Temporary immobilization of aquatic nuisance species through application of short electric pulses has been explored as a method to prevent biofouling in cooling water systems where untreated lake, river, or sea water is used. In laboratory experiments, electrical pulses with amplitudes on the order of kilovolts/centimeter and submicrosecond duration were found to be most effective in stunning hydrazoans, a common aquatic nuisance species. Varying pulse amplitude and repetition rate allows us to control the stunning time in a temporal range from minutes to hours. The temporary immobilization is assumed to be caused by reversible membrane breakdown. This assumption is supported by results of measurements of the energy required for stunning. Based on the data obtained in laboratory experiments, field experiments in a tidal mater environment have been performed. The flow velocity was such that the residence time of the aquatic nuisance species in the system was approximately half a minute. The results showed that the pulsed electric field method provides full protection against biofouling when pulses of 0.77 /spl mu/s width and 6 kV/cm amplitude are applied to the water at the inlet of such a cooling water system. Even at amplitudes of 1 kV/cm, the protection is still in the 90% range, at an energy expenditure of 1 kWh for the treatment of 60 000 gallons of water.
[1]
K. Schoenbach,et al.
Effect of pulsed electric fields on micro-organisms: experiments and applications
,
1995,
Digest of Technical Papers. Tenth IEEE International Pulsed Power Conference.
[2]
W. Hamilton,et al.
Effects of high electric fields on micro-organisms. 3. Lysis of erythrocytes and protoplasts.
,
1968,
Biochimica et biophysica acta.
[3]
K. Schoenbach,et al.
The effect of pulsed electric fields on biological cells: experiments and applications
,
1997
.
[4]
Kenneth S. Cole.
Electric impedance of marine egg membranes
,
1937
.
[5]
K. Schoenbach,et al.
Biofouling prevention with pulsed electric fields
,
1996,
Proceedings of 1996 International Power Modulator Symposium.
[6]
R. Benz,et al.
Dependence of the Electrical Breakdown Voltage on the Charging Time in Valonia Utricularis
,
1980
.