The BIOCOS-process represents a cyclic activated sludge system that has been developed at the University of Innsbruck (Prof. Ingerle) throughout the last 15 years. Typically the aeration Tank (B-tank) is hydraulically connected to two alternating sludge recycling and –settling tanks (SU-tanks). A RAS pump-station or any electro-mechanical equipment for stirring or cycling are not required – all phases of the operation cycle are exclusively driven by pressurized air (see operation cycle in figure below):
- Sludge recycle (S-) phase: Recycling of settled sludge (thickened bottom layer) to the B-tank by means of an air-lift.
- Mixing (U-) phase: Mixing of the SU-tank by a roll current induced by coarse bubble aeration.
- Discharge (A-) phase: Intermittent aeration in the B-tank for nitrogen removal and continuous discharge of supernatant water from a SU-tank (no water-level variation).
- Settling (V-) phase: Settling sludge layer – formation of a floc-filter and a dense bottom sludge layer.