MARPOL Annex IV – Regulations for the Prevention of Pollution by

MARPOL Annex IV – Regulations for the

Prevention of Pollution by Sewage from Ships

Sewage, which is a water-carried waste, contains a

significant proportion of potentially disease-causing

microbes known as pathogens. If sewage is released into the

sea, it can cause a threat to the environment and serious

health hazards. It is therefore necessary that its discharge

isregulated.

This article aims to provide information on why releasing

untreated sewage into the sea is hazardous and guidance on

the regulations that control pollution of the sea by sewage.

Hazards of releasing untreated

sewage in the sea

Ships produce waste water in two

categories:

• Grey waste water is generated

by domestic activities such as

using sinks and showers, or doing

laundry and dishwashing.

• Black waste water contains

drainage and other wastes from

any form of toilets or urinals and

from spaces containing living

animals. It also includes medical

discharges generated by a ship’s

hospital, dispensary, etc.

The amount of waste water reaching

the sea is of particular concern as it

affects the marine environment.

Black waste water in particular is

naturally rich in both phosphorous

and nitrogen, which encourages the

excessive growth of plants and algae,

creating toxic algae ‘blooms’. These

algae cause oxygen depletion when

they decompose. The higher the

discharged concentration, the more

this reaction takes place and the lower

the amount of oxygen available for

fish and other aquatic animals and

plants, killing larger marine life.

Waste water also introduces

pathogenic bacteria and viruses, and if

discharged into coastal waters, it poses

a risk to public health for swimmers and

those eating contaminated seafood.

Sewage regulations

The principal international instrument

regulating discharges of waste water

from vessels is Annex IV of MARPOL.

Ships of 400gt and above engaged in

international voyages, or which are

certified to carry more than 15 persons,

are required to be fitted with either:

• an approved sewage treatment

plant

• an approved sewage comminuting

and disinfecting system

• a sewage holding tank to control the

discharge of sewage into the sea.

The discharge of sewage or black

water into the sea is prohibited,

except in the following cases:

• Untreated sewage may only be

discharged at a distance of more

than 12nm from the nearest land,

provided that sewage held in

holding tanks is not discharged

instantaneously, but at a moderate

rate when the ship is en route

and proceeding at a speed of

not less than 4 knots. MEPC

resolution157(55) provides

recommendations for the rate

of discharge to be used.

• Comminuted and disinfected

sewage may be discharged at a

distance of more than 3nm from

the nearest land, so long as an

approved system is used.

Akshat Arora

Marine Surveyor

+65 6506 2809

[email protected]

Legend

MARPOL nearest land

Baseline

• Effluent from an IMO-approved

sewage treatment plant may be

discharged at any location providing

the effluent does not produce

visible floating solids or cause

discolouration of the surrounding

water. MEPC resolution227(64)

provides guidelines on the

implementation of effluent

standards and performance tests

for sewage treatment plants.

Nearest land

The term ‘nearest land’ means the

baseline from which the territorial

sea of the territory in question

is established. In Australia, this

extends up to the outer edge of the

Great Barrier Reef, and no discharge

of any type is permitted in the

area of the Great Barrier Reef.

MARPOL Annex IV – Regulations for the

Prevention of Pollution by Sewage from Ships

continued

Special area

In July 2011, the IMO (through MEPC

resolution200(62)) designated

the Baltic Sea as a ‘special area’

for sewage from passenger ships.

The decision entered into force on

1 January 2013 and this is the only

designated area as specified under

MARPOL Annex IV. In the special

area, the discharge of sewage

from passenger ships is prohibited

unless the ship has in operation an

approved sewage treatment plant

that meets the applicable additional

effluent standards as specified

under MEPC resolution 227(64).

As agreed during the 69th session of

MEPC in April 2016, stricter discharge

restrictions will apply from 1 June

2019 for new passenger ships (built on

Australian coastline

or after 1 January 2016). For existing

passenger ships, the date is set as 1

June 2021. Single voyages of passenger

ships into and out of Russian territorial

waters east of the 28°10´ longitude

which do not call at any other ports in

the Baltic Sea will get a further two-

year grace period until 1 June 2023.

Alternatively, sewage from passenger

ships may be discharged to reception

facilities in ports. The status as a

special area has now also become fully

effective after all states bordering

the Baltic Sea have reported to

the IMO that sufficient reception

facilities for sewage from passenger

ships are available in their ports.

This requirement does not apply to

cargo ships.

Local regulations

In addition to international standards

established under MARPOL Annex IV,

some jurisdictions also regulate sewage

discharges. For example, in the United

States, a variety of vessel discharges

(including sewage and grey water) are

regulated through the EPA’s Clean

Water Act (CWA) National Pollutant

Discharge Elimination System (NPDES)

program. Under this act, specific

areas are designated as ‘no-discharge

zones’ (NDZs). Sewage discharges

are prohibited in these areas.

Sewage treatment plants on ships

International maritime laws require

black waste water to be treated before

discharge overboard. Treatment

of waste water can be carried out

separately for grey and black waste

water, or both streams can be

processed by a shared system.

In recent years, there has been an

increased focus on the condition

and operation of sewage treatment

plants or sewage comminuting and

disinfecting systems by the Port

State Control officers. A number of

ships have been detained because of

improper operation and maintenance

of sewage treatment systems.

The most common errors are the

inadequate usage or non-functioning

of sewage treatment plants, and

unauthorised modifications of sewage

treatment systems. As mentioned

earlier, ships are only allowed to

discharge sewage in ports if they use

an IMO-approved sewage treatment

plant. Comminuted and disinfected

sewage using an approved system

must be discharged at a distance of

more than 3nm from the nearest land.

There have been cases where the

authorities have levied fines on ships

for discharging untreated sewage in

port because the sewage treatment

plant was bypassed or the overboard

discharge valve had seized up or was

kept in ‘open to sea’ position. Any

malfunction of the equipment or

non-compliance with the approved

drawings may result in an invalid

International Sewage Pollution

Prevention Certificate and, as such,

is a violation of MARPOL Annex IV.

It is therefore essential that ships’

crews are aware of the MARPOL Annex

IV requirements and familiar with the

proper operation of the shipboard

sewage treatment system. It is also

important that regular maintenance

of the system is carried out, and

modifications (if any) should only

be undertaken following approval

from the class on behalf of the

administration (the ship’s flag state).

Members are reminded that, other

than in cases of purely accidental

discharge, P&I cover for fines

related to MARPOL violations is only

available on a discretionary basis. We

recommend members to proactively

report any equipment malfunction

to the vessel’s flag state and/or

class, and all reasonable actions

must be taken to prevent discharge

of untreated sewage overboard.