St. Louis Dry Line Chlorinating System

1940 the St. Louis Water Dept. was confronted with the problem of adding chlorine, in the Howard Bend secondary coagulation basins, at a point 2,200 ft. from the chlorine control room. Until that time pipelines had been used to transport chlorine solution from the control room to the point of application, less than 500 ft. away, and even with this short line considerable difficulty was experienced with line breaks and other mishaps. Because chlorine solution lines are relatively expensive, it was decided to substitute a less expensive means of application. The dry line chlorinating system now in use at the two St. Louis water purification plants was therefore designed and built. This dry line system consists essentially of a pressure regulator for the chlorine gas, a rotameter and a control valve in the control room ; a steel pipe to carry the dry gas to the point of application, which may be any distance from the control room; and an eductor at the point of application to pull the chlorine gas from the dry line and force it into the water through a short section of chlorine solution hose.