Critical Comparison between the Pulsed Electric Field and Thermal Decontamination Methods of Hospital Wastewater

Filtered wastewater samples were inoculated with Enterococcus faecium and exposed to different pulsed electric field (PEF) treatment energies at 40, 50 and 60°C. A lethal effect of heat treatment on E. faecium can be observed for T > 56°C and a heating duration of 4 min. A treatment with 60°C, 4 min, provokes a bacterial reduction of 4 log. A combined treatment of inoculated wastewater samples with pulsed electric field and heat (40, 50 and 60°C) reduced the bacterial contamination considerably. At a suspension temperature of 60°C pulsed electric field inactivation resulted in a complete bacterial decontamination (8 log reduction rate). Moreover, it was demonstrated that naturally occurring nuclease activities were not changed by the pulsed electric field treatment. In contrast to a thermal treatment with temperature over 72°C, for 4 min., the nuclease activity was reduced up to 90%. In this case, inactivation is only 4 log. The same inactivation rate can be obtained by a combination of heat treatment (60°C) and pulsed electric field treatment (30 J/ml).