High voltage impulse electric fields: Disinfection kinetics and its effect on membrane bio-fouling

A high voltage impulse (HVI) technique was applied for the control of membrane bio-fouling caused due to the filtration of microorganisms. Escherichia coli was used as a model microorganism for membrane filtration. The death rate of the cells increased with increasing electric fields (E) strength from 5 to 20 kV/cm. In particular, the cell numbers decreased from 3.7 x 10(5) to 2.5 x 10(3) CFU/ml (99.3% reduction) when subjected to an HVI of 20 kV/cm for 60 min. The model equation for HVI disinfection; E-1.94 t = 1.3 x 10(4), was obtained by plotting the contact time (t) vs. E for 2-log removal (99% reduction) of microorganisms. E. coli Suspensions, both with and without HVI induction, were filtered through an ultrafiltration membrane to verify if the HVI enhanced the filtration performance. The flux of the suspension subjected to HVI was constantly maintained throughout the entire filtration period; whereas, that of the control (without HVI induction) abruptly decreased after the onset of membrane filtration. The main reason for the improved flux was the reduced cake resistance (R-c) as a result of the increased cell particle sizes after HVI induction. E coli cells became coagulated after being subjected to HVI and; thus, the particle size increased. The HVI system could be used as an alternative method for the control of membrane bio-fouling. (C) 2011 Elsevier B.V. All rights reserved.