Research in the area of bacteriological studies of biogical nutrient removal (BNR) systems has emphasized the role of Acinetobacter spp. in phosphorus removal. The present study was undertaken to enumerate, isolate and identify bacterial populations from a BNR/activated sludge system. The most probable numbers (MPN) of volatile fatty acid (VFA) utilizers and denitrifiers were determined. Bacterial populations were isolated from the MPN tubes. Pure cultures of Gram-negative bacteria were identified. Acinetobacter spp. were not the dominant group of bacteria recovered from the system. Bacteria belonging to Aeromonas/Vibrio, coliforms, Pseudomonas and Acinetobacter groups were recovered both on VFA media and denitrification medium, indicating an overlap in their role. In the system studied, both phosphorus and nitrogen removal was carried out by more than one group of bacteria.
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