The present study reports the treatment performance and selectivity of two photochemically active materials, namely TiO2 (1 g/L, pH = 2.8) and the heteropolyacid H4SiW12O40 (1.44 g/L or 0.5 mM in aqueous solution, pH = 2.8) for the oxidation of phenol, isopropyl alcohol and formic acid selected as the recalcitrant index pollutants, using UV-C (20 W) and UV-A (125 W) light sources in two different photoreactors. In separate experiments, the effect of the zeolites Y (1 g/L; Si/Al = 5.2/1 and 80/1) and Beta (1 g/L; Si/Al = 75/1) as TiO2 and H4SiW12O40 catalyst supports has also been studied under the same reaction conditions. It could be demonstrated that H4SiW12O40 is More selective than TiO2, especially for the charge transfer type isopropanol oxidation. It was also found that the zeolitic supports improved the photocatalytic activity of poly-oxometalates (POM) with a pronounced effect for UV-C (short-UV) irradiation. A significantly reduced photoactivity (12.5 % for UV-A and 9.5 % for UV-C) in comparison with TiO2-mediated photocatalysis was observed for the combination POM + TiO2, speculatively due to the conduction band electron "short-circuit" effect of POM, i.e. e(cb)(-) + POM --> POMred.