To investigate the bioelectrochemical enhanced anaerobic ammonia oxidation (anammox) nitrogen removal process, a bioelectrochemical system with coupled anammox cathode was constructed using a dual-chamber microbial electrolysis cell (MEC). Specifically, a dark incubation batch experiment was conducted at 30 ℃ with different influent total nitrogen concentrations under an applied voltage of 0.2 V, and the enhanced denitrification mechanism was investigated by combining various characterization methods such as cyclic voltammetry, electrochemical impedance spectroscopy and high-throughput sequencing methods. The results showed that the total nitrogen removal rates of 96.9%±0.3%, 97.3%±0.4% and 99.0%±0.3% were obtained when the initial total nitrogen concentration was 200, 300 and 400 mg/L, respectively. In addition, the cathode electrode biofilm showed good electrochemical activity. High-throughput sequencing results showed that the applied voltage enriched other denitrifying functional groups, including Denitratisoma, Limnobacter, and ammonia oxidizing bacteria SM1A02 and Anaerolineaceae, Nitrosomonas europaea and Nitrospira, besides the anammox bacteria. These electrochemically active microorganisms comprised of ammonium oxidizing exoelectrogens (AOE) and denitrifying electrotrophs (DNE). Together with anammox bacteria Candidatus Brocadia, they constituted the microbial community structure of denitrification system. Enhanced direct interspecies electron transfer between AOE and DNE was the fundamental reason for the further improvement of the total nitrogen removal rate of the system.
Denitrification ; Wastewater ; Anaerobic Ammonia Oxidation ; Nitrogen ; Oxidation-Reduction ; Bioreactors/microbiology* ; Ammonium Compounds ; Bacteria/genetics* ; Microbiota ; Sewage

To study the effect of preservation temperature on the characteristics of anaerobic ammonium oxidation (Anammox) granules and optimize the preservation temperature of Anammox granules, the Anammox granules were cultivated in an upflow anaerobic sludge bed reactor through adjusting the hydraulic retention times, and the inorganic carbon with KHCO3/NaHCO3 was alternately supplied. Subsequently, the enriched Anammox granules were preserved at -40, 4 and 35 °C, and ambient temperature of (27 ± 4) °C. NaHCO3 can be used as the inorganic carbon for the growth of anaerobic ammonium oxidizing bacterium (AnAOB). The best preservation temperature was 4 °C for maintaining Anammox biomass, Anammox activity, settleability, and the integrity of the Anammox granule and AnAOB cell structure. During the preservation period, the first-order exponential decay model can simulate the decay of Anammox biomass and activity, and the decay coefficients (bAN) of Anammox biomass and activity had positive correlation with the degree of AnAOB cell lysis. Meanwhile, the rate of Anammox biomass decay was larger than that of Anammox activity. The ratio of protein to polysaccharide in extracellular polymeric substances and heme c cannot effectively indicate the changes of Anammox granules settleability and activity, respectively, and the bioactivity has a negative association with the degree of AnAOB cell lysis.
Ammonia ; chemistry ; Anaerobiosis ; Bacteria, Anaerobic ; Biomass ; Bioreactors ; Carbon ; Models, Theoretical ; Oxidation-Reduction ; Sewage ; microbiology ; Temperature

Anaerobic ammonia oxidation (Anammox) is one of the important discoveries in the field of environmental microbiology, and it plays an indispensible role in the nitrogen removal from wastewaters and the biogeochemical nitrogen cycle. Through review research progress in anaerobic ammonia oxidation, an Anammox special issue is published so as to find problems, explore applications and outlook developments. The special issue consists of reviews and original papers, mainly involving in the following aspects: i) enrichment of Anaerobic ammonia oxidation bacteria (AnAOB); ii) community analysis of AnAOB; iii) preservation of granular AnAOB sludge; iv) effect of organic matter on Anammox; v) application of Anammox process, etc.
Ammonia ; chemistry ; Bacteria, Anaerobic ; metabolism ; Environmental Microbiology ; Nitrogen ; chemistry ; Nitrogen Cycle ; Oxidation-Reduction ; Sewage ; microbiology ; Waste Disposal, Fluid ; Waste Water ; chemistry

Start-up and process control of a pilot-scale anaerobic ammonium-oxidizing (Anammox) bioreactor were studied at ambient temperature. Inoculated with a mixture of nitrification-denitrification sludge, nitritation sludge, anaerobic floc sludge and anaerobic granular sludge, the pilot-scale Anammox bioreactor was successfully started up within 255 days at 5 degrees C-27 degrees C. The nitrogen removal rate reached 1.30 kg/(m3 x d). Three facets were taken into account to facilitate the process initiation. First, in terms of alkalization in Anammox, influent pH was kept at about 6.8. Besides, nitrite concentration was kept as low as 13-36 mg/L. Finally, 2% (volumetric ratio) of Anammox sludge from lab-scale bioreactors was supplemented to the pilot-scale one.
Ammonia ; chemistry ; metabolism ; Bacteria, Anaerobic ; metabolism ; Bioreactors ; microbiology ; Nitrites ; analysis ; Nitrogen ; metabolism ; Oxidation-Reduction ; Sewage ; microbiology ; Waste Disposal, Fluid ; instrumentation ; methods