Biofouling prevention with a pulsed discharge

The effects of shockwaves in water on biofouling were explored. Shockwaves were generated by a pulsed high-voltage arc discharge. This apparatus is composed of a pulsed high-voltage power and a submerged electrode. The power supply generates up to 5 kJ of pulsed energy with a peak current of 20 kA at 5 kV. A field test on biofouling prevention was conducted with four test loops: one with no treatment (control) and others with treatment (pulsed discharge and continuous/pulsed injection of NaClO). Each loop contains three segments with various flow rates (1.1 m/s, 1.8 m/s, and 3.0 m/s). First, we measured voltage/current waveforms with tap water and salt water, then shockwave intensity at the upper and lower sides of the control loop. After a two- month period, a thick sludge film and many small barnacles were found on the 1.1 m/s and 1.8 m/s flow rate pipe surfaces of the control loop, however, only a thin sludge film and no barnacles were found in the pulsed discharge loop. Furthermore, few barnacles and no sludge were found in the pulsed NaClO injection loop of the 1.1 m/s and 1.8 m/s flow rate pipes of the pulsed injection loop. There was no biofouling in the continuous NaClO injection loop and in all 3.0 m/s rate pipes.