Quick Answer
You may need to add chemicals after filtering water to make it safe for drinking, especially if the filter doesn't remove all bacteria, viruses, or parasites, or if the water source is contaminated with heavy metals.
Chemical Disinfection
When using a water filter that doesn’t remove all pathogens, such as Giardia or Cryptosporidium, you’ll need to disinfect the water with chemicals like chlorine, iodine, or UV light. Chlorine is a common choice, as it’s effective against a wide range of pathogens. Use a solution of 2-4 milligrams of chlorine per liter of water for 30 minutes to 1 hour to disinfect. Iodine is also effective, but it can have a stronger taste and odor.
Water Disinfection Methods
There are two primary methods of water disinfection: chlorine and iodine. Chlorine can be added as a tablet or liquid, while iodine is usually added as a tablet. The World Health Organization recommends using 5 milligrams of iodine per liter of water for 30 minutes to 1 hour. However, iodine has a shorter shelf life and can be less effective against certain pathogens.
Improvised Water Disinfection
In a survival situation, you may not have access to commercial disinfection tablets or equipment. In this case, you can use solar disinfection (SODIS) to kill bacteria and viruses. Simply place the water in a clear plastic bottle and leave it in direct sunlight for at least 6 hours. The UV rays from the sun will disinfect the water. Alternatively, you can use boiling water to kill pathogens. Boil the water for 1-3 minutes at a rolling boil to ensure it’s safe to drink.
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