In this work, the photocatalytic degradation of humic acids (HAs) in aqueous solution was investigated using combined microfiltration/photocatalysis systems. The effects of initial HA concentration and UV irradiation intensity on HA removal were compared and assessed during batch operations. Significant UV₂₅₄ reduction occurred due to the adsorption of HA on TiO₂ before UV irradiation but the desorption of HA by photocatalysis brought about an increase in UV₂₅₄ and TOC of permeate. The desorptive phenomena of HA degradation processes did not follow the first-order reaction kinetics because of desorption phenomena.