Influence of pH shift on the community enriched in phosphate-accumulating microorganisms in a sequential-periodic action bioreactor

In a sequentially periodic bioreactor, changes in the structure and properties of a community enriched with phosphate-accumulating microorganisms (PAO) after a shift in pH to more acidic values (pH 6.7–7.1) were traced. The proportion of Candidatus Accumulibacter decreased from 43.6 to 13.9%, while the number of potential FAOs belonging to Dechloromonas and Thauera increased. At the same time, the share of the total amount of FAO changed slightly and amounted to 40–43%. The share of the main competitors of FAO ‒ glycogen-accumulating microorganisms (GAM) during the experiment remained insignificant: Competibacter 16S rRNA gene fragments before and after pH changes amounted to 2‒4%. A decrease in pH led to a drop in the amount of phosphates released in the anaerobic phase, but the amount of phosphorus in the biomass and its removal remained high ‒ 15–17 and 92–94%, respectively.