Compliance Strategies for Stage I & II DBPR 4 Case Studies

1. Compliance Strategies for Stage I & II DBPR4 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 StudyAurora 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. 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. Disinfectant Evaluation - Chlorine

5. 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. Disinfectant Evaluation - Chlorine Dioxide

6. Advantages Can provide 0.5-log inactivation of Cryptosporidium Strong oxidant – will help control Quincy T&O problems, and could eliminate KMNO4 and PAC system. Willreduce manganeseconcentrations though oxidation/filtration Application to raw water will providebenefit 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). Disinfectant Evaluation - Chlorine Dioxide (cont’d)

7. Master Plan Evaluation of Disinfectant Costs

8. Initial Demand and Decay Rate Determines ClO2 Dosage & CT 1 Area Under Curve Represents CT Achieved 0.9 Initial Demand 0.8 0.7 (mg/L) 0.6 0.5 2 0.4 ClO ClO Concentration Decay 0.3 2 0.2 0.1 0 0 5 10 15 Time (min)

9. Existing Contact Flocculation Basin Can Be Optimized for t10

10. Chlorine dioxide contactor modifications

11. Why Isn’t ClO2 More Common? • Until recently, minimal regulatory incentive to increase disinfection • Poor efficiency and performance of older style generators • Toxicology gaps for ClO2- and ClO3- • mclg for CLO2- was increased from 0.08 to 0.8 mg/L • No mclg for CLO3-

12. Aurora Conclusions • ClO2 can meet current disinfection requirements without construction of chlorine contact basin (saves $2.8 million) • ClO2 provides some taste and odor control

13. Conclusions (cont’d) • ClO2 can meet current disinfection requirements without chlorite control • Implementation of ClO2 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 SurfaceWater Treatment System FromNorthPlatteRiver Chlorine Alum Storage TransferPumping Floc/Sed Filters Raw Water Pumping Screens HighServicePumping Sludge Lagoons WashwaterLagoons To Distribution System

17. Upgraded Surface Water Treatment Process FromNorthPlatteRiver SO4 FeCl3 NaOCl NH4Ortho-PO4 Ozone HighServicePumping Actiflo Clarification OzoneContactor Filters Raw Water Pumping Settled Water Pumping Screens To Distribution System Sludge Lagoons WashwaterLagoons

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 NevadaUV Disinfection • Direct filtration plant • Chlorine disinfection for 1 log Giardia and 2 log virus inactivation DBP and Disinfection Drivers • Need to achieve 2 log Crypto inactivation • Future need for chloramines for THM and HAA control

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. 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” (-) Disinfectant Comparison

28. Ozone Relies on measurement of residual and hydraulic modeling to calculate CT Contactor design validated with tracer testing (t10) 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) Calculation of UV & Ozone Disinfection Performance

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/cm2 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. Recent Research Indicates Capability of UV for Cryptosporidium Inactivation 0 Excystation -1 Infectivity -2 After Clancy et al., 1998 [Demonstration Scale Testing] Medium-Pressure UV Lamp Log (N/No) -3 -4 -5 0 50 100 150 200 UV Dose, mW-sec/cm2

33. Recent UV Inactivation Data for Cryptosporidium • Clancy; 2.8 to 4.8 Log Crypto Inactivation Using 25 mJ/cm2 • Bolton; 3-Log Crypto Inactivation at 20 mJ/cm2 • Finch; 2.5 to 4.6 Log Crypto Inactivation Using 28 mJ/cm2 • Sobsey & Linden; 4-Log Crypto Inactivation Using 15 mJ/cm2

34. Giardia Inactivation Capability of UV • Previous Studies (Hoff, Karanis) Showed Doses of 100 to 180 mJ/cm2 Required for 2.0-Log Giardia Inactivation • Sobsey & Linden; 4-log Giardia Inactivation Using 15mJ/cm2 • Bolton; 3-log Giardia Inactivation at 20 mJ/cm2

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 Bacillussubtilis 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 WaterChlorine Disinfection • Conventional water treatment at 3 water treatment plants • Disinfection with chlorine followed by chloramines DBP and Disinfection Drivers • Need to reduce THMs and HAAs • Planning for future disinfection and DBP regulations

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

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

44. Yes BulkChlorine Gas Can risks be mitigated? Bulk chlorine $10.2M No Will chlorine meet short-term goals? On-site NaOCl generation $24.9M Yes Purchase NaOCI Purchase NaOCl $21.8M No Evaluate other disinfectants Short Term Planning

45. Long-Term Planning Meets DBPR Chlorine Chlorine Yes Conduct Ozone / UV Studies No Crypto Inactivation ImplementChlorination Strategy Yes Evaluate Performance of Chlorine Chloramine > 1.0 Log Crypto? No Ozone or UV Yes No Meets Criteria No Chlorine Chloramine Yes 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 1997 1998 1999 2000 2001 2002 2003 Design/Construct Chlorination System Improvements Pilot Testing - Ozone Pilot Testing - Chlorine/Chloramine ESWTR Requirements Identified Design/Construct Long-Term Disinfection Improvements

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