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Smythe, G., C.L. Lange, and G.H. Keipper, 1997. In-Field Evaluation of a Fine Mesh Filter System Using Microbeads and Zebra Mussel Eggs and Embryos to Determine Efficacy in Excluding All Viable Zebra Mussel Life Stages From Irrigation Water, Acres International Corporation Abstract from The Seventh International Zebra Mussel and Other Aquatic Nuisance Species Conference, New Orleans, Louisiana, January 1997 In-Field Evaluation of a Fine Mesh Filter System Using Microbeads and Zebra Mussel Eggs and Embryos to Determine Efficacy in Excluding All Viable Zebra Mussel Life Stages From Irrigation WaterIndustries and municipalities have used various filtration methods to control zebra mussels. Recently, in-line automatic/continuous backwash, fine-mesh filters have been employed to remove early life stages of mussels and clams. The size of the mesh required to preclude mussels from a system can have a major impact on facility and filter operation, as well as system cost. Several mesh sizes have been tested by the authors in Mississippi and New York, by Ontario Hydro in Ontario, and by the New York Power Authority to determine filter efficacy in removal of zebra mussels and operational impacts. These studies demonstrated that settlement-stage mussels could be controlled using filtration. Other studies of in-line filter efficacy have been completed, but the data remains unpublished. Data from one study conducted by the authors, which specifically examined egg passage, suggested that a 40-micron absolute mesh effectively filtered all viable life stages. The earliest mussel life stages (i.e., egg, embryo, and trocophore) are considered by most researchers to be pliable, but very fragile. These stages are easily damaged and probably killed if they suffer any abrasions caused by pressure forcing them through filter meshes. Some resource agency personnel conservatively estimate that the smallest viable eggs (reported to be 40 microns) could be forced through a 40-micron absolute mesh and survive. The Michigan Department of Environmental Quality, therefore, required the Mud Creek Irrigation District (MCID) to install 25-micron absolute mesh in their nominal 2,500 gpm automatic backwash filter system and conduct in-field tests to demonstrate filter mesh integrity and efficacy in excluding viable eggs. The filter system was designed to draw water from mussel-infested Saginaw Bay on Lake Huron, however, the State would not allow the MCID to pump bay water until conclusive tests had been completed. The MCID, therefore, conducted tests in closed-loop mode. In the closed-loop mode, zebra mussel eggs and embryos were not available in the raw water, so innovative techniques were developed to determine mesh efficacy in removal of eggs and mesh integrity. Millions of precision glass microbeads (~18 to 45 microns) were used as surrogate mussels for some tests, while mussel eggs/embryos (collected after inducing adults using serotonin) were used in others. Beads and eggs were injected into the system operating under normal flows and pressure differentials in the closed-loop mode, and backwash and filtered samples were collected and analyzed. Contact: G. Smythe, Acres International Corporation, 140 John James Audubon
Parkway, Amherst, NY 14228-1180 or asmythe@amherst.acres.com
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