Combined use of heat and oxidants for controlling adult zebra mussels

The results of an experimental study are presented that demonstrate the use of chlorine or ozone to control zebra mussels at temperatures from 30 to 36°C. Control studies were conducted with no oxidant present. Three acclimation temperature ranges were tested: 0–5, 10–15, and 20–25°C. Chlorine was tested at 0.1 and 0.5 mg/L; ozone at 0.5 mg/L. Mortality was described by a cumulative normal distribution, from which times to 95% mortality were estimated and used as a dependent variable for hypothesis testing. Study results showed that the addition of chlorine or ozone was more effective than heat alone at test temperatures above 30°C. Compared to heat alone, the combined use of heat and oxidants decreased the time to 95% mortality by more than 95% at 30°C. Above 30°C, the benefits of the combined treatment strategy decreased with increasing test temperature. At 36°C, the benefits of the combined treatment strategy over heat alone were minimal. Acclimation temperature was important only for heat alone and for mussels acclimated at 0–5°C. The addition of chlorine or ozone at elevated temperatures can reduce mortality times by as much as three orders of magnitude compared to oxidant addition at ambient temperatures. The results of the study should be of significance to power plants or industries where excess heat is available to raise water temperatures.