Membrane fouling monitoring

The main problem with pressure-driven membrane processes is the flux decline as a function of filtration time (Fig. 3.6-3) due, most importantly, to concentration polarization (remaining constant once estabhshed) and membrane fouling (worsening as a function of time). These cause extra resistances on top of the membrane resistance and thus slow down the transport This reduction can be as severe as 99% of the initial flux value in M F. Reviews are available on these matters [7], some focusing in more detail on in situ monitoring techniques [8], some only on concentration polarization [9] others only on fouling [10-12]. 

Phattaranawik J, Fane AG, Pasquier ACS. Studies of air slug distributions and preliminary membrane fouling by optical monitoring in a side-stream membrane module. Sep. Sci. Technol. 2009 44 3793-3813. 

Confocal Scanning Laser Microscopy Fundamentals and Uses on Membrane Fouling Characterization and Opportunities for Online Monitoring... 

The next section gives a review about studies using acoustic waves for the monitoring of membrane fouling. 

The monitoring of membrane fouling with acoustic waves is one of the few non-invasive methods potentially applicable to commercial-scale modules. Nonetheless, amplitude measurements can only provide qualitative characterization (relative amplitude variations) of the cake formation process because of the lack of knowledge about the propagation mode of an acoustic wave in a deformable deposit. 

Towards Fouling Monitoring and Visualization in Membrane Bioreactors... 

Projector technique (PT), one early application of optical techniques to membrane fouling visualization, utilizes a projector and screen to monitor fouling deposition. This technique was applied to measure biofilm thickness on the silicone rubber tubular membrane during wastewater filtration [63]. The thickness was then measured and photographed from direct visual observation on the projector screen. 

Li, J. X., Hallbauer, D. K., and Sanderson, R. D. (2003). Direct monitoring of membrane fouling and cleaning during ultrafiltration using a non-invasive ultrasoruc technique. J. Membr. Sci. 215, 33. 

Biological fouling was monitored using the customary indicators of RO performance, including flux (productivity), salt passage, and bundle pressure drops (AP). In addition, the total bacteria count (TBC) of the RO feed water and the reject brine stream were also obtained using the membrane filtration method (Ref. 6). The increase in TBC between the feed and reject portions of the system had been found in the preliminary stages of... 

Fig. 10.2 Various monitoring devices (1 to r) corrosion/fouling/ biofouling mesh coupons, LPRM monitor, corrosion rack, deposit monitor, membrane filter on poured plate, and dip-slide... 

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