Clearing the water - with air

STEVE GWIDT, an eccentric inventor from Rhinelander, Wis., would be pleased but hardly surprised: His invention has cleaned up the Suyong River in time for the Olympic Games, and a grateful South Korean government has honored one of its citizens for bringing the Gwidt approach to its attention. What was an odoriferous mess is now clean enough for the fish to return and for the yachting events that will take place there later this year. But Mr. Gwidt would have expected that. Back in 1972 he told a Wisconsin commission on economic development that his patented water-aeration device was so simple that ``any fool could see'' it could clean up the world's polluted waterways.

The commission, however, wasn't impressed. But one of its members found Gwidt's presentation interesting enough to take a second look. He was Joe Durda, a former Navy pilot and marketing expert who, with his son Dan, drove up to see the device some while later.

The machine, as the younger Durda recalls it, looked something like a one-man submarine.

Gwidt cared a lot about the environment, and in the Durdas he found receptive listeners.

Cleaning up humanity's organic waste - including some chemicals - is mostly a matter of turning it over to waste-consuming bacteria. There's no shortage of these workers in the nutrient-rich wastes, but there is a great shortage of the oxygen they need to work quickly. All that is needed to speed up the process is to pump in oxygen, and Gwidt had developed a machine to do the job.

Gwidt had absolute faith that his device would clean up lakes, rivers, and harbors everywhere. It would also prevent fish kills in frozen Northern waters and maybe even keep navigation channels free of ice. The Durdas were sure the man was exaggerating but saw enough in what he was saying to buy the patent rights. Now they believe that Gwidt was right.

Joe Durda believes that even the mighty St. Lawrence can be kept open with the help of the large aerators his Minnesota-based Aeration Industries International builds. (The company line ranges from a 1/2-horsepower machine frequently used in fish tanks up to the 100 hp. machines used on the Suyong River.) An experience early in the company's existence is the basis for this confidence.

In late 1976, the Sportsmen's Club and the Cedar Lake Improvement Association of New Prague, Minn., launched an urgent ``save the fish'' campaign. The quality of the water was such that there would probably not be enough oxygen to prevent a massive fish kill under the ice during the coming winter.

By Jan. 6 the lake's oxygen level had fallen to 2.4 parts per million, less than half the Department of Natural Resources' recommended minimum and barely above the 2 p.p.m. to keep fish alive if immobile. The Durdas hastily drilled holes through three feet of ice and installed six 2 hp. Aire-O2 machines.

One week later there was a mile-long stretch of open water where the machines had been installed. It was an event to be captured on home movies - but the film froze inside the camera.

More important, though, the lake's oxygen level had risen out of the danger zone and by March 10 had reached an abundant 8.4 p.p.m. The expected massive winter kill did not take place.

The town of Zumbrota was the scene of another triumph. When a new dairy operation began to overwhelm the waste treatment plant, the town was in trouble. The Minnesota Pollution Control Agency banned new construction in the area and threatened to fine the town and shut down the dairy, which had become the town's leading employer.

When the Durdas arrived with their entire inventory of twenty-seven 2 hp. machines, Joe Durda announced he would have the situation cleaned up in five days - and did.

What the elderly inventor had said would always happen in these situations did: Stirring up the water kept the wastes in suspension rather than settling on the bottom as a thick sludge. In the process the bacteria were circulated to all corners of the lagoon, along with the oxygen they needed to operate efficiently. They proliferated on a massive scale and the natural speed of decomposition was increased perhaps a thousand times. The mixing and stirring of the water by the Aire-O2 also accounts for its ability to keep water clear of ice during winter.

Aeration devices are needed wherever water can be depleted of oxygen by high fish populations or decaying wastes. Conventional aeration approaches include the paddle wheel, which throws surface water into the air where it absorbs oxygen before falling back into the pond. A second option is air hoses laid on the floor of the pond, bubbling air up through the water.

In a sense the Aire-O2 is a hybrid of these two. It is surface-mounted like the water wheel, yet it forces air deep into the water like the underwater hoses.

The machine consists of an electric motor above the water which turns a propeller at the end of a hollow shaft underwater. The propeller pushes the water outward from the end of the shaft, causing a vacuum that sucks air down through the shaft, where the action of the propeller breaks it into millions of tiny bubbles. Pushed away from the propeller, the oxygen-enriched water is distributed throughout the pond.

The machine was designed to clean up pollution but ``the waste-water market now accounts for only 3 of every 1,000 machines sold,'' Dan Durda explains. ``The rapidly growing part of our business is in Asia, where aquaculture is becoming a major industry,'' he says. Fish farmers have found that adding an aerator in their tanks or pens can increase stocking density from 4 to 10 times, depending on species. Eels, tilapia, and prawns are the major commercial species.

Slowly the older paddle wheel is being replaced in Asian ponds as farmers note the new aerator's efficiency. This in turn has prompted some copying of the Aire-O2.

Recently the Hitachi company began making an aerator ``suspiciously like'' the Aire-O2. The Durdas, who didn't fancy long, bitter patent battles with the Japanese conglomerate, found that Hitachi didn't want to argue, either. The net result of negotiations is a possible joint venture.

On the eve of playing host to the Asian Games late in 1986, the South Korean government found it had an embarrassing problem on its hands: the foul-smelling, almost black water of the Suyong River where it flows into Pusan Harbor, site of the major yachting events.

While the immediate need was to get rid of the odor for the Asian Games, Korean officials were even more concerned that the pollution be controlled well before the prestigious Olympic Games got under way two years later.

Nine of the big (100 hp.) Aire-O2s were installed across the river above the yachting marina, along with an oil fence to catch floating scum. Within a month increased oxygen levels had eliminated the odors and restored the environment so that fish and wildlife that had been absent from the river for years started to return. Hai Soo Kim, chairman of the company that distributes the aerators in Korea, was honored by the government for his introduction of the ``energy efficient'' products.

Because electricity is many times as expensive in Korea as in the United States, the aerators are not generally run 24 hours a day, as Aeration Industries' engineers recommend for optimum results. That will probably occur about the time the Olympic flame starts wending its way toward Seoul.

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