[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.

[Influence of Substrate Exposure Level on ANAMMOX Microbial Activity and Biomass].

Substrate exposure levels are vital for the growth and metabolism of ANAMMOX microorganisms, and their effects on growth characteristics of ANAMMOX sludge during the enrichment process have been rarely reported. Using two continuous flow stirred reactors and the process of a gradually developing nitrogen load, the changes in biomass and activity, as well as nitrogen removal efficiency of the reactors were investigated under high substrate exposure level culture mode (R1:effluent NH4+-N and NO2--N concentrations were 40-60 mg·L-1) and low substrate exposure level culture mode (R2:effluent NH4+-N and NO2--N concentrations were 0-20 mg·L-1). The results showed that the high substrate exposure level culture mode was more beneficial to the improvement of nitrogen removal performance of the ANAMMOX reactor. For comparison, the NLR (nitrogen load rate), which was 0.69 kg·(m3·d)-1, and the NRR (nitrogen remove rate), which was up to 0.41 kg·(m3·d)-1, was obtained in the high substrate exposure culture mode. These values were twice as high as those obtained in the low substrate exposure culture mode. Under the culture mode with high substrate exposure level, the sludge concentration (in VSS) and the total gene copy numbers of ANAMMOX reached 1805 mg·L-1 and 4.81×1012 copies, respectively, which was conducive to the rapid enrichment of ANAMMOX microorganisms. In the low substrate exposure level culture mode, ANAMMOX sludge was more active,in N/VSS, 0.27 g·(g·d)-1, which was conducive to the cultivation of ANAMMOX sludge with higher biological activity.

[Treatment of Old Landfill Leachate via a Denitrification-Partial Nitritation-ANAMMOX Process].

To research the performance of removing nitrogen and organics from old landfill leachate via denitrification-partial nitritation-ANAMMOX (DN-PN-ANAMMOX) process, an integrated reactor seeded with mature ANAMMOX sludge and nitritation sludge connected to a denitrification (DN) reactor was studied. The result showed that before the pre-denitrification reactor was connected, the PN-ANAMMOX reactor achieved a nitrogen removal rate (NRR) of 1.88 kg·(m3·d)-1 and a nitrogen removal efficiency (NRE) of 90.3% when the concentration of influent ammonia nitrogen and COD were 600 mg·L-1 and 483 mg·L-1, respectively. The NRR of the PN-ANAMMOX process dropped to 1.50 kg·(m3·d)-1 when the concentration of influent COD>483 mg·L-1, which corresponds to C/N>0.8. To relieve the influence of organic matter on ANAMMOX, a DN reactor was put in front of the PN-ANAMMOX reactor. The DN-PN-ANAMMOX process achieved an NRR and NRE of 1.37 kg·(m3·d)-1 and 98.6%, respectively, under the conditions of influent ammonia nitrogen and COD concentrations of 1100 mg·L-1 and 1150 mg·L-1, respectively. The NRR of ANAMMOX reached 15.6 kg·(m3·d)-1. The whole system realized a highly efficient and deep removal of nitrogen without any additional carbon source. When treating old landfill leachate, most of the biodegradable organics can be removed by the system.