Application of solar advanced oxidation processes to the degradation of the antibiotic sulfamethoxazole

This work deals with the treatment of highly concentrated sulfamethoxazole (SMX) solutions by some advanced oxidation processes (AOPs) that have not been studied until now. The antibiotic has been subjected to oxidation by photolysis, UV/H2O2 and photo-Fenton using both artificial light and sunlight as radiation sources depending on the installation scale. SMX, total organic carbon (TOC) and chemical oxygen demand (COD), as well as the generation of NH4+, NO3- and SO42-, were followed. SMX photolytic degradation efficiency followed the ranking: 254 nm lamps > sunlight > black-light blue (BLB) lamps (negligible for the latter). The highest eliminations were obtained by means of UV/H2O2 reaction in a lab-scale reactor (254 nm lamps) with an initial H2O2 concentration of 200 mg L-1: Delta TOC = 62.3%; Delta COD = 79.1% (more than 6 h). Similar removals were achieved with a lab-scale photo-Fenton reactor (BLB lamps) but using 400 mg L-1 of oxidant (94 min). The use of solar light appeared to be an interesting option since satisfactory results were obtained in the solar-based photo-Fenton experiments compared to the lab-scale ones, and also since a significant improvement with respect to the solar photolysis was achieved when performing the UV/H2O2 reaction with sunlight. Finally, some of the resultant effluents from different reactions were subjected to a short-term biodegradability test in order to estimate their quality from a biological point of view.