Purifying Water

Objective  Learn techniques and identify material needed to purify water

NOTE: Only equipment marked "Purifier" will safely treat water.  Equipment  labeled as "Filters" do not do a complete job of removing harmful substances.

Equipment - There are several types of commercially available water purification systems

Whole house systems - require water pressure from your water utility company.  During a period when local government warns you to boil water, be sure your system is rated as a "Purifier" and not just a "Filter"

Faucet Mounted - These screw on to the faucet.  Check label ensure they are rated as "Purifiers"

Home use gravity drain - These are large volume (2 to 5 gallon) counter top units that have 3 to 5 filters.  Water is dispensed from bottom after passing through purification system.

Portable -  These range from simple water bottles with internal filters, filtration "straws" and small hand pump units.  There are also a few larger volume back pack units that use a gravity drain from one container to another.  For personal use, the "water bottle" type is preferred since there are no moving parts to break. 

Water Purification WARNING Notes:

Giardia cysts are very difficult to remove from water.  Water must either be be boiled or filtered with a 1micron or smaller filter. Chlorine does not kill Giardia. Giardia is present in the fecal of animals. Giardia infection causes a high fever.

Chlorine levels above 4ppm will harm your digestive system and higher levels can cause death. Be sure to test the level of chlorine present in the water before used for drinking.

BE SURE to understand and follow all hazards and precautions on chemical container labels

 

Purification ABCs - if normal purification systems are not available

1. Clean Food-Grade Containers are required
   Clean the containers in which you're going to hold or store the water. Use dish soap and water. Rinse thoroughly. After washing them, submerge them in a solution of 1 teaspoon of non-scented liquid household chlorine bleach to every quart (or liter) of water (making sure the entire surface of the bottle comes in contact with the solution for a minimum of 15 seconds), and then rinse thoroughly with a weaker mixture of bleach and water.
    

   • Don't use any container that has had milk or fruit juice in it. Milk protein and fruit sugars remain in the container and can fuel bacterial growth when water is stored. Plastic soda bottles are suitable.
      

2. Filter the Water to Remove Suspended Particles, Chemicals and Heavy Metals.
   If the water is very cloudy, let it stand for about 30 minutes to allow particles to settle. The settling step is especially important if you're going to be using chemical purification because disinfectants are less effective in cloudy, murky, or colored water.  Use a hose to siphon off the clear water into another container for filtering.
   
   Your filtering apparatus will depend on your preparation.  There are numerous commercial water filters available from small camping units to pour-through 3 liter household types.  Be sure to follow manufacturer's instructions.  If you live near the ocean, consider a portable desalinization unit.
    

3. Purify the Water to Kill Bacteria and Microbes
   After filtering, using any of the following methods. If you can, combine boiling with a chemical disinfection method.  Boiling is more thorough, and the chemical method will continue to keep the water safe when it's stored.
    

   • Boiling kills disease-causing organisms and is the most recommended purification technique. Boil the water for at least 5 to 10 minutes, then let it cool. Make sure it's a full, rolling boil. If you are more than one mile above sea level, boil 3 minutes longer.
      

   • Bleach.  Disinfecting with unscented household bleach kills some, but not all, types of disease-causing organisms. The bleach must contain chlorine in order to work. Don't use scented bleaches, color-safe bleaches, or bleaches with added cleaners. Neither chlorine (e.g., bleach) nor iodine alone is considered completely effective against Cryptosporidium, although they are partially effective against Giardia. Iodine should be allowed at least 30 minutes to kill Giardia. Chlorine is considered slightly better than iodine against Giardia. A more complete field solution that includes chemical disinfectants is to first filter the water, using a 0.2 micron ceramic cartridge pumped filter, followed by treatment with iodine or chlorine, thereby filtering out cryptosporidium, Giardia, and most bacteria, along with the larger viruses, while also using chemical disinfectant to address smaller viruses and bacteria that the filter cannot remove. Most household chlorine bleaches have 4-6% available chlorine, in which case you should add 1/8 teaspoon (8 drops) of regular, unscented, liquid household bleach for each gallon of water (2 drops per Liter), stir it well and let it stand for 30 minutes before you use it. Check the label; if the percentage of available chlorine is around 1%, or you don't know what the percentage is, use 40 drops per gallon/ 10 drops per Liter; if the percentage is 7-10%, use 4 drops per gallon or 1 drop per Liter. Double the amount of chlorine if the water is cloudy, murky, or colored, or if the water is extremely cold. If after sitting covered for 30 minutes the water doesn't have a slight chlorine odor, repeat the dosage and let sit for another 15 minutes.  Liquid bleach has a manufacturer recommended shelf life of 4 to 6 months
      

   • Granular calcium hypochlorite works in the same way as household bleach. You can dissolve one heaping teaspoon of high-test granular calcium hypochlorite (about 1/4 ounce) in two gallons of water (1 heaping tablespoon for

 

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