###### Abstract
There are various treatment methods such as composting and anaerobic digestion, which are used for treating animal waste [23; 24; 25]. Temperature-based treatment methods, such as composting, which produces high temperature (>55 \({}^{\circ}\)C) and thermophilic anaerobic digestion, were found to be suitable for reducing pathogens in animal waste [26; 27; 28]. In many instances, however, pathogens such as _E. coli_ O157:H7, _Salmonella_ spp., and _L. monocytogenes_ were present in compost organic waste [29; 30; 31; 32; 33] and animal-waste amended soil [34]. One possible reason for this could be that the composting process did not attain a high enough temperature for a sufficient duration [35; 36]. In addition to this, cross contaminations are also known to cause pathogen contamination in cross products [37; 38]. Because of pathogen survival issues in existing waste treatment methods, there is a growing demand to identify new technologies or improved methods capable of removing pathogens from waste such as dairy manure. Ozone treatment could be an option [39; 40]; however, further studies are needed prior to its widespread application in treating dairy waste. Ozone has been used to sanitize a number of products including food products and ozone treatment has been studied in various food and waste treatment industries. Ozone is used for treating sewage and killing harmful bacteria [41; 42; 43]. Application of ozone treatment for wastewater treatment at a pilot scale showed significant removal of contaminants such as pharmaceuticals, nitrate, and micropollutants [44; 45; 46]. Ozone treatment is considered a cost-effective, and eco-friendly method for the removal of various contaminations including mycotoxins in grain products [47], pharmaceutical removal from water [48], and contaminants removal in food products [49]. The triatomic form of oxygen (O\({}_{3}\)) [ozone] is detrimental to pathogens and bacteria in food products because of the strong oxidation property of ozone. Ozone is considered to be highly effective against bacteria in many products, even with a low concentration of ozone (0.01 ppm). Further, ozone treatment is an approved food additive by the U.S. Food and Drug Administration (US FDA), which facilitates its use for treating food products for the removal of bacteria, viruses, and protozoa [7; 39; 50; 51]. Ozone reduces microbial populations by 2-4 orders of magnitude and ozone treatment increases the shelf life of fruits and vegetables [22]. It has been found that _E. coli_ would be more readily killed by ozone in juices used for human consumption. Pathogens reductions in wastewater have been widely reported when wastewater was exposed to ozone [42]. Further, the effects of ozone on reducing the populations of _Salmonella_, _E. coli_ O157:H7, and _L. monocytogenes_ on the surface of the lettuce, spinach, and green onion were studied and results showed that pathogens populations were reduced substantially [52]. During ozone treatment, the survival of pathogen depends on the O\({}_{3}\) concentration and duration of exposure [53; 54]. In addition to time and concentrations, the effect of O\({}_{3}\) in pathogen reduction is influenced by the physicochemical characteristics of the material (i.e., water content, pH, microbial load, and organic matter content) [22; 53; 55; 56; 57]. Pathogens such as _E. coli_ and _Salmonella typhimurium_ in food products were reduced substantially after exposure to O\({}_{3}\)[51; 55]. The goal of this study was to understand the impacts of ozone on pathogen removal in dairy wastewater. Specific objectives of this study were: (1) to investigate the impacts of ozone concentrations and exposure time on _E. coli_ O157:H7 reductions; (2) to determine the impacts of ozone _S._ Typhimurium reductions; and (3) to understand the impacts of ozone on the degradation of organic content of manure.