The capacity and efficiency of the existing activated sludge waste water treatment plant at SCA Graphic Laakirchen AG needs to be enhanced due to an expected future increase in waste water flow and COD-load. For the case of an existing upper limit of COD discharges into the river, the COD reduction rate of the waste water treatment has to be increased to a degree which is unobtainable by biodegradation only.

Laboratory and pilot plant trials using a moving bed biofilm technique and an activated sludge treatment combined with ozone treatment and subsequent biofiltration have been performed with the aim to increase the COD reduction capacity and efficiency of the plant.

The results show that the COD reduction capacity of the existing activated sludge plant can be increased by more than 100% by integrating a moving bed biofilm pre-treatment stage into the plant. In addition, improved sludge separation in the secondary clarifier was established. A special benefit of the ozonation plus biofilter treatment is a controllable COD reduction between 20 - 90% related to the outflow of the activated sludge plant.

It is concluded that by integrating the investigated treatment techniques in the existing activated sludge plant the future increases in waste water flow and COD-Load can be handled satisfactorily without increasing bioreactor volume.

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