For a biological cleaning action on soiled waste water, where the water flows through basins with plant roots to give a physical/chemical/biological cleaning, oxygen is introduced in partial zones of the base of the basin by mechanical or chemical delivery. Pref. mechanically delivered O2 is pure over pressure or compressed air passed to the base of the basin through porous tubes within the base from a closed tube feed. The porous tubes are laid across the water flow direction in a number of parallel or ring-shaped rows, according to the basin dimensions and shape. The porous tubes are covered by a coarse pore and/or loosely spread material such as ground plastics waste. The compressed air can be heated above its' compression heat, for winter use, using heated exhaust air from livestock buildings. The compressed air can be provided by a fan, or a blower powered by a wind wheel. In operation, the amt. of compressed air produced is altered by a control circuit according to the redox potential measurements at the base of the basin. O2 can be produced in an electro-chemical process, with a wind wheel to generate the electrical energy required. ADVANTAGE - The technique gives the correct conditions for the plant life and, in turn, their action on the water passing through for cleaning.
