Development and testing of a transparent membrane biofouling monitor

Abstract

A modified version of the membrane fouling simulator (MFS) was developed for assessment of (i) hydraulic biofilm resistance, (ii) performance parameters feed-channel pressure drop and transmembrane pressure drop, and (iii) in situ spatial visual and optical observations of the biofilm in the transparent monitor, e.g. using optical coherence tomography. The flow channel height equals the feed spacer thickness enabling operation with and without feed spacer. The effective membrane surface area was enlarged from 80 to 200 cm 2 by increasing the monitor width compared to the standard MFS, resulting in larger biomass amounts for analysis. By use of a microfiltration membrane (pore size 0.05 μm) in the monitor salt concentration polarization is avoided, allowing operation at low pressures enabling accurate measurement of the intrinsic hydraulic biofilm resistance. Validation tests on e.g. hydrodynamic behavior, flow field distribution, and reproducibility showed that the small-sized monitor was a representative tool for membranes used in practice under the same operating conditions, such as spiral-wound nanofiltration and reverse osmosis membranes. Monitor studies with and without feed spacer use at a flux of 20 L m −2 h −1 and a cross-flow velocity of 0.1 m s −1 clearly showed the suitability of the monitor to determine hydraulic biofilm resistance and for controlled biofouling studies.

Compaction and relaxation of biofilms

“…The transparent membrane fouling monitor is based on the membrane fouling simulator [22,23] developed for biofouling studies. Details of the used system (modified monitor) can be found in previous work [11,24]. Fig.…”

“…Calculated data usingSchock and Miquel (1987) equation for spiralwound membrane elements (adapted from Dreszer et 'al [24]…”

Optical coherence tomography for the in situ three-dimensional visualization and quantification of feed spacer channel fouling in reverse osmosis membrane modules

“…In addition to these macroscopic parameters, imaging techniques are applied more frequently to understand the (bio)fouling formation and structure in more detail. A first option is the observation of the fouling inside feed spacer channels by eye when transparent fouling simulators are used [6]. At the microscale for instance scanning electron microscopy, atomic force microscopy, and confocal laser scanning microscopy are often used techniques to visualize the (bio)fouling structure on fouled membranes and feed spacers [7][8][9].…”

The membrane fouling simulator: development, application, and early-warning of biofouling in RO treatment

“…Short-term studies (4 and 10 d) with nutrient dosage presented the same development of FCP and biomass accumulation in MFS units operated in parallel [4,38,61].…”