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Article: Stability of sludge flocs under shear conditions: Roles of extracellular polymeric substances (EPS)

TitleStability of sludge flocs under shear conditions: Roles of extracellular polymeric substances (EPS)
Authors
Issue Date2006
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, 2006, v. 93 n. 6, p. 1095-1102 How to Cite?
AbstractThe roles of extracellular polymer substances (EPS) in the shear stability of aerobic and anaerobic flocs were investigated. Both pH and EDTA concentration had a significant effect on the floc stability. The sludge flocs became much weaker as the solution pH increase to above 10. Addition of 1 mM EDTA or more could cause considerable cell erosion and deflocculation of the anaerobic flocs, whereas more than 3 mM EDTA was needed to show its adverse effect on the stability of aerobic flocs. A fraction of the EPS, around 10 mg/g SS for the aerobic flocs and 15 mg/g SS for the anaerobic flocs, could be extracted by fluid shear when the dispersed mass concentration approached the equilibrium. This suggests that most of the dispersed particles were glued by a small amount of readily-extractable EPS fraction. In addition to the abundance of this EPS fraction, its proteins/carbohydrates ratio, about 0.22:1 for the aerobic flocs and 2.66:1 for the anaerobic flocs, also appeared to be an important factor governing the microbial floc stability. A lower content of the readily-extractable EPS fraction and a lower ratio of proteins/carbohydrates were responsible for the greater stability of microbial flocs. The total content of the EPS, however, did not show a direct correlation with the floc stability. A hypothesis about biological flocs with two distinct structural regions was proposed. The outer part contained dispersible cells loosely entangled by the readily-extractable EPS fraction. This part was layered and would become completely dispersed at an infinite shear intensity. On the other hand, the inner part contains biomass in a stable structure tightly glued by EPS, which could not be dispersed by shear except under unfavorable conditions. © 2006 Wiley Periodicals, Inc.
Persistent Identifierhttp://hdl.handle.net/10722/71849
ISSN
2015 Impact Factor: 4.243
2015 SCImago Journal Rankings: 1.633
ISI Accession Number ID
References

 

DC FieldValueLanguage
dc.contributor.authorSheng, GPen_HK
dc.contributor.authorYu, HQen_HK
dc.contributor.authorLi, XYen_HK
dc.date.accessioned2010-09-06T06:35:43Z-
dc.date.available2010-09-06T06:35:43Z-
dc.date.issued2006en_HK
dc.identifier.citationBiotechnology And Bioengineering, 2006, v. 93 n. 6, p. 1095-1102en_HK
dc.identifier.issn0006-3592en_HK
dc.identifier.urihttp://hdl.handle.net/10722/71849-
dc.description.abstractThe roles of extracellular polymer substances (EPS) in the shear stability of aerobic and anaerobic flocs were investigated. Both pH and EDTA concentration had a significant effect on the floc stability. The sludge flocs became much weaker as the solution pH increase to above 10. Addition of 1 mM EDTA or more could cause considerable cell erosion and deflocculation of the anaerobic flocs, whereas more than 3 mM EDTA was needed to show its adverse effect on the stability of aerobic flocs. A fraction of the EPS, around 10 mg/g SS for the aerobic flocs and 15 mg/g SS for the anaerobic flocs, could be extracted by fluid shear when the dispersed mass concentration approached the equilibrium. This suggests that most of the dispersed particles were glued by a small amount of readily-extractable EPS fraction. In addition to the abundance of this EPS fraction, its proteins/carbohydrates ratio, about 0.22:1 for the aerobic flocs and 2.66:1 for the anaerobic flocs, also appeared to be an important factor governing the microbial floc stability. A lower content of the readily-extractable EPS fraction and a lower ratio of proteins/carbohydrates were responsible for the greater stability of microbial flocs. The total content of the EPS, however, did not show a direct correlation with the floc stability. A hypothesis about biological flocs with two distinct structural regions was proposed. The outer part contained dispersible cells loosely entangled by the readily-extractable EPS fraction. This part was layered and would become completely dispersed at an infinite shear intensity. On the other hand, the inner part contains biomass in a stable structure tightly glued by EPS, which could not be dispersed by shear except under unfavorable conditions. © 2006 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.meshBacterial Adhesionen_HK
dc.subject.meshBiodegradation, Environmentalen_HK
dc.subject.meshBiopolymers - analysis - chemistryen_HK
dc.subject.meshBioreactors - microbiologyen_HK
dc.subject.meshEdetic Acid - chemistryen_HK
dc.subject.meshFlocculationen_HK
dc.subject.meshHydrogen-Ion Concentrationen_HK
dc.subject.meshPolysaccharides - analysis - chemistryen_HK
dc.subject.meshProteins - analysis - chemistryen_HK
dc.subject.meshRheologyen_HK
dc.subject.meshSewage - chemistry - microbiologyen_HK
dc.subject.meshThermodynamicsen_HK
dc.titleStability of sludge flocs under shear conditions: Roles of extracellular polymeric substances (EPS)en_HK
dc.typeArticleen_HK
dc.identifier.openurlhttp://library.hku.hk:4550/resserv?sid=HKU:IR&issn=0006-3592&volume=93&spage=1095&epage=1102&date=2006&atitle=Stability+of+sludge+flocs+under+shear+conditions:+Roles+of+extracellular+polymeric+substances+(EPS)en_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.20819en_HK
dc.identifier.pmid16435397en_HK
dc.identifier.scopuseid_2-s2.0-33646067768en_HK
dc.identifier.hkuros125585en_HK
dc.relation.referenceshttp://www.scopus.com/mlt/select.url?eid=2-s2.0-33646067768&selection=ref&src=s&origin=recordpageen_HK
dc.identifier.volume93en_HK
dc.identifier.issue6en_HK
dc.identifier.spage1095en_HK
dc.identifier.epage1102en_HK
dc.identifier.isiWOS:000236592200008-
dc.publisher.placeUnited Statesen_HK
dc.identifier.scopusauthoridSheng, GP=34573573700en_HK
dc.identifier.scopusauthoridYu, HQ=13008678100en_HK
dc.identifier.scopusauthoridLi, XY=26642887900en_HK

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