SEPARATION: FILTRATION & DISTILLATION WATER FILTRATION Water filtration is a form of separation which strains out, or separates, the impurities from a water source. The larger the impurity particulate (e.g., rust, sediment), the easier it is to filter. The smaller the impurity particulate (e.g., viruses), 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 ability to perform. Most filtering elements are made of ceramic, glass fiber, or hard-block carbon. Ceramic elements are the most expensive, most durable, and can be maintained (cleaned). They have the smallest pore size (0.1-0.5 microns) and are used by some of the leading portable water filtering companies in the world. Ceramic elements can filter only free floating particulates and microorganisms. They do not remove chemicals, poor tastes, odors, or pollutants. Glass fiber elements are mildly expensive, have medium durability, and usually are not cleanable. They have small pores (0.2-1.0 microns). Like the ceramic filter, they remove only particulates and microorganisms, but they do not help much with pollutants. These are good low-cost filtering elements for home, backpacking and scouting needs. They are not good for long-term storage because they can develop mold and mildew and are hard to clean. Hard-block carbon elements are less expensive, brittle, and not cleanable. They have a small, but still effective pore size (0.4-2.0 microns). They are also used as an absorption filter. The best contribution that carbon makes to filtering is its ability to reduce chemical quantities, poor taste, odors and many organic chemical 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 unit. WATER DISTILLATION Solar stills operate using a "greenhouse effect." A clear plastic barrier (a plastic bag, ground cloth, or a plastic grocery sack) is placed over a damp “source,” such as the ground (or a small hole dug in the ground), tree branches or other organic materials. The sun’s (solar) energy passes through the barrier and heats the source material. Moisture from the source evaporates, rises, and then condenses on the underside of the plastic barrier. The moisture is then collected as drinkable water. Solar stills are capable of distilling almost any tainted water, even seawater. Solar stills can condense drinkable water from almost anything that contains moisture. The only source materials that it cannot distill drinkable water from are materials that give off volatile toxins, such as fluids with high amounts of chemicals, radiator fluids, and fuels. Solar stills are easy to assemble and require only two essential components: 1) A container to catch the water, and 2) A large sheet of clear plastic (from 6’ x 6’ to 9’x 9’). Optional items include a long plastic drinking tube with an end cap, a small shovel, and duct tape. Solar stills are inexpensive to make and most of their component parts can be purchased at a hardware store. However, solar stills should not be your only method for Replaceing drinkable water during an emergency. This distilling process is extremely slow and only small amounts can be collected daily. A solar still is good when you have exhausted other methods. Caution: Do not use a solar still as your primary water source. It is not a substitute for carrying adequate amounts of water. Depending on your circumstances you will need from one half to one gallon per day per person. PLAN AHEAD TO COMBINE METHODS The most common pathogenic (disease-causing) microorganisms in untreated water are protozoa and bacteria. Normally viruses are not a problem in water in North America. However, in a disaster situation there is a possibility that water sources will become contaminated with viruses. Even the best microfilter system may not get all viruses out of water since those organisms are smaller than the smallest pore sizes available on microfilters. Protozoa take up to four hours to kill with Chlorine or Chlorine Dioxide (but they are removed with most filters). E.P.A. sanctioned testing at the University of Arizona Dept. of Microbiology showed that Chlorine Dioxide tablets will kill both bacteria and viruses within 15 minutes - even in cold, dirty water. The combination many experts now recommend when viruses may be present in water is first microfiltration, then chemical treatment. Only a 15 minute wait time is necessary, and as a bonus over other methods: 1. Dirty water will be cleaned up. 2. If the microfilter also has activated charcoal (carbon) in it, it is possible harmful organic chemicals may be removed. The two largest outdoor water filter companies, Katadyn® and MSR®, both approve of combining microfiltration with subsequent use of Chlorine Dioxide or Chlorine to remove or kill all microorganisms in water (including viruses). In conclusion, become aware of your area’s surrounding surface water and determine which methods work best to make that water safe to drink. Educate yourself to know what works, what doesn’t, and how you could get more drinkable water if needed. Combining methods can increase the safety of your treated water.
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