Transcript OILY SLUDGE DISPOSAL OPTIONS

OILY SLUDGE DISPOSAL
IN THE CONTEXT OF THE
MARINE POLLUTION AGREEMENT
INTRODUCTION
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MARPOL – (Marine Pollution Agreement)
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International convention signed by 137 countries
around the world, including the UAE in October 2006
Introduced to reduce, and reduce the risk of, pollution
at sea from shipping
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To prevent the disposal of wastes at sea
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Requires Port Authorities to control waste disposal by ensuring
all vessels have Certificates of Safe Disposal for all waste
streams, namely solids, sewage and oily waste before leaving
port
 In particular the disposal of oily slops and sludges
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SOURCE
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The sources of oily effluents generated by
shipping are mainly from:
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Impurities removed from bunker fuel oil
Tank cleanings (bunker and cargo)
Oily effluent water
Lubricants and greases
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CHARACTERISATION
These streams can be characterised into two groups
as follows:
Slops:
Sludge:
Pumpable
Solids < 1,5% m/m
Water 30% - 60% v/v
Specific Gravity <1
Un-pumpable
Solids > 35% m/m
Water 10% - 20%
Specific Gravity >1
The importance of this distinction is in the
handling, processing and disposal costs.
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RECOVERY
The method of recovery of these waste streams varies
significantly:
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SLOPS:
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Pumped overboard
Either into a barge or a
road tanker on the wharf
side
The quantity of oil
generated is typically 0,5%
of vessel’s fuel used
The typical recoverable oil
in slops is >95%
The cost per tonne of oil
recovered is relatively low
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SLUDGE:
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Shoveled by hand into
small plastic bags
Placed in skips
Removed overboard by
crane
The quantity is much less
than slops and dependent
on the period between tank
cleanings
The typical recoverable oil
in sludge is <66%
The cost per tonne of oil
recovered is relatively high
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DISPOSAL
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The principles of disposal should always
be to:
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MAXIMISE the UTILISATION of the energy
source through recovery and recycling
MINIMISE the quantity of waste requiring
DISPOSAL with regard to:
Environmental considerations/circumstances
 Best Available Practical Technology (BAPT)
 Facilities and infrastructure
 Cost
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UTILISATION
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SLOPS:
Has a high usable oil content, and recovery and
dewatering can be practically and economically carried
out. The recovered oil can be either:
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Returned to BUNKER FUEL OIL by blending
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Currently no practical technology available to render slops into
bunker fuel oil specification
However as most refineries produce bunker fuel that is well within
the quality specification, judicious blending is possible, although this
is not necessarily to the liking of ship owners and engineers
INDUSTRIAL FUEL OIL
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Requires a different and often lower quality specification
Can be practically achieved with current technology
Requires a local industrial base using heating fuel
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UTILISATION
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SLUDGE:
The sludge can be utilised as is, in:
Cement manufacture (Fe & Al content beneficial)
 Clay brick manufacture (replaces coal)
 And not much else!
However some useful oil can generally be recovered
from the sludge. This has the advantage of reducing
the volume of waste and renders the sludge more
acceptable for disposal
But at considerable cost
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DISPOSAL
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SLOPS:
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SOLIDS (sludge):
 The removal of the inorganic solids from slops produces a
sludge as there is usually some associated oil remaining.
 This sludge can be less than 60% oil by mass
 And would typically account for less than 5% by mass of the
oil in the slops received.
WATER:
 The water can be
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Easily removed to below 1% remaining in the oil
Pre-treated to remove the bulk of the oil (<200 ppm)
Disposed to a biological water treatment facility
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DISPOSAL
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SLUDGE:
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The removal of the free oil in sludge results in
a sludge requiring disposal with around 50% oil
content by mass and accounts for around 40%
by mass of the sludge received.
Further processing can reduce the oil content
even further but at a cost
There are various available technologies:
Centrifugation, solvent wash, steam stripping
 Incineration, pyrolisation or thermal desorption
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DISPOSAL
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The choice of approved disposal options
needs to consider:
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The ENVIRONMENTAL IMPACT of each
alternative in respect of the:
Available practical technology
 Type and quantity of pollution produced
 The local circumstances
 The acceptable cost-benefit ratio
 Sustainability
 Monitoring and control required
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PROCESS
SLOPS
PROCESSING
WATER
TREATMENT
WATER
DISPOSAL
OIL PRODUCT
SLUDGE
SLUDGE
PROCESSING
SLOPS
SLUDGE
TREATMENT
SOLIDS
DISPOSAL
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SYSTEM REQUIREMENTS
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Policy (port authority) detailing requirements, standards, procedures,
system, authorisations, measurement, monitoring etc
Vessel disposal control system
Infrastructure:
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Processing facilities
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Slops
Sludge
Effluent oily water
Disposal Facilities
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Barges and/or road tankers
Wharf side tankage for slops/ballast water
Sludge handling (skips and trucks)
Landfill for sludge/solids/plastic
Bio-treatment for effluent water
Compliance monitoring
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LOW SPEED
HORIZONTAL
SPINDLE
CENTRIFUGE
HIGH SPEED
VERTICAL
SPINDLE
CENTRIFUGE
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FORCED FEED
EVAPORATOR
FOR WATER
REMOVAL
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