Geoscience Reference
In-Depth Information
ent, accurate, and easy to use. For disinfecting large quantities of water, their cost may be pro-
hibitive, but they are a lot lighter and easier to carry than gallons of pure water.
Caution:
Traditional chlorine tablets will not kill
Cryptosporidium
cysts.
Redi Chlor tablets, from Continental Technologies, are premeasured tablets of calcium hy-
pochlorite that are handy for disinfecting significant quantities of drinking water. Each tablet
treats 5 gallons of water, so a single bottle of 100 tablets treats 500 gallons of water for about
$19.95, which is far cheaper than the per-gallon cost of small purifying filters.
Granular Calcium Hypochlorite
Granular calcium hypochlorite is used for chlorinating swimming pools and fairly large quant-
ities of water and for making stock disinfectant solution. It is best stored in a garage or storage
building far enough away from other products, since it can cause pitting and corrosion. Granu-
lar calcium hypochlorite is packaged for sale in plastic bottles or drums. Sources of calcium hy-
pochlorite are hardware stores, sporting goods stores, pharmacies, chemical suppliers, and
swimming pool supply companies.
Caution:
Calcium hypochlorite is poisonous and extremely corrosive.
To make a disinfecting solution, dissolve 1 heaping teaspoon of granular calcium hypo-
chlorite (about ¼ ounce) for each 2 gallons of water. This will yield a concentrated chlorine
solution of approximately 500 milligrams per liter. To sterilize water, add this chlorine solution
in the ratio of 1 part chlorine solution to 100 parts of water to be disinfected (Le Baron 1998,
115). This is roughly equal to adding 1 pint (16 ounces) of concentrated chlorine solution to
each 12.5 gallons of water. If this seems unnecessarily complicated, use the Redi Chlor tablets
as described under “Chlorine Tablets.”
Iodine Disinfection
Iodine is one of the best and most dependable germicides and is widely used as a skin disinfect-
ant for the treatment of superficial wounds. You can use iodine to disinfect your drinking water,
and it is commonly impregnated into modern water filter media to kill bacteria and viruses in-
side water filters. However, iodine is not effective against
Cryptosporidium
cysts. Iodine-
treated water has a peculiar odor and taste that some people find unpleasant.
Caution:
Pregnant or nursing women, or people with thyroid problems, should not ingest
iodine-treated water. The EPA recommends that devices that add iodine to the water should not
be used for periods extending beyond two to three weeks at a time.
