Biofouling prevention with pulsed electric fields

The clogging of pipes due to biofouling organisms capable of rapid population growth is a major problem in cooling systems where untreated lake, river or sea water is used. In estuarine and marine ecosystems, it is blue mussels and barnacles which cause biofouling problems; in freshwater ecosystems the uncontrolled growth of zebra mussels has significant economic implications. In order to explore the preventive effect of pulsed electric fields on biofoulants, the authors have, following laboratory studies, performed field tests with a pulsed power system which was to designed to provide /spl mu/s pulses of up to 40 kV into a low impedance (<10 /spl Omega/) load. The system was used to treat water from the Elizabeth River in Norfolk, USA. Two tests, each performed over a period of three weeks with pulsed electric fields of 12 kV/cm, and 6.4 kV/cm, respectively, in the treatment cell have demonstrated the feasibility of the electric field method for biofouling prevention. Whereas strong growth of barnacles, blue mussels and hydrazoans was seen in the control system, the test system was completely free of these biofoulants. The highest efficiency reached so far was 1,400 gallons of treated tidal water per kWh of electrical energy. It is expected that the efficiency can be further increased by optimizing the effect with respect to pulse duration and electric field, and by concentrating on fresh water biofoulants, such as zebra mussels.