Zebra mussels, a small freshwater mollusk native to the Caspian and Black Seas, have been causing big problems in North American waters.
In addition to causing water quality issues and disrupting aquatic ecosystems, the prolific shellfish and their cousin, the quagga mussel, accumulate on underwater infrastructure and boats. This accumulation is called biofouling.
The freeloading mollusks cause corrosion via their acidic fecal matter, and the sticky protein threads they use to attach to surfaces have been shown to increase the corrosion rate of steel and iron, according to a 2001 study of shipwrecks in Lake Champlain.
According to a report by the U.S. Department of the Interior, these mussels “grow on a variety of infrastructure systems, including water intake pipes for drinking water, irrigation, and power plants. They also attach to locks, the faces and interiors of dams, and canal systems, greatly impacting operation and maintenance costs. With continual attachment, the mussels can increase corrosion rates of steel and concrete, leaving equipment and infrastructure vulnerable to failure.”
The Emsworth Locks and Dam, located on the Ohio River in Pittsburgh, Pennsylvania, is evidence of this. Operated by the US Army Corps of Engineers (USACE), the Emsworth project is one of six major river facilities on the Ohio River.
The presence of zebra mussels was throwing a wrench in the dam’s gate system, and to add insult to injury, the bulkhead structures were built using two different metals, aluminum and steel — a “perfect storm” scenario for developing corrosion problems.
To restore the bulkheads, USACE called in the experts from Coatings Unlimited, a St. Louis-based industrial coatings company.
“Typically, you don’t coat aluminum because it doesn’t need it, but [USACE] were having problems with zebra mussels attaching themselves to the bulkhead,” said Gene Ebbinghaus, project manager at contractor Coatings Unlimited Inc. “Secretions from the zebra mussels were causing pitting in the aluminum,” he continued. “They were concerned about losing the structural integrity of the bulkheads.”
The crew worked on one bulkhead at a time, starting with installing two types of containment. They used 85 percent containment underneath to avoid re-introducing the mussels and 100 percent (impenetrable) tarps when prepping.
That prep included pressure washing the aluminum with 5,000 psi to eliminate contaminants such as algae. The crew also blasted the surface to achieve a blast profile compliant with SSPC SP 16 Standard (Brush-off Blast Cleaning Non-Ferrous Metals).
To begin the coating process, the crew used a ceramic epoxy-based composite material to patch corrosive pits created by the bulkheads’ dissimilar metals. Then, the crew came back in to work on the three-coat spray-applied system — sanding, tackling defects, and verifying coating thickness measurements at each step. In total, the crew covered 40,000 square feet of aluminum.
While this approach addressed an existing biofouling problem, researchers are working to find new ways to prevent biofouling before it begins. Although many of these solutions address marine biofouling in the shipping industry, they may also have freshwater applications to fight the zebra mussel invasion in North America’s lakes and rivers.
- In 2018, APV Engineered Coatings announced an experimental marine coating that would prevent damage caused by barnacle and zebra mussel fouling while reducing maintenance costs and environmental effects. This new antifouling coating is based on the Marine Organism Sensory Interference (MOSI) concept, which “tricks” juvenile barnacles into creating a type of adhesive that does not allow itself to attach to ship hulls and other marine assets.
- Protective coatings applied to vessels usually contain copper-based biocides, which may harm the environment and become ineffective due to resistance developed by organisms. A German research team simulated a defense mechanism employed by algae, and discovered that cerium dioxide (CeO2) nanoparticles can effectively prevent fouling. This discovery could lead to the production of new protective coatings that are much less environmentally harmful than current antifouling coatings.
- Dutch paint and performance coatings company, AkzoNobel, is working to develop a biocide-free fouling prevention technology using ultraviolet light-emitting diodes (UV-LED) for the hulls of ships and boats.
Sources and Additional Reading
AMPP Interview Series. “AMPP Technical Exchange on Ship Biofouling.” 2021.
Chizik, Stephanie M. "Coatings Crew Mussels Through Corroded Bulkheads." CoatingsPro Magazine, January 2019.
Koch, Sophie. “Invasive Zebra Mussels.” U.S. National Park Service.(2017)
US Army Corps of Engineers. Emsworth Locks & Dams.
US Army Corps of Engineers. Zebra Mussel Resource Document (2013)
US Department of the Interior, Invasive Species Advisory Committee. Invasive Species Impacts on Infrastructure (2016)
Watson, Mary, Arthur B. Cohn, and Bryan P. Emerson. Zebra Mussels, Shipwrecks, and the Environment. (2001)
USACE operations employees scrape zebra mussels off the lock wall. The U.S. Army Corps of Engineers St. Paul District dewatered Lock and Dam 7, located near La Crescent, Minn., to do major renovation and rehabilitation work. (U.S. Army Corps of Engineers photo by Shannon Bauer)