God of water cleanses water if it flow about one inch.

---This is a Japanese proverb.
@In Japan, about 50 years ago, sewer drainage equipments did not spreads as today. The back of a private house, there was a digs of soil, and the sewage flow through the digs.

A simple water cleaning system of old house in Japan

Ground cherry

The filthy water from a kitchen poured to the dig and flow to a pond , which played a shock absorber of the flow. We called the system as SESENAGI in Japanese. The person memorizing the word SESENAGI are very rare at most near. In Japanese proverb, say, "If a water flows through 1 meter, then the stream is clean completely. In an old book in Japan, say "a god of water cleanses the water if the water flow 10 cm". It is this SESENAGI that show this proverb concretely. Several meter ahead from water inflow point, widen the width of a ditch and water stagnates and drifts. Because this place was the place that was dirty with both bad smell A which drifted and covered with many plants. In summer, It is a playground of happy children , where an uncrowded growing up many plants, butterbur(Fig. ), etc, and tree of persimmon were training place of tree claiming. It is the splendid device that took advantage of dirty place. Even if the flow increased temporarily, this damp area had buffer action and prevented filthy water from flowing out to the down stream. SESENAGI was a natural history laboratory of children. It is a really symbolic incident of cultural history that a word of SESENAGI was forgetting out from the people. It is a city sewage disposal plant which concentric and effective operation in a industrial device. A principle of an activated sludge method is the SESENAGI itself. This simple processing of house dust in every house, now doing by a city unit. In other words, the relation with the next house, changed into it in a city unit. In Japan, the YODODAWA water system which from lake BIWA to OSAKA city is a typical sample. However, is decisive difference between them Grime is burnt up, but is dangerous in nature. Because there is various poison coming from a life waste of the present age in the ash. Most burn it up and dispose, and ash is filled up. Because I throw it away in a mountainous district , they pollute undergound water in long time and fall on a human being. It is a bad inheritance of modern people toward the 21st century.