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Water Purification

Water Purification

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Water Purification

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  1. Water Purification

  2. Waterborne Enteric Pathogens

  3. Infectious Dose Organism Minimal infectious dose Salmonella 105 V cholera 103 Shigella 10 Cryptosporidium 30 Giardia 10

  4. Viability of Enteric Pathogensin Cold Water Organism Survival V cholera 4 – 5 weeks Campylobacter 3 – 5 weeks Viruses 17 – 130 days Giardia 2 – 3 months Cryptosporidium 12 months

  5. Infection Signs/Symptoms Diarrhea Gas/flatulence Greasy stool Stomach, abdominal cramps Upset stomach Nausea Dehydration Symptoms appear on average 7 days after becoming infected, last 2-4 weeks depending on immune system of host

  6. Water Source

  7. Water Source Lake or Stream? ?

  8. Field Water Treatment Methods • Heat • Clarification Sedimentation Coagulation/flocculation Granular activated charcoal • Filtration • Chemical disinfection Chlorine Iodine Chlorine dioxide • Ultraviolet

  9. Water Disinfection by Heat • Advantages Reliable Simple Widely available Sterilize Not dependent on water quality • Disadvantage Limited by fuel supplies Does not improve taste or appearance of water

  10. Thermal Death Points • Giardia, E histolytica cysts 2-3 minutes at 60º C (140º F) • Cryptosporidium oocysts 2 minutes at 64º C 1 minute at 72º C • Enteric viruses Seconds at 80º -100º C • Hepatitis A 1 minute at 85º C • Enteric bacteria 1 minute at 65º C Seconds at 100º C

  11. Effect of Altitude Elevation Boiling Point 5,000 ft (1524 m) 95º C (203º F) 10,000 ft (3048 m) 90º C (194º F) 14,000 ft (4267 m) 86º C (187º F) 19,000 ft (5791 m) 81º C (178º F)

  12. Water Disinfection by Filtration • Advantages Simple process No taste imparted Many choices May improve appearance of water • Disadvantages Special equipment adds weight to pack May not remove all viruses Gradual clogging

  13. Effective Filter Pore Size Organism Maximum pore size (um) Parasitic eggs and larvae 20 Giardia, E histolytica 5 Cryptosporidium 1 Enteric bacteria 0.2-0.4 Viruses 0.01

  14. Halogen Disinfection • Advantages Inexpensive and widely available Flexible dosing and equal ease with large and small quantities • Disadvantages Potential toxicity Limited effect on Cryptosporidium Imparts taste and odor • Sensitivity of microorganisms Bacteria > Viruses > Protozoan cysts

  15. Variables for Halogen Disinfection • Primary Halogen concentration Contact time • Secondary Temperature Water contaminants pH

  16. Iodine Contraindications Known iodine allergy Thyroid disease Pregnancy

  17. Improving Taste of Halogens • Decrease dose, increase time • Remove halogen Granular activated charcoal • Chemically remove taste Ascorbic acid Sodium thiosulfate Hydrogen peroxide

  18. Iodine Resins • “Demand” disinfectant Iodine molecules on resin transfer to organisms on contact Minimal dissolved iodine • Various filter designs combine Microfilter for resistant cysts Iodine resin for bacteria and viruses Charcoal to remove residual iodine

  19. Chlorine Dioxide At least as effective as chlorine for bacteria and more effective for viruses and Cryptosporidium Controls/eliminates some odor, tastes, manganese and iron Less affected by pH and ammonia nitrogen Available in liquid or tablets

  20. Miox PurifierMixed Species Disinfectant On-site production of mixed species disinfectants and oxidants Uses battery current (electrolysis) to convert brine solution (table salt) Generates mixed species includes free chlorine, chlorine dioxide, ozone, hydrogen peroxide, oxidants)

  21. MIOX PEN

  22. Ultra Violet Rays • Advantages Effective against all microorganisms Leaves no taste Extra dosing is not harmful, it is safety factor Battery operated units available • Disadvantages Requires power source Only works in clear water Moderate cost No residual disinfectant action

  23. EPA Testing for Microbiologic Water Purifiers 6-log reduction of bacteria 4-log reduction of viruses 3-log reduction cysts (Cryptosporidium) Testing at 20º C and 5º C Worse case scenario—high pollution, turbidity

  24. Susceptibility of Microorganisms to Field Disinfection 1 General Ecology First Need and Sawyer Purifier claim virus removal 2 Cryptosporidium is highly resistant

  25. Optimal Techniques • Single step Heat Chlorine dioxide Ultraviolet • Combinations 1.) C-F followed by halogenation or 2.) Halogenation followed by filtration (filtration last if charcoal matrix)