Nothing looks unusual about the three seafood processing plants located next to each other on the Portland waterfront, but they may be the only seafood producers north of Boston using a clean, green technology to make seafood safer.

Their not-so-secret is ozonated water — a technology employed throughout the bottled water industry and used for swimming pools and spas all over California and elsewhere, but not widely used in the seafood industry. Yet.

“Fish guys, if they don’t have to spend money, they won’t,” said Jerry Knecht, president of North Atlantic, Inc. on the Portland Fish Pier. He figures North Atlantic’s total investment in the system is $25,000 including plumbing.

Ozone in the water kills 99 percent of all bacteria within seconds of contact, whether it’s on the fish, the cutting counter, the floor, the truck. Anywhere. Killing bacteria on the fish means not only a safer product for the consumer, but a longer shelf life for the fish.

Longer shelf life means the producer can guarantee the customer, whether it’s a retail store or a restaurant, a longer-lasting, higher-quality product.

Knecht was the first to install a machine to put ozone into water in his fish plant seven years ago (WWF March 2005). That machine produced only 10 gallons a minute, but the in-house lab at North Atlantic showed the ozone was doing its job. When a better machine became available, Knecht installed it.

North Atlantic, Inc. has been doing business on the Portland waterfront since the early 1980s. The company has shifted its business focus to accommodate changing times in the seafood industry, but one thing has never changed.

“Our stock in trade all along the way has been shelf life extension,” said Knecht. Now he can claim, with independent lab testing to prove it, that his product and the plant are 99 percent bacteria-free.

When North Atlantic realized the advantages of ozonated water, the company had co-pack arrangements with two of its neighbors on the pier — Bristol Seafood and SeaFresh. The two processors agreed to install ozone in order to meet the North Atlantic standard, and now they’re hooked on it.

Before Bristol installed an ozonated water system, it called in an independent testing service to take baseline readings of bacteria levels in six crucial spots throughout the plant.

The bacteria levels were duly recorded. Five weeks later, after the new ozone system was turned on, the independent testers came back to take random swabs of the same six spots in the plant.

“They called right after the second round of tests and said they wanted to come back again because something was wrong,” said Kevin Murphy, Bristol plant manager. “The bacteria counts had been reduced a thousand fold,” said Murphy. “The counts were so low, they couldn’t believe it until they did the tests a second time.”

Larry Lindgren, general manager of the Sea Fresh plant and longtime sales manager next door, said he “became a devotee when I was at North Atlantic. We had the first one north of Boston. When the spa industry picked it up commercially, then they built machines that could produce gallons per minute to keep up with the work pace.”

Ozone as a sterilizing agent has been around for more than half a century. For instance, ozonated water has been used in the citrus fruit industry for a long time to spray the outside skins of fruit before shipping to kill mold and fungus. In 2001, the U.S. Federal Drug Administration approved ozone for use on raw proteins, including seafood.

Ozone is nearly ubiquitous in the bottled water industry, large public water and wastewater treatment systems, swimming pools and aquariums. Ozone in different forms is also used in wildly different industries. such as growing plants, to provide a healthier environment for raising farm animals, and cleaning semiconductors.

Paper mills are starting to use ozone in place of chlorine, thereby eliminating the production of dioxin. Many experiments are being performed in the medical and dental fields as well. Ozone gas is a sanitizer often used to treat vegetables by injecting the gas into a closed container to kill bacteria, for instance, on potatoes.

At Bristol, they’ve been using ozonated water for nearly six years — in the plant’s ice, for rinsing fish before and after cutting, for washdowns of surfaces (including trucks and the front of the building), in the air in some areas, and as a big marketing tool because of the two or three days of extended shelf life low bacteria levels give the product.

Ozone is merely “three oxygen molecules stuck together” which makes it unstable, said Swenton. “Oxygen likes to be at two molecules because it’s stable at two. At three it will attach to something when it comes in contact with it, such as hydrogen, it will become water — or carbon, it will become carbon dioxide.”

Ozonated water is created by first extracting oxygen from the air by running it through a corona discharge unit, then exposing the oxygen to electricity to create ozone gas. The ozone gas is pumped into the water in a dedicated plumbing system.

“Bugs can develop a resistance to chemicals,” said Swenton. “Unlike chlorine, which is basically a salt, nothing can build up a resistance to ozone. When it comes in contact with bacteria, it kills them because it’s unstable.”

“Chemicals attack the DNA, the cell of the bacteria. Ozone explodes the cell wall. Ozone not only destroys listeria, but for some reason listeria is particularly sensitive to ozone. It kills listeria before eColi,” said Peter Rubenstein, president of Pressure Techniques Inc., of Haverhill, Mass., installer of the ozone systems. “Of course, they’re all killed in seconds anyway.”

Resistance — So, why doesn’t every seafood plant in the world, or at least the U.S., have an ozone system? Some processors may resist ozone because of the many myths that circulate about it.

One myth is that any off-gassing, or release of excess ozone into the air, is dangerous.

“What doesn’t come out in the water, comes out as gas,” said Rubenstein. If ozone is in the air, the human nose can pick up the scent at as low as 40 parts per billion (ppb). It’s the same smell that occurs after lightning strikes, creating ozone through the surge of electric energy reacting with the oxygen in the air.

“If there’s too much, you’ll smell it a mile away,” said Rubenstein. There is little risk unless the amounts are excessive, there is no ventilation and leaks of the gas are so regular that workers become desensitized and unable to smell it.

“This is where claims come in — it separates one brand of machine from another — the efficiency of how the mixing of gas and water is done,” said Rubenstein. “Hopefully the water comes out 100 percent saturated. Otherwise, some machines have an off-gas destruct unit. Ours doesn’t have one because there’s no off-gassing. That’s the efficiency you’re looking for.”

The ozone levels used for ozonated water in a seafood plant are tiny compared to the large scale use of ozone gas for treating large water systems or in the bottled water industry.

Caution is required in order to use the ozonated water properly. Lindgren points out that plumbing must be installed properly to maintain the proper level of ozone in the water at each point of use. “Proximity is a big thing. You don’t want it to dissipate. It has to be working full tilt to keep the 99 percent kill rate.”

The Portland plant is the “little brother” to a larger plant in Rhode Island. Most of the fish processed at Sea Fresh in Portland is monkfish and skate shipped to Europe. Bristol specializes in fresh North Atlantic fish, frozen at sea fish and scallops.

At North Atlantic, fish is imported from Asia and South America for the U.S. market. The company also imports a lot of farmed salmon from Newfoundland.

“You can’t leave ozone water in salmon. If it’s exposed for too long, it bleaches the salmon,” said Knecht. “You just need enough time to get the bacteria kill rate, then it’s dried with filtered air to get rid of the water.”

Ozone machines cost from around $20,000 to $40,000 depending on the output. “A bigger machine doesn’t put out better ozone,” said Rubenstein. “Ozone is ozone. Plumbing installation for a small plant could be as little as $500 and a large one, $10,000.”

Bristol uses some ozone in the plant’s air purposely. “We use ozone air in the thawing unit and the ductwork in the lower room,” said Murphy.

“It reduces odors,” said Swenton. “It’s especially useful when dealing with waste.” Swenton pipes ozonated air into his office as an air freshener.

When Bristol installed the first system, nearly six years ago, chemical suppliers warned them they wouldn’t be happy with it, said Swenton. They weren’t, but it wasn’t because of the ozone, it was because their first supplier wasn’t “user friendly.”

Use of ozone has cut chemical costs at Bristol from $9,000 a year to $2,000. The cost of additional electricity to run the quiet, 20-amp ozone equipment is minimal, “like another small appliance running in the plant,” said Swenton. “Probably less than your refrigerator at home.”

“Then there’s water, but we use that anyway,” said Murphy.

Annual maintenance averages between two and three percent of the machine’s cost. Machines require some user maintenance, such as changing filters.

A dedicated plumbing system installed for Bristol’s first system cost $1,200, said Murphy. A couple of years later, when installing Rubenstein’s system, a more extensive plumbing network added to provide 25 “drops” for the ozonated water covering 24,000 square feet in the plant, cost $6,500.

“One of our potential customers won’t buy our product because of the ozone — he says he only wants all-natural product,” laughed Ray Swenton, president of Bristol. “What’s more natural than oxygen?”