Commercial fertilizer as effective iron chelate (Fe3+-EDDHA) for wastewater disinfection under natural sunlight for reusing in irrigation

Abstract

In this study, the use of a commercial iron fertilizer (Fe3+-EDDHA) employed to remediate iron chlorosis in agriculture has been investigated as a promoting bactericidal agent in solar wastewater disinfection processes. Two water matrices: isotonic water (IW) and synthetic fresh-cut wastewater (SFCWW) and two bacterial strains (E. coli O157:H7 and Salmonella enteritidis) have been investigated. The bacterial inactivation rates were compared with other solar processes (solar only, H2O2/solar, Fe3+/solar and Fe3+/H2O2/solar) at neutral pH and at laboratory scale (200 mL) under natural solar radiation. Reagents concentration tested was 0.5, 2.5 and 5 mg L−1 of Fe3+ or Fe3+-EDDHA and 1, 5 and 10 mg L-1 of H2O2.Microbial inactivation kinetics showed an improvement of the solar disinfection efficiency when using Fe3+-EDDHA/solar in comparison with Fe3+/H2O2/solar (conventional photo-Fenton) in both water matrices. Among all reagent concentrations tested, the best inactivation kinetic rate for both bacteria was obtained with 2.5/5 mg L−1 Fe3+-EDDHA/H2O2, reaching > 5-log reduction in 45 min of treatment or 31 Whm-2 of solar UVA-dose. In addition, an inactivation mechanism has been proposed based on changes in membrane permeability when Fe3+-EDDHA is present and on structural damages caused by hydroxyl radicals (HO•) for Fe3+-EDDHA/H2O2/solar process.Finally, this study highlights the possibility of efficient fresh-cut wastewater treat for further irrigation reuse in arid and semiarid regions using disinfected wastewater that already includes iron fertilizer, reducing water scarcity and with the additional advantage of diminished impact of iron chlorosis in crops.