Effects of intermittently chlorinated cooling tower blowdown on fish and invertebrates

Abstract

Cooling towers at the Applachian Power Company, Carbo, Virginia, were treated for slime control with 0.75 mg/1 of Cl for 30 min 4 times/d. The cooling tower blowdown was discharged into the Clinch River. Caged bluegill sunfish and snails were placed at various distances downstream from the blowdown discharge and observed for 96 hr. Amperometric determinators for free and total Cl were made at 10-min intervals at selected stations throughout the study period. No fish deaths occurred which could be attributed to the blowdown discharges; the blowdown was acutely toxic, however, in 72 hr to 50 percent of the snails exposed to less than 0.04 ppM total residual Cl for less than 2 hr/d and to 80 ..mu..g/1 Cu plus other blowdown constituents. The impact of the cooling tower blowdown on the total ecology of the Clinch River was probably of no importance since the observed mortalities were restricted to an area extended less than or equal to 20 ft from the left bank and 800 ft downstream.