Australia Up Close College Engineers Aim To Fight Pollution By DARREN McLEAN	フレームで見る  英文をプリントする  脚注をプリントする
オーストラリアで水質浄化の新兵器 集約化農業による肥料の大量流出や土地開発などによって、湖や貯水池の汚染が進んでいます。そんな中、オーストラリアの大学生たちが、水質を向上させる低コスト・高パフォーマンスの新装置を開発しました。プロペラを使ったこの奇妙な装置の仕組みとは？

Two engineers in Australia have invented a device that could soon be used extensively in Japan. A student and a teacher at Griffith University's School of Engineering have designed a mechanical circulator for lakes and reservoirs to solve a range of water quality problems such as bad odor and taste, fishkills and algae accumulation.

The mechanical circulator could have massive international potential, especially in Japan. The Lakes Country Club, northwest of Tokyo, had success using similar mechanical circulators after its lakes became seriously polluted with thick sediments and algae. Not only were these conditions unsightly and unhealthy but the lakes gave off a terrible smell.

The pollution was partly due to fertilizer and waste water that had washed into the lakes. Also, in the hotter months the surface level of the lakes become considerably warmer than the lower levels, creating a temperature barrier that stops any natural exchange of water between the top and bottom. The organic material at the bottom of the lake decomposes, using up all the dissolved oxygen in the water.

An underwater environment without oxygen not only means that fish and prawns can't survive, but it causes a range of water quality problems. Toxic algal blooms cause thick smelly sludge and the water becomes contaminated with metals. All of these conditions can endanger people's health.

Several methods have been tried in an attempt to solve these problems. Greenkeepers at the Lakes Country Club first tried cleaning the lakes manually, dragging the unwanted vegetation and sediments out of the lakes. This task, however, must be ongoing and is not appropriate for larger water bodies.

Another method involves pumping compressed air into the bottom of the lake or reservoir, adding oxygen to the deeper water, and moving water closer to the surface. This proved to be quite ineffective, using large amounts of power for little benefit.

The best way to overcome the problem is by forcing an exchange of water between top and bottom layers to transfer oxygen from the surface to the desired depth. This can be done by mounting a large motor-driven impeller below a floating pontoon. Similar to an upside-down helicopter in appearance, this mechanical circulator pushes the surface water down.

The mechanical circulator designed at Griffith University generates a slow, steady flow using minimal amounts of power. Recent tests show that the Griffith design is the most energy-efficient ever reported. It will also prove to be more cost effective than any other design,including those used in Japan at present.

Stephen Elliott designed the mechanical circulator for a student research project. He describes the design as cutting-edge technology. "The impeller revolves at only 25 rpm, which is very slow compared to other designs, making it quite a unique piece of machinery," said Elliott.

Brian Kirke, a lecturer at Griffith University and codesigner of the mechanical circulator, believes more and more people will soon be looking for ways to keep our water supplies clean. "Agriculture and development is becoming more and more intensive all over the world," said Kirke. "This means our lakes and water supplies are being put under increasing pressure due to more fertilizer runoff and larger amounts of waste pollution."

Although the invention is in its early stages, the inventors can see large commercial potential for the mechanical circulator. At present they are negotiating marketing and manufacturing deals with local companies and are focusing on installing the design in several Australian lakes and reservoirs.

Elliott and Kirke have already received a grant from Griffith University to purchase sophisticated measuring equipment to further their research.

There is no doubting the enormous potential for inventions that keep the Earth's water supplies healthy. After all, everybody needs clean water.

Shukan ST: April 10, 1998

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