Traditional food product for modern water cleansing

Around 1.8 million of the world’s children die every year because they lack sanitary water. The technology of a Japanese enterprise is helping to reduce that number by delivering clean water for people in other countries at a low cost. Surprisingly, the technique involves a fermented soybean foodstuff called natto, which contains γ-polyglutamic acid. The acid is a flocculant, a gooey substance that makes particles clump together. This led developers to examine how natto’s flocculant power could cleanse water. When placed in a tank of water containing suspended microorganisms and tiny particles, the flocculant turns them into big, heavy clumps. The result, which is actually easy to achieve, is water that would pass the sanitary standards of various countries.

Clean, safe-to-drink water in Bangladesh, courtesy of the cleansing technology of Poly-Glu Social Business Co., Ltd.

The local community enjoys clean water just by adding an agent that causes suspended particles to clump together and sink.

The flocculant material is harmless and natural, and the method requires no special equipment. The technique has spread to countries including Bangladesh, Brazil, Colombia, India and Tanzania. It is also used in camps housing Somali refugees, improving their lives.

Photocatalysis: A clean energy source changing hydroponics

The rows of tomato plants on the right are growing in water processed in a recycling system developed by the Hashimoto Laboratory at the University of Tokyo. The tomato plants on the left are grown the conventional hydroponic way, showing the remarkable difference between the two methods.

Hydroponic farms grow plants indoors, without the use of soil. Instead, the roots lay in water containing a mixture of mineral nutrients and fertilizer. Because the weather and pesky insects have little chance of harming the plants, farmers feel they can count on consistent yields.

During the growing process, however, organic matter seeps into the nutrient solution from the roots, hindering plant growth. The water has to be filtered to remove the organic matter, then recycled back to the plants. But now a new method has been developed. It breaks down the organic matter with titanium oxide, due to its photocatalytic effect in light. The process breaks down the organic material easily, with no need for an electricity-consuming filtration system. Developers report that, thanks to the system, tomato harvests have increased about 30%. And the solution can be reused, instead of being flushed away. This cuts down on the amount of solution required and prevents phosphorus and nitrogen, which are nutrients in the solution, from seeping into soil and rivers.

Less impact on the environment, and bigger harvests—this system will soon change hydroponic farms, which are part of a growing industry in Japan.

Saltwater fish in a highland spa?

Noguchi Katsuaki, the president of the aquaculture company, Dream Creativity Ltd., checks the condition of the facility’s tiger puffers.
Bottom right: One of the puffers that has done well in spa water. (Photos: Ito Chiharu)

Tochigi Prefecture north of Tokyo has no seacoast, but it does have saltwater fish swimming in tanks. The fish are tiger puffers, and the place is Nakagawa-machi, a town nestled in the mountains. But why there? The answer lies in the fact that the town has springs of warm water bubbling up to the surface. At about 20 °C, the water is cooler than at most hot springs, and it contains no sulfur or other noxious minerals. In addition, its salt content ranges from around 0.9% to 1.2%, about the same as found in liquids in the bodies of living creatures. A local enterprise zeroed in on these advantages and succeeded in raising tiger puffers, a fish that is very expensive in Japan.

The natural habitat of tiger puffers is seawater, which has a salt content around 3.5%. Puffers have to reduce that salt density to around 0.9%, and they do this while absorbing water through their gills. Since the salt density of the spa water is about that same 0.9%, the fish do not need to adjust the salt content, saving their energy. And in addition, they have the advantage of plenty of nutrients. This explains why they can grow larger than their counterparts in the sea.

After tests, tiger puffer aquaculture began in Nakagawa in 2009, with 1,150 fish. By 2014 the facility’s annual production was 40,000 ready-for-market fish. The mountain town had faced a decline in its population, but now it is ready to develop a new industry.