NON-FILAMENTOUS ACTIVATED-SLUDGE BULKING IN A LABORATORY-SCALE SYSTEM

The paper describes the appearance of non-filamentous bulking in a lab -scale activated sludge plant with nitrification-denitrification and r eaeration of return sludge. The inlet part of the denitrification zone was operated as an anoxic selector. Although filamentous microorganis ms regularly occurred, the sludge settled properly. Deterioration of S VIs was observed after increasing the oleic acid concentration in synt hetic wastewater. The bulking period was related to the abundant growt h of viscous zoogloeal colonies. The intensive foam production resulte d from the excessive appearance of exocellular polymers. A structure o f short intertwined fingered projections formed the zoogloeal flocs. A fter decreasing the oleic acid proportion in the synthetic wastewater to the original level the zoogloeal flocs gradually changed to the wel l-settling sludge in 3 weeks.