Quantitative measurement and visualization of biofilm O2 consumption rates in membrane filtration systems

There is a strong need for techniques enabling direct assessment of biological activity of biofouling in membrane filtration systems. Here we present a new quantitative and non-destructive method for mapping O2 dynamics in biofilms during biofouling studies in membrane fouling simulators (MFS). Transparent planar O2 optodes in combination with a luminescence lifetime imaging system were used to map the two-dimensional distribution of O2 concentrations and consumption rates inside the MFS. The O2 distribution was indicative for biofilm development. Biofilm activity was characterized by imaging of O2 consumption rates, where low and high activity areas could be clearly distinguished. The spatial development of O2 consumption rates, flow channels and stagnant areas could be determined. This can be used for studies on concentration polarization, i.e. salt accumulation at the membrane surface resulting in increased salt passage and reduced water flux. The new optode-based O2 imaging technique applied to MFS allows non-destructive and spatially resolved quantitative biological activity measurements (BAM) for on-site biofouling diagnosis and laboratory studies. The following set of complementary tools is now available to study development and control of biofouling in membrane systems: (i) MFS, (ii) sensitive pressure drop measurement, (iii) magnetic resonance imaging, (iv) numerical modelling, and (v) biological activity measurement based on O2 imaging methodology.