Abstract: A plurality of containers are combined in a stepped manner into a container group. Each container opens downwardly. They are sunk under water and anchored to the bed of the sea. A notch is formed at a lower portion of a side wall of each container connected to the next container so as to permit air to pass therethrough. Air is supplied into the interior of the lowermost container. The air is delivered to upper containers one after another through the notches and accumulated in all interiors of the containers. A staircase is disposed in a position spaced from the container group by a predetermined distance. A diver can use the space between the staircase and the container group. Furthermore, a diver can step down from the uppermost container to the lower ones one after another, so that he can also get deep into the sea without any scuba equipment or air accumulator.

Abstract: A multi-gas-phase settling tank has a plurality of containers mounted upside down in vertical spaced relation at fixed intervals for holding a predetermined quantity of gas under water. Each container has a flat horizontal wall, side walls extending downwardly therefrom, a vent port in the flat horizontal wall and a hollow projection extending downwardly from the vent port for a shorter distance than the height of the side walls. The containers can be mounted at their corners in relation to each other or on inner walls of a settling tank.

Abstract: A multiple-gas-phase liquid treatment apparatus for use, for example, as a gas dissolving apparatus, gas removing apparatus, sewage treatment apparatus, or large-quantity culture apparatus includes a hollow container, a plurality of horizontal partition plates mounted in the hollow container to define a plurality of vertically-stacked liquid treatment chambers, a pouring port for introducing liquid to be treated into an upper portion of the hollow container, a discharge port for removing treated liquid from a bottom portion of the hollow container, a gas vent port for introducing gas into the bottom portion of the hollow container, and a hollow tube connected to each horizontal partition plate and extending a predetermined distance downwardly therefrom. Liquid introduced into the top portion of the hollow container flows from one partition plate to an adjacent lower partition plate through the hollow tube in each partition plate.

Abstract: The present invention comprises tray-like shallow vats placed upside down and horizontally at intervals in a culture tank so as to provide partitioned air spaces in mid water. When gas is sent, via an air supply pipe, into an air space provided at the bottom vat, a good number of artificial environments, in contact with an atmospheric environment in a manner similar to the natural surface of the water, are efficiently provided in the culture tank.