Degradation of emerging contaminants at low concentrations in MWTPs effluents with mild solar photo-Fenton and TiO2

The purpose of this study was to propose a municipal wastewater treatment method based on solar Advanced Oxidation Processes (AOPs) permitting reuse of the treated wastewater. Experiments were performed in a pilot compound parabolic collector (CPC) solar plant at the Plataforma Solar de Almería. Mineralisation was monitored by measuring the dissolved organic carbon (DOC), and the concentration profile of each compound during degradation was determined by HPLC–UV. Two different approaches, photo-Fenton (pH = 2.8) and TiO2 were tested with 9 different emerging contaminants at 100 μg L−1 each (acetaminophen, antipyrine, atrazine, caffeine, diclofenac, isoproturon, progesterone, sulfamethoxazole, and triclosan) at low iron and TiO2 concentrations. Photo-Fenton was by far more effective than TiO2 for degrading these contaminants, and was therefore selected for further study. The 9 contaminants were tested under the following conditions without pH adjustment: (i) Fe = 5 mg L−1, D.I. water; (ii) Fe = 5, 15 and 55 mg L−1, standard fresh water; (iii) Fe = 5 mg L−1, standard fresh water without NaHCO3. Initial amount of hydrogen peroxide was 50 mg L−1, frequently analysed and added to maintain this concentration. It was demonstrated that low efficiency in some cases is mainly due to bicarbonates, and it is therefore proposed that the process be improved, either by increasing the iron concentration, or eliminating bicarbonates.