Water that is safe to drink is called potable water, or drinking water, in contrast to safe water, which can be used for bathing or cleaning. In the United States, the Environmental Protection Agency sets maximum levels for the 90 most commonly occurring contaminants. If something happens to your water supply, your supplier has to contact you to let you know what precautions you should take.
Water treatment requires six basic steps.
- In coagulation, coagulants like lime and alum are added to the water, which causes particulates to clump together.
- Next, the water is shaken into larger clumps, called flocs.
- The sedimentation process requires that the water stand for 24 hours, which allows the clumps to settle to the bottom.
- The water is then filtered, disinfected (usually with chlorine) and aerated.
- Aeration helps to remove certain contaminants like radon.
In the next section, we'll take a closer look at exactly how water circulates in animal and plant cells.