EFFECT OF OZONATION ON PRELOADING OF BACKGROUND ORGANIC-MATTER IN GRANULAR ACTIVATED CARBON FILTERS

Background Organic Matter (BOM) preloading is adsorption of BOM onto G ranular Activated Carbon (GAG) prior to the adsorption of target compo unds, such as pesticides and other organic micropollutants (e.g. atraz ine). BOM preloading is commonly found to speed up the breakthrough of target compounds during GAC filtration. Ozonation of GAC filter influ ent may be expected to lower BOM preloading, because it results in les s adsorbable and more biodegradable BOM compounds. Short Fixed Bed (SF B) tests with virgin and preloaded GAG, performed within this study, c onfirmed that preloading of BOM present in pretreated river Rhine wate r speeds up the breakthrough of atrazine in GAC filters. BOM preloadin g was found to lower equilibrium adsorption capacity of GAC for atrazi ne, and to slow down both external and internal mass transfer rate of atrazine on/into GAG. Adsorption capacity of (crushed) GAC was determi ned from atrazine adsorption isotherms, while mass transfer rate coeff icients were determined by fitting the Homogeneous Surface Diffusion m odel to the breakthrough of atrazine in the SFB tests. More pronounced BOM preloading was found in the GAC filter receiving non-ozonated inf luent than in its ozonated counterpart. Biodegradation of ozonated BOM was shown to lower BOM preloading in GAC filters. (C) 1997 IAWQ. Publ ished by Elsevier Science Ltd.