Onshore ballast water treatment stations : a harbour specific vector management proposition / by Lawrence A. Kuroshi.
Abstract
The discharge of Harmful Aquatic Organisms and Pathogens (HAOP) found in ships ballast water from one port environment to another can have severe ecological, environmental and economic consequences, especially when they transform into marine pests. This informs the necessity to investigate treatment options that could curtail the transfer of these organisms from a source harbour. An alternative to the conventional Ballast Water Treatment Systems is investigated and proposed in this study- it entails the onshore treatment of host port water before it is loaded as ballast water into ships. The study covered sampling of Port Harcourt Harbour water in Nigeria. The field samples were subjected to laboratory analysis. Inferential statistics was employed to determine the relationships between the physicochemical properties of sampling stations and organisms’ density. Literature on ballast water treatment research were reviewed, and the most viable treatment options for Port Harcourt Harbour based on the field results obtained were discovered to be treatment combinations that could remove most of the species found in the study area, especially; Alexandrium minutum, Acartia clausi, Pseudocalanus elongatus, Tortanus sp., and Oncaea sp., which are non-indigenous to North America; one of the Harbour’s leading trading regions in the world. A three stage shore treatment combination process was therefore, proposed by the study for employment in the Harbour. The first stage involves filtration of the harbour’s sea water to remove the larger organisms, mainly zooplankton. It is followed by a stage of heating of the harbour’s water (>38oC) to remove larger zooplanktons that have escaped the filtration process. The third stage shall involve the use of biocides-this entails the application of chemicals like ozone (which has a strong lethal effect on a lot of phytoplankton and bacteria). And finally, the treated sea water is pumped into the visiting ship as treated ballast water.