Disinfection

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Disinfection methods in water treatment process.

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Disinfection

  1. 1. Anup Ghimire Rock Face Limited
  2. 2. Common microorganisms in water  Bacteria such as E.coli, leptospira species, salmonella species, shigella and vibrio chollrae
  3. 3. Common microorganisms in water  Protozoa such as Balantidium coli, Cryptospiridium parvum, Entamoeba histolytica and Giardia lambia
  4. 4. Common microorganisms in water  Helminths such as Ascaris lumbricoides, T. solium and Trichuris trichuria
  5. 5. Common microorganisms in water  Viruses such as Entero viruses, Hepatitis A virus and Rota virus
  6. 6. Water treatment  Conventional methods of water treatment can’t remove some pollutants concentrations in water. persistent at lower
  7. 7. Water treatment  Disinfection process removes microorganisms from drinking water.  Ozonation, Chlorination and UV-radiation are effective disinfection methods.
  8. 8. Ozonation  Ozone is highly corrosive and toxic colourless gas and powerful oxidant capable of oxidising organic and inorganic compounds in water.
  9. 9. Ozonation  Ozone is formed by combining an oxygen atom with oxygen molecule (O2).
  10. 10. Ozonation  Ozone reacts with substrate or organic and inorganic compounds by direct oxidation and oxidation of compounds by hydroxyl free radicals.
  11. 11. Ozonation: applications  Bleaching process  Drinking water treatment such as improvement of flocculation, removal de coloration, taste/odour
  12. 12. Ozonation: applications  Waste water treatment processes such as elimination of tensides, phenols, COD, cyanides and sludge reduction.
  13. 13. Ozonation: applications  Process water such as cooling water, swimming pools and product polishing such as chemical modification of food and shelf-life improvement of food.
  14. 14. Ozonation: applications  Water treatment process to remove bacteria, viruses, organic and inorganic pollutants and hazardous chemicals.
  15. 15. Ozonation: applications  Ozonation process is also applied in the treatment of waste water contaminating milk and chemically treated municipal wastewater. physico-
  16. 16. Ozonation  Ozone attacks bacterial membrane either through the glycoproteins or glycolipids or through certain amino acids and ozone reacts with nuclear material affecting pyrines and pyrimidine in nucleic acids.
  17. 17. Ozonation  Ozone acts on viral capsid to inactivate viruses and high concentration of ozone dissociates the capsid completely.
  18. 18. Ozonation  Ozone inactivates RNA and DNA of the viruses.  Protein capsid is affected by ozone attack which releases nucleic acid and inactivates DNA.
  19. 19. UV radiation  Disinfection from UV radiation removes organic compounds.  No production of compounds (VOCs). odour and volatile organic
  20. 20. UV radiation  Improves taste of water.  Do not require storage of hazardous waste and requires minimal space for treatment.
  21. 21. UV radiation  Growth and reproduction of micro-organism is inhibited by UV light induced genetic material disruption.
  22. 22. UV radiation  UV light is capable of penetrating microbe’s cell wall without producing toxic side effects.  Optimum wave length requirement to destroy bacterial activities lies between 250nm to 270nm.
  23. 23. UV radiation  Special lamp to produce a spectrum of radiation is used in disinfection process.
  24. 24. UV radiation  Presence of high levels of suspended solids, turbidity, colour and soluble organic matter creates unsuitable environment for UV-radiation disinfection process.
  25. 25. UV radiation  Dose Requirement is crucial in UV radiation process. Required level of radiation dose to disrupt and destroy microorganisms must be maintained for the effectiveness.
  26. 26. UV radiation  Radiation concentration, proper wavelength, exposure time, water quality, flow rate, the micro-organism’s type, source and its distance from the light source determine the effective dose requirement.
  27. 27. Chlorination  In Chlorination process, hypochlorous acid acts as disinfecting agent. Hypochlorous acids are formed when chlorine hydrolizes in water. When hypochlorous acids splits into H+ and OCl- ions, bacteria and viruses are inactivated and enzymatic activities are inhibited.
  28. 28. Chlorination  Chlorine has a higher degree of persistence in water distribution systems.
  29. 29. Chlorination  Chlorination can be applied in drinking water operations such as treatment of ground water, industrial process water, chilling water, cooling tower systems, drip irrigation systems.
  30. 30. Chlorination  In the chlorination process, chlorine has two forms in water: free chlorine and combined chlorine. Sodium hypochlorite or chlorine gas produces free chlorine when added to water. When free chlorine and ammonia reacts, combine chlorine is formed which includes monochloramine and dichloramine.
  31. 31. Chlorination  Gaseous chlorine, chlorinated lime, sodium hypochlorite and calcium hypochlorite are chlorinerelated compounds for water disinfection.
  32. 32. Chlorination  Chlorine gas (Cl2) is highly toxic and liquefied under pressure.  Chlorinated lime (CaO2CaCl2O3H2O) is corrosive dry white powder.
  33. 33. Chlorination  Sodium hypochlorite (NaClO) is corrosive and yellowish liquid solution, commonly called “liquid bleach” and calcium hypochlorite (Ca (ClO)24H2O) is corrosive inflammable powder or granules and tablets.
  34. 34. Chlorination  Sodium hypochlorite (NaClO) produces hypochlorous acid (HClO) and hypochlorite (ClO-) ions, in water which affects bacteria and viruses by inactivating and inhibiting enzymatic activities.
  35. 35. Chlorination  Sodium hypochlorite affects biological functions of proteins and produces deleterious effects on DNA.
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