Minor elements in water

A complete characterization of natural waters includes a determination of the concentrations of 30 or more minor elements. Emission spectrochemical methods are uniquely suited to the determination of a comparatively large number of minor elements, mainly those classified as heavy metals. Spectro-chemical data published by Braidech and Emory in 1935 and more recent data by Durfor and Becker, and by Barnett, Skougstad, and Miller, provide some insight into the minor-element character of the raw- and finished-water supplies of most of the major U.S. cities. Such data permit assessment of those supplies that contain either comparatively high or low concentrations of minor elements. The concentrations of many minor elements are unchanged by the municipal treatment-plant operations between the raw- and finished-water supply. On the other hand, part of the copper in a raw-water supply may be removed during treatment, even though the over-all result is a net increase in copper in the finished water. The aluminum concentration of finished water is greater than in the raw-water supply when aluminum sulfate is used as a coagulant aid. Significant amounts of iron may be removed during treatment.