This section was developed using information and original text from the Zebra Mussel (Dreissena polymorpha) Control Handbook for Facility Operators.
Zebra mussel thermal mitigation strategies, based on the chronic upper thermal limits of the mussel, involve continuous exposure to constant lethal temperatures for durations sufficient to achieve significant mortality. Chronic thermal treatment for mitigation of zebra mussel infestations is most applicable to industrial and steam-electric power station raw water systems. These facilities generate heated discharge water and can recirculate or backwash heated effluent into their intakes to maintain operating temperatures at relatively constant, elevated, lethal levels for prolonged periods.
The exposure time of chronic thermal treatments is affected by both the acclimation and treatment water temperatures. The required exposure time increases as the acclimation temperature increases and the treatment temperature decreases (McMahon and Ussery 1995). Mitigation treatment with temperatures greater than or equal to 34°C could induce near 100-percent kill of zebra mussel infestations within 6 to 26 hr depending on the prior acclimation/operating temperature (McMahon and Ussery 1995). At treatment temperatures ranging from 34 to 37°C, exposure times required for 100-percent kill of the zebra mussel are short enough to be cost-effective, application temperatures are low enough to prevent major loss of production or excessive equipment wear and/or malfunction, and discharge temperatures are likely to be low enough to meet the discharge temperature restrictions of state and/or federal regulatory agencies (EPRI 1992, Claudi and Mackie 1994).
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