Comparing disinfection efficiency of ozone and peroxone in water containing Giardia duodenalis cysts

Abstract

This study aimed to investigate the efficiency of ozone and peroxone for the disinfection of water containing Giardia duodenalis cysts. Dechlorinated tap water (TW) and spring water (SW) samples were inoculated with a purified commercial suspension containing 105 cysts of Giardia duodenalis. The membrane filtration method was employed for cyst concentration, with average recovery efficiencies of 43.3% in TW and 73.3% in SW. Visualization of the cysts was carried out by Immunofluorescence Assay (IFA). The use of ozone as a disinfectant in SW showed a concentration-dependent increase in cyst damage, reaching 98% non-viability at the highest ozone concentration (5 mg L-1). The addition of hydrogen peroxide (H2O2) improved the process, as 2.5 mg L-1 of ozone at an H2O2 / O3 ratio of 0.3 caused morphological damage to 99% of the cysts. The data indicated that the lower H2O2 / O3 ratio resulted in better overall performance in terms of cyst damage. In TW, the oxidation behavior differed, with no clear difference observed between the lowest and highest ozone concentrations causing cyst wall damage. The presence of alkalinity in TW negatively affected the disinfection process, likely due to the scavenger effect of alkalinity compounds on hydroxyl radicals. The use of peroxone process with an H2O2 / O3 ratio of 0.5 yielded the highest damage to cysts in TW. The findings contribute to the understanding of factors influencing the efficacy of oxidation techniques and provide insights for developing effective disinfection strategies for water treatment systems.