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Chlorination of Drinking Water PowerPoint Presentation
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Chlorination of Drinking Water

Chlorination of Drinking Water

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Chlorination of Drinking Water

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  1. Typhoid 1880 1900 1920 Chlorination of Drinking Water Uses - Disinfection • 1908 began •  cholera, typhoid • - water borne diseases • Saved millions of lives • Side products now of concern

  2. Disinfection Processes • Chlorination • Chlorine • Chloramine T • Bleach • Bromination • Iodination • Ozone • U.V. • Radiation • Silver Salts

  3. Chlorination Process Chlorine Gas (Cl2) Chlorine Dioxide (ClO2) Bleach (sodium hypochlorite) Chloramine T (ammonia + chlorine)

  4. Humic Substances Fulvic Acid Humic Acid Humin Light Yellow Dark Grey Black Yellow Brown Brown Black Water Components Water Color - Decaying Organic Matter - Surface Water/Some Groundwater • Treated by Chlorination

  5. Chlorination Water Chlorination - Organic Residue Cl2+ NOM  CHCl3+ THM + Other NOM = Natural Organic Material THM = CHCl3, CHBrCl2 CHBr2Cl, CHBr3 Other = di, trichloroacetic acids chlorinated ketones di, trichloroacetonitrile

  6. THM Production THMs …... ..…... .…... …... ..…... .…... .…... …... ..…... .…... …... …... .…... .…... …... …... ..…... .…... …... ..…... .…... …... Nonvolatile Organic Carbon Trihalomethanes Haloacetic Acids Haloacetonitriles Haloketones Other (>100)

  7. Time Table 1908 Chlorine Disinfection - U.S. 1974 THMs - Netherlands - New Orleans 1975 EPA - 80 cities THMs - Widely Present Relate to Chlorination 1977 Confirmed, Other Products Identified 1980s THM Remain Predominant Form Mean THM - 36-39 µg/l (ppb) Mean Haloacetic Acid - 17 µg/l (ppb) 1990 Reduce Excessive Chlorination Use Chloramine T

  8. X X C H X Cl Br Cl C H H Br C Cl Br THM

  9. THM (Chloroform) Toxicity • Chloroform • - anesthetic • - “syrups” • Liver, Kidney Toxicity • Biotrans • CHCl3 CHCl3*  Macromolecules • Cancer - Animals • - lifetime exposure • - every day, high levels • - liver, kidney, lung Cancer   Toxicity

  10. THM Toxicity II THMs - Bromo Compounds CHBr3~ CHCL3 Liver Toxicity CHBr3~ ? CHCl3 Cancer Haloacetic Acids Cancer, Co-Carcinogen 60 µg/l (ppb)

  11. Disinfection Products/Toxicity Trihalomethanes Chloroform Cancer, Human CHBrCl2 Cancer, Human CHBr2Cl Liver CHBr3 Cancer, Human Haloacetic Acids Trichloroacetic Liver Dichloroacetic Cancer, Human

  12. THM Standard • 100 µg/l (ppb) - finished water • Reduce to 50 µg/l • In Discussion • Recheck Water Utilities • - mean 38 µg/l (same as prior) • Cost vs real health benefits • 100 µg/l  80 µg/l December 2001

  13. THM Cancer Epidemiology I • 1997 K.P. Cantor, NCI - Epidemiology • Epidemiology Studies (1977  1997) • 1st-Ecological - Epidemiological (1977) • - Water source - surface • - Mississippi River • - Water supply characteristics • - Bladder, colon, rectal cancer • - descriptive • 2nd Case - control mortality records • - water exposure variables • - cancer bladder, colon, rectum • - brain • - strengthen hypothesis, but limits

  14. THM Cancer Epidemiology II • 3rd - Colon, Rectal Cancers • - lack consistency, source unclear • - variations from state to state • - geographic differences in byproducts? • 3rd - Bladder Cancer • - more consistent • - all associations positive • - correlate to duration exposure • 4th - Regard results with concern • - need better link to • - by products mixture • - individual’s characteristics

  15. THM - Birth Outcomes • Trichloroethylene - South Tucson • - birth defects • Chloroform - Birth Defects • - Schuetz • THMs • - still births • - birth defects • Probably More Important • > cancer

  16. Risk - Cost Benefit • Chlorination/Disinfection • -  water borne disease • - save million(s) of lives • Chlorination Byproducts • - link to cancer? • - can “control” quantity byproducts • Efforts/Cost to Further Reduce Byproducts • Animal Models vs Humans • - cancer site vs animals • - concentration required • Birth Effects • - concentrate efforts • - difficult to study • Extraneous Factors • - other chemicals • - diet changes