Natural and Engineering Factors that Affect Disinfection Byproduct Concentrations in the Home - PowerPoint PPT Presentation

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Natural and Engineering Factors that Affect Disinfection Byproduct Concentrations in the Home

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  1. Natural and Engineering Factors that Affect Disinfection Byproduct Concentrations in the Home Boning Liu and David Reckhow Department of Civil and Environmental Engineering, University of Massachusetts, Amherst, MA 01003

  2. Let’s make some disinfection byproducts! Outline • Intro & DBP Issue • Factors affecting DBP formation • Information Gaps • Field Studies • Design • Municipal system • Home impacts • Conclusions

  3. Oxidized NOM • and inorganic chloride • Aldehydes • Chlorinated Organics • TOX • THMs • HAAs The THMs MCL 80µg/L Intro & DBP Issue The Precursors! HOCl + natural organics (NOM)

  4. Factors affecting DBP levels • Raw water NOM levels (e.g., TOC) • Specific precursor content of the RW NOM • NOM removal • Disinfection regime • type & dose • location in plant • contact time & temperature • pH • Degradation and formation in DS

  5. Activity Major Routes City Water Drinking Ingestion EPA regulation based Water Heater Showering & Washing Dermal & Inhalation Ingestion & Inhalation Beverage Preparation Human Exposure Food Preparation Ingestion & Inhalation Dermal & Inhalation Clothes Washing Dermal & Inhalation Dish Washing

  6. Inhalation in the shower produces highest blood level and response is fast Multiple Routes of Exposure Gordon et al., 2006 [Env. Hlth Persp.114:514-521]

  7. Regulated DBPs But, the Bad Stuff is probably somewhere here TOX: Known & Unknown Data from the Mills Plant (CA) August 1997 (courtesy of Stuart Krasner)

  8. What is the extent of diurnal variations in regulated and non-regulated DBPs? • In mains, near storage tanks, in dead ends • How does actual exposure compare to expectations from compliance testing? • Hot water effects(tankless vs. tank heater) • Non-regulated DBPs Key Study Questions

  9. d Case studies: Northampton, MA

  10. Relatively low TOC Historical Water Quality

  11. Recent DBP levels have dropped due to new WTP Historical Data(cont.)

  12. Intensive sampling over 2 days • Monitor cold water • Plant effluent: system entry • Distribution system location unaffected by storage and dead end • Monitor hot water • Measure regulated and non-regulated DBPs • THMs, HAAs, residual chlorine, temp • TOX, HANs, CP, TCP Field Study 1 Design

  13. Don’t try this at home Study #1 Design

  14. dsa Total transit time is around 18-30 hours Field Site #1

  15. Plant to Tap: Chlorine Residual

  16. Plant to Tap: TTHM

  17. Trihaloacetic Acids

  18. temp Monitoring Hot water

  19. Results-Hot vs Cold: TTHM

  20. Hot vs Cold: Dihaloacetic Acids

  21. Northampton, MA Hot vs Cold: Trihaloacetic Acids

  22. Percentage of Unknown TOX little changed • 50% for cold water • 45% for hot water TOX

  23. If TCAA decarboxylation isn’t the explanation, then what? Answer: Shift in reaction pathway for common THM/TCAA intermediate Alternative Explanation THMs TriHAAs Simplified from: Reckhow & Singer, 1985 [Water Chlorination: Environmental Impact and Health Effects, Vol 5, pp1229-1257.]

  24. Hot vs Cold: Dichloroacetonitrile

  25. DHAN • Key intermediate • Concentrations are well known

  26. Hot vs Cold: Trichloropropanone

  27. Northampton, MA Hot vs Cold: Chloropicrin

  28. Rocky Hill Cohousing Community, Northampton, MA • Uniform construction: completed 2005 • Study date: late July 2010 • 18 homes participated • 8 tankless gas heaters, 10 conventional tank heaters Field study 2Impact of heaters on DBP formation

  29. tankless heaters Field study 2Impact of heaters on DBP formation No storage tank On-Demand, save energy, how about Disinfection byproducts?

  30. 2 day sampling Temperature controlled Chlorine residual/pH measured at each site Samples quenched, cooled down and transported to lab for DBP analysis Simulated experiments Experimental Design

  31. Temperature Reading is after flushing when temperature is stabilized Hot Water: 50-60 C Cold Water: 18-22 C

  32. Tankless vS. Tank Heater(DHAA) Heavy water usage

  33. Delta value, ratio Tankless vS. Tank Heater(DHAA)

  34. Tankless vS. Tank Heater(THAA)

  35. Tankless vS. Tank Heater(THAA)

  36. Tankless vS. Tank Heater(TTHM)

  37. Tankless vS. Tank Heater(TTHM)

  38. Conclusions & Next Steps • Water Heaters substantially change the DBP levels and character • Some increase many fold • THMs, DiHAAs, Chloropicrin • Some show little change • TriHAAs • Some decrease • Dichloroacetonitrile, Trichloropropanone • For most, we simply don’t know • Tankless heaters have a smaller affect • High temperatures shift reaction pathways • TriHAA→THM • Other products formed? • What does this mean to exposure studies? • Need to look at other DBPs and develop models • Hypothesis: DBP increase is related to chlorine residual at time of heating

  39. Northampton (MA) DPW - Water Division • David Sparks, superintendent • Alex Roseweir, Doug Ducharme, Paul Petersen • Northampton Rocky Hill cohousing community • 18 anonymous home owners Acknowledgements

  40. Dichloroacetonitrile

  41. Choropicrin

  42. Total Chlorine Residual Lab-incubated samples • Mixed cold water from cohousing homes, incubated at 53oC(average T of hot tap) • Incubated water effluent from water treatment plant

  43. Lab incubated samples(cont.) DHAA TTHM Immediately 53oC THAA

  44. TCAA Degradation kinectics pH=6.7, temperature 60oC, TCAA standard solution. Calculated K=( 0.0169 +/- 0.0025 )/hr

  45. The Haloacetic Acids MCL: 60µg/L

  46. Less than with the hot tap THM Terminal

  47. Little difference between hot and cold DiHAA Terminal

  48. Higher terminal levels in cold tap TriHAA Terminal