Ship hitchhikers may be in for a shock
By Susanne Rust
Milwaukee Journal Sentinel
Posted on thestate.com on January 12, 2007
MILWAUKEE - Researchers at the University of Wisconsin-Madison and Pennsylvania State University have come up with a clever way of potentially decreasing the contamination of invasive species and other aquatic critters that latch onto boats in the Great Lakes and beyond.
It just requires a few little shocks.
The work, which the researchers say is just a first step, could mean fewer hitchhiking zebra mussels on boat hulls, or mollusks that slow down the U.S. Navy's ships. It could save the Navy millions of dollars each year and reduce a headache that has plagued the shipping industry for hundreds of years. It also could help to clean up water treatment and industrial intake pipes across the Great Lakes.
It's a field of research known as "biofouling," and it's such a hot subject in the world of chemical engineering, material sciences and biology that there's an entire journal devoted to the subject.
In a recent issue of the journal Biofouling, the team reported promising results from a series of experiments in which they used electricity to stave off ferrying fauna. In preliminary experiments, they were able to reduce the accumulation of organisms by 50 percent.
"This was really a proof-of-concept paper," said Rodolfo Perez, an engineering graduate student at UW and lead author of the paper, describing the experiment, which was small scale and targeted bacteria, not barnacles.
But it indicated that the researchers' concept - "that no one would want to be electrocuted," said Perez - was correct.
He said the next step will be to "scale-up" the experiments, and try to figure out ways to rig ship hulls, as well as other objects, with electrodes. He said the U.S. Navy was particularly interested in their work because of the potential economic contributions it could provide. The Office of Naval Research funded the work.
Environmentalists, industrial manufacturers and medical researchers also stand to gain by their findings. The presence of microscopic critters on medical devices, dental equipment and water distribution systems are of concern because of their potential to harbor and introduce a variety of diseases.
Russell Cuhel, a biologist with the Great Lakes Water Institute, said that any effective biofouling method will also have an enormous effect on the Great Lakes region. Not only are boats in the lakes slowed down by aquatic organisms such as zebra mussels and algae, but the screens and grates on the intake pipes of water treatment plants are plagued by zebra and quagga mussels.
This reduces the efficiency of those pipes, causing the pumps that suck in the water to work harder, and therefore increases the amount of fuel needed to run them. In addition, the grates and screens protecting the pipes from debris also have to be cleaned, which requires time and money. As do the chlorine treatments required to kill the larvae of the mussels.
But it's for those who sail the seas that this research holds the most immediate and promising allure.
For hundreds, if not thousands, of years the shipping industry has loathed the latching ability of creatures such as barnacles, mussels, tube worms and sponges. When found en masse on a ship's hull, they create drag - reducing the speed of the vessel, thus requiring more fuel to maintain speed. In addition, the critters must be scraped off and the hulls repainted.
According to Linda Chrisey at the Office of Naval Research, a lot of time and money is spent on "hull husbandry," the maintenance and care required to keep the hull of a ship free from clinging aquatic organisms. It's estimated that millions of dollars every year are spent cleaning the hulls of Navy vessels with divers, remote submersibles, new paints and so forth, she said.
"This has plagued navies" since civilizations began using boats with any frequency, said Chrisey. "The Greeks and Romans worried about this." And it was these early navies that first started looking for ways to keep the clingers off. They discovered that copper worked pretty well. So, they started lining their wooden ships with this heavy metal.
Indeed, if you take a look at the USS Constitution, which is docked near Boston, you'll notice that it is copper-clad.
The problem, said Michael Hadfield, director of the Kewalo Marine Laboratory at the University if Hawaii, is that copper is toxic not only to animals wanting to catch a ride on a ship, but also to other animals in the marine environment. And as boats are maintained, and copper chips fall to the sea floor, there is environmental fallout. Other organic metals, such as tins, also have been used.
However, some of these were so damaging to the environment - in some cases wiping out entire ecosystems - they are no longer used anywhere.
So, the U.S. Navy and others are searching for an environmentally friendly, cost-effective and long-term solution that will solve the biofouling problem. For now, they are largely relying on paints with copper chips suspended in them. But, they are looking for other solutions.
One kind of paint, known as Intersleek, has been adopted by many yachters. It is a slippery, silicone-based paint that works by preventing animals from latching on. However, it very expensive, and because it is soft, it can get easily "banged up," Chrisey said.
And that's where Perez's work comes in. Although there's a lot of promise in these non-stick paints, the idea of using electricity to zap critters off - while not entirely new - offers another avenue of investigation with enormous potential.
Perez correctly reasoned that electro-shock therapy might dissuade creatures from making a home on a surface. Their experiments showed they were right. And although they performed their experiments only on bacteria - and non-marine bacteria at that - they, and others, hope the results can be applied on a larger, more applicable scale. Perez envisions a paint or an applique that is filled with thousands of microscopic, possibly nano-scale electrodes that would zap off organisms as they settled onto a surface.
But they still have a lot to figure out how to create such a lining and then test to see whether it is effective with all organisms, or just some.
The questions they need to answer, said Chrisey, are "Does it work? And if so, how much electricity do you have to use?"
For instance, if "you have to use 50,000 volts every 10 minutes" to keep the creatures off the hull, it's not going to be a practical or economically viable option, she said.