Encyclopedia of Environmental Science and Engineering, Volume I and II

802

OIL SPILLAGE INTO WATER—TREATMENT

The general subject of treatment of oil spillage represents

a relatively new area of technology that is unique in that it

encompasses chemical, mechanical, and biological disciplines.

There are three major aspects to the problem of oil spills.

1) PREVENTION OF THE SPILL;

2) CONTAINMENT AND RECOVERY OF THE

SPILL;

3) TREATMENT OF THE SURFACE OIL.

Although this discussion is mainly directed toward the treat-

ment of the spilled oil, the related areas will also be considered

in order to put the overall subject in the correct perspective.

PREVENTION OF THE SPILL

The Prevention of Oil Spillages is the Primary

Consideration

It should be emphasized that prevention is the fi rst consid-

eration and, of course, the most complete solution. In the

industrial and governmental communities, the major effort

has been directed toward this area. There is extensive ongo-

ing research for example, ranging from operational areas

such as collision avoidance techniques and training to more

novel approaches such as the gellation of crude oil. In this

latter approach several chemical systems have been devel-

oped to gel the oil cargo. This in-situ solidifi cation thereby

prevents the release of oil from a damaged cargo compart-

ment that may be in danger of failure.

Details of this gellation system can be found in US Patent

3,634,050.^1 Other details, such as the effects of mixing, crude oil

type, chemical concentration, and so on, on the strength of the

gel have been outlined by Corino.^2 Gellation is a novel approach

to prevent the release of oil. However the fact that there have

been no commercial uses of this method since its conception

twenty fi ve years ago raises questions regarding its practicality.

Finally, the removal of the oil cargo from a grounded

tanker is another area where the threat of the release of a fl uid

and mobile oil cargo to the marine environment has been miti-

gated by advances in salvage techniques. The offl oading of

the grounded SS General Colocotronis on a reef off Eleuthera

Island in March–April 1969 and the well documented recov-

ery of Bunker C oil from the sunken tanker SS Arrow in

Chedabucto Bay, Nova Scotia during the winter of 1970^3 are

two outstanding examples of this prevention technique.

This latter incident represented a singular achievement

in light of the weather conditions encountered during early

March in Nova Scotia. Over 6000 tons of viscous Bunker C

oil were recovered from the sunken wreck. The salvage team

used a hot tap technique to penetrate the tanker cargo tanks

and then used a steam traced pumping system to transfer the

oil to a barge at the surface.

A more recent and massive removal of oil was the EXXON

VALDEZ in March 1989 after its grounding on a reef in Prince

William Sound. Although approx 250,000 Bbls of North

Slope Crude oil was spilled from the grounded vessel, 80 per-

cent of its cargo was still in the tanker. This offl oading was a

signifi cant marine engineering feat since care must be taken to

offl oad such a large vessel in the correct sequence since other-

wise hull stresses could cause the vessel to break up.

CONTAINMENT, RECOVERY OR REMOVAL OF THE

SPILLED OIL

If a spill has occurred, it is universally agreed that the rec-

ommended procedure is to contain and physically recover

it with or without the use of adsorbents. It is obviously the

most direct solution to spill incident, if conditions permit its

execution. This approach may entail three processes:

1) Confinement of the spill by spill booms.

2) Recovery of the spill by sorbing agents. In this

area, more recent advancements have been solidi-

fying agents (Solidifiers).

3) Physical removal of the contained oil by oil pickup

devices.

4) Controlled burning of spilled oil.

These aspects of the recovery approach are interrelated as

will be appreciated by the following discussion.

Confi nement of the Spill by Spill Booms There are many

oil spill booms commercially available today. Unfortunately

they are signifi cantly limited by the velocity of the surface

current and wave height. Although there are variations in

the materials of construction, strength, geometry, etc., of

these various boom designs, as evidenced by the number

available and the range of costs, their general forms are

quite similar. Almost any type of fl oating barrier will hold

back and contain some amount of oil under quiescent

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