[Improved on Nitrogen Removal of Anaerobic Ammonia Oxidation by Coupling Element Sulfur-based Autotrophic Short-cut Denitrification].

In order to enhance the removal of NO3--N in the ANAMMOX process, an element sulfur-based autotrophic short-cut denitrification (short-cut S0-SADN) was introduced by adding elemental sulfur to an ANAMMOX continuous flow reactor. The effects of different influent NH4+-N/NO2--N ratios on the nitrogen conversion and NO2--N competitive characteristics in the coupled system were investigated at (33±2)℃ and a pH of 7.8-8.2. The results showed that under different influent NH4+-N/NO2--N ratios (1:1.3, 1:1.5, 1:1, and 1:1.1), the average total nitrogen (TN) removal efficiency of the coupled system reached 96.78%, 97.21%, 94.68%, and 97.72%, respectively, which were much higher than the highest TN removal efficiency of the ANAMMOX theory (89%). Among them, the stable operation of deep nitrogen removal of the short-cut S0-SADN coupled with ANAMMOX was successfully achieved with an influent NH4+-N/NO2--N ratio of 1:1 or 1:1.1. Under the optimal influent NH4+-N/NO2--N ratio of 1:1.1, the concentrations of influent NH4+-N and NO2--N were 240 mg·L-1 and 265 mg·L-1, respectively, the TN removal rate reached 1.50 kg·(m3·d)-1, and the TN removal efficiency of ANAMMOX and S0-SADN pathways were stable at (95.68±1.22)% and (2.04±0.77)%, respectively. During the entire operational process, ANAMMOX always occupied an absolute advantage in the competition of substrate NO2--N, and the activity of ANAMMOX bacteria (NH4+-N/VSS) was stable at (0.166±0.008)kg·(kg·d)-1.

[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.

[Granular Characteristics of Anaerobic Ammonia Oxidation Sludge During the Recovery Process].

Operation instability has become one of the factors restricting the application of the anaerobic ammonia oxidation (ANAMMOX) process. Under the condition that the substrate is not suppressed, the effects of the substrate concentration on the granulation and activity of ANAMMOX granular sludge in the recovery process were studied by restoring the activity of ANAMMOX sludge, which was derived from early-stage operation instability of the continuous stirred tank reactor (CSTR). The results show that the activity of ANAMMOX sludge was recovered and the denitrification capacity increased significantly after 126 days of operation. When the NH4+-N and NO2--N concentrations were 450 mg·L-1 and 560 mg·L-1, respectively, the nitrogen removal was achieved in both the high-and low-substrate concentration reactors and the maximum NRR was 16.97 kg·(m3·d)-1 and 14.43 kg·(m3·d)-1, respectively. With the improvement of the nitrogen removal capacity of the reactor (the granular diameter of the sludge is increased), the extracellular polymeric substance (EPS) content increased in both reactors from 34.45 to 77.52 and to 94.18 mg·g-1, respectively, and the PN/PS increased from 1.89 to 6.25 and 6.84, respectively. To a certain extent, the increase of PN/PS is conducive to the granulation of ANAMMOX sludge, but a too large PN/PS would lead to the instability of granular sludge and sludge loss.