Ballast water management (BWM) and biofouling

The BWM Convention applies to all ships with ballast water capacity and active in international trade, except ships mentioned in Article 3:

1. Ships which are not designed or constructed to carry ballast water.

2. Ships that only operate in the local waters of a single authority (party), or in local waters of a single authority and on the high seas.

3. War ships, naval auxiliary, or other ships owned and operated by a state and used only on government non-commercial service, as stated in Article 3.2(d) of the convention.

4. Ships with permanent ballast water in sealed tanks that is not subject to discharge.

5. For ships operating usually only in local waters, single international voyages may be granted an exemption under regulation A-4 by following the IMO guidance circular BWM.2/Circ.52/Rev.1. The countries of origin and destination must be approached for consent to the single voyage.

1. Since the date of entry into force (EIF), 8 September 2017, all ships shall have and implement a BWM Plan (BWMP) and record all ballast water operations in the BWM record book. The BWMP shall be approved by the administration.

2. Vessels above 400 GT (excluding floating platforms, FSUs and FPSOs) are subject to a BWM survey and are required to hold a BWM certificate, as per regulations E-1 and E-2.

3. Since 8 September 2024 at the latest, vessels shall meet the D-2 standard by having a ballast water treatment system (BWTS) approved, installed and commissioned, and the International Ballast Water Management Certificate has to indicate the D-2 method only.

4. Alternatively, ships without a BWTS and operating in international voyage may apply to the Flag Administration for an “other approach” method in accordance with Reg. A-4, B-3.6, B-3.7 or A-5 (Ref. UI BWM.2/Circ.66/Rev.5, Ch.5).

If the vessel is in international voyage and the BWM Convention is applicable as per Article 3 of the convention, the vessel and also floating platforms, FSUs and FPSOs must comply with the D-2 (treatment) regulation. According to the convention, such vessels shall be required to have an approved BWM Plan (BWMP) and a record book. But a BWM certificate is only required if the flag administration has their own national requirements.

The D-2 compliance date for these vessels was the completion of first IOPP renewal after 8 September 2019. If the vessel does not have an IOPP certificate, then the compliance date was 8 September 2024 at the latest, if not otherwise given by the flag administration.

If the BWM Convention is not applicable as per Article 3, for instance in the case that the vessel is reasonably permanently positioned, then an approved BWMP for the D-1 standard should be available in the case of single voyages, by following the IMO guidance circular BWM.2/Circ.52/Rev.1.

The Ballast Water Management Plan (BWMP) is the document that details the procedure for the discharge of ballast water and the handling of sediment in accordance with regulation D-2 (treatment) and regulation B-5 (sediment management).

This plan must be specific to the vessel and the installed BWTS, and the plan must be approved for each vessel by the flag administration or Class if authorized. 

It is recommended that the BMWP also includes a chapter or an addendum describing

• contingency measures in accordance with the IMO guidance BWM.2/Circ.62 in the event that the treatment system malfunctions

• procedures for operating in challenging water quality (CWQ) conditions in accordance with the interim IMO guidance MEPC.387(81) if the vessel is expected to operate in ports with CWQ conditions

• if applicable, procedures for temporary storage of treated sewage and/or grey water in ballast water tanks in accordance with IMO guidance BWM.2/Circ.82

Some flags require the BWMP to include a chapter for contingency measures, and this amendment to the BWMP must be approved by the flag administration or Class.

Although only some flag administration require that a BWMP addendum with procedures for operating in CWQ conditions and/or the temporary storage of treated sewage and/or grey water is approved by the flag or a Recognized Organisation, DNV recommend that such amendments are submitted for approval by DNV.

DNV has developed a template and a generator for the BWMP containing all elements listed above, and this template / generator can be found here.

If a ship uses an “other approach” method in accordance with Reg. A-4, B-3.6, B-3.7 or A-5 (Ref. UI BWM.2/Circ.66/Rev.5, Ch.5), then the Flag administration may require a BWMP describing this method.

As of 1 February 2025, vessels must record and report their ballast water operations using the ballast water record book form and the reporting codes adopted by IMO in Resolution MEPC.369(80). Further details are provided by the IMO guidance BWM.2/Circ.80/Rev.1 on ballast water record-keeping and reporting. This guidance explains how ballast water operations should be recorded by making mandatory entries in the Ballast Water Record Book (BWRB) and contains several examples for recording ballast water operations.

The D-2 standard became mandatory for all existing vessels, to which the BWM convention is applicable, at completion of the first IOPP renewal on or after 8 September 2019, latest by 8 September 2024. Vessels keel-laid or having underwent a major conversion after 8 September 2017 shall comply with the regulation D-2 upon delivery.

The intention of the D-2 regulation (treatment) is to prevent the discharge of harmful microorganisms into new locations. However, the convention is open regarding how this can be achieved, such as by discharging the ballast water at a reception facility (reg. B-3.6). The port state should have the final decision as to whether they accept any equivalent to D-2 and allow discharging in their waters. For most vessels, a treatment system will be the best way to comply with regulation D-2. Such a system must be type approved by an administration, and most administration accept the type approval issued by another Party to the BWM Convention or a Class authorized by this Party.

The type approval certificate for the ballast water treatment system installed on a vessel can have a validity date that has expired. However, the certificate must have been valid at the time when the treatment system was installed (i.e. the date of installation stated on the BWM certificate).

Even fresh water used as ballast water shall be treated according to the BWM Convention. Regulation B-3.7 accepts other methods of ballast water management as alternatives, but a fresh water generator is not accepted by the IMO for the D-2 standard.

As part of the approval process for retrofitting a vessel with a ballast water treatment system, the owner will be required to submit the BWMP for approval with information regarding the treatment system and its application. Given that all vessels now have to comply with the D-2 standard, only the treatment method must be included in the BWMP. A previously approved exchange procedure (D-1) can remain in the BWMP, but he BWMP shall clearly note that treatment is the only approved method and that exchange may only be carried out as a contingency measure or as part of decontamination when operating in challenging water quality (CWQ) conditions. The previously approved BWMP with exchange procedures (D-1) may be added as an appendix to the BWMP.

DNV has prepared a BWMP template for the D-2 standard, which can be found here. We encourage ship owners to use the BWMP template for D-2 for new-building and retrofit projects. DNV has also prepared a template for exchange procedures if there the vessel does not have a previously approved BWMP for D-1 and intends to make use of contingency measure or procedures for operating in CWQ conditions.

In accordance with Articles 3.2(b) to 3.2(d) of the BWM Convention, vessels that only operate in waters under the jurisdiction of one Party are exempted from the BWM convention (the convention does “not apply”), unless the Party determines that the discharge of ballast water from such vessels would impair or damage their environment, human health, property or resources. 

Vessels operating only in national waters should retain on board a dispensation letter issued by the flag or the administration in which water the vessel operates. Unless required by the flag administration, vessels, to which the convention is not applicable according to Article 3, do not have to carry on board a BWM Certificate. It is sufficient that the vessel carries on board a dispensation letter / statement by the flag or the administration in which water the vessel operates.

Yes, even vessels operating only in intra North Sea traffic and/or intra Baltic Sea traffic have to comply with the D-2 standard.  

However, the convention is open for exemption for vessels voyaging only between specified ports or locations based on Regulation A-4. An exemption may be given by parties in waters under their jurisdiction (local authorities). The exempting parties shall communicate the exemption to the IMO. This exemption can be given for a period of maximum five years and is subject to intermediate review (reg. A-4). A full overview of the application procedure is given in the Guidelines for Risk Assessment Under Regulation A-4 of the BWM Convention (G7).

Within Norwegian territorial waters and economic zone, the Norwegian national regulation applies.

Yes. The convention allows the use of an electronic record book, and the BWM record book may even be integrated into another record book or system on board. Guidelines for the use of Electronic Record Books (ERB) under the Ballast Water Management (BWM) Convention were adopted by IMO in Resolution MEPC.372(80). In accordance with the amendments to BWMC regulations A-1 and B-2 by Resolution MEPC.383(81), vessels operating with a BWM ERB as main record book shall have a “Declaration of BWM Convention Electronic Record Book” issued by the RO or by the Flag since 1 October 2025.

Electronic Record Books mentioned on the Declaration shall be type approved by or on behalf of the Flag Administration.

A ship operating exclusively under the jurisdiction of one party to the convention, pursuant to Articles 3.2(b) to 3.2(d), may be granted an exemption under regulation A-4 for a single voyage on the condition that the ship performs ballast water exchange in accordance with regulations B-4 and D-1 and an approved BWMP. The requirements of regulation A-4.1.4 (risk assessment) should be addressed to the satisfaction of the countries of origin and destination of the ship.

The IMO guidance circular BWM.2/Circ.52/Rev.1 can be applied with consent of the countries of origin and destination.

No, only the D-2 standard is applicable on the BWM certificate since 8 September 2024 at the latest. While ballast water exchange may still be carried out as contingency measure or when operating in challenging water quality (CWQ) conditions, only treatment in accordance with the D-2 standard is the approved method to be stated on the BWM certificate.

The BWM Convention is international. Even if there are a number of countries that have not ratified the convention and do not require a vessel to fulfil the requirements, DNV recommends following the convention at any time to avoid possible comments from the PSC of the signatory state.

Yes, some countries, such as the Ukraine and the USA, have stricter requirements than those listed in the convention. DNV recommends clarifying local requirements prior to conducting discharge of the ballast water in a new port.

The type approval process for ballast water treatment systems (BWTS) using active substances includes an evaluation and approval by IMO and/or USCG. Chemical treatment systems are required to satisfy minimum toxicity requirements, and any limitations applicable to the BWTS, such as the Maximum Allowable Discharge Concentration (MADC) of active substances, are stated in the type approval certificate.

The requirements related to toxic discharge for different US states are addressed in the 2013 VGP and the US EPA’s Generic Protocol for the Verification of Ballast Water Treatment Technology, known as the ETV Protocol.

The amendments to regulation E-1 of the BWM Convention adopted by MECP 74 requires biological efficacy testing when commissioning a BWTS on board a vessel. This amendment came into effect on 1 of June 2022.

For the biological efficacy testing, a test organization approved by DNV or by an organization/supplier accepted by the flag administration, needs to go on board the ship to take samples. An indicative (or detailed) analysis of the samples is typically performed on board the ship (organism counts have to be carried out within a few hours after the samples were taken). The test shall take into account the Guidance for the commissioning testing of ballast water management systems (BWM.2/Circ.70/Rev.1), as amended.

The commissioning test is successful if the indicative analysis indicates that the discharge samples do not exceed the D-2 standard for the size classes ≥50 µm and organisms 10-50 µm and the self-monitoring equipment indicates correct operation. The DNV surveyor will then be able to issue a full term International Ballast Water Management Certificate. There is no separate certificate for the test itself, but the test results need to be summarized in a report. DNV has published a template for such a report, and the template is available here.

A biological test for the IMO is only required once per system onboard at the commissioning of the BWTS and before the International Ballast Water Management Certificate is issued. However, a new biological test is required after a significant upgrade or change to the installed BWTS as described by Reg. E-1.1.5 

The commissioning test shall be arranged either with a DNV approved service supplier or by an organisation/supplier acceptable to the Flag Administration. Please refer to the DNV approval finder for test facilities accepted by DNV for biological commissioning testing of BWMS (select “Approval of Service Suppliers” and then “Service Suppliers engaged in testing of Ballast Water Management Systems (validation of biological efficacy at commissioning)” or “Commissioning testing of ballast water management systems (BWMS)”).

For becoming an approved service supplier for commissioning testing, a test facility is requested to submit their standard operating procedures (SOP) for sampling and analysis as per the IMO guidance for commissioning testing of BWMS (BWM.2/Circ.70/Rev.1). Analysis methods, including indicative methods, listed in the IMO guidance on ballast water sampling and analysis (BWM.2/Circ.42/Rev.1) may be applied. A test facility may use a portable compliance monitoring device, given that the reliability and accuracy of this device has been validated. For further details, please visit our DNV class programmes page to find the “Approval of service suppliers scheme”, document code “DNV-CP-0484”. In addition, you can find the template for biological testing at commissioning of BWM here.

There will be no need to send the approved BWMP for re-approval. However, the BWMP should get a note in the ship’s particulars to reflect that since the first IOPP renewal survey after 8. September 2019, treatment as per D-2 is the only approved method and the D-1 exchange shall be used only as a contingency measure. If this implies just a small revision to the BWMP, a class surveyor can check and endorse the note in the BWMP during the annual survey. The approved exchange procedure (as per D-1) can still be in the approved BWMP; but D-1 shall only be used as a contingency measure.

The vessel must contact the port authority and flag state administration immediately to discuss contingency measures (see separate question on contingency measures).

We advise ship owners to follow the IMO guidance circular on contingency measures BWM.2/Circ.62.

Exchange may be offered as a contingency measure but cannot be performed without permission from the port authority receiving untreated water and flag state. The vessel must obtain approval of the exchange method D-1 before proposing exchange as a contingency measure.

When travelling in US waters, the USCG requires that the BWMP contain vessel-specific contingency methods. The BWMP should also include procedures for contacting the Captain of the Port (COTP) and reporting to the National Ballast Information Clearinghouse (NBIC) in the event of a BWTS malfunction

The vessel must contact US authorities as soon as possible and ask for instructions. US regulations require that the vessel inform the nearest COTP, but it is recommended that the destination COTP also be informed.

The IMO has established a generic guidance in BWM.2/Circ.62 for situations where ballast water to be discharged from a ship is determined to be non-compliant. In such cases, communication between the ship and the port state should occur. The ship and the port state should consider the following as possible contingency measures on a case-by-case basis:

1. Actions predetermined in the BWMP of the ship

2. Discharging ballast water to another ship or an appropriate shipboard or land-based reception facility, if available

3. Managing the ballast water or a portion of it in accordance with a method acceptable to the port state

4. Operational actions, such as modifying sailing or ballast water discharge schedules, internal transfer or ballast water other retention of ballast water on board the ship. The port state and the ship should consider any safety issues and avoid possible undue delays.

Having considered all options above, the ballast water may be discharged in the port or any suitable area, as acceptable to the port state.

Port state consideration may include environmental, safety, operational and logistical implications of allowing or disallowing the discharge.

The discharge of ballast water is subject to any conditions of the port state. In any case, the ship is required to do its best to correct the malfunction of the BWTS as soon as possible and submit its repair plan to the PSC authorities and the flag state.

If the only change for the BWMP is to include contingency measures, an addendum to the BWMP will be enough to send to class for approval. If the BWMP for D-2 itself is revised and amended with an additional chapter, then the plan is to be submitted for re-approval.

Some flag administrations require a BWMP chapter or addendum with contingency measures according to the IMO guidance BWM.2/Circ.62 and that such a chapter or addendum is approved by Class. Contingency measures may also be included voluntarily by the vessel owner or manager for vessels of other flags. DNV strongly recommends including in the BWMP a chapter or addendum on contingency measures instructing crew on the procedure in the event of a BWTS malfunction and submitting the revised BWMP or addendum to DNV for approval.

In case of BWTS malfunction, well-planned BWM contingency measures allow ship owners to avoid unnecessary downtime for the vessel. The port authority of destination and the flag administration are to be informed about the malfunction of the BWTS.

DNV has prepared a BWMP template for D-2 with a chapter on contingency measures, which can be found here.

IMO MEPC adopted Resolution MEPC.387(81) with interim guidance for ships operating in challenging water quality conditions. The purpose of this guidance is to assist ships to comply with the BWM Convention and the D-2 discharge standard when a type-approved BWMS encounters operational limitations or has difficulty meeting operational demand in challenging water quality (CWQ) conditions, such as high total suspended solids or turbidity (Note that temperature and/or salinity of the outside of the BWMS design limitations are not considered CWQ conditions). CWQ conditions may result in the BWMS to be temporarily inoperable due to, for example, filter clogging or causing the BWMS to operate outside its system design limitations.

The guidance does not address situations in which a BWMS is inoperable for reasons unrelated to CWQ, such as technical failures of the BWMS.

Bypassing the BWMS should be the last resort. However, if bypassing the BWMS is unavoidable, only the minimum ballast required to maintain safety and operational demands of the ship shall be taken up. Moreover, after any bypassing of the BWMS, the affected ballast tanks need to be decontaminated to again restore compliance with the D-2 standard. Decontamination is to replace the untreated ballast water in each contaminated tank through ballast water exchange, flushing and final treatment via the BWMS.

When applying the procedures for operating in CWQ outlined in MEPC.387(81), it is not required to inform the port State of uptake or the flag State of any reactive bypass (i.e. a bypass upon reaching an operational limitation or encountering an inability to meet operational demand). Only the port State where affected ballast water will be discharged needs to be informed of the bypass and the decontamination actions taken.

Any pre-emptive bypass (i.e a BWMS bypass undertaken prior to or during a ballasting operation in anticipation of reaching an operational limitation or encountering an inability to meet operational demand) may be agreed in advance bilaterally between the flag administration of the ship and the port State receiving the ballast water.

Pre-emptive bypass arrangements should be specific to voyages between specified ports or locations and should be documented in the ship's approved BWMP and the BWRB. Ships expecting to encounter CWQ conditions and intending to apply CWQ procedures should amend the BWMP with the steps outlined in MEPC.387(81). The procedures in the BWMP for managing CWQ conditions should be ship-specific and consider the operational limitations of the BWMS installed and the operational demand of the ship.

If a ship does not expect to encounter CWQ conditions, it is not required to update or amend the BWMP with CWQ procedures. However, some flag administrations require the BWMP to be amended for all ships sailing under their flag. Hence, please check the particular requirements of the flag administration of your vessel.

Any amended BWMP shall be submitted for approval. Alternatively, a standalone addendum to the BWMP with CWQ procedures may be submitted for approval.

Please consult the manual of the BWTS for any troubleshooting procedures in such situations. The treatment system may be operated at a lower flow rate.

In case the treatment system cannot be used for ballasting operations due to filter clogging, and the BWTS must be by-passed, any untreated ballast water in the tanks should be exchanged and the ballast water tanks in question should be decontaminated in accordance with IMO guidance MEPC.387(81) for operating in challenging water quality (CWQ) conditions.

In case ballasting operations were carried out with alarms indicating that the treatment system is operating outside the system’s performance claim (e.g. UV intensity or TRO is too low), the treated ballast water may not comply with the D-2 standard. Ballast water that is insufficiently treated should be exchanged and the ballast water tanks in question should be decontaminated in accordance with IMO guidance MEPC.387(81) for operating in challenging water quality (CWQ) conditions.

If the only change for the BWMP is to include procedures for operating in challenging water quality conditions in accordance with IMO guidance MEPC.387(81) and/or, as applicable, procedures for temporary storage of treated sewage and/or grey water in ballast tanks in accordance with IMO guidance BWM.2/Circ.82, an addendum to the BWMP will be enough to send to Class for approval. If the BWMP for D-2 itself is revised and amended with an additional chapter, then the plan is to be submitted for re-approval.

Intra North Sea ballast water contingency and compliance area are indicated in Annex 10 to the OSPAR Convention. These areas may only be used by vessels that are on a voyage between two different North Sea ports and are facing a contingency situation according to BWM.2/Circ.62 or are in challenging water quality according to MEPC.387(81) and meet the other prerequisites specified in Annex 10 to OSPAR Convention.

Training of officers and crew in ballast water management should be an integral part of the vessel’s Safety Management System (SMS) in accordance with the ISM Code. DNV recommends that the different roles that officers and crew may have with regard to ballast water management, including the operation, troubleshooting and maintenance of the ballast water treatment system, are clearly described and that the training requirements for each role are clearly specified. Records of training individual officers and crew members should be maintained on board the vessel or easily available on request by a PSC officer.

Vessels may meet the USCG discharge standard in one of five ways:

1. Use of a USCG type-approved BWTS

2. Temporarily use of a foreign type-approved BWMS that the USCG has accepted as an Alternative Management System (AMS).

3. Use and discharge of ballast water obtained from a US public water system.

4. Discharge of ballast water to a reception facility.

5. Refrain from discharging ballast water within 12 nautical miles of the US coast.

It is also possible to apply for an extension, but the vessel’s management must document that none of the options above are viable.

Some territorial waters may be divided into different zones for exchange. An exhaustive list of special regulations is not available, and additional regulations may be subject to change now that the convention has been ratified. It is recommended that vessel operators contact the relevant flag administrations.

The US is the only country which requires type-approved systems that satisfy a standard other than the IMO. Certain states have specific ballast water requirements:

• Arizona
• California
• Connecticut
• Hawaii
• Illinois
• Indiana
• Maine
• Michigan
• Minnesota
• New York
• Ohio
• Oregon
• Rhode Island
• Vermont
• Washington
• Wisconsin

With the exception of Oregon, the requirements of these states are found in the 2013 VGP.

No, the discharge requirements for ballast water in California are the same as the federal USCG requirements. While California intends to apply stricter requirements, no treatment systems was yet found to be available which can satisfy any stricter California requirements.

VGP requirements are only for the USCG and are not covered in the IMO. “The Vessel Discharge Sample Collection & Analytical Monitoring, A How-To Reference for EPAs, 2013 Vessel General Permit (VGP)” final report covers the frequency of testing and the parameters to test. Please note that the VGP requirements are different than IMO requirements for biological sampling and analysis at commissioning of the BWTS.

The main mode of action of UV irradiation is to damage the organisms’ genetic material (DNA and RNA) so that they are not able to reproduce. Common to the filtration and UV technology-based systems used for treatment of ballast water is that while the filter component mainly has effect on the >50 micron organisms, UV affects all organisms but with the highest impact on those in the 0 to 50 micron-sized range, mainly algae, due to the size-related penetration depth. Algae that are irreversibly damaged by UV appear to be “live”, but they are not able to reproduce after being treated with sufficient UV irradiation. Without any reproductive capability, colonization of a new environment is not possible.

The BWTS on DNV-class vessels shall include relevant gas detectors. BWTS that are type approved by DNV already include these sensors. In case of a leakage, a warning should be given and, if necessary, a shutdown should take place. Location installation also requires ventilation arrangements. If the BWTS is in a dedicated room, ventilation changes are required depending on the type of vessel and location.

DNV has not detected any hazardous gas generated by the BWTS type approved by DNV in the ballast water tanks. However, confined space entry precautions are always to be followed before entering a ballast water tank regardless of the BWTS installed. The general procedure for safe tank entry must be followed.

Plastic pipe may be used in ballast water management system (BWMS) provided that the following design requirements are complied:

1. Plastic pipes are type approved for its intended service. (for special service in chemical cleaning/or chemical injection system, plastic pipe manufacture shall be consulted for the intended service.) (DNV Rules Pt.4 Ch.6 Sec.2 1.7.5, Sec.9 1.7.5)

2. Plastic pipe shall have low surface flame spread characteristics. (DNV Rules Pt.4 Ch.6 Sec.2 1.7.1)

3. Plastic pipe are fitted with remote isolation valve at connection between ballast water treatment system and main ballast pipe/(or sea inlet/sea outlet if applicable) to prevent uncontrolled flooding of the space where the BWMS (plastic pipe) is located. The isolation valves including actuators, shall be steel material or equivalent and be remotely controlled from outside the space. (DNV Rules Pt.6 Ch.7 Sec.1 3.3.1.2, Pt.4 Ch.6 Sec.3 1.3.10)

4. For plastic pipe installation in hazardous area, plastic pipe shall be type approved for installation in hazardous area which includes electrically conductive characteristics. (DNV Rules Pt.4 Ch.6 Sec.9 1.7.2, Sec.10 4.1.9)

5. If the plastic pipe is part of main ballast piping function (main function), fire endurance test L3 is required for the plastic pipe installation in Engine Room/Pump Room/similar machinery space/etc. (Usually not to be installed in part of main ballast piping system in upper deck/or deckhouse at upper deck) (DNV Rules Pt.4 Ch.6 Sec.2, Table 1 – fire endurance requirement matrix)

If there is a connection between the ballast system and sewage system, some port states will not accept the use of such connections. Additionally, the BWTS may be sensitive towards contamination. While not in contradiction with MARPOL Annex IV, this is potentially in conflict with the BWM Convention. Combined ballast and treated wastewater (TWW) or grey water (GW) tanks are not recommended; however, they may be accepted through means on how to prevent contamination into the ballast system and signboard for the transfer connection between the TWW/GW system and the ballast tank(s).

Guidance for the temporary storage of treated sewage and/or grey water in ballast water tanks is given by the IMO circular BWM.2/Circ.82.

The Ballast Water Management Plan (BWMP) of the ship should include a ship-specific change-over procedure, from ballast water storage to TS/GW storage and back to ballast water storage, including pump and piping associated with the dual-purpose BW tanks, with specific details on how the flushing is conducted.

The Ballast Water Record Book (BWRB) should have an entry made under the appropriate code as mentioned in the IMO guidance BWM.2/Circ.80.

For vessels laid up for longer periods (cold lay-up), all statutory certificates are not maintained by periodical surveys, while the class status is maintained by periodical surveys with a limited scope. In the background and in the DNV systems, the normal survey schedule is dormant and will be reinstated with the original dates after the lay-up by performing the periodical surveys due at that time.

Some laid-up vessels have decoupled their IOPP which is to be re-coupled at recommissioning survey.

In relation to the implementation of the BWM Convention, if the ship has ballast water tanks and is operating in international waters the installation of the BWTS (D-2 compliance) is mandatory at recommissioning survey.

If the ship with ballast water tanks shall operate only in national waters based on Article 3, then the Coastal State or Flag administration is to be approached for a “non-applicability” / dispensation letter to be kept on board.

Such declaration/exemption will be subject to the port state and flag state in question (See question "I need to do a single voyage between two locations. Can I apply for an exemption?" under Convention basics).

Tankers operating as Floating Storage Units (FSUs) and Floating and Regasification Units (FSRUs) and similar operating in national water may apply for a “non-application” of the BWM convention based on Article 3.2. The flag administration or the competent shore state determines if the convention is not applicable and may issue a “non-applicability” / dispensation letter / statement.

If an owner would like to change the status of these vessels to normal seagoing vessels, this needs to consider that such a change could lead to the need for the immediate installation of a BWTS.

RSW tanks are not considered ballast tanks by some flag administrations. So the flag administration shall be contacted in this situation. However, if the vessel is using RSW tanks also for stability purposes, with only ballast water inside the tanks, it meets the definition of a ballast tank according to the BWM Convention.

The below is DNV’s interpretation on how fishing vessels may comply with the BWM Convention. DNV recommends ship owners to contact the flag of the vessel in regards to this requirement.

• The RSW tanks, when used as ballast tanks, can only discharge according to the D-1 (exchange) or D- 2 (treatment) standards
• When in RSW mode (i.e. containing fish), the tanks are cargo tanks and discharge with regard to the BWM Convention does not need to be considered.
• All other ballast tanks, anti-roll tanks, etc. must follow the BWM Convention as usual.
• Such ships would need to have a BWTS installed. Administrations/class should require a BWMP that explains in detail to the captain when he must use the treatment system.
• The total ballast water capacity as defined in regulation A-1.2 must include the RSW tanks for ships that use them as ballast water tanks in some conditions.

Yes, MOUs are affected by the convention as soon as they move to a new location (in-transit condition). However, while operating within the local waters of the authority, vessels can apply for “non-application” of the BWM Convention based on Article 3.2 of the BWM Convention. Authorization shall be granted by the local authority, and the vessel’s flag administration has to be informed.

For single voyages, the IMO guidance circular BWM.2/Circ.52/Rev.1 can be applied with consent of the countries of origin and destination.

Yes, regulation A-5 of the convention allows for an equivalent compliance with the requirements, but not for exceptions. Equivalent compliance must be determined by the administration taking into account the G3 Guidelines: Guidelines for ballast water management equivalent compliance.

No, during the MEPC 70 it was concluded that such cases will be covered only by MARPOL Annex I and there will be no amendment for the BWM Convention.