Multi-Scale Individual-Based Model of Microbial and Bioconversion Dynamics in Aerobic Granular Sludge

Xavier, João B.; Kreuk, Merle de; Picioreanu, Cristian; Loosdrecht, M.C.M. van

doi:10.1021/es070264m

Cited by 143 publications

(103 citation statements)

References 31 publications

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“…This indicated that the granules were unstable. However, this was inconsistent with the previous studies finding that glucose-fed aerobic granular sludge had a compact shape under a higher organic loading (15 kg COD/(m 3 ·d)), with the same MLSS as for R3 [26]. This was likely due to the organic loading threshold for the instability of aerobic granules depending on the varieties of substrates [27].…”

Section: The Stability Of Aerobic Granular Sludgecontrasting

confidence: 79%

Effects of the Food-to-Microorganism (F/M) Ratio on N2O Emissions in Aerobic Granular Sludge Sequencing Batch Airlift Reactors

Guo

Zhang

Xie

et al. 2017

Water

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The present study investigated the effect of the food-to-microorganism (F/M) ratio on nitrous oxide (N 2 O) emissions in aerobic granular sludge sequencing batch airlift reactors. Three identical sequencing batch airlift reactors were fed with sodium acetate-based wastewater at different chemical oxygen demand (COD) concentrations, resulting in F/M ratios from 0.2 to 0.67 g COD/g SS. The results indicated that N 2 O emissions increased with an increase of the F/M ratio. N 2 O emissions at the high F/M ratio of 0.67 g COD/g SS were the highest (4.4 ± 0.94 mg/d). The main source of the high N 2 O emissions at the F/M ratio of 0.67 g COD/g SS was nitrifier denitrification, rather than heterotrophic denitrification, confirmed by the qPCR (quantitative real-time PCR) results. The heterotrophic denitrification was destroyed by the DO (dissolved oxygen) diffusing into the sludge particles with porous structures. This study offers theoretical support to study the N 2 O emissions in aerobic granular sludge, and can provide guidance for conducting risk assessment and enhancing our ability to predict N 2 O production in aerobic granular sludge at different F/M ratios.

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Section: The Stability Of Aerobic Granular Sludgecontrasting

confidence: 79%

Effects of the Food-to-Microorganism (F/M) Ratio on N2O Emissions in Aerobic Granular Sludge Sequencing Batch Airlift Reactors

Guo

Zhang

Xie

et al. 2017

Water

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show abstract

“…The underlying assumptions are described and justified in detail elsewhere (40,(43)(44)(45), and empirical tests have demonstrated the framework's ability to make accurate predictions for real biological systems (46,47).…”

Section: Resultsmentioning

confidence: 99%

Social evolution in multispecies biofilms

Mitri

Xavier

Foster

2011

Proc. Natl. Acad. Sci. U.S.A.

216

245

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Microbial ecology is revealing the vast diversity of strains and species that coexist in many environments, ranging from free-living communities to the symbionts that compose the human microbiome. In parallel, there is growing evidence of the importance of cooperative phenotypes for the growth and behavior of microbial groups. Here we ask: How does the presence of multiple species affect the evolution of cooperative secretions? We use a computer simulation of spatially structured cellular groups that captures key features of their biology and physical environment. When nutrient competition is strong, we find that the addition of new species can inhibit cooperation by eradicating secreting strains before they can become established. When nutrients are abundant and many species mix in one environment, however, our model predicts that secretor strains of any one species will be surrounded by other species. This "social insulation" protects secretors from competition with nonsecretors of the same species and can improve the prospects of within-species cooperation. We also observe constraints on the evolution of mutualistic interactions among species, because it is difficult to find conditions that simultaneously favor both withinand among-species cooperation. Although relatively simple, our model reveals the richness of interactions between the ecology and social evolution of multispecies microbial groups, which can be critical for the evolution of cooperation.mutualism | microbe | spatial organization | extracellular secretion | interspecies

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“…These phenomena particularly redefine the oxic-anoxic zones within granules which are important for simultaneous nitrogen and phosphorus removal. Although computationally demanding (37) and challenging from the standpoint of experimentally measuring all relevant parameters, these models should allow the virtual engineering of granules, which would without a doubt be a fascinating achievement.…”

Section: Discussionmentioning

confidence: 99%

Aerobic Granules: Microbial Landscape and Architecture, Stages, and Practical Implications

Gonzalez-Gil

Holliger

2014

Appl Environ Microbiol

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For the successful application of aerobic granules in wastewater treatment, granules containing an appropriate microbial assembly able to remove contaminants should be retained and propagated within the reactor. To manipulate and/or optimize this process, a good understanding of the formation and dynamic architecture of the granules is desirable. Models of granules often assume a spherical shape with an outer layer and an inner core, but limited information is available regarding the extent of deviations from such assumptions. We report on new imaging approaches to gain detailed insights into the structural characteristics of aerobic granules. Our approach stained all components of the granule to obtain a high quality contrast in the images; hence limitations due to thresholding in the image analysis were overcome. A three-dimensional reconstruction of the granular structure was obtained that revealed the mesoscopic impression of the cavernlike interior of the structure, showing channels and dead-end paths in detail. In "old" granules, large cavities allowed for the irrigation and growth of dense microbial colonies along the path of the channels. Hence, in some areas, paradoxically higher biomass content was observed in the inner part of the granule compared to the outer part. Microbial clusters "rooting" from the interior of the mature granule structure indicate that granules mainly grow via biomass outgrowth and not by aggregation of small particles. We identify and discuss phenomena contributing to the life cycle of aerobic granules. With our approach, volumetric tetrahedral grids are generated that may be used to validate complex models of granule formation. G ranules are compact, quasispherical aggregates formed by self-immobilized, mixed microbial communities embedded in a matrix of extracellular bio-polymeric substances (1). The phenomenon of granule formation in wastewater treatment systems was first described in anaerobic bioreactors (2, 3). The technological success of anaerobic granules in the treatment of highly concentrated industrial wastewaters (4) has been crucial to stimulating research in developing their aerobic counterparts. Previous studies have shown that in sequencing batch reactors and under certain operational conditions, which include high shear stress and short settling times (5), activated sludge can form aerobic granules (5, 6). Compared to flocs, granules can accommodate five times the biomass concentration (7) and settle 10 times faster (8, 9), and these characteristics translate into small-footprint wastewater treatment plants. Therefore, the use of aerobic granular sludge-based systems stands as a promising alternative technology to conventional activated sludge treatment systems (10). To guarantee the successful application of the aerobic granular sludge technology, granules should be physically stable and should contain an appropriate microbial assembly able to remove the desired contaminants. Moreover, in the long term, this assembly should be retained and should propagate wit...

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Multi-Scale Individual-Based Model of Microbial and Bioconversion Dynamics in Aerobic Granular Sludge

Cited by 143 publications

References 31 publications

Effects of the Food-to-Microorganism (F/M) Ratio on N2O Emissions in Aerobic Granular Sludge Sequencing Batch Airlift Reactors

Effects of the Food-to-Microorganism (F/M) Ratio on N2O Emissions in Aerobic Granular Sludge Sequencing Batch Airlift Reactors

Social evolution in multispecies biofilms

Aerobic Granules: Microbial Landscape and Architecture, Stages, and Practical Implications

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