| 1. |
- Cimbritz, Michael, et al.
(author)
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PAC dosing to an MBBR – Effects on adsorption of micropollutants, nitrification and microbial community
- 2019
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In: Science of the Total Environment. - : Elsevier BV. - 0048-9697 .- 1879-1026. ; 677, s. 571-579
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Journal article (peer-reviewed)abstract
- Two nitrifying MBBR reactors were operated in parallel, one with PAC dosing and one without, to determine the effects of PAC dosing on nitrification and micropollutant adsorption in municipal wastewater. The removal of micropollutants was evaluated for several doses of PAC and batch experiments were performed to measure adsorption kinetics and nitrification rates. The influence of PAC on the nitrifying microbial community was examined by high-throughput amplicon sequencing. Long-term operation of the pilot reactors showed that nitrification could be maintained while supplying PAC at increasing doses, as confirmed by high nitrification rates and significant abundance of nitrifying bacteria. The adsorption of organic micropollutants could be controlled by the PAC dose, and increased dosing resulted in corresponding improvements in removal efficiency. Biomass, suspended or attached to carriers, did not interfere with the adsorption of organic micropollutants. Freundlich isotherms obtained from the batch experiments were used to predict removal of organic micropollutants in the pilot reactors, suggesting that batch adsorption experiments can be used to predict micropollutant removal on a full scale. Collectively, the results show that nitrification and adsorption of organic micropollutants can be performed simultaneously in an MBBR.
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| 2. |
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| 3. |
- Karacic, Sabina, 1987, et al.
(author)
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Biodeterioration of reinforced sprayed concrete in subsea tunnels (peer-reviewed)
- 2018
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In: Proceedings pro123-1 : Final Conference of RILEM TC 253-MCI: Microorganisms-Cementitious Materials Interactions. - 9782351582077 ; 1:PRO 123, s. 209-221
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Conference paper (peer-reviewed)abstract
- Progressive microbial deterioration of steel fibre reinforced sprayed concrete for rock support has been observed in the Norwegian Oslofjord subsea tunnel due to reddish/brown and black biofilms. The concrete mix design corresponded to B45 and M45, with water/binder ratio = 0.42. Previous research on the microbial community has revealed complexity of the microbial composition involved in degradation of the cement paste matrix, material loss and steel fibre corrosion. In this study, we analysed microbial community dynamics and concrete degradation over time, biominerals and water chemistry composition to understand most important mechanisms involved in the biodeterioration process. Results showed temporal variations of microbial community and concrete degradation in association with changes in the water flow. The dataset from 2011 revealed a biofilm bacterial community dominated by Marinicella sp. (Proteobacteria) with a few ammonia oxidisers within Nitrosomonas and nitrite oxidisers within Nitrospinaceae. The data from 2015-2016 showed that the major phylum groups detected were Proteobacteria, Thaumarchaeota, Planctomycetes, Bacteroidetes, Actinobacteria, Acidobacteria, Nitrospirae, and Gemmatimonadetes with relative sequence abundance >2%.
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| 4. |
- Karacic, Sabina, 1987, et al.
(author)
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Microbial attack on subsea sprayed concrete
- 2016
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In: International RILEM Conference on Microorganisms-Cementitious Materials Interactions. - 9782351581605 ; , s. 63-75
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Conference paper (peer-reviewed)abstract
- A novel deterioration process has recently been discovered in several Norwegian subsea tunnels resulting in degradation of the sprayed concrete matrix and destructive corrosion of steel fibers in association with biofilms rich in Mn(IV), Fe(III) and exopolymers. Microbial processes together with abiotic attack from saline ground water, containing high concentrations of Cl−, SO42−, Mg2+ and HCO3 −, are assumed to be responsible for the degradation. In this initial study of the biofilm microbial communities, high throughput amplicon sequencing of 16S rRNA genes was used to survey the biofilm composition and diversity. Results showed a high abundance of iron oxidizing bacteria within Mariprofundus, which was in accordance with the observed accumulation of Fe(III) and exopolymers in the biofilms. Also iron and manganese reducing bacteria were detected. Surprisingly, the biofilm harbored autotrophic nitrogen converting microorganisms at high relative abundances, while no known manganese oxidizingor sulfur reducing bacteria were detected. Furthermore, a number of the numerically important contributors in the biofilm communities could not be assigned to any function. Apparently, the biofilm transformations were more complex than initially anticipated and the role of for instance the nitrogen converting- and the undetermined bacteria for the degradation processes remains unsolved.
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| 5. |
- Karacic, Sabina, 1987, et al.
(author)
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Subsea tunnel reinforced sprayed concrete subjected to deterioration harbours distinct microbial communities
- 2018
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In: Biofouling. - : Informa UK Limited. - 0892-7014 .- 1029-2454. ; 34:10, s. 1161-1174
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Journal article (peer-reviewed)abstract
- Deterioration of concrete is a large societal cost. In the Oslofjord subsea tunnel (Norway), deterioration of sprayed concrete and corrosion of reinforcing steel fibres occur under biofilm formed at sites with intrusion of saline groundwater. In this study, the microbial community structure, in situ environmental gradients and chemical composition of the biofilms were examined at three tunnel sites. Ammonia- and nitrite-oxidising microorganisms, in particular Nitrosopumilus sp., and iron-oxidising bacteria within Mariprofundus sp., were omnipresent, together with a diversity of presumably heterotrophic bacteria. Alpha- and beta diversity measures showed significant differences in richness and community structure between the sites as well as over time and null-models suggested that deterministic factors were important for the community assembly. The superficial flow of water over the biofilm had a strong effect on oxygen penetration in the biofilm and was identified as one major environmental gradient that varied between the sites, likely being important for shaping the microbial communities. © 2019, © 2019 The Author(s). Published by Informa UK Limited, trading as Taylor & Francis Group.
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| 6. |
- Liebana, Raquel, 1986, et al.
(author)
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Combined Deterministic and Stochastic Processes Control Microbial Succession in Replicate Granular Biofilm Reactors
- 2019
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In: Environmental Science & Technology. - : American Chemical Society (ACS). - 0013-936X .- 1520-5851. ; 53:9, s. 4912-4921
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Journal article (peer-reviewed)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.
(author)
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Integration of aerobic granular sludge and membrane bioreactor for wastewater treatment
- 2018
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In: Critical Reviews in Biotechnology. - : Informa UK Limited. - 0738-8551 .- 1549-7801. ; 38:6, s. 801-816
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Research review (peer-reviewed)abstract
- Environmental deterioration together with the need for water reuse and the increasingly restrictive legislation of water quality standards have led to a demand for compact, efficient and less energy consuming technologies for wastewater treatment. Aerobic granular sludge and membrane bioreactors (MBRs) are two technologies with several advantages, such as small footprint, high-microbial density and activity, ability to operate at high organic- and nitrogen-loading rates, and tolerance to toxicity. However, they also have some disadvantages. The aerobic granular sludge process generally requires post-treatment in order to fulfill effluent standards and MBRs suffer from fouling of the membranes. Integrating the two technologies could be a way of combining the advantages and addressing the main problems associated with both processes. The use of membranes to separate the aerobic granules from the treated water would ensure high-quality effluents suitable for reuse. Moreover, the use of granular sludge in MBRs has been shown to reduce fouling. Several recent studies have shown that the aerobic granular membrane bioreactor (AGMBR) is a promising hybrid process with many attractive features. However, major challenges that have to be addressed include how to achieve granulation and maintain granular stability during continuous operation of reactors. This paper aims to review the current state of research on AGMBR technology while drawing attention to relevant findings and highlight current limitations.
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| 8. |
- Liebana, Raquel, 1986, et al.
(author)
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Stability of nitrifying granules exposed to water flux through a coarse pore mesh.
- 2015
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Conference paper (other academic/artistic)abstract
- The study of the strength and stability of aerobic granules is essential for the application of aerobic granular sludge membrane bioreactors (AGMBR). In this study, a coarse pore nylon mesh membrane was used to study the differences in compressibility and breakage of 78 aerobic granules submitted to different water fluxes. Confocal laser scanning microscopy was employed to investigate the distribution of extracellular polymeric substances of cryosectioned granules. The tested granules were able to withstand fluxes much higher than those typically applied in MBRs, with pressures ranging from 0.2 to 4.5 kN m-2 before breakage. Cells, β-polysaccharides and proteins were present in higher abundance in the outer layers, while calcium ions were abundant in the outer- as well as the inner layers of the granule. The results shows that the use of coarse pore meshes operated at very high flux is a feasible technique for biomass separation in AGMBR.
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| 9. |
- Modin, Oskar, 1980, et al.
(author)
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Nonoxidative removal of organics in the activated sludge process
- 2016
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In: Critical Reviews in Environmental Science and Technology. - : Informa UK Limited. - 1064-3389 .- 1547-6537. ; 46:7, s. 635-672
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Journal article (peer-reviewed)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. |
- Modin, Oskar, 1980, et al.
(author)
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Sorption and Release of Organics by Primary, Anaerobic, and Aerobic Activated Sludge Mixed with Raw Municipal Wastewater
- 2015
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In: PLoS ONE. - : Public Library of Science (PLoS). - 1932-6203 .- 1932-6203. ; 10:3, s. e0119371-
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Journal article (peer-reviewed)abstract
- New activated sludge processes that utilize sorption as a major mechanism for organics removal are being developed to maximize energy recovery from wastewater organics, or as enhanced primary treatment technologies. To model and optimize sorption-based activated sludge processes, further knowledge about sorption of organics onto sludge is needed. This study compared primary-, anaerobic-, and aerobic activated sludge as sorbents, determined sorption capacity and kinetics, and investigated some characteristics of the organics being sorbed. Batch sorption assays were carried out without aeration at a mixing velocity of 200 rpm. Only aerobic activated sludge showed net sorption of organics. Sorption of dissolved organics occurred by a near-instantaneous sorption event followed by a slower process that obeyed 1st order kinetics. Sorption of particulates also followed 1st order kinetics but there was no instantaneous sorption event; instead there was a release of particles upon mixing. The 5-min sorption capacity of activated sludge was 6.5±10.8 mg total organic carbon (TOC) per g volatile suspend solids (VSS) for particulate organics and 5.0±4.7 mgTOC/gVSS for dissolved organics. The observed instantaneous sorption appeared to be mainly due to organics larger than 20 kDa in size being sorbed, although molecules with a size of about 200 Da with strong UV absorbance at 215–230 nm were also rapidly removed.
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