Effects of voyage routing on the survival of microbes in ballast water

Abstract

This study examines the use of patterns of variation in voyage routing water temperature to lighten the burden of on board ballast water management. Experimental results from all six ships in this study indicate that total bacterial counts decreased during the first six days of the voyage, regardless of trends in temperature variation. The ability of temperature to maintain bacterial counts at a certain level was obvious when temperature continuously decreased to less than 15°C, or rose within the same range. The results of the bacterial analyses show that effective use of voyage routing yielding patterns of variations in water temperature may assist ballast water management in some cases. The testing regime in this study reveals the effects on causing increased mortality in the ballast water. Vessels undertaking long voyages should take advantage of temperature variation to control the growth of bacteria in ballast water. This method relies on abrupt variations in temperature over time, and requires the integration of other treatments such as deoxygenation.