Water Purification Chemicals
Water purification chemicals, while not critical, are a fast and convenient way to make water safe for human consumption. There are many different chemicals that can used to purify water, each with their own pros and cons. Chemicals also come in both liquid and tablet form. Typically tablets are easier to use while liquids are stable for longer periods of time and provide greater purification capacity from a smaller volume of the chemical being used. Many people turn to chemicals for water purification because, unlike microfiltering, boiling, or ultraviolet treatment, chemical treatments are residually effective, meaning that once purified, they will remain pure even if new pathogens are introduced.
It is, however, important to note that chemical treatment only kills pathogens, it does nothing against other chemical impurities. Chemical treatment will do nothing to reduce the amounts of heavy metals, radioactive isotopes, or toxins dissolved in water. Because of this, many people stock a water filter to use in conjunction with chemical treatments.
Types of Chemicals
Chlorine is a commonly used chemical, particularly in commercial kits. It is often in the form of "Halazone", which has become less popular in the United States. Chlorine is also found in bleach (sodium hypochlorite) which has been recommended by FEMA as a means of sterilizing water in an emergency. It should be noted that while bleach is an effective sterilizer, its effectiveness is degraded by organic material in the water, it is less effective at lower temperatures, and it "outgasses" from open containers rather quickly.
To use, most manufacturers recommend that you eliminate as much particulate matter and organic solids from the water as possible. To do this, either filter the water through a high thread count cloth (some backpackers use bandannas), run it through a commercial water filter, or allow the particulate matter to settle and then decant the now clarified water into a new container.
If using chlorine tablets designed to treat water, simply use according to the manufacturer's instructions. If using household bleach (remember to use unscented!), the usual protocol is two drops of bleach per quart or liter of water. Shake or stir this and let it sit for at least ten minutes with half an hour being better. Smell the water. If it has a slight chlorine scent, the water is now potable. If not, add two more drops and repeat the stirring and waiting process.
Chloramine has been displacing chlorine in municipal water treatment facilities as it is more stable than chlorine, remains in water longer, and it is less adversely effected by organic materials. However, it is toxic to fish and some other animals. Chloramine is an emergent technology in the water purification field, and as of summer of 2008 there is no chloramine commercially available in major camping stores or swimming pool supply outlets. However, a patent was recently filed for chloramine tablets, so this technology should be out soon.
Iodine is a very popular chemical for water purification, it is extremely stable and effective. Many people find that water purified with iodine has an unpleasant taste and as a result many water purification kits that use iodine also include chemicals to remove this taste. Iodine designed for water purification is almost always sold in tablets.
To use, simply follow the instructions on the bottle of tablets. Most instructions are similar to the use of chlorine.
Comparison of Chemicals
Because of chloramine's status as emergent technology, the only two major options available for home use are chlorine and iodine. For health and price reasons, it is often better to use chlorine rather than iodine if you plan on using it for all potable water (like in a bug out scenario).