Microbial population dynamics during aerobic sludge granulation at different organic loading rates

Li, An-jie; Yang, Shu-Fang; Li, Xiaoyan; Gu, Ji‐Dong

doi:10.1016/j.watres.2008.05.005

Cited by 233 publications

(110 citation statements)

References 23 publications

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“…The subsequent impact of biomass loss is deteriorated nitrogen removal efficiency. Rapid changes in the microbial population have also been documented during start-up [17,18]; however, very few studies have examined the abundance and dynamics of the nitrifying community during granulation [19]. Based on a modeling approach, Su et al [20] suggested that a stepwise decrease of settling time can be an effective method for optimizing biomass discharge during start-up, but their study did not investigate the nutrient removal during granulation.…”

Section: Introductionmentioning

confidence: 99%

Effects of Wash-Out Dynamics on Nitrifying Bacteria in Aerobic Granular Sludge During Start-Up at Gradually Decreased Settling Time

Szabo

Hermansson

Modin

et al. 2016

Water

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Abstract:The aerobic granular sludge process is a promising technology for the removal of nutrients and organic contaminants from wastewater. However, a large amount of the sludge is often washed out during the start-up of granular reactors, which results in reduced process performance and a protracted start-up phase. In this study, the possibility of a rapid start-up of the nitrification process through a stepwise decrease of the settling time was investigated, and the bacterial population dynamics in two lab-scale sequencing batch reactors were studied. The results demonstrated that the stepwise decrease of the settling time enabled fast granulation and rapid start-up of the process. Small cores of granules were already observed after 10 days of operation, and the biomass was dominated by granules after 28 days. The removal of organic matter and ammonium was >95% after one day and 14 days, respectively. The bacterial community composition changed rapidly during the first 21 days, resulting in strongly reduced richness and evenness. The diversity increased at a later stage, and the bacterial community continued changing, albeit at a slower pace. The rate of the stepwise decrease in settling time strongly affected the abundance of nitrifying organisms, but not the general composition of the bacterial community. The results of this study support the idea that a stepwise decrease of the settling time is a successful strategy for the rapid start-up of aerobic granular sludge reactors.

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Section: Introductionmentioning

confidence: 99%

Effects of Wash-Out Dynamics on Nitrifying Bacteria in Aerobic Granular Sludge During Start-Up at Gradually Decreased Settling Time

Szabo

Hermansson

Modin

et al. 2016

Water

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“…Most research thus far has focused on the engineering aspects of the reactors and on operational variables necessary to induce granulation (11)(12)(13)(14)(15)(16). Recently, at a molecular level, the makeup of the microbial assemblies of the aggregates has been studied for aerobic granules under different conditions (17)(18)(19). Aerobic granules exposed to temporal anaerobic-aerobic cycles display the ability to biologically remove phosphorus and nitrogen in a single reactor (7).…”

mentioning

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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“…A touchdown thermal profile technique was used for the PCR procedure (Watanabe et al 1998). The PCR-amplified DNA products were separated by DGGE, and the DGGE images were acquired using the ChemiDoc (Bio-Rad, Hercules, CA, USA) gel documentation system following the procedures described previously (Li et al 2008). Quantity One software (Bio-Rad) was used for band pattern analysis.…”

Section: Shear Sensitivity Of Aggregated Flocsmentioning

confidence: 99%

“…5). In a mixture of extracted DNA, less abundant sequences may not be amplified sufficiently to form visible DGGE bands (Eichner et al 1999;Li et al 2008). For the three different reactors under different SRT conditions, the bacterial populations were different producing different DGGE bands and patterns.…”

Section: Biodiversity Of the Free Cell And Aggregated Cellmentioning

confidence: 99%

Characteristics of free cells and aggregated flocs for the flocculation and sedimentation of activated sludge

2015

Int. J. Environ. Sci. Technol.

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Laboratory experiments were conducted to investigate the correlation of the free cells/aggregated flocs characteristics and the sludge flocculation and separation behavior during the activated sludge process. Activated sludge was cultured in three laboratory-scale batch reactors with same carbon sources of glucose but different sludge retention times (SRTs) of 5, 10 and 20 days. The variation in the operation condition produced sludge with different flocculation and separation characteristics. The reactor performance in terms of bioflocculation as measured by the amount of suspended solids in the effluent, sludge sedimentation and compression as measured by the sludge value index improved considerably as the SRT lengthened. The higher SRT was related to less negatively charged surface of free cells and more hydrophobic of aggregated flocs. The negative zeta potential of aggregated flocs (11-13 mV) was smaller than that of free cells (15-23 mV), and free cells carrying lesser negative surface charges resulted in effluent clarification. Hydrophobicity of aggregated flocs (10-17 %) in each reactor was higher than that of free cells (5-8 %). The increase in hydrophobicity of aggregated flocs had positive effect on settleability. Floc strength measured by breakage/erosion index was closely related to hydrophobicity of aggregated flocs, but no correlation could be established with zeta potential of aggregated flocs. In addition, different bacterial species existed in free cells and aggregated flocs. Microbial similarity between free cells and aggregated flocs increased with shorter SRT and was closely related to effluent clarification.

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Microbial population dynamics during aerobic sludge granulation at different organic loading rates

Cited by 233 publications

References 23 publications

Effects of Wash-Out Dynamics on Nitrifying Bacteria in Aerobic Granular Sludge During Start-Up at Gradually Decreased Settling Time

Effects of Wash-Out Dynamics on Nitrifying Bacteria in Aerobic Granular Sludge During Start-Up at Gradually Decreased Settling Time

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

Characteristics of free cells and aggregated flocs for the flocculation and sedimentation of activated sludge

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