An adequate supply of clean water is essential to our health and well-being. We can live without food for many days, but life would end in only a few days without water. Our circulatory system is an aqueous stream 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-fourths of Earth’s surface is covered with water, which gives the planet a blue color when it is viewed from space. The oceans represent the world’s largest liquid solution. Water participates in most of the chemical reactions that occur in nature. Most 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 downstream. Such reused water may become seriously polluted 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 settling, whereby specific materials are added to bring down suspended
solids. This is followed by filtration through sand and gravel to remove still
more suspended matter. The filtered water may 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, chlorine or another disinfectant is added to kill any remaining bacteria.
The treatment of water before use is an important safety precaution.
