The involvement of lectins and lectin-like humic substances in biofilm formation on RO membranes - is TEP important?

Abstract

There are significant number of publications that state that the main cause of biofilm formation and organic fouling on reverse osmosis (RO) membranes is due to the presence of transparent exopolymer particles (TEP) and their precursors. Alcian Blue has been used to detect and quantify TEP and their precursors. However, Alcian Blue is not specific for TEP substances and interacts with other acidic substances, lectin-like humic substances which may also be important in biofilm formation and chemical conditioning of membrane surfaces.Certain lectin-like humic substances may be present in RO feed waters. A new assay procedure which couples, ammonium sulfate protein precipitation, LC-OCD and Alcian Blue is presented which can detect and quantify these lectin-like humics in any water sample. It appears that bio-adhesion is dependent upon these lectin-like humics and they appear to control biofilm formation.Based on results from a wastewater RO reclamation facility and examination of the literature, the presence and importance of TEP and their precursors in biofilm formation may be overstated and that biofilm and/or organic fouling on RO membranes appears to be initiated and controlled by the presence of certain lectin-like humics which may not be the dominant conditioning mechanisms in every RO desalination plant.