[Microbial Community Analysis of Different DN and PN-ANAMMOX Coupling Modes for Mature Landfill Leachate Treatment]

To promote the application of ANAMMOX process in landfill leachate treatment, a pilot reactor based on the ANAMMOX process was established at a landfill site. In this paper, we aim to further analyze the influence of different coupling modes of denitrification (DN) and partial nitrification and ANAMMOX (PN-ANAMMOX) on the diversity of microbial community. The DN+(PN-ANAMMOX) process could effectively treat the mature leachate. However, with an increase in organic matter in the influent, the oxygen demand of PN zone increased, and the enrichment of Nitrosomonadaceae in the PN zone was limited. The lack of substrate supply for ANAMMOX zone further limited the enrichment of Brocadiaceae as well; thus, the total nitrogen removal rate (TNRR) remained at 0.44 kg ·(m³ ·d)^-1. In the DN-(PN-ANAMMOX) process, Saprospiraceae with denitrifying ability was enriched in the DN zone, and the organic matter was gradually degraded and removed; thus, a good low-carbon environment was provided for the subsequent PN-ANAMMOX process. Nitrosomonadaceae and Brocadiaceae were enriched in the functional zones, and the TNRR and total nitrogen removal efficiency (TNRE) of the DN-(PN-ANAMMOX) were further elevated to 0.55 kg ·(m³ ·d)^-1 and 94.65%, respectively. Moreover, the direct treatment of mature leachate with 2233 mg ·L^-1 NH₄⁺-N and 2712 mg ·L^-1 COD was finally realized. In addition, Candidatus Kuenenia was better adapted to leachate and high substrate concentration wastewater, and it became the dominant genus in the ANAMMOX zone.