Solar photocatalytic disinfection of agricultural pathogenic fungi (Curvularia sp.) in real urban wastewater

Abstract

The interest in developing alternative water disinfection methods that increase the access to irrigation water free of pathogens for agricultural purposes is increasing in the last decades. Advanced Oxidation Processes (AOPs) have been demonstrated to be very efficient for the abatement of several kind of pathogens in contaminated water. The purpose of the current study was to evaluate and compare the capability of several solar AOPs for the inactivation of resistant spores of agricultural fungi. Solar photoassisted H2O2, solar photo-Fenton at acid and near-neutral pH, and solar heterogeneous photocatalysis using TiO2, with and without H2O2, have been studied for the inactivation of spores of Curvularia sp., a phytopathogenic fungi worldwide found in soils and crops. Different concentrations of reagents and catalysts were evaluated at bench scale (solar vessel reactors, 200 mL) and at pilot plant scale (solar Compound Parabolic Collector-CPC reactor, 20 L) under natural solar radiation using distilled water (DW) and real secondary effluents (SE) from a municipal wastewater treatment plant. Inactivation order of Curvularia sp. in distilled water was determined, i.e. TiO2/H2O2/sunlight (100/50 mg L− 1) > H2O2/sunlight (40 mg L− 1) > TiO2/sunlight (100 mg L− 1) > photo-Fenton with 5/10 mg L− 1 of Fe2 +/H2O2 at pH 3 and near-neutral pH. For the case of SE, at near neutral pH, the most efficient solar process was H2O2/Solar (60 mg L− 1); nevertheless, the best Curvularia sp. inactivation rate was obtained with photo-Fenton (10/20 mg L− 1 of Fe2 +/H2O2) requiring a previous water adicification to pH 3, within 300 and 210 min of solar treatment, respectively. These results show the efficiency of solar AOPs as a feasible option for the inactivation of resistant pathogens in water for crops irrigation, even in the presence of organic matter (average Dissolved Organic Carbon (DOC): 24 mg L− 1), and open a window for future wastewater reclamation and irrigation use. © 2017 Elsevier B.V.