Method for biological wastewater purification

A method for carrying out biological purification of wastewater with the aid of activated sludge in a wastewater treatment system, the method comprising:

• introducing the wastewater first into a tank for elimination of settlable solids of the inflowing wastewater, the storage of produced primary and excess sludge, and the reduction of a rising of the water level in the wastewater purification system (the S tank);
• and then
• introducing the wastewater into a tank for biological phosphor elimination (the P tank), wherein the volume of the P tank is mixed permanently or intermittently;
• and then
• introducing the wastewater into an activated sludge tank that is ventilated (the B tank) and then into a sedimentation and recirculation tank (the SU tank), in which at least one operating cycle is carried out over the course of a day, the operating cycles including a sludge return phase (the S phase), a recirculation phase (the U phase), a pre-sedimentation phase (the V phase), and a draw-off phase (the A phase), wherein the P tank is hydraulically connected with the B tank, and, wherein the B tank is hydraulically connected with the SU tank, wherein the S tank is hydraulically connected with the P tank via one or more openings;
• wherein consecutively, in the S phase a thickened activated sludge is introduced from the at least one SU tank into the P tank, in the U phase the volume of the SU tank is mixed, in the V phase the activated sludge is settled, and in the A phase treated water is drawn off, a flow of treated wastewater passes through the at least one SU tank only in the A phase, a rising water level in the phases S, U and V is provided and, therefore, a wastewater treatment system discharge corresponding to the wastewater treatment system supply develops (“filling up”-principle), and, wherein the at least one SU tank is not in an aerobic condition, wherein excess sludge present in the P tank is transferred from the P tank to the S tank.