EBPR process dynamics under variable conditions: interaction between PAOs and the microbial community

The performance of enhanced biological phosphorus removal (EBPR) is influenced by various process conditions, such as the type of carbon source, temperature, COD:P ratio or pH-value. The activity of polyphosphate accumulating organisms (PAOs) and the composition of biocoenosis are strongly influenced by these process conditions. Nevertheless, critical knowledge gaps remain regarding the relevance of microbial diversity and the correlations between PAO/GAO community composition and EBPR process dynamics under different operational conditions. This study demonstrates that Dechloromonas plays a crucial role in the EBPR process and that the type of carbon source has a more sensitive influence on EBPR dynamics than the COD:P ratio, temperature or pH. Using both a microfluidic model biofilm system (MMBS) and a sequencing batch reactor (SBR) system, we found that the consumption of glucose resulted in maximal PAO activity, whereas EBPR performance was limited when using glycerol, ethanol and amino acids. In both systems, Dechloromonas was the dominant PAO, while in MMBS Zoogloea and in SBR Competibacter/Contendobacter were the dominant GAOs. Tessaracoccus (PAO) and Micropruina (GAO) were relevant in the fermentation of glucose and glycerol. No significant effect on EBPR performance was observed between 12 and 20 °C, and PAO activity peaked at pH 7.5. Our findings highlight that PAO-GAO competition is overestimated. We anticipate that our study provides a deeper understanding of the dynamics in the biocoenosis and emphasizes the relevance of biodiversity in EBPR systems, which would help guide relevant applications.