The Disposal of Liquid and
Solid Effluents from Oil Refineries
MICHAEL BENGER
British Petroleum Company, Ltd.
London, England
INTRODUCTION
Public authorities in all parts of the world where oil refineries are installed or
projected have become acutely aware of the danger of loss of amenity resulting
from the presence of the refinery. Many countries have recently introduced new
legislation to control discharges and all are continuously reviewing measures to
make the controls more stringent. In a paper presented to an international conference it is not appropriate to describe the regulations imposed by any one country
in detail; all are framed with the same intentions. This paper is largely confined
to conditions as they exist in the United Kingdom and Western Europe.
Required standards of liquid effluent quality naturally vary according to the
locality and circumstances of the discharge and are usually decided by the appropriate local authority. It would evidently he unfair to expect a refinery discharging
into an already dirty harbor or estuary to conform to the same standard as one discharging close to an established bathing beach or into an unpolluted river stocked
with fish. The self-purifying character of the water should also normally be taken
into account. A new refinery will be required to achieve higher standards than
one that has been operating over a number of years, although the latter will be
under continuous pressure for improvements. When a new refinery is being designed
it is necessary to hold consultations at an early stage with the appropriate authorities to agree to the maximum tolerable limits of various possible contaminants.
Disposal facilities for solid wastes, although a relatively minor problem must also
be discussed with local authorities.
TYPES OF AQUEOUS EFFLUENTS
The most important waste from a refinery, requiring purification, is oily
water, although especially in older refineries there may be chemical wastes as
well. Aqueous effluents may be classified as follows: 1) Surface water including
rainwater; 2) Process water; 3) Cooling water; 4) Tanker ballast.
Rainwater falling on a refinery can be divided into two categories, one from
oil-free areas and the other from places that may be oily. Clean areas include
car parks, roadways, administrative buildings etc., and here no special purification
is necessary. Dirty areas are process units, tank bunds, pipe tracks, laboratory
drains, etc. Cooling water for pump glands also frequently passes to surface drains.
This must be purified, by methods to be described later, before being discharged.
Process water is all water that has been in direct contact with oil. This includes
crude oil desalter water, to be referred to again later, water wash stages from
various refining processes, and also condensate deriving from steam injection to
distillation columns or ejectors of vacuum towers. All this must also be purified
before being discharged.
Refinery cooling water may be once through or recirculated through cooling
towers.    In either case large quantities are required.   The volume will depend on
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