Marine Pollution Control
Marine Pollution Control
Marine Pollution Control
In 1954, the first international convention for the prevention of pollution of the
sea by oil was adopted (OILPOL 1954). OILPOL 1954 established zones
prohibiting discharge of oil and oily mixtures containing more than 100ppm of
oil.
The IMO became responsible for this convention when it was established in 1959.
The IMO then carried out a worldwide inquiry into the extent of oil pollution, the
availability of shore reception facilities and research on methods of combating
pollution by oil. As a result of this survey the IMO convened a conference in 1962
which extended the application of the 1954 convention to ships of lesser gross
tonnage, and increased the prohibited zones.
Several amendments were made to the 1954 OILPOL convention until 1973. In
1973 the IMO assembly convened an international conference to adopt a new
convention MARPOL 73. This convention dealt with all forms of marine
pollution.
There are six annexes that deal with marine pollution and they are:
Annex I, which deals with oil pollution:
Annex II, which is concerned with pollution by noxious liquid
substances (such as chemicals)
Annex III, containing regulations for the prevention of pollution
by harmful substances in packaged form (such as plastic)
Annex IV which deals with sewage discharges
Annex V, which deals with garbage disposal
Annex VI, which deals with air pollution
The new amendments make it possible for ships to be inspected when in the ports
of other states that are signatories to the convention to ensure that crews are able
to carry out essential shipboard procedures relating to marine pollution
prevention.
Marine Pollution Control/MEP1/November 2017
The oil content of the effluent from machinery spaces ships of over 400
gross tons is not to exceed 15 ppm.
The instantaneous rate of discharge of effluent with oil content from cargo
spaces of oil tankers is not to exceed 30litres per nautical mile.
Vessels constructed before 1993 had to comply with the above requirements by
July 1998.
Special guidelines for the discharge of noxious liquid substances are detailed
in the Ship’s procedures and arrangements manual for the carriage of bulk
liquid substances.
Annex I (oil): the Mediterranean Sea, the Baltic Sea, the Black Sea, the Red Sea,
the Gulfs area, the Gulf of Aden, the Antarctic.
Annex V (garbage): Baltic Sea, Mediterranean Sea, Black Sea, Red Sea, Gulfs
area, North Sea, Antarctic, Wider Caribbean region.
A new protective zone around UK coasts, in which virtually all oil pollution from
ships will be banned, came into force on 1 August 1999. The International
Maritime Organisation has designated the seas around the UK and the north west
European coastlines a special area.
MARPOL certificate requirements for vessels
International Oil Pollution Prevention Certificate (IOPP)
MARPOL annual survey certificate.
Ballast water
Ballast water is usually carried in special tanks in order to ensure stability of the
ship when the ship is not carrying a full load of cargo. The water is usually
discharged when the ship arrives to load a new cargo. The ballast water is usually
taken on board in the port where the cargo was last discharged.
The problems that have been caused by the discharge of ballast water includes:
Pollution
Spreading of diseases (such as cholera)
Ecological impact on native species by the introduction of
parasites and other foreign species.
Research is currently being conducted with ballast water management and two
methods presently being evaluated are:
Activity 1
Figure 1.1 shows a typical oily water separator. The oily bilge water is pumped to
the first stage of the separator by the bilge pump. Due to the differing densities of
oil and water, the oil will tend to separate to the upper part of the chamber of the
first stage. Further separation occurs as the liquid passes through a series of
plates. The oil droplets will collect on the underside of the plates and travel
upwards agglomerating in the baffles. The large oil globules will then separate
and move to the top of the chamber.
The water from the first stage will then flow into the second stage. The coalescer
filter elements in the second stage will further separate out any remaining oil.
A level sensing probe monitors the oil that is collected at the top of the chambers
and at a predetermined level opens a valve to discharge the oil to a separated oil
tank.
The water from the second stage is then discharged overboard. The water that is
being discharged overboard is continuously sampled through a monitor. If the oil
content in the discharge should exceed 15ppm, an alarm will sound and the
discharge from the separator will be automatically diverted to a holding tank
stopping the discharge to the sea.
Marine Pollution Control/MEP1/November 2017
Figure 1.2 shows a oil in water content monitor using direct light. A strong light
shines through a sampling chamber onto a photocell. The amount of light falling
on the photocell will be affected by the amount of oil particles in the sample. The
amount of light falling on the photocell is compared with that of direct light
falling onto a reference cell and the comparator circuit registers the difference on
a meter calibrated to show oil content. The circuitry maybe configured to trigger
an alarm and operate an automatic stopping device for overboard discharge.
Activity 2
When a ship is to be bunkered the chief engineer will prepare a bunkering plan.
This plan will include the following:
Quantity of oil to filled in each tank in cubic metres and the expected final
ullage.
Overflow arrangements to be used.
It is the bunkering engineer’s duty to be familiar with the bunker tanks, valves
and overflow system of the vessel. He must further familiarise himself with the
bunker plan detailed by the chief engineer.
Every vessel is required to have on board an oil pollution emergency plan. The
plan must list the crew members and outline their duties with respect to a
shipboard emergency during bunkering.
Ship’s Name
Berth Port
is not considered to be applicable a note to that effect should be inserted in the remarks
column.
- The presence of this symbol in the columns ‘Ship’ and ‘Terminal’ indicates that checks
shall be carried out by the party concerned.
The presence of letters A and P in the column ‘Code’ indicates the following:
A – The mentioned procedures and agreements shall be in writing and signed by both
parties.
P – In the case of a negative answer the operation shall not be carried out without the
permission of the Port Authority.
T
E
S R C
H M O
PART A I I D
P N E
Bulk liquids - General A Remarks
L
A1 Is the ship securely moored?
A2 Are emergency towing wires correctly
positioned?
A3 Is there safe access between ship and
shore?
A4 Is the ship ready to move under its own
power?
A5 Is there an effective deck watch in
attendance and adequate supervision
on the terminal?
A6 Is the agreed ship/shore
communication system operative?
A7 Have the procedures for cargo, bunker
and ballast handling been agreed?
A8 Has the emergency shutdown
procedure been agreed?
A9 Is the fire fighting equipment on board
and ashore positioned and ready for
immediate use?
A10 Are bunker hoses / arms in good
condition and properly rigged?
A11 Are scuppers plugged and drip trays
in position on board and ashore?
A12 Are unused bunker connections
blanked?
A13 Are overboard discharge valves not in
Marine Pollution Control
The biological sewage treatment plant works by aerating the sewage by the use of
an air blower. The oxygenated sewage produces bacteria which digest the sewage
to produce a harmless sludge. This type of bacteria is termed aerobic.
The raw sewage is broken up into extremely small particles by the mascerator and
enters the aeration tank through a screen. The sewage is then aerated and agitated
by the air from the blower. The bacteria residing in the plant will digest the
sewage converting it into sludge and water over a period of time.
The liquid in the aeration tank then flows to the settling tank where the sludge
settles and remaining effluent flows to the chlorination and collection tank. The
effluent must be disinfected by chlorination in order to reduce the coliform count
to acceptable levels. The chlorinator uses Sodium hypochlorite tablets in
perforated plastic tubes and dissolves in the effluent. The effluent is retained in
the collection tank for disinfection for about 1 hour before being discharged
overboard.
It is extremely important that the aeration process is not stopped at any stage as
a different bacteria is produced when there is a lack of oxygen. This type of
bacteria is called anaerobic bacteria. Anaerobic bacteria also digests sewage
but in the process generates hydrogen sulphide and methane gases. These gases
are toxic and flammable. Hydrogen sulphide gas has a similar smell to rotten
eggs and extreme care must be exercised if the presence of hydrogen sulphide
gas is detected.
Marine Pollution Control
Activity 3
All oil carrying ships are required to be capable of operating the method of
retaining oily wastes on board through the "load on top" system or for discharge
to shore reception facilities. This involves the fitting of appropriate equipment,
which may include an oil discharge monitoring and control system, oily water
separation equipment and filtering system, slop tanks, sludge tanks, piping and
pumping arrangements.
During discharging of a crude oil cargo the tanks are washed with high pressure
nozzles using a portion of the cargo. Crude oil from the cargo is sucked through
fixed piping to a tank cleaning unit and pumped through to the nozzles at high
pressure. The nozzles are programmed to perform a slow horizontal rotation
combined with a slower vertical oscillation. The directed liquid jet is used to flush
the oil sticking to the tank wall along with any dirt or residue down to the suction
point in the bottom of the tank. The washing is completed when the nozzles reach
the bottom of the tanks. The waxy asphaltic residues are easily dissolved in the
crude oil that is being used to wash the tank. Typically an inert gas system is
operated while crude oil washing is being carried out.
Marine Pollution Control/MEP1/November 2017
Fires and explosions in cargo tanks of oil tankers can have a wide variety of
causes. However it is impossible for a fire or explosion to take place in a tank that
has been rendered inert by the reduction of the oxygen level.
This reduction is achieved by delivering inert gas to the cargo tanks of crude oil
tankers to purge the air content and to maintain a slightly higher than atmospheric
pressure and so exclude air during operations.
Marine Pollution Control
In general inert gas systems are required for all tankers over 40000 tons
deadweight and all other tankers with crude oil washing systems or high capacity
tank washing machines (over 60M3 / h).
Inert gas cannot be used for pump rooms and other spaces where there is normal
access for personnel.
In general the inert gas is produced by treating the flue gases from the vessels
boilers and directing them to the vessels cargo tanks to displace the gases in the
tank atmosphere until the oxygen level falls below 8%.
Lecture Summary
You should be now able to state the statutory regulations concerning maritime
pollution, describe the procedures for handling oily bilge water and explain the
working principles and operation of oily water separators and associated
equipment capable of fulfilling discharge regulations. You should be able to
explain the working principles and operation of sewage systems. You should be
familiar with the special discharge requirements for oil and chemical tankers and
be able to explain crude oil washing and inert gas systems. You must also be able
to state the procedures for bunkering oils.