There are two primary chemicals used to purify water: iodine and chlorine.
Both are lightweight, low cost and easy to use.
Iodine has been proven effective in killing off viruses, bacteria and protozoa. However, the colder the water is, the more time it will take to purify with iodine.
Iodine can also absorb into the dirt and debris naturally found in water, so the dosage will always vary.
Also, pregnant women or those with thyroid conditions should not drink water with the chemical. Usually, iodine is just used for short-term purposes, and should not be used for more than three consecutive months.
Many do not favor the taste it leaves behind either. The unfavorable taste can be combated by mixing the water with a sugar-based drink mix, or better yet, by not using the method at all.
Chlorine bleach is the second chemical purifier.
The process of chlorination will cause dirt and debris to settle to the bottom of the water container and make the water visually clearer.
The American Red Cross endorses the brand Chlorox. The Red Cross states that people should use an unscented household bleach that contains 5.25% sodium hypochlorite.
When using bleach to purify, the recommendation is to add 16 drops of bleach per gallon of water, stir, and let stand for 30 minutes. If the water does not have a slight bleach odor, repeat the dosage and let stand another 15 minutes.
There are many drawbacks to the chlorination method. If the household bleach is over six months old, it may not have enough potency to disinfect. Also, chlorine is very poisonous and adding too much can cause illness, internal organ damage or even death.
Chlorine has been linked to many health problems. You can read about them in the health section of this site. Also, if one decides to use bleach, be sure to add it at the time intended to use the water, not when storing.
Seeing the drawbacks of these traditional filtration methods brings us to understand why more advanced water purification are required nowadays.
Advanced Modern Water Purification Methods
Water filtration by definition simply means to strain out the impurities from a water source. The larger the impurity particulate, the easier it is to filter.
The opposite is true: the smaller the impurity particulate, the harder it is to remove. Thus, the size of the filter pore and the durability of the filtering element are important to the filter's longevity and its ability to perform.
Most filtering elements are made of ceramic, glass fiber, hard-block carbon, or materials that resemble compressed surgical paper.
Some of the better purification methods include the activated carbon and reverse osmosis.
The best contribution that carbon makes to filtration technology is its ability to reduce chemical quantities, poor taste, odors and many pollutants. Because carbon is only mildly effective in filtering out particulates and microorganisms, it is mostly used as a second or third stage filter in home and portable water use.
It is seldom used as a stand-alone filtering, and often times, used in conjunction with reverse osmosis. Reverse osmosis, which uses a semipermable membrane filter to separate the water from contaminants.
Reverse osmosis is highly effective in removing several impurities from water such as [url=http://www.freedrinkingwater.com/glossary.htm#total dissolved solids]total dissolved solids[/url], turbidity,asbestos, lead and other toxic heavy metals, radium, and many dissolved organic.
The process will also remove chlorine, and can also remove nuclear radiation such as radioactive plutonium or strontium in the drinking water.
Therefore, reverse osmosis combined with activated carbon seems to be the most advanced water purification method developed so far.