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Wang L, Zhang C, Kang X, Liu Y, Qiu Y, Wanyan D, Liu J, Cheng G, Huang X. Establishing mainstream partial nitrification in the membrane aerated biofilm reactor by limiting the oxygen concentration in the biofilm. WATER RESEARCH 2024; 261:121984. [PMID: 38924949 DOI: 10.1016/j.watres.2024.121984] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/22/2024] [Revised: 06/13/2024] [Accepted: 06/20/2024] [Indexed: 06/28/2024]
Abstract
The proliferation of nitrite oxidizing bacteria (NOB) still remains as a major challenge for nitrogen removal in mainstream wastewater treatment process based on partial nitrification (PN). This study investigated different operational conditions to establish mainstream PN for the fast start-up of membrane aerated biofilm reactor (MABR) systems. Different oxygen controlling strategies were adopted by employing different influent NH4+-N loads and oxygen supply strategies to inhibit NOB. We indicated the essential for NOB suppression was to reduce the oxygen concentration of the inner biofilm and the thickness of aerobic biofilm. A higher NH4+-N load (7.4 g-N/(m2·d)) induced higher oxygen utilization rate (14.4 g-O2/(m2·d)) and steeper gradient of oxygen concentration, which reduced the thickness of aerobic biofilm. Employing closed-end oxygen supply mode exhibited the minimum concentration of oxygen to realize PN, which was over 46% reduction of the normal open-end oxygen mode. Under the conditions of high NH4+-N load and closed-end oxygen supply mode, the microbial community exhibited a comparative advantage of ammonium oxidizing bacteria over NOB in the aerobic biofilm, with a relative abundance of Nitrosomonas of 30-40% and no detection of Nitrospira. The optimal fast start-up strategy was proposed with open-end aeration mode in the first 10 days and closed-end mode subsequently under high NH4+-N load. The results revealed the mechanism of NOB inhibition on the biofilm and provided strategies for a quick start-up and stable mainstream PN simultaneously, which poses great significance for the future application of MABR.
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Affiliation(s)
- Lisheng Wang
- State Key Joint Laboratory of Environment Simulation and Pollution Control, School of Environment, Tsinghua University, Beijing, China
| | - Congcong Zhang
- State Key Joint Laboratory of Environment Simulation and Pollution Control, School of Environment, Tsinghua University, Beijing, China
| | - Xiaofeng Kang
- State Key Joint Laboratory of Environment Simulation and Pollution Control, School of Environment, Tsinghua University, Beijing, China
| | - Yanchen Liu
- State Key Joint Laboratory of Environment Simulation and Pollution Control, School of Environment, Tsinghua University, Beijing, China
| | - Yong Qiu
- State Key Joint Laboratory of Environment Simulation and Pollution Control, School of Environment, Tsinghua University, Beijing, China
| | - Deqing Wanyan
- Research Institute for Environmental Innovation (Suzhou) Tsinghua, Suzhou 215009, China
| | - Jiayin Liu
- Research Institute for Environmental Innovation (Suzhou) Tsinghua, Suzhou 215009, China
| | - Gang Cheng
- Research Institute for Environmental Innovation (Suzhou) Tsinghua, Suzhou 215009, China
| | - Xia Huang
- State Key Joint Laboratory of Environment Simulation and Pollution Control, School of Environment, Tsinghua University, Beijing, China; Research and Application Centre for Membrane Technology, School of Environment, Tsinghua University, Beijing, 100084, China.
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Aqeel H, Asefa B, Liss SN. Nitrospira dominant pin-point flocs with granule-like settleability in stirred tank reactors with oxic/hypoxic/oxic zones. Front Microbiol 2023; 14:1307727. [PMID: 38111639 PMCID: PMC10726125 DOI: 10.3389/fmicb.2023.1307727] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2023] [Accepted: 11/16/2023] [Indexed: 12/20/2023] Open
Abstract
The characteristics of biomass and microbial community dynamics, in relation to autotrophic nitrification, were studied in two 20 L stirred tank reactors (STR) with oxic/hypoxic/oxic zones. The bioreactors were fed with synthetic wastewater with stepwise increasing ammonia concentrations (50-200 N mg/L) without organic substrate in the first phase (autotrophic phase) for 35 days (R1) and 15 days (R2), followed by a heterotrophic phase (with supplementation of organic substrate). The settling properties of the biomass, represented by pin-point flocs, gradually improved in both reactors during the autotrophic phase. The pin-point flocs of R1 exhibited granule-like settling properties. The SVI30 in RI gradually improved to 29 mL/g MLSS, and the corresponding SVI30/ SVI10 gradually improved to 0.88 during the autotrophic phase. The settling properties of the biomass deteriorated in both bioreactors during the heterotrophic phase. The protein to polysaccharide ratio (PN:PS ratio) gradually increased in the extracted EPS (in both, loosely bound (LB) and tightly bound (TB) EPS) during the autotrophic phase, in both bioreactors. The TB:LB EPS ratio was higher when the pin-point flocs of R1 showed granule-like settling properties, followed by a decline in TB:LB EPS ratio during the heterotrophic phase. A combination of molecular approaches (droplet digital-PCR (dd-PCR) and 16S rRNA gene sequencing) revealed that Nitrospira were the predominant nitrifying bacteria in the pin-point flocs that show granular sludge-like settling properties during autotrophic phase in R1. Comammox Nitrospira was the dominant ammonia oxidizer in seed biomass and at low ammonia concentrations in both bioreactors. The relative abundance of canonical ammonia-oxidizing bacteria increased with an increase in influent-ammonia concentrations.
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Affiliation(s)
- Hussain Aqeel
- Chemistry and Biology, Toronto Metropolitan University, Toronto, ON, Canada
| | - Bruke Asefa
- Chemistry and Biology, Toronto Metropolitan University, Toronto, ON, Canada
| | - Steven N. Liss
- Chemistry and Biology, Toronto Metropolitan University, Toronto, ON, Canada
- School of Environmental Studies, Queen’s University, Kingston, ON, Canada
- Department of Microbiology, Stellenbosch University, Stellenbosch, Western Cape, South Africa
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Verma S, Kuila A, Jacob S. Role of Biofilms in Waste Water Treatment. Appl Biochem Biotechnol 2023; 195:5618-5642. [PMID: 36094648 DOI: 10.1007/s12010-022-04163-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 08/28/2022] [Indexed: 11/02/2022]
Abstract
Biofilm cells have a different physiology than planktonic cells, which has been the focus of most research. Biofilms are complex biostructures that form on any surface that comes into contact with water on a regular basis. They are dynamic, structurally complex systems having characteristics of multicellular animals and multiple ecosystems. The three themes covered in this review are biofilm ecology, biofilm reactor technology and design, and biofilm modeling. Membrane-supported biofilm reactors, moving bed biofilm reactors, granular sludge, and integrated fixed-film activated sludge processes are all examples of biofilm reactors used for water treatment. Biofilm control and/or beneficial application in membrane processes are improving. Biofilm models have become critical tools for biofilm foundational research as well as biofilm reactor architecture and design. At the same time, the differences between biofilm modeling and biofilm reactor modeling methods are acknowledged.
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Affiliation(s)
- Samakshi Verma
- Department of Bioscience and Biotechnology, Banasthali Vidyapith, Rajasthan, 304022, India
| | - Arindam Kuila
- Department of Bioscience and Biotechnology, Banasthali Vidyapith, Rajasthan, 304022, India.
| | - Samuel Jacob
- Department of Biotechnology, School of Bioengineering, College of Engineering and Technology, Faculty of Engineering and Technology, SRM Institute of Science and Technology, SRM Nagar, Chengalpattu Dist., Kattankulathur, 603203, Tamil Nadu, India.
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Zhang C, Chen X, Han M, Li X, Chang H, Ren N, Ho SH. Revealing the role of microalgae-bacteria niche for boosting wastewater treatment and energy reclamation in response to temperature. ENVIRONMENTAL SCIENCE AND ECOTECHNOLOGY 2023; 14:100230. [PMID: 36590875 PMCID: PMC9800309 DOI: 10.1016/j.ese.2022.100230] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/20/2022] [Revised: 11/30/2022] [Accepted: 12/01/2022] [Indexed: 06/17/2023]
Abstract
Conventional biological treatment usually cannot achieve the same high water quality as advanced treatment when conducted under varied temperatures. Here, satisfactory wastewater treatment efficiency was observed in a microalgae-bacteria consortia (MBC) over a wide temperature range because of the predominance of microalgae. Microalgae contributed more toward wastewater treatment at low temperature because of the unsatisfactory performance of the accompanying bacteria, which experienced cold stress (e.g., bacterial abundance below 3000 sequences) and executed defensive strategies (e.g., enrichment of cold-shock proteins). A low abundance of amoA-C and hao indicated that conventional nitrogen removal was replaced through the involvement of microalgae. Diverse heterotrophic bacteria for nitrogen removal were identified at medium and high temperatures, implying this microbial niche treatment contained diverse flexible consortia with temperature variation. Additionally, pathogenic bacteria were eliminated through microalgal photosynthesis. After fitting the neutral community model and calculating the ecological niche, microalgae achieved a maximum niche breadth of 5.21 and the lowest niche overlap of 0.38, while the accompanying bacterial community in the consortia were shaped through deterministic processes. Finally, the maximum energy yield of 87.4 kJ L-1 and lipid production of 1.9 g L-1 were achieved at medium temperature. Altogether, this study demonstrates that advanced treatment and energy reclamation can be achieved through microalgae-bacteria niche strategies.
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Affiliation(s)
- Chaofan Zhang
- State Key Laboratory of Urban Water Resource and Environment, School of Environment, Harbin Institute of Technology, Harbin, 150090, PR China
| | - Xi Chen
- State Key Laboratory of Urban Water Resource and Environment, School of Environment, Harbin Institute of Technology, Harbin, 150090, PR China
| | - Meina Han
- State Key Laboratory of Urban Water Resource and Environment, School of Environment, Harbin Institute of Technology, Harbin, 150090, PR China
| | - Xue Li
- State Key Laboratory of Urban Water Resource and Environment, School of Environment, Harbin Institute of Technology, Harbin, 150090, PR China
| | - Haixing Chang
- School of Chemistry and Chemical Engineering, Chongqing University of Technology, Chongqing, 400054, PR China
| | - Nanqi Ren
- State Key Laboratory of Urban Water Resource and Environment, School of Environment, Harbin Institute of Technology, Harbin, 150090, PR China
| | - Shih-Hsin Ho
- State Key Laboratory of Urban Water Resource and Environment, School of Environment, Harbin Institute of Technology, Harbin, 150090, PR China
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Petrovich ML, Rosenthal AF, Griffin JS, Wells GF. Spatially resolved abundances of antibiotic resistance genes and intI1 in wastewater treatment biofilms. Biotechnol Bioeng 2018; 116:543-554. [PMID: 30512194 DOI: 10.1002/bit.26887] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2018] [Revised: 11/15/2018] [Accepted: 11/29/2018] [Indexed: 12/12/2022]
Abstract
Attached growth bioprocesses that use biofilms to remove organic matter or nutrients from wastewater are known to harbor antibiotic resistance genes (ARGs). Biofilms in these processes are spatially heterogeneous, but little is known about depth stratification of ARGs in complex, mixed culture biofilms. To address this knowledge gap, we used an experimental approach combining cryosectioning and quantitative polymerase chain reaction to quantify the spatial distribution of three ARGs (sul1, ermB, and qnrS) and the class 1 integron-integrase gene intI1 in biofilms from a lab-scale rotating annular reactor fed with synthetic wastewater. We also used high throughput 16S ribosomal RNA (rRNA) gene sequencing to characterize community structure with depth in biofilms. The ARG sul1 and the integron-integrase gene intI1 were found in higher abundances in upper layers of biofilm near the fluid-biofilm interface than in lower layers and exhibited significant correlations between the distance from substratum and gene abundances. The genes ermB and qnrS were present in comparatively low relative abundances. Microbial community structure varied significantly by date of sampling and distance from the substratum. These findings highlight the genetic and taxonomic heterogeneity with distance from substratum in wastewater treatment biofilms and show that sul1 and intI1 are particularly abundant near fluid-biofilm interfaces where cells are most likely to detach and flow into downstream portions of treatment systems and can ultimately be released into the environment through effluent.
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Affiliation(s)
- Morgan L Petrovich
- Department of Civil and Environmental Engineering, Northwestern University, Evanston, Illinois
| | - Alex F Rosenthal
- Department of Civil and Environmental Engineering, Northwestern University, Evanston, Illinois
| | - James S Griffin
- Department of Chemical and Biological Engineering, Northwestern University, Evanston, Illinois
| | - George F Wells
- Department of Civil and Environmental Engineering, Northwestern University, Evanston, Illinois
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Kinnunen M, Dechesne A, Albrechtsen HJ, Smets BF. Stochastic processes govern invasion success in microbial communities when the invader is phylogenetically close to resident bacteria. THE ISME JOURNAL 2018; 12:2748-2756. [PMID: 30002504 PMCID: PMC6194134 DOI: 10.1038/s41396-018-0202-1] [Citation(s) in RCA: 32] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/18/2017] [Revised: 04/12/2018] [Accepted: 05/11/2018] [Indexed: 12/28/2022]
Abstract
Despite recent efforts in identifying the determinants of invasion in microbial communities, experimental observations across different ecosystems are inconclusive. While relationships between resident community diversity and invasion success are often noted, community diversity says little about community assembly processes. Community assembly processes may provide a more inclusive framework to explain-and potentially prevent or facilitate-invasion. Here we let replicate nitrite-oxidizing bacterial guilds assemble under different conditions from a natural source community and study their compositional patterns to infer the relative importance of the assembly processes. Then, an invader strain from that same guild was introduced at one of three propagule pressures. We found no significant correlation between community diversity and invasion success. Instead, we observed that the effect of selection on invasion success was surpassed by the effect of drift, as inferred from the substantial influence of propagule pressure on invasion success. This dominance of drift can probably be generalized to other invasion cases with high phylogenetic similarity between invader and resident community members. In these situations, our results suggest that attempting to modulate the invasibility of a community by altering its diversity is futile because stochastic processes determine the invasion outcome. Increasing or reducing propagule pressure is then deemed the most efficient avenue to enhance or limit invasion success.
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Affiliation(s)
- Marta Kinnunen
- Department of Environmental Engineering, Technical University of Denmark, Bygningstorvet 115, 2800 Kgs, Lyngby, Denmark
- Novozymes A/S, Microbial Discovery, Krogshoejvej 36, Bagsvaerd, DK-2880, Denmark
| | - Arnaud Dechesne
- Department of Environmental Engineering, Technical University of Denmark, Bygningstorvet 115, 2800 Kgs, Lyngby, Denmark
| | - Hans-Jørgen Albrechtsen
- Department of Environmental Engineering, Technical University of Denmark, Bygningstorvet 115, 2800 Kgs, Lyngby, Denmark
| | - Barth F Smets
- Department of Environmental Engineering, Technical University of Denmark, Bygningstorvet 115, 2800 Kgs, Lyngby, Denmark.
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Keller AH, Kleinsteuber S, Vogt C. Anaerobic Benzene Mineralization by Nitrate-Reducing and Sulfate-Reducing Microbial Consortia Enriched From the Same Site: Comparison of Community Composition and Degradation Characteristics. MICROBIAL ECOLOGY 2018; 75:941-953. [PMID: 29124312 DOI: 10.1007/s00248-017-1100-1] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/13/2017] [Accepted: 10/26/2017] [Indexed: 05/22/2023]
Abstract
Benzene mineralization under nitrate-reducing conditions was successfully established in an on-site reactor continuously fed with nitrate and sulfidic, benzene-containing groundwater extracted from a contaminated aquifer. Filling material from the reactor columns was used to set up anoxic enrichment cultures in mineral medium with benzene as electron donor and sole organic carbon source and nitrate as electron acceptor. Benzene degradation characteristics and community composition under nitrate-reducing conditions were monitored and compared to those of a well-investigated benzene-mineralizing consortium enriched from the same column system under sulfate-reducing conditions. The nitrate-reducing cultures degraded benzene at a rate of 10.1 ± 1.7 μM d-1, accompanied by simultaneous reduction of nitrate to nitrite. The previously studied sulfate-reducing culture degraded benzene at similar rates. Carbon and hydrogen stable isotope enrichment factors determined for nitrate-dependent benzene degradation differed significantly from those of the sulfate-reducing culture (ΛH/C nitrate = 12 ± 3 compared to ΛH/C sulfate = 28 ± 3), indicating different benzene activation mechanisms under the two conditions. The nitrate-reducing community was mainly composed of Betaproteobacteria, Ignavibacteria, and Anaerolineae. Azoarcus and a phylotype related to clone Dok59 (Rhodocyclaceae) were the dominant genera, indicating an involvement in nitrate-dependent benzene degradation. The primary benzene degrader of the sulfate-reducing consortium, a phylotype belonging to the Peptococcaceae, was absent in the nitrate-reducing consortium.
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Affiliation(s)
- Andreas H Keller
- Department of Isotope Biogeochemistry, Helmholtz Centre for Environmental Research-UFZ, Permoserstraße 15, 04318, Leipzig, Germany
- Department of Environmental Microbiology, Helmholtz Centre for Environmental Research-UFZ, Permoserstraße 15, 04318, Leipzig, Germany
| | - Sabine Kleinsteuber
- Department of Environmental Microbiology, Helmholtz Centre for Environmental Research-UFZ, Permoserstraße 15, 04318, Leipzig, Germany
| | - Carsten Vogt
- Department of Isotope Biogeochemistry, Helmholtz Centre for Environmental Research-UFZ, Permoserstraße 15, 04318, Leipzig, Germany.
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Ma C, Jensen MM, Smets BF, Thamdrup B. Pathways and Controls of N 2O Production in Nitritation-Anammox Biomass. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2017; 51:8981-8991. [PMID: 28669192 DOI: 10.1021/acs.est.7b01225] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/21/2023]
Abstract
Nitrous oxide (N2O) is an unwanted byproduct during biological nitrogen removal processes in wastewater. To establish strategies for N2O mitigation, a better understanding of production mechanisms and their controls is required. A novel stable isotope labeling approach using 15N and 18O was applied to investigate pathways and controls of N2O production by biomass taken from a full-scale nitritation-anammox reactor. The experiments showed that heterotrophic denitrification was a negligible source of N2O under oxic conditions (≥0.2 mg O2 L-1). Both hydroxylamine oxidation and nitrifier denitrification contributed substantially to N2O accumulation across a wide range of conditions with varying concentrations of O2, NH4+, and NO2-. The O2 concentration exerted the strongest control on net N2O production with both production pathways stimulated by low O2, independent of NO2- concentrations. The stimulation of N2O production from hydroxylamine oxidation at low O2 was unexpected and suggests that more than one enzymatic pathway may be involved in this process. N2O production by hydroxylamine oxidation was further stimulated by NH4+, whereas nitrifier denitrification at low O2 levels was stimulated by NO2- at levels as low as 0.2 mM. Our study shows that 15N and 18O isotope labeling is a useful approach for direct quantification of N2O production pathways applicable to diverse environments.
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Affiliation(s)
- Chun Ma
- Department of Biology, University of Southern Denmark , 5230 Odense M, Denmark
| | - Marlene Mark Jensen
- Department of Environmental Engineering, Technical University of Denmark , 2800 Kongens Lyngby, Denmark
| | - Barth F Smets
- Department of Environmental Engineering, Technical University of Denmark , 2800 Kongens Lyngby, Denmark
| | - Bo Thamdrup
- Department of Biology, University of Southern Denmark , 5230 Odense M, Denmark
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Eva S. Longterm Monitoring of Nitrification and Nitrifying Communities during Biofilter Activation of Two Marine Recirculation Aquaculture Systems (RAS). ACTA ACUST UNITED AC 2017. [DOI: 10.17352/2455-8400.000029] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
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Ma Y, Domingo-Félez C, Plósz BG, Smets BF. Intermittent Aeration Suppresses Nitrite-Oxidizing Bacteria in Membrane-Aerated Biofilms: A Model-Based Explanation. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2017; 51:6146-6155. [PMID: 28448139 DOI: 10.1021/acs.est.7b00463] [Citation(s) in RCA: 46] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Autotrophic ammonium oxidation in membrane-aerated biofilm reactors (MABRs) can make treatment of ammonium-rich wastewaters more energy-efficient, especially within the context of short-cut ammonium removal. The challenge is to exclusively enrich ammonium-oxidizing bacteria (AOB). To achieve nitritation, strategies to suppress nitrite-oxidizing bacteria (NOB) are needed, which are ideally grounded on an understanding of underlying mechanisms. In this study, a nitrifying MABR was operated under intermittent aeration. During eight months of operation, AOB dominated, while NOB were suppressed. On the basis of dissolved oxygen (DO), ammonium, nitrite, and nitrate profiles within the biofilm and in the bulk, a 1-dimensional nitrifying biofilm model was developed and calibrated. The model was utilized to explore the potential mechanisms of NOB suppression associated with intermittent aeration, considering DO limitation, direct pH effects on enzymatic activities, and indirect pH effects on activity via substrate speciation. The model predicted strong periodic shifts in the spatial gradients of DO, pH, free ammonia, and free nitrous acid, associated with aerated and nonaerated phases. NOB suppression during intermittent aeration was mostly explained by periodic inhibition caused by free ammonia due to periodic transient pH upshifts. Dissolved oxygen limitation did not govern NOB suppression. Different intermittent aeration strategies were then evaluated for nitritation success in intermittently aerated MABRs: both aeration intermittency and duration were effective control parameters.
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Affiliation(s)
- Yunjie Ma
- Department of Environmental Engineering, Technical University of Denmark , Miljøvej Building 113, 2800 Kongens Lyngby, Denmark
| | - Carlos Domingo-Félez
- Department of Environmental Engineering, Technical University of Denmark , Miljøvej Building 113, 2800 Kongens Lyngby, Denmark
| | - Benedek Gy Plósz
- Department of Environmental Engineering, Technical University of Denmark , Miljøvej Building 113, 2800 Kongens Lyngby, Denmark
| | - Barth F Smets
- Department of Environmental Engineering, Technical University of Denmark , Miljøvej Building 113, 2800 Kongens Lyngby, Denmark
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Pellicer-Nàcher C, Franck S, Gülay A, Ruscalleda M, Terada A, Al-Soud WA, Hansen MA, Sørensen SJ, Smets BF. Sequentially aerated membrane biofilm reactors for autotrophic nitrogen removal: microbial community composition and dynamics. Microb Biotechnol 2013; 7:32-43. [PMID: 24112350 PMCID: PMC3896934 DOI: 10.1111/1751-7915.12079] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2013] [Revised: 06/21/2013] [Accepted: 07/26/2013] [Indexed: 02/01/2023] Open
Abstract
Membrane-aerated biofilm reactors performing autotrophic nitrogen removal can be successfully applied to treat concentrated nitrogen streams. However, their process performance is seriously hampered by the growth of nitrite oxidizing bacteria (NOB). In this work we document how sequential aeration can bring the rapid and long-term suppression of NOB and the onset of the activity of anaerobic ammonium oxidizing bacteria (AnAOB). Real-time quantitative polymerase chain reaction analyses confirmed that such shift in performance was mirrored by a change in population densities, with a very drastic reduction of the NOB Nitrospira and Nitrobacter and a 10-fold increase in AnAOB numbers. The study of biofilm sections with relevant 16S rRNA fluorescent probes revealed strongly stratified biofilm structures fostering aerobic ammonium oxidizing bacteria (AOB) in biofilm areas close to the membrane surface (rich in oxygen) and AnAOB in regions neighbouring the liquid phase. Both communities were separated by a transition region potentially populated by denitrifying heterotrophic bacteria. AOB and AnAOB bacterial groups were more abundant and diverse than NOB, and dominated by the r-strategists Nitrosomonas europaea and Ca. Brocadia anammoxidans, respectively. Taken together, the present work presents tools to better engineer, monitor and control the microbial communities that support robust, sustainable and efficient nitrogen removal.
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Affiliation(s)
- Carles Pellicer-Nàcher
- Department of Environmental Engineering, Technical University of Denmark, Building 113, Miljøvej, 2800, Kgs Lyngby, Denmark
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12
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New methods for analysis of spatial distribution and coaggregation of microbial populations in complex biofilms. Appl Environ Microbiol 2013; 79:5978-87. [PMID: 23892743 DOI: 10.1128/aem.01727-13] [Citation(s) in RCA: 47] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
In biofilms, microbial activities form gradients of substrates and electron acceptors, creating a complex landscape of microhabitats, often resulting in structured localization of the microbial populations present. To understand the dynamic interplay between and within these populations, quantitative measurements and statistical analysis of their localization patterns within the biofilms are necessary, and adequate automated tools for such analyses are needed. We have designed and applied new methods for fluorescence in situ hybridization (FISH) and digital image analysis of directionally dependent (anisotropic) multispecies biofilms. A sequential-FISH approach allowed multiple populations to be detected in a biofilm sample. This was combined with an automated tool for vertical-distribution analysis by generating in silico biofilm slices and the recently developed Inflate algorithm for coaggregation analysis of microbial populations in anisotropic biofilms. As a proof of principle, we show distinct stratification patterns of the ammonia oxidizers Nitrosomonas oligotropha subclusters I and II and the nitrite oxidizer Nitrospira sublineage I in three different types of wastewater biofilms, suggesting niche differentiation between the N. oligotropha subclusters, which could explain their coexistence in the same biofilms. Coaggregation analysis showed that N. oligotropha subcluster II aggregated closer to Nitrospira than did N. oligotropha subcluster I in a pilot plant nitrifying trickling filter (NTF) and a moving-bed biofilm reactor (MBBR), but not in a full-scale NTF, indicating important ecophysiological differences between these phylogenetically closely related subclusters. By using high-resolution quantitative methods applicable to any multispecies biofilm in general, the ecological interactions of these complex ecosystems can be understood in more detail.
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