Trihalomethanes in the Cooling Discharge of a Power Plant on Chlorination of Intake Seawater

Trihalomethanes (THMs) formation and species distribution in the discharged chlorinated cooling seawater of a nuclear power plant was assessed during Aug 2010 to July 2011. The monthly variation of chlorine demand of the source seawater under laboratory chlorination conditions was studied for the same period. The entire period can be divided into two separate zones; viz. Feb, Mar, Apr, Sep, Oct (low chlorine demand), and May, Jun, Jul, Aug, Nov, Dec, Jan (high chlorine demand) months. Bromoform was found to be the single dominant THMs species in the chlorinated cooling seawater discharge. The THMs concentration was observed to be highest for the month of Nov 2010 (41 μg/L), and lowest for Feb 2011(12 μg/L). Under laboratory chlorination of intake seawater with 1 ppm Cl₂, the concentration of THMs that was formed within 5–15 min is in agreement with the actual concentration in the discharge water. A simplified predictive approach is proposed for the total THMs concentration at the cooling discharge outlet of a power plant, based on the actual chlorine demand of source water.