Polyphosphate accumulation by bacteria isolated from activated sludge

Biological phosphorus removal is an acknowledged phenomenon applied to redu ce phosphorus concentrations in wastewaters. Under aerobic conditions some heterotrophic organisms store polyphosphate intracellularly which serves as a phosphorus and energy source during periods of phosphorus starvation. Th e objective of this study was to investigate polyphosphate accumulation by all bacteria isolated from the aerobic zone of a nutrient removal plant. Po lyphosphate organisms were isolated on casitone glycerol yeast agar. Proced ures for phosphate uptake studies included exposure of each monoculture to anaerobic environments for 2 h followed by aeration for 5 h. Extracellular orthophosphate concentrations were determined after aeration using a Merck SQ118 spectrophotometer. Identification was conducted using various biochem ical tests, API 20E and 20NE. Acinetobacter calcoaceticus var. lwoffi, Aero monas hydrophila, gram-positives and Pseudomonas spp. were among the predom inant phosphate removers. Neisser staining confirmed that the organisms had stored polyphosphate intracellularly. Findings confirm that Acinetobacter calcoaceticus var, lwoffi is the predominant micro-organisms involved in en hanced phosphorus uptake.