Using sound to protect aquatic life

April 22, 2013 by James M. O'neill

The large cargo ships that steam daily into Newark Bay unload more than the colorful containers stacked on deck - from their holds they also can release millions of gallons of water teeming with tiny sea creatures from faraway ports-of-call.

These aquatic stowaways, which sometimes thrive in New Jersey's local waters, can harm fisheries and clog the intake pipes of drinking water treatment facilities and power plants.

As a result, the U.S. Coast Guard has ordered ships to treat ballast water and kill off any organisms. The most common treatment methods, however, involve chemicals, which then need to be discarded, or ultraviolet light, which can't penetrate murky water.

A Montclair State University professor has been working on a contraption that could avoid those issues by treating the water with something quite simple - .

"Ultrasound has special properties that have already been in use as a disinfectant to control unwanted organisms, such as bacteria in laboratories or surgical settings," said Professor Meiyin Wu, a biologist and director of the Passaic River Institute. "It has been used to disinfect swimming pools and drinking water."

Locally, many invasive species have taken hold.

The Asian shore crab arrived in New Jersey in 1988 and has since spread to New England and North Carolina. "You can come across them in huge numbers," said Judith Weis, a marine biologist at Rutgers University. "They reproduce very fast and have no strong site fidelity - they'll wander around, which helps them spread further."

Green crabs, which were introduced into Raritan Bay from Europe a century ago, have also spread to Maine, where they have damaged shell fisheries, Weis said. She has seen the Chinese mitten crab, a new invader within the past decade, in the Hudson River. It digs burrows in riverbanks, which can speed erosion.

Montclair State Robert Prezant has studied the , which was released into Canada about a century ago and has since spread across the United States - including into the Passaic River. Prezant said they can grow in concentrations of up to 20,000 per square meter. "They're like a layer of concrete on the riverbed," he said. "They compete with the native species of freshwater mussel for the same food sources."

The zebra mussel, which has ravaged the Great Lakes since it arrived in ship ballast water from the Black Sea, has not yet reached New Jersey, Prezant said. "But it will get here," he said. The state has a zebra mussel watch program in place.

The Coast Guard rule about treating ballast water applies to new vessels built after December of this year and will apply to older vessels beginning with their first dry-docking after January 2016. Ballast water is taken on or released from a ship to help keep it balanced while being loaded, unloaded or traveling in the open ocean.

In 2004, the Coast Guard started requiring ships to exchange their ballast water while at sea, but the results have been mixed. Some organisms can still remain in sediment at the bottom of the ship's tanks and the process can be dangerous - a number of ships have capsized, said Douglas Schneider, vice president for government affairs with the World Shipping Council. If there is bad weather, the exchange can't be attempted at all.

Standard container ships can carry more than 5 million gallons of ballast water, Schneider said, with large crude oil carriers holding 10 times that amount. Up to 3,200 ships call each year on the six container terminals operated by the Port Authority of New York and New Jersey, with the bulk of them landing at Newark and Elizabeth.

The cost of installing a treatment system can be $1 million to $2 million per ship, not including the lost revenue from having the ship out of service for several months.

Montclair State's Wu came to the ballast water issue indirectly, while she was researching how to control the spread of the water chestnut plant on Lake Champlain.

The water chestnut is an invasive plant from Eurasia that floats on the water and can grow into dense impenetrable mats that block light from reaching native species growing beneath the water - species that fish and other organisms rely on.

But collecting the plant is slow and costly and trying to kill it with chemicals has other side effects.

So Wu contacted Junru Wu (no relation), a physicist at the University of Vermont, who had done ultrasound research for 25 years. "It can be very useful to kill the bacteria growing in milk and apple cider," he said.

Junru Wu figured that ultrasound might work on the water chestnut because it relies on an air pocket to stay afloat. The sound waves could burst the air pocket, sending the plant to the lake bottom to decompose.

Their lab tests worked. But it was one thing to target the water chestnut in a controlled laboratory environment - it would be harder and less practical to treat it in a 500-square-mile lake.

To attract more funding, Wu needed to figure out a way to apply her work to other irritating species. The two researchers were able to secure a $673,000 federal grant because the U.S. government was looking for ways to reduce the widespread impact of invasive species introduced through ship into the Great Lakes.

The device that they developed - which they call a BallastSolution - looks like a stylized, elongated metal porcupine. The machine can send sound waves at frequencies above the range of human hearing through the water as it flows through a pipe.

They built their device in Vermont, then took it apart, packed it into a van, drove it down to Montclair State, where Meiyin Wu had been hired, and reassembled it.

For the past year and a half, they have been testing its effectiveness at killing off the larval stages of many invasive species. They have also tested it on the larvae of mosquitoes.

They have been able to kill off 99 percent of organisms present in the water. It takes 10 to 20 seconds of exposure to the sound waves for the water to be disinfected, Meiyin Wu said.

She and Jenru Wu are talking to a number of potential investors to bring the device to the market.

"The ship owners' primary interest is to buy a technology that works," said the World Shipping Council's Schneider. "They want the confidence in it given how costly it will be. If acoustic blasting works, it will certainly have a market."

Explore further: New requirements for ballast water dumped by ships


Related Stories

New requirements for ballast water dumped by ships

March 29, 2013

(AP)—The Environmental Protection Agency has issued new requirements for cleansing ballast water dumped from ships, which scientists believe has brought invasive species to U.S. waters that damage ecosystems and cost the ...

Coasts' best protection from bioinvaders falling short

November 4, 2011

Invasive species have hitchhiked to the U.S. on cargo ships for centuries, but the method U.S. regulators most rely on to keep them out is not equally effective across coasts. Ecologists from the Smithsonian Environmental ...

Fighting ecological invaders efficiently

May 11, 2012

Siemens is using a special water-treatment technique to make ship traffic more environmentally friendly. By disinfecting the ballast water in ships, a system named Sicure protects marine environments from damage due to the ...

Microbial stowaways: Are ships spreading disease?

May 29, 2008

Ships are inadvertently carrying trillions of stowaways in the water held in their ballast tanks. When the water is pumped out, invasive species could be released into new environments. Disease-causing microbes could also ...

Scientists block ship-borne bioinvaders before they dock

March 28, 2011

The global economy depends on marine transportation. But in addition to cargo, the world's 50,000-plus commercial ships carry tiny stowaways that can cause huge problems for the environment and economy. A new model created ...

Recommended for you

New discovery challenges long-held evolutionary theory

October 19, 2017

Monash scientists involved in one of the world's longest evolution experiments have debunked an established theory with a study that provides a 'high-resolution' view of the molecular details of adaptation.

Water striders illustrate evolutionary processes

October 19, 2017

How do new species arise and diversify in nature? Natural selection offers an explanation, but the genetic and environmental conditions behind this mechanism are still poorly understood. A team led by Abderrahman Khila at ...

Gene editing in the brain gets a major upgrade

October 19, 2017

Genome editing technologies have revolutionized biomedical science, providing a fast and easy way to modify genes. However, the technique allowing scientists to carryout the most precise edits, doesn't work in cells that ...

Gut bacteria from wild mice boost health in lab mice

October 19, 2017

Laboratory mice that are given the gut bacteria of wild mice can survive a deadly flu virus infection and fight colorectal cancer dramatically better than laboratory mice with their own gut bacteria, researchers report October ...


Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.