The CANON System (Completely Autotrophic Nitrogen-removal Over Nitrite) under Ammonium Limitation: Interaction and Competition between Three Groups of Bacteria

doi:10.1078/0723-2020-00077

Systematic and Applied Microbiology

Volume 24, Issue 4, 2001, Pages 588-596

https://doi.org/10.1078/0723-2020-00077 Get rights and content

Summary

The CANON system (Completely Autotrophic Nitrogen Removal Over Nitrite) can potentially remove ammonium from wastewater in a single, oxygen-limited treatment step. The usefulness of CANON as an industrial process will be determined by the ability of the system to recover from major disturbances in feed composition. The CANON process relies on the stable interaction between only two bacterial populations:Nitrosomonas-like aerobic and Planctomycete-like anaerobic ammonium oxidising bacteria. The effect of extended periods of ammonium limitation was investigated at the laboratory scale in two different reactor types (sequencing batch reactor and chemostat). The lower limit of effective and stable nitrogen removal to dinitrogen gas in the CANON system was 0.1 kg N m^—3 day^—1. At this loading rate, 92% of the total nitrogen was removed. After prolonged exposure (>1 month) to influxes lower than this critical NH₄⁺-influx, a third population of bacteria developed in the system and affected the CANON reaction stoichiometry, resulting in a temporary decrease in nitrogen removal from 92% to 57%. The third group of bacteria were identified by activity tests and qualititative FISH (Fluorescence In Situ Hybridisation) analysis to be nitrite-oxidising Nitrobacter and Nitrospira species. The changes caused by the NH₄⁺-limitation were completely reversible, and the system re-established itself as soon as the ammonium limitation was removed. This study showed that CANON is a robust system for ammonium removal, enduring periods of up to one month of ammonium limitation without irreversible damage.

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Anaerobic ammonium oxidation (ANAMMOX)-mediated system is a cost-effective green nitrogen removal process. However, there are few examples of successful application of this advanced wastewater denitrification process in wastewater treatment plants, and the understanding of how to implement anaerobic ammonia oxidation process in full-scale is still limited. In this study, it was found that the abundance of anaerobic ammonia-oxidizing bacteria (AnAOB) in the two livestock wastewater plants named J1 and J2, respectively, showed diametrically opposed trends of waxing and waning with time. The microbial communities of the activated sludge in the two plants at different time were sampled and analyzed by high-throughput sequencing of 16S rRNA genes. Structural equation models (SEMs) were used to reveal the key factors affecting the realization of the ANAMMOX. Changes in the concentration of dissolved oxygen and C/N had a significant effect on the relative abundance of anaerobic ammonia oxidation bacteria (AnAOB). The low concentration of DO (0.2∼0.5 mg/L) could inhibit the activity of nitrifying bacteria (NOB) to achieve partial oxidation of ammonia nitrogen and provide sufficient substrate for the growth of AnAOB, similar to the CANON (Completely Autotrophic Nitrogen removal Over Nitrite). Unlike CANON, heterotrophic denitrification is also a particularly critical part of the livestock wastewater treatment, and a suitable C/N of about 0.6 could reduce the competition risk of heterotrophic microorganisms to AnAOB and ensure a good ecological niche for AnAOB. Based on the results of 16S rRNA and microbial co-occurrence networks, it was discovered that microorganisms in the sludge not only had a richer network interaction, but also achieved a mutually beneficial symbiotic interaction network among denitrifying bacteria (Pseudomonas sp., Terrimonas sp., Dokdonella sp.), AnAOB (Candidatus Brocadia sp.) at DO of 0.2∼0.5 mg/L and C/N of 0.6. Among the top 20 in abundance of genus level, AnAOB had a high relative abundance of 27.66%, followed by denitrifying bacteria of 3.67%, AOB of 0.64% and NOB of 0.26%, which is an essential indicator for the emergence of an AnAOB-dominated nitrogen removal cycle. In conclusion, this study highlights the importance of dissolved oxygen and C/N regulation by analyzing the mechanism of ANAMMOX sludge extinction and growth in two plants under anthropogenic regulation of AnAOB in full-scale wastewater treatment systems.
Achieving simultaneous removal of carbon and nitrogen by an integrated process of anaerobic membrane bioreactor and flow-through biofilm reactor
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In this study, a combined system consisting of an anaerobic membrane bioreactor (AnMBR) and flow-through biofilm reactor/CANON (FTBR/CANON) was developed to simultaneously remove carbon and nitrogen from synthetic livestock wastewater. The average removal efficiencies of total nitrogen (TN) were 64.2 and 76.4% with influent ammonium (NH₄⁺-N) concentrations of approximately 200 and 500 mg/L, respectively. The COD removal efficiencies were higher than 98.0% during the entire operation. Mass balance analysis showed that COD and TN were mainly removed by the AnMBR and FTBR/CANON, respectively. The anammox process was the main nitrogen removal pathway in the combined system, with a contribution of over 80%. High functional bacterial activity was observed in the combined system. Particularly, an increase in the NH₄⁺-N concentration considerably improved the anammox activity of the biofilm in the FTBR/CANON. 16S rRNA high-throughput sequencing revealed that Methanosaeta, Candidatus Methanofastidiosum, and Methanobacterium were the dominant methanogens in the AnMBR granular sludge. In the CANON biofilm, Nitrosomonas and Candidatus Kuenenia were identified as aerobic and anaerobic ammonium-oxidizing bacteria, respectively. In summary, this study proposes a combined AnMBR and FTBR/CANON process targeting COD and nitrogen removal, and provides a potential alternative for treating high-strength wastewater.
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We investigated the performance of a two-stage partial-nitritation-anammox biocathode integrated microbial desalination cell (TNiA_moxMDC) for concurrent nitrogen removal, desalination, and bioelectricity generation at different aeration rates in the nitritation chamber. The TNiA_moxMDC system achieved a maximum total nitrogen removal rate of 50.4 ± 8.2 g-TN/m³/d with 300 mW/m² of maximum power production utilizing 500 mg/L of glucose chemical oxygen demand (COD) in the anode. The organic removal in the anode chamber showed a good fit to first order reaction model with a rate constant of 0.036 h⁻¹. The biocatalytic activity of anammox bacteria in the biocathode produced a current density of 0.7 A/m² in the absence of oxygen. More than 98% of the salinity was removed at a rate of 1.48 mg/h. The energy consumption values for nitrogen removal at aeration rates of 0.7, 2.2, and 10 ml/min were 0.022, 0.55, and 0.20 kWh/kg-N, respectively. The maximum energy produced by the TNiA_moxMDC was 0.0157 kWh/m³. Excluding the energy consumption by the system, the net energy recovery was 0.0023 kWh/m³ at an airflow rate of 10 ml/min. Thus, the integration of the partial nitritation-anammox process with microbial desalination cell (MDC) provides energy-and resource-efficient synergy for bioelectrochemical wastewater treatment.
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There are various types of reactors for completely autotrophic nitrogen removal over nitrite (CANON) process, but the advantages and disadvantages of different types of reactors and their scope of application still need to be studied. In this paper, high-throughput sequencing technology was used to analyze the microbial characteristics of four CANON reactors with similar and stable influent water quality conditions, and the applicable scenarios of different types of CANON reactors was clarified. At the gene level, the proportions of aerobic ammonia oxidizing bacteria (AerAOB), anaerobic ammonia oxidation bacteria (AnAOB) and denitrifying bacteria in a flocculent sludge sequencing batch reactor (FSBR), a membrane bioreactor (MBR), a biological aerated filter (BAF) and a granular sludge sequencing batch reactor (GSBR) were 16.88 %, 3.49 %, 19.36 % and 29.67 %; 9.51 %, 4.72 %, 5 % and 27.75 %; 7.12 %, 11.5 %, 6.81 % and 13.6 %. The results showed that FSBR was low nitrogen removal load and low stability in practical application. MBR can treat different concentrations of ammonia nitrogen wastewater by controlling the influent load. BAF can treat ammonia nitrogen wastewater with moderate influent load. GSBR has high removal load and can treat high ammonia nitrogen wastewater.

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Systematic and Applied Microbiology

Summary

References (19)

Simultaneous nitrification and denitrification in an aerobic biofilm system

Water Science and Technology

Nitrogen loss in a nitrifying biofilm system

Water Science and technology

Aerobic deammonification – a new experience in the treatment of wastewaters

Water Science and Technology

Towards a more sustainable wastewater treatment system

Water Science and Technology

Nitrogen loss in a nitrifying rotating contactor treating ammonium-rich wastewater without organic carbon

Water Science and Technology

In situ identification of micro-organisms by whole cell hybridisation with rRNA-targeted nucleic acid probes

Single stage nitrogen removal by nitritation and anaerobic ammonium oxidation in biofilm systems

Water Science Technology

Combined molecular and conventional analyses of nitrifying bacterium diversity in activated sludge – Nitrosococcus mobilis and Nitrospira- like bacteria as dominant populations

Applied and environmental microbiology

Cited by (468)

Micro-aeration and low influent C/N are key environmental factors for achieving ANAMMOX in livestock farming wastewater treatment plants

Achieving simultaneous removal of carbon and nitrogen by an integrated process of anaerobic membrane bioreactor and flow-through biofilm reactor

Insights into the rapid start-up of an inoculated municipal sludge system: A high-height-to-diameter-ratio airlift inner-circulation partition bioreactor based on CFD analysis

Resource-efficient nitrogen and salinity removal in a synergistic partial nitritation-anammox bioelectrochemical system

Ecological insight into deterioration of one-stage partial nitritation and anammox system during environmental disturbance

Performance and microbial characteristics of completely autotrophic nitrogen removal over nitrite process in different types of reactors