The application of aeration and ozonation for E. coli inactivation in dairy manure slurry

Dairy industry is important for milk production and has substantial contribution to the California's economy. Dairy manure contains carbon, nitrogen and phosphorus, which are beneficial to soil, however, dairy farms also produce manure, which impacts environment negatively, and manure-borne pathogens poses risks to public and animal health. In this research, a lab scale experiment was designed and a series of experiments were conducted to determine the impact of ozone and air injection on E. coli inactivation in liquid manure. Liquid manure was exposed to ozone and air for multiple durations (0 min, 60 min, 120 min, and 240 min) and E. coli levels were determined. Further, manure samples were analyzed for pH, salt content, potassium (K⁺), sodium (Na⁺), nitrate (NO3⁻), calcium (Ca2⁺), and electrical conductivity (EC, mS/cm). Results showed that Ozonation can be an effective treatment method to reduce E. coli levels in liquid manure. Further nitrate ions were reduced substantially by Ozonation. The analysis of variance (one way and two way) revealed significance difference in E. coli and nitrate reductions in liquid slurry among ozone and air treatments (p < 0.05). The study's results carry significance importance in terms of developing a simple field-scale method for reducing microbial and nutrient pollutions from dairy lagoon manure.