Kreis et al.(1994) indicate that contaminants are primarily associated with zebra mussel tissues rather than with shells (Table 5). This has also been observed by Secor et al.(1993) and van der Velde et al.(1992). Disposal of zebra mussel waste involves whole mussels and includes both tissues and shells. The shells effectively dilute contaminant concentrations in relation to the disposal of zebra mussel waste. Kreis et al. (1994) also discuss some of the problems associated with the use of zebra mussels for contaminant biomonitoring and state that their data strongly support the conclusion that whole zebra mussel contaminant concentrations are relatively low and that the zebra mussel contaminant concentrations would be considered nonpolluted if compared to USEPA sediment guidelines. These data do not indicate that normal zebra mussel populations require any special disposal practices.
Table 5, a summary of organic and metal contaminant concentrations and percent lipids for shell, tissue, and whole zebra mussel, size class 16-19 mm, from western Lake Erie, is from Kreis et al. (1994). The data summarized in Table 5 indicate that zebra mussels are well-suited to accumulate contaminants such as metals, PCBs, and petroleum hydrocarbons from water and suspended sediments, but tissue concentrations of whole mussels are generally low. Contaminant bioaccumulation by zebra mussels has been demonstrated in the laboratory and in field populations. Periodic removal of zebra mussel populations from facilities should aid in preventing tissue concentrations from becoming excessive. The data in Table 5 indicate that contaminant concentrations do not exceed criteria in leachate tests with field populations of zebra mussels.
There is no reason, therefore, to consider whole zebra mussel waste as hazardous, and in the absence of additional data, no special precautions are necessary for the disposal of the zebra mussel. Periodic chemical analyses and/or leachate tests of zebra mussels removed from facilities are recommended, especially at locations having any history of contamination. Large volumes of zebra mussels generally should not be disposed of at aquatic sites or used as animal feed. Secor et al. (1993) report chemical analyses of zebra mussels from known contaminated areas in New York. The zebra mussels were found to contain generally high levels of Cd, Se, and PCBs. This kind of information should be carefully considered prior to decisions about disposal of dead zebra mussels or the use of the zebra mussel as food for farm animals or as a fertilizer. Zebra mussels can be disposed of at approved landfills, but may also be composted to increase disposal options.
Currently zebra mussel remains may be disposed of at municipal landfills that will accept them. The most obvious problem associated with zebra mussel disposal is the characteristic odor that results from their rapid decomposition. It is possible that in some cases whole zebra mussels or zebra mussel liquids, resulting from decomposition, could be considered a contaminant source and may make disposal difficult without chemical analyses and/or state permits. There is also general agreement that zebra mussels taken from a waterway or hydropower facility should not be disposed of in any aquatic habitat.