## 3 Results and Discussion
### Effects of O3 on S. typhimurium Inactivation  
Effects of ozone on _S. typhimurium_ reduction were estimated (Figure 4), and results showed that more than 1-2 log reduction was achieved depending on the ozone concentrations and exposure time. The _S. typhimurium_ reduction was compared in the dairy manure with and without autoclave (i.e., pretreatment) to understand the impacts of microbial interference in treatment. As shown in Figure 4, the bacteria counts were significantly decreased along with the exposure time. The reduction percentages in treatment with  
Figure 3: Change in _E. coli_ levels in autoclaved manure. (**A**) _E. coli_ O157:H7 counts; (**B**) reduction percentages in the autoclaved dairy manure inoculated with _E. coli_ O157:H7 under different ozone concentrations and durations (means denoted by a different letter indicate significant differences between treatments (_p_ < 0.05)). ozone concentrations of 132.46 mg\(\cdot\)L\({}^{-1}\) were significantly higher than that at 43.26 or 87.40 mg\(\cdot\)L\({}^{-1}\) (\(p\) = 0.05). Figure 5 showed _Salmonella_ reductions in the dairy manure, which was autoclaved before O\({}_{3}\) treatment. The reduction percentages in treatments of 87.40 and 132.46 mg\(\cdot\)L\({}^{-1}\) were significantly higher than that in 43.26 mg\(\cdot\)L\({}^{-1}\). The reduction percentages in autoclaved dairy manure were significantly higher than the reductions in the material without an autoclave, and similar findings are presented elsewhere [67]. These results showed that the effects of ozone on the removal of the studied two pathogens were similar for both species (_E. coli_ and _Salmonella_), and ozone may eliminate a range of pathogenic species [68]. Figure 4: _S. typhimurium_ (**A**) counts and (**B**) reduction percentages in the dairy manure inoculated with _S. typhimurium_ under different ozone concentrations and durations (means denoted by a different letter indicate significant differences between treatments (\(p<0.05\))). In previous studies, pathogen removal through ozone treatments has been demonstrated on various surface types and bacteria. As an example, ozone treatments were used on personal protective equipment (PPE) to study coronavirus 2 (SARS-CoV-2) and ozone impacts on it. To generate O\({}_{3}\) concentrations a medical ozone generator that produced higher ozone concentrations at 500 and 40,000 ppm (1-80 g/m\({}^{3}\)) was used and a special ozone chamber was designed that produced low concentrations of ozone 8-12 ppm (0.016-0.024 g/m\({}^{3}\)). While at high concentrations, there was a vir  
Figure 5: _S. typhimurium_ (**A**) counts and (**B**) reduction percentages in the autoclaved dairy manure inoculated with _S. typhimurium_ under different ozone concentrations and durations (means denoted by a different letter indicate significant differences between treatments (_p_ < 0.05)). minutes of exposure, the effects of ozone were low at low concentrations. Further, the virucidal effects of ozone treatment on SARS-CoV-2 were also dependent on humidity levels [69]. Other studies displayed reductions of _Escherichia coli_ O157:H7 and _Salmonella_ in apple cider and orange juice at thermophilic conditions. _E. coli_ and _Salmonella_ populations were reduced below the detection limit dependent on temperature conditions. In apple cider, impacts of ozone were greater in _E. coli_ and _Salmonella_ reductions at 50 \({}^{\circ}\)C than at 4 \({}^{\circ}\)C (\(p<0.05\)). In orange juice, however, the effectiveness of _E. coli_ and _Salmonella_ reductions between 4 \({}^{\circ}\)C and ambient temperature did not differ substantially. These results were statistically insignificant (\(p>0.05\)). Also, the type of juice (apple cider or orange juice) did not alter the results [70]. In surfaces such as wheat, ozone levels (0-20 \(\upmu\)g m = 0-120 ppb \(v/b\) 7 h per day)\({}^{-3}\) degraded the leaf pigments prematurely [71].