FORMATION AND FINAL COMPOSITION OF BACTERIAL FLORA OF A DAIRY WASTE ACTIVATED SLUDGE

A comparison of the bacterial flora of a dairy waste activated sludge developing from the initial to the optimal stage in an oxidation ditch and in a laboratory apparatus, showed a close similarity between both systems, so that the latter may be used for representative experiments. Adaptation of the bacterial flora to the supplied waste was found to be a slow process. The composition of the flora altered with time until ultimately it consisted predominantly of coryneform (Arthrobacter-like) bacteria. Next to these, considerable amounts of Achromobacteraceae were found. Pseudomonadaceae, initially present in large numbers, decreased to the least important of the 3 major groups of bacteria. The alteration of the bacterial groups coincided with an alteration of the physiological characteristics of the total activated sludge flora. In the final stage two-thirds of the isolated bacteria gave a neutral reaction on Hugh and Leifson media and more than half were nonproteolytic. This is in agreement with the predominant position held by the group of coryneform-particularly Arthrobacter-like-bacteria. The brown colour of dairy waste activated sludge may be attributed to Flavobacteria. © 1968.