NAMS 2002 Workshop - ICOM 2008

Nanofiltration and Reverse Osmosis II - Imaging and Characterization – 3
Tuesday July 15, 10:00 AM-10:30 AM, Maui
Characterization of Biofouling Development of Spiral Wound Membrane
Systems: The First NMR Study
D. Graf von der Schulenburg, University of Cambridge, Cambridge, UK
J. Vrouwenvelder (Speaker), Wetsus, Delft University of Technology, Deft, The Netherlands,
hans.vrouwenvelder@wetsus.nl
J. Kruithof, Wetsus, The Netherlands
M. Van Loosdrecht, Delft University of Technology, Deft, The Netherlands
M. Johns, University of Cambridge, Cambridge, UK
High quality drinking water can be produced with membrane filtration processes
like reverse osmosis and nanofiltration. A disadvantage of membrane filtration
processes is membrane fouling, resulting in higher costs. A major fouling type is
biofouling caused by biofilm accumulation in membrane elements [1]. Biofouling
development in time is difficult to study because of the construction of spiral
wound membrane modules. There is a need for in-situ non destructive
quantitative measurements on the accumulation of biomass in spiral wound
membranes. Nuclear magnetic resonance (NMR) is a potential powerful tool to
study membrane fouling, since it is a quantitative potentially, real-time, noninvasive
measurement/imaging technique that is readily applied to opaque
samples.
The objective of this study was thus to determine if NMR is a suitable technique
to study biofouling of spiral wound membranes.
Biofilm development and velocity distribution images were determined using an
appropriate NMR spectrometer as a function of time in a spiral wound membrane
module and a flow cell containing spacers and membranes. The flow cell had the
same construction as the membrane fouling simulator [3], utilizing sheets of
membrane and spacers. The development of pressure drop in time was
monitored and the accumulated material on the membranes was analyzed for
fouling diagnosis. The feed water was supplemented with a biodegradable
compound to stimulate biofilm formation.
The presented NMR protocols allow (i) the extraction of the spatial biofilm
distribution in the membrane module, (ii) the velocity field and its evolution with
biofouling and (iii) propagators, that is distributions of molecular displacement of
a passive tracer (e.g. salts, organic molecules) in the membrane module. Despite
the opaque nature of the membrane design, NMR provides a non-invasive, nondestructive
and spatially resolved in-situ measurement of biofouling and its
impact on hydrodynamics and mass transport. In a spiral wound membrane
module, biofilm accumulation and velocity fields were observed over time. Biofilm