US takes step to recognising MPN ballast viability test

Sarah Carter
Sarah Carter

16 November 2018


This week the US Senate gave its approval to a bill aimed at recognising the Most Probable Number (MPN) test for determining the viability of ballast water treatment systems.

On 14 November the USCG Authorization Act was passed by the Senate with the Vessel Incidental Discharge Act (VIDA). The VIDA Bill includes legislative language that amends the USCG regulations to allow for the use of reproductive methods for the testing and approval of ballast water management systems. The amendments explicitly expand the definition of “living” to ensure that organisms that cannot reproduce (nonviable) are not considered to be living. Basically, organisms that cannot reproduce are as good as dead for the purposes of the regulation.

The effect is that the USCG is required to develop a draft policy letter detailing reproductive methods based on best available science and the it must consider Type Approval testing methodologies that utilise organism grow-out and MPN analysis to determine the number of viable organisms in ballast water that are capable of reproduction.

Most of the UV ballast systems approved under IMO rules have used the MPN to determine effectiveness but this method was previously determined by the US authorities to not meet their requirements and an alternative ‘vital stain’ test was required.

The VIDA Bill will now move on to Congress for a vote. If passed by the US House of Representatives, it would then be signed into law by the President of the United States.