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The Best Ways to Filter Water Naturally

Our world brims with large natural water filters calls aquifers. Aquifers typically contain sand, rock, sediment and other materials that filter bacteria and other contaminants from water. Scientists first learned how to filter water from studying these natural formations. Today, water purification usually involves a cocktail of potent chemicals and mechanical filtration systems, but a number of viable natural filtration options still exist.

  1. Slow Sand Filtration

    • Slow sand filtration is a simple and inexpensive method of filtering water. These filters comprise a gravel layer at the bottom of a tank followed by layers of coarse sand and fine sand. Such filters should be at least 39 inches deep with a minimum of 27 inches of sand. They filter water at about 0.15 gallons per minute per square foot of the top layer's surface area. Slow sand filters remove most pathogens but have limited effectiveness at removing organic chemicals and dissolved heavy metals.

    Ultraviolet Light Purification

    • The sun's ultraviolet rays are one of the most natural methods of water purification. Most bacteria and parasites can withstand several days of exposure to intense direct sunlight, so UV filtration systems usually involve artificial UV lamps. The lamp's wavelength should be roughly 254 nm, and filtered water should receive UV exposure of 40,000 µW/cm2, according to EPA guidelines. For individuals unsure of how to measure UV exposure, commercial lamps exist with clearly published UV exposure ratings. Most commercial filters purify 1 to 9 gallons of water per minute. UV filters are highly effective against bacteria and other parasites but won't remove inorganic contaminants from water.

    Sedimentation Filters

    • Natural sedimentation filters work best with wells or other large sources of water. These filters function much like sand filters but use additional materials and more than one tank. In such a filter, water passes through an upper tank filled with fine sediment. Heavier contaminants sink to the bottom of the tank while pumps push the water from the first tank's upper layer into a second tank. Water then passes through layers of sand, carbon and gravel to filter additional contaminants. Sedimentation filtration can be highly effective, but its safety and efficiency vary dramatically based on the amount and quality of the filtration material used.

    Emergency Filtering

    • One common method of filtering water in emergency conditions is passing boiling water through a cloth. "The Backpacker's Field Manual" recommends bringing water to a rapid boil for one minute. Boiling water will kill all organic pathogens but is not foolproof. Simmering water should be poured slowly through a clean cloth to remove additional inorganic contaminants. This method will not remove dissolved or microscopic contaminants.

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