| 1. |
- Wilen, Britt-Marie, 1966, et al.
(författare)
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The mechanisms of granulation of activated sludge in wastewater treatment, its optimization, and impact on effluent quality
- 2018
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Ingår i: Applied Microbiology and Biotechnology. - : Springer Science and Business Media LLC. - 0175-7598 .- 1432-0614. ; 102:12, s. 5005-5020
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Tidskriftsartikel (refereegranskat)abstract
- Granular activated sludge has gained increasing interest due to its potential in treating wastewater in a compact and efficient way. It is well-established that activated sludge can form granules under certain environmental conditions such as batch-wise operation with feast-famine feeding, high hydrodynamic shear forces, and short settling time which select for dense microbial aggregates. Aerobic granules with stable structure and functionality have been obtained with a range of different wastewaters seeded with different sources of sludge at different operational conditions, but the microbial communities developed differed substantially. In spite of this, granule instability occurs. In this review, the available literature on the mechanisms involved in granulation and how it affects the effluent quality is assessed with special attention given to the microbial interactions involved. To be able to optimize the process further, more knowledge is needed regarding the influence of microbial communities and their metabolism on granule stability and functionality. Studies performed at conditions similar to full-scale such as fluctuation in organic loading rate, hydrodynamic conditions, temperature, incoming particles, and feed water microorganisms need further investigations.
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| 2. |
- 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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| 3. |
- Fredriksson, Johan, 1979, et al.
(författare)
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Long-term dynamics of the bacterial community in a Swedish full-scale wastewater treatment plant
- 2019
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Ingår i: Environmental Technology. - : Informa UK Limited. - 0959-3330 .- 1479-487X. ; 40:7, s. 912-928
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Tidskriftsartikel (refereegranskat)abstract
- The operational efficiency of activated sludge wastewater treatment plants depends to a large extent on the microbial community structure of the activated sludge. The aims of this paper are to describe the composition of the bacterial community in a Swedish full-scale activated sludge wastewater treatment plant, to describe the dynamics of the community and to elucidate possible causes for bacterial community composition changes. The bacterial community composition in the activated sludge was described using 16S rRNA gene libraries and monitored for 15 months by a terminal restriction fragment (T-RF) length polymorphism (T-RFLP) analysis of the 16S rRNA gene. Despite variable environmental conditions, a large fraction of the observed T-RFs were present at all times, making up at least 50% in all samples, possibly representing a relatively stable core fraction of the bacterial community. However, the proportions of the different T-RFs in this fraction as well as the T-RFs in the more variable fraction showed a significant variation over time and temperature. The difference in community composition between summer and winter coincided with observed differences in floc structure. These observations suggest a relationship between floc properties and bacterial community composition, although additional experiments are required to determine causality.
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| 4. |
- Wilen, Britt-Marie, 1966, et al.
(författare)
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Influence of flocculation and settling properties of activated sludge in relation to secondary settler performance
- 2006
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Ingår i: Water Science and Technology. - : IWA Publishing. - 0273-1223 .- 1996-9732. ; 54:1, s. 147-155
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Tidskriftsartikel (refereegranskat)abstract
- Floc characteristics were studied at a full scale activated sludge treatment plant with a unique process solution incorporating pre-denitrification with post-nitrification in nitrifying trickling filters. Since greater nitrogen removal is achieved when more secondary settled wastewater is recirculated to the trickling filters, the secondary settlers are always operated close to their maximal capacity. The flocculation and settling properties are therefore crucial and have an effect on the overall plant performance. Since the plant is operated at a short sludge age, these properties change quickly, resulting in variable maximal secondary settler capacity. The dynamics in floc structure and microbial community composition were studied and correlated to the secondary settler performance. Fluorescence in situ hybridisation was used to investigate the microbial community structure and their spatial distribution. The floc structure could to some extent be related to the flocculation and settling properties of the sludge. Even small differences had an influence suggesting that colloidal properties also play a significant role in determining the floc properties. No correlation between microbial community composition and settling properties could be established with the group-specific probes investigated.
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| 5. |
- 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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| 6. |
- Wilen, Britt-Marie, 1966, et al.
(författare)
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Microbial community structure in activated sludge floc analysed by fluorescence in situ hybridization and its relation to floc stability
- 2008
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Ingår i: Water Research. - : Elsevier BV. - 0043-1354 .- 1879-2448. ; 42:8-9, s. 2300-2308
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Tidskriftsartikel (refereegranskat)abstract
- The efficiency of activated sludge treatment plants is dependent on the solid–liquid separation properties of the activated sludge. A critical parameter is the stability of the microbial flocs. Weak flocs deflocculate easily leaving increased concentrations of suspended solids in the effluent. The knowledge about how different bacteria are attached to the flocs and their influence on the bioflocculation is limited. In this study, the deflocculation of different phylogenetic groups of bacteria in activated sludge from a full scale plant was investigated. The experiments were carried out by using a shear method where the sludge flocs are deflocculated under controlled shear conditions. The degree of deflocculation was measured as increase in turbidity of the supernatant. Identification and quantification of the microbial community structure of both total activated sludge and deflocculated bacteria were conducted with group-specific gene probes for broad groups of bacteria (Alphaproteobacteria, Betaproteobacteria, Gammaproteobacteria and Actinobacteria) and fluorescence in situ hybridization (FISH). The microbial community structure of the deflocculated bacteria was different compared to the total activated sludge with a higher abundance of Gammaproteobacteria in the supernatant indicating that different groups of bacteria are bound with different strength to the floc surface. The results show that the bacteria in the outer parts of the flocs are relatively loosely bound to the floc matrix and can be easily eroded from the surface when exposed to shear.
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| 7. |
- 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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| 8. |
- Persson, Frank, 1970, et al.
(författare)
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Community structure of partial nitritation-anammox biofilms at decreasing substrate concentrations and low temperature
- 2017
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Ingår i: Microbial Biotechnology. - : Wiley. - 1751-7907 .- 1751-7915. ; 10:4, s. 761-772
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Tidskriftsartikel (refereegranskat)abstract
- Partial nitritation-anammox (PNA) permits energy effective nitrogen removal. Today PNA is used for treatment of concentrated and warm side streams at wastewater treatment plants, but not the more diluted and colder main stream. To implement PNA in the main stream, better knowledge about microbial communities at the typical environmental conditions is necessary. In order to investigate the response of PNA microbial communities to decreasing substrate availability, we have operated a moving bed biofilm reactor (MBBR) at decreasing reactor concentrations (311–27 mg-N l−1 of ammonium) and low temperature (13°C) for 302 days and investigated the biofilm community using high throughput amplicon sequencing; quantitative PCR; and fluorescence in situ hybridization. The anammox bacteria (Ca. Brocadia) constituted a large fraction of the biomass with fewer aerobic ammonia oxidizing bacteria (AOB) and even less nitrite oxidizing bacteria (NOB; Nitrotoga, Nitrospira and Nitrobacter). Still, NOB had considerable impact on the process performance. The anammox bacteria, AOB and NOB all harboured more than one population, indicating some diversity, and the heterotrophic bacterial community was diverse (seven phyla). Despite the downshifts in substrate availability, changes in the relative abundance and composition of anammox bacteria, AOB and NOB were small and also the heterotrophic community showed little changes in composition. This indicates stability of PNA MBBR communities towards decreasing substrate availability and suggests that even heterotrophic bacteria are integral components of these communities.
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| 9. |
- Persson, Frank, 1970, et al.
(författare)
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Structure and composition of biofilm communities in a moving bed biofilm reactor for nitritation-anammox at low temperatures
- 2014
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Ingår i: Bioresource Technology. - : Elsevier BV. - 0960-8524 .- 1873-2976. ; 154, s. 267-273
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Tidskriftsartikel (refereegranskat)abstract
- It is a challenge to apply anaerobic ammonium oxidation (anammox) for nitrogen removal from wastewater at low temperatures. Maintenance of anammox- and aerobic ammonia oxidizing bacteria (AOB) and suppression of nitrite oxidizing bacteria (NOB) are key issues. In this work, a nitritation-anammox moving bed biofilm pilot reactor was operated at 19-10°C for 300d. Nitrogen removal was decreasing, but stable, at 19-13°C. At 10°C removal became unstable. Quantitative PCR, fluorescence in situ hybridization and gene sequencing showed that no major microbial community changes were observed with decreased temperature. Anammox bacteria dominated the biofilm (0.9-1.2×1014 16S rRNA copies m-2). Most anammox bacteria were similar to Brocadia sp. 40, but another smaller Brocadia population was present near the biofilm-water interface, where also the AOB community (Nitrosomonas) was concentrated in thin layers (1.8-5.3×1012 amoA copies m-2). NOB (Nitrobacter, Nitrospira) were always present at low concentrations (<1.3×1011 16S rRNA copies m-2).
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| 10. |
- Piculell, Maria, et al.
(författare)
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The inhibitory effects of reject water on nitrifying populations grown at different biofilm thickness
- 2016
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Ingår i: Water Research. - : Elsevier BV. - 0043-1354 .- 1879-2448. ; 104:1 Nov, s. 292-302
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Tidskriftsartikel (refereegranskat)abstract
- Suppression of nitrite oxidizing bacteria (NOB) is of vital importance to achieve successful, energy efficient, mainstream anammox processes for wastewater treatment. In this study, biofilm carriers from a fully nitrifying MBBR system, fed with mainstream wastewater, were temporarily exposed to reject water from sludge dewatering, to evaluate this as a possible strategy to inhibit NOB and achieve nitrite production under realistic conditions. Two different carrier types were compared, in which biofilm thickness was maintained at approximately 400 and 50 mm, respectively, and reject treatment was tested at different exposure time and loading rates. Reject exposure almost always resulted in an increased nitrite production in the thinner biofilm, and overall, nitrifiers growing in the thin biofilm were more sensitive than those grown in the thicker biofilm. The effect from reject exposure remained in the systems for four days after returning to mainstream operation, with nitrite production gradually increasing for three days. Increased concentrations of free ammonia correlated with reject exposure and may be the cause of inhibition, although other factors cannot be excluded.
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