This section was developed using information and original text from the Zebra Mussel (Dreissena polymorpha) Control Handbook for Facility Operators.
Acute upper lethal temperatures are defined as the temperatures at which death occurs when water temperature is raised at a specific rate. Heating of raw water systems to the acute lethal temperature of zebra mussels, followed by rapid return to normal operating temperatures, is a promising thermal mitigation technology for zebra mussel macrofouling (McMahon et al. 1995). Acute upper lethal temperature treatment to mitigate zebra mussel fouling is most applicable in raw water systems where lethal temperatures are difficult or inefficient to maintain for extended periods. In these systems, increasing water temperature to a level that induces an instantaneous 100-percent mussel mortality followed by a return to normal operating temperatures is more practical. Acute thermal treatment does not require precise, long-term regulation of elevated temperatures, and has been proposed for raw water systems where operation above normal water temperatures for prolonged periods reduces efficiency and increases component wear, making chronic thermal treatment of zebra mussels economically infeasible. Acute thermal mitigation may also be particularly applicable for use in off-line components such as intake embayments heated by steam injection or other means.
The acute upper lethal temperature of zebra mussels is affected by both the acclimation or ambient water temperature and the rate at which the temperature rises and induces instantaneous death. The temperature at which instantaneous death ensues increases with increased acclimation temperature and increased heating rate. McMahon et al. (1995) studied the relation of acclimation temperature and rate of temperature increase to zebra mussel mortality.
Acute Thermal Treatment Graph
The time required for 100-percent zebra mussel mortality with respect to acclimation temperature for heating temperatures of 35, 36, and 37 C (adapted from McMahon et al. 1995).
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