Resolution
MEPC.157(55)
RECOMMENDATION ON STANDARDS FOR THE RATE OF DISCHARGE OF UNTREATED SEWAGE FROM
SHIPS
(Adopted on 13 October 2006)
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.
Annex.
RECOMMENDATION ON STANDARDS FOR THE RATE OF DISCHARGE OF UNTREATED SEWAGE FROM
SHIPS
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.
2.1 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.
3.1 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.
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.
______________
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.
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.
6.1 Before undertaking a sewage discharge in
accordance with this standard, the crew member responsible for sewage
operations should