Water treatment—or the purification and sanitation of water—varies as to the source and kinds of water. Municipal waters, for example, consist of surface water and ground-water, and their treatment is to be distinguished from that of industrial water supplies.

Municipal water supplies are treated by public or private water utilities to make the water potable (safe to drink) and palatable (aesthetically pleasing) and to insure an adequate supply of water to meet the needs of the community at a reasonable cost. Except in exceedingly rare instances, the entire supply is treated to drinking water quality for three reasons: it is generally not feasible to supply water of more than one quality; it is difficult to control public access to water not treated to drinking water quality; and a substantial amount of treatment may be required even if the water is not intended for human...