Solar photocatalysis as a tertiary treatment to remove emerging pollutants from wastewater treatment plant effluents

Water taken from the outlet of a wastewater treatment plant from the South East of Spain has been treated by means of TiO2-based solar photocatalysis. Preliminary analysis showed the presence of significant amounts of nine emerging pollutants (order of magnitude of ng/l): trimethoprim, ofloxacin, enrofloxacin, clarithromycin, acetaminophen, diclofenac, caffeine, thiabendazole and carbamazepine; and trace amounts of another two were detected, namely acetamiprid and erythromycin. Irradiation of the effluent in the presence of TiO2 resulted in a significant removal of all the emerging pollutants, as most of them were detected only at trace amounts after the treatment. In addition to this, percentages of faecal bacteria elimination were close to 100%. Finally, experiments carried out using caffeine as model compound showed that a mild photo-Fenton process might be employed at neutral media in the presence of humic acids, although the performance was worse than photo-Fenton at acidic pH or TiO2.