Date of Award

Summer 1998

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Electrical & Computer Engineering

Committee Director

Karl H. Schoenbach

Committee Member

Vishnu K. Lakdawala

Committee Member

Linda L. Vahala

Committee Member

Fred C. Dobbs

Abstract

Clinical and theoretical evidence indicate that electric fields have biological effects ranging from recoverable disturbance to mortality induction depending on the field parameters and time of exposure. In this thesis, the effect of electrical field in pulsed form on aquatic nuisance species is investigated. Pulse parameters in terms of amplitude, width, shape, and repetition rate that stimulate the species to desirable levels are to be defined. Applying the electrical pulses with appropriate parameters to stun aquatic nuisance species entering marine cooling systems will prevent it from attaching to pipe walls. The use of electrical fields to seek efficient, environmentally friendly, and inexpensive solution for the biofouling problem is studied.

Laboratory experiments were performed on a "representative" species, the hydrozoan Stylactis arge, to achieve parameter optimization. In these experiments, four pulse generators were used to generate electric field strength of 100 V/cm to 20 kV/cm, with pulse width of 300 ns to 15 μs. Two field experiments were constructed to validate the idea of using the electric field in biofouling prevention.

Laboratory experiments showed that a combination of electric field strength and energy density is the crucial factor that determines the stunning duration. It was found that a sub-lethal pulse could be effective if repeated. Repetition rate was shown to be an important parameter to gain cumulative effects of successive pulses. It was also concluded that semiconductor technology can not provide simple pulsers for the application of biofouling prevention; rather, gas tube or magnetic switches should be used for large field systems. Field experiments confirmed the laboratory observations. Electric fields of 12 kV/cm and 6.45 kV/cm at pulse width of 770 ns were able to prevent biofouling in salt water with an efficiency of 100% with a consumption of 1200 Gal/kWh. The fresh water trial, currently running, showed a promising start.

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DOI

10.25777/v176-6r67

ISBN

9780599059450

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