Instead of a planned two stage activated sludge plant the design was changed to a single stage activated sludge plant with enhanced biological phosphate removal and pre-anoxic zone denitrification. For flexible operation it is possible to vary the rato of VD/V from 0.3 to 0.5. Problems with the aeration equipment in the nitrification/denitrification cells occurred and were solved. The circular clarifiers are equipped with scrapers. Instead of a sludge hopper a collector in the centre of the tank was constructed.

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