Chemical Disinfection

Chemical disinfection is the most widely used method of disinfecting drinking-water.

Chlorine Compounds 

  • Household bleach (sodium hypochlorite)
  • Sodium dichloroisocyanurate tablet
  • Calcium hypochlorite

How to use to Treat 1L of Drinking-water: 

  • For typical room temperature and water temperature of 25°C (77°F), minimum contact time should be 30 minutes. Contact time needs to be increased for colder water; e.g. one hour for temperatures less than 10°C
  • Prepare tablets according to package instructions
  • Household bleach (5%) - 4 drops per 1L water
  • Sodium dichloroisocyanurate - 1 tablet per package instructions; 15mg per 1L of clear water.
  • Calcium Hypochlorite (1%) - 4 drops per 1L

Can Treat: 

  • Kills most bacteria and viruses
  • Longer contact time required to kill Giardia cycts - especially when water is cold
  • Not effective against Cryptosporidium

 

Iodine  - not recommended for pregnant women, or for more than a few months continuous use

  • Tincture of iodine (2% solution)
  • Iodine (10% solution)
  • Iodine tablet
  • Iodine resin

How to use to Treat 1L of Drinking-water:

  • For typical room temperature and water temperature of 25°C (77°F), minimum contact time should be 30 minutes. Contact time needs to be increased for colder water; e.g. one hour for temperatures less than 10°C
  • Prepare tablets according to package instructions
  • Tincture of iodine (2%) - 5 drops per 1L
  • Iodine solution (10%) - 8 drops per 1L
  • Triiodide or pentaiodide resin - per package instructions

Note: Carbon filter should be used to remove excess iodine after iodine treatment

Can Treat:  

  • Kills most pathogens
  • Longer contact time required to kill Giardia cycts - especially when water is cold
  • Not effective against Cryptosporidium

 

 

For Further Information:

WHO Water Quality Guidelines - 4th Edition

WHO Water Treatment Guidance

WHO How to Make Drinking-water Safe