Ballast Management: Treatment Technology
Current management strategies for preventing introductions via ballast water are limited to ballast water retention or open ocean exchange, which flushes ballast water from the initial port into the open ocean (where estuarine organisms are not likely to survive). However, due to the placement of intake and outflow pipes and ballast water tank configuration, not all ballast water is able to be replaced during ballast water exchange (see figure at bottom). The open ocean ballast water exchange efficiency has been documented to range from 75-95% of tank water, which is not enough to ensure that no species introductions will result from ballast water release.
Due to the limitations of open ocean exchange, regulatory agencies are pushing for the development of ballast water treatment systems that will remove or kill the organisms before they are discharged into port waters. Some promising technologies include one or a combination of the following: UV irradiation, hydrocyclone/centrifugation, filtration, ozonation, heat treatment, and some form of chlorination.
The United States Coast Guard is actively working to create a standard for ballast water treatment systems that could be adopted by federal and state regulatory programs (see Treatment Technology Approval Process page). Meanwhile, researchers and regulators are currently working to create a standard testing protocol for ballast water treatment systems so that different systems can be easily assessed and compared. A few experimental systems have been installed on ships and have undergone preliminary testing. Successful treatment development and testing requires a cooperative effort between researchers, regulatory agencies and ship owners. There have been several reports analyzing the viability of treatment technologies. The 2007 report by the California State Lands Commission (SLC) provides several tables that list treatment technology developers and give comparisons of the various technologies**:
For additional TT info, visit Treatment Technology R&D page.
**Please note: The SLC 2007 report only includes information through 2007; for any updates, please contact Nicole Dobroski at DobrosN@slc.ca.gov.