Who’s Affected

The USCG’s decision to reject the MPN method will negatively impact shipowners, the environment and supporters of ecosystem protection, legislators, international policymakers, marine consultants, and concerned citizens. Here’s how:


The rejection of the MPN method restricts the use of well-developed ballast water management systems that are acceptable under the IMO BWM Convention and are already in use by thousands of ships throughout the world. If the USCG’s position is maintained, low-energy UV-based systems cannot practicably achieve USCG Type Approval and the options available for shipowners will be greatly diminished, as roughly half of the system suppliers in the market today will be eliminated. In addition – without a practical, energy-efficient UV-based solution available for those owners seeking USCG Type Approved systems – the capital, installation and operating costs of ballast water management systems for many vessel types will sharply increase.

Shipowners are now in the undue position of having to accommodate an approaching installation schedule as the IMO BWM Convention nears entry into force, with few USCG Type Approved systems available, and no low-energy UV-based options that are capable of treating poor quality water at ports throughout the world.

The Environment

The Nonindigenous Aquatic Nuisance Prevention and Control Act of 1990 (NANPCA) and National Invasive Species Act of 1996 (NISA) require the Secretary of Homeland Security (and therefore the USCG) to ensure to the maximum extent practicable that aquatic invasive species are not introduced into U.S. waters. The USCG’s ruling against the MPN method has unnecessarily rejected the use of proven technologies, testing and monitoring protocols that can meet this mandate. It leaves the U.S. with few (and no low-energy UV-based) Type Approved ballast water management systems. This decision eliminates the practical application of a safe, established, and green UV treatment technology and favors chlorine-based solutions which increase environmental risk due to potential for chlorine discharge and disinfection by-products effects (more citations here).


As a result of the USCG’s ruling against the MPN method, the shipping industry now faces unnecessary uncertainty that could impede economic progress and delay the use of environmentally friendly technology. Even more so than other industries, the shipping industry is truly global and heavily reliant upon uniform standards to both protect the environment and allow unencumbered trade. Without consistent international regulations, vessels equipped to trade in U.S. waters will likely bear higher capital costs than those vessels not operating in U.S. waters (and such costs may be passed on to U.S. consumers). The USCG claims that its ruling is consistent with its regulations, authorized by the NANPCA, as amended by the NISA. Surely, when these laws were enacted, Congress did not intend to make USCG Type Approval of ballast water management systems incompatible with international standards, or impracticable in terms of meeting the goal of preventing the spread and infestation of ecosystems by aquatic invasive species.

International Policy Makers

The shipping industry is truly global and heavily reliant upon uniform standards to both protect the environment and allow unencumbered trade. It is critical that international ballast water management standards and implementation, particularly the IMO Guidelines and USCG Final Rule, are consistent and global. This will enable streamlined management and enforcement. The USCG’s rejection of the MPN method, and subsequently, of the first three Type Approval applications is based on a unique interpretation that may restrict the use of well-developed ballast water management systems that are acceptable under the IMO BWM Convention and are already in use by ships throughout the world.

While the USCG maintains that the U.S. discharge standard is “equivalent to the IMO discharge standard” (77 FR 17254 at 17262 and 17291), the IMO relies on culture-based methods, such as MPN, to ensure the biological efficacy of ballast water management systems. Furthermore, entities responsible for assessing compliance with the IMO BWM Convention standards (i.e., Class Societies) rely on the MPN method.

Marine Consultants

Shipowners need compliant solutions that meet the unique needs of their vessels. The USCG’s decision on the MPN method essentially eliminates the practical use of UV treatment technologies. Instead of approving the available, energy-efficient systems, the USCG has suggested that UV-based systems utilize the vital stain method to measure treatment system efficacy. If UV-based systems use vital stains to measure UV treatment system efficacy, they will need to be designed to use dramatically more energy to increase the UV dose and/or be restricted to be used with high-quality water or treat only certain types of organisms. Given similar water quality and influent organism characteristics, these systems will require a minimum of 10 times more electrical power and hence a 10-fold increase in carbon emissions. Operational limitations are also not feasible because they would limit travel only to ports with high water quality or certain types of organisms, and dramatic reductions in ballast water flow rate would significantly impact a vessel’s cargo operations. Eliminating low-energy UV will also leave shipowners with few, if any, cost-effective options for treating fresh water. Uniform and consistent standards, particularly between the IMO and USCG, will reduce unnecessary compliance risks associated with interpreting and conforming to these standards.

Concerned Citizens

It serves the entire marine industry to allow best available technologies to economically and environmentally achieve the regulatory requirements to safeguard our waters. However, the USCG’s decision to not allow the use of the MPN method essentially eliminates the practical application of safe, green, low-energy UV-based treatment technology and favors the use of chlorine- and chemical-based solutions. This will have significant adverse economic and environmental consequences in the U.S. and internationally.

Delacroix, S., Vogelsang, C., Tobiesen, A., Liltved H. (2013). Disinfection by-products and ecotoxicity of ballast water after oxidative treatment–results and experiences from seven years of full-scale testing of ballast water management systems.

Gonsior, M. et al (2015). Bromination of Marine Dissolved Organic Matter Following Full Scale Electrochemical Ballast Water Disinfection. Environmental Science & Technology, DOI : 10.1021/acs.est.5b01474. 

Helmholtz Zentrum Muenchen – German Research Centre for Environmental Health (2015).

Shah, A.D., Liu, Z., Salhi, E., Höfer, T., Werschkun, B., von Gunten, U. (2015). Formation of disinfection by-products during ballast water treatment with ozone, chlorine, and peracetic acid: influence of water quality parameters.

Werschkun, B., Sommer, Y., Banerji, S (2012). Disinfection byproducts in ballast water treatment: An evaluation of regulatory data. Water Research. 46: 4884-4901. Doi:10.1016/j.watres.2012 .05.034.

Effect Change

Together with concerned citizens, environmental groups, shipowners, marine organizations, and manufacturers, let’s urge the USCG to reconsider its decision.

Send a letter to the USCG