Development of the microbial community of a full scale biological nutrient removal activated sludge plant during start-up

The bacterial populations capable of accumulating polyphosphate in pure culture were followed during the first 10 months of operation of a full scale biological nutrient removal plant with a modified U.C.T. configuration. Special emphasis was placed on the Acinetobacter isolates obtained. Results showed that of these, most could be identified as A. johnsonii (genospecies 7) although other genospecies including 9 and 12 were also found in smaller numbers. A large number of these could not be identified with the Biology system. Several other Gram positive and Gram negative bacterial genera capable of removing polyphosphate were also isolated from the biomass. The filamentous bacterial populations seen in the mixed liquor and foam were monitored regularly over this period, and after early changes, Microthrix parvicella and Eikelboom Types 0092 and 0041/0675 gradually assumed dominance in the mixed liquor, while Nocardia amarae-like organisms and Type 0092 together with M. parvicella were in the foam.