Mussels as Biological Filters

From January, 1995 (update #23)

MILWAUKEE, Wis. - UW-Milwaukee biologist Jerry Kaster attracted a lot of media attention in late November after a Milwaukee Journal article reported the results of experiments Kaster and co-workers conducted using zebra mussels to filter the city's harbor water. Kaster's experiments involved the construction of a zebra mussel "biofilter" - a filter that uses zebra mussels to remove particles and bacteria from incoming water. The Chicago Tribune then ran an extensive follow-up, suggesting science had come up with a "task for pesky zebra mussels." The Trib story was picked up by national wire-services and prompted a cascade of dueling headlines like "Alderman Will Support Study Of Using Mussels To Filter Water," and "Zebra Mussels Won't Work As Crypto Filter, Official Says." Kaster said that the study investigated the potential of using a series of three one-liter zebra mussel biofilters to filter Milwaukee harbor water. "The incoming water was 'spiked' with Cryptosporidium," he explained, "in order to determine the effectiveness of the filters in removing these protozoans. It turned out that 95 percent of the protozoans and 70 percent of the total coliform bacteria was removed by the biofilters. We repeated this study over and over in a double-blind test - the technicians examining water samples were unaware whether they were examining filtered or unfiltered water - and kept seeing the same results." Kaster pointed out that "the study needs to be repeated on a larger scale to determine its value in a water treatment operation," but deemed the results "promising." He is currently exploring options to construct a larger biofilter and evaluate its effectiveness in a municipal water treatment plant. Milwaukee's keen interest in purifying its water is understandable, given the 1993 outbreak of Cryptosporidium, a parasitic protozoan that tainted the city's drinking water and made 400,000 Milwaukeeans sick. This November, the Milwaukee Common Council approved a proposal to spend $89 million to install ozone disinfection systems at the two municipal water treatment plants to prevent future outbreaks.

ID: 199501-8.

The Zebra Mussel Update was a 4- to 8-page quarterly national newsletter published by the University of Wisconsin Sea Grant Institute from May 1990 through May 1997. The ZMU documented the spread of the zebra mussel -- an exotic nuisance mussel -- through North America's freshwater environments, especially the Great Lakes, and on efforts to control it.