centuries, Europeans have not found a satisfactory control method for zebra
mussels. In the Great Lakes, no technique has been developed that is both
feasible for widespread use and not harmful to other aquatic species. Lake-
or river-wide control of zebra mussels is simply not possible at this time.
|A number of
methods have been tried, however. Proactive treatments include the following:
Corps of Engineers has evaluated a variety of coatings, include some
containing copper or zinc products, which are toxic to zebra mussels;
silicone-based systems that provide a low-tension, nonadherent surface; and
thermal sprayed metallic coatings.
Chemical treatment involves use of oxidizing chemicals, nonoxidizing
chemicals and molluscides. When used, chlorination involves injecting
chlorine through a facility and then dechlorination before the water is
returned to the waterbody. The EPA requires that the discharge be analyzed
and monitored to demonstrate that the system works properly and meets EPA
Temperatures above 95-100°F for several hours are lethal to zebra mussels, so
its possible to prevent zebra mussels from colonizing structures by
injecting steam or hot water and circulating them through a facility
line filters with extremely small mesh sizes can be used to filter the
troublesome veligers, but backwashing can be a problem at high flow rates.
treatments include a few other possibilities:
high-pressure water Mechanical cutting devices and high-pressure water
treatments typically involve manual labor and hand tools. These can be used
to dislodge zebra mussels from large surface areas, such as those found in
blasting Blasting can also be an effective mechanical means of removing
Freezing during the winter or desiccation at high summer temperatures can
be effective in killing a large portion of the zebra mussel population. Where
feasible, the population can be exposed by lowering water levels, since the
mussels are usually restricted to shallow areas above the thermocline.
|Radiation -- UV
light (wavelengths between 40° and 4,000°) is a prospective zebra mussel
control method. Researchers found that not only are zebra mussel veligers
sensitive to UV-B radiation (2800° - 3200°), but also adult zebra mussels
were sensitive, provided that the radiation was applied constantly. Veliger
mortality was 42-percent after 1 hr, 85-percent after 2 hr, and 100-percent
after 4 hr exposure to UV-B radiation.