| 1. |
- 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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| 2. |
- 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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| 3. |
- Gustavsson, David J.I., et al.
(författare)
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Long-term stability of partial nitritation-anammox for treatment of municipal wastewater in a moving bed biofilm reactor pilot system
- 2020
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Ingår i: Science of the Total Environment. - : Elsevier BV. - 0048-9697 .- 1879-1026. ; 714
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Tidskriftsartikel (refereegranskat)abstract
- © 2019 Nitrogen removal from the mainstream of municipal wastewater with partial nitritation-anammox (PNA) would be highly beneficial with regard to the uses of energy and organic carbon. However, the challenges of process instability, low nitrogen removal rates (NRR) and unwanted aerobic nitrite oxidation need to be solved to reach large-scale implementation. Here, we have operated pilot-scale moving bed biofilm reactors (MBBRs) for mainstream treatment, together with sidestream treatment of sludge liquor from anaerobic digestors, for over 900 days to investigate process stability, reactor performance and microbial community structure at realistic conditions. The MBBR biofilm contained stable and high relative abundances of anammox bacteria (10–32%) consisting of two major Brocadia sp. populations, and several populations of aerobic ammonia-oxidising bacteria (AOB) within Nitrosomonas sp. (0.2–3.1%), as assessed by 16S rDNA amplicon sequencing. In addition, nitrite-oxidising bacteria (NOB) consisting of Nitrospira sp. (0.4–0.8%) and Nitrotoga sp. (up to 0.4%) were present. Nitrogen was removed at a peak rate of 0.66 g N m−2 d−1 (0.13 kg N m−3 d−1) with a nitrate production over ammonium consumption of 15% by the NOB, at operation with continuous aeration at 15 °C. However, during most periods with continuous aeration, the NRR was lower (≈ 0.45 g N m−2 d−1), with larger relative nitrate production (≈40%), presumably due to problems to maintain stable residual ammonium concentrations during wet-weather mainstream flows. Changing reactor operation to intermittent aeration decreased the NRR but did not help in suppressing the NOB. The study shows that with MBBRs, stable mainstream PNA can be attained at realistic NRR, but with need for post-treatment of nitrate, since effective NOB suppression was hard to achieve.
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| 4. |
- Heinicke, G., et al.
(författare)
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The effect of biological pre-filtration on the performance of conventional surface water treatment
- 2006
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Ingår i: Journal of Water Supply: Research and Technology - Aqua. - 0003-7214. ; 55:2, s. 109-119
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Tidskriftsartikel (refereegranskat)abstract
- Many waterworks that apply conventional treatment of surface water, by flocculation and filtration, have to deal with seasonal changes of the raw water quality, increasing concentrations of natural organic matter (NOM), and the necessity to improve particle removal. A pilot plant was operated to closely resemble the full-scale treatment at a surface water treatment plant in Göteborg, Sweden. Treatment consisted of flocculation, sedimentation and rapid granular activated carbon (GAC) filtration. To assess the effects of biological pre-filtration, the feed water to the pilot plant was switched weekly between surface water and biofiltered water which had passed through adsorptively exhausted GAC at an empty bed contact time (EBCT) of 34 minutes. The processes were investigated with regard to NOM, the bacterial re-growth potential, as well as their function as a barrier for suspended particles that originate from the raw water. Biological pre-filtration improved particle removal and made it less dependent on the post-sedimentation GAC rapid filter, thereby improving robustness. Episodically elevated concentrations of earthy-musty odour compounds, which are not reliably removed by flocculation and filtration, were reduced by the biofilters. The process combination may be of particular interest for waterworks with variable raw water quality.
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| 5. |
- Kämpfer, P, et al.
(författare)
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Undibacterium pigrum gen. nov., sp. nov., isolated from drinking water
- 2007
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Ingår i: International Journal of Systematic and Evolutionary Microbiology. - : Microbiology Society. - 1466-5026 .- 1466-5034. ; 57:7, s. 1510-1515
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Tidskriftsartikel (refereegranskat)abstract
- Two Gram-negative, rod-shaped, oxidase-positive, non-spore-forming, non-motile bacteria (strains CCUG 49009T and CCUG 49012), both isolated from drinking water, were characterized. On the basis of chemotaxonomic data [major ubiquinone, Q-8; predominant polyamines, putrescine and 2-hydroxyputrescine; major polar lipids, phosphatidylethanolamine, moderate amounts of diphosphatidylglycerol and phosphatidylglycerol and minor amounts of three aminolipids and phosphatidylserine; major fatty acids, C16 : 0 and summed feature 3 (C16 : 1ω7c/C15 : 0 iso 2-OH)] and 16S rRNA gene sequence similarities, both strains clearly belong to the family Oxalobacteraceae of the Betaproteobacteria. 16S rRNA gene sequence similarities with members of the most closely related genera of this group (Herminiimonas, Massilia, Duganella, Telluria, Herbaspirillum, Janthinobacterium, Naxibacter and Paucimonas) were less than 96.5 % for both strains. The two strains also shared a relatively low 16S rRNA gene sequence similarity (96.8 %). Although phylogenetic analysis based on 16S rRNA gene sequence similarities clearly showed that the two organisms formed a separate branch, their phenotypes (including chemotaxonomic features) were hardly distinguishable and showed high similarities to those reported for the most closely related genera. On the basis of DNA–DNA hybridization results, the two strains were shown to represent separate species (sharing only 20 % DNA–DNA relatedness), but they could not be clearly differentiated phenotypically from each other. It is evident that these organisms represent a new genus, Undibacterium gen. nov., with one species, Undibacterium pigrum sp. nov. The type strain of Undibacterium pigrum is strain CCUG 49009T (=CIP 109318T). Strain CCUG 49012 (=CIP 108976) probably represents a second species of this genus, but is described here as a second genomovar of this species because of the lack of differentiating characters.
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| 6. |
- Liebana, Raquel, 1986, et al.
(författare)
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Combined Deterministic and Stochastic Processes Control Microbial Succession in Replicate Granular Biofilm Reactors
- 2019
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Ingår i: Environmental Science & Technology. - : American Chemical Society (ACS). - 0013-936X .- 1520-5851. ; 53:9, s. 4912-4921
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Tidskriftsartikel (refereegranskat)abstract
- Granular sludge is an efficient and compact biofilm process for wastewater treatment. However, the ecological factors involved in microbial community assembly during the granular biofilm formation are poorly understood, and little is known about the reproducibility of the process. Here, three replicate bioreactors were used to investigate microbial succession during the formation of granular biofilms. We identified three successional phases. During the initial phase, the successional turnover was high and alpha-diversity decreased as a result of the selection of taxa adapted to grow on acetate and form aggregates. Despite these dynamic changes, the microbial communities in the replicate reactors were similar. The second successional phase occurred when the settling time was rapidly decreased to selectively retain granules in the reactors. The influence of stochasticity on succession increased and new niches were created as granules emerged, resulting in temporarily increased alpha-diversity. The third successional phase occurred when the settling time was kept stable and granules dominated the biomass. Turnover was low, and selection resulted in the same abundant taxa in the reactors, but drift, which mostly affected low-abundant community members, caused the community in one reactor to diverge from the other two. Even so, performance was stable and similar between reactors.
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| 7. |
- Liebana, Raquel, 1986, et al.
(författare)
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Resistance of aerobic granular sludge microbiomes to periodic loss of biomass
- 2023
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Ingår i: Biofilm. - 2590-2075. ; 6
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Tidskriftsartikel (refereegranskat)abstract
- Granular sludge is a biofilm process used for wastewater treatment which is currently being implemented worldwide. It is important to understand how disturbances affect the microbial community and performance of reactors. Here, two acetate-fed replicate reactors were inoculated with acclimatized sludge and the reactor performance, and the granular sludge microbial community succession were studied for 149 days. During this time, the microbial community was challenged by periodically removing half of the reactor biomass, subsequently increasing the food-to-microorganism (F/M) ratio. Diversity analysis together with null models show that overall, the microbial communities were resistant to the disturbances, observing some minor effects on polyphosphate-accumulating and denitrifying microbial communities and their associated reactor functions. Community turnover was driven by drift and random granule loss, and stochasticity was the governing ecological process for community assembly. These results evidence the aerobic granular sludge process as a robust system for wastewater treatment.
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| 8. |
- Modin, Oskar, 1980, et al.
(författare)
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Hill-based dissimilarity indices and null models for analysis of microbial community assembly
- 2020
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Ingår i: Microbiome. - : Springer Science and Business Media LLC. - 2049-2618. ; 8:1
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Tidskriftsartikel (refereegranskat)abstract
- BackgroundHigh-throughput amplicon sequencing of marker genes, such as the 16S rRNA gene in Bacteria and Archaea, provides a wealth of information about the composition of microbial communities. To quantify differences between samples and draw conclusions about factors affecting community assembly, dissimilarity indices are typically used. However, results are subject to several biases, and data interpretation can be challenging. The Jaccard and Bray-Curtis indices, which are often used to quantify taxonomic dissimilarity, are not necessarily the most logical choices. Instead, we argue that Hill-based indices, which make it possible to systematically investigate the impact of relative abundance on dissimilarity, should be used for robust analysis of data. In combination with a null model, mechanisms of microbial community assembly can be analyzed. Here, we also introduce a new software, qdiv, which enables rapid calculations of Hill-based dissimilarity indices in combination with null models.ResultsUsing amplicon sequencing data from two experimental systems, aerobic granular sludge (AGS) reactors and microbial fuel cells (MFC), we show that the choice of dissimilarity index can have considerable impact on results and conclusions. High dissimilarity between replicates because of random sampling effects make incidence-based indices less suited for identifying differences between groups of samples. Determining a consensus table based on count tables generated with different bioinformatic pipelines reduced the number of low-abundant, potentially spurious amplicon sequence variants (ASVs) in the data sets, which led to lower dissimilarity between replicates. Analysis with a combination of Hill-based indices and a null model allowed us to show that different ecological mechanisms acted on different fractions of the microbial communities in the experimental systems.ConclusionsHill-based indices provide a rational framework for analysis of dissimilarity between microbial community samples. In combination with a null model, the effects of deterministic and stochastic community assembly factors on taxa of different relative abundances can be systematically investigated. Calculations of Hill-based dissimilarity indices in combination with a null model can be done in qdiv, which is freely available as a Python package (https://github.com/omvatten/qdiv). In qdiv, a consensus table can also be determined from several count tables generated with different bioinformatic pipelines.
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| 9. |
- Modin, Oskar, 1980, et al.
(författare)
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Nonoxidative removal of organics in the activated sludge process
- 2016
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Ingår i: Critical Reviews in Environmental Science and Technology. - : Informa UK Limited. - 1064-3389 .- 1547-6537. ; 46:7, s. 635-672
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Tidskriftsartikel (refereegranskat)abstract
- The activated sludge process is commonly used to treat wastewater by aerobic oxidation of organic pollutants into carbon dioxide and water. However, several nonoxidative mechanisms can also contribute to removal of organics. Sorption onto activated sludge can remove a large fraction of the colloidal and particulate wastewater organics. Intracellular storage of, e.g., polyhydroxyalkanoates (PHA), triacylglycerides (TAG), or wax esters can convert wastewater organics into precursors for high-value products. Recently, several environmental, economic, and technological drivers have stimulated research on nonoxidative removal of organics for wastewater treatment. In this paper, we review these nonoxidative removal mechanisms as well as the existing and emerging process configurations that make use of them for wastewater treatment. Better utilization of nonoxidative processes in activated sludge could reduce the wasteful aerobic oxidation of organic compounds and lead to more resource-efficient wastewater treatment plants.
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| 10. |
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