The TA Luft 2002 became effective for existing plants in November 2007. Caused by a significant tightening of waste air limit values, biological treatment processes seemed to be non realistic to obtain these values and were substituted by non-biological techniques. To demonstrate the applicability of biological treatment systems, a bioscrubber system, which was not conformable to the TA Luft 2002 values, was investigated. The progress of modernisation of the biological process was accompanied by analytical measurement directly on-site. The compound specific degradation potential of the plant was verified in laboratory scale.