Rheology of biofilms formed at the surface of NF membranes in a drinking water production unit
Titel:
Rheology of biofilms formed at the surface of NF membranes in a drinking water production unit
Auteur:
Houari, A. Picard, J. Habarou, H. Galas, L. Vaudry, H. Heim, V. Martino, P. Di
Verschenen in:
Biofouling
Paginering:
Jaargang 24 (2008) nr. 4 pagina's 235-240
Jaar:
2008
Inhoud:
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 μm. 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 (η = 300 Pa s for y = 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 G0 and η values were, respectively, 1.4 ± 0.3 × 103 Pa and 3.3 ± 0.65 × 106 Pa s. The relationship between the characteristics of NF biofilms and the flow conditions encountered during NF is discussed.