RESOLUTION MEPC.

387(81) (adopted on 22 March 2024)

INTERIM GUIDANCE ON THE APPLICATION OF THE BWM CONVENTION TO SHIPS
OPERATING IN CHALLENGING WATER QUALITY CONDITIONS
 RESOLUTION MEPC.387(81) (adopted on 22 March 2024)
INTERIM GUIDANCE ON THE APPLICATION OF THE BWM CONVENTION TO SHIPS
OPERATING IN CHALLENGING WATER QUALITY CONDITIONS
MEPC 81/16/Add.1
Annex 5, page 1
ANNEX 5

RESOLUTION MEPC.387(81)
(adopted on 22 March 2024)

INTERIM GUIDANCE ON THE APPLICATION OF THE BWM CONVENTION TO SHIPS

OPERATING IN CHALLENGING WATER QUALITY CONDITIONS

THE MARINE ENVIRONMENT PROTECTION COMMITTEE,

RECALLING Articles 38(a) and 38(b) of the Convention on the International Maritime
Organization concerning the functions of the Marine Environment Protection Committee
conferred upon it by international conventions for the prevention and control of marine pollution
from ships, and its functions for considering appropriate measures to facilitate the enforcement
of such conventions,

RECALLING ALSO that resolution MEPC.290(71) established an experience-building phase

(EBP) associated with the International Convention for the Control and Management of Ships'
Ballast Water and Sediments, 2004 (BWM Convention), in order to identify aspects of this
Convention that are working well and to shed light on issues that require further attention,

RECOGNIZING that properly installed, operated and maintained type-approved ballast water
management systems (BWMS) may effectively become temporarily inoperable in the various
challenging water quality (CWQ) conditions that exist in a number of global ports and locations,

CONCERNED that bypassing installed BWMS in CWQ, while sometimes necessary as a last
resort to permit the continued operation of ports and ships, may contaminate ballast tanks and
sediments with harmful aquatic organisms and pathogens that present substantial risks for the
environment, human health, property and resources where ballast water is later discharged,

EMPHASIZING its expectation that discharged ballast water meets the performance standard
in regulation D-2 of the BWM Convention whenever the Convention requires this to be the
case, while recognizing the challenges currently faced by ships encountering CWQ in enclosed
and semi-enclosed seas,

DETERMINED to thoroughly address the issue of CWQ through the holistic review of the
Convention under the experience-building phase (EBP), the scope of which includes the Code
for Approval of Ballast Water Management Systems (BWMS Code, resolution MEPC.300(72))
and the Guidelines for port State control under the BWM Convention (resolution
MEPC.252(67)), and avoid unintended consequences for ships already equipped with BWMS,

CONSIDERING that, in the meantime, ships urgently need guidance on managing CWQ and
retaining compliance with the D-2 performance standard in subsequent discharge operations,
while also considering that Administrations, BWMS manufacturers and port States would also
benefit from guidance on implementing their roles with respect to CWQ,

1 ADOPTS the Interim guidance on the application of the BWM Convention to ships
operating in challenging water quality, as set out in the annex to the present resolution;

2 REAFFIRMS the conditions for temporary non-penalization agreed in operative

paragraph 4 of resolution MEPC.290(71) relating to non-compliance of a ship with the
performance standard in regulation D-2 following the use of a BWMS during the EBP;

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 RESOLUTION MEPC.387(81) (adopted on 22 March 2024)
INTERIM GUIDANCE ON THE APPLICATION OF THE BWM CONVENTION TO SHIPS
OPERATING IN CHALLENGING WATER QUALITY CONDITIONS
MEPC 81/16/Add.1
Annex 5, page 2

3 CALLS UPON all relevant entities to maximize the suitability and regular use of
BWMS for the management of CWQ in both the short and long term, and calls particularly
upon:

.1 BWMS manufacturers to develop performance improvements regarding

commonly encountered water quality challenges;

.2 ships and shipyards to invest in the most suitable, robust BWMS where
known and available;

.3 ships to treat as much ballast water as practicable in CWQ and use bypass
as a last resort;

4 AGREES to keep this interim guidance under review in connection with the EBP.

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 RESOLUTION MEPC.387(81) (adopted on 22 March 2024)
INTERIM GUIDANCE ON THE APPLICATION OF THE BWM CONVENTION TO SHIPS
OPERATING IN CHALLENGING WATER QUALITY CONDITIONS
MEPC 81/16/Add.1
Annex 5, page 3

ANNEX

INTERIM GUIDANCE ON THE APPLICATION OF THE BWM CONVENTION TO SHIPS

OPERATING IN CHALLENGING WATER QUALITY (CWQ) CONDITIONS

TABLE OF CONTENTS

Introduction

Purpose
Principles
Application
Definitions

Guidance for ships operating in CWQ

Pre-planning
Assessment
Troubleshooting and mitigation
CWQ triggers
Alternatives to bypass
Bypass procedure
Decontamination
Communication
Record-keeping

Guidance for Administrations with respect to Ballast Water Management Plans and
CWQ

Guidance for port State control officers with respect to ships that have encountered CWQ

Guidance for BWMS manufacturers with respect to participation in pre-planning

Appendices

1 Example decontamination procedure

2 Sample process diagrams for ships ballasting in areas with CWQ

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 RESOLUTION MEPC.387(81) (adopted on 22 March 2024)
INTERIM GUIDANCE ON THE APPLICATION OF THE BWM CONVENTION TO SHIPS
OPERATING IN CHALLENGING WATER QUALITY CONDITIONS
MEPC 81/16/Add.1
Annex 5, page 4

INTRODUCTION

Purpose

1 The primary purpose of this Guidance is to assist ships in planning for compliance
with the BWM Convention and the D-2 discharge standard when a type-approved ballast water
management system (BWMS) that has been properly installed, operated and maintained
encounters operational limitations or has difficulty meeting operational demand in challenging
water quality (CWQ) conditions. The Guidance may also serve as a practical operational guide
for ships and voyage planners in this regard.

2 This Guidance also includes sections intended to guide Administrations, port States
and BWMS manufacturers in providing appropriate support and oversight to ships before,
during and after CWQ operations.

3 This interim Guidance has been developed while the Committee takes steps through
the experience-building phase (EBP) associated with the BWM Convention (resolution
MEPC.290(71)) to improve the performance and reliability of BWMS.

4 This Guidance includes recommended steps that can be taken to restore or maintain
effective operation of a BWMS when operating in CWQ. These include steps to identify when
a system is inoperable owing to CWQ; actions to avoid bypass of the system; steps to recover
from bypass including steps to return to compliance with the D-2 discharge standard; and
planning, record-keeping and communication principles.

5 This Guidance does not address situations in which a BWMS is inoperable for reasons
unrelated to CWQ, or in which inadequate performance is due to installation, operation or
maintenance issues. Such situations should be addressed on a case-by-case basis in
consultation with the Administration of the ship and implicated port States (see also the
Guidance on contingency measures under the BWM Convention (BWM.2/Circ.62, as may be
revised)).

Principles

6 Ships, supported by BWMS manufacturers, should plan for circumstances where

CWQ may be experienced and include procedures informed by this Guidance in their approved
Ballast Water Management Plan (BWMP). This Guidance is not intended to reduce the
importance of selecting the most suitable BWMS, as known and available, for the
circumstances of the ship where appropriate. Relevant stakeholders may, for example, use
the INTERTANKO CWQ database1 until a universal platform becomes available.

7 When operating a BWMS in CWQ, encountering an operational limitation or

experiencing a challenge in satisfying operational demand does not indicate a BWMS failure.
A BWMS has warnings and alarms to protect the BWMS equipment and/or the ship and the
triggering of these set points or flow reductions demonstrates proper BWMS operation as
designed.

8 Triggers for implementing CWQ procedures should be included in the BWMP and
should be based on the performance and self-monitoring functions of the BWMS. The list of
triggers should be developed based on information provided by the BWMS manufacturer in
the Operations, Maintenance and Safety Manual (OMSM), based on the BWMS design and
operational limitation(s).

1
See document MEPC 81/4/11 and https://www.intertanko.com/search-article/articleview/pcwq-database

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 RESOLUTION MEPC.387(81) (adopted on 22 March 2024)
INTERIM GUIDANCE ON THE APPLICATION OF THE BWM CONVENTION TO SHIPS
OPERATING IN CHALLENGING WATER QUALITY CONDITIONS
MEPC 81/16/Add.1
Annex 5, page 5

9 CWQ triggers should be assessed on a voyage-by-voyage basis because water

quality challenges may vary: from berth to berth, with conditions on board the ship, and with
environmental factors such as organism density, tides and seasons.

10 Following a bypass event in a location with CWQ, decontamination to ensure that

subsequent discharges meet the D-2 performance standard may include ballast water
exchange through a BWMS (BWE+BWT). However, BWE+BWT alone may not be sufficient
to meet the standard. This risk may be mitigated by conducting ballast water flushing as
described in appendix 1.

11 Bypass should always be considered as the last resort and the BWMS should be used
as far as practicable to treat ballast water with CWQ. However, some BWMS are able to treat
ballast water at flow rates that are prohibitively low for practical, safe operations.

12 Ports are requested to take CWQ conditions into account and work with ships to plan
arrival, departure and berthing times that will accommodate the consistent use of BWMS at
expected ballasting rates. When ballasting rates are impacted by CWQ, ports are requested
to exercise flexibility and support the ship in using a BWMS as long as operational demand is
met (as defined in this Guidance and the ship's approved BWMP).

13 A ship fully applying this Guidance minimizes the risk of non-compliance with the D-2
standard at subsequent discharges. While this Guidance does not limit the rights of a port State
in verifying a ship's compliance with the Convention (including sampling), this Guidance should
be taken into account when prioritizing compliance verification activities.

14 Administrations and manufacturers of BWMS should collect information to improve

the Convention and support the development of BWMS performance improvements regarding
commonly encountered CWQ conditions. This information should be shared with the
Committee as appropriate.

Application

15 This Guidance is applicable to:

.1 ships that are required to meet the ballast water performance standard in
accordance with regulation B-3 of the BWM Convention;

.2 Administrations approving BWMPs in accordance with regulation B-1 and

applying articles 13 and 14 of the BWM Convention;

.3 port States applying articles 8 to 10 of the BWM Convention; and

.4 BWMS manufacturers defining troubleshooting procedures in the OMSM in

accordance with paragraph 4.8 of the BWMS Code.

Definitions

16 Challenging water quality (CWQ) refers to ambient uptake water having quality
parameters (including but not limited to high total suspended solids,2 or turbidity) that cause a
properly installed, maintained and operated type-approved BWMS to be temporarily inoperable
due to an operational limitation or an inability to meet operational demand. However,
temperature and salinity are not parameters that define CWQ.

2
Total suspended solids are defined as solids in water that can be trapped by a filter.

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 RESOLUTION MEPC.387(81) (adopted on 22 March 2024)
INTERIM GUIDANCE ON THE APPLICATION OF THE BWM CONVENTION TO SHIPS
OPERATING IN CHALLENGING WATER QUALITY CONDITIONS
MEPC 81/16/Add.1
Annex 5, page 6

17 Operational demand means the minimum BWMS flow rate defined in the BWMP that
will permit the ship to continue cargo operations while using the BWMS, which should be
no greater than 50% of the BWMS treatment rated capacity (TRC).3

18 Operational limitation means an automatic shutdown of the BWMS, a critical alarm for
which the BWMS OMSM directs a manual shutdown, or a safety-related circumstance that
requires the shutdown of the BWMS for the protection of the BWMS equipment, the ship or its
crew.4

19 Pre-emptive bypass means 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.

20 Reactive bypass means a BWMS bypass undertaken during a ballasting operation

upon reaching an operational limitation or encountering an inability to meet operational
demand.

GUIDANCE FOR SHIPS OPERATING IN CWQ

21 This part of the guidance is intended to inform the development of Ballast Water
Management Plans (BWMP), which should include ship-specific guidance and procedures
identified in the conceptual overview provided in figure 1. This planning is intended to facilitate
ship operations and efficiency by optimizing the performance of BWMS in CWQ, reducing the
need to bypass this environmentally protective equipment and decontaminate ballast tanks.

22 While the focus of this part is on planning, its specific guidance and example process
flow charts may also help ship crews reduce risks to the environment, human health, property
and resources when operating in CWQ. However, this guidance should be read in conjunction
with the ship-specific BWMP and OMSM.

3
Operational demand pertains to the ship.
4
Operational limitation pertains to the BWMS.

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 RESOLUTION MEPC.387(81) (adopted on 22 March 2024)
INTERIM GUIDANCE ON THE APPLICATION OF THE BWM CONVENTION TO SHIPS
OPERATING IN CHALLENGING WATER QUALITY CONDITIONS
MEPC 81/16/Add.1
Annex 5, page 7

CWQ process

Assessment
Determination that the BWMS is not performing e.g. indications from the self-monitoring system,
at its expected treatment rated capacity mechanical observations

e.g. verify valves, address alarms, clean, add

Ensure proper operation and maintenance of Troubleshooting
reagents, backflush, increase intensity, slow flow
BWMS and deploy measures to assist it and mitigation

Assess operational limitations e.g. consult BWMS self-monitoring system, and

and operational demands to establish CWQ CWQ triggering monitor BWMS flow rate

Take all additional steps possible before Alternatives to e.g. restrict flow to operational demand,
bypassing the BWMS bypass optimize BWMS for CWQ, load less ballast

Load the minimum amount of unmanaged water e.g. consider partial BWMS bypass, load
and limit the tanks and piping affected Bypass minimum safe amount and reposition ballast

Decontaminate tanks and piping to lower the e.g. conduct exchange, flushing and treatment,
Decontamination
risk of not meeting D-2 at next discharge preferably in mid-ocean

Regularly update the Ballast Water Record Book Record-keeping/ e.g. make BWRB entries throughout this process,
and inform future ports of any BWMS bypass communication and submit a pre-arrival reporting form

Figure 1: Conceptual overview of the CWQ process

Pre-planning

23 Operations in CWQ will be most efficient when the BWMP includes practical and
realistic measures specific to the ship that take into account this Guidance, the BWMS
technology installed on board, and specific instructions and procedures from the OMSM.

24 The approved BWMP should include a ship-specific definition of operational demand

based on paragraph 17 that identifies the sustained flow rate below which cargo operations
cannot practicably be continued by the ship. This flow rate should not be higher than 50% of
the treatment rated capacity of the BWMS unless the ship's safety or stability would
be affected. For example:

"On this ship, the operational demand to practicably permit continued cargo
operations without affecting the ship's safety or stability while using the BWMS is
defined by a sustained flow rate of ___ m3/h, which is 50% of the treatment rated
capacity of the BWMS."

25 Developing ship-specific process flow charts based on the appended samples and
manufacturer's guidance is recommended.

26 A detailed plan for at least the following items should be included in the ship-specific
BWMP and BWMS operating instructions, taking into account ship safety and the maintenance
and operation instructions in the OMSM. Further information and guidance on selected topics
from this list are included in the sub-sections below.

.1 Maintenance: Maintenance timetables and checklists for maintaining the

system in optimal condition for managing CWQ when it is encountered,
including:

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 RESOLUTION MEPC.387(81) (adopted on 22 March 2024)
INTERIM GUIDANCE ON THE APPLICATION OF THE BWM CONVENTION TO SHIPS
OPERATING IN CHALLENGING WATER QUALITY CONDITIONS
MEPC 81/16/Add.1
Annex 5, page 8

.1 crucial maintenance actions, such as those related to inspection,

cleaning, calibration, active substance monitoring, etc.; and

.2 ensuring the availability on board of sufficient approved spare parts,

Active Substances and neutralizing agents.

.2 Assessment: Indications from the BWMS self-monitoring system or a

mechanical observation that the BWMS is not performing at its expected
treatment rated capacity.

.3 Troubleshooting and mitigation: Procedures to identify and resolve

challenges linked to the operation and maintenance of the BWMS, as well as
ship-specific procedures for assisting and optimizing the BWMS in treating
CWQ, with a view to completing normal ballast water treatment without
bypassing the BWMS, giving consideration to operational demands.

.4 CWQ triggers: In case troubleshooting and mitigation is unsuccessful, a table

of critical alarms specific to the BWMS based on the OMSM indicating that
an operational limitation has been reached (see paragraph 18). This should
include ship-specific procedures to be taken when an alarm is encountered.

.5 Alternatives to bypass: Pre-planned actions, considerations and procedures,

taking into account the OMSM, that may clear operational limitations or allow
the BWMS to meet operational demands.

.6 Bypass procedure: Steps to be taken to bypass the BWMS, including

treatment of a fractional part of the ballast water stream and/or bypassing
only the inoperative part of the ballast water treatment process.

.7 Decontamination: Specific procedures for decontaminating ballast tanks

and/or piping to reduce the risk of bypassed water, with a view to meeting
the D-2 standard at subsequent discharges. Any use of the ballast water
exchange plus treatment (BWE+BWT) approach should be clearly detailed
in the approved BWMP.

.8 Communication: Procedure for informing the port State(s) that will receive
any ballast water discharge impacted by reactive bypass of the BWMS,
before arrival of the ship in such State(s).

.9 Record-keeping: How to record CWQ situations in the Ballast Water Record

Book (BWRB), in line with the Guidance on ballast water record-keeping and
reporting (BWM.2/Circ.80, as may be revised). The BWRB should provide a
detailed description of the ballast water management method(s) used, as
well as location and affected tanks (tank ID).

27 The BWMP should provide that, when a ship encounters CWQ, an evaluation of ship
safety should be conducted prior to the application of any steps to manage CWQ as included
in this Guidance. Any safety risks identified should be evaluated to determine mitigating
actions.

Assessment

28 CWQ may be impacting ballasting operations if the BWMS is not functioning at its
expected treatment rated capacity, and alarms indicating an operational limitation arise or the
BWMS is not meeting operational demand. A sample process for performing this assessment
is set out in process diagram 1 ("Assessment of BWMS operation") in appendix 2.

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 RESOLUTION MEPC.387(81) (adopted on 22 March 2024)
INTERIM GUIDANCE ON THE APPLICATION OF THE BWM CONVENTION TO SHIPS
OPERATING IN CHALLENGING WATER QUALITY CONDITIONS
MEPC 81/16/Add.1
Annex 5, page 9

29 Pre-emptively bypassing the BWMS based on historical CWQ issues experienced at

a location is discouraged because water quality conditions may vary by precise location, ship
and/or nearby port operations, time of day, tide, weather or seasonality. Through the
self-monitoring system, the BWMS is the most suitable and technical method to precisely
determine the water quality challenge at any moment and relieves the ship crew of this
determination.

30 However, if a pre-emptive bypass is warranted in the case of regular visits to a port

or location with known and recurring CWQ, this should be agreed in advance bilaterally
between the Administration of the ship and the port State receiving the ballast water
(see paragraph 52 below).

Troubleshooting and mitigation

31 If CWQ is impacting ballasting operations, as described in paragraph 28, then the

crew should implement ship-specific troubleshooting procedures set out in the BWMP and the
OMSM to ensure the system is being operated in accordance with proper procedure and the
manufacturer's instructions. For example, this may include steps such as verifying the correct
alignment of valves, that the BWMS is in the correct mode, and fully addressing any BWMS
warnings and alarms.

32 The crew should also follow ship-specific procedures in the BWMP and the OMSM to
verify that the BWMS has been properly maintained. For example, these procedures may
include ensuring that any necessary reagents have been introduced into the BWMS, that any
cleaning cycles have been run, and that no mechanical or electrical failures are present.

33 If the steps above indicate that the BWMS has been properly operated and
maintained, the crew should follow procedures in the BWMP and the OMSM to deploy
mitigating measures that assist the system in treating the water successfully. For example,
these may include manually operating any backflushing controls, applying suitable
backpressure at high differential filter pressures, maximizing UV intensity in the presence of
turbid water or low UV transmittance, progressively reducing ballast water flow rate to the point
of operational demand or operational limitation.

34 In planning troubleshooting and mitigation, refer to the ship's OMSM and the sample
process diagram 2 ("Challenging water quality process") in appendix 2.

CWQ triggers

35 The crew should implement CWQ actions when, despite maximizing all mitigating
measures, the BWMS delivers a critical alarm identified in the BWMP signalling that an
operational limitation has been reached (see paragraph 18), or the BWMS is not meeting
operational demand (see paragraph 17).

36 CWQ triggers relating to operational limitations should be based on the system design
limitations of the BWMS as tested during the type approval process, clearly identified in the
ship's approved BWMP, and should be developed with reference to the OMSM. CWQ triggers
may consist of relevant alarms concerning matters such as:

.1 the required UV transmittance or UV dose of the BWMS;

.2 the maximum allowable differential pressure across the filter to prevent

permanent damage to the filter element;

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 RESOLUTION MEPC.387(81) (adopted on 22 March 2024)
INTERIM GUIDANCE ON THE APPLICATION OF THE BWM CONVENTION TO SHIPS
OPERATING IN CHALLENGING WATER QUALITY CONDITIONS
MEPC 81/16/Add.1
Annex 5, page 10

.3 a reduction in flow rate that is below the minimum operating requirements of

the BWMS, as identified by the OMSM; and

.4 monitoring data of the BWMS when the self-monitoring system indicates the
BWMS is not operating normally owing to issues such as those listed below,
and that cannot be remediated through optimization of the BWMS in
accordance with the BWMP:

.1 variation of pressure in filters;

.2 UV transmittance or dosage and/or the levels of dissolved organic

carbon; and

.3 turbidity and/or total suspended solid that triggers an alarm of the

BWMS.

Table 1: Water quality parameters for challenging water

Potential CWQ Types of BWMS

Impacts
parameters affected
Turbidity Decreased light transfer through water due to UV, filtration
deflection from particles/organisms (UV
scatter), increased filter differential pressure
UV transmissivity Decreased penetration of UV light through UV
seawater
Dissolved organic Increased consumption of Active Substance, UV, Active Substance
carbon UV absorption
Particulate organic Increased consumption of Active Substance, UV, Active Substance
carbon UV scatter
Total suspended Increased consumption of Active Substance, UV, filtration, Active
solids (sediment UV scatter, increased filter differential Substance
and/or organism pressure
load)

37 The relevant CWQ triggers should be reviewed and amended, as applicable, in the
event of any change to the BWMS.

38 The crew should respond with the pre-planned steps in the BWMP and the OMSM for
managing any critical alarm or operational demand.

Alternatives to bypass

39 Alternatives should be tried before the ship bypasses a BWMS, because bypass
increases the risks ballast water poses to the environment, human health, property and
resources. Bypass also increases the operational workload for ship crew to perform alternative
management methods and subsequently return the BWMS and ship to normal operations for
D-2 compliance.

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 RESOLUTION MEPC.387(81) (adopted on 22 March 2024)
INTERIM GUIDANCE ON THE APPLICATION OF THE BWM CONVENTION TO SHIPS
OPERATING IN CHALLENGING WATER QUALITY CONDITIONS
MEPC 81/16/Add.1
Annex 5, page 11

40 Before the BWMS is bypassed, the officer designated in accordance with

regulation B-1.5 should:

.1 ensure that any BWMS alarm that could be ascribed to CWQ is not due to
other factors such as malfunction, maintenance, crew familiarity or
experience;

.2 ensure that the BWMP and OMSM have been followed in troubleshooting
the operation of the BWMS (see paragraph 31), verifying that the BWMS has
been properly maintained (see paragraph 32) and ensuring that applicable
mitigating measures have been applied (see paragraph 33) to optimize the
performance of the BWMS before any bypass;

.3 restrict the flow rate of the BWMS to the minimum level consistent with
operational demand (see paragraph 17); and

.4 consider persisting with using the BWMS in the challenging area to load the
minimum safe amount of ballast water and complete remaining ballasting at
a nearby less challenging location at a later time, taking into account the
ship's stability and cargo condition as well as expected weather conditions.

Bypass procedure

41 The sequence of steps for safely bypassing the BWMS in the BWMP and OMSM
should be followed. In undertaking an assessment of alternatives to bypassing the BWMS,
refer to sample process diagram 3 ("Alternatives to bypass") in appendix 2.

42 The crew should consider that partially managed or unmanaged ballast water loaded
through a bypass is likely to contaminate ballast tanks and piping systems with harmful aquatic
organisms and pathogens that pose a risk to the environment, human health, property and
resources. Therefore:

.1 consideration should be given to limiting the number of ballast tanks that will
be exposed to partially treated or unmanaged ballast water;

.2 consideration should be given to treating the greatest possible fraction of the

uptake water, by continuing to apply the BWMS to as much of the uptake
water stream as practicable;

.3 in cases where only one part of a BWMS treatment process is inoperable,

consideration should be given to applying the remainder of the treatment
process to the uptake water, if practicable; and

.4 only the minimum safe volume of ballast water should be taken on board
through the bypass following which, if necessary and practicable, the ship
should proceed to a nearby area where less challenging uptake water may be
obtained in order to complete ballasting using the BWMS as usual.

Decontamination

43 When a bypass is undertaken, the ship is still responsible for meeting the D-2
standard at subsequent discharge locations. The density of organisms at the location of uptake
may impact the ship's return to D-2 compliance following a bypass. The recovery steps within
this Guidance and the BWMP for decontaminating affected ballast tanks and piping should be
followed to mitigate risks to the environment, human health, property and resources.

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 RESOLUTION MEPC.387(81) (adopted on 22 March 2024)
INTERIM GUIDANCE ON THE APPLICATION OF THE BWM CONVENTION TO SHIPS
OPERATING IN CHALLENGING WATER QUALITY CONDITIONS
MEPC 81/16/Add.1
Annex 5, page 12

44 The approved BWMP should include a procedure for decontaminating ballast tanks,
taking into account the example procedure set out in appendix 1 and the sample process
diagram 4 in appendix 2.

45 Regulation B-4.3 does not apply to decontamination following a bypass of a BWMS,

in order to restore compliance to regulation D-2.

46 In the case of a ship operating in a sea area where ballast water exchange in
accordance with regulations B-4.1 and D-1 is not possible (e.g. an enclosed or semi-enclosed
sea) and no ballast water exchange area has been designated, the ship should follow any
instructions provided by subsequent port States to reduce the risk of discharging unmanaged
or partially unmanaged ballast water and/or residuals. Port States should take into account
adjacent or other States that may be affected by such instructions, as well as the safety
of ships.

Communication

47 Whenever a full or partial bypass of a BWMS is undertaken, the next State receiving
water from affected ballast tanks should be informed of the bypass, such as through a
pre-arrival ballast water reporting form5 when such a form is required. Any deviation from the
procedures in this Guidance or the BWMP should be noted in the communication.

Record-keeping

48 In instances when the BWMS has not operated as expected owing to CWQ and may
not be treating the water successfully, such circumstances carry greater environmental risk
and should be recorded in the Ballast Water Record Book, taking into account the Guidance
on ballast water record-keeping and reporting (BWM.2/Circ.80, as may be revised).

49 The ship's BWRB should include a description of:

.1 the reason why normal ballasting operations were stopped;

.2 any steps taken to optimize the treatment process and resolve BWMS
technical malfunctions;

.3 the operational demands that were not met and/or operational limitations
encountered (see paragraphs 17 and 18);

.4 the steps that were taken prior to a bypass being initiated (as relevant);

.5 the tanks which have received bypassed ballast water (tank ID);

.6 the date, time and location where the bypass took place; and

.7 the decontamination steps that were taken to recover from BWMS bypass as
per the approved BWMP, including: the start and end locations
(GPS coordinates) at which any flushing and/or exchange took place, the
start date and time; end date and time, the method of exchange and the
volume exchanged and/or flushed.

5
See the Guidance on ballast water record-keeping and reporting (BWM.2/Circ.80, as may be revised).

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 RESOLUTION MEPC.387(81) (adopted on 22 March 2024)
INTERIM GUIDANCE ON THE APPLICATION OF THE BWM CONVENTION TO SHIPS
OPERATING IN CHALLENGING WATER QUALITY CONDITIONS
MEPC 81/16/Add.1
Annex 5, page 13

GUIDANCE FOR ADMINISTRATIONS WITH RESPECT TO BALLAST WATER

MANAGEMENT PLANS AND CHALLENGING WATER QUALITY

50 Administrations should ensure that ships are fully prepared to encounter CWQ.
Approved BWMPs should be ship-specific, reflect the OMSM of the BWMS, and include
at least: equipment maintenance procedures and intervals, predetermined mitigating
measures that may preserve and optimize the treatment process in marginal conditions, a table
of critical alarms that justify CWQ action, ship-specific alternatives to bypassing the BWMS,
safe bypass procedures that minimize the exposure of tanks/piping to unmanaged water, and
a decontamination procedure that reflects this Guidance and is safe for the ship and crew.
Administrations should also ensure that crew familiarization includes relevant aspects of this
Guidance, BWMS operating instructions and the environmental risks of bypassing BWMS and
steps to avoid/minimize them.

51 Reactive bypasses (see paragraph 20) may be undertaken by the ship without
consulting the Administration or the next port State. Port States receiving water from affected
tanks should be notified before arrival (see paragraph 47).

52 Pre-emptive bypass (see paragraph 19) should be discouraged for the reasons set
out in paragraph 29. However, in cases where pre-emptive bypass may be appropriate, the
Administration should ensure this will not impair or damage the environment, human health,
property or resources of other States. In bilaterally agreeing to the pre-emptive bypass, the
Administration of the ship and the receiving port State should ensure that the pre-emptive
bypass will not impair or damage the environment, human health, property or resources of any
State. 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.

GUIDANCE FOR PORT STATE CONTROL OFFICERS WITH RESPECT TO SHIPS THAT
HAVE ENCOUNTERED CHALLENGING WATER QUALITY

53 When determining compliance with the Convention by a ship that has encountered
CWQ, a port State control officer should consult the BWMP, BWRB and crew. In determining
that the ship has done all it can to meet the D-2 standard, the officer should use professional
judgement in considering:

.1 the nature and degree of the challenge;

.2 whether challenges arose despite proper BWMS operation and

maintenance;

.3 whether steps were taken to avoid or limit the bypass of a BWMS, such as
efforts to mitigate challenges while continuing to use the BWMS;

.4 whether the ship and crew followed the procedures in the BWMP and
recorded this in the BWRB; and

.5 whether decontamination was properly undertaken following any bypass.

54 Port States should consider that a ship fully applying this Guidance is minimizing its
risk of non-compliance with the D-2 standard at subsequent discharge locations.

I:\MEPC\81\MEPC 81-16-Add.1.docx
 RESOLUTION MEPC.387(81) (adopted on 22 March 2024)
INTERIM GUIDANCE ON THE APPLICATION OF THE BWM CONVENTION TO SHIPS
OPERATING IN CHALLENGING WATER QUALITY CONDITIONS
MEPC 81/16/Add.1
Annex 5, page 14

GUIDANCE FOR BWMS MANUFACTURERS WITH RESPECT TO PARTICIPATION IN

PRE-PLANNING

55 Manufacturers of BWMS should ensure that the self-monitoring system of the BWMS
records and provides clear indications to the crew on the degree of challenge being
experienced by the BWMS. Specific CWQ instructions and procedures should be included in
the OMSM to assist the ship and Administrations in developing and approving BWMPs,
which should include specific, realistic actions the crew can follow to optimize the efficiency
and performance of the BWMS. The OMSM should also include a table of unambiguous
triggers necessitating actions in CWQ that could compromise the treatment process.

56 Manufacturers of BWMS should support providing appropriate technical information

and possible actions to be taken in CWQ scenarios that are appropriate for the installed BWMS
for inclusion in the ship-specific BWMP. This may include, but is not limited to:

.1 simple, easy to use operating instructions for the crew to allow prompt
identification of BWMS operational issues and an understanding of BWMS
alarms and relevant actions to be taken by crew when an alarm arises;

.2 clearly identifying critical alarms in the OMSM and BWMP;

.3 providing clear troubleshooting and mitigation instructions in the OMSM and

BWMP for crews to use when CWQ is encountered; and

.4 actions that can be taken pre-emptively to support the BWMS in successfully

operating even in CWQ conditions (paragraph 33).

57 Manufacturers of BWMS are encouraged to take efforts to collect relevant information

and/or data from ship operators, as available, about BWMS operation in CWQ (including in
specific water qualities, and/or at specific ports and locations, if appropriate) for the purposes
of informing and guiding relevant stakeholders (e.g. ships, Administrations, port States, IMO)
with a view to optimizing the operation of BWMS in CWQ. Ship crews are encouraged to
cooperate with BWMS manufacturers to support collection of information and/or data regarding
BWMS operations in CWQ.

I:\MEPC\81\MEPC 81-16-Add.1.docx
 RESOLUTION MEPC.387(81) (adopted on 22 March 2024)
INTERIM GUIDANCE ON THE APPLICATION OF THE BWM CONVENTION TO SHIPS
OPERATING IN CHALLENGING WATER QUALITY CONDITIONS
MEPC 81/16/Add.1
Annex 5, page 15

APPENDIX 1

EXAMPLE DECONTAMINATION PROCEDURE

1 The following steps are intended to promote a return to compliance with

regulation D-2 after a BWMS has been bypassed.

2 Having loaded the minimum volume of ballast water, proceed to the first suitable
location for the discharge of ballast water from the following list:

.1 a location specified in regulation B-4.1; or

.2 a location specified in regulation B-4.2 by the port State in whose waters the
BWMS is bypassed; or

.3 a location specified in regulation B-4.2 by the port State in whose waters the
ballast water is to be discharged.

3 Replace the ballast water in each contaminated tank through ballast water exchange
(in accordance with the operational and safety provisions of the BWMP), flushing and
treatment.

.1 In the case of a ship using the sequential method, which is preferred:

.1 the ballast water should be fully discharged through the

neutralization, if applicable, and/or treatment process for the
deballasting operation of the BWMS, if technically feasible;

.2 the stripping pump (eductor) should be used to remove residual

water from the tank;

.3 the concentration of organisms in remaining residual ballast water

and sediments should be reduced by flushing the tank using the
following sequential steps, if allowed and/or required by the
receiving port State:6

.1 the addition of treated water to the ballast tanks

(decontamination will be most effective with the addition of
as much treated mid-ocean water into the tank as is safe
for the ship and crew, at minimum an amount that will cover
the entire bottom of the ballast tank);

.2 the mixing, through the motion of the ship, of the added

water with the residual ballast water and any sediments
that have settled in the tanks; and

.3 the release of the mixed waters; and

6
The concentration of organisms in unmanaged ballast water (e.g. resulting from a bypass) is expected to
exceed the D-2 standard. The purpose of flushing the emptied tanks with treated water is to reduce the
concentration of organisms remaining in residual unmanaged ballast water and sediments. This practice has
been shown to reduce the risk of subsequent ballast water discharges and can promote a return to D-2
compliance after the tank is refilled with treated water during exchange.

I:\MEPC\81\MEPC 81-16-Add.1.docx
 RESOLUTION MEPC.387(81) (adopted on 22 March 2024)
INTERIM GUIDANCE ON THE APPLICATION OF THE BWM CONVENTION TO SHIPS
OPERATING IN CHALLENGING WATER QUALITY CONDITIONS
MEPC 81/16/Add.1
Annex 5, page 16

.4 the tank should be refilled with treated ballast water.

.2 The use of the flow-through or dilution method is not recommended.

However, in the case of a ship which must use the flow-through or dilution
method:

.1 a sufficient volume of treated uptake water should be pumped

through to reduce the concentration of organisms in the tank to the
standard in regulation D-2, at least 1.66 times the volume specified
by regulation D-1.2, if required by the receiving port State;7 and

.2 to reduce the risk that non-neutralized Active Substances could

damage the environment, human health, property or resources, a
ship with a BWMS that uses Active Substances should only conduct
this exchange in a location described in regulation B-4.1 and in
compliance with any precautions in the approved BWMP designed
to ensure the safety of the ship and crew.

.3 Record the ballast water exchange and flushing operations in the BWRB.

7
The concentration of organisms in unmanaged ballast water (e.g. resulting from a bypass) is expected to
exceed the D-2 standard. Pumping through 1.66 times the normal volume of treated ballast water can
promote a return to D-2 compliance by ensuring that a sufficient proportion of the unmanaged water
(and the organisms contained within it) has been replaced with the treated water.

I:\MEPC\81\MEPC 81-16-Add.1.docx
 RESOLUTION MEPC.387(81) (adopted on 22 March 2024)
INTERIM GUIDANCE ON THE APPLICATION OF THE BWM CONVENTION TO SHIPS
OPERATING IN CHALLENGING WATER QUALITY CONDITIONS
MEPC 81/16/Add.1
Annex 5, page 17

APPENDIX 2

SAMPLE PROCESS DIAGRAMS FOR SHIPS BALLASTING IN AREAS WITH

CHALLENGING WATER QUALITY

Process diagram 1: Assessment of BWMS operations

Start BWMS for ballasting

operations

Does the BWMS Does BWMS

function at the indicate a critical
expected alarm as detailed in
the system's
No Operations,
Treatment Rated
Maintenance and
Capacity (TRC)
Safety Manual
during entire
(OMSM)? Yes
ballasting
operation?

No

Yes
Consult system's
OMSM for
troubleshooting Consult system's OMSM and
and mitigation ship's Ballast Water
steps to improve Management Plan (BWMP) for
performance needed actions

Yes Is the
BWMS at Log alarms and any shutdowns
Continue ballasting operations
least in Ballast Water Record Book.
meeting
operational
demand?*

Proceed to "Challenging
Complete ballasting No water process"
operations using the
BWMS; proceed to
discharge port

* Operational demand means the minimum BWMS flow rate defined in the approved BWMP that will permit the ship to continue
cargo operations while using the BWMS, which should be no greater than 50% of the BWMS treatment rated capacity (TRC).

I:\MEPC\81\MEPC 81-16-Add.1.docx
 RESOLUTION MEPC.387(81) (adopted on 22 March 2024)
INTERIM GUIDANCE ON THE APPLICATION OF THE BWM CONVENTION TO SHIPS
OPERATING IN CHALLENGING WATER QUALITY CONDITIONS
MEPC 81/16/Add.1
Annex 5, page 18

Sample process diagram 2: Challenging water quality process

Determine reason for BWMS critical
Process Diagram
alarm / shutdown 3:
/ not meeting
operational demands
Consult port State and
Administration regarding
potential contingency
Consult with measures (BWM.2/Circ.62)
manufacturer
Is the BWMS free
of mechanical or
No and/or BWMS Has BWMS
Operations been
electrical
Maintenance and
equipment
Safety Manual
repaired? No
failures?
(OSMS) to repair
system
Yes
Yes

Are all valves No Properly align

aligned system for function Resume normal ballasting
correctly? and restart BWMS operations

Yes

Is BWMS in No Place BWMS in

proper mode and proper mode,
is full power increase system to
available? full power

Does BWMS
Yes return to
Yes
normal
function?

Has all No Complete all

maintenance outstanding or
been completed deferred
on BWMS? maintenance No

Record any
Yes shutdowns and
alarms in Ballast
Water Record
Book

Have all
troubleshooting No Troubleshoot
procedures as per BWMS as per
OMSM and BWMP OMSM and BWMP
been completed?

Yes Water ship is

encountering is
outside of BWMS
operational
limitations (CWQ)
Have all mitigation
measures outlined in OMSM No Implement
and Ballast Water mitigation
Management Plan (BWMP) measures as per
been implemented? OMSM and BWMP

Proceed to "Alternatives to bypass"

process diagram
Yes

I:\MEPC\81\MEPC 81-16-Add.1.docx
 RESOLUTION MEPC.387(81) (adopted on 22 March 2024)
INTERIM GUIDANCE ON THE APPLICATION OF THE BWM CONVENTION TO SHIPS
OPERATING IN CHALLENGING WATER QUALITY CONDITIONS
MEPC 81/16/Add.1
Annex 5, page 19

Sample process diagram 3: Alternatives to bypass

Evaluate alternatives to bypass

Is ballasting critical
for safety or due to No Avoid ballasting until BWMS is
operational fully operational or CWQ is no
demand of the longer observed
ship?

Yes

Is partial treatment No
possible? Bypass the BWMS

Yes

Fully treat the greatest

possible fraction of the
Record bypass in
uptake water or
Ballast Water Record
bypass only the
Book
inoperable portions of
the BWMS

Take on the minimum

ballast required to
maintain safety and
operational demand of
the ship

Ballast to the minimum

number of tanks to
maintain the safety
and operational
demand of the ship

Proceed to "Managing ballast

water following a BWMS bypass"
process diagram

I:\MEPC\81\MEPC 81-16-Add.1.docx
 RESOLUTION MEPC.387(81) (adopted on 22 March 2024)
INTERIM GUIDANCE ON THE APPLICATION OF THE BWM CONVENTION TO SHIPS
OPERATING IN CHALLENGING WATER QUALITY CONDITIONS
MEPC 81/16/Add.1
Annex 5, page 20

Sample process diagram 4: Decontamination: managing ballast water following

a BWMS bypass
Ballast water is not
To manage ballast water expected to meet D-2.
***
following a BWMS bypass Consult next port of call
event prior to arrival for
instructions, taking into
account BWM.2/Circ 62

No
Does the discharge
port have an area
for ballast water Yes
exchange in
Was system accordance with
No Is the Yes regulation B-4.2?
system bypassed due
repaired? to mechanical
failure?
Yes

Contact BWMS No No
manufacturer to
provide support to
repair BWMS at next
port of call
Does the uptake
port have an area Yes
for ballast water
exchange in
accordance with
regulation B-4.2?

No

Can the ship safely Can the ship safely

No conduct ballast
conduct ballast
water exchange water exchange
(BWE) in (BWE) in
accordance with accordance with
regulation B-4.1.1? regulation B-4.1.2?

Yes
Ballast water is not Yes Conduct BWE+BWT* in
expected to meet D-2. Conduct BWE+BWT* in accordance with the ship's
Consult next port of call accordance with the ship's BWMP in designated area
prior to arrival for BWMP before entering next port
instructions, taking into
account BWM.2/Circ 62

Inform the next State receiving water from affected ballast tanks of the bypass, such as through a pre-arrival
ballast water reporting form when such a form is required. Any deviation from the procedures in this guidance or
the BWMP should be noted in the communication.

* For decontamination purposes, BWE+BWT is to be done in accordance with the OMSM, approved Ballast Water Management Plan, and best practices. For the sequential
method, ballast tanks should be emptied, residual ballast water and sediments should be managed (by flushing the tank with treated water, if allowed and/or required by the
receiving port State), and then the tank should be refilled with treated water. For non-sequential methods, a sufficient volume of treated uptake water should be pumped
through to reduce the concentration of organisms in the tank to the standard in regulation D-2, at least 1.66 times the volume specified by regulation D-1.2, if required by the
receiving port State. The BWMS should be used during emptying of contaminated tanks, as well as subsequent uptakes, flushing and discharges during decontamination, if
technically feasible. See appendix 1.
***

I:\MEPC\81\MEPC 81-16-Add.1.docx
 RESOLUTION MEPC.387(81) (adopted on 22 March 2024)
INTERIM GUIDANCE ON THE APPLICATION OF THE BWM CONVENTION TO SHIPS
OPERATING IN CHALLENGING WATER QUALITY CONDITIONS