Bacteriological studies of excess activated sludge subjected to aerobic mineralization.

Quantitative and qualitative changes in the composition of bacterial microflora occur in the course of mineralization of excess activated sludge formed during the purification of crude oil refining wastewaters were studied. The excess activated sludge was dominated by Gram-negative bacteria belonging to the genera Pseudomonas III and IV. Mineralization of the excess sludge in both stationary and semicontinuous systems was accompanied by quantitative changes in the composition of the individual groups of Gram-negative bacteria. The frequency of Pseudomonas was reduced in favour of the Enterobacteriaceae, Achromobacter and Alcaligenes.