Gunma: College headmaster invents device to purify water, raise sea oysters

Akira Kojima, head administrator of the International Industrial Technical College in Maebashi, demonstrates the oyster cultivation box he invented. (Credit: The Yomiuri Shimbun)

MAEBASHI -- A steel device that raises bigger and more delicious oysters just by submerging it in the sea is the brainchild of the head of a technical college in Gunma Prefecture, the invention of which was an 11-year process.

Akira Kojima, head administrator of International Industrial Technical College in Maebashi, invented the device which measures about 15 centimeters long, 15 centimeters wide and 40 centimeters tall. It contains charcoal, which draws the oysters' eggs toward it, and leaf mold, which produces the phosphorus necessary for the oysters to grow.

The box has numerous holes, each roughly 5 millimeters in diameter, through which the components are designed to leak out. As the iron of the device is gradually broken down by the seawater, the iron concentration in the water rises and causes an increase in the amount of plankton, resulting in water purification.

(Credit: The Yomiuri Shimbun)

Kojima previously served as a specially-appointed professor at the National Institute of Technology, Gunma College and has improved the water quality of rivers and ponds in a number of projects through the use of charcoal.

Hoping to help the areas affected by the Great East Japan Earthquake, Kojima in 2012 conducted preliminary tests on the device in Yamada, Iwate Prefecture. The results proved that the weight of the shelled oyster meat increased by 30% and the amount of glycogen, an indicator for umami, increased by 70%. However, the effects were found to differ based on location.

All experiments conducted in Hiroshima Prefecture since 2018 have focused on the device's effectivity of improving water quality.

It was found that the more phosphorus seawater contained, the larger the oyster meat grows. The device then was improved to be able to produce sufficient growth in any area of the sea by adjusting the ratio of charcoal and leaf mold in the box, depending on the water quality.

Kojima has already established a system to mass-produce the device in cooperation with a local company and plans to sell it nationwide as the Takarajima Box.

Read more from The Japan News at https://japannews.yomiuri.co.jp/