Inactivation of Ascaris eggs in water using sequential solar driven photo-Fenton and free chlorine

Abstract

Sequential helminth egg inactivation using a solar driven advanced oxidation process (AOP) followed by chlorine was achieved. The photo-assisted Fenton process was tested alone under different H2O2 and/or Fe(II) concentrations to assess its ability to inactivate Ascaris suum eggs. The effect of free chlorine alone was also tested. The lowest egg inactivation results were found using Fe(II) or H2O2 separately (5 and 140 mmol L−1, respectively) in dark conditions, which showed about 28% inactivation of helminth eggs. By combining Fe(II) and H2O2 at the same concentrations described earlier, 55% of helminth egg inactivation was achieved. By increasing the reagent's concentration two-fold, 83% egg inactivation was achieved after 120 min of reaction time. Process efficiency was enhanced by solar excitation. Using solar disinfection only, the A. suum eggs inactivation reached was the lowest observed (58% egg inactivation after 120 min (120 kJ L−1)), compared with tests using the photo-Fenton process. The use of the photo-Fenton reaction enhanced the process up to over 99% of egg inactivation after 120 kJ L−1 when the highest Fe(II) and H2O2 concentration was tested. Practically no effect on the helminth eggs was observed with free chlorine alone after 550 mg min L−1 was used. Egg inactivation in the range of 25–30% was obtained for sequential processes (AOP then chlorine) using about 150 mg min L−1.