Insights into Synergistic Metabolism Mechanisms of Carbon, Nitrogen and Phosphorus in Tetrasphaera-dominated Partial Denitrifying Phosphorus Removal and Anammox (PDPRA) process

The partial denitrifying phosphorus removal coupled with anammox (PDPRA) technology holds great promise for the simultaneous removal of carbon, nitrogen, and phosphorus. However, its widespread application is hindered by the instability of nitrite accumulation and the strong dependence on volatile fatty acids (VFAs) of traditional denitrifying polyphosphate accumulating organisms (DPAOs). This study first proposes coupling partial denitrifying phosphorus removal, driven by Tetrasphaera, a novel fermentative DPAO, with anammox for efficiently treating wastewater rich in complex organic matter (e.g., amino acids and proteins). A comprehensive investigation was conducted on the synergistic metabolic mechanisms between DPAOs and anammox bacteria (AnAOB). Under a low carbon to nitrogen (C/N) ratio of 3.1 ± 0.1, Tetrasphaera utilized intracellular amino acids, particularly proline, to drive the stable and efficient nitrite accumulation, leading to a contribution of 82.64% to total nitrogen removal through anammox. This PDPRA system ultimately achieved remarkable removal efficiency of chemical oxygen demand (COD, 84.8 ± 0.8%), total inorganic nitrogen (TIN, 92.3 ± 0.9%) and orthophosphate (PO₄^3--P, 92.0 ± 1.5%). Microbial community analysis and metagenomic sequencing revealed the high abundance of Tetrasphaera and Candidatus Brocadia, with their high contribution to key functional genes (narGHI, napAB, ppk1, ppk2, hzs, hdh) confirming the co-existence and co-prosperity metabolic relationship between DPAO and AnAOB. Additionally, an even spatial distribution of Tetrasphaera and AnAOB within the biofilm was developed, further ensuring the stable and efficient removal performance. The findings of this study contribute to the broader application of the PDPRA process and provide a new approach for treating wastewater containing complex organic matter.