COMBINED USE OF HEAT AND OXIDANTS FOR CONTROLLING ADULT ZEBRA MUSSELS

The results of an experimental study are presented that demonstrate th e use of chlorine or ozone to control zebra mussels at temperatures fr om 30 to 36 degrees C. Control studies were conducted with no oxidant present. Three acclimation temperature ranges were tested: 0-5, 10-15, and 20-25 degrees C. Chlorine was tested at 0.1 and 0.5 mg/L; ozone a t 0.5 mg/L. Mortality was described by a cumulative normal distributio n, from which times to 95% mortality were estimated and used as a depe ndent variable for hypothesis testing. Study results showed that the a ddition of chlorine or ozone was more effective than heat alone at tes t temperatures above 30 degrees C. Compared to heat alone, the combine d use of heat and oxidants decreased the time to 95% mortality by more than 95% at 30 degrees C. Above 30 degrees C, the benefits of the com bined treatment strategy decreased with increasing test temperature. A t 36 degrees C, the benefits of the combined treatment strategy over h eat alone were minimal. Acclimation temperature was important only for heat alone and for mussels acclimated at 0-5 degrees C. The addition of chlorine or ozone at elevated temperatures can reduce mortality tim es by as much as three orders of magnitude compared to oxidant additio n at ambient temperatures. The results of the study should be of signi ficance to powerplants or industries where excess heat is available to raise water temperatures. (C) 1997 Elsevier Science Ltd.