Using Zebra Mussels to Filter Milwaukee's Water
When politics meets science, strange things can happen.
Jerry Kaster found out just how strange when his idea for using zebra mussels as a low-tech water treatment filter recently sparked a heated debate at Milwaukee's City Hall.
Kaster, an associate professor of biological sciences at UW-Milwaukee's Center for Great Lakes Studies, never had any plans to enter the political fray when he proposed using zebra mussels as a first step in Milwaukee's potable water purification system. Initial labwork had shown the idea to be feasible, at least on a small scale.
But Milwaukee alderman Michael J. Murphy seized on Kaster's idea and proposed funding a study using mussels as an alternative to ozone disinfection. Murphy opposed spending $51 million to install ozone disinfection systems in Milwaukee's two water treatment plants. Ozone disinfection, an expensive but effective means of water purification, was part of an $89 million water treatment package the city was considering in an effort to prevent incidents like the 1993 cryptosporidium outbreak, which made more than 400,000 Milwaukeeans sick.
The debate snowballed when Milwaukee Water Works Assistant Superintendent Dale Mejaki said that using a zebra mussel biofilter was infeasible and had already been reviewed and rejected by his office.
Ironically, the political hubbub obscured the potential benefits of the biofilter, which still holds tremendous potential for a variety of water treatment applications, Kaster said.
"People had the wrong impression that the [zebra mussel] biofilter was intended to replace ozone treatment," Kaster said. "That was never the case. The zebra mussel treatment was always intended as a pretreatment."
The biggest benefit, Kaster said, is that zebra-mussel prefiltering would allow water to pass through subsequent filters much faster, saving energy and improving efficiency.
"We ran brown water through the (zebra mussel) biofilter and it came out clear," he said. "That prefiltered water then passed through traditional filters 70 times faster than 'control' water that had not been through the biofilter."
Kaster also found that zebra mussels don't ingest most particles in the water, but instead cover the particles with mucus and clump them together, then discharge them back to the water. The larger clumps are much easier to filter.
Kaster admitted that some of his ideas might meet resistance because they're so different from traditional water-treatment practices.
"Potable water facilities personnel are trained to use chemicals to treat water," Kaster explained. "Though sewage treatment facilities have used biofilters for a long time - snails and worms and bacteria, for instance. Which brings up another possibility - using them to help clean up sewage effluent. We know they can survive in some pretty foul environments."
Despite his scientific enthusiasm, Kaster is practical. He's continuing his research while waiting to hear if the city of Milwaukee will provide him with any funding. If not, he plans to seek funding elsewhere.
"The bottom line is that this idea has to be demonstrated to work on site," he said. "But assuming it does, communities with zebra mussel problems might tie into the idea of using zebra mussels to help filter their water. It would be a great low-tech application."
- Laurence Wiland
Aquatic Sciences Seminars Continue
The Recent Advances in Limnology and Oceanography seminar series continues through the spring semester at the Center for Great Lakes Studies at the University of Wisconsin-Milwaukee.
The remaining calendar of 1995 sessions includes:
February 23: Peter Sousounic, University of Michigan, Atmospheric, Oceanic and Space Sciences, "Multi-Scale Impacts of the Great Lakes in Winter: How Atmospheric Circulation 'TouchesŐ the Lakes"
March 2: Kenneth H. Nealson, University of Wisconsin-Milwaukee, "Biological Sciences and Center for Great Lakes Studies Bacterial Metal Reduction at Interfaces: Who Does It, How and Where Do They Do It, and Why Does It Matter?"
March 23: Thomas Osborn, The Johns Hopkins University, "Copepod Behavior and Turbulence: A New View of the Physics of Feeding"
March 30: James Maki, Marquette University, Department of Biology, "Microbial Process in the Surface Microlayer"
April 6: Bjorn Sundby, Universite du Quebec, INRS-Oceanologie, "Solute Transport and Reactions Near the Sediment-Water Interface: Models and Microelectrodes"
April 13: Max L. Bothwell, National Water Research Institute, Saskatoon, SK Canada, "Ecosystem Responses to Solar UV-B Radiation: Influence of Trophic Level Interactions"
April 27: Frederick J. Grassle, Rutgers University, Institute of Marine and Coastal Sciences, "Deep Sea Biodiversity" Sessions are held at 7:30 p.m. Thursdays at the Center for Great Lakes Studies. The program is supported by the University of Wisconsin Sea Grant Institute and the Cooperative Institute for Limnology and Ecosystem Research. For further information, contact Arthur S. Brooks at (414) 382-1700.