Some Aspects of Chemical Treatment at St. Louis Water Works

Abstract

The principal streams contributing to the water supply of the city of St. Louis are the Mississippi, Illinois and Missouri Rivers. The Illinois River enters the Mississippi 33 miles north of the intakes at the Chain of Rocks and in traversing this distance a more or less intimate mixture of the two waters is effected. The Missouri River enters the Mississippi 5£ miles north of the intakes and causes a pressing of the Mississippi River water upon the east bank of the river and in this way, as a rule, very little mixing of the two waters occurs by the time the water reaches the intakes. At times the turbidity of the water on the west side of the river is ten times as great as that of the water on the east side, and at other times the color of the east water is 25 parts per million greater than that of the west water, showing the incompleteness of the mixing of the two waters. With a high stage in either river and a low stage in the other, the mixing of the waters is more complete. The waters in each of these rivers have certain characteristics which become of greater or less interest as the Stages of the rivers vary. The Mississippi River drainage area being covered with swamps, the water in this river becomes highly colored at times of heavy run-off, while the Illinois River, carrying a large amount of sewage, contains colloidal organic matter which seems to act as a protective colloid on the turbidity carried by this rivei. The water in the Missouri River, always turbid, becomes much more so at times of heavy run-off. The dissolved solids in these waters vary considerably but dissolved solids offer no difficulty in the treatment of the water and are therefore of less interest. The river water enters the plant through two intakes, one, the old or west intake, 1500 feet east of the west bank of the river and connected to the wet well by a 7-foot circular, brick-lined tunnel, 2197 feet long. The other, or east intake, is 700 feet east and 200