An adequate supply of clean water is essential to our health and well-being. We can live many days without food, but life would end in a few days without water. Our circulatory system is a watery current that distributes an amazing variety of substances throughout the body. Our cells are filled with water solutions in which the chemical reactions of life take place. Without water and its unique properties, life would not be possible on Earth.
Three-quarters of Earth’s surface is covered in water, giving the planet a blue color when viewed from space. The oceans represent the largest liquid solution in the world. Water participates in most chemical reactions that occur in nature. Most of the water used for human consumption comes from reservoirs, lakes, rivers and wells. Much of this water is used and reused by numerous cities as it travels down the river. Such reused water can be severely contaminated with waste from previous users and with pathogenic microorganisms.
As a safety precaution, most of the water we use undergoes chemical and physical treatment to purify it. This treatment process includes sedimentation, whereby specific materials are added to reduce suspended solids. This is followed by filtration through sand and gravel to remove even more suspended matter. The filtered water can then be aerated by spraying it into the air. This part of the treatment process removes some odors and improves the taste of the water. Charcoal filtration, a treatment process that is gaining in use, also removes odors along with colored materials. In a final step, bleach or another disinfectant is added to kill any remaining bacteria.
Treating the water before use is an important safety precaution.