Simultaneous degradation of the pharmaceuticals gemfibrozil, hydrochlorothiazide and naproxen and toxicity changes during UV-C and UV-C/H2O2 processes in different aqueous matrixes

The degradation of pharmaceuticals and toxicity changes in different aqueous matrixes treated by UV-C and UVC/H2O2 were evaluated. No pH influence (4.0, 6.0 and 7.0) on the degradation of the target compounds was obtained in deionised water for any target compound. Hydrochlorothiazide was the most easily photodegraded followed by naproxen and gemfibrozil. The matrix composition strongly decreased the rates and degradation efficiencies of the pharmaceuticals according to the following sequence: sewage treatment plant effluent > surface water > deionised water. In contrast, the addition of H2O2 improved the rates and degradation efficiencies when compared to the isolated use of UV-C. Better degradation efficiencies in deionised and surface water were obtained using 4 mg L-1 H2O2, and a 16-fold higher concentration of H2O2 (64 mg L-1) was required for sewage treatment plant effluent. Additionally, the sewage treatment plant matrix was the most strongly influenced by the addition of H2O2, which increased the degradation rates of gemfibrozil, hydrochlorothiazide and naproxen by 7.7-, 2.5- and 4.4-fold, respectively, when compared to UV-C. The acute toxicity to Vibrio fischeri increased in the real matrixes due to the formation of toxic transformation products from natural organic matter as confirmed by control experiments using the matrixes in the absence of the target compounds. Overall, UV-C/H2O2 is useful for degrading target compounds in all aqueous matrixes, but an initial treatment step is recommended for the removal of the natural organic matter from real matrixes.