Why MFI is edging SDI as a fouling index
Jan C Schippers, Sergio G Salinas-Rodriguez and Maria D Kennedy (TU Delft), UNESCO-IHE, and Siobhan Boerlage, Boerlage Consulting
A well-known weakness of this permeator was its vulnerability to fouling. Initially, this vulnerability was attributed to suspended and colloidal matter in the feed water, ie, particulate fouling. Therefore, Du Pont developed, the Silt Density Index (SDI), initially named the Fouling Index, as a parameter to characterize the fouling potential of the feedwater for permeators.
The fouling mechanism turned out to be more complicated than just fouling of the membrane surface as initially assumed. Gradually it became clear that the fouling was initiated by local clogging of the woven or non-woven fabric between the fibres, which is needed to ensure equal flow distribution of the feed water (see Figure 1).
This article first appeared in the issue of Desalination & Water Reuse magazine.
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