Ozone disinfection of treated wastewater for inactivation of Cryptosporidium parvum for agricultural irrigation.

Abstract

The reliance on agriculture in many nations has increased the use of treated wastewater for irrigation. However, reclaimed water still poses health risks from resistant pathogens like Cryptosporidium spp. Ozone, a strong disinfectant, has been used in water treatment. This study assessed the microbiological quality of treated wastewater for irrigation and evaluated ozone effectiveness in inactivating C. parvum oocysts. All samples contained Cryptosporidium spp., with 163 to 850 oocysts 100 L^-1, and 50% contained viable oocysts. When C. parvum was exposed to different ozone residual concentrations (0.1, 0.8, and 1.3 mg L^-1), oocyst viability reduction of 73%, 85%, and 99% and infectivity of 0.8, 1.36, and 2 Log₁₀ was achieved. The predicted values for infectious oocysts were 4.19, 3.64, and 3.27, representing absolute counts of infective oocysts after ozone treatment. These findings demonstrate ozone's effectiveness in inactivating C. parvum in treated wastewater, supporting its potential for safe water reuse. PRACTITIONER POINTS: All wastewater samples contained Cryptosporidium spp., with 163 to 850 oocysts per 100 L. Wastewater had 50% contained viable oocysts. Ozone concentrations (0.1, 0.8, 1.3 mg/l) achieved oocyst viability of 73.33%, 85.0%, and 99.4%, respectively. The predicted values for infectious oocysts were 4.19, 3.64, and 3.27, respectively for each ozone concentration.