Effect of temperature and pH on the toxicity of monochloramine to the Asiatic clam

The Asiatic clam (Corbicula fluminea) has become a pest to many users of freshwater transmission systems. Monochloramine has been suggested as a biocide because it is effective and the formation of trihalomethanes is low. Flow-through aquariums, a laboratory incubator, and a pilot-scale pipeline were used to show that monochloramine concentrations between 1 and 10 mg/L effectively killed juvenile clams over a wide range of water temperatures, with mentality increasing significantly with temperature. The reduction in clam mortality as water temperature decreases can be overcome by corresponding increases in biocide concentration. An equation is provided that predicts the kill that would be achieved at a given biocide residual and water temperature. The pH did not affect the efficacy of the biocide.