PURIFICATION OF WATER at household 4m*

  1. Boiling: 
    1. Very effective method of purification
    2. Boiled or rolled over for 10-20 mins
    3. Taste is slightly altered but harmless
    4. Care should be taken for vessels during storage as there is chance of contamination
    5.  It kills bacteria spores, cysts, ova and also removes temporary hardness by removing carbon dioxide and precipitating calcium carbonate.
  2. Bleaching powder
    1. It contains about 33% of “ active chlorine”
    2. It’s a unstable product
    3. To make it stable = excessive alum is added = chlorinated lime 
    4. On exposure to environment leads to loss of active chlorine
    5. It should be stored in dark and dry place 
    6. It gives pungent smell = hence not routinely used
  3. Chlorine solution:
    1. Prepared from 4 kgs bleaching powder in 20 liters of water
    2. 25% of activate chlorine
    3. But evaporates in the environement = stored in dark, dry and cold place
  4. High test hypochlorite
    1. Calcium compound containing 60 to 70% active chlorine. 
    2. It is stable than bleaching powder and less deterioration 
  5. Chlorine tablets
    1. Available readily in the market
    2. under various trade names like halazone tablets. 
    3. Very economical = formulation used currently was developed by NEERI, nagpur 
    4. 0.5 gm of chlorine tablet for 20 liters of water
  6. Iodine
    1. It is used for emergency disinfection of water. Why?
      1. highly expensive
      2. physiological activity with respect to thyroid
    2. Two drops of 2% ethanol solution of iodine will be sufficient for one liter of clear water 
    3. for a contact period of 20 to 30 min for effective disinfection.
    4. Remains active for longer time 
  7. Potassium permanganate:
    1. This was widely used,but now no longer recommended for water disinfection.
    2. Effective against vibrio cholera but not against other pathogens 
    3. It also alters the color, taste and smell of water.
  8. Filtration
    1. On a small scale, water can be purified by using THREE TYPES OF filters
    2. PASTEUR CHAMBERLAND FILTER = made up of percelian 
    3. BERKEFELD FILTER = made up of kieselguhr or infusorial earth. 
    4. KATADYN FILTERS = silver coating on filters = when bacteria touch silver- it dies due to oligodynamic effect
    5. Heart of the filter is = candle = ONCE PER WEEK 
    6. Wash it under running water using hard brush followed by boiling = to remove impurities clogging the filters 

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