A wastewater treatment plant was having serious problems with the build-up of clumps in their sludge. The choppers installed were not able to cut up the voluminous clumps in a passable size. This caused constant blockages in the rotary pumps which were supposed to keep the contents of the digestion tower circulating. The operator of the plant decided to try out a Börger Rotorrake. The Rotorrake is a robust chopper in inline design. Blades and counter blades are mounted one after the other on the carrier shaft.

The Rotorrake was tested intensively for a long period of time. During that time, no problems occurred with the Rotorrake and no signs of wear could be detected on the blades or counter blades after the test phase.