Ballast water may be taken onboard by ships for stability and can contain thousands of aquatic or marine microbes, plants and animals, which are then carried across the globe. Untreated ballast water released at the ship’s destination could potentially introduce a new invasive marine species. Hundreds of such invasions have already taken place, sometimes with devastating consequences for the local ecosystem.
The International Convention for the Control and Management of Ships’ Ballast Water and Sediments (BWM Convention) was adopted in 2004 to introduce global regulations to control the transfer of potentially invasive species. With the treaty now in force, ships need to manage their ballast water.
Since the introduction of steel-hulled vessels, water has been used as ballast to stabilize vessels at sea. Ballast water is pumped in to maintain safe operating conditions throughout a voyage. This practice reduces stress on the hull, provides transverse stability, improves propulsion and manoeuvrability, and compensates for weight changes in various cargo load levels and due to fuel and water consumption.
While ballast water is essential for safe and efficient modern shipping operations, it may pose serious ecological, economic and health problems due to the multitude of marine species carried in ships’ ballast water. These include bacteria, microbes, small invertebrates, eggs, cysts and larvae of various species. The transferred species may survive to establish a reproductive population in the host environment, becoming invasive, out-competing native species and multiplying into pest proportions.
Scientists first recognized the signs of an alien species introduction after a mass occurrence of the Asian phytoplankton algae Odontella (Biddulphia sinensis) in the North Sea in 1903. But it was not until the 1970s that the scientific community began reviewing the problem in detail. In the late 1980s, Canada and Australia were among countries experiencing particular problems with invasive species, and they brought their concerns to the attention of IMO’s Marine Environment Protection Committee (MEPC).
The problem of invasive species in ships’ ballast water is largely due to the expanded trade and traffic volume over the last few decades and, since the volumes of seaborne trade continue to increase, the problem may not yet have reached its peak yet. The effects in many areas of the world have been devastating. Quantitative data show that the rate of bio-invasions is continuing to increase at an alarming rate and new areas are being invaded all the time.
The spread of invasive species is now recognized as one of the greatest threats to the ecological and the economic well being of the planet. These species are causing enormous damage to biodiversity and the valuable natural riches of the earth upon which we depend. Direct and indirect health effects are becoming increasingly serious and the damage to the environment is often irreversible.
Ballast Water Convention
The Convention requires all ships to implement a ballast water management plan. All ships have to carry a ballast water record book and are required to carry out ballast water management procedures to a given standard. Parties to the Convention are given the option to take additional measures which are subject to criteria set out in the Convention and to IMO guidelines.
Several articles and regulations of the BWM Convention refer to guidelines to be developed by the Organization and Conference resolution 1 invited IMO to develop these guidelines as a matter of urgency and adopt them as soon as practicable and, in any case, before the entry into force of the Convention, with a view to facilitate global and uniform implementation of the instrument.
Dealing with Ballast Water
Ballast water is routinely taken on by ships for stability and structural integrity. It can contain thousands of aquatic microbes, algae and animals, which are then carried across the world’s oceans and released into ecosystems where they are not native.
Untreated ballast water released at a ship’s destination could potentially introduce new invasive aquatic species. Expanded ship trade and traffic volume over the last few decades has increased the likelihood of invasive species being released. Hundreds of invasions have already taken place, sometimes with devastating consequences for the local ecosystem, economy and infrastructure.
The Ballast Water Management Convention requires all ships in international trade to manage their ballast water and sediments, according to a ship-specific ballast water management plan. All ships must carry a ballast water record book and an International Ballast Water Management Certificate.
All ships engaged in international trade are required to manage their ballast water so as to avoid the introduction of alien species into coastal areas, including exchanging their ballast water or treating it using an approved ballast water management system.
Initially, there will be two different standards, corresponding to these two options.
The D-1 standard requires ships to exchange their ballast water in open seas, away from coastal waters. Ideally, this means at least 200 nautical miles from land and in water at least 200 metres deep. By doing this, fewer organisms will survive and so ships will be less likely to introduce potentially harmful species when they release the ballast water.
D-2 is a performance standard which specifies the maximum amount of viable organisms allowed to be discharged, including specified indicator microbes harmful to human health.
New ships must meet the D-2 standard from today while existing ships must initially meet the D-1 standard. An implementation timetable for the D-2 standard has been agreed, based on the date of the ship’s International Oil Pollution Prevention Certificate (IOPPC) renewal survey, which must be undertaken at least every five years.
Eventually, all ships will have to conform to the D-2 standard. For most ships, this involves installing special equipment.
Ballast water treaty amendments enter into force
Amendments to an international treaty aimed at preventing the spread of potentially invasive species in ships’ ballast water entered into force on 13 October 2019.
Ships regularly take on sea water, in tanks, to ensure their stability. Known as ballast water, this can contain many aquatic species, including in microscopic or larval form. These can become invasive and harmful if the ballast water is released, unmanaged, in a new location at the end of an ocean voyage.
The International Convention for the Control and Management of Ships’ Ballast Water and Sediments, 2004 (the BWM Convention) was adopted by IMO to address this problem.
The BWM Convention entered into force in 2017. The amendments formalise an implementation schedule to ensure ships manage their ballast water to meet a specified standard (“D-2 standard” – see above) aimed at ensuring that viable organisms are not released into new sea areas, and make mandatory the Code for Approval of Ballast Water Management Systems, which sets out how ballast water management systems used to achieve the D-2 standard have to be assessed and approved.
This will help ensure that aquatic organisms and pathogens are removed or rendered harmless before the ballast water is released into a new location – and avoid the spread of invasive species as well as potentially harmful pathogens.
The amendments to the BWM Convention were adopted in April 2018. In essence, the schedule for implementation means that compliance with the D-2 standard set out in the Convention will be phased-in over time for individual ships, up to 8 September 2024. Over time, more and more ships will be compliant with the D-2 standard.
In many cases, meeting the D-2 standard will be achieved through fitting ballast water management systems. There are now many such approved systems on the market, ranging from those which use physical methods such as ultraviolet light to treat the ballast water, to those using active substances (chemicals). Those that use active substances have to go through a thorough additional approval process.
Other amendments to the BWM Convention entering into force on 13 October 2019 relate to survey and certification.
The BWM Convention – D-2 standard
The D-2 standard specifies that ships can only discharge ballast water that meets the following criteria:
► less than 10 viable organisms per cubic metre which are greater than or equal to 50 micrometres in minimum dimension;
► less than 10 viable organisms per millilitre which are between 10 micrometres and 50 micrometres in minimum dimension;
► less than 1 colony-forming unit (cfu) per 100 millilitres of Toxicogenic Vibrio cholerae;
► less than 250 cfu per 100 millilitres of Escherichia coli; and
► less than 100 cfu per 100 millilitres of Intestinal Enterococci.
All ships must have a ship-specific ballast water management plan and keep a ballast water record book. Ships are also required to manage their ballast water to meet either the D-1 ballast water exchange standard or the D-2 performance standard. The amendments in force from 13 October 2019 formalise the implementation schedule for the transition from the D-1 to the D 2 standard.
Ballast Water Treatment Systems (BWTS)
Ballast Water Treatment System (BWTS) is a system designed to remove and destroy/inactive biological organisms (zooplankton, algae, bacteria) from ballast water. Ballast water treatment is still evolving technology with an ever-growing number of manufacturers. This means that there is limited inservice experience for the systems being offered and there is a general understanding that no single system is suitable for all ship types
The system is a two stage approach with filtration followed by disinfection using ultraviolet light. Upon uptake, seawater is first passed through an automatic backwashing filter (1st stage). The filtered seawater then passes through a UV chamber (2nd stage) where ultra-violet light is used to disinfect the water before entering the ballast tank.
On discharge, water from the ballast tank is pumped through the UV chamber for a second time to complete the disinfection process prior to discharge.
Upon uptake the sea water is first passed through a automatic backwashing filter (1st stage), and then filtered water passes through a static mixer, where disinfectant generated from the side stream EC Cell Module (2nd stage) is injected to ensure a maximum dose of 10ppm in the treated ballast water prior to entering the ballast tank. At discharge, water from the ballast tanks by-passes the filter and residual concentration of disinfectant is monitored. If required, treated ballast water is neutralized, ensuring compliance with MARPOL discharge limits.