Vessels sailing in U.S. waters are required to adhere with USCG ballast water discharge standards and regulations, and will ultimately have to be equipped with a USCG Type Approved system. Today, ballast water management systems must undergo testing according to the Environmental Technology Verification (ETV) Protocol, which contains assessment procedures to evaluate the performance characteristics of commercial-ready treatment technologies, including biological treatment performance.
To measure the efficacy of treatment systems, the ETV Protocol employs a staining method (FDA/CMFDA) that tests for the presence of enzymatic activity as a proxy for whether organisms in the water appear to have been treated to the point of immediate death. This vital stain method is not a definitive measure of live/dead status, as it measures one of the seven characteristics of life.
In contrast, the IMO and entities responsible for assessing compliance with the IMO BWM Convention standards (Class Societies) rely on culture-based methods, such as MPN, to ensure biological efficacy of ballast water management systems. Some of these same Class Societies have been approved as Independent Laboratories by the USCG to perform testing to support Type Approval applications.
The MPN method measures the ability to reproduce, while the vital stain method measures the ability to metabolize. If organisms cannot reproduce, they cannot grow in number, colonize or otherwise infest or invade U.S. waters.