The effectiveness of ozonation, adsorption and catalytic ozonation with ferric hydroxide (FeOOH) and cerium dioxide (CeO2) as catalysts on removal of several organic acids were investigated. The organic acids selected were benzoic acid (BA), phthalic acid (PA), commercial humic acid (CHA), and humic acid of Songhua River water (SHA) concentrated with reverse osmosis (RO). FeOOH was active in catalytic ozonation of the non-adsorbable BA, with 45% of BA removal higher than ozonation alone. It was inactive in case of ozonation of PA, the adsorption of which on FeOOH caused 5% reduction of its concentration. CeO2 enhanced ozonation of PA that was strongly adsorbed, but not for the non-adsorbed BA. Oxalate ions as product of oxidation of PA were also removed by CeO2 catalytic ozonation. As adsorption of humic acids on CeO2 is stronger than that on FeOOH, its catalytic removal by CeO2 was more than by FeOOH. The activity of catalytic ozonation of humic acids was scavenged in case of competition for adsorption sites on the catalysts by inorganic anions.