H2O. Two hydrogen atoms and one oxygen atom, is all that make up the most important substance to all living beings on earth. Water, as the best known, has a touch of blue in their purest form and is known as the most universal solvent. In all three countries, the water takes many forms: water vapor and clouds in the sky, waves and icebergs in the sea, glaciers and aquifers in the country for a few. Of water on Earth is 97% salt water and undrinkable by humans. The remaining 3% is fresh water or drinking, but that 2% is frozen in glaciers and ice caps. Our bodies are approximately 65% water so it is vital to our health. For proper functioning of the body requires between one and seven liters of water a day to prevent dehydration. Through evaporation, precipitation and runoff, water is constantly changing from one state to another in what is known as the hydrologic cycle. Run-water flow after rainfall or recharge groundwater aquifers. In many countries water is becoming increasingly scarce as the human population in these places, and availability is a major social and economic concerns. Major pollutants in water are also a major source of concern as contaminants such as fertilizers and chemical waste, can be found in our water supplies. Gone are the days, in many developed countries, where municipal tap water is considered safe to drink. Here are some common undesirable contaminants: Chemical Lead – found in water with lead solder or pipes, especially if the water is soft or corrosive. While lead is never desirable, concentrations above 15 micrograms per liter (15 ug / L also known as parts per billion or ppb) can cause brain, nerve and kidney damage, especially in young children. Nitrate Nitrogen – nitrate nitrogen is commonly used lawn and agricultural fertilizers.It is a chemical formed when the decomposition of waste as fertilizer or sewage.Fluoride – add water to reduce tooth decay, but there is controversy about the benefits and risks. Small amounts of fluoride is often used in health applications, but the levels found in water should be monitored and published. Bacterial and parasiteCryptosporidium – is a common parasite found in lakes and rivers, especially when the water is polluted with sewage and animal waste. Escherichia coli – (usually abbreviated to E. coli) is one of the main types of bacteria that live in the intestines of warm-blooded animals and are necessary for proper digestion of food. Its presence in groundwater is a common indicator of sewage contamination.Bottled today because of a much greater awareness of water contaminants, more people drink bottled or filtered water for consumption. Bottled water can be divided into three sources: the spring water – Derived from an underground aquifer from which water flows naturally to the surface of the earth. Spring water must be collected only at source or through a hole tapping the underground formation feeding the source. If some external force is used to draw water from a well, water should have the same composition and quality as the water flows naturally to the surface. Mineral water – water from an underground source that at least 250 parts per million total dissolved solid. Minerals and trace elements must come from the groundwater source. You can add later. Purified water – usually comes from municipal sources – in other words – the key. Drinking water is usually treated before being bottled. As shown, there are plenty of questions to the authenticity label bottled water advertising. If you drink bottled water, always read the fine print to see where it comes from or what "claims" to be. Another way to remove unwanted contaminants in water by filtration. The filtration and purification filtration and purification, it takes a lot to explain what they do, but what it should be noted, is the large number of types and their effectiveness against various contaminants. Boiling – The water is heated to boiling for one minute kills the microorganisms that normally live in water at room temperature. Carbon Filter: coal, with a large area, due to the method of preparation absorbs many compounds including some toxic compounds. The water passes through activated carbon to remove impurities. Distillation: – involves the boiling of water to produce steam, leaving contaminants. The water then rises to a cold surface, it condenses