Reduction of ClO2 demand by ClO2 oxidation and subsequent GAC filtration

The effective removal of soluble natural organic matter (NOM) during water treatment can significantly decrease the ClO2 demand of processed water. This can be achieved through the oxidation and/or the removal of NOM. The purpose of the study was to examine the influence of ClO2 oxidation and subsequent GAC filtration on the final ClO2 demand of treated water. The study showed the ClO2 demand to be strongly correlated with the abundance of high molecular fractions of NOM in treated water. As it was shown, this part of NOM was effectively removed during the GAC filtration. Moreover, the pretreatment of water with ClO2 considerably increased the total capacity of GAC filters for organic and inorganic (i.e. chlorites) oxidation by-products. Therefore, the oxidation of NOM molecules in conjunction with a very efficient GAC filtration can be successfully employed to control the abundance of high molecular NOM components, and thus the ClO2 demand of finished water.