Substitution of the final clarifier by membrane filtration within the activated sludge process with increased pressure; initial findings

The Institut für Siedlungswasserbau, Wassergüte- und Abfallwritschaft of the University of Stuttgart has performed a series of tests with the activated sludge process at increased pressures over a long period. The advantage of this process is that it increases the activated sludge content by improving the oxygen supply. This advantage is accompanied by a decrase in the production of excess sludge as an additional benefit. A major disadvantage of this process is the fact that the separation of the activated sludge from the water has to be done at the same pressure as that applied to the biological reactor as a result of the choice for a continuous operation. This fact leads to technical difficulties. Tests carried out with membranes in another research project suggested that membrane filtration could be effective for solid/liquid separation. Our initial findings clearly confirmed this, even though the testing conditions were not optimal.