Anyone can purify drinking water. People have been purifying water since the dawn of civilization. The Egyptian Sanskrit, written about 2000 B.C. directed people to “heat foul water by boiling and exposing to sunlight and by dipping seven times into it a piece of hot copper, then to filter and cool in an earthen vessel”. You only have to treat the water you and your family drink and use in food preparation. There are many ways to treat water and the unit you use should perform all or most of the following tasks: leave the water free of harmful bacteria, viruses, amoebic cysts, and other parasitic organisms, not breed and release harmful bacteria into the water, remove off-colors, odors, and tastes, remove sediment, remove microscopic asbestos fibers, remove chlorine, remove chloroform, remove organic chemical pollutants, remove harmful heavy metals, moderate or remove iron, manganese, or hydrogen sulfide, provide sufficient amounts of water to supply a family’s needs in a reasonable time, not consume large amounts of energy, and indicate when maintenance is required or when the useful life of the treatment unit is over. (Carol Keough, Water Fit to Drink: A Guide to the Hidden Hazards of Drinking Water and What You Can Do to Ensure a Safe, Good-Tasting Supply for the Home, 134) One way to filter water is a simple sand filter, which is much the same as those used by the ancient Egyptians. It is simply a column of sand or other porous matter that strains out particles from water. This kind of filter can remove clay, silt, colloids, and microorganisms, ranging in size from 1 millimicron to 50,000 millimicrons. Each bacterium and virus can be strained out of water, if the pores in the filter are small enough. The most widely used filters are sand filters in which 18-30 inches of sand are used, supported by a gravel layer about 6-12 inches thick. Slow sand filters are commonly used for pond water treatment because the cost is low and the effectiveness high, if they are properly cared for. Good maintenance consists of frequent backwashing to remove the accumulated dirt and scum on the top inch or 2 of sand. A slow sand filter can handle about 2 or 2.5 gallons of water per square foot of sand surface per minute. At the bottom of the filter is a drain which removes the cleansed water. It is simply a pipe punched with small pores to allow the passage of water. Constructing a Simple Filter To make this filter you will need a 55-gallon drum with a lid. First attach a drain faucet at the side near the bottom. Assemble your filter media and wash all of it to remove dirt and dust. Now put in 6-8 inches of gravel of sizes varying between 0.5 and 2 inches. Place 6 to 7 inches of activated carbon on top of the gravel. This will help support the sand on the next layer and keep it out of the drain. Between 27 and 36 inches of sand are needed. The sand used should consist of hard durable grains free of clay, loam, dirt, or organic matter. It should have an effective size of 0.20 to 0.40 millimeter (The effective size is the diameter of the grains in millimeters, which make up 90 percent or more, by weight, of the sand). This layer should be covered with 4 to 6 inches of gravel. The net result is that about two-thirds to three-fourths of the drum will be filled. Turbid water is poured into the top of the drum and filtered water comes out the bottom. Such a filter will become more efficient as it matures as the mat of turbid materials that builds up on the top layer promotes better filtration naturally. The thick layer of sand will help reduce bacterial levels considerably. Maturation comes in 15 to 17 weeks, and efficiency is maintained for another 6 to 100 weeks. Thereafter, the filter becomes saturated, the rate of flow slows down, and turbid matter bleeds through. At this point the filter content can be dumped, dried under the sun, dusted, and well rinsed. The carbon should be replaced, but the sand and gravel can be reused. Filtration can be furthered by distillation, a deionizing unit, reverse osmosis unit, or a GAC filter. (Keough, 135) Water storage Once water has been filtered and is ready for human consumption, it may be necessary to store the water until it is used. Water should be stored in a clean receptacle and should be tightly covered. It is important that animals are not given an opportunity to defecate in the water or have any contact with it. Animals can transfer diseases and bacteria to the water if they are allowed to come in contact with it. It is important that dirty utensils are not dipped into the water storage container to gather water. A system that makes it possible to retrieve water without dipping utensils into the storage container is preferred.