Pure Water

Purifying Water

Three things have to be removed from drinking water to make it safe: parasites, bacteria, and viruses. Some of this data comes from: "Medicine for Mountaineering", 4th ed., James Wilkerson, MD, The Mountaineers, 1992.

Boiling

Boiling kills all three. According to the CDC, once the water has started to boil, the bacteria and parasites are dead. They recommend boiling for another three minutes to kill viruses. Boiling is time consuming and requires a stove and additional fuel just for water treatment.

Iodine Tablets

Iodine tablets kill everything but cryptosporidium which is a tough skinned parasite. Use 1 tablet per quart unless the water is dirty or very cold then use 2. It takes about 15-20 minutes for the tablets to work, longer when the water is cold or dirty. Remember to partially unscrew the top, and turn the water bottle upside down to allow some of the treated water to seep through and around the cap threads. Iodine tablets provide a strong chemical aftertaste after using them for several days. Citrus drinks can be used to mask this taste but should be added after the iodine has had the required time to kill all the microcooties. Ascorbic acid interferes with how iodine chemically purifies the water.

Filter

Filtering is done with a ceramic filter with microscopic passages which will remove all but viruses which are too small for the filter to remove. Typical filter pores are on the order of 0.2um. Viruses have to be killed with iodine tablets or boiling. Filters can clog easily and depending on the design, may be difficult to clean. Try to use water where the silt or sand has already settled to the bottom.

Purifier

Purifiers are ceramic filters which have been impregnated with an Iodine compound. The filter mechanically removes the bacteria and parasites. Then the iodine kills any remaining viruses. This is the most effective treatment available. The amount of iodine is less than what you would get from a tablet and therefore the water tastes better. Desirable design features in a filter or purifier include: small size and weight, low force to use, easy to clean, field replaceable cartridge, and a high flow rate of treated water.