Chlorine demand and trihalomethane formation by tubercles from cast iron water mains

Chlorine demand was monitored using tubercular corrosion deposits collected from the Columbus water distribution system. The initial rates of chlorine demand were inversely pH‐dependent. The time courses of chlorine demand were found to have two phases; the first was rapid and large and the second was slow and small. In parallel experiments the formation of trihalomethanes was monitored. Chloroform was the only trihalomethane compound identified in the chromatogram. The formation of chloroform‐correlated directly with the pH and inversely with the chlorine demand.