Phenomenological study and application of the combined influence of iron concentration and irradiance on the photo-Fenton process to remove micropollutants

Abstract

The presence of low concentrations of persistent pollutants in waters (μg/L or ng/L), also called micropollutants, brings as a consequence the need to apply advanced oxidation treatments for their removal. The successful application of solar-driven photo-Fenton to treat highly polluted wastewaters (g/L and mg/L of pollutants) has prompted its application to lowly polluted effluents. However, a decrease in contaminant concentration may involve an alteration in the intrinsic process phenomenon, which until now has only been widely studied at the milligram-per-litre level or higher with this process. The aim of this research was to study the combined influence of the operating variable (iron concentration) and the environmental variable (irradiance) and application on the photo-Fenton process at pH2.8 when removing micropollutants. For this purpose, experimentation was carried out at laboratory and pilot plant scales with a biocide mixture of acetamiprid (ACTM), thiabendazole (TBZ) and imazalil (IMZ) (100μg/L each) as the model pollutant. Results indicated that above 15WUV/m2 and a light path length of 5cm (the most commonly used path for this type of application) iron concentration limited the process and there was irradiance excess under these conditions. On the other hand, and given the circumstances of irradiance excess, a higher light path length (10cm) was assessed. Results showed that path lengths wider than 5cm are recommended since more wastewater volume could be treated with a higher process rate per surface unit.