A newly built pilot plant system consisting of four different treatment streets, two of which have a biological character, and the other two a physical/chemical character, has been intensively tested during a period of almost one year. These tests are expected to last until August 1996. The objective of the investigation is to find the economically and technologically optimal configuration of treatment steps. This should finally result in the choice and design of a permanent treatment system.

The coagulation/flocculation/sedimentation techniques, as a part of the physical/chemical treatment systems proved to be very unstable, unreliable and very difficult to control. Stable operation conditions were reached only during a few days. Removal efficiencies were very low.

The activated sludge system as well as the biofilm system had very high performance rates. For most of the components very high removal efficiencies could be reached. The addition of PAC to the activated sludge caused a slight increase of the removal efficiencies. UV/ozone tested as a cracking process between two biofilm reactors did not show any improvement. Also the use of UV/ozone as a post treatment system was not very successful.