Page 19 - Environmental Control in Petroleum Engineering

8 Environmental Control in Petroleum Engineering

In most cases, the cost of eliminating all risks and hazards associ-
ated with wastes is economically prohibitive. Prudent management
practices focus available resources on the activities that pose the
greatest risk to both the economic health of the company and the
environment. The risks associated with various waste management
practices can be quantified and ranked through risk assessment studies
(Sullivan, 1991). When properly managed, the risks and hazards of
drilling and production operations can be reduced to low levels.

1.1.5 Waste Treatment Methods

Most wastes require some type of treatment before they can be
disposed of. Waste treatment may include reducing the waste's total
volume, lessening its toxicity, and/or altering its ability to migrate
away from its disposal site. A variety of treatment methods are
available for different types of wastes, although their costs vary
significantly. The waste treatment method selected, however, must
comply with all regulations, regardless of their cost.
One of the most important steps in waste treatment is to segregate
or separate the wastes into their constituents, e.g., solid, aqueous, and
hydrocarbon wastes. This isolates the most toxic component of the
waste stream in a smaller volume and allows the less toxic components
to be disposed of in less costly ways. Primary separation occurs with
properly selected and operated equipment, e.g., shale shakers, separa-
tion tanks, and heater treaters. Separation can be improved by using
hydrocyclones, filter presses, gas flotation systems, or decanting
centrifuges (Wojtanowicz et al., 1987). In arid areas, evaporation
and/or percolation can be used to dewater some wastes.
A number of methods are available for treating hydrocarbon-
contaminated solids like drill cuttings, produced solids, or soil. Solids
can be washed by agitation in a jet of high-velocity water, perhaps
with an added surfactant. Solids can also be mixed with an oil-wet
material such as coal or activated carbon, that absorbs the hydrocar-
bons and can be separated from the more dense solids by subsequent
flotation. An emerging and promising technology for hydrocarbon
removal from contaminated solids is bioremediation. Other treatment
methods include distillation, solvent extraction, incineration, and
critical/supercritical fluid extraction.