Gel-forming exopolysaccharides explain basic differences between structures of aerobic sludge granules and floccular sludges

Seviour, T., Pijuan, M., Nicholson, T., Keller, J. and Yuan, Z.G. (2009) Gel-forming exopolysaccharides explain basic differences between structures of aerobic sludge granules and floccular sludges. Water Research, 43 18: 4469-4478. doi:10.1016/j.watres.2009.07.018


Author Seviour, T.
Pijuan, M.
Nicholson, T.
Keller, J.
Yuan, Z.G.
Title Gel-forming exopolysaccharides explain basic differences between structures of aerobic sludge granules and floccular sludges
Journal name Water Research   Check publisher's open access policy
ISSN 0043-1354
Publication date 2009-10-01
Year available 2009
Sub-type Article (original research)
DOI 10.1016/j.watres.2009.07.018
Volume 43
Issue 18
Start page 4469
End page 4478
Total pages 10
Editor Mogens Henze
Place of publication Oxford, U.K.
Publisher Pergamon Press
Collection year 2010
Language eng
Subject C1
Abstract The sol-gel transition of extracellular polymeric ubstances (EPS) derived from sludge flocs and granules is investigated in order to explain basic differences between the two aggregates. A reversible, pH dependent sol-gel transition was observed at pH 9.0–12.0 in EPS extracted from granules. At pH <9 granule EPS existed as a strong gel, indicating that their EPS exist in a gel state at normal operating pH of a wastewater treatment system (i.e. 6.0–8.5). This characteristic transition from solution to strong gel was not observed in any of the EPS samples derived from floccular sludges. A transition to a weak gel was however, observed at pH 4.0–5.0. Enriched exopolysaccharides from the granular EPS exhibited rheological behaviour analogous to the granules and the granule EPS. The critical overlap concentration (c*) of the exopolysaccharide concentrate was 0.33% w/w, similar to the c* of other known bacterial exopolysaccharides. Additionally, the protein content was found to be not contributing to the storage modulus of granule EPS gels. These factors suggest that exopolysaccharides or glycosides were the gelling agent in aerobic sludge granules. Given that EPS derived from aerobic sludge granules and flocs are distinguished by such a solstrong gel transition, these exopolysaccharides therefore likely play an important role in granulation.
Keyword Aerobic sludge granules
Extracellular polymeric substances
Hydrogels
Sol-gel transition
Floccular sludge
Q-Index Code C1
Q-Index Status Confirmed Code

 
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Created: Sun, 22 Nov 2009, 10:00:13 EST