| 1. |
- Almstrand, Robert, et al.
(författare)
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Dynamics of specific ammonia-oxidizing bacterial populations and nitrification in response to controlled shifts of ammonium concentrations in wastewater
- 2013
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Ingår i: Applied Microbiology and Biotechnology. - : Springer Verlag (Germany). - 0175-7598 .- 1432-0614. ; 97:5, s. 2183-2191
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Tidskriftsartikel (refereegranskat)abstract
- Ammonia-oxidizing bacteria (AOB) are essential for the nitrification process in wastewater treatment. To retain these slow-growing bacteria in wastewater treatment plants (WWTPs), they are often grown as biofilms, e.g., on nitrifying trickling filters (NTFs) or on carriers in moving bed biofilm reactors (MBBRs). On NTFs, a decreasing ammonium gradient is formed because of the AOB activity, resulting in low ammonium concentrations at the bottom and reduced biomass with depth. To optimize the NTF process, different ammonium feed strategies may be designed. This, however, requires knowledge about AOB population dynamics. Using fluorescence in situ hybridization (FISH) and confocal laser scanning microscopy, we followed biomass changes during 6 months, of three AOB populations on biofilm carriers. These were immersed in aerated MBBR tanks in a pilot plant receiving full-scale wastewater. Tanks were arranged in series, forming a wastewater ammonium gradient mimicking an NTF ammonium gradient. The biomass of one of the dominating Nitrosomonas oligotropha-like populations increased after an ammonium upshift, reaching levels comparable to the high ammonium control in 28 days, whereas a Nitrosomonas europaea-like population increased relatively slowly. The MBBR results, together with competition studies in NTF systems fed with wastewater under controlled ammonium regimes, suggest a differentiation between the two N. oligotropha populations, which may be important for WWTP nitrification.
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| 2. |
- Almstrand, Robert, et al.
(författare)
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New methods for analysis of spatial distribution and co-aggregation of microbial populations in complex biofilms.
- 2013
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Ingår i: Applied and Environmental Microbiology. - 0099-2240 .- 1098-5336. ; 79:19, s. 5978-5987
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Tidskriftsartikel (refereegranskat)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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| 3. |
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| 4. |
- Almstrand, Robert, et al.
(författare)
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Three-dimensional stratification of bacterial biofilm populations in a moving bed biofilm reactor for nitritation-anammox.
- 2014
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Ingår i: International Journal of Molecular Sciences. - : MDPI AG. - 1661-6596 .- 1422-0067. ; 15:2, s. 2191-206
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Tidskriftsartikel (refereegranskat)abstract
- Moving bed biofilm reactors (MBBRs) are increasingly used for nitrogen removal with nitritation-anaerobic ammonium oxidation (anammox) processes in wastewater treatment. Carriers provide protected surfaces where ammonia oxidizing bacteria (AOB) and anammox bacteria form complex biofilms. However, the knowledge about the organization of microbial communities in MBBR biofilms is sparse. We used new cryosectioning and imaging methods for fluorescence in situ hybridization (FISH) to study the structure of biofilms retrieved from carriers in a nitritation-anammox MBBR. The dimensions of the carrier compartments and the biofilm cryosections after FISH showed good correlation, indicating little disturbance of biofilm samples by the treatment. FISH showed that Nitrosomonas europaea/eutropha-related cells dominated the AOB and Candidatus Brocadia fulgida-related cells dominated the anammox guild. New carriers were initially colonized by AOB, followed by anammox bacteria proliferating in the deeper biofilm layers, probably in anaerobic microhabitats created by AOB activity. Mature biofilms showed a pronounced three-dimensional stratification where AOB dominated closer to the biofilm-water interface, whereas anammox were dominant deeper into the carrier space and towards the walls. Our results suggest that current mathematical models may be oversimplifying these three-dimensional systems and unless the multidimensionality of these systems is considered, models may result in suboptimal design of MBBR carriers.
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| 5. |
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| 6. |
- Hermansson, Malte, 1954, et al.
(författare)
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Nitrifierande biofilmer för biologisk kväverening i avloppsreningsverk
- 2006
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Biological nitrogen removal is implemented in Swedish wastewater treatment plants, often using biofilm processes for nitrification. Using DNA based methods we analyzed population dynamics and activity of nitrifying biofilms, and have tested different running strategies in a pilot plant with controlled ammonium concentrations.
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| 7. |
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| 8. |
- Lydmark, Pär, 1976, et al.
(författare)
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Vertical distribution of nitrifying populations in bacterial biofilms from a full-scale nitrifying trickling filter
- 2006
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Ingår i: Environmental Microbiology. - : Wiley. - 1462-2912 .- 1462-2920. ; 8:11, s. 2036-2049
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Tidskriftsartikel (refereegranskat)abstract
- Cryosectioned biofilm from three depths (0.5, 3.0 and 6.0 m) in a full-scale nitrifying trickling filter (NTF) were studied using fluorescence in situ hybridization (FISH). A large number of sections were used to determine how the biofilm thickness, structure and community composition varied with depth along the ammonium concentration gradient in the NTF, and how the ammonia-oxidizing bacteria (AOB) and nitrite-oxidizing bacteria (NOB) were distributed vertically within the biofilm. Both the biofilm thickness and relative biomass content of the biofilm decreased with depth, along with structural differences such as void size and surface roughness. Four AOB populations were found, with two Nitrosomonas oligotropha populations dominating at all depths. A smaller population of Nitrosomonas europaea was present only at 0.5 m, while a population of Nitrosomonas communis increased with depth. The two N. oligotropha populations showed different vertical distribution patterns within the biofilm, indicating different ecophysiologies even though they belong to the same AOB lineage. All NOB were identified as Nitrospira sp., and were generally more associated with the biofilm base than the surface-associated dominating AOB population. Additionally, a small population of anaerobic ammonia-oxidizers was found at 6.0 m, even though the biofilm was well aerated.
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| 9. |
- Oquist, M. G., et al.
(författare)
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Nitrous oxide production in a forest soil at low temperatures - processes and environmental controls
- 2004
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Ingår i: Fems Microbiology Ecology. - : Oxford University Press (OUP). - 0168-6496 .- 1574-6941. ; 49:3, s. 371-378
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Tidskriftsartikel (refereegranskat)abstract
- Recent investigations have highlighted the relative importance of the winter season for emissions of N2O from boreal soils. However, our understanding of the processes and environmental controls regulating these emissions is fragmentary. Therefore, we investigated the potential for, and relative importance of, N2O formation at temperatures below 0 degreesC in laboratory experiments involving incubations of a Swedish boreal forest soil. Our results show that frozen soils have a high potential for N2O formation and subsequent emission. Net N2O production rates at -4 degreesC equaled those observed at +10 to +15 degreesC at moisture contents >60% of the soil's water-holding capacity. The source of this N2O was found to be denitrification occurring in anoxic microsites in the frozen soil and temperature per se did not control the denitrification rates at temperatures around 0 degreesC. Furthermore, both net nitrogen-mineralisation and nitrification were observed in the frozen soil samples. Based on these findings we propose a conceptual model for the temperature response of N2O formation in soils at low temperatures. (C) 2004 Federation of European Microbiological Societies. Published by Elsevier B.V. All rights reserved.
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| 10. |
- Persson, Frank, 1970, et al.
(författare)
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One-stage nitritation - anaerobic ammonium oxidation at low temperatures in a moving bed biofilm reactor
- 2013
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Ingår i: 1st International IWA Conference on Holistic Sludge Management. Proceedings. 6–8 May 2013, Västerås, Sweden.
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Konferensbidrag (refereegranskat)abstract
- Bacteria capable of anaerobic ammonium oxidation (anammox) enable autotrophic nitrogen removal. Organic carbon in wastewater can instead be utilized for energy production. However, anammox-based processes are not yet used at any extent for treatment of the main stream at wastewater treatment plants. One of the reasons for this is the challenge for the slow growing autotrophic bacteria to work at low temperatures. Here we investigate one-stage nitritation-anammox at temperatures of 13-16°C in a pilot moving bed biofilm reactor (MBBR) receiving reject water from anaerobic sludge digestion. At a target nitrogen loading rate of 1 g NH4+-N m-2 d-1 the average nitrogen removal rate was 0.81 g NH4+-N m-2 d-1 and 0.55 g NH4+-N m-2 d-1 at 16°C and 13°C respectively. At low temperatures oxygen control is important to avoid oxygen penetration to the deeper parts of the biofilm, which causes inhibition of the anammox bacteria and as a result nitrite accumulation. Hence, the process was operated at conditions to limit the activity of the aerobic ammonium oxidizing bacteria (AOB) by oxygen availability. The biofilm biomass was dominated by anammox bacteria, with 1.0 × 1014 copies m-2 (16S rRNA), with considerably fewer AOB of 2.1 × 1012 copies m-2 (amoA), as measured by quantitative PCR. Cell specific conversion rates of anammox bacteria and AOB were estimated at 0.3-0.5 fmol N cell-1 d-1 and 7-9 fmol N cell-1 d-1, respectively. The study shows the applicability of one-stage nitritation-anammox in MBBRs at low temperatures and highlights the importance of quantification of AOB and anammox bacteria for understanding process performance.
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