Silicone foul-release coatings that have long protected ship hulls are now showing major promise against invasive mussels that plague much of the nation’s water and hydropower infrastructure, federal researchers have found.
The findings cap a three-year research effort by the U.S. Bureau of Reclamation, whose scientists tested more than 50 antifouling and foul-release coatings on still and flowing waters at Parker Dam on the Colorado River.
Bureau of Reclamation
|The Bureau of Reclamation’s Technical Service Center tested more than 50 coatings and metal alloys over three years at Parker Dam on the Colorado River.|
The research could hold tremendous potential for reducing maintenance and improving performance at the nation’s dams and similar structures.
“The silica foul-release coatings are performing very well,” Allen D. Skaja, Ph.D., PCS, of the Bureau of Reclamation’s Technical Service Center, concludes in a video report on the project.
Some of the foul-release coatings worked so well that the flowing water dislodged the pesky invaders without any additional intervention, Skaja said in a statement.
“The silicone foul-release coatings were found to reduce the rate of mussel settlement, and any attached mussels were easy to remove,” he said. “In many cases, it was found water flowing at 0.1 feet per second provided sufficient force to remove mussel colonies.”
Reclamation scientists were looking for a new tool to combat infestations of quagga and zebra mussels, which can disrupt water delivery and hydropower generation functions.
The pests were introduced into the Great Lakes in the mid- to late-1980s from freshwater ballast discharged from freighters originating in the Black and Caspian Sea region of Eastern Europe and western Asia, according to the National Oceanic and Atmospheric Administration’s (NOAA) National Sea Grant College Program. Since then, the mussels have spread into 22 states and two Canadian provinces.
NOAA New York Sea Grant
|Fouling of underwater substrates by invasive quagga and zebra mussels has cost hundreds of millions of dollars in maintenance and repair.|
Scientists say the mussels wreak havoc in several ways, including clogging underwater hulls, piers, pipes and other substrates by attaching with using tough elastic strands called byssal threads. Hundreds of millions of dollars have been spent to clean up fouled pipes and keep the mussels from fouling drinking water treatment, industrial and power plant intakes, the program reports.
The Bureau of Reclamation, established in 1902, is part of the Interior Department. Best known for the 600-plus dams, power plants and canals it has built in 17 western states, Reclamation is now the nation’s largest wholesaler of water and the second-largest producer of hydroelectric power in the western U.S.
“Parker Dam provided an excellent field test site to evaluate coatings in still and flowing water, because the quagga and zebra mussels infesting this location reproduce throughout the year and have a high growth rate,” the Bureau reported.
The team tested coatings and metal alloys in six categories: conventional epoxies (no fouling control), antifouling coatings (designed to prevent mussel attachment), foul-release coatings (designed to ease removal of mussels that have attached), fluorinated powdered coatings, metallic coatings and metal alloys.
The coatings were tested in still and flowing waters. For still water, three one-foot-square steel plates were tied on a nylon rope and lowered into water about 50 feet deep near the face of the dam. For the flowing conditions, one 18-by-24-inch coated floor grate with one-inch spacing was suspended 40 feet below the water surface downstream from the forebay trash rack structure.
Although the foul-release coatings performed the best against the mussels, the coatings did not hold up well, the Bureau said.
“One problem with silicone foul-release coatings is they are not that durable,” the agency reported.
“Initial research found the silicone foul-release coatings were soft and were easily damaged by floating debris or mechanical abrasion, such as a trash rack being cleaned."
The agency's next step, already underway, is additional research "to find a silicone foul-release technology that will meet the abuse coatings on facilities must take.”