Hydraulic Biofilm Resistance

Critical aspects of RO desalination: A combination strategy

“…EPS is composed of extracellular biopolymers having various structural forms, rich in 10 to 30 kDa heteropolysaccharides such as bacterial alginate [47]. Biofouling can increase transmembrane resistance, increase osmotic pressure due to hindered mass transfer away from the membrane surface, and increase axial friction losses and pressure drop in the feed channel, due to membrane fouling, spacer fouling, or both [48].…”

“…The biofilm that initially forms in feed channels and on membrane surfaces creates a hydraulic resistance that depends on biofilm composition, with EPS considered a major contributor to flux decline [49]. The volume of bacterial cells within a biofilm may be quite small; Dreszer et al [48] reported a value of less than 0.5% of the biofilm volume. Biofilm composition may change in response to nutrients, temperature, redox potential, pH, age, and cleaning history [53,54].…”

“…For both configurations, increased feed channel and transmembrane pressure drop and decreased salt rejection are potential indicators of biofouling [45]. Dreszer et al [48] measured biofilm resistance of 6×10 12 m -1 in short term (4 d) experiments employing transmembrane flux of 20 L m -2 h -1 ; this resistance is relatively small compared with the typical resistance of NF (2×10 13 m -1 ) and RO (9×10 13 m -1 ) membranes. The biofilm resistance was about an order of magnitude higher (5×10 13 m -1 ), approaching that of RO membranes, when the transmembrane flux increased to 100 L m -2 h -1 .…”

“…The biofilm resistance was about an order of magnitude higher (5×10 13 m -1 ), approaching that of RO membranes, when the transmembrane flux increased to 100 L m -2 h -1 . This resistance has been explained by a gel-like diffusion layer [49] or a tortuous matrix [48]. Zodrow et al [57] found that biofilms formed during desalination of Long Island Sound seawater pretreated by microfiltration.…”

A review of efforts to reduce membrane fouling by control of feed spacer characteristics

“…Alternative imaging methods, such as scanning electron microscope, can offer a high image resolution. However, it is a destructive technique, the visual area is small and comprises only a small part of the feed spacer or the membrane, and in addition it cannot be used to measure fouling processes directly in-situ [102][103][104]. Fouling characterization has also been carried out using electrical impedance spectroscopy [105,106] and ultrasonic time domain reflectometry [107,108] , but again it is difficult for these sensor-based methods to produce high resolution images of the fouling process directly.…”