Advanced nitrogen and phosphorus removal from municipal wastewater via simultaneous enhanced biological phosphorus removal and semi-nitritation (EBPR-SN) combined with anammox.

In this study, a novel laboratory-scale synchronous enhanced biological phosphorus removal and semi-nitritation (termed as EBPR-SN) combined with anammox process was put forward for achieving nutrient elimination from municipal wastewater at 27 ℃. This process consisted of two 10 L sequencing batch reactors (SBRs), i.e. EBPR-SN SBR followed by Anammox SBR. The EBPR-SN SBR was operated for 400 days with five periods and the Anammox SBR was operated starting on period IV. Eventually, for treating municipal wastewater containing low chemical oxygen demand/nitrogen (COD/N) of 3.2 (mg/mg), the EBPR-SN plus Anammox system performed advanced total inorganic nitrogen (TIN) and P removal, with TIN and P removal efficiencies of 81.4% and 94.3%, respectively. Further analysis suggested that the contributions of simultaneous partial nitrification denitrification, denitrification, and anammox to TIN removal were 15.0%, 45.0%, and 40.0%, respectively. The enriched phosphorus-accumulating organisms (PAOs) in the EBPR-SN SBR facilitated P removal. Besides, the EBPR-SN SBR achieved P removal and provided stable anammox substrates, suggesting a short sludge retention time (SRT 12 d) could achieve synergy between ammonia-oxidizing bacteria and PAOs. These results provided an alternative process for treating municipal wastewater with limited organics.

Nitrogen removal from low COD/N interflow using a hybrid activated sludge membrane-aerated biofilm reactor (H-MABR).

A hybrid activated sludge membrane-aerated biofilm reactor based on a two-stage simultaneous nitrification-denitrification (SND) process was built, and its utility for treating interflow with low chemical oxygen demand (COD)/total nitrogen (TN) (COD/N) was explored. The operating performance, functional microbial communities, and functional genes for nitrogen metabolism were evaluated at low COD/N (4-1.3). The reactor could achieve stable operation at COD/N = 4-1.5, and the removal efficiency of COD, TN, and ammonia nitrogen was stable at 90.30 ± 2.36 %, 85.69 ± 2.22 %, and 89.52 ± 6.06 %, respectively. The SND rates were 70.89 % and 50.75 % when influent COD/N was 2.0 and 1.7, respectively, indicating that SND makes an important contribution to nitrogen removal under these two COD/N conditions. Microbial analysis revealed that the sampling sites with a high abundance of denitrification genes in the outer ring experienced aerobic conditions, inferring that aerobic denitrification also plays an important role in denitrification.

Effect of increasing salinity and low C/N ratio on the performance and microbial community of a sequencing batch reactor.

The purpose of this study was to investigate the effects of increasing salinity on the performance and microbial community structure in a sequencing batch reactor (SBR) treating low C/N ratio wastewater. The SBR was subjected to a gradual increased salinity from 0 wt% to3.0 wt% under low Chemical Oxygen Demand (COD)/N ratio, operating for 80 days. The study results indicated that high salinity decreased the removal efficiency of ammonium (NH4+-N) from 77.09% (1.0 wt%) to 45.7% (3.0wt%). The organic matter removal are not significantly affected by the high salinity. Non-metric Multi-Dimensional Scaling (NMDS) analysis showed that the gradual increased salinity altered the overall bacterial community structure, and low salinity (1wt%) promoted the bacterial diversity, while high salinity (2 and 3 wt%) significantly decreased the bacterial diversity in low C/N ratio activated sludge system. Further analysis revealed that two genera related to nitrification process (unclassified-Nitrosomonadales and g-Nitrospira) were inhibited, while a genus related to organic removal (Piscicoccus) and three genera related to denitrification (Rodobacteraceae, Denitromonas and Hyphomicrobium) increased significantly at a salinity of 3 wt%. This study provides insights of shifts in the bacteria community under the stress of high salinity in low C/N ratio of activated sludge systems.

Simultaneous nitrification and denitrification in the bio-cathode of a multi-anode microbial fuel cell.

A multi-anode microbial fuel cell (MA-MFC) was developed to investigate simultaneous nitrification and denitrification (SND) in the bio-cathode. As the chemical oxygen demand to nitrogen (COD/N) ratio of the cathode was increased from 0 to 4.5, the electricity-producing quantity ranged between 498 and 543 C and the attained total nitrogen (TN) removal rate reached 12.07 g TN·m-3·d-1, resulting in a TN removal efficiency of 78.8% under the target COD/N ratio of 3.5. The removal of pollutants in series and parallel, open-circuit and closed-circuit were compared, respectively. The removal rates of TN, NH4+-N, and cathode and anode COD were all higher in the parallel connection configuration than in the series configuration. In parallel connection, the TN removal rate reached 14.4 g TN·m-3·d-1, which was 1.9 times that in series connection. Compared with the open-circuit system, the removal rate of TN in the closed-circuit system was improved by 17.8%, which could be ascribed to electrochemical denitrification. The results of high-throughput sequencing confirmed and clarified the presence of autotrophic denitrification and heterotrophic denitrification, including aerobic denitrification, when the MA-MFC had been operated for 18 months.

[Long-term Performance and Bacterial Community Composition Analysis of AGS-SBR Treating the Low COD/N Sewage at Low DO Concentration Condition].

This study utilized the sequencing batch activated sludge reactor (SBR) inoculated aerobic granular sludge (AGS) to treat the low COD/N ratio (<4.0) domestic wastewater under low DO (0.5-1.0 mg·L-1) concentration condition. Long-term performance of simultaneous nitrogen and phosphorus removal and bacterial community composition of AGS-SBR were studied. The results showed that the AGS-SBR system had good and stable decontamination abilities in its 180-day operation. The average removal rates of COD, NH4+-N, TN and TP were 87.17%, 95.21%, 77.05%, and 91.11%, respectively. At the same time, the AGS showed good settling performance, and always kept its integrated and compact structure. No obvious granular sludge disintegration phenomenon occurred in 180 days. Meanwhile, by using Illumina 16S rRNA gene MiSeq sequencing, we investigated the bacterial abundance in AGS-SBR reactor. Proteobacteria, Firmicutes, Chlorobi, Chloroflex, and Bacteroidetes were the dominant microbial communities in the simultaneous nitrogen and phosphorus removal reactor. Denitratisoma, Planctomycetaceae, Thauera, Comamonas, Nitrosomonas and Nitrospira were suggested to be the primary organisms responsible for the nitrogen removal. Clostridium and Anaerolinea were the main bacterial communities of phosphorus removal.