Environmental Aspects of Phosphate and Potash Mining United ...

The Environmental Approach of the Phosphate Rock and Potash Mining Industry
Surface Disposal of Potash Waste
In Saskatchewan, Canada the salt tailings, insolubles
and brines are typically disposed of to a salt tailings
pile as a slurry. The insolubles and brine drain to the
settling ponds at the base of the pile.The brine is then
either recirculated to the process or disposed of
through deep well re-injection to suitable geological
formations.
In Germany, dry separation processes allow dry disposal
on a salt tailings pile. The salt tails are stacked
using a conveyor and spreader system that allows
steeper, higher stacking than wet stacking.
Industry research in Canada is currently focusing on
higher salt tailings piles that allow more waste to be
accommodated within the same footprint. This has
been driven by regulations on the expansion of waste
disposal facilities.This technique also reduces surfaceto-volume
ratio, and fewer brines are produced by
precipitation.
In many cases, engineered surface containment methods
such as stacks (or piles), dams and ponds are used
to contain liquid and solid wastes. This involves an
integrated system comprising engineered impoundments,
walls, containment dykes, liners, drains, ditches
and capture wells. These confine any adverse environmental
effects of the waste to a limited area, while
providing a high degree of management control.
Stacking may reduce the area of land disturbed.
Backfilling of waste into underground openings produced
during extraction of the ore is conducted at a
few operations. When feasible, this provides a safe and
secure long-term disposal method.
The technical feasibility of backfilling flat-lying orebodies
has been studied through large scale trials.
However, its wider adoption has been hindered by a
number of factors including the difficulty of placement,
safety concerns, and the cost.
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Salt tailings pile - Potash Corporation of Saskatchewan
(PCS), Canada
Currently, the cost of backfilling flat-lying orebodies
may be a factor of 10 higher than surface disposal
methods.
Safety concerns arise from the placement of unconsolidated
waste into underground workings that
experience rapid convergence. If not restrained by a
bulkhead of suitable strength it will be squeezed into
the adjacent open workings, endangering the workforce.
Alternatives such as converting the salt tailings
to paste fill are being explored.
Deep well injection is used to dispose of brines at
operations where suitable, confined permeable geological
strata are available.
Converting waste to an environmentally benign form
reduces the difficulty and cost of disposal. In certain
instances, there is also potential for creating a saleable
by-product.
Dry salt tailings pile - Kali und Salz GmbH, Germany