Uses of fluorescence excitation-emissions indices in predicting water treatment efficiency

Membrane filtration is a possible alternative for the increase of the natural organic matter (NOM) content in the raw water sources in boreal areas. In a pilot study, a new hollow fiber nanofilter (HFNF) has been tested. Water from four raw water sources were treated in membrane pilot plants, and three full-scale conventional plants were sampled. Three established fluorescence indices, humification index (HIX), fluorescence index (FI) and freshness index (β:α), were used for characterization, and were related to NOM removal by the two treatment methods Although the NOM removal in the treatment processes were related to SUVA, HIX has only a weak correlation to the total organic carbon (TOC) reduction of the HFNF, and none for the conventional treatment. FI and β:α are both correlated to the TOC reduction of the HFNF. Water hardness has a logarithmical correlation to the TOC reduction by the HFNF, plausibly due to moderation of the membrane surface. FI and β:α have potential to predict the efficiency of the HFNF and conventional treatment processes, and could be used online to identify changes in the raw water which affects the process efficiency.