High-temperature EBPR process: The performance, analysis of PAOs and GAOs and the fine-scale population study of Candidatus “Accumulibacter phosphatis”

The applicability of the enhanced biological phosphorus removal (EBPR) process for the removal of phosphorus in warm climates is uncertain due to frequent reports of EBPR deterioration at temperature higher than 25 °C. Nevertheless, a recent report on a stable and efficient EBPR process at 28 °C has inspired the present study to examine the performance of EBPR at 24 °C–32 °C, as well as the PAOs and GAOs involved, in greater detail. Two sequencing batch reactors (SBRs) were operated for EBPR in parallel at different temperatures, i.e., SBR-1 at 28 °C and SBR-2 first at 24 °C and subsequently at 32 °C. Both SBRs exhibited high phosphorus removal efficiencies at all three temperatures and produced effluents with phosphorus concentrations less than 1.0 mg/L during the steady state of reactor operation. Real-time quantitative polymerase chain reaction (qPCR) revealed Accumulibacter-PAOs comprised 64% of the total bacterial population at 24 °C, 43% at 28 °C and 19% at 32 °C. Based on fluorescent in situ hybridisation (FISH), the abundance of Competibacter-GAOs at both 24 °C and 28 °C was rather low (