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12/14/2015: Coast Guard decision on use of Most Probable Number method

Today, the Coast Guard’s Marine Safety Center informed four ultraviolet ballast water management system, or BWMS, manufacturers that the Most Probable Number, or MPN, method is not considered as an equivalent alternative to the testing method prescribed in the Coast Guard’s regulations pertaining to the type approval of ballast water systems.

A Coast Guard review concluded that the MPN test method is not equivalent because it does not measure the efficacy of the BWMS to the performance standard required by the regulations. The regulations specifically require ballast water treatment systems to be evaluated based on their ability to kill certain organisms. Since the proposed MPN method assesses the viability of an organism to colonize after treatment, it measures to a different standard than that required by the regulations.

In the Preamble to the Final Rule which implemented the ballast water discharge standard and the procedures for BWMS type-approval, the distinction between live/dead and viable/unviable was evaluated, explicitly discussed and the decision was made to use live/dead as the standard for evaluating the performance of BWMS (See 77 FR 17254, at 17266). Since the MPN method does not measure performance to this standard, it is not an equivalent evaluation or test under the provisions of 46 C.F.R. § 162.060-10(b)(1).

The Coast Guard is aware of other ultraviolet BWMS, which are undergoing evaluation using the prescribed tests. As such, the tests required by the regulations and the Environmental Protection Agency’s Environmental Technology Verification, or ETV, Protocol are applicable and practicable for the evaluation of all systems.

As with all decisions made under the authority of Title 46 of the Code of Federal Regulations, this Marine Safety Center ruling is subject to appeal by the manufacturers. The Coast Guard will continue to evaluate this method through the ETV Technical Panel.

To view the response letters to the four BWMS manufacturers, visit Homeport:

Environmental – Ballast Water Management Program – Type Approval – “Marine Safety Center Ruling on Most Probably Number (MPN)”

This blog is not a replacement or substitute for the formal posting of regulations and updates or existing processes for receiving formal feedback of the same. Links provided on this blog will direct the reader to official source documents, such as the Federal Register, Homeport and the Code of Federal Regulations. These documents remain the official source for regulatory information published by the Coast Guard.









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