Inactivation of microorganisms by pulsed electric field treatment: the influence of pulse parameters on the inactivation rate

Abstract

For a bacterial decontamination of critical wastewater outlets like those from hospitals, conventional methods fail. In the presence of organic substances, ozonization or chlorination can produce toxic reagents. Also the penetration depth of UV radiation in thick water is insufficient.With regard to an industrial implementation of the pulsed electric field treatment technique the influence of the pulse parameters on the inactivation of Pm. putida and E. faecium was studied.The bacteria were suspended in diluted PBS-buffer at a conductivity of 0.2 Sm-1 and treated with rectangular pulses at a field strength of up to 125 kVcm-1. The duration of the pulses was varied between 100 ns and 10 µs. For an energy of 120 kJ/l delivered to the bacterial suspension a maximum inactivation rate of 3.6 log rates was observed when 1 µs, 100 kVcm-1 pulses were applied. The inactivation rate decreases for shorter pulse widths.Compared to unipolar pulses, the application of fast reversing bipolar pulses did not improve the killing rate.A high sampling size study involving exponential pulses of different decay time and rectangular pulses results in similar killing rates for both pulse shape types.