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This study provides a feasible scheme for the treatment of municipal sewage through simultaneous partial nitritation, anammox, and denitrification (SNAD) process, which was realized in a single-stage biofilter reactor (BFR). First, the BFR was started up to enrich the anaerobic ammonium-oxidizing bacteria (AnAOB) in the upper part of the reactor through the operation mode of the top influent and bottom effluent. Then, the BFR was inoculated with activated sludge and aerated continuously at the bottom to realize the coupling of SNAD, which was accompanied by a two-point influent from the bottom and top effluent. Results indicated that the high removal efficiency of NH4+-N (93.40%), total nitrogen (TN, 89.95%), and soluble chemical oxygen demand (SCOD, 92.68%) were achieved with an air–water ratio of 4.29 and hydraulic retention time (HRT) of 6 h. During the SNAD steady phase for the treatment of simulated municipal sewage with a soluble chemical organic demand to nitrogen (C/N) ratio of 2.31, low concentrations of NH4+-N (4.13 mg/L), TN (6.44 mg/L), and SCOD (11.29 mg/L) were attained in the effluent. High-throughput sequencing analysis indicated that the relative abundance of Nitrosomonas, Candidatus Brocadia, and Denitratisoma were 0.77%, 0.43%, and 4.07% in the biofilm at the 0–12.5 cm zone, respectively, suggesting successful implementation of the SNAD process.

Two sets of hybrid constructed wetlands (HCWs) with the first-stage aeration were used to treat actual domestic sewage in this paper, where the effects of three important factors of aeration mode, hydraulic loading rates (HLR), and aeration volume on the removal of pollutants in both HCWs were studied in contrasts. In addition, the pollutant removal efficiency, the contribution of plants, and the characteristics of biofilm in both HCWs were explored. The results of 250-day experiment showed that the TN removal capacity of HCW combining vertical flow CW with horizontal flow CW (VF-HF) was better than HCW’s converse combination (HF-VF) in treatingsewage, while the removal efficiency of COD and NH4+-N were similar, and the concentrations of TN and COD in the effluent of VF-HF could successfully meet the National discharge requirements. Compared with the continuous aeration, the intermittent aeration only had a little effect on the removal of COD and NH4+-N, but could improve TN removal performance in both HCWs. Meanwhile, increasing the aeration volume was beneficial to remove NH4+-N but not TN in HCWs. In addition, although the pollutant removal performances in both HCWs were impacted, the removal capacity of TN in VF-HF was only affected a little, when HLR was increased by 50%. The contribution of plants’ uptake accounted for about 10% to nitrogen removal and 20% to phosphorus removal in both HCWs. The biomass at the filler surface near the plant rhizosphere was greater than that in the non-rhizosphere zones, and the impact of plant rhizosphere on the nitrification activity of biofilm was significantly greater than that on denitrification activity in both HCWs.

The high-rate nitrogen removal in a continuous biofilter anammox reactor (CBAR) was investigated to treat low-concentration nitrogen wastewater. Shortening hydraulic retention time (HRT) gradually could restart CBAR and accumulate anammox bacteria effectively in the reactor, where the carmine anammox granular sludge and biofilm were coexisted well. It spent 21 days to restart CBAR completely after it had been idle for 116 days. Meanwhile, the total nitrogen removal rate remained stable at 86.42% accompanied with a total biomass concentration of 26.02 g-SS/L in 0 ~ 20 cm zone under nitrogen loading rate of 4.25 ± 0.10 kg-N/(m3·day), HRT of 20 min and 25 ℃. In addition, the specific anammox activity of biomass exceeded 0.28 g-N/(g-VSS·day) in 0 ~ 20 cm zone, which was related with a high relative abundance of Candidatus Brocadia (>30%) in the same zone. Thus, it is a feasible approach to adopt CBAR to treat low-concentration nitrogen wastewater efficiently.