Studies of Radioactivity in the Chicago Water Supply

Abstract

supplies, water producers feel the need of a radioactivity monitoring program for these supplies at the state or municipal level. It is apparent that prevention or control of discharge of radioactive wastes into water supplies is of primary importance. This is especially true considering that there is no method now applicable on a plant scale which assures complete removal of radioactivity, or even removal to below acceptable levels, should the raw water levels exceed the permissible concentration. Were such a method available, many problems would be presented in treating over 450 mgd of water, an amount frequently pumped through the South District Filtration Plant in Chicago. As long ago as 1950, officials of the Chicago Bureau of Water realized the hazard of potential radioactive pollution of Lake Michigan waters. At that time, a limited monitoring program was started with the aim of obtaining some background data concerning radioactivity levels in the lake. This program has continued to the present time, with some modification and expansion. Before discussing the monitoring program it might be well to review some data on permissible concentrations of radioisotopes in drinking water. The maximum allowable conc ntration for mixed fission products for lifetime consumption, is 1 X 107 /xc/ml. The 10-day emergency acceptable tolerance, again for mixed fission products, is 9 X 10~2 /*c/ml. Table 1 shows the maximum permissible average c ncentration of some common radioisotopes in water for nonoccupational exposure (1). Attention is called to the extremely small amounts of these elements considered permissible in waters for domestic use.