In this study natural organic matter (NOM) removal by ultra- and nanofiltration from four different raw waters was investigated. The experiments were carried out with a flat channel cross flow unit and with a pilot unit equipped with two parallel spiral wound modules. NOM rejection was characterized using 13CMAS-NMR spectroscopy, scanning electron microscopy (SEM) and size exclusion chromatography with online DOC detection (LC-OCD). Additionally measurements, such as DOC, UVA (254nm and 436nm), AOX- and THM-precursors, ion concentration, turbidity, etc. were made on raw waters, permeates and concentrates. The results indicate that NOM removal by nanofiltration for all water sources is almost complete (>90%), while NOM removal by ultrafiltration depends on raw water chemistry, especially ionic strength. Solid state 13C-NMR spectra of freeze-dried NOM deposits on membrane surfaces suggest the presence of structural polysaccharides (such as chitin and cellulose). SEM images confirm the NMR-results: after filtration, inorganic deposits and algae like structures were found on membrane surfaces.

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