Potentiation of the virucidal effectiveness of free chlorine by substances in drinking water.

At 5 degrees C, poliovirus 1 was inactivated by free chlorine (FC) at pH 9.0 more than 10 times as rapidly in drinking water as in purified water. Because ions that comprise many salts potentiate the virucidal effectiveness of FC, we believe that ions and possible other substances in the drinking water potentiated the virucidal effectiveness of FC. Since viruses may be much more sensitive to chlorination in drinking waters than laboratory tests in purified waters have heretofore led us to believe, it may be possible to reduce the amounts of FC applied to many water supplies for disinfection and thereby perhaps reduce the quantities of halomethanes and other toxic compounds produced in these supplies by the chlorination process.