Veterinary antibiotics are widely used at concentrated animal feeding operations (CAFOs)
to prevent disease and promote growth of livestock. However, the majority of antibiotics
are excreted from animals in urine, feces, and manure. Consequently, the lagoons used to
store these wastes can act as reservoirs of antibiotics and antibiotic-resistant bacteria.
There is currently no regulation or control of these systems to prevent the spread of these
bacteria and their genes for antibiotic resistance into other environments. This study was
conducted to determine the disinfection potential of chlorine, ultraviolet light and ozone
against swine lagoon bacteria. Results indicate that a chlorine dose of 30mg/L could
achieve a 2.2–3.4 log bacteria reduction in lagoon samples. However, increasing the dose of
chlorine did not significantly enhance the disinfection activity due to the presence of
chlorine-resistant bacteria. The chlorine resistant bacteria were identified to be closely
related to Bacillus subtilis and Bacillus licheniformis. A significant percentage of lagoon
bacteria were not susceptible to the four selected antibiotics: chlortetracycline, lincomycin,
sulfamethazine and tetracycline (TET). However, the presence of both chlorine and TET
could inactivate all bacteria in one lagoon sample. The disinfection potential of UV
irradiation and ozone was also examined. Ultraviolet light was an effective bacterial
disinfectant, but was unlikely to be economically viable due to its high energy
requirements. At an ozone dose of 100 mg/L, the bacteria inactivation efficiency could
reach 3.3
3.9 log.