In this study, batch reactor was used to evaluate the advanced oxidation process of theUV/H_2O_2 system as a pretreatment of humic acids (HA) in drinking water. The resultsshowed that HA oxidation and H_2O_2 decomposition followed the first-order reaction kinetics.The optimum H_2O_2 dosage was found to be 3.5 - 34.7 mM, for the oxidation of humic acids(Co = 3 - 10 mg/L as nonpergeable dissolved organic carbon, NPDOC). Under theseconditions, more than 50% of HA were degraded in less than one hour and no H_2O_2 residualswere detected in the aqueous phase. The results also indicated that HA is not completelydegraded directly but go through a series of intermediates. As UV irradiation time increases,the initial HA molecules (molecular sizes > 30,000 daltons) were degraded into moleculeswith smaller sizes (< 1000 daltons). However, no apparent difference was found on thefunctional groups of the humic acids during the reactions.After the UV/H_2O_2 process, both batch and fixed bed (minicolumn) systems were used toevaluate the activated carbon adsorption of the HA. In batch adsorption system, a muchwider equilibrium range was observed for HA after UV/H_2O_2 treatment. The Freundlichisotherms changed from Qe=0.28Ce1.59 (before UV/H_2O_2) to Qe=0.74Ce1.83 (after UV/H_2O_2).For minicolumns, the ratio of nonadsorbable HA reduced from 35% to 20%, also the numberof bed volumes required for 70% breakthrough increased from 1,500 to 30,000 bed volumesafter UV/H_2O_2 treatment. The results indicated that the use of UV/H_2O_2 treatment not onlydegrade HA, but also improve the adsorbability of the HA residuals on the following GACadsorption system.
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