Mechanical removal of zebra mussels using wire brushes, scrapers, or other physical means is effective. However, manual means are generally less cost effective than the preventive type of control methodology because they must be repeated at regular intervals, and removal and disposal of zebra mussel shells need to be considered (Figure 5).
Pigging systems involve forcing plugs (pigs) through mussel-infested lines to scrape mussels from pipe walls, forcing them out in front of the advancing pig. Pigs can be forced through lines by gas or fluid pressures or by hauling on cable systems. For smaller intakes (< 60 cm) mechanical pigging operations may be the method of choice. Pigs are available in a wide variety of designs and are manufactured to clean pipes up to 180 cm in diameter. Generally, the piping will need some modifications to provide entrance and exit capabilities (Claudi and Mackie 1994).