Considerable publicity has been generated concerning the use, and harm therefrom, of chlorine in drinking water plants resulting in the formation of the chlorinated hydrocarbons known as total trihalomethane. These are now labeled as carcinogenic by the EPA, which is expected to issue regulations which limit the TTHM at 100 ppb. Among the carcinogens formed are chloroform, carbon tetrachloride and trihalomethanes.
Many municipal drinking water plants are, or have been, involved in extensive bench tests and plant trials for methods to reduce the TTHM in their plant water. The EPA and the American Water Works Association (AWWA) have expended considerable resources on consulting fees and funding projects to this end. The alternative methods have been poor at best, and purport to introduce very costly chemicals, or equipment for THM reduction.
Some prior efforts to reduce total trihalomethane as summarized as follows:
______________________________________ Means Attempted Remarks ______________________________________ 1. Substituting chlorine with (a) Very expensive equip- chlorine dioxide ment; over $1.0MM Tests have shown that in for a medium size some waters ClO.sub.2 is not plant always effective. It has (b) Chlorine & sodium demonstrated an ability chlorite are expen- to reduce the halogens, but sive chemicals. at times, has no effect on (c) ClO.sub.2 is 15 to 20 .times. the THM. cost of Cl.sub.2. (d) Forms a toxic products of chlorite & chlor- ate in H.sub.2 O. (e) ClO.sub.2 is a very un- stable explosive gas for a water treatment plant to store and handle. High energy (electrical) costs to operate in ore site chlorine dio- xide generator. 2. Use of Powdered Activitated (a) Very expensive Carbon (PAC) equipment; over