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The application of ANAMMOX technology is constrained by sluggish growth and difficulty in enriching ANAMMOX bacteria. Long-term starvation of functioning bacteria due to limited substrate supply makes the steady operation of ANAMMOX reactors more difficult. Re-examining the start-up and recovery performance of the ANAMMOX reactor and identifying its resistance mechanism are important from the standpoint of long-term starvation. By inoculating nitrifying and denitrifying sludge under various operating circumstances, the ANAMMOX reactors were successfully started. Under various start-up procedures, the tolerance mechanism and recovery performance were examined. The outcomes demonstrated that the denitrifying sludge-inoculated reactor operated steadily with a high substrate concentration and low flow rate. After 85 days of operation, the removal efficiencies of NH 4 + -N, and total nitrogen reached 98.7%, 99.3%, and 89.3%, respectively. After 144 days of starvation and 30 days of recovery, the better nitrogen removal performance was achieved at a low substrate concentration and high flow rate, and the removal efficiencies were 99.8% （NH 2 - -N）, and 93.6% （total nitrogen）. During the starvation, extracellular polymeric substances wrapped the ANAMMOX bacteria and kept them intact to resist long-term starvation stress. The expression of 4 + -N）, 99.8% （NO 2 - -N）, and 93.6% （total nitrogen）. During the starvation, extracellular polymeric substances wrapped the ANAMMOX bacteria and kept them intact to resist long-term starvation stress. The expression of nirS , hzsA , and hdh genes ensured the synthesis of nitrite/nitric oxide oxidoreductase, hydrazine synthase, and hydrazine dehydrogenase to maintain ANAMMOX activity. There was no significant difference in the relative abundance of ANAMMOX bacteria before and after starvation recovery. Candidatus Kuenenia had better anti-hunger ability, and the relative abundance increased by more than 86% after 30 days of recovery, confirming its tolerance to long-term starvation.

Hydroxylamine (NH 2 OH), one of the most important intermediates of anammox was employed to test the recovery performance because of its stimulation to anammox bacteria. Batch test indicated simultaneous addition of 1.83 ~ 9.17 mg N /L NH 2 OH relieved Cr(VI) inhibition because of extracellular reduction to Cr(III). The recovery efficiency (RE) was over 166%, with the effluent Cr(VI) and Cr(III) below 0.25 and 0.12 mg/L, respectively. Anammox activity after Cr(VI) inhibition was effectively recovered by 8 mg N/L NH 2 OH with RE at 218%. The long-term operation showed 1 ~ 2 mg N/L NH 2 OH accelerated the recover speed of nitrogen removal rate with 2.84 folds, as well as improving NH 4 + conversion ratio and reducing NO 3 - production. After 55 days recovery, extracellular polymeric substance concentration, anammox activity and heme content recovered better with NH 2 OH addition. This study will provide the theoretical basis for rapid recovery of anammox activity by NH 2 OH when suffering Cr(VI) inhibition., (Copyright © 2021 Elsevier Ltd. All rights reserved.)

A novel mathematical model was developed to estimate the volumetric nitrogen conversion rates of a high-rate Anammox UASB reactor based on the packing patterns of granular sludge. A series of relationships among granular packing density, sludge concentration, hydraulic retention time and volumetric conversion rate were constructed to correlate Anammox reactor performance with granular packing patterns. It was suggested that the Anammox granules packed as the equivalent simple cubic pattern in high-rate UASB reactor with packing density of 50-55%, which not only accommodated a high concentration of sludge inside the reactor, but also provided large pore volume, thus prolonging the actual substrate conversion time. Results also indicated that it was necessary to improve Anammox reactor performance by enhancing substrate loading when sludge concentration was higher than 37.8 gVSS/L. The established model was carefully calibrated and verified, and it well simulated the performance of granule-based high-rate Anammox UASB reactor., (Copyright © 2013 Elsevier B.V. All rights reserved.)

Nitrogen pollution created severe environmental problems and increasingly has become an important issue in China. Since the first discovery of ANAMMOX in the early 1990s, this related technology has become a promising as well as sustainable bioprocess for treating strong nitrogenous wastewater. Many Chinese research groups have concentrated their efforts on the ANAMMOX research including bacteria, process development, and application during the past 20 years. A series of new and outstanding outcomes including the discovery of new ANAMMOX bacterial species (Brocadia sinica), sulfate-dependent ANAMMOX bacteria (Anammoxoglobus sulfate and Bacillus benzoevorans), and the highest nitrogen removal performance (74.3-76.7 kg-N/m(3)/d) in lab scale granule-based UASB reactors around the world were achieved. The characteristics, structure, packing pattern and floatation mechanism of the high-rate ANAMMOX granules in ANAMMOX reactors were also carefully illustrated by native researchers. Nowadays, some pilot and full-scale ANAMMOX reactors were constructed to treat different types of ammonium-rich wastewater including monosodium glutamate wastewater, pharmaceutical wastewater, and leachate. The prime objective of the present review is to elucidate the ongoing ANAMMOX research in China from lab scale to full scale applications, comparative analysis, and evaluation of significant findings and to set a design to usher ANAMMOX research in culmination.

The granulation of anammox sludge plays an important role in the high nitrogen removal performance of the anammox reactor. In this study, anaerobic granular sludge was selected as the seeding sludge to start up anammox reactor in order to directly obtain anammox granules. Results showed that the anammox UASB reactor was successfully started up by inoculating anaerobic granular sludge, with substrate capacity of 4435.2 mg/(L · d) and average ammonium and nitrite removal efficiency of 90.36% and 93.29%, respectively. During the start-up course, the granular sludge initially disintegrated and then reaggregated and turned red, suggesting the high anammox performance. Zn-Fe precipitation was observed on the surface of granules during the operation by SEM-EDS, which would impose inhibition to the anammox activity of the granules. Accordingly, it is suggested to relatively reduce the trace metals concentrations, of Fe and Zn in the conventional medium. The findings of this study are expected to be used for a shorter start-up and more stable operation of anammox system.

Efficient biological nitrogen removal from pharmaceutical wastewater has been focused recently. The present study dealt with the treatment of colistin sulfate and kitasamycin manufacturing wastewater through anaerobic ammonium oxidation (ANAMMOX). The biotoxicity assay on luminescent bacterium Photobacterium phosphoreum (T3 mutation) showed that the pharmaceutical wastewater imparted severe toxicity with a relative luminosity of 3.46% ± 0.45%. During long-term operation, the cumulative toxicity from toxic pollutants in wastewater resulted in the performance collapse of conventional ANAMMOX process. A novel ANAMMOX process with sequential biocatalyst (ANAMMOX granules) addition (SBA-ANAMMOX process) was developed by combining high-rate ANAMMOX reactor with sequential biocatalyst addition (SBA). At biocatalyst addition rate of 0.025 g VSS (L wastewater)(-1) day(-1), the nitrogen removal rate of the process reached up to 9.4 kg N m(-3) day(-1) in pharmaceutical wastewater treatment. The effluent ammonium concentration was lower than 50 mg N L(-1), which met the Discharge Standard of Water Pollutants for Pharmaceutical Industry in China (GB 21903-2008). The application of SBA-ANAMMOX process in refractory ammonium-rich wastewater is promising., (Copyright © 2010 Elsevier Ltd. All rights reserved.)

Both ammonium and nitrite act as substrates as well as potential inhibitors of anoxic ammonium-oxidizing (Anammox) bacteria. To satisfy demand of substrates for Anammox bacteria and to prevent substrate inhibition simultaneously; two strategies, namely high or low substrate concentration, were carefully compared in the operation of two Anammox upflow anaerobic sludge blanket (UASB) reactors fed with different substrate concentrations. The reactor working at relatively low influent substrate concentration (NO(2)(-)-N, 240 mg-NL(-1)) was shown to avoid the inhibition caused by nitrite and free ammonia. Using the strategy of low substrate concentration, a record super high volumetric nitrogen removal rate of 45.24 kg-Nm(-3) day(-1) was noted after the operation of 230 days. To our knowledge, such a high value has not been reported previously. The evidence from transmission electron microscopy (TEM) showed that the morphology and ultrastructure of the Anammox cells in both the reactor enrichments was different., (Copyright 2010 Elsevier B.V. All rights reserved.)

Various studies have revealed anaerobic ammonium oxidation (anammox) as a very attractive alternative process suitable for nitrogen removal from wastewater. Here we investigated anammox bacteria in eight different nitrogen removal reactors. The diversity and abundance of anammox bacteria were determined by the 16S rRNA gene analysis, fluorescence in situ hybridization with specific probes and real-time quantitative PCR (qPCR). In these reactors, at least eight unique near full length anammox 16S rRNA gene sequences were detected, which were distributed over two genera; Candidati Brocadia and Kuenenia. FISH results confirmed that only one anammox bacterium dominated the community in each of the eight reactors investigated in this study. qPCR analysis revealed that anammox bacteria were present in seven of the reactors in the order of 10(9) cells/ml and 10(7) cells/ml in reactor A1. The dominant and divergent Brocadia-like anammox phylotype in one reactor represented a novel species for which we propose the name Candidatus Brocadia sinica. Taken together, these results indicated that a single seeding source could be used to seed anammox reactors designed to treat different types of wastewater, which could lead to a faster start-up of bioreactors., (Copyright © 2010 Elsevier Ltd. All rights reserved.)

Vigorous anaerobic ammonium oxidation (anammox) activity was realized by seeding with diverse sludge contents. Granules taken from a 2-year old methanogenic reactor loaded with high organic and methanol contents were used as inoculum to enrich anammox biomass in a 1.1L upflow anaerobic sludge blanket reactor. Anammox activity appeared after an operation of 83 d resulting in the final nitrogen removal rate of 11.7 kg N m(-3) d(-1) with the efficient granulation of anammox sludge. The analysis based on 16S rDNA sequencing confirmed that Candidatus "Brocadia" was the dominant population in the enriched biomass., (2010 Elsevier Ltd. All rights reserved.)

The effect of organic matter on the nitrogen removal performance of anaerobic ammonium oxidation (Anammox) process was investigated in an upflow anaerobic sludge blanket (UASB) reactor fed with nitrogen loading rate of 13.92 kg Nm(-3)day(-1) at an HRT of 0.83 h. Mass balance showed that the heterotrophic denitrification prevailed in the UASB reactor, and became the dominant reactions when high influent COD/NO(2)(-)-N ratios of 2.92 were applied. The Anammox bacterial growth was significantly suppressed by denitrifying communities under high organic matter content due to the weaker competition for nitrite (electron acceptor) and living space. Long-term operation of the Anammox UASB reactor under relatively high organic content resulted in weak recovery performance., (Copyright (c) 2009 Elsevier Ltd. All rights reserved.)

Nitrogen pollution of waters has sometimes caused severe eutrophication, leading to the death of fishes and most aquatic life. There is therefore a need for efficient and cost-effective methods to remove nitrogen from ammonium-rich wastewaters. Anaerobic ammonium oxidation (ANAMMOX) is a promising process to remove nitrogen because this process directly oxidizes ammonium (NH ) to dinitrogen gas (N) under anoxic condition. Nonetheless, a challenge of this process is that chemolithoautotrophic Anammox bacteria grow slowly at the beginning, thus resulting in low Anammox biomass and instability of reactors. Such issues can be overcome by granulation of the Anammox sludge. Here, we review the characteristics of the Anammox bacteria, and the formation, structure and flotation of Anammox granules under high hydraulic loadings. We also evaluate the performances of full-scale granular Anammox processes. The major points are: 1) Anammox bacteria secrete a large amount of extracellular polymeric substances (EPS), up to 415 mg g of volatile suspended solids (VSS), containing many hydrophobic functional groups that facilitate biomass granulation. 2) Granulation enhances the sludge settling property and retention time, which contributes to the extremely high nitrogen removal rate of 77 kg m d of Anammox upflow reactors. 3) Flotation of Anammox granules frequently occurs under nitrogen removal rate higher than 10 kg m d, which is mainly due to the overproduction of EPS under high hydraulic conditions. [ABSTRACT FROM AUTHOR]

The spread application of nanoparticles (NPs) would cause instability on anaerobic ammonium oxidation (anammox) process. The present study focused on the short-term evaluation of ZnO nanoparticles (NPs) on anammox process by batch tests. Results indicated that a significant inhibition occurred under ZnO NPs stress of 5–100 mg gVSS −1 . The half inhibitory concentration (IC 50 ) of ZnO NPs was found to be 11.6 mg gVSS −1 . The release of zinc ions from ZnO NPs dissolution was confirmed to be the main mechanism of inhibition on anammox activity. Haldane kinetic model simulation results confirmed that ZnO NPs imposed a non-competitive inhibition on nitrite conversion by decreasing maximum nitrogen removal rate ( q max ), while they showed a competitive inhibition on ammonium conversion kinetics with affinity constant ( K s ) increasing by 6 times. From the competitive inhibition results, it is suggested that the inhibition caused by ZnO NPs could be alleviated and recovered under higher ammonium concentrations. [ABSTRACT FROM AUTHOR]

[Display omitted] • Pyrite alleviates NO 2 − inhibition and enhances 14% TN removal. • Pyrite reduces NO 3 − production and enhances 19% TN removal. • Metatranscriptome analysis confirms the enhancement of autotrophic denitrification. • Pyrite enhances heterotrophic denitrification by stimulating EPS secretion. Fe and S could improve the anammox performance by coupling with the N cycle. However, the coexistence of Fe and S complicates the metabolic process, troubling the quantification of nitrogen removal pathways. Herein, the nitrogen removal pathways were quantificationally analyzed by 15N stable isotope tracing and elaborate batch tests, and the enhancing mechanism was illuminated by physiological and metatranscriptome analyses in pyrite (FeS 2)-amended anammox system. We found that anammox, denitrification and Feammox (NH 4 + oxidation coupled with Fe(III) reduction) contributed to 80.22 %, 19.53 % and 0.25 % nitrogen removal in this process. With pyrite addition, Fe, S release and the extracellular polymeric substances secretion were responsible for the enhancement of nitrite and nitrate removal via chemical, autotrophic and heterotrophic denitrification, improving nitrogen removal by 14 % and 19 %. The network analyses further confirmed that the multiple nitrogen removal pathways (i.e., anammox, Feammox and denitrification) contribute to pyrite-induced nitrogen removal enhancement in the anammox system. This work enables the in-depth understanding, future design and optimization of the pyrite-amended anammox system, providing a fundamental basis for developing Fe- and S-based anammox enhancement technologies. [ABSTRACT FROM AUTHOR]

Abstract: Microscopic observation and settling test were carried out to investigate the structure, density and settlability of anammox granules taken from a high-rate upflow anaerobic sludge blanket (UASB) reactor. The results showed that the anammox granules were irregular in shape and uneven on surface, and their structure included granule, subunit, microbial cell cluster and single cell. The gas pockets were often observed in the anammox granules, and they originated from the obstruction of gas tunnel by extracellular polymer substances (EPSs) and the inflation of produced dinitrogen gas. The volume of gas pockets became larger with the increasing diameter of anammox granules, which led to the decreasing density and the floatation of anammox granules. The diameter of anammox granules should be controlled at less than 2.20mm to avoid the granule floatation. A hypothesized mechanism for the granulation and floatation of anammox biomass was proposed. [Copyright &y& Elsevier]