By installation of lamella in the activated sludge tank an increase of biomass concentration in the activated sludge tank can be achieved without additional charge of the secondary clarifier. Integrated packages of lamella which are installed in the discharge of the activated sludge tank at an angle of 60° effect a partial sedimentation and so a MLSS-preseparation.
The MLSS in the activated sludge tank (influent of the lamella construction) was 6.5 g/l, the MLSS in the influent to the final clarifier (effluent of the lamella) was 3.1 g/l. That means that the lamella increased the MLSS concentration in the activated sludge tank by a factor of two. Despite a volume loading of 1.24 kg BOD5/(kg MLSS • d) a complete nitrification could be obtained. For ensuring a stable process and a balanced concentration of the biomass in the influent of the secondary clarifier, the preseparation of solids in the lamella is controlled by addition of air bubbles.
By the enhancement of biomass concentration using this preseparation device, the extension of waste water treatment plants can be carried out with lower investment costs.