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Wastewater treatment and water recycling
Transcript of Wastewater treatment and water recycling
IN MINING AND
MINERAL EXTRACTION PROCESSES
Water and solution recycling in the Canadian mineral industry
Methods for treatment of recycle water
The aim of the thesis
Contents of the thesis
for water use in mineral extraction processes
used and the
formed in the processing of ore and minerals
technologies for different mineral industry wastewaters
behind the processes
motives for recycling
of process waters
best available techniques
considering mining activities
in mining and mineral extraction processes
School of Chemical Technology
Degree Programme of Materials Science and Engineering
A literature survey
To consider the
in reasonable and efficient water usage and high water recycling rate in mining and mineral processing industry.
collect background information
for the future projects and development of wastewater management technologies and water recycling in mining and mineral extraction processes.
Water intensities of key minerals and metals
Effects of using
in sulfide and non-sulfide flotation
Rao and Finch, 1989.
Rao and Finch, 1989.
The motives for the
recycling of water
Both economic and environmental reasons
Mineral processing plants may use a large proportion of the local water resources
Reduced availability of water for others
Shortage of water
in hot arid or semi-arid areas
On the other hand, too much water in e.g. Scandinavia
production and transportation
of fresh water are usually expensive
Recycling can lead to
in water, energy and reagent consumption
, such as heavy metals, metal ions and residual reagents in the flotation wastewater are one more reason to aim for
directly re-using the water in the process instead of transporting it to the disposal area
As mineral production continues to be necessary for economic development, the
recycling and re-use
of mining and mineral-processing wastes need to be developed now and in the future.
Water is getting more expensive to gain and recover. At the moment,
pricing of water
is distorted as governments want water to be as cheap as possible.
The pricing should prevent misuse.
Purifying recycled process waters only to a suitable level
concerning the process
(not to a level needed when water is discharged back to the environment) could lead to
The amount of make-up water is thus also decreased.
What has been done and noticed:
No problems in
gravity and magnetic concentration
circuits is well developed.
The most serious problems are in
circuits using selective flotation.
cyanide gold industry
, recycling is limited due to the build-up of complex chemical compounds and a high concentration of sulfates.
plants using acid leaching, recycling is not practiced because of the impurities and incompatibility with the process. In carbonate leach plants, alkaline leach solutions are recycled.
Mine water is recycled in the grinding-thickening circuit.
Joe, 1984; Joe and Pickett, 1974; Ritcey, 1989.
recycling in different mills
(alkaline earth and heavy metal ions)
on active carbon or coal (organics)
on mineral slimes (metal ions, some organics)
on bentonite clay (metal ions, amines)
at liguid-gas interface (surface-active organics)
, IX (ionic species)
Dissolved air flotation
(ions, ultrafine particles, precipitates, micro-organisms, oils, proteins)
Reverse osmosis, RO (electrolytes: dissolved salts, organics, colloidal solids)
by e.g. ozone (organics)
(electro-lytes and organics)
(In brackets: what is removed)
Hoag and Albern, 1977