The contact reaction tank is filled with sewage, and the turntable alternately contacts with air and sewage. After a period of time, a biofilm inhabited by a large number of microorganisms will be attached to the turntable. The species composition of microorganisms is gradually stable, the metabolic function is gradually exerted, reaching a stable level, and the organic pollutants in sewage are adsorbed and degraded by biofilm.

The turntable rotates away from the sewage and contacts the air. The fixed water layer on the biofilm absorbs oxygen from the air, and the oxygen in the fixed water layer is supersaturated and transferred to the biofilm and sewage, so that the dissolved oxygen in the sewage in the pool has a certain concentration or even saturation. The biofilm gradually thickens, forming an anaerobic layer inside and starting to age. The aged biofilm falls off under the shear force of sewage flow and disk surface, and the fallen biofilm is trapped in the secondary sedimentation tank, and the sludge formed by the fallen biofilm has high density and is easy to precipitate. Therefore, if the biological turntable system is operated properly, it also has the functions of nitrification, nitrogen and phosphorus removal.