Screening of denitrifying polyphosphate-accumulating organisms and their biological characteristics

To study the biological characteristics of denitrifying phosphate-accumulating organisms (DNPAOs), four effective DNPAOs were identified in an anaerobic/anoxic SBR reactor with steady operation. Candidate organisms were screened by a phosphate uptake experiment, where nitrates were denitrified to gas and through inspection of metachromatic and Polyphydroxybutyrate (PHB) granules. The DNPAOs were Pseudomonas sp. H16, H19, H24 and Enterobacter sp. Xg. Two important factors, temperature and pH value, were studied to evaluate their effect on the growth and phosphorus removal ratios of H16, H19, H24 and Xg. Results show that the optimal temperature for the four DNPAO's growth and phosphorus removal is about 35°C and 25°C respectively. In ideal temperature conditions, the best pH values for H16, H19 and H24 growth and phosphorus removal range from 6.0-8.0; for Xg, the best pH range is between 7.0-9.0.Phosphorus removal for all four strains are optimal in a mildly alkali condition. Growth curves for these strains were also determined.