Environmental Engineering Reference
In-Depth Information
the steam-assisted in situ processes and/or the fracking process for treatment at their
respective surface treatment facilities, not all the contaminated water is recovered. It is
the nonrecovered (fugitive) water that constitutes the source of stressors to the immedi-
ate geoenvironment.
5.4 Tailings Discharges
Central to the extraction of resource material contained in the ores obtained in mining
is ine grinding of the ores—as the preliminary stage of the beneiciation process. The
common elements of the various techniques used in the beneiciation processes include
both ine grinding and washing-lotation and inally, at some stage in the beneiciation
process, separation of the resources from the inely ground material. Flotation and other
methods of resource separation (e.g., magnetic) are required. The end result of all of these
processes is the generation of liquid wastes containing a suspension of the inely ground
material. This liquid waste is generally deined as tailings waste slurry or slurry tailings . It
can be well appreciated that the generous quantities of tailings are relective of the sig-
niicant amounts of water needed in the processing of the inely ground ore material for
beneiciation.
5.4.1 Containment of Tailings
Slurries, slimes, sludges, and red-mud ponds are all names that are given to the general
class of slurry tailings discharged from beneiciation processes—the choice of which
depends on the nature of the tailings being discharged. These slurry tailings cannot be
directly discharged into the land environment not only because (a) they contain suspended
ines and (b) their chemical nature will most likely be toxic to the environment and public
health. In short, discharge of these kinds of tailings will have detrimental impact on the
land ecosystem. Some of the main reasons for containment of these slurry tailings are
• To avoid pollution of the land surface environment . This is one of the principal rea-
sons for containment, and is generally coupled with other speciic disposal-
containment strategies.
• To provide permanent containment of the tailings . This strategy generally includes sev-
eral kinds of scenarios, ranging from permanent ponds to totally reclaimed solid
land surfaces, e.g., a multistage strategy for treatment of tailings pond sludges as a
land reclamation process (Yong, 1983a, b).
• To recover water for reuse in the beneiciation processes as process recycle water or other
mine-site requirements . This requires implementation of treatment of the superna-
tant—assuming that liquid-solids separation is effective in producing sedimenta-
tion of the suspended ines in the slurry tailings.
• To permit secondary recovery from the storage pond . This strategy presumes that some
residual resource is contained in the slurry tailings waste, and that secondary
recovery of this resource can be obtained when appropriate technology becomes
available, and when the economic climate is favorable.
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