It's an interesting question. How does the earth purify water? Seeing as though natural spring water originating hundreds, sometimes thousands of feet below the earth's surface is the cleanest, healthiest and most delicious H20 ever to be tasted, it might be a good idea to understand just how that happens. How can water that comes from the dirty ground be purer and safer than what comes from my kitchen faucet? Perhaps the notion appears counter intuitive. But it is true. The water that has filtered through many layers of sediment and gravel is purer than even some filtered, bottled H20.
When investigating the answer to the question “How does the earth purify the water?”, I like to imagine that the layers of the earth are really just giant filters that help to eliminate contaminants in water as it makes its way down through the rocks, sand and gravel. This is not a quick process. In fact, you might go crazy sitting there waiting for it to turn into pure, underground spring water. In a given one square foot area, H20 passes through layers of dirt, sand and gravel at a rate of 0.1 gallon a minute. That's 0.4 liters a minute. By the time you had enough water to quench your thirst, you might be old and gray.
Natural springs found deep below the surface of the earth has naturally filtered out 99.9 percent of contaminants that could harm a person's health if ingested. As the water moves through the various porous layers of the earth, foreign particles are trapped in the sediment while it passes freely, but slowly, down to deeper layers. Even microorganisms that can cause disease and death in ingested by humans or animals are filtered out of the water through this natural process.
How does the earth purify water in other ways?
Another way in which the earth naturally purifies is through the water cycle. You probably learned about this in elementary school. The cycle starts with the large bodies of waters such as oceans and seas. Great volumes evaporate off the surface of these bodies of water and become gas and drift up into the earth's atmosphere. Most particles are not able to evaporate and stay behind. The water then reconstitutes as a liquid and falls to the earth as rain or snow. Of course pollution in the air and water has devastated this process.