Decontamination of industrial wastewater containing pesticides by combining large-scale homogeneous solar photocatalysis and biological treatment

This work evaluates the technical feasibility of large-scale combined solar photo-Fenton/aerobic biological treatment targeting the treatment of a real industrial wastewater polluted with commercial pesticides. Photo-Fenton experiments were carried out under sunlight in a CPC-based plant (150 m2 of solar collectors and the total photo-reactor volume 1060 L). The biological reactor was an immobilized biomass reactor (IBR, 2× 1230 L) filled with Pall®Ring supports colonized by activated sludge from a municipal wastewater treatment plant. The first study performed was focused on the decontamination of wastewater containing a selected mixture of five commercial pesticides (Vydate®, Metomur®, Couraze®, Ditimur-40® and Scala®) at 500 mg/L of initial dissolved organic carbon (DOC). Real wastewater containing pesticides was tested at two different initial DOCs (200 and 500 mg/L). The solar photo-Fenton was always performed in batch mode at pH adjusted to 2.8 and with 20 mg/L of Fe2+, while the biological reactor was operated both in batch and continuous mode. Mineralization was followed by measuring DOC and chemical oxygen demand (COD) and the composition of the real wastewater was determined by liquid chromatography electrospray time-of-flight mass spectrometry (LC-TOF-MS). It has been demonstrated that photo-Fenton is able to enhance biodegradability of real wastewaters containing biorecalcitrant compounds at concentrations up to 500 mg/L but it has been also pointed out that the process should be optimized by a proper selection of treatment time and H2O2 dose.