Learning objectives
- Explain the environmental problem of invasive species transported via ballast water.
- Distinguish between the Convention's D-1 and D-2 standards.
- Understand the general operation of a Ballast Water Management System (BWMS).
- Manage the required documentation (BWMP, Record Book, Certificate).
- Recognise the typical areas checked in a PSC inspection on ballast water.
The environmental problem of invasive species
Module objectiveRecognise how ballast water carries invasive species from one port to another and why a convention is dedicated to this risk.
Ships that take on ballast water for stability in one port and discharge it in another carry, along with the water, aquatic organisms, larvae and sediments that can survive the voyage and establish themselves in an entirely foreign ecosystem, with sometimes serious ecological and economic consequences.
The problem of invasive species transported by ballast water has been recognised as one of the main threats to global marine biodiversity, on a par with chemical pollution, which is why the international community developed a convention specifically dedicated to this risk.
Key takeaways
- Organisms, larvae and sediments taken on with ballast water can survive the voyage and establish themselves in a foreign ecosystem.
- Invasive species transported by ballast water are recognised as one of the main threats to global marine biodiversity.
- The international community developed a convention dedicated specifically to this risk.
The Ballast Water Management Convention
The BWM Convention was adopted on 13 February 2004 and entered into force on 8 September 2017. It is an IMO instrument distinct from MARPOL.
Application and certification
The Convention applies to ships entitled to fly the flag of a Party and ships operating under the authority of a Party, subject to Article 3 exclusions and determinations. Warships, naval auxiliaries and State ships used only on government non-commercial service are excluded; limited trades require verification of the competent Party’s decision.
Section E survey and certification generally applies to ships of 400 GT and above, excluding floating platforms, FSUs and FPSOs. For other ships subject to the Convention, the Party establishes appropriate measures. Flag, operating area, service, tonnage, exclusions, exemptions and implementing law must be checked.
Main obligations
- B-1: approved ship-specific BWMP.
- B-2: traceable BWRB retained for the required periods.
- B-3/B-4: applicable standard and exchange conditions.
- B-5/B-6: sediments, duties and familiarisation.
- E-1: survey and certification where applicable.
The D-1 and D-2 standards
The Convention provides for two distinct management standards, with the second representing the final and now mandatory objective for the generality of ships subject to it. The difference is not one of degree but of kind: D-1 dilutes, D-2 removes.
D-1: what «exchange» actually means
The D-1 standard is met with an effective volumetric exchange of at least 95%. Using the pumping-through method the criterion is taken as met by pumping three times the volume of each tank; less than three times is acceptable only where 95% is demonstrated.
Regulation B-4 sets out where: at least 200 nautical miles from the nearest land and in water at least 200 metres deep. Where that is not possible, as far from the nearest land as possible and in all cases at least 50 nautical miles away and in water at least 200 metres deep. Where neither is achievable, the port State may designate exchange areas in consultation with neighbouring States. And there is a clause worth knowing: the ship is not required to deviate from its route or delay the voyage in order to exchange.
| Standard | Method | Characteristics |
|---|---|---|
| D-1 | Ballast water exchange at sea, under the conditions of Regulation B-4 | Dilutes the concentration of coastal organisms by replacing them with oceanic ones, which rarely survive in coastal waters; transitional, eliminates nothing |
| D-2 | Treatment with an approved BWMS on board | Reduces viable organisms below five numerical limits — two by size and three microbiological — verifiable by analysis; the definitive standard |
Table 3.1 — Comparison of the D-1 and D-2 standards.
D-2 in figures
This is the heart of the subject, and what the course must be able to state without hesitating: D-2 is not «clean water», it is a set of five measurable limits.
| Category | Discharge limit |
|---|---|
| Viable organisms ≥ 50 µm in minimum dimension | fewer than 10 per cubic metre |
| Viable organisms ≥ 10 µm and < 50 µm | fewer than 10 per millilitre |
| Toxicogenic Vibrio cholerae (serotypes O1 and O139) | fewer than 1 cfu per 100 mL, or per gram of zooplankton sample (wet weight) |
| Escherichia coli | fewer than 250 cfu per 100 mL |
| Intestinal Enterococci | fewer than 100 cfu per 100 mL |
Table 3.2 — The D-2 ballast water performance standard (Regulation D-2).
The three indicator microbes do not measure ecology: they measure public health. They are there because ballast water has already carried cholera, and they are the reason a system can remove zooplankton perfectly and still fail the standard.
The transition timetable is Regulation B-3 as amended by resolution MEPC.297(72), in force since 13 October 2019, which anchored each ship's compliance date to its IOPP renewal survey. The final deadline was 8 September 2024: from that date D-2 is the ordinary method for ships in scope that have reached their compliance date. Exceptions, exemptions, reception facilities, other permitted methods and contingency require a specific basis, the approved plan and, where applicable, competent-authority acceptance.
How a BWMS works
Module objectiveRecognise the technologies used in a BWMS and distinguish approval under the BWMS Code from the G8 Guidelines and from Procedure G9.
Ballast Water Management Systems (BWMS) use combinations of physical and chemical technologies to reduce the concentration of viable organisms below the thresholds required by the D-2 standard.
Type approval no longer follows G8
Until 2018 BWMS were approved under the G8 Guidelines, which were not binding and left Administrations wide room for interpretation. Approval today follows the BWMS Code, adopted by resolution MEPC.300(72) on 13 April 2018 and made mandatory by the amendments to the Convention adopted by resolution MEPC.296(72), in force since 13 October 2019. The difference is not formal: the Code sets stricter and more repeatable test conditions, and it is why a system approved before that date and one approved after are not equivalent even where they carry the same commercial name.
A system using an Active Substance — electrochlorination, chlorination, ozone — additionally requires approval under Procedure G9, which assesses the risk to the environment, to human health and to the ship, and sets the limits for residuals at discharge.
| Technology | Operating principle |
|---|---|
| Mechanical filtration | Physically removes larger organisms and sediments |
| UV disinfection | Damages organisms' DNA using ultraviolet light, preventing reproduction |
| Electrochlorination | Generates a disinfecting agent through electrolysis of the seawater itself |
| Neutralisation | Some systems require neutralisation of the residual disinfectant before discharge |
Table 4.1 — Main technologies used in BWMS.
A BWMS that is installed but poorly maintained (spent UV lamps, clogged filters, uncalibrated sensors) may fail to achieve the required performance, exposing the ship to a risk of non-compliance despite formally having met the installation obligation.
Key takeaways
- Mechanical filtration, UV disinfection and electrochlorination act on organisms through different operating principles.
- The G8 Guidelines were not binding; approval now follows the BWMS Code, which sets stricter and more repeatable test conditions.
- A poorly maintained BWMS may fail to achieve the required performance and expose the ship to a risk of non-compliance.
When the system cannot treat
Module objectiveRecognise the hierarchy when the BWMS cannot treat: commissioning testing, the exceptions of Regulation A-3 and contingency measures.
An approved BWMS must be verified on its individual installation and managed under the approved plan. Technical failure, challenging water quality, A-3 exceptions and contingency are different categories.
Commissioning test
The regulation E-1 commissioning test at initial survey and following change, replacement or significant repair demonstrates that mechanical, physical, chemical and biological processes work correctly. BWM.2/Circ.70/Rev.1 calls for a representative discharge sample, analysis of at least the two D-2 size classes, assessment of self-monitoring and collection/analysis independent of the maker or supplier to the Administration’s satisfaction. It is not a full repetition of type approval.
A failed result creates a technical non-conformity to diagnose and rectify before certification. Cost and responsibility among owner, yard, installer, maker and testing provider depend on cause, contract and evidence.
Regulation A-3: defined exceptions
A-3 identifies limited cases: ship safety or saving life; accidental discharge or ingress resulting from damage subject to its conditions; avoiding or minimising a pollution incident; uptake and discharge on the high seas of the same water; and uptake and discharge at the same location without relevant mixing. It is not a general container for BWMS failures.
Contingency: case-by-case with the port State
For non-compliant water, ship and port State communicate and consider BWM.2/Circ.62 options: BWMP actions; discharge to another ship or suitable facility; a method acceptable to the port State; D-1 exchange under the approved plan; revised schedule, internal transfer or retention on board. Discharge remains subject to authority acceptance and conditions. Failure, repair plan, consultation and decisions must be recorded.
Challenging water quality
The reference is MEPC.387(81). It addresses ambient characteristics such as high suspended solids or turbidity that prevent the BWMS from meeting operational demand; it does not automatically cover temperature or salinity outside system design limitations or replace technical-failure contingency. Procedures must be ship-specific and included in the BWMP.
Key takeaways
- Commissioning testing checks installation and self-monitoring; it does not re-verify the type-approval performance.
- Outside the closed list of Regulation A-3 there is no lawful non-compliant discharge, and a broken system is not on it.
- A contingency measure does not erase the non-compliance: what protects the ship is the chain of notifications and entries.
Required documentation
Module objectiveRecognise the documentation required to demonstrate compliance with the Convention and know how the Ballast Water Record Book is kept.
Documentation management is central to demonstrating compliance with the Convention, both in routine inspections and in targeted PSC checks.
| Document | Function |
|---|---|
| Ballast Water Management Plan (BWMP) | Describes the ship's specific operating procedures for ballast water management |
| Ballast Water Record Book | Log of every ballasting, treatment and discharge operation |
| International BWM Certificate | Certifies the compliance of the ship and the installed system |
Table 6.1 — Essential documentation on ballast water management.
The Record Book changed form on 1 February 2025
Resolution MEPC.369(80) replaced the model Ballast Water Record Book. From 1 February 2025 entries follow a standardised format with operation codes from letter A to H and item numbers, on the model of the Oil Record Book; the guidance for completing it is BWM.2/Circ.80/Rev.1, which also contains examples for the unusual cases. The requirement applies to existing ships as well, not only to new buildings.
Retention is set by Regulation B-2: two years on board from the last entry, then three years under the company's control. Each operation is recorded without delay and signed by the officer in charge; each completed page is signed by the master.
From 1 October 2025, amendments MEPC.383(81) recognise an electronic BWRB. Where it replaces the paper book, the system must be approved by the Administration taking account of MEPC.372(80) and preserve authentication, amendment traceability, master verification and availability for inspection. The 2026 G4 is adopted guidance under MEPC.409(84); Convention drafts approved at MEPC 84 are not yet in force.
As with hours of rest in the MLC 2006 course, the Ballast Water Record Book must also be completed with genuine accuracy, not «for convenience»: discrepancies between the records and the operations actually carried out are among the most frequent deficiencies found by PSC inspectors in this area.
Key takeaways
- The BWMP describes the ship's procedures, the Record Book logs the operations, the certificate attests compliance.
- With Resolution MEPC.369(80), from 1 February 2025 the Record Book follows a standardised format, on existing ships too.
- Regulation B-2 sets retention: two years on board from the last entry, then three years under the company's control.
Additional requirements in certain areas
Module objectiveRecognise the additional measures a coastal State may impose in its own waters, the warnings on ballast uptake and the exemptions it may grant.
The BWM Convention does not use MARPOL’s “special areas” category. Section C governs additional measures and warnings; regulation A-4 governs limited exemptions.
C-1 measures and C-2 warnings
C-1 measures are normally notified at least six months in advance, but the Convention provides for emergencies and epidemics. Voyage preparation should consult IMO, coastal and port authority communications, notices to mariners and agent instructions, recording source, date and applicability. C-2 uptake warnings belong in voyage planning before the operation.
A-4 exemptions
An exemption covers voyages between specified ports or locations, lasts no more than five years with intermediate review, is based on a G7 risk assessment, and must not impair the environment, health, property or resources of adjacent or other States. Potentially affected States should be consulted. Route, ports, validity, conditions, mixing and records must be checked before use.
Key takeaways
- An additional measure is communicated to the IMO with scientific and technical justification and notified six months in advance.
- Every Party warns mariners of areas where ballast should not be taken up, giving coordinates and, where possible, an alternative.
- An exemption rests on a risk assessment under the G7 Guidelines, lasts at most five years and is communicated to the IMO.
The United States framework: USCG type approval and EPA discharge standards
Module objectiveDistinguish the two US regimes, USCG and EPA, and recognise why a system approved to IMO standards is not automatically usable in US waters.
The United States is not a Party to the BWM Convention. Subject vessels operate under 33 CFR Part 151 and BWMS type approval under 46 CFR Part 162.060. IMO approval does not automatically equal USCG type approval: the US certificate, operational limitations and installation must be checked.
USCG type approval and testing methods
The historical distinction between “living” and “viable/capable of reproduction” remains relevant but should not be frozen at 2022. Policy Letter 02-22 defines an evaluation process, while USCG separately publishes testing methods and protocols accepted under VIDA. Current status must be checked before technical decisions; it is wrong to say UV systems generally lack US approval.
EPA discharge standards and VIDA transition
EPA published the Vessel Incidental Discharge National Standards of Performance on 9 October 2024. USCG implementation, compliance and enforcement regulations are to follow. Until those rules are final, effective and enforceable, the 2013 VGP, current USCG rules and applicable State and local requirements continue. 9 October 2026 is the statutory deadline assigned to USCG, not an automatic switch.
AMS is a transitional solution tied to the compliance date and approval of the individual ship and system; status must be checked from the actual documents.
Key takeaways
- The numerical standard coincides with D-2, but the USCG counts living organisms while the IMO reasons in terms of viable ones.
- The Alternate Management System was a transitional measure and has by now run out for the generality of the fleet.
- The new EPA federal standards are not enforceable until the USCG adopts its implementing regulations, by 9 October 2026.
PSC inspections on ballast water
Module objectiveRecognise the three levels of the PSC inspection on ballast water and distinguish indicative from detailed analysis.
Guidelines MEPC.252(67) describe four graduated stages: initial inspection; more detailed inspection where clear grounds exist; sampling with indicative analysis; and detailed analysis where needed. An indicative result is not by itself a final determination of non-compliance.
Recurring controls
- Certificate, BWMP and BWRB consistent with ship, voyage and system.
- Operation, alarms, self-monitoring, maintenance records and commissioning.
- Actual crew knowledge of ship-specific procedures.
- Sampling, timing and action under the Guidelines and authority procedures, avoiding undue delay.
2025 BWM CIC: official preliminary data
| Indicator | Value |
|---|---|
| Total inspections | 9,244 |
| Inspections using the CIC questionnaire | 6,930 |
| Total detentions | 184 |
| Detentions directly resulting from CIC deficiencies | 30 — 0.43% of questionnaire inspections |
The critical area identified was BWMS operation and maintenance (code 14811, question 6). The data do not support undocumented regional rankings or further claims.
Key takeaways
- The international certificate must match the system actually installed: model, serial number and rated capacity.
- A negative indicative analysis does not prove non-compliance: it constitutes clear grounds for a more detailed inspection.
- In the 2025 campaign the Record Book is the most recorded deficiency, 921 findings, but the system detains: 51 detainable of 462.
Sediment management
Regulation B-5 requires sediments from spaces designated to carry ballast water to be removed and disposed of in accordance with the BWMP.
Design, removal and disposal
Ships constructed from 2009 to which the provision applies should, as far as practicable, minimise uptake and accumulation, facilitate removal and provide safe access, taking G12 into account.
Location and method depend on the approved plan, available reception facilities, safety procedures and applicable State or port rules. Regulation B-5 does not contain a universal geographical prohibition for every sediment and circumstance.
Crew training
As with the other management systems seen in previous courses, genuine compliance with the Convention depends on the crew's competence in correctly operating the system and completing the required documentation.
Elements of good training
- Understanding of the basic operation of the BWMS installed on board, not just start/stop procedures.
- Recognition of malfunction signals and immediate intervention procedures.
- Correct completion of the Record Book in real time, not after the fact.
A crew that can only start and stop the system, without understanding the correct operating parameters, is unable to promptly recognise a malfunction that could compromise D-2 compliance without anyone noticing until an inspection.
Integrating BWM into the SMS, maintenance and voyage planning
The BWM Convention remains distinct from MARPOL, ISM, stability requirements and climate regimes. On board, however, their processes share people, machinery, data and decisions. The BWMP should interface with the SMS, planned maintenance, familiarisation, risk assessment, passage/voyage planning, cargo plan and emergency management.
Before, during and after the operation
Before: verify ballast quantities and sequence, stability and strength, BWMS flow and system design limitations, expected water quality, local restrictions, available time and contingency plan. During and after: monitor parameters, alarms, bypass, neutralisation, consumables, energy, samples and records; open defects/non-conformities and corrective action where needed.
BWMS electrical load may affect fuel and emissions, but this does not alter D-2 or turn BWM into a CII measure. Safety, biological compliance and energy performance remain distinct while their interactions are made visible.
The review of the Convention: from MEPC 84 to MEPC 85
MEPC 84 approved draft Convention amendments for expected adoption at MEPC 85; it did not make them mandatory. It adopted the 2026 G4 Guidelines through MEPC.409(84), inviting early application.
Dates, transitional provisions and final text must be verified after MEPC 85.
| Area | Draft change |
|---|---|
| A-3 / B-1 | CWQ, contingency, procedures and BWMS approval status in the plan. |
| B-2 / B-6 | Maintenance records and documented familiarisation. |
| D-2 | Maximum Allowable Discharge Concentration for active substances. |
| E-1 | Installation and maintenance records; annual residual sampling where applicable; biological testing at intermediate and renewal surveys to verify D-2, subject to adopted text. |
Work on the BWMS Code continues intersessionally. If adopted and brought into force, the package will shift evidence towards documented maintenance, familiarisation and periodic verification.
Building effective BWM management
Module objectiveSet up BWM compliance as part of daily technical management, integrating equipment maintenance, documentary discipline and crew training.
Effective management of BWM compliance requires the integration of equipment maintenance, documentary discipline and crew training, following the same principles already seen for the ISM Code and maintenance management.
Critical success factors
- Scheduled maintenance of the BWMS, with the same discipline seen in the Reliability Management course.
- Ongoing crew training, not limited to initial training alone.
- Rigorous discipline in completing the Record Book in real time.
- Monitoring of specific local requirements for the routes the ship usually serves.
Like decarbonisation and maintenance management, ballast water management is no longer an isolated obligation but an integrated component of the ship's daily technical management, requiring the same systematic attention given to other critical onboard systems.
Key takeaways
- Maintenance of the BWMS is scheduled with the same discipline seen in the Reliability Management course.
- Crew training continues beyond initial training and the Record Book is completed in real time.
- Monitoring of specific local requirements concerns the routes the ship usually serves.
Recurring mistakes
From the Mistake Library of SuperbaKnowledge, filtered to the subjects this course covers. This view selects and organises content published in SuperbaKnowledge; it does not modify or replace it. The linked Knowledge page remains the reference version, while official texts remain authoritative.
| Topic | Mistake | Typical consequence | Topic sheet |
|---|---|---|---|
| Ballast Water | Using the old BWRB format after 1 February 2025 | PSC deficiency | See the topic sheet |
Related PSC deficiencies
From the PSC Knowledge Base of SuperbaKnowledge. This view selects and organises content published in SuperbaKnowledge; it does not modify or replace it. The linked Knowledge page remains the reference version, while official texts remain authoritative.
| Deficiency | Regulation | Indicative frequency | Possible consequence | Topic sheet |
|---|---|---|---|---|
| Ballast Water Record Book format not updated (post 1/2/2025) | BWM Convention | Medium | Deficiency | See the topic sheet |
Glossary of acronyms
| Acronym | Definition |
|---|---|
| BWM | Ballast Water Management |
| BWMC | Ballast Water Management Convention |
| BWMP | Ballast Water Management Plan |
| BWMS | Ballast Water Management System |
| AMS | Alternate Management System (transitional USCG regime) |
| BWMS Code | Code for Approval of Ballast Water Management Systems (MEPC.300(72)) |
| CIC | Concentrated Inspection Campaign |
| EPA | Environmental Protection Agency (United States) |
| cfu | Colony-forming unit |
| GT | Gross Tonnage |
| IOPP | International Oil Pollution Prevention Certificate |
| MEPC | IMO Marine Environment Protection Committee |
| MADC | Maximum Allowable Discharge Concentration |
| MoU | Memorandum of Understanding on Port State Control |
| PSC | Port State Control |
| USCG | United States Coast Guard |
| VGP | Vessel General Permit (EPA) |
| VIDA | Vessel Incidental Discharge Act, 2018 |
References and sources
Consolidated list of the sources cited. Updated as of August 2026.
| Function | Sources |
|---|---|
| Convention and application | 2004 BWM Convention; Article 3; Regulations A–E; current status to be checked against IMO treaty status. |
| Standards and timetable | Regulations B-3/B-4, D-1/D-2; MEPC.297(72). |
| Type approval and commissioning | MEPC.296(72), MEPC.300(72), MEPC.325(75), BWM.2/Circ.70/Rev.1. |
| Contingency and CWQ | BWM.2/Circ.62; MEPC.387(81). They are distinct instruments. |
| Records | MEPC.369(80), BWM.2/Circ.80/Rev.1; MEPC.383(81) and MEPC.372(80) for the electronic BWRB. |
| PSC and CIC | MEPC.252(67), BWM.2/Circ.42/Rev.2; Tokyo MoU preliminary CIC release, 17 March 2026. |
| United States | 33 CFR Part 151; 46 CFR Part 162.060; USCG Policy Letter 02-22 and current accepted-methods page; VIDA; EPA national standards. |
| 2026 review | MEPC.409(84): 2026 G4 adopted. Convention drafts approved at MEPC 84, not in force; adoption expected at MEPC 85. |
This course is educational material for training purposes and does not constitute a professional certification or qualifying credential. Read the full disclaimer.