For the treatment of larger wastewater volumes, two or more KLARO container.blue systems are required. In such a case, the identically equipped systems are installed so as to operate in parallel. The systems operated in parallel are steadily fed with raw wastewater via a joint wastewater collection tank (1) and pump stations (2) (integrated in the wastewater collection tank or via external pump stations). This way, the irregular afflux may be balanced out and distributed equally to the systems. In the systems (3), the distributed wastewater is then treated via the innovative, modified SBR procedure before it is drained into receiving water (stream, river or lake).