The report gives results of a study of methods used to reduce free-chlorine residuals in power plant effluents. Most U.S. power plants use chlorine (28,600 tons in 1972) to control biological fouling in their cooling systems, particularly in their condenser tubes. Using chlorine raises many questions regarding the toxicity of chlorinated compounds which may enter public drinking-water systems or harm aquatic organisms in the receiving water. The report considers viable alternatives to current chlorination practices used to decrease passage of ecologically harmful effluents to receiving waters. Alternative methods include: use of other chemicals (BrCl, ClO2, O3, controlled-release pesticides); more efficient methods of chemical application (serial dosing near the condenser inlet, adding dechlorination chemicals, blowdown timing control, chlorination by residuals feedback control); on-line mechanical cleaning (sponge ball system, brush system, hot water backflush system); and physical/chemical treatment. Information on advantages, disadvantages, costs, and applicability for retrofit or new installations of these methods is presented. Promising approaches to reducing free-chlorine residuals in power plant effluents are available.

Prepared under contract 68-02-1320, program element no. EHE624. Issued Mar. 1977. Includes bibliographical references (p. 68-74).