Study on application of shock waves generated by micro bubbles to the treatment of ships’ ballast water

Abstract

This paper reports the fundamental study for development of a ships’ ballast water clarifying treatment technology using shock pressures generated by the collapse of micro bubbles. From the microscopic observation, it was confirmed that micro bubbles less than 65 μm in diameter became small in size and disappeared, and the shock wave generation by their collapse was observed by optical visualization method and pressure sheets. The bio-experiments using a marine Vibrio sp. were carried out under the three conditions: (1) only use of micro bubbles, (2) only use of 20 kHz ultrasonic waves, and (3) simultaneous use of them. The number of survival cells was investigated under the respective conditions for 12 hours. The inactivation effect on the marine Vibrio sp. by simultaneous use of micro bubbles and ultrasonic waves indicated better inactivation than that by the only use of micro bubbles or ultrasonic waves.