Fractionation and removal of dissolved organic carbon in a full-scale granular activated carbon filter used for drinking water production

The removal of natural organic matter (NOM) and, more particularly, its individual fractions by two different GACs was investigated in full-scale filters in a drinking water treatment plant (DWTP). Fractionation of NOM was performed by high performance size exclusion chromatography (HPSEC) into biopolymers, humic substances, building blocks and low molecular weight organics. The sorption capacity of GAC in terms of iodine number (IN) and apparent surface area (SBET), as well as the filling of narrow- and super-microporosity were monitored over the 1-year operation of the filters. Both GACs demonstrated to be effective at removing NOM over a wide range of fractions, especially the low and intermediate molecular weight fractions. TOC removal initially occurred via adsorption, and smaller (lighter) fractions were more removed as they could enter and diffuse more easily through the pores of the adsorbent. As time progressed, biodegradation also played a role in the TOC removal, and lighter fractions continued to be preferentially removed due to their higher biodegradability. The gained knowledge would assist drinking water utilities in selecting a proper GAC for the removal of NOM from water and, therefore, complying more successfully the latest water regulations.

► Removal and fractionation of NOM by two full-scale GAC filters were investigated.
► Both GACs were effective at removing NOM over a wide range of fractions.
► TOC removal was initially removed via adsorption and gradually via biodegradation.
► Low and intermediate molecular weight fractions seemed to be preferentially removed.
► The most loaded pore size range was clearly the super-microporosity (0.7–2 nm).