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Article: Physical and hydrodynamic properties of flocs produced during biological hydrogen production

TitlePhysical and hydrodynamic properties of flocs produced during biological hydrogen production
Authors
Issue Date2004
PublisherJohn Wiley & Sons, Inc. The Journal's web site is located at http://www3.interscience.wiley.com/cgi-bin/jhome/71002188
Citation
Biotechnology And Bioengineering, 2004, v. 88 n. 7, p. 854-860 How to Cite?
AbstractDense 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 (23°C, 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 ± 0.11, 2.40 ± 0.26, and 4.59 ± 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-H2/mol-glucose, increased with organic loading rates in the order 17.7%, 23.1%, and 25.6%. The gas contained 56.1 + 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 (10g-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 ± 0.17 to 2.48 ± 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. © 2004 Wiley Periodicals, Inc.
Persistent Identifierhttp://hdl.handle.net/10722/71131
ISSN
2015 Impact Factor: 4.243
2015 SCImago Journal Rankings: 1.633
ISI Accession Number ID
References

 

DC FieldValueLanguage
dc.contributor.authorZhang, JJen_HK
dc.contributor.authorLi, XYen_HK
dc.contributor.authorOh, SEen_HK
dc.contributor.authorLogan, BEen_HK
dc.date.accessioned2010-09-06T06:29:11Z-
dc.date.available2010-09-06T06:29:11Z-
dc.date.issued2004en_HK
dc.identifier.citationBiotechnology And Bioengineering, 2004, v. 88 n. 7, p. 854-860en_HK
dc.identifier.issn0006-3592en_HK
dc.identifier.urihttp://hdl.handle.net/10722/71131-
dc.description.abstractDense 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 (23°C, 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 ± 0.11, 2.40 ± 0.26, and 4.59 ± 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-H2/mol-glucose, increased with organic loading rates in the order 17.7%, 23.1%, and 25.6%. The gas contained 56.1 + 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 (10g-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 ± 0.17 to 2.48 ± 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. © 2004 Wiley Periodicals, Inc.en_HK
dc.languageengen_HK
dc.publisherJohn Wiley & Sons, Inc. The Journal's web site is located at http://www3.interscience.wiley.com/cgi-bin/jhome/71002188en_HK
dc.relation.ispartofBiotechnology and Bioengineeringen_HK
dc.rightsBiotechnology and Bioengineering. Copyright © John Wiley & Sons, Inc.en_HK
dc.subject.meshBacteria, Anaerobic - growth & development - metabolismen_HK
dc.subject.meshBiomassen_HK
dc.subject.meshBioreactors - microbiologyen_HK
dc.subject.meshCell Aggregation - physiologyen_HK
dc.subject.meshComputer Simulationen_HK
dc.subject.meshFractalsen_HK
dc.subject.meshGlucose - metabolismen_HK
dc.subject.meshHydrogen - metabolismen_HK
dc.subject.meshModels, Biologicalen_HK
dc.subject.meshParticle Sizeen_HK
dc.subject.meshRheology - methodsen_HK
dc.subject.meshWater Microbiologyen_HK
dc.subject.meshWater Purification - methodsen_HK
dc.titlePhysical and hydrodynamic properties of flocs produced during biological hydrogen productionen_HK
dc.typeArticleen_HK
dc.identifier.openurlhttp://library.hku.hk:4550/resserv?sid=HKU:IR&issn=0006-3592&volume=88&spage=854&epage=860&date=2004&atitle=Physical+and+hydrodynamic+properties+of+flocs+produced+during+biological+hydrogen+productionen_HK
dc.identifier.emailLi, XY:xlia@hkucc.hku.hken_HK
dc.identifier.authorityLi, XY=rp00222en_HK
dc.description.naturelink_to_subscribed_fulltext-
dc.identifier.doi10.1002/bit.20297en_HK
dc.identifier.pmid15538742-
dc.identifier.scopuseid_2-s2.0-10844264221en_HK
dc.identifier.hkuros105195en_HK
dc.relation.referenceshttp://www.scopus.com/mlt/select.url?eid=2-s2.0-10844264221&selection=ref&src=s&origin=recordpageen_HK
dc.identifier.volume88en_HK
dc.identifier.issue7en_HK
dc.identifier.spage854en_HK
dc.identifier.epage860en_HK
dc.identifier.isiWOS:000225557000006-
dc.publisher.placeUnited Statesen_HK
dc.identifier.scopusauthoridZhang, JJ=7601341506en_HK
dc.identifier.scopusauthoridLi, XY=26642887900en_HK
dc.identifier.scopusauthoridOh, SE=7404103316en_HK
dc.identifier.scopusauthoridLogan, BE=7202196555en_HK

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