Population dynamics of “Candidatus Accumulibacter phosphatis” under the modes of complete nitrification and partial nitrification (nitritation) in domestic wastewater treatment system

Abstract In order to understand the enhanced biological phosphorus removal in a continuous-flow domestic wastewater treatment system, population dynamics of “ Candidatus Accumulibacter phosphatis” using polyphosphate kinase ( ppk 1) gene as genetic marker was investigated under the modes of complete nitrification and partial nitrification (nitritation). Nitritation was achieved at hydraulic retention time (HRT) of 6.49 h and dissolved oxygen (DO) of 0.5 mg O 2 /L. Denitrifying phosphate removal via nitrite pathway caused low PHAs consumption. Regardless of change of nitrifying modes, phosphorus removal always maintained at a high level of about 100%. Abundance of total Accumulibacter increased along with rising of carbon to nitrogen ratios (C/N). Under good performance of complete nitrification and nitritation, IIC and IID clade affiliated with type II (including clades II A-I) of Accumulibacter lineage was dominant (70%–80%), respectively. Clade IID exhibited high tolerance to starving, oxygen-limiting and high nitrite accumulation, and thus became dominant clade under insufficient carbon sources, low DO and nitritation mode. Clade IIC had a positive correlation with C/N ratios, and IIF had a positive correlation with temperature (p