A rotary system composed of two worms (1 and 2) which are built together and interconnected at their central coils by a pipe conduit (4), said worms having their respective coils oppositely directed to one another and consisting of spirally coiled pipes rotatable about a horizontal axis (3), is used for flushing and aerating a medium which is disposed in the pipes and coated with microorganisms. The microorganisms take up nutrients from waste water (6) in a biological purification process, one worm (1) with part of its periphery immersed in the water (6) lifting quantities of water towards its center, the other worm (2) lowering the water to the original level. This provides for alternate flushing and aeration, and the weight of the water in said second worm (2) provides a torque which contributes towards driving the system.

An apparatus for purification of waste water in a tank or a pool has a housing rotatably journalled on a raft and provided with pump means to force air and water therethrough. The housing contains first discs having central holes and a second discs having peripherical apertures at the wall of the housing. Each disc forms a baffle for air and water flows through the housing, thereby imparting a tortuous path to the air and water passing through the housing. The discs are corrugated and are arranged in a stack with the corrugations of adjacent discs oriented at right angles. The corrugations strengthen the discs and form support points at which the discs contact each other, and also define channels between the discs, through which channels of water and air can flow. A spiral pump rotating with the inlet end of the rotor forces metered volumes of water and air through the rotor.

Waste containing liquor is treated in a device containing a plurality of submerged, slowly rotating bacterial growth surfaces which are spaced apart from each other, extend in a horizontal plane and are mounted on a vertical, rotating shaft. The bacterial growth surfaces, which may be in the configuration of a substantially flat disk, are maintained submerged in a waste water treatment tank as the waste-containing liquor is passed over, through and around them. The tank may be provided with several sets of growth areas and shafts which are interleafed and separated from each other.

A reactor includes a reaction vessel that defines a reaction chamber. Completely or partially within the reaction chamber is at least one spiroid. The spiroid is operably associated with the reaction vessel so that rotation of the reaction vessel causes the spiroid to rotate and liquid to be transferred through the spiroid. The spiroid can circulate gas and liquid within the reaction chamber, introduce fresh gas and liquid into the reaction chamber or discharge gas and liquid from the reaction chamber.