Degradation of antibiotic trimethoprim by the combined action of sunlight, TiO2 and persulfate: A pilot plant study

Abstract

The degradation of trimethoprim (TMP) was investigated in a compound parabolic collector (CPC) pilot scale reactor. P25 TiO2 was employed as the photocatalyst, while sodium persulfate (SPS) was activated by solar light to generate reactive radicals. Experiments were performed in three matrices, namely natural water, municipal wastewater treatment plant (MWTP) effluent and well water at SPS concentrations between 0.125 and 0.5 mM, initial solution pH between 4 and 7.5, in the presence of 1 mg/L TMP, 200 mg/L TiO2 and 10 mg/L humic acid.TMP degradation occurs by the combined action of semiconductor photocatalysis, persulfate oxidation and photolysis. The extent of TMP degradation generally increases with increasing SPS concentration and decreasing water matrix complexity, while the solution pH effect is dependent of the water matrix. SPS conversion is always slower than TMP degradation; for example, complete degradation of TMP occurs at ca 2.5 kJ/L accumulated energy with 0.125 mM SPS, whose complete conversion requires 9 kJ/L. The proposed process may be employed for the simultaneous decontamination and disinfection of water matrices. Experiments with well water in a laboratory scale reactor resulted in 5-log reduction of Enterococcus faecalis and complete removal of 1 mg/L TMP after 1 and 3.3 kJ/L accumulated energy, respectively.