below 10 ug/L Bromate is not an issue Inline ozone was the least cost alternative

24. Henderson Nevada UV Disinfection Direct filtration plant Chlorine disinfection for 1 log Giardia and 2 log virus inactivation Need to achieve 2 log Crypto inactivation Future need for chloramines for THM and HAA control DBP and Disinfection Drivers

25. Disinfection Objectives Provide Cost-Effective Disinfection No Less Than 2-Log Cryptosporidium Inactivation No Less Than 2-Log Giardia Inactivation Provide Capability to Eliminate Use of Free Chlorine for Primary Disinfection

26. Disinfection Alternatives Evaluated Ozone Ultraviolet Disinfection Chlorine Dioxide Membranes

27. Disinfectant Comparison Ozone Strong oxidant (+) Powerful disinfectant (+) Microflocculation (+) Controls taste and odor (+) Increases concentration of D.O. (-) High cost (-) Disinfection mechanism not completely defined (-) Bromate formation (-) Increases concentration of AOC (-) Operationally complex (-) UV No byproduct formation (+) Effective protozoan and viral disinfectant (+) Generated onsite (does not require LOX delivery) (+) Lower cost (+) Disinfection mechanism not completely defined (-) Lamp cleaning/replacement (-) No measure of disinfectant “residual” (-)

28. Calculation of UV & Ozone Disinfection Performance Ozone Relies on measurement of residual and hydraulic modeling to calculate CT Contactor design validated with tracer testing (t 10 ) Monitoring disinfectant provides continuous measure of disinfection efficiency UV UV intensity sensors, flow signal, lamp age, UV transmittance and power measurement to calculate dose (I x t), and assess possible problems EPA expected to publish IT values in near future (2-3 years)

29. Why Hasn’t UV Been More Prevalent for Potable Water Treatment?

30. Previous Studies Used In Vitro Assays for Protozoan Inactivation Cell Excystation (Viability Assay Using In Vitro Measure of Ability of Oocyst to Excystate [Open Up] Under Simulated Gut Environment) Vital Dyes (in Vitro Assay Using Fluorogenic Vital Dyes That Adhere to Viable Oocysts or Non-viable Depending on Dye) Study Showed UV Dose of 120 mJ/cm 2 for 2-log Cryptosporidium Inactivation (Ransome et al, 1993)

31. Infectivity Tests Provide New Understanding of Protozoa Inactivation By UV Infectivity Assays Using Neonatal Mice (In Vivo) In Vitro Assays Unable to Correctly Predict Infectivity Infectivity Accurately Tests the Ability to Cause Disease Not Just Viability

32. -5 -4 -3 -2 0 050100150200 UV Dose, mW-sec/cm 2 Log (N/N o ) Excystation Infectivity After Clancy et al., 1998 [Demonstration Scale Testing] Medium-Pressure UV Lamp Recent Research Indicates Capability of UV for Cryptosporidium Inactivation

33. Recent UV Inactivation Data for Cryptosporidium Clancy; 2.8 to 4.8 Log Crypto Inactivation Using 25 mJ/cm 2 Bolton; 3-Log Crypto Inactivation at 20 mJ/cm 2 Finch; 2.5 to 4.6 Log Crypto Inactivation Using 28 mJ/cm 2 Sobsey & Linden; 4-Log Crypto Inactivation Using 15 mJ/cm 2

34. Giardia Inactivation Capability of UV Previous Studies (Hoff, Karanis) Showed Doses of 100 to 180 mJ/cm 2 Required for 2.0-Log Giardia Inactivation Sobsey & Linden; 4-log Giardia Inactivation Using 15mJ/cm 2 Bolton; 3-log Giardia Inactivation at 20 mJ/cm 2

35. UV Regulatory Status in the U.S. Widely Used Since 1980’s in WW Treatment and Reclamation (CA Title 22 Approval) SWTR Included UV Doses for 2 and 3 Log Virus Inactivation in 1989/1990 EPA Proposes Groundwater Rule With UV As a Likely BAT in 1991 1998 - New Cryptosporidium Research Released 1999 - EPA Sponsors UV Workshop for FACA

36. Henderson’s UV Implementation Strategy Bench-Scale Testing –Conduct bench-scale collimated beam testing to establish dose-response relationship for MS-2 and/or Bacillus subtilis for Henderson’s water Design and Construction –Evaluate/select the UV system vendor based on an evaluated bid –Detailed design of UV system including controls and monitoring –Installation –Full-scale performance validation

37. Henderson’s UV Implementation Strategy (cont’d) Validation –Full-scale demonstration using MS2 phage/Bacillus spores –Back-calculate full-scale system dosage Maintenance –Routine cleaning/replacement of UV lamps –Routine cleaning/calibration/replacement of UV sensors

38. Henderson NV Conclusion UV achieved disinfection and DBP goals Lowest cost option Regulatory approval can coincide with design and construction

39. Denver Water Chlorine Disinfection Conventional water treatment at 3 water treatment plants Disinfection with chlorine followed by chloramines Need to reduce THMs and HAAs Planning for future disinfection and DBP regulations DBP and Disinfection Drivers

40. Current Disinfection Practice Chlorine Headworks Raw Water Rapid Mix Flocculation/ Sedimentation Filter Clear Water Reservoirs Chlorine Ammonia

41. Project Goals Continue to meet current EPA disinfection requirements Improve safety / reliability Identify strategies for future compliance Develop implementation plan and costs

42. Disinfection Regulations Current: 30 minutes contact SWTR:0.5-log Giardia inactivation ESWTR: 0 to 3-log (0 to 99.9%) Cryptosporidium inactivation

43. Short Term - 0.5-log Giardia Inactivation - TTHMs < 80 ppb, HAAs < 60 ppb - Eliminate prechlorination Long Term - Cryptosporidium inactivation - Lower levels of DBPs Disinfection Objectives

44. Short Term Planning Will chlorine meet short-term goals? On-site NaOCl generation $24.9M Purchase NaOCl $21.8M Evaluate other disinfectants Can risks be mitigated? Bulk Chlorine Gas Yes NoNo NoNo Bulk chlorine $10.2M Purchase NaOCI

45. Meets Criteria Long-Term Planning Evaluate Performance of Chlorine Chloramine Chlorine Ozone or UV Conduct Ozone / UV Studies Crypto Inactivation > 1.0 Log Crypto? Meets DBPR Yes No Yes No Yes No Implement Chlorination Strategy Chlorine Chloramine Chlorine Chloramine

46. Long Term Disinfectants Costs (0.5-Log Cryptosporidium)

47. Short-Term Implementation Elements Construct well-baffled chlorine contact basins Install emergency gas scrubbers Update chlorination equipment and controls Provide process monitoring and control for disinfection

48. Computational Fluid Dynamic Model T = 25 min.

49. Implementation Schedule Design/Construct Chlorination System Improvements Pilot Testing - Ozone Pilot Testing - Chlorine/Chloramine ESWTR Requirements Identified Design/Construct Long-Term Disinfection Improvements 1997 1998 1999 2000 2001 2002 2003

50. Denver Water Conclusions Post Filtration chlorine will meet disinfection and DBP requirements Study ozone and UV Wait for regulatory development Initiate revised disinfection based on regulatory requirements and study results

51. DBP Compliance Now and Into the Future Each case is site specific when balancing disinfection needs and DBP Chlorine, ozone, chlorine dioxide, and UV are all possibilities A thorough analysis and cost estimate is essential to a good decision