Structure of activated sludge floes

Li, Dahong; Ganczarczyk, Jerzy J.

doi:10.1002/bit.260350109

Cited by 204 publications

(104 citation statements)

References 14 publications

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“…Although biohydrogen flocs examined here had similar fractal dimensions to other biological aggregates, they were much more dense than other biological aggregates, as evidenced by their lower porosities. Activated sludge flocs larger than 0.1 cm typically have a porosity greater than 0.95 (Li and Ganczarczyk, 1990;Lee et al, 1996; Yuan, 2002;Li et al, 2003). However, most biohydrogen flocs examined here had porosities that were less than 0.95.…”

Section: Discussionmentioning

confidence: 77%

“…The open structure of highly porous and fractal aggregates can allow intra-aggregate flow through the flocs, resulting in their settling velocity being appreciably faster than that predicted for impermeable spherical particles (Li and Ganczarczyk, 1992;Johnson et al, 1996;Li and Yuan, 2002). Biological flocs produced in activated sludge reactors are highly porous and fractal (Li and Ganczarczyk, 1990;Lee et al, 1996;Li and Yuan, 2002), but the flow through the floc is not large enough to affect their settling behavior. However, floc permeability can affect mass transport rates to bacteria inside the floc, even under conditions where it does not affect settling velocity (Logan and Hunt, 1988;Li and Ganczarczyk, 1992;Tsou et al, 2002;Li et al, 2003).…”

Section: Introductionmentioning

confidence: 99%

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Physical and hydrodynamic properties of flocs produced during biological hydrogen production

Zhang¹,

Li²,

Oh³

et al. 2004

Biotech & Bioengineering

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Dense flocs readily form in continuous culture bioreactors used for hydrogen production, but the fractal and hydrodynamic properties of these flocs have not been previously analyzed. We therefore examined the size distribution, fractal dimension, and hydrodynamic properties of flocs formed in a continuous flow, well-mixed reactor treating synthetic wastewater at a fixed condition of a 4.5 h hydraulic detention time (23jC, pH 5.5). The reactor was operated for a total of 3 months at three different organic loading rates (27, 53, and 80 g-COD/L-d) with influent glucose concentrations of 5, 10, and 15 g-COD/L. At all three loading rates the removal of glucose was nearly complete (98.6 -99.4%) and biomass was produced in proportion to the organic loading rate (0.86 F 0.11, 2.40 F 0.26, and 4.59 F 1.55 g/L of MLVSS in the reactor). Overall conversion efficiencies of glucose to hydrogen, evaluated on the basis of a maximum of 4 mol-H 2 /molglucose, increased with organic loading rates in the order 17.7%, 23.1%, and 25.6%. The gas contained 56.1 F 4.9% hydrogen, with the balance as carbon dioxide. No methane gas was detected. Under these conditions, flocs were produced with mean sizes that increased with organic loading, in the order 0.12 cm (5 g-COD/L), 0.35 cm (10 g-COD/L), and 0.58 cm (15 g-COD/L). As the average floc size increased, the flocs became on average denser and less fractal, with fractal dimensions increasing from 2.11 F 0.17 to 2.48 F 0.13. Floc porosities ranged from 0.75 -0.96, and resulted in aggregate densities that allowed little intra-aggregate flow through the floc. As a result, average settling velocities were not appreciably larger than those predicted by Stokes' law for spherical, impermeable flocs. Our results demonstrate that dense, relatively impermeable flocs are produced in biohydrogen reactors that have settling properties in reasonable agreement with Stokes' law. B 2004 Wiley Periodicals, Inc.

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Section: Discussionmentioning

confidence: 77%

Section: Introductionmentioning

confidence: 99%

Physical and hydrodynamic properties of flocs produced during biological hydrogen production

Zhang¹,

Li²,

Oh³

et al. 2004

Biotech & Bioengineering

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“…These may be divided into those discussing the general architecture revealed after fixation, embedding, dehydration and sectioning followed by light microscopic (Li & Ganczarczyk 1990) or electron microscopic (Zartarian et al 1994) examination and those applying rRNA targeted oligonucleotide probes to label certain microbial groups within the activated sludge floc. These fixed samples were examined by employing epifluorescence microscopy or CLSM (e.g., Wagner et al 1994a,b, Amann et al 1995, Manz et al 1998.…”

Section: Discussionmentioning

confidence: 99%

In situ cell and glycoconjugate distribution in river snow studied by confocal laser scanning microscopy

Neu¹

2000

Aquat. Microb. Ecol.

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Aggregates from the river Elbe (Germany) were collected and examined by confocal laser scanning microscopy. The river snow was directly transferred into coverslip chambers and observed without any embedding and fixation procedure. River snow samples were examined in the reflection and fluorescence mode to record mineral content and autofluorescence signals. Spatial distribution of microb~al cells within the aggregates was shown with general nucleic acid specific stains (SYTO 9, SYTO 64). The polymeric matnx of the river snow was demonstrated by using a panel of fluorescently labelled lectins. Staining with FITC and TRITC labelled lectins and simultaneous dual channel unaging showed the distribution of different types of glycoconjugates. The binding pattern observed included bacterial cell surface labelling and cloud-type labelling of extracellular polymeric substances (EPS). In addition, dual staining combined with triple-channel recording was employed to clearly separate the signal in the red channel originating from TRITC-lectin or SYTO 64 nucleic acid stain from the far red autofluorescence originating from chlorophyll-containing organisms. With this approach the fully hydrated, living, 3-dimensional architecture of aquatic aggregates was investigated. Application of lectins demonstrated the heterogeneity of the EPS matrix in between the cellular constituents of the river snow community. The chemical heterogeneity of river snow may be significant for sorption and transport of nutrients and contaminants in lotlc aquatic environments. This in situ technique may be also useful to examine interfacial microbial consortia in other habitats. Finally, it is suggested to employ in situ lectin staining to probe for the glycoconjugate distribution at the polymer level similar to in situ hybridisation with rRNA targeted oligonucleotides at the cellular level.

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“…Using the open-ended coaxial probe, we have made the first measurements of the complex permittivity and conductivity of thickened waste-activated sludge (WAS) [9] sampled from our local wastewater treatment facility (WWTF) [10]. Characterizing the electrical properties of materials has both scientific and practical value.…”

Section: Introductionmentioning

confidence: 99%

Permittivity Measurements of Biological Samples by an Open-Ended Coaxial Line

Bobowski¹,

Johnson²

2012

PIER B

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Abstract-We previously reported on the complex permittivity and dc conductivity of waste-activated sludge. The measurements, spanning a frequency range of 3 MHz to 40 GHz, were made using an open-ended coaxial transmission line. Although this technique is well established in the literature, we found that it was necessary to combine methods from several papers to use the open-ended coaxial probe to reliably characterize biological samples having a high dc conductivity. Here, we provide a set of detailed and practical guidelines that can be used to determine the permittivity and conductivity of biological samples over a broad frequency range. Due to the electrode polarization effect, low frequency measurements of conducting samples require corrections to extract the intrinsic electrical properties. We describe one practical correction scheme and verify its reliability using a control sample.

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Structure of activated sludge floes

Cited by 204 publications

References 14 publications

Physical and hydrodynamic properties of flocs produced during biological hydrogen production

Physical and hydrodynamic properties of flocs produced during biological hydrogen production

In situ cell and glycoconjugate distribution in river snow studied by confocal laser scanning microscopy

Permittivity Measurements of Biological Samples by an Open-Ended Coaxial Line

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