Mild solar photo-Fenton: An effective tool for the removal of Fusarium from simulated municipal effluents

Abstract

In this work, the efficacy of natural solar radiation (up to 21.1 kJ/L of UV energy dose) combined with homogeneous iron (5 and 10 mg/L Fe2+) and/or hydrogen peroxide (10 and 20 mg/L) to treat a simulated municipal effluent in a solar bottle reactor was assessed. Emphasis was given on the inactivation of resistant spores with Fusarium solani serving as the test species in a matrix containing 25 mg/L of dissolved organic carbon, 65 mg/L of inorganic carbon and pH about 8. Processes like dark Fenton oxidation (5 mg/L Fe2+ and 10 mg/L H2O2 at pH 3), solar radiation alone (at 21.1 kJ/L and pH 3–8) and H2O2 oxidation alone (up to 20 mg/L in the dark) led to no or inadequate disinfection, thus showing the resistance of F. solani. Solar irradiation in the presence of 10 mg/L peroxide led to complete inactivation (i.e. ≤2 CFU/mL which is the detection limit) with 11.9 kJ/L at pH 3 and 16.9 kJ/L at pH 4–8, but no mineralization occurred. When the process was added 5 mg/L Fe2+, complete inactivation required 17.1 kJ/L at pH 3 but this was accompanied by 36% mineralization. Interestingly, doubling the concentration iron and peroxide hindered inactivation but promoted mineralization; these results demonstrate a competitive effect between spores and the effluent organic matter for hydrogen peroxide, hydroxyl radicals and other ROS and highlight the importance of the nature of the microorganism. Finally, the implications for wastewater treatment are also discussed.