Much of what has been said about the need for high quality water supplies as a basis for preparation of potable water is more the product of emotion than of logic. The water of the much discussed Hudson River, which allegedly should not be used for municipal supply because of its poor quality, is actually of comparable quality to that at the Torresdale intake of the City of Philadelphia and better than the quality at the intakes of the City of St. Louis.
For many years acceptable drinking water has been produced from water of such quality—albeit at the expense of some extra chemical and physical treatment. Moreover, a plant at Dusseldorf, Germany, with draws water from the Rhine River, which is of far lower quality thall the Delaware, the Hudson, or the Missouri, treats it with activated carbon and ozone, and produces quite suitable drinking water.
Poor quality water does impose extra costs on municipal water systems but—except in cases of toxic or evil-tasting substances—use by municipalities ordinarily cannot justify very high levels of waste effluent control. Usually the toxic elements comprise very small and separable portions of waste effluents.
This general point is brought brought out a recent study of a stream system along whose shores are municipal waste dischargers and municipal water users. It involved a very careful gathering of cost data and the generation of new cost information. The study also developed a sophisticated technique for estimating by means of computer simulation the interrelationship between water quality at waste outfalls and at water intakes. It was found that vast amounts of reuse are required to justify the additional costs of advanced treatment for municipal waste disposal.
For example, it turned out downstream water withdrawals to be treated for municipal water supply had to be anywhere from 10 to 250 times as large as the waste discharge (after treatment) upstream before additional waste treatment costs upstream could be justified. Again it appears that the need to prepare potable water cannot justify particularly high standards of quality in watercourses.
This leads to the conclusion that higher water quality must be justified primarily on aesthetic and recreational grounds.
Adapted from Managing Water Quality: Economics, Technology, Institutions, by Allen V. Kneese and Blair T. Bower (published for RFF by Johns Hopkins Press, 1968).
A version of this article appeared in print in the September 1968 issue of Resources magazine.
