ArticlePDF Available

The impact of acid mine drainage in South Africa

Authors:
S Afr J Sci 2011; 107(5/6)
hp://www.sajs.co.za
Commentary
The impact of acid mine drainage in South Africa
Author:
Terence S. McCarthy
1
Aliaon:
1
School of Geosciences,
University of the
Witwatersrand,
Johannesburg, South Africa
Email:
Terence.Mccarthy@wits.ac.za
Postal address:
PO Box 3, WITS 2050,
Johannesburg, South Africa
How to cite this arcle:
McCarthy TS. The impact
of acid mine drainage in
South Africa. S Afr J Sci.
107(5/6), Art. #712, 7 pages.
doi:10.4102/sajs.v107i5/6.712
© 2011. The Authors.
Licensee: OpenJournals
Publishing. This work
is licensed under the
Creave Commons
Aribuon License.
Acid mine drainage (AMD) has received considerable coverage in the media of late and the number
of short courses and workshops devoted to the topic has mushroomed. The current interest was
prompted mainly by concern arising from the decanting of contaminated water from the old
gold mines in the Krugersdorp area into the Cradle of Humankind. This led to the establishment
of an interministerial committee on AMD in late 2010. As part of this initiative, a technical task
group was formed to investigate the problem and to recommend possible solutions. The report
was nalised in December 2010,
1
and focused primarily on the immediate problems arising from
gold mining and in particular on the now defunct mines in the Western Basin (Krugersdorp area),
the Central Basin (Roodepoort to Boksburg) and the Eastern Basin (Brakpan, Springs and Nigel
area). However, the problem of AMD is of far wider extent and to understand it in its entirety it
is necessary to take a much broader geographic view.
The origin of acid mine drainage
Acid mine drainage (also sometimes referred to as acid rock drainage) is a well-understood
process
2
and arises primarily when the mineral pyrite (‘fool’s gold’ or iron disulphide) comes
into contact with oxygenated water. The pyrite undergoes oxidation in a two-stage process, the
rst producing sulphuric acid and ferrous sulphate and the second orange-red ferric hydroxide
and more sulphuric acid. Pyrite is a common minor constituent in many mineral deposits and is
associated with our coal (it is the main host of sulphur in coal, the source of acid rain) and the gold
deposits of the Witwatersrand Basin. During normal weathering of these mineral deposits, acid
is produced but at a very slow rate, so slow that natural neutralisation processes readily remove
the acidity.
However, during mining and mineral extraction, the rock mass is extensively fragmented,
thereby dramatically increasing the surface area and consequently the rate of acid production.
Certain host rocks, particularly those containing large amounts of calcite or dolomite, are able to
neutralise the acid. But this is not the case for our coal and gold deposits and in these the natural
neutralising processes are overwhelmed and large quantities of acidic water are released into the
environment by mining activities, initially into the groundwater and ultimately into streams and
rivers. The acidic water increases the solubility of aluminium and heavy metals which may be
present in the affected region. The overall effect is to render the water toxic to varying degrees.
Ultimately, the water becomes neutralised by a combination of dilution and reaction with river
sediment or various minerals in soils, but certain constituents have relatively high solubilities
and remain in the water, particularly sulphate. Not all of South Africa’s mineral deposits are
aficted by acid production: diamond, iron, manganese, chrome and vanadium mines do not
generate acid-producing wastes and the majority of our platinum mines also seem to be free of
this problem.
Variables aecng the impact of acid mine drainage
The overall impact of AMD is very much dependent on local conditions and varies widely,
depending on the geomorphology, the climate and the extent and distribution of the AMD-
generating deposits. To appreciate the impact of AMD on South Africa, it is therefore necessary
to briey consider these other factors.
The river drainage network in South Africa is very asymmetrical (Figure 1). The Vaal and Orange
rivers rise almost on the eastern escarpment and ow across the entire country to discharge into
the Atlantic Ocean. The other major drainage is the Limpopo-Olifants River system, which drains
the northern portion of the country and discharges into the Indian Ocean. Most of the remaining
rivers drain the escarpment and coastal areas and have relatively small catchments. The Vaal is by
far our most important river because it supplies water to the economic heartland of the country,
not only in the Gauteng region but as far aeld as the mining districts of Welkom, Sishen and
Postmasburg. It is already over-utilised, necessitating interbasin transfers from the Tugela (via
the Tugela pumped storage scheme) and the Orange rivers (via the Lesotho Highlands scheme).
There are also some imports from below the eastern escarpment.
Page 1 of 7
S Afr J Sci 2011; 107(5/6)
hp://www.sajs.co.za
Commentary
Climate is an important variable in determining the impact
of AMD. South Africa has a very pronounced east to west
climatic gradient rainfall decreases from over 1000 mm
per annum in the east to less than 100 mm per annum in the
west, and potential evapotranspiration increases from about
1500 mm per annum in the east to 3000 mm per annum in the
west. Most of the country therefore experiences a negative
water balance (i.e. evapotranspiration > rainfall). The higher
rainfall region in the eastern and central Highveld is thus the
major source of water for the Vaal River system, with very
limited additions in the drier west.
The distribution of the coal and the major gold elds of
the Witwatersrand Basin are shown in Figure 2. A large
proportion of the coal deposits and all of the gold deposits
lie within the Vaal River catchment. The upper catchments of
the Vaal and the Olifants rivers in particular are extensively
underlain by coal deposits. This coal-rich region has the
highest rainfall in the Vaal catchment.
How mines generate acid mine
drainage
As mentioned earlier, the mining process increases the
exposure of pyrite-bearing rock to oxygenated water (derived
from rainfall), resulting in acid generation. This occurs in
different ways in gold and coal mining.
Gold mining
Witwatersrand gold occurs in layers of conglomerate rock
which form part of the approximately 7000 m thick sequence
of sedimentary rocks of the Witwatersrand Supergroup. The
layers average about a metre in thickness. The conglomerates
are not uniformly gold-bearing and only in certain
localised areas is gold present in economically recoverable
concentrations. These areas form the goldelds. Within any
individual goldeld, only a few of the conglomerate layers
have been mined.
The process of mining involves extracting the gold-bearing
conglomerate layer and transporting it to the surface where it
is crushed and the gold is extracted. Some conglomerate is left
unmined to provide support for the workers underground
and also because gold concentrations may be insufcient to
justify extraction. After extraction of the gold, the crushed
rock is deposited on waste heaps known as slimes or
tailings dumps. The conglomerates typically contain about
3% pyrite, which ends up on the dumps. Rainwater falling
on the dumps oxidises the pyrite, forming sulphuric acid
which percolates through the dump, dissolving heavy metals
(including uranium) in transit, and emerges from the base of
the dump to join the local groundwater as a pollution plume.
This polluted water ultimately emerges on surface in the
streams draining the areas around the dumps.
3,4,5,6
Streams
draining the tailings dumps are therefore typically acidic and
have high sulphate and heavy metal concentrations.
Page 2 of 7
FIGURE 1: A map showing the river basins in South Africa.
S Afr J Sci 2011; 107(5/6)
hp://www.sajs.co.za
Commentary
Page 3 of 7
Water is continually seeping into the mine workings from
surrounding groundwater and this has to be pumped out to
prevent ooding. Some of the water is used in the mining
operations and the rest is discharged into streams after basic
treatment (if necessary). Once mining operations cease,
pumping also ceases and the void created by mining slowly
lls with water. This water originates as rain and contains
dissolved oxygen. In its slow passage through the old
workings it becomes acidic and enriched in heavy metals.
Once the mine void lls completely, decant of this polluted
water commences. Decanting will occur from the lowest-
lying opening to the old workings, as is currently taking
place from the Western Basin mine void in the Krugersdorp
area.
Coal mining
South African coal occurs in layers within sedimentary rocks
of the Karoo Supergroup. These are widespread, but coal is
restricted to the areas shown in Figure 2. The coal is extracted
either by underground mining or by opencast methods.
Unlike gold mining, the coal is removed from the site and
there is very little surface dumping. Both the coal and the
host rock contain pyrite, but it is generally more abundant in
the coal layers. Underground mining results in collapse of the
overlying rock strata and when mining terminates, the voids
in the fractured rock ll with water and decanting occurs
from the lowest opening. The water is acidic as a result of its
reaction with pyrite in unmined coal and in the host rocks.
Opencast mining involves blasting and removal of the rocks
overlying the coal layer, which is removed completely.
The fragmented cover rock is then replaced (backlled)
and covered with soil and the terrain is landscaped
(‘rehabilitated’). Rainwater penetrating through the soil
into the backll becomes acidied by pyrite in the backll
material and ultimately decants on the surface. Decanting
generally commences a decade or more after mining ceases.
7
Opencast mining destroys the natural groundwater regime
and radically alters the nature of groundwater–surface water
interactions.
Past experiences of the impact of
acid mine drainage on water quality
in South Africa
Gold mining
Gold tailings dumps have been a feature of the landscape
around the large gold mining towns since mining began, and
as described above, have been discharging polluted water
for decades. The effect of this so-called diffuse pollution has
been particularly pronounced in the case of the Blesbokspruit
FIGURE 2: A map showing the distribuon of coal and Witwatersrand Basin gold deposits.
S Afr J Sci 2011; 107(5/6)
hp://www.sajs.co.za
Commentary
Page 4 of 7
in Springs and the Klip River (which drains the southern
portion of the Witwatersrand escarpment) because tailings
dumps abound in their upper catchments.
The gold mines on the Witwatersrand closed over a number
of years, and as each mine closed and ceased pumping, water
began to accumulate in the void and was then discharged
into neighbouring mines because of the high degree of
connectivity of the mine workings. The neighbours were
thus forced to shoulder the pumping responsibility. The
government introduced a pumping subsidy to assist mines
with the cost of pumping this additional quantity of water.
The water was generally of low quality, necessitating basic
treatment. This treatment consisted of adding lime to raise
the pH and blowing oxygen or air into the water to oxidise
the iron, which precipitated, taking with it most of the other
heavy metals. The iron was then allowed to settle and was
separated and disposed of on tailings dumps and the water
was discharged into local rivers. The discharged water
was clear with a neutral pH but had a very high sulphate
concentration (about 1500 mg/L).
8
These so-called point
sources further added to the pollution load already carried
by the rivers in the mining districts.
The effect of the diffuse and point source pollution arising
from gold mines of the Central and Western basins is well
illustrated by the salinity of the Vaal River, which more than
doubles between the Vaal Dam and the Barrage (Figure 3)
as a result of the inow of water from the Klip River and the
Blesbokspruit (via the Suikerbos River). The low quality of
water at the Barrage necessitates the periodic release of water
from the Vaal Dam to reduce the salinity for the downstream
Vaal River users. During wet periods, such as the current
situation, this poses no problem, but it could become critical
in a drought situation when water in the upper Vaal system,
which should be conserved for Gauteng users, has to be
released purely for dilution purposes.
When the last mine in a goldeld closed, pumping ceased
altogether and the void began to ll. The Western Basin nally
lled and began to decant in 2002. Pumping ceased in the
Central Basin in 2008 and the water level in the void is rising
at about 12 m per month currently. Pumping in the Eastern
Basin became sporadic towards the end of 2010 and nally
ceased early in 2011. The quality of the water that decants
from the mine void is extremely poor, as can be seen from
the water discharging from the Western Basin. The sulphate
concentration is typically around 3500 mg/L and the pH is
from 2 to 3. The water has high concentrations of iron and
other heavy metals. The iron oxidises on exposure to air and
precipitates along the ow path, leaving a bright orange trail
on riverbeds and banks. If there is no intervention, the Central
Basin is expected to decant in Boksburg (in about 3 years
time) and the Eastern Basin in Nigel where the lowest-lying
shafts are situated.
9
However, these decant points are based
on the assumptions that there is free-ow of water through
the mine voids and that mine shafts are the only signicant
openings to the mine void. This assumption may not be valid.
In the case of the Western Basin, water initially decanted
from a farm borehole and later from a very old mine shaft
not known to have been connected to the main void. If the
rate of ow through the void is insufcient to accommodate
the inow, multiple decant points could result.
10
Coal mining
Coal mining in the Witbank/Middelburg area commenced in
1894 to supply coal to the growing diamond and gold mining
Source: Department of Water Aairs
FIGURE 3: Variaons in the concentraon of total dissolved solids (TDS, mean and range) aecng water quality along the Vaal River system.
0
100
200
300
400
500
600
700
800
900
VS17
VS16
VS13
VS9
VS8
VS7
VS6
VS5
VS4
VS3
VS2
VS1
Monitoring Point on Vaal River(Level 1)
TDS (mg/l)
Acceptable RWQO
Vaal Dam
Grootdraai
Dam
Bloemhof
Dam
Vaal
Barrage
Douglas
Barrage
TDS (mg/L)
900
800
700
600
500
400
300
200
100
VS20 VS19 VS18 VS17 VS16 VS14 VS13 VS13 VS11 VS10 VS9 VS8 VS7 VS6 VS5 VS4 VS3 VS2 VS1
0
Monitoring point on Vaal River (Level 1)
Douglas Barrage
Bloemhof Dam
Vaal Barrage
Vaal Dam
Grootdraai Dam
S Afr J Sci 2011; 107(5/6)
hp://www.sajs.co.za
Commentary
Page 5 of 7
industries and this region therefore provides insight into the
longer-term impacts of coal mining. Many mines in the region
lie abandoned; some are on re, some have collapsed and
most are decanting acidic water. The water is entering the
local river systems (tributaries of the Olifants River) where
it is slowly neutralised by dilution and various chemical
and biological reactions. However, the water remains
highly saline and sulphate concentrations are particularly
elevated. An indication of the problem is provided by the
rising salinity and sulphate concentration of the water in
the Middelburg and Witbank dams (Figures 4 and 5). The
problem is exacerbated during dry periods and improves
somewhat during wet periods, which is the reason for the
high degree of variability in these plots, but the general
trend is one of steadily increasing salinity and sulphate
concentration. The sulphate concentration in Witbank Dam
now regularly exceeds the 200 mg/L level, which is the
recommended maximum in water for domestic use. The
quality of local water is so poor that ESCOM imports water
from the eastern escarpment for use in the power stations in
the Witbank-Middelburg area.
Ultimately, pyrite in the rocks in these mining areas will be
fully oxidised and AMD will cease. There is no indication as
to how long this will take, but the problem is likely to persist
for centuries rather than decades.
Possible future impacts of acid mine
drainage
As can be seen in Figures 4 and 5, the situation in the Olifants
River catchment continues to deteriorate. Attempts were
made to install a treatment plant in the particularly heavily
polluted Brugspruit area near Witbank, but this has been
of limited efcacy. Its main function was to address the pH
problem, and it has had no effect on the salinity of the water.
A water treatment plant (the eMalahleni Water Reclamation
Plant) based on reverse osmosis has been commissioned in
the area and has demonstrated that it is possible to treat badly
polluted water to drinking quality standards, but the cost of
the water is about three times that of water delivered to the
area from the Vaal River. Moreover, whilst this technology
can produce drinking water for communities, it cannot be
used to improve the general state of polluted rivers in the
area (the plant has a capacity of 20 mL per day, or 0.23 m
3
/s,
and cost in the region of R300 million when built in 2007). The
water quality of the Olifants River will therefore continue
to deteriorate in the foreseeable future. There is still a large
amount of unmined coal in the Olifants catchment and many
prospecting and mining applications await approval (Figure
6), which will undoubtedly lead to further increases in the
pollution loads in the future.
Although coal mining has been in progress in the upper Vaal
River catchment for some time, most of these mines are deep
and are still being actively managed. However, a disturbing
development has been the proliferation of applications for
new mining permits in the catchment (Figure 6). Should
these mines go ahead, it is almost certain that the quality of
water in the Vaal River will suffer the same fate as that in
the Olifants River, and the water in the Grootdraai Dam will,
in time, resemble that in Witbank Dam in terms of quality.
Concentraon (mg/L)
SO
4
TDS
Source: Department of Water Aairs
FIGURE 4: Concentraons of sulphates (SO
4
) and total dissolved solids (TDS) from September 1978 to July 2007 in the Middelburg Dam.
1000
900
800
700
600
500
400
300
200
100
0
Sep - 1978
Aug - 1979
Jul - 1980
Jul - 1981
Jun - 1982
May - 1983
Apr - 1984
Mar - 1985
Feb - 1986
Feb - 1987
Jan - 1988
Dec - 1988
Nov - 1989
Oct - 1990
Sep - 1991
Sep - 1992
Aug - 1993
Jul - 1994
Jun - 1995
May - 1996
Apr - 1997
Apr - 1998
Mar - 1999
Feb - 2000
Jan - 2001
Dec - 2001
Nov - 2002
Nov - 2003
Oct - 2004
Sep - 2005
Aug - 2006
Jul - 2007
S Afr J Sci 2011; 107(5/6)
hp://www.sajs.co.za
Commentary
Page 6 of 7
Concentraon (mg/L)
SO
4
TDS
Source: Department of Water Aairs
FIGURE 5: Concentraons of sulphates (SO
4
) and total dissolved solids (TDS) from January 1972 to August 2007 in the Witbank Dam.
Water from the Lesotho Highlands will then be the only
source of good quality water in the Vaal River system. The
Usutu/Pongola and Komati rivers could suffer a similar fate
(Figure 6).
The government recently announced that it has set aside
funds to deal with the looming problem of decanting of water
from the Witwatersrand gold mines. This will involve the
reestablishment of pumping and basic treatment operations
(such as the addition of lime and removal of iron) in the three
goldelds currently affected by the problem. The measures
will stop the uncontrolled decanting in the Western Basin
and prevent similar decanting from occurring in the Central
and Eastern basins. Whilst this intervention will greatly
improve the situation in the Western Basin, it will have no
impact on water quality in the Vaal River system, but will
merely return the situation to what it was when the mines
were still pumping, treating and releasing water from the
mine void.
There are many different technologies that have been
developed to desalinate polluted water from the local
mining areas. Only one of these has been implemented at
a commercial scale, namely the reverse osmosis plant at
Witbank. This plant has demonstrated that reverse osmosis
technology can address the problem, but at a high cost.
The nancial implications of other technologies have yet to
be demonstrated. It is probable that, whereas most of the
proposed technologies are suitable for treating point sources
of polluted water (e.g. pumped from old mines), it is unlikely
that they will be capable of treating polluted water arising
from diffuse sources such as waste dumps. In the case of
gold mines, the water in the void is generally accessible and
can be treated as a point source. The situation in coal mines
is more complex and it may never be possible to prevent
uncontrolled decanting of AMD from rehabilitated opencast
mines. Water quality in such areas can therefore be expected
to continue to deteriorate.
Conclusions
South Africa is well endowed with vast mineral resources
and the wealth created through mining, particularly gold
mining, has funded the development of the country.
However, as the gold mining industry enters its twilight
years we are now beginning to grasp the environmental
damage that this industry has caused and will continue to
cause in the decades to come. We have also seen the impact
that coal mining has had, particularly on water quality in
the Olifants River system. The longer-term impacts of these
industries, and especially the coal mining industry, are likely
to be far more severe in South Africa than in other countries
because of our unique combination of geography, climate,
population distribution and the scale of the deposits. We
must learn from these experiences, especially in respect of
coal mining, and carefully examine the wisdom of allowing
further coal mining in the catchments of the Vaal River and
rivers draining the eastern escarpment. New mines should
probably not be permitted in these areas until such time as an
Jan - 1972
May - 1973
Sep - 1974
Feb - 1976
Jun - 1977
Nov - 1978
Mar - 1980
Aug - 1981
Dec - 1982
Apr - 1984
Sep - 1985
Jan - 1987
Jun - 1988
Oct - 1989
Mar - 1991
Jul - 1992
Nov - 1993
Apr - 1995
Aug - 1996
Jan - 1998
May - 1999
Oct - 2000
Feb - 2002
Jun - 2003
Nov - 2004
Mar - 2006
Aug - 2007
600
500
400
300
200
100
0
S Afr J Sci 2011; 107(5/6)
hp://www.sajs.co.za
Commentary
Page 7 of 7
Source: Dr J Pretorius, Foundaon for Sustainable Environment.
FIGURE 6: A map showing the mining and prospecng areas in the upper catchments of the Vaal, Olifants, Koma and Mfolozi-Pongola-Usutu rivers in Mpumalanga.
economically viable method has been found, either to prevent
pollution or to clean up the pollution that will inevitably be
produced. As yet, none have been devised that can operate
on the scale required by our gold and coal mining industries.
Our forebears deferred the environmental costs associated
with mining, and we now have to pay those costs. Are we
going to do the same to future generations? If we do, their
problems are likely to be far more severe than ours because
the effects are cumulative and in the future, once mining is
on the wane, the funds to address the problem might not be
readily available.
This review has focused on AMD related to gold and coal
mining which is especially affecting the Vaal and Olants
River systems. These are not the only areas in the country
aficted by this malady, but because of the particular local
conditions, the problems in the Olifants and especially the
Vaal River basins are huge by comparison and pose a serious
threat to future generations of South Africans.
References
1. Expert Team of the Inter-Ministerial Committee. Mine water
management in the Witwatersrand Gold Fields with special emphasis on
acid mine drainage. Report to the Inter-Ministerial Committee on Acid
Mine Drainage. Pretoria: Department of Water Affairs; 2010.
2. Blowes DW, Ptacek CJ, Jambor JL, Weisener CG. The geochemistry of
acid mine drainage. In: Holland HD, Turekian KK, editors. Treatise on
geochemistry. Oxford: Elsevier, 2003; p. 150–204.
3. Jones GA, Brierly SE, Geldenhuis SJJ, Howard JR. Research on the
contribution of mine dumps to the pollution load in the Vaal Barrage.
WRC Report 136/1/89. Pretoria: Water Research Commission; 1989.
4. Naiker K, Cukrowska E, McCarthy TS. Acid mine drainage arising
from gold mining activity in Johannesburg, South Africa, and environs.
Environ Pollut. 2003;122:29–40.
5. Winde FLA. Uranium pollution of South African streams – An overview
of the situation in gold mining areas of the Witwatersrand. GeoJournal.
2004;61:131–149.
6. Tutu H, McCarthy TS, Cukrowska E. The chemical characteristics of
acid mine drainage with particular reference to sources, distribution and
remediation: The Witwatersrand Basin, South Africa, as a case study.
Appl Geochem. 2008;23:3666–3684.
7. Hodgson FDI, Krantz RM. Investigation into groundwater quality
deterioration in the Olifants River catchment above the Loskop Dam
with specialised investigation in the Witbank Dam sub-catchment. WRC
Report 291/1/98. Pretoria: Water Research Commission; 1998.
8. Van der Merwe W, Lea I. Towards sustainable mine water treatment
at Grootvlei Mine. Proceedings of the 8th International Congress on
Mine Water and the Environment; 2003 Oct 19–22; Johannesburg, South
Africa. Armstrong D, de Viviers AB, Klieinmann RLP, McCarthy TS,
Norton, PJ, editors. International Mine Water Association; 2003. p 25–36.
9. Scott R. Flooding of the Central and East Rand gold mines. WRC Report
486/1/95. Pretoria: Water Research Commission; 1995.
10. McCarthy TS. The decant of acid mine water in the Gauteng city-region
analysis, prognosis and solutions. Provocations Series, Gauteng City-
Region Observatory. Johannesburg: Universities of the Witwatersrand
and Johannesburg; 2010.
... Mineralogically, the Witwatersrand basin gold mine tailing dumps are mainly composed of sulphides ( McCarthy, 2011 ). It is these sulphides, particularly pyrite, that serve as the source for sulphuric acid production when reacting with water and oxygen ( Fig. 2 A). ...
... Grasslands, shrubs, small forests and ferns grow on the reddish soil along the tailing slopes. The tailings are weathered and eroded by N-W winds blowing at ca. 4 m/s and generating dust that is deposited in nearby residential settlements within 100 to 500 m away from the tailing dumps ( McCarthy, 2011 ). The study tailings are discharged by perennial tributaries flowing from the west to the east and receiving an average annual rainfall of 650 mm ( Naicker et al., 2003 ;SAWS, 2018 ). ...
... Sources of contamination include inappropriate disposal of untreated solid mining waste, weathering, and metal leaching from mine tailing dumps ( Loredo et al., 2006 ;Ahmedat et al., 2018 ;Iavazzo et al., 2012 ). The abundance of metals in the study soil is controlled by a variety of factors, such as the metal content in the original conglomerate, and the metal content in the methods used to extract the gold ( McCarthy, 2011 ;Tibane and Mamba, 2022 ). Pearson's correlation coefficient matrix was used to test the correlations between the selected metals. ...
Article
Full-text available
The Witwatersrand basin in South Africa is one of the well-known gold mining regions worldwide. Plausibly, it is one of the sites in South Africa with the highest environmental impact emanating from trace metal contamination. This study assessed the concentration of Fe, S, Cu, Mn, Cr, Zn, Ni, Co, P, Mo using inductively coupled plasma optical emission spectrometry on 21 soil samples that were collected from 9 independently located historical gold mine tailings. The results revealed high mean concentration (mg/kg) for Fe (36,433.39) > S (5,071.83) > Cu (1,717,28) > Mn (612.81) > Cr (74.52) > Zn (68.67) > Ni (40.44) > Co (9.63) > P (3.49) > Mo > (2.74) in the samples investigated. Estimated degree of contamination by using contamination indices calculations showed that the sites surveyed are on average low to moderately contaminated with Co, Cr, Cu, Mn, Ni, S, and Zn. The trace metals that are most likely to cause ecological risk incorporate Mn and Cu, especially at Durban Deep. While the health risk assessment revealed a low ecological risk (Eri) of Cr, Ni and Zn, the Eri estimates showed that the residents in the study area are prone to health risk mainly from the covetous effects of Cu (320 ≤ Eri). The residents of the study area are low income earners and the possibility that they can relocate is nonexistent. Thus, mitigation strategies are required to avoid eminent health risks and restraining housing developments near the tailing dumps.
... The oxidation of the pyrite forms sulfuric acid and then either decants from the underground cavities or percolates through the mine tailings as acid mine drainage (AMD) water. During this process the low pH water remobilizes metals, including uranium (U), ultimately translocating the dissolved metals into surface water streams and rivers [19]. As gold mines near the end of their lifetime, the removal or pumping out of groundwater is discontinued, resulting in the filling of the mining cavities. ...
... Coupled to the increased waste production and, in many cases, poorly maintained, outdated, and low-capacity tailing storage facilities, it is expected that the number of tailing dam failures will increase. Over the past 50 years there have been 63 major tailings failures worldwide [19]. In addition to the loss of life (2,375 deaths between 1961 and 2019) there has been extensive damage to the environment. ...
... Although South Africa was the biggest producer of gold globally, the industry has been experiencing several drawbacks such as mine closure of older mines and shafts, declining mineral production, exhaustion of gold reserves, global low gold prices, the high energy requirement for deep-level mining, high wage demands and social unrests as well as the generation of acid mine drainage from the mines and tailings storage facilities [1]. The cessation of the large mining operations has detrimental effects as access to gold reserves are far underground, and mining operations resorted to dewatering activities to keep the groundwater level away from the mining operations [2]. Cessation of mining further resulted in flooding of the voids, a substantial cause of groundwater and surface water contamination by acidic water [3]. ...
Chapter
Full-text available
Although mining has over the centuries improved the livelihoods and economies of many countries, the results have not spared the environment's luxurious legacy. Acid mine drainage contaminated sites with heavy metals that affect negatively and positively the macrophytes plants that grow on those sites. Accumulated elements by macrophytes planted on artificial wetlands portray the relative bioconcentration and translocation factors. Various elements were measured in the sediment, water, and macrophytes from the sampled sites and the results indicate that concentrations accumulated by plants play a significant role in biological and chemical processes in soil-water-plant relations. When comparing the drinking water quality standards by international organizations that were used as a guideline for the comparisons of elements concentration levels of elements found in water, Iron (Fe), Nickel (Ni), Manganese (Mn), and Copper (Cu) were found to be above the international water quality standards for drinking water and their average concentrations were 2230, 282, 5950, and 14,080 μg/l respectively. The sequence of elements accumulation by the macrophytes differed per plant and each of the three macrophytes plants was a hyperaccumulator of a certain element.
... The application of semi-passive biochemical reactors is a promising strategy for mitigating sulphate-rich effluents (Sánchez-Andrea et al., 2014). These systems are ideal for treatment of persistent, low volume discharge in remote locations where limited infrastructure and expertise are available (McCarthy, 2011;Pat-Espadas et al., 2018). However, the widespread application of these processes is often limited due to challenges such as reaction kinetics, sulphide management and the provision of a cost-effective carbon substrate (Harrison et al., 2014;Yang et al., 2021). ...
Article
Full-text available
Semi-passive bioremediation is a promising strategy to mitigate persistent low volume mine-impacted wastewater containing high sulphate concentrations. Building on the proof of concept demonstration of the hybrid linear flow channel reactor (LFCR), capable of simultaneous biological sulphate reduction and partial sulphide oxidation with elemental sulphur recovery, the impact of key operating parameters, such as temperature, on process performance is critical to real-world application. Temperature fluctuates seasonally and across the diurnal cycle, impacting biological sulphate reduction (BSR) and partial sulphide oxidation. The process is reliant on the metabolic activity and synergistic interactions between sulphate-reducing (SRB) and sulphide-oxidising (SOB) microbial communities that develop within discrete oxic and anoxic microenvironments within the hybrid LFCR. In this study, the impact of operating temperature on process performance was evaluated by decreasing temperature with time from 30 to 10°C in each of three laboratory-scaled hybrid LFCR units operating in pseudo-steady state at 1 g/L sulphate. Using lactate as a carbon source, two reactor sizes (2 and 8 L) were considered, while the impact of lactate vs. acetate as carbon source was evaluated in the 2 L reactors. On incremental decrease in temperature from 30 to 10°C, a decrease in volumetric sulphate reduction rate was observed: from 0.144 to 0.059 mmol/L.h in the 2 L lactate-fed reactor; from 0.128 to 0.042 mmol/L.h in the 8 L lactate-fed reactor; and from 0.127 to 0.010 mmol/L.h in the 2 L acetate-fed reactor. Similarly, sulphate conversion efficiency decreased (2 L lactate-fed: 66% to 27%; 8 L lactate-fed: 61% to 20%; 2 L acetate-fed: 61% to 5%). A decrease in temperature below the critical value (15°C) led to considerable loss in metabolic activity and overall BSR performance. Sessile and planktonic microbial communities were represented by bacterial phyla including Proteobacteria, Synergistetes, Bacteroidetes, and Firmicutes. A diverse group of putative SRB (Deltaproteobacteria) and SOB, including Alpha, Beta, Gamma, and Epsilonproteobacteria phylotypes, were prevalent and shifted in relative abundance and community composition in response to decreasing temperature. Specifically, the decrease in the relative abundance of Deltaproteobacteria with decreasing temperature below 15°C corresponded with a loss of BSR performance across all three reactors. This study demonstrated the impact of low temperature on the physiological selection and ecological differentiation of SRB and SOB communities within the hybrid LFCR and its implications for real-world process performance.
... In South Africa, the threat of AMD to the water systems has reached acute levels in recent years [27][28][29] . Both operational and abandoned coal mines generate AMD in South Africa 30 . ...
Article
Full-text available
The study reported on here was conducted to assess the impacts of historic coal mining activities at Elitheni Colliery in South Africa. Five boreholes and five water ponds were sampled during the summer of 2010 and winter of 2011. Physical characteristics (pH, EC, TDS) and hydrochemical characteristics (Na + , K + , Ca 2+ , Mg 2+ , HCO3-, Cl-, SO4 2-, F-, Pb and Fe) of the water were determined. To assess the suitability of the water for irrigation purposes, parameters such as total hardness, sodium absorption ratio (SAR), percentage sodium (% Na), residual sodium carbonate (RSC), permeability index (PI) and Mg ratio were calculated. The pH of the water ranged from 6.87 to 8.91, and electrical conductivity (EC) was between 4.5 and 94 mS/m. Total dissolved solids (TDS) ranged from 178 to 470 mg/L; spatial variations in TDS attest to variations in lithological composition, activities and prevailing hydrological regimes. HCO3-and SO4 2-were the dominant anions, while Na + was the dominant cation. Na-K-SO4 and Na-HCO3 were the dominant hydrochemical facies. Fe content was high in borehole water due to the oxidation of pyrite. On the basis of the calculated SAR, % Na, RSC, Mg ratio and salt content, it was concluded that the water can be used for irrigation purposes. The water quality analysis provided no conclusive evidence that historical mining activities have had any significant impact on the acidification of water resources in Elitheni Colliery. However, further studies are required to ascertain the ability of the aquatic environment and surrounding rocks to buffer any acid generated.
... 1,2 Consequently, the huge amount of waste from mining activities adversely affects ecosystems, including human health. 3,4 Minerals are extracted from both open-pit and underground mine configurations across the life of the mine, inevitably leading to the generation of acid mine drainage (AMD), a toxic waste effluent. AMD is generated by the spontaneous oxidation of FeS 2 when exposed to air and water. ...
Article
Full-text available
Intensive mining activities generate toxic acid mine drainage (AMD) effluents containing a high concentration of metals, including iron. The chemical synthesis of iron nanoparticles from this waste could lead to further environmental concerns. Therefore, the green synthesis of nanoparticles using plants has gained significant interest because of several benefits, including being eco-friendly. The current study reports a novel approach involving the synthesis of stabilized iron nanoparticles from AMD using rooibos tea extract. An aqueous solution of rooibos tea was prepared and titrated with AMD to reduce Fe2+/Fe3+. The samples synthesized under optimum conditions were characterized by TEM, XRD, FTIR, UV-Vis, and EDS. The results revealed that the nanoparticles had an average particle size of 36 nm with a spherical shape. These particles showed promising application as a Fenton-like catalyst for the degradation of textile dye (orange II sodium salt) with a removal efficiency of 94% within 30 min. Thus, the stabilized iron nanoparticles synthesized here performed in higher ranges than the currently reported Fenton-like catalysts regarding dye removal efficiency and reaction time.
... Limited studies have been conducted to understand SV strategies (Anglo American, 2021;Cooper & Harvey, 2018;Nicholson, 2017) and how South African mining organisations could navigate the environment in which they operate to create value for all stakeholders. Previous studies in the South African mining industry include a study on the impact of acid mine drainage (McCarthy, 2011), prospects and challenges for small-scale mining entrepreneurs (Mkubukeli & Tengeh, 2016), black economic empowerment in the industry (Fauconnier & Mathur-Helm, 2008), tough choices facing the industry (Lane et al., 2015) and sustainability (Zvarivadza, 2018). Similarly, one of the SV pioneering studies in South Africa focused on assessing SV created in tourism (Nicholson, 2017). ...
Article
Full-text available
Purpose: The study investigated the perceptions of Shared Value (SV) and its antecedents and outcomes within the mining industry in South Africa. Design/methodology/approach: After conducting a literature overview of the South African mining industry and theories linked to SV, a hypothesised model of the study was developed. This study used a quantitative research methodology. An explanatory hypothesis-generating approach was employed through an empirical investigation using the survey method. The survey items were self-developed based on hypothesised variables. The study’s respondents were identified via non-probability sampling, namely convenience and snowball sampling. A total of 340 respondents participated in the study. Results/Findings: The empirical results confirmed that automation and employment conditions are the antecedents of SV in the mining industry. The study illustrated three approaches of SV: reconceiving the products or services and markets, reimagining value chain productivity and development of the enabling environment. Furthermore, the study revealed competitive advantage and sustainability performance as the outcomes of SV in the mining industry in South Africa. Practical implications: The study contributes by making practical recommendations to the mining industry role players on how to increase SV and improving competitiveness and sustainability performance whilst increasing economic prosperity by resolving social and environmental issues that are of mutual interest to stakeholders. Originality/value: The study fills a knowledge gap on SV in South Africa because of limited national mining studies. Furthermore, as SV is a novel and significant advancement in management sciences, the study is a valuable resource for SV decision-making across industries.
Chapter
Although mining has over the centuries improved the livelihoods and economies of many countries, the results have not spared the environment’s luxurious legacy. Acid mine drainage contaminated sites with heavy metals that affect negatively and positively the macrophytes plants that grow on those sites. Accumulated elements by macrophytes planted on artificial wetlands portray the relative bioconcentration and translocation factors. Various elements were measured in the sediment, water, and macrophytes from the sampled sites and the results indicate that concentrations accumulated by plants play a significant role in biological and chemical processes in soil-water-plant relations. When comparing the drinking water quality standards by international organizations that were used as a guideline for the comparisons of elements concentration levels of elements found in water, Iron (Fe), Nickel (Ni), Manganese (Mn), and Copper (Cu) were found to be above the international water quality standards for drinking water and their average concentrations were 2230, 282, 5950, and 14,080 μg/l respectively. The sequence of elements accumulation by the macrophytes differed per plant and each of the three macrophytes plants was a hyperaccumulator of a certain element.
Article
The lack of access to safe drinking water has been a global crisis for the longest time, which has encouraged researchers to improve existing technologies or create new strategies to address issues associated with water pollution from both inorganic and organic pollutants. Adsorption and photodegradation are among the simple, cost-effective and environmentally durable methods applied in wastewater treatment. The chemistry and applications attapulgite clays receive ongoing attention in removal of contaminants from water due to their fascinating unique remarkable adsorption properties as well as their economic appeal, attapulgite clays have been extensively studied for the adsorption of various contaminants in aqueous media. In this study, the removal of sulphate ions from Acid Mine Drainage (AMD) using modified attapulgite by electrolyte (BaCl2) and two surfactants viz., hexadecyltrimethylammonium bromide (HDTMA), and trimethyldecylammonium bromide (TDTMA) was investigated. The study is the first to investigate and compare all three modified attapulgite by electrolyte (BaCl2) and two surfactants viz., hexadecyltrimethylammonium bromide (HDTMA), and trimethyldecylammonium bromide (TDTMA) and the factors that affecting removal of sulphate from AMD. A scanning electron microscope (SEM), X-ray diffraction (XRD) patterns, and a Fourier Transform Infrared (FTIR) spectrometer were used to analyse and validate the modified attapulgite clays. Batch adsorption studies were then carried out using the modified attapulgite clays, and the influence of various parameters influencing sulphate ion recovery, such as contact time, temperature, and solids loading, was investigated. At 25°C, sulphate ion removal rates of 75% were obtained using BaCl2-modified attapulgite at a solid loading of 10% (m/v).TDTMA and HDTMA-modified attapulgites followed, with ion recovery of 69 and 16 %, respectively, at a solid loading of 200% (m/v). These results suggest that BaCl2 was the most effective ionic surfactant when used to modify attapulgite clay for sulphate ion removal, and was therefore chosen for downstream studies. When the reaction temperature was increased to 35°C and 45°C to investigate the influence of temperature, it was discovered that the removals of sulphate ions were reduced to 66 and 64%, respectively. These results demonstrated that increasing the temperature has a negative impact on the removal of sulphate ions. The Temkin adsorption isotherm and the second-order kinetic model were found to have a very significant correlation with the results, implying that they best describe the experimental data. The activation energy of 23.7 kJ/mol clearly showed that chemisorption was the primary sulphate removal method. The results of this investigation demonstrated that BaCl2-modified attapulgite clay was a good adsorbent for the efficient adsorption of sulphate ions from AMD.
Article
Understanding the fundamental controls that govern the generation of mine drainage is essential for waste management strategies. Combining the isotopic composition of water (H and O) and dissolved sulfate (S and O) with hydrogeochemical measurements of surface and groundwater, microbial analysis, composition of sediments and precipitates, and geochemical modeling results in this study we discussed the processes that control mine water chemistry and identified the potential source(s) and possible mechanisms governing sulfate formation and transformation around a South African colliery. Compared to various South African water standards, water samples collected from the surroundings of a coal waste disposal facility had elevated Fe²⁺ (0.9 to 56.9 mg L⁻¹), Ca (33.0 to 527.0 mg L⁻¹), Mg (6.2 to 457.0 mg L⁻¹), Mn (0.1 to 8.6 mg L⁻¹) and SO4 (19.7 to 3440.8 mg L⁻¹) and circumneutral pH. The pH conditions are mainly controlled by the release of H⁺ from pyrite oxidation and the subsequent dissolution of carbonates and aluminosilicate minerals. The phases predicted to precipitate by equilibrium calculation were green rusts, ferrihydrite, gypsum, ±epsomite. Low concentrations of deleterious metals in solution are due to their low abundance in the local host rocks, and their attenuation through adsorption onto secondary Fe precipitates and co-precipitation at the elevated pH values. The δ³⁴S values of sulfate are enriched (−6.5 ‰ to +5.6 ‰) compared to that of pyrite sampled from the mine (mean −22.5 ‰) and overlap with that of the organic sulfur of coal from the region (−2.5 to +4.9 ‰). The presence of both sulfur reducing and oxidizing bacteria were detected in the collected sediment samples. Combined, the data are consistent with the dissolved sulfate in the sampled waters from the colliery being derived primarily from pyrite probably with the subordinate contribution of organic sulfur, followed by its partial removal through precipitation and microbially-induced reduction.
Article
Full-text available
During more than a century of gold mining in South Africa large amounts of tailings were produced, which now cover vast areas in densely populated regions. These dumps contain elevated levels of uranium and other toxic heavy metals associated with gold in the mined ore. Large-scale extraction of uranium from auriferous ore only took place during the cold war, leaving tailings with high uranium concentrations that were deposited before and after this period. Recent studies found elevated levels of the radioactive heavy metal in groundwater and streams, mainly attributed to the discharge of contaminated water from mines. In this paper the contribution of seepage from slimes dams to the uranium pollution of adjacent streams is analysed. Based on geochemical analyses of samples, field observations and long-term in situ measurements of hydraulic and hydrochemical parameters at selected mining sites across the Witwatersrand goldfields, the extent, mechanisms and dynamics of diffuse stream contamination by tailings seepage is characterised. Temporal and spatial variations of the process and the associated hazard potential are discussed.
Article
Full-text available
Water quality in the immediate vicinity of mine tailings in and around Johannesburg, South Africa was investigated. Pollution is derived primarily from Au mine tailings dumps that are disused or are undergoing retreatment to extract remaining Au, and is dispersed by way of groundwater plumes. These discharge into perennial streams in the area. Pollution manifests itself in the form of low pH (>2) and high concentrations (exceeding 7,000 mg L−1 in some cases). Water quality improves away from the tailings area. Pollution loads were found to be higher at the end of the rainy season, due to a rise in the water table and hence increased groundwater seepage. Polluted groundwater usually has low Eh (300 mV) and pH (2–3), and high EC (up to 8 mS cm−1 in some instances). Oxidation of Fe occurs as the groundwater emerges on surface, further lowering pH, and establishing an Fe(III)-Fe(OH)3 redox equilibrium, which operates for many kilometres downstream. Various processes that occur increase compositional heterogeneity in the water, amongst which are evaporation, dissolution of efflorescent crusts and dilution by unpolluted water. Wetland environments are characterised by high pH and low Eh, and appear to be influenced by a sulfide–sulfate redox system, under which and metals are removed, and pH increased. Lakes in the mining area have normal water quality, which arises from a combination of metal removal by wetlands (most lakes have wetlands at their inlets) and dilution by rain and unpolluted groundwater. They offer a potential method for passively treating polluted water arising from tailings dumps.
Article
Full-text available
The Witwatersrand region of South Africa is famous for its gold production and a major conurbation, centred on Johannesburg, has developed as a result of mining activity. A study was undertaken of surface and ground water in a drainage system in this area. Soils were also analysed from a site within the mining district. This study revealed that the ground water within the mining district is heavily contaminated and acidified as a result of oxidation of pyrite (FeS2) contained within mine tailings dumps, and has elevated concentrations of heavy metals. Where the water table is close to surface, the upper 20 cm of soil profiles are severely contaminated by heavy metals due to capillary rise and evaporation of the ground water. The polluted ground water is discharging into streams in the area and contributes up to 20% of stream discharge, causing a lowering of pH of the stream water. Much of the metal load is precipitated in the stream: Fe and Mn precipitate as a consequence of oxidation, while other heavy metals are being removed by co-precipitation. The oxidation of iron has created a redox buffer which controls the pH of the stream water. The rate of oxidation and of dilution is slow and the deleterious effect of the addition of contaminated water persists for more than 10 km beyond the source.
Article
Mine wastes are the largest volume of materials handled in the world (ICOLD, 1996). The generation of acidic drainage and the release of water containing high concentrations of dissolved metals from these wastes is an environmental problem of international scale. Acidic drainage is caused by the oxidation of sulfide minerals exposed to atmospheric oxygen. Although acid drainage is commonly associated with the extraction and processing of sulfide-bearing metalliferous ore deposits and sulfide-rich coal, acidic drainage can occur wherever sulfide minerals are excavated and exposed to atmospheric oxygen. Engineering projects, including road construction, airport development, and foundation excavation are examples of civil projects that have resulted in the generation of acidic drainage. On United States Forest Service Lands there are (2-5)×104 mines releasing acidic drainage (USDA, 1993). Kleinmann et al. (1991) estimated that more than 6,400 km of rivers and streams in the eastern United States have been adversely affected by mine-drainage water. About (0.8-1.6)×104 km of streams have been affected by metal mining in the western United States. The annual worldwide production of mine wastes exceeded 4.5 Gt in 1982 (ICOLD, 1996). Estimated costs for remediating mine wastes internationally total in the tens of billions of dollars ( Feasby et al.,1991).
Flooding of the Central and East Rand gold mines
  • R Scott
Scott R. Flooding of the Central and East Rand gold mines. WRC Report 486/1/95. Pretoria: Water Research Commission; 1995.
The decant of acid mine water in the Gauteng city-region-analysis, prognosis and solutions. Provocations Series, Gauteng CityRegion Observatory
  • T S Mccarthy
McCarthy TS. The decant of acid mine water in the Gauteng city-region-analysis, prognosis and solutions. Provocations Series, Gauteng CityRegion Observatory. Johannesburg: Universities of the Witwatersrand and Johannesburg; 2010.
Research on the contribution of mine dumps to the pollution load in the Vaal Barrage
  • G A Jones
  • S E Brierly
  • Sjj Geldenhuis
  • J R Howard
Jones GA, Brierly SE, Geldenhuis SJJ, Howard JR. Research on the contribution of mine dumps to the pollution load in the Vaal Barrage. WRC Report 136/1/89. Pretoria: Water Research Commission; 1989.
Mine water management in the Witwatersrand Gold Fields with special emphasis on acid mine drainage Report to the Inter-Ministerial Committee on Acid Mine Drainage. Pretoria: Department of Water Affairs The geochemistry of acid mine drainage
  • Cj Ptacek
  • Jl Jambor
  • Cg Weisener
1. Expert Team of the Inter-Ministerial Committee. Mine water management in the Witwatersrand Gold Fields with special emphasis on acid mine drainage. Report to the Inter-Ministerial Committee on Acid Mine Drainage. Pretoria: Department of Water Affairs; 2010. 2. Blowes DW, Ptacek CJ, Jambor JL, Weisener CG. The geochemistry of acid mine drainage. In: Holland HD, Turekian KK, editors. Treatise on geochemistry. Oxford: Elsevier, 2003; p. 150–204.
Investigation into groundwater quality deterioration in the Olifants River catchment above the Loskop Dam with specialised investigation in the Witbank Dam sub-catchment Pretoria: Water Research Commission; 1998. 8. Van der Merwe W, Lea I. Towards sustainable mine water treatment at Grootvlei Mine
  • Fdi Hodgson
  • Rm Krantz
Hodgson FDI, Krantz RM. Investigation into groundwater quality deterioration in the Olifants River catchment above the Loskop Dam with specialised investigation in the Witbank Dam sub-catchment. WRC Report 291/1/98. Pretoria: Water Research Commission; 1998. 8. Van der Merwe W, Lea I. Towards sustainable mine water treatment at Grootvlei Mine. Proceedings of the 8th International Congress on Mine Water and the Environment; 2003 Oct 19–22; Johannesburg, South Africa. Armstrong D, de Viviers AB, Klieinmann RLP, McCarthy TS, Norton, PJ, editors. International Mine Water Association; 2003. p 25–36.
Investigation into groundwater quality deterioration in the Olifants River catchment above the Loskop Dam with specialised investigation in the Witbank Dam sub-catchment
  • Fdi Hodgson
  • R M Krantz
Hodgson FDI, Krantz RM. Investigation into groundwater quality deterioration in the Olifants River catchment above the Loskop Dam with specialised investigation in the Witbank Dam sub-catchment. WRC Report 291/1/98. Pretoria: Water Research Commission; 1998.