Cleaning takes place in three stages. Wastewater from the household flows into the primary settling tank, where it settles. Undissolved, solid and floating substances are retained and settle like sludge in pre-treatment. The water then flows into the aerator where the bacteria carriers are.

A natural, biological film of microorganisms grows on the surface of the carriers, which biologically purifies wastewater by supplying air. The computer controls the operation of the compressor in two modes (day and night). The compressor takes care of the intensive turnover of the carrier substance and keeps the biofilm active. This achieves lasting good cleaning performance. The purified water settles in the clarifier. The sludge that had been brought on the swirling floating crib settles. The settled sludge is returned to the primary settling tank by means of an air pump.