title: Rheology of biofilms formed at the surface of NF membranes in a drinking water production unit.
abstract: In this study, the mechanical properties of biofilms formed at the surface of nano-filtration (NF) membranes from a drinking water plant were analysed. Confocal laser scanning microscopy observations revealed that the NF biofilms formed a dense and heterogeneous structure at the membrane surface, with a mean thickness of 32.5 +/- 17.7 mum. The biofilms were scraped from the membrane surface and analysed in rotation and oscillation experiments with a RheoStress 150 rotating disk rheometer. During rotation analyses, a viscosity decrease with speed of shearing characteristic of rheofluidification was observed (eta = 300 Pa s for ý = 0.3 s(-1)). In the oscillation analyses with a sweeping of frequency (1-100 Hz), elasticity (G') ranged from 3000 to 3500 Pa and viscosity (G'') from 800 to 1200 Pa. Creep curves obtained with an application of a shear stress of 30 Pa were viscoelastic in nature. The G(0) and eta values were, respectively, 1.4 +/- 0.3 x 10(3) Pa and 3.3 +/- 0.65 x 10(6) Pa s. The relationship between the characteristics of NF biofilms and the flow conditions encountered during NF is discussed.
authors.affiliation: Laboratoire ERRMECe (EA1391), université de Cergy-Pontoise, Pontoise, France.
authors.forename: A
authors.initials: A
authors.lastname: Houari
authors.forename: J
authors.initials: J
authors.lastname: Picard
authors.forename: H
authors.initials: H
authors.lastname: Habarou
authors.forename: L
authors.initials: L
authors.lastname: Galas
authors.forename: H
authors.initials: H
authors.lastname: Vaudry
authors.forename: V
authors.initials: V
authors.lastname: Heim
authors.forename: P
authors.initials: P
authors.lastname: Di Martino
mesh_terms: D001419:Bacteria / Q000254:growth & development*; D018441:Biofilms / Q000254:growth & development*; D008567:Membranes, Artificial; D018613:Microscopy, Confocal; D049329:Nanostructures; D012212:Rheology / Q000295:instrumentation*; D014783:Viscosity; D014871:Water Microbiology; D014881:Water Supply
chemical_list: D008567:Membranes, Artificial