Humans may live for a month or more without food, but only a
few days without water; only oxygen is more important. Each day,
the body loses up to three quarts of water. A loss of only 10-20%
of the body's water content could be fatal.
When we take untreated water
from a river or reservoir, the water often contains natural wastes
and pollutants, such as bacteria, solids (like mud, sand, and
debris), inorganic minerals, and decayed organic compounds, as
well as trace amounts of certain other contaminants. Such water
is not good for human consumption.
Water suppliers transfer this
water to a treatment plant where water will be filtered and chemically
treated to be ready for human use.