Use of the Filter-Sandwich carriers in continuous effectiveness monitoring of slurry treatment methods as an element improving biosafety in agriculture

Slurry, due to high microbiological contamination, requires hygienization before spreading. The agricultural usage of treated slurry has to guarantee biosafety. Therefore, constant monitoring of the slurry treatment process should be conducted. The use of Filter-Sandwich carriers seems to be a prospective solution. The aim of the research was to test whether Filter-Sandwich carriers influence the survivability of microorganisms during the slurry hygienization process and hence, whether they are safe for the environment. Raw cattle and swine slurry with different dry matter content was the research material. Salmonella Senftenberg W775 rods were introduced directly into the slurry and into the carriers placed in the liquid excrements stored at 4 and 20 °C, and underwent anaerobic digestion at 35 °C. The number of tested bacteria obtained from the slurry and carriers was determined using the MPN method with proper microbiological media. The values of physicochemical parameters of the raw and treated slurry were determined, both for the carriers and for slurry only. Biosafety control was also conducted for the carriers in slurry containers. The differences in the theoretical survivability between Salmonella Senftenberg W775 re-isolated from the slurry and the carriers, and in the values of the selected physicochemical parameters obtained at the end of the process, were not statistically significant. The re-contamination of the sterile slurry caused by the bacteria in the carrier was not observed after placement of the carrier with inoculated material. The conducted research proves the usefulness of Filter-Sandwich carriers for continuous hygienization monitoring of the slurry treatment process. This refers not only to the semi-technical scale, but also to the full-scale process.