Biological treatment of potato-starch wastewater - design and application of an aerobic selector

The effluent of a potato-starch factory is separately treated in a two-stag e activated sludge plant. The occurrence of bulking sludge in the second bi ological stage due to excessive growth of type 021N was repeatedly observed . The installation of an aerobic selector, consisting of three cascades, pr ior to the aeration tank of the second stage, where the return sludge and a ll the influents flow together, has been effective in improving the SVI to values below 150 ml/g. The design procedure was carried out in accordance w ith Prendl's work, with a simple calculation method based on findings deriv ed from aerobic treatment of sugar mill wastewater.