Population shifts in activated sludge from sewage treatment plants of the chemical industry: A numerical cluster analysis

Summary The numerical taxonomy of the bacterial flora in activated sludge from two sewage treatment plants of the chemical industry is described. The predominant taxa; Alcaligenes, Pseudomonas and Zoogloea could be devided into a total of 14 subclusters. A significant disturbance of the biocoenosis was manifested in a substantial drop in the plant efficiency and in defined population shifts. The bacterial groups which increase, as the process performance improves are indicated and their technological significance is discussed.