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Safety of potable water

Safety of potable water. FS0104 1. 2000. Demand for water. Some compelling statistics. human water use has increased more than 35-fold over the past three centuries.

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Safety of potable water

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  1. Safetyofpotablewater FS0104 1 2000

  2. Demandforwater Some compelling statistics • human water use has increased more than 35-fold over the past three centuries • per capita water consumption in North and Central America is twice that of Europe, three times that of Asia and seven times that of Africa • about one billion people in developing countries do not have access to potable water • unsafe water, along with food, is implicated in 3 million deaths about 2.4 billion episodes of illness per year • the world's population, now 5 billion, is expected to increase to 8 billion by 2025 and 10 billion by 2050. This means that demands for water and food will also increase. FS0104 2 2000

  3. Watersafety amatterofpublicconcern Water quality ‹ strictly regulated ‹ an important public health indicator ‹ standards are becoming more rigorous FS0104 3 2000

  4. Hazardsinwater Surface water ‹acid rain ‹ storm water runoff ‹ pesticide runoff ‹ industrial waste FS0104 4 2000

  5. Hazardsinwater Ground Water ‹disease-producing pathogens ‹leachate from landfills and septic systems ‹ hazardous household products ‹ agricultural chemicals ‹ leaking underground storage tanks FS0104 5 2000

  6. Waterbornepathogens These organisms cause most waterborne infections ‹bacteria ‹ viruses ‹ parasites FS0104 6 2000

  7. Waterbornepathogens Bacteria • Shigella spp • Pathogenic Escherichia coli • Vibrio cholerae • Campylobacter jejuni • Salmonella typhi Viruses • Adenoviruses • Enteroviruses • Hepatitis A & E • Norwalk virus • Rota virus • Small round viruses Parasites • Giardia intestinalis • Cryptosporidium parvum • Entamoeba histolytica FS0104 7 2000

  8. Toxinsassociatedwith Cyanobacteria • hepatoxins (induce death by circulatory shock and liver haemorrhage) • neurotoxins • lipopolysaccharides FS0104 8 2000

  9. Othersourcesofcontamination indrinkingwater • corrosion or deposits on pipes and storage tanks, caused by iron and sulfur bacteria • colonisation by microorganisms of non-metallic pipe-fittings, joints, lining • microbial growth in distribution systems, encouraged by the presence of organic carbon in the water • infestation of water mains by animal life FS0104 9 2000

  10. Characteristicsof waterbornepathogens • ‹ pathogens are discrete and not in solution • ‹pathogens are often clumped, or adhere to solids in water; thus, the likelihood of acquiring an infective dose cannot be predicted from their concentration in water • ‹the likelihood that the pathogen will cause an infection dependson itsinvasiveness and virulence, and the immunity of the individual • ‹ pathogens multiply in their host FS0104 10 2000

  11. Categoriesofchemicalcontaminants indrinkingwater • toxic organic chemicals • toxic inorganic chemicals • radioactive elements. FS0104 11 2000

  12. Toxicorganicchemicals • Trihalomthanes (THMs) • Pesticides herbicides insecticides fungicides • Volatile organic chemicals (VOCs) FS0104 12 2000

  13. Toxicinorganicchemicals • arsenic • barium • Cadmium • Chromium • Lead • Mercury • nitrate • silver FS0104 13 2000

  14. Radiologicalaspectsof drinkingwaterquality • environmental radiation originates from natural and man-made sources • radionuclides occur naturally in drinking water • drinking water is not a significant source of exposure to radionuclides FS0104 14 2000

  15. Ensuringwaterquality Focus of water quality assurance programs ‹ selection and protection of sources ‹ treatment process ‹ distribution networks FS0104 15 2000

  16. Protectingwatersources -isolation or protection of the watershed - control of polluting activities in the area - protection of springs, wells and ground water - control or prevention of public access FS0104 16 2000

  17. Watertreatment Treatment of urban water ‹pre-disinfection ‹ coagulation, flocculation, sedimentation ‹ filtration ‹ disinfection FS0104 17 2000

  18. Controllingthedistribution system - deterioration of underground reservoirs - back siphonage of contaminated water, due to loss of pressure - microbial growth, especially on lining materials and plastics - corrosion of tanks, pipes, valves and pumps FS0104 18 2000

  19. Assuringdrinkingwatersafety: generalconsiderations -compliance with existing guidelines - monitoring to ensure continued compliance - having adequate contingency plans in place to be used in emergencies FS0104 19 2000

  20. Summary - Only a small percentage of the earth's water is available for drinking - Demand for safe water is increasing - Microbial contamination (by bacteria, viruses, parasites, algae) is the most serious problem - Tolerable Daily Intake levels (TDIs) have been established for chemical contaminants - Water quality assurance efforts should focus on: selection/protection of sources, treatment, distribution - Compliance with WHO guidelines on drinking water quality should assure a safe water supply FS0104 20 2000

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