MEPC 55/23

ANNEX 14

Page 1

ANNEX 14

RESOLUTION MEPC.157(55)

Adopted on 13 October 2006

RECOMMENDATION ON STANDARDS FOR THE RATE OF DISCHARGE

OF UNTREATED SEWAGE FROM SHIPS

THE MARINE ENVIRONMENT PROTECTION COMMITTEE,

RECALLING Article 38(a) of the Convention on the International Maritime Organization 

concerning the functions of the Marine Environment Protection Committee (the Committee)

conferred upon it by international conventions for the prevention and control of marine pollution,

NOTING resolution MEPC.115(51) by which the Committee adopted the revised

MARPOL Annex IV, which entered into force on 1 August 2005,

NOTING ALSO the provisions of regulation 11.1.1 of MARPOL Annex IV,

RECOGNIZING that untreated sewage that has been stored in holding tanks shall not be

discharged instantaneously but that the discharge is to be undertaken at a moderate rate approved 

by the Administration based upon the standards developed by the Organization,

HAVING CONSIDERED the recommendations made by the Sub-Committee on Bulk

Liquids and Gases at its tenth session,

1. ADOPTS the Recommendation on standards for the rate of discharge of untreated sewage 

from ships, the text of which is set out in the Annex to the present resolution;

2. RECOMMENDS member Governments to accept the rate of discharge based upon the

annexed Standards,

3. ENCOURAGES operators of ships that may have high discharge requirements to keep

calculations of actual discharges to demonstrate compliance to the Administration and to port or 

coastal State authorities.
MEPC 55/23

ANNEX 14

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ANNEX

RECOMMENDATION ON STANDARDS FOR THE RATE OF DISCHARGE

OF UNTREATED SEWAGE FROM SHIPS

1 INTRODUCTION

1.1 Regulation 11.1.1 of the revised Annex IV of MARPOL 73/78 requires that untreated

sewage, which may be discharged at more than 12 nautical miles from the nearest land,

should not be discharged instantaneously but at a moderate rate of discharge when the

ship is en route and proceeding at a speed not less than 4 knots, while the rate should be

approved by the Administration based upon standards developed by the Organization. 

This Recommendation provides the standard and guidance for the approval and

calculation of a moderate rate of discharge.

1.2 A moderate rate of discharge applies to the discharge of untreated sewage that has been

stored in holding tanks.

1.3 This standard does not incorporate the dilution of sewage with water or greywater into

calculations of the discharge rate. Therefore the rate is a conservative estimate and it is

recognised that discharges of sewage in accordance with this standard will present a

higher level of protection to the marine environment due to mixing prior to the actual

discharge in addition to the mixing action of the ship’s wake.

2 DEFINITIONS

2.1 Swept volume means ship breadth x draft x distance travelled.

2.2 Untreated sewage means sewage that has not been treated by a type approved sewage

treatment plant, or that has not been comminuted and disinfected.

3 DISCHARGE RATE 

3.1 The maximum permissible discharge rate is 1/200,000 (or one 200,000th part) of swept

volume as follows:

DRmax = 0.00926 V D B

Where:

DRmax is maximum permissible discharge rate (m3/h)

V is ship’s average speed (knots) over the period

D is Draft (m)

B is Breadth (m)

3.2 The maximum permissible discharge rate specified in 3.1 refers to the average rate as

calculated over any 24 hour period, or the period of discharge if that is less, and may be

exceeded by no more that 20% when measured on an hourly basis.
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ANNEX 14

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4 APPROVAL OF RATE BY ADMINISTRATION

4.1 The Administration should approve the rate of discharge specified in 3.1 based upon the

ship’s maximum summer draft and maximum service speed1. Where sewage is to be

discharged at a different combination of draft and speed one or more secondary discharge 

rates may also be approved2.

5 METHOD OF CALCULATION

5.1 The calculated swept volume of the ship is to be determined for drafts up to and including 

the summer draft assigned in accordance with Article 3 of International Convention on

Load Lines, 1966. 

5.2 Where a ship is to discharge sewage from a holding tank using a pump calibrated at a

fixed rate, the pump can either be:

- calibrated at a the rate permitted at 4 knots; or

- calibrated for a specific minimum ship’s speed in excess of 4 knots.

5.3 Where the intended actual discharge rate exceeds that permissible at 4 knots, the actual

discharge rate may need to be reduced or the speed increased. The rate and speed is to be 

detailed in the approval issued by the Administration. 

6 COMPLIANCE WITH THE RATE

6.1 Before undertaking a sewage discharge in accordance with this standard, the crew

member responsible for sewage operations should ensure that the ship is en route, is more 

than 12 nautical miles from the nearest land and the navigation speed is consistent with

the discharge rate that has been approved by the Administration. Ships with high

discharge requirements are encouraged to keep notes of calculations of the actual

discharges to demonstrate compliance with the approved rate.

_________________

1

The attention of ship operators and personnel is drawn to the reduction in permissible rate of discharge at reduced draft

and/or speed.

2

Presentation may be tabular, refer to table below. For ships other than those having a high requirement for untreated sewage 

discharge, such as passenger ships and livestock carriers, the discharge rate criterion will generally not be exceeded at ship

speed of 4 knots.

DISCHARGE RATE (m3/h)

SPEED (kt) 4 6 8 10 12

DRAFT (m)

5 4.63 6.94 9.26 11.57 13.89

6 5.56 8.33 11.11 13.89 16.67

7 6.48 9.72 12.96 16.20 19.45

8 7.41 11.11 14.82 18.52 22.22

9 8.33 12.50 16.67 20.83 25.00

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