Low-Dissolved-Oxygen Nitrifying Systems Exploit Ammonia-Oxidizing Bacteria with Unusually High Yields

ABSTRACTIn wastewater treatment plants, nitrifying systems are usually operated with elevated levels of aeration to avoid nitrification failures. This approach contributes significantly to operational costs and the carbon footprint of nitrifying wastewater treatment processes. In this study, we tested the effect of aeration rate on nitrification by correlating ammonia oxidation rates with the structure of the ammonia-oxidizing bacterial (AOB) community and AOB abundance in four parallel continuous-flow reactors operated for 43 days. Two of the reactors were supplied with a constant airflow rate of 0.1 liter/min, while in the other two units the airflow rate was fixed at 4 liters/min. Complete nitrification was achieved in all configurations, though the dissolved oxygen (DO) concentration was only 0.5 ± 0.3 mg/liter in the low-aeration units. The data suggest that efficient performance in the low-DO units resulted from elevated AOB levels in the reactors and/or putative development of a mixotrophic AOB community. Denaturing gel electrophoresis and cloning of AOB 16S rRNA gene fragments followed by sequencing revealed that the AOB community in the low-DO systems was a subset of the community in the high-DO systems. However, in both configurations the dominant species belonged to theNitrosomonas oligotrophalineage. Overall, the results demonstrated that complete nitrification can be achieved at low aeration in lab-scale reactors. If these findings could be extended to full-scale plants, it would be possible to minimize the operational costs and greenhouse gas emissions without risk of nitrification failure.

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Efficient nitrification and low N2O emission in a weakly acidic bioreactor at low dissolved oxygen levels are due to comammox

Applied and Environmental Microbiology ◽

10.1128/aem.00154-21 ◽

2021 ◽

Author(s):

Deyong Li ◽

Fang Fang ◽

Guoqiang Liu

Keyword(s):

Wastewater Treatment ◽

Dissolved Oxygen ◽

Greenhouse Gas ◽

N2o Emission ◽

Low Energy ◽

Emission Source ◽

Ammonia Oxidizer ◽

Ammonia Oxidizing Bacteria ◽

Nitrifier Denitrification ◽

Low Do

Nitrification is an essential process for nutrient removal from wastewater and an important emission source of nitrous-oxide (N2O), which is a powerful greenhouse gas and a dominant ozone-depleting substance. In this study, nitrification and N2O emissions were tested in two weakly acidic (pH = 6.3–6.8) reactors: one with dissolved oxygen (DO) over 2.0 mg/L and the other with DO approximately 0.5 mg/L. Efficient nitrification was achieved in both reactors. Compared to the high-DO reactor, N2O emission in the low-DO reactor decreased slightly by 20% and had insignificant correlation with the fluctuations of DO (P = 0.935) and nitrite (P = 0.713), indicating that N2O might not be mainly produced via nitrifier denitrification. Based on qPCR, qFISH, functional gene amplicon and metagenome sequencing, it was found that complete ammonia oxidizer (comammox) Nitrospira significantly outnumbered canonical ammonia-oxidizing bacteria (AOB) in both weakly acidic reactors, especially in the low DO reactor with the comammox/AOB amoA gene ratio increasing from 6.6 to 17.1. Therefore, it was speculated that the enriched comammox was the primary cause for the slightly decreased N2O emission under long-term low DO in weakly acidic reactor. This study demonstrated that comammox Nitrospira can survive well under the weakly acidic and low-DO conditions, implying that achieving efficient nitrification with low N2O emission as well as low energy and alkalinity consumption is feasible for wastewater treatment. Importance Nitrification in wastewater treatment is an important process for eutrophication control and an emission source for greenhouse gas of N2O. The nitrifying process is usually operated at a slightly alkaline pH and high DO (>2 mg/L) to ensure efficient nitrification. However, it consumes a large amount of energy and chemicals especially for wastewater without sufficient alkalinity. This manuscript demonstrated that comammox can adapt well to the weakly acidic and low-DO bioreactors, with a result of efficient nitrification and low N2O emission. These findings indicate that comammox are significant for sustainable wastewater treatment, which provides an opportunity to achieve efficient nitrification with low N2O production as well as low energy and chemical consumption simultaneously.

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High functional diversity among Nitrospira populations that dominate rotating biological contactor microbial communities in a municipal wastewater treatment plant

10.1101/529826 ◽

2019 ◽

Cited By ~ 4

Author(s):

Emilie Spasov ◽

Jackson M. Tsuji ◽

Laura A. Hug ◽

Andrew C. Doxey ◽

Laura A. Sauder ◽

...

Keyword(s):

Wastewater Treatment ◽

Municipal Wastewater ◽

Ammonia Oxidation ◽

Treatment Plant ◽

16S Rrna Gene Sequencing ◽

Model Systems ◽

Rrna Gene ◽

Ammonia Oxidizing Bacteria ◽

Municipal Wastewater Treatment ◽

Nitrite Oxidizers

AbstractNitrification, the oxidation of ammonia to nitrate via nitrite, is an important process in municipal wastewater treatment plants (WWTPs). Members of the Nitrospira genus that contribute to complete ammonia oxidation (comammox) have only recently been discovered and their relevance to engineered water treatment systems is poorly understood. This study investigated distributions of Nitrospira, ammonia-oxidizing archaea (AOA), and ammonia-oxidizing bacteria (AOB) in biofilm samples collected from tertiary rotating biological contactors (RBCs) of a municipal WWTP in Guelph, Ontario, Canada. Using quantitative PCR (qPCR), 16S rRNA gene sequencing, and metagenomics, our results demonstrate that Nitrospira species strongly dominate RBC biofilm samples and that comammox Nitrospira outnumber all other nitrifiers. Genome bins recovered from assembled metagenomes reveal multiple populations of comammox Nitrospira with distinct spatial and temporal distributions, including several taxa that are distinct from previously characterized Nitrospira members. Diverse functional profiles imply a high level of niche heterogeneity among comammox Nitrospira, in contrast to the sole detected AOA representative that was previously cultivated and characterized from the same RBC biofilm. Our metagenome bins also reveal two cyanase-encoding populations of comammox Nitrospira, suggesting an ability to degrade cyanate, which has not been shown previously for Nitrospira that are not strict nitrite oxidizers. This study demonstrates the importance of RBCs as model systems for continued investigation of environmental factors that control the distributions and activities of AOB, AOA, comammox Nitrospira, and other nitrite oxidizers.

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The Influence of Optic and Polarographic Dissolved Oxygen Sensors Estimating the Volumetric Oxygen Mass Transfer Coefficient (KLa)

Modern Applied Science ◽

10.5539/mas.v10n8p142 ◽

2016 ◽

Vol 10 (8) ◽

pp. 142 ◽

Cited By ~ 1

Author(s):

Gustavo Andrés Baquero-Rodríguez ◽

Jaime A. Lara-Borrero

Keyword(s):

Mass Transfer ◽

Wastewater Treatment ◽

Dissolved Oxygen ◽

Transfer Coefficient ◽

Mass Transfer Coefficient ◽

Oxygen Transfer ◽

Airflow Rate ◽

Oxygen Probe ◽

Aeration System ◽

Oxygen Measurement

Aeration is usually the most energy intensive part of the wastewater treatment process. Optimizing the aeration system is essential for reducing energy costs. Field tests oriented to estimate parameters related to oxygen transfer are a common approach to compare aeration systems. The aim of this research is to assess the effect of dissolved oxygen probe lag on oxygen transfer parameter estimation. Experimental procedures regarding to process automation and control were applied to quantify dissolved oxygen probe lag. We have measured oxygen transfer in clean water, under a wide range of conditions (airflow rate, diffuser characteristics and diffuser density), with optic and polarographic sensors for dissolved oxygen measurement. The oxygen transfer was measured as per ASCE Standard procedures. Nonparametric statistical tests were used to compare the estimated volumetric mass transfer coefficient KLa with different sensors. According to the results, there is not significant influence of the probe lag (also known as time constant) or probe characteristics on the parameters used to assess oxygen transfer efficiency. This fact has great relevance in common practice of aerobic process for wastewater treatment because dissolved oxygen monitoring is used as an input for decision making related to the energy optimization in the aeration system. Findings from these tests contradict previous studies which claim that lag time in polarographic sensors for the dissolved oxygen measurement can bias estimate KLa.

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Meta-azotomics of engineered wastewater treatment processes reveals differential contributions of established and novel models of N-cycling

10.1101/2020.08.25.229054 ◽

2020 ◽

Author(s):

Mee-Rye Park ◽

Medini K. Annavajhala ◽

Kartik Chandran

Keyword(s):

Wastewater Treatment ◽

Ammonia Oxidation ◽

Carbon Sources ◽

N Cycling ◽

Glycerol Metabolism ◽

Ammonia Oxidizing Bacteria ◽

Design And Optimization ◽

Treatment Processes ◽

Upstream Process ◽

Biological Nitrogen

AbstractThe application of metagenomics and metatranscriptomics to field-scale engineered biological nitrogen removal (BNR) processes revealed a complex N-cycle network (the meta-azotome) therein in terms of microbial structure, potential and extant function. Autotrophic nitrification bore the imprint of well-documented Nitrosomonas and Nitrospira in most systems. However, in select BNR processes, complete ammonia oxidizing bacteria, comammox Nitrospira, unexpectedly contributed more substantially to ammonia oxidation than canonical ammonia oxidizing bacteria, based on metatranscriptomic profiling. Methylotrophic denitrification was distinctly active in methanol-fed reactors but not in glycerol-fed reactors. Interestingly, glycerol metabolism and N-reduction transcript signatures were uncoupled, possibly suggesting the role of other carbon sources in denitrification emanating from glycerol itself or from upstream process reactors. In sum, the meta-azotome of engineered BNR processes revealed both traditional and novel mechanisms of N-cycling. Similar interrogation approaches could potentially inform better design and optimization of wastewater treatment and engineered bioprocesses in general.

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Measurements of nitrite production in and around the primary nitrite maximum in the central California Current

Biogeosciences ◽

10.5194/bg-10-7395-2013 ◽

2013 ◽

Vol 10 (11) ◽

pp. 7395-7410 ◽

Cited By ~ 47

Author(s):

A. E. Santoro ◽

C. M. Sakamoto ◽

J. M. Smith ◽

J. N. Plant ◽

A. L. Gehman ◽

...

Keyword(s):

Ammonia Oxidation ◽

Heterotrophic Bacteria ◽

California Current ◽

Euphotic Zone ◽

Ammonia Oxidizing Bacteria ◽

Central California ◽

Oxidation Rates ◽

Ammonia Oxidizing Archaea ◽

Nitrite Production ◽

Nh3 Oxidation

Abstract. Nitrite (NO2−) is a substrate for both oxidative and reductive microbial metabolism. NO2− accumulates at the base of the euphotic zone in oxygenated, stratified open-ocean water columns, forming a feature known as the primary nitrite maximum (PNM). Potential pathways of NO2− production include the oxidation of ammonia (NH3) by ammonia-oxidizing bacteria and archaea as well as assimilatory nitrate (NO3−) reduction by phytoplankton and heterotrophic bacteria. Measurements of NH3 oxidation and NO3− reduction to NO2− were conducted at two stations in the central California Current in the eastern North Pacific to determine the relative contributions of these processes to NO2− production in the PNM. Sensitive (< 10 nmol L−1), precise measurements of [NH4+] and [NO2−] indicated a persistent NH4+ maximum overlying the PNM at every station, with concentrations as high as 1.5 μmol L−1. Within and just below the PNM, NH3 oxidation was the dominant NO2− producing process, with rates of NH3 oxidation to NO2− of up to 31 nmol L−1 d−1, coinciding with high abundances of ammonia-oxidizing archaea. Though little NO2− production from NO3− was detected, potentially nitrate-reducing phytoplankton (photosynthetic picoeukaryotes, Synechococcus, and Prochlorococcus) were present at the depth of the PNM. Rates of NO2− production from NO3− were highest within the upper mixed layer (4.6 nmol L−1 d−1) but were either below detection limits or 10 times lower than NH3 oxidation rates around the PNM. One-dimensional modeling of water column NO2− production agreed with production determined from 15N bottle incubations within the PNM, but a modeled net biological sink for NO2− just below the PNM was not captured in the incubations. Residence time estimates of NO2− within the PNM ranged from 18 to 470 days at the mesotrophic station and was 40 days at the oligotrophic station. Our results suggest the PNM is a dynamic, rather than relict, feature with a source term dominated by ammonia oxidation.

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Indole degrading of ammonia oxidizing bacteria isolated from swine wastewater treatment system

Water Science & Technology ◽

10.2166/wst.2009.312 ◽

2009 ◽

Vol 59 (12) ◽

pp. 2405-2410 ◽

Cited By ~ 9

Author(s):

Ping Li ◽

Lei Tong ◽

Kun Liu ◽

Yanhong Wang ◽

Yanxin Wang

Keyword(s):

Wastewater Treatment ◽

Biochemical Analysis ◽

Ammonia Oxidation ◽

Treatment System ◽

Swine Wastewater ◽

Ammonia Oxidizing Bacteria ◽

16S Rdna Gene ◽

Wastewater Treatment System ◽

Nitrate And Nitrite ◽

Physiological And Biochemical

Three new strains named LPA11, LPB11 and LPC24 were isolated to investigate the patterns of indole degradation and ammonia oxidation in swine wastewater from different parts of a swine wastewater treatment system by the direct spreading plate method. These three isolates were all identified as Pseudomonas putida based on 16S-rDNA gene sequences, main physiological and biochemical analysis. They were capable of decomposing 1.0 mM indole completely in 10, 16 and 18 days respectively. According to the results of HPLC and GC/MS, the possible pathway for the degradation was via oxindole, isatin and anthranilic acid. The three bacteria were capable of oxidizing ammonia, and the strains LPA11 and LPC24 were capable of effectively reducing nitrate and nitrite.

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Nitrification mainly driven by ammonia-oxidizing bacteria and nitrite-oxidizing bacteria in an anammox-inoculated wastewater treatment system

AMB Express ◽

10.1186/s13568-021-01321-6 ◽

2021 ◽

Vol 11 (1) ◽

Author(s):

Jing Lu ◽

Yiguo Hong ◽

Ying Wei ◽

Ji-Dong Gu ◽

Jiapeng Wu ◽

...

Keyword(s):

Wastewater Treatment ◽

Activated Sludge ◽

Nitrogen Removal ◽

High Throughput Sequencing ◽

High Efficiency ◽

Ammonia Oxidation ◽

Ammonia Oxidizing Bacteria ◽

Ammonium Oxidation ◽

Strong Activity ◽

Nitrite Oxidizing Bacteria

AbstractAnaerobic ammonium oxidation (anammox) process has been acknowledged as an environmentally friendly and time-saving technique capable of achieving efficient nitrogen removal. However, the community of nitrification process in anammox-inoculated wastewater treatment plants (WWTPs) has not been elucidated. In this study, ammonia oxidation (AO) and nitrite oxidation (NO) rates were analyzed with the incubation of activated sludge from Xinfeng WWTPs (Taiwan, China), and the community composition of nitrification communities were investigated by high-throughput sequencing. Results showed that both AO and NO had strong activity in the activated sludge. The average rates of AO and NO in sample A were 6.51 µmol L−1 h−1 and 6.52 µmol L−1 h−1, respectively, while the rates in sample B were 14.48 µmol L−1 h−1 and 14.59 µmol L−1 h−1, respectively. The abundance of the nitrite-oxidizing bacteria (NOB) Nitrospira was 0.89–4.95 × 1011 copies/g in both samples A and B, the abundance of ammonia-oxidizing bacteria (AOB) was 1.01–9.74 × 109 copies/g. In contrast, the abundance of ammonia-oxidizing archaea (AOA) was much lower than AOB, only with 1.28–1.53 × 105 copies/g in samples A and B. The AOA community was dominated by Nitrosotenuis, Nitrosocosmicus, and Nitrososphaera, while the AOB community mainly consisted of Nitrosomonas and Nitrosococcus. The dominant species of Nitrospira were Candidatus Nitrospira defluvii, Candidatus Nitrospira Ecomare2 and Nitrospira inopinata. In summary, the strong nitrification activity was mainly catalyzed by AOB and Nitrospira, maintaining high efficiency in nitrogen removal in the anammox-inoculated WWTPs by providing the substrates required for denitrification and anammox processes.

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Quantification of amoA gene abundance and their amoA mRNA levels in activated sludge by real-time PCR

Water Science & Technology ◽

10.2166/wst.2004.0474 ◽

2004 ◽

Vol 50 (8) ◽

pp. 1-8 ◽

Cited By ~ 23

Author(s):

N. Araki ◽

T. Yamaguchi ◽

S. Yamazaki ◽

H. Harada

Keyword(s):

16S Rrna ◽

Dissolved Oxygen ◽

Real Time ◽

Real Time Pcr ◽

Ammonia Oxidation ◽

Amoa Gene ◽

Ammonia Concentration ◽

Ammonia Oxidizing Bacteria ◽

Mrna Levels ◽

Transcription Level

The transcription level of amoA mRNA encoding a subunit of ammonia monooxygenase (AMO) in ammonia-oxidizing bacteria (AOB) was quantified by reverse transcription-polymerase chain reaction (RT-PCR) methods in combination with real-time PCR technology. The effects of ammonia concentration and dissolved oxygen (DO) on the transcription levels of amoA mRNA and 16S rRNA in AOB were evaluated in batch experiments with nitrifying sludge taken from a lab-scale reactor treating artificial wastewater. A batch incubation without ammonia resulted in a rapid decrease, within four hours, in the transcription level of amoA mRNA to as low as 1/10 of that at the beginning of the experiment, while the 16S rRNA level in AOB was almost constant. After subsequent incubation with 3 mM ammonia for eight hours, a small increase in the transcription level of amoA mRNA occurred, but ammonia oxidation proceeded in the interim. Copy numbers of amoA mRNA showed an almost fixed value for over eight hours in the absence of dissolved oxygen.

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The Response of Estuarine Ammonia-Oxidizing Communities to Constant and Fluctuating Salinity Regimes

Frontiers in Microbiology ◽

10.3389/fmicb.2020.574815 ◽

2020 ◽

Vol 11 ◽

Author(s):

João Pereira Santos ◽

António G. G. Sousa ◽

Hugo Ribeiro ◽

Catarina Magalhães

Keyword(s):

Ammonia Oxidation ◽

Estuarine Sediments ◽

Ammonia Oxidizer ◽

Rrna Gene ◽

Ammonia Oxidizing Bacteria ◽

Salinity Regime ◽

Salinity Fluctuation ◽

Ammonia Oxidizing Archaea ◽

Negative Effect ◽

The Impact

Aerobic nitrification is a fundamental nitrogen biogeochemical process that links the oxidation of ammonia to the removal of fixed nitrogen in eutrophicated water bodies. However, in estuarine environments there is an enormous variability of water physicochemical parameters that can affect the ammonia oxidation biological process. For instance, it is known that salinity can affect nitrification performance, yet there is still a lack of information on the ammonia-oxidizing communities behavior facing daily salinity fluctuations. In this work, laboratory experiments using upstream and downstream estuarine sediments were performed to address this missing gap by comparing the effect of daily salinity fluctuations with constant salinity on the activity and diversity of ammonia-oxidizing microorganisms (AOM). Activity and composition of AOM were assessed, respectively by using nitrogen stable isotope technique and 16S rRNA gene metabarcoding analysis. Nitrification activity was negatively affected by daily salinity fluctuations in upstream sediments while no effect was observed in downstream sediments. Constant salinity regime showed clearly higher rates of nitrification in upstream sediments while a similar nitrification performance between the two salinity regimes was registered in the downstream sediments. Results also indicated that daily salinity fluctuation regime had a negative effect on both ammonia-oxidizing bacteria (AOB) and ammonia-oxidizing archaea (AOA) community’s diversity. Phylogenetically, the estuarine downstream AOM were dominated by AOA (0.92–2.09%) followed by NOB (0.99–2%), and then AOB (0.2–0.32%); whereas NOB dominated estuarine upstream sediment samples (1.4–9.5%), followed by AOA (0.27–0.51%) and AOB (0.01–0.23%). Analysis of variance identified the spatial difference between samples (downstream and upstream) as the main drivers of AOA and AOB diversity. Our study indicates that benthic AOM inhabiting different estuarine sites presented distinct plasticity toward the salinity regimes tested. These findings help to improve our understanding in the dynamics of the nitrogen cycle of estuarine systems by showing the resilience and consequently the impact of different salinity regimes on the diversity and activity of ammonia oxidizer communities.

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Microbial community analysis of biofilters reveals a dominance of either comammox Nitrospira or archaea as ammonia oxidizers in freshwater aquaria

10.1101/2021.11.24.468873 ◽

2021 ◽

Author(s):

Michelle M McKnight ◽

Josh D Neufeld

Keyword(s):

Microbial Communities ◽

Ammonia Oxidation ◽

16S Rrna Gene Sequencing ◽

Community Analysis ◽

Microbial Community Analysis ◽

Ammonia Oxidizer ◽

Future Research ◽

Rrna Gene ◽

Ammonia Oxidizing Bacteria ◽

Ammonia Oxidizers

Nitrification by aquarium biofilters transforms toxic ammonia waste (NH3/NH4+) to less toxic nitrate (NO3-) via nitrite (NO2-). Ammonia oxidation is mediated by ammonia-oxidizing bacteria (AOB), ammonia-oxidizing archaea (AOA), and the recently discovered complete ammonia oxidizing (comammox) Nitrospira. Prior to the discovery of comammox Nitrospira, previous research revealed that AOA dominate among ammonia oxidizers in freshwater biofilters. Here, we characterized the composition of aquarium filter microbial communities and quantified the abundance of all three known groups of ammonia oxidizers. Aquarium biofilter and water samples were collected from representative freshwater and saltwater systems in Southwestern Ontario, Canada. Using extracted DNA, we performed 16S rRNA gene sequencing and quantitative PCR (qPCR) to assess community composition and quantify the abundance of amoA genes, respectively. Our results show that aquarium biofilter microbial communities were consistently represented by putative heterotrophs of the Proteobacteria and Bacteroides phyla, with distinct profiles associated with fresh versus saltwater biofilters. Among nitrifiers, comammox Nitrospira amoA genes were detected in all 38 freshwater aquarium biofilter samples and were the most abundant ammonia oxidizer in 30 of these samples, with the remaining biofilters dominated by AOA, based on amoA gene abundances. In saltwater biofilters, AOA or AOB were differentially abundant, with no comammox Nitrospira detected. These results demonstrate that comammox Nitrospira play an important role in biofilter nitrification that has been previously overlooked and such microcosms are useful for exploring the ecology of nitrification for future research.

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