Ballast Water Management: History, Application, and Legislation

There's Water, Then There's Ballast Water

Ballast is weights added to a ship to improve stability, balance, and trim.  In the past, this was often rocks found nearby a port.  For flexibility, ships today pump water in and out of tanks as ballast – Ballast Water.  Ballast water is taken onboard when cargo is unloaded and discharged when cargo is loaded or can be added for extra stability in foul weather.

By example, the container vessel Emma Mærsk, built in 2013, carries over 11,000 standard containers each weighing up to 20 tons and has 60,000 cubic meters (15.8 million gallons) of tank capacity set aside for ballast water.  As the cargo is offloaded, that weight is replaced with a like quantity of ballast water.  When the ship arrives at another port for loading, the ballast water is pumped from the tanks.  In this way, water is transported from one locale and released in another. However, ballast water contains more than just plain water. When ballast water is taken into a ship, so are local species.

Zebra Mussel (QUAGGA)
Figure 1 – A Zebra Mussel.









When the ship travels to it's loading port, these species are discharged along with the ballast water. The environmental conditions are similar for port to port, but the natural predators are not.  Since ports are often located at the mouths of rivers and in bays where plentiful nutrients support hardy species, populations of a new species can grow to invasive levels.  Good examples are the zebra mussels in the Great Lakes, Quagga mussels on the West Coast, mitten crabs in the San Francisco Bay, and the blue crab in Northern Europe.  Whether it is along a seaboard or across an ocean, the release of ballast water brings unintended consequences.


The worldwide extent of the unintended transport of invasive species has become a focal point for environmental legislation. National governments are inclined to limit the movement of non-indigenous species throughout the world. In 2004, the delegates to the International Maritime Organization (IMO) drafted a set of regulations for the control of the movement of invasive species known as the International Convention for the Control and Management of Ship’s Ballast Water and Sediment, or Ballast Water Management Code (BWM Code). 

The BWM Code provides two primary regulations intended to reduce the transport of invasive species: “Regulation D-1, Ballast Water Exchange” and “Regulation D-2, Ballast Water Treatment.” Regulation D-1 seeks to reduce invasive species by flushing the majority of them out before arriving at a different port. Regulation D-2 requires the installation of new shipboard systems to remove invasive species to specified levels. The systems of Regulation D-2 are to be verifiable, record operational time, note instances when bypassed, and allow for sampling of the treated ballast water (effluent). 

At its inception, the BWM Code was to go into effect when it had been ratified by at least 30 countries with 35% of the world’s tonnage. On September 9, 2016, Finland ratified the BWM Code, bringing the Convention into force with 52 nations and 35.14% of the world’s tonnage in agreement.

Organism Figure
Figure 2 – Table of Allowable Discharge Standard, Regulation D-2.

Along with the BWM Code, the United States government – in this case, the United States Coast Guard (USCG) – has given consideration to the impact of invasive species.  The USCG issued a final rule on their position in November 2015 – applying Regulation D-2 standards but on a different time table.  Figure 3 is a table of the implementation dates for both the IMO BWM Code and the USCG interpretation. 

Ballast Capacity Figure
Figure 3 – Table of Implementation Dates for the IMO BWM Code and the USCG Interpretation: There will be three (3) instances where ships will need to comply immediately with the BWM Code – these are dates in Figure 3 without an asterisk.  Upon ratification of the BWM Code, an agreement was reached to allow 1 year grace for instances where the vessel has not yet fitted a D-2 compliant system  - until September 9, 2018.  In the instance where the USCG date of implementation differs from the IMO date, a situation can exist where the ship can be fitted with an IMO approved treatment system which has not yet passed the USCG approval process; that ship will be non-compliant if discharging ballast in the United States and may be arrested.

The Technology to Outfit Ships

With deadlines for compliance approaching, there will be increased demand for these new technologies to be installed.  For instance, a ship with a ballast water capacity of 1400 cubic meters built 1969 would be required by the USCG and IMO to be retrofitted with a ballast water treatment system not later than 2021 (2016 implementation + 5 years maximum time between dry-docking).

Technologies for treatment systems which are currently showing promise include filtration with some type of sanitization – Ozone, ultraviolet irradiation, biocides, and hydrogen peroxide to name a few – along with a monitoring and control system.

The technology to treat ballast water is required to go through an approval process in order to be suitable for installation.  It is a three-stage process – theoretical analysis, controlled testing and onboard testing.  For the USCG acceptance of ballast water treatment, the controlled testing must be done at a facility approved by the USCG.

 As of September this year, 50 systems were in process through both the IMO and USCG testing cycles, with six (6) systems having been fully approved by the USCG.

Ballast water treatment systems will not offer a ‘one size fits all’ approach, as the system for a given ship will need to address that ship’s particular needs for through-put, total ballast capacity, duration of ballast retention, trade route and a myriad of other variables.

Now that the BWM Code has achieved international mandate, the pressure is on for system designers, operators, reviewers, and installers.