Volunteer Monitoring for Zebra Mussels
Economic Impacts
•
•Control
•Preventative
–coatings
–chemicals
–thermal treatment
–filtration
•
•Reactive
–mechanical
–high pressure water
–carbon dioxide pellet blasting
–freezing/dessication
•
After two 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:
Coatings – The 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.
Chemicals – 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 limits.
Thermal – Temperatures above 95-100°F for several hours are lethal to zebra mussels, so it’s possible to prevent zebra mussels from colonizing structures by injecting steam or hot water and circulating them through a facility periodically.
Filtration – In 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.
Reactive treatments include a few other possibilities:
Mechanical and 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 power plants.
CO2 pellet blasting – Blasting can also be an effective mechanical means of removing zebra mussels.
Freezing/dessication – 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.