Low-Fouling Membranes

Low-fouling membranes are available from some manufacturers. These membranes can be modified is several ways to reduce the potential for fouling them with contaminants in the feed water. Chapter 4.2.3 describes these modifications in more detail. 

An example of a low-fouling membrane is the Hydranautics low-fouling composite LFC3-LD membrane (see Chapter 4.4.2.3 for a description of the LD (low-differential-pressure) membrane). This membrane exhibits the same throughput as the standard 

Low-differential-pressure membrane modules can be considered a subset of low-fouling membranes. These low-differential-pressure membrane modules typically have a thicker feed spacer. Instead of the standard 28-mil thick spacer, these low-differential-pressure membranes have 31- or 34-mil thick spacers. There is less resistance to flow through the feed channels, resulting in lower pressure drops through the membrane modules. Furthermore, the feed channels will not plug as quickly with suspended solids, foulants, or scale. Examples of low-differential-pressure membrane modules are the FilmTec BW30-400-34i (with a 34-mil feed spacer) and the Hydranautics CPA3-LD (with a 31-mil feed spacer). 

High productivity can also be achieved with brief, measured exposure to free chlorine (see Chapter 8.2.1). Membrane manufacturers will sometimes treat their membranes with a very short exposure to free chlorine. This results in membranes that exhibit higher flux with no change in salt rejection. Longer exposure to free chlorine will result in a permanent loss of salt rejection. Note that exposure to free chlorine by the end user is a violation of the membrane warranty and should not be attempted to increase flux. 

There are other types of membrane and modules available. These types spring from applications where the need is different than standard membranes can handle. Two common applications are boron rejection and sanitary processing. 

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N. 1994 - TriSep introduces first low fouling membrane (see Chapter 4.4.2.3)... 

In general, it may be concluded that despite the endeavor described earlier to develop low-fouling membranes via surface modification with nanoparticles, further research is still needed to investigate the combined effects of the water chanistry, the nature of the nanoparticles, and the coating conditions on the modified-manbrane performance and fouling mitigation. Also, careful control and monitoring of the nanoparticles released from the modified membranes are necessary to minimize potential environment (eco) toxicity effects (Tiede et al. 2009). 

Kull, K.R., Steen, M.L. and Fisher, E.R. 2005. Surface modification with nitrogen-containing plasmas to produce hydrophilic, low-fouling membranes. 

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