Inactivation of Salmonella spp. by Low-Frequency Electric Fields in Sewage Sludge

The treatment of the sewage sludge produced in the biological treatment plants have increasingly become a serious problem. For this reason, when the reuse and the disposal of the sludge are taken into consideration, the pathogens that the sludge contains should be seriously reduced. In this study, as an alternative to traditional treatment methods for the purpose of pathogen inactivation in sewage sludge, AC electric field, which is a non-thermal technology, was used. The electric field energy designed for the inactivation of the microorganisms in the sewage sludge affects directly the pores in the cell wall in a physical manner. In order to evaluate the inactivation effect of the electric field, AC electric field (50 Hz, 0,6 -1,2kV cm-1) was applied to the sewage sludge containing Salmonella spp. and Salmonella typhimurium. It was observed that Salmonella spp. population reduced 1.4 log in 0.6 kVcm-1, 1.1 log in 1.2 kV cm-1and S. typhimurium reduced 0.5 log in pure culture. The results showed that the electric field treatment increased the transmittance of the cell wall and that caused destructions in the cell membranes. Index Term— AC electric field, pathogen inactivation, sewage