Dissertation FINAL

UNIVERSITY OF PORTSMOUTH
Acid Mine Drainage; An
Overview
and a Comparison of
Mitigation Strategies

ii
Abstract
Exploiting the Earth’s natural resources has been a remorseless pursuit since early times. Although
mining is no longer a vital industry in the UK economy, the legacy of Britain’s industrial past still
remains, in the form of pollution emanating from abandoned mines. Over time, this has called for real
investment into technologies to mitigate the environmental impacts of discharging mines. Unlike in
history, a robust environmental monitoring scheme is now built into the initial mine development plan,
with strict monitoring initiating from the green field site to years after closure.
Prevention of AMD synthesising and inhibiting its migration from its source is considered to be the
most desirable option, although this often isn’t practical in many sites. In such cases it is essential to
collect, treat, and discharge the mine water back into the environment. Various options for remediating
AMD, are divided into those that use either chemical or biological mechanisms to neutralise AMD and
remove metals from solution. In the case of Wheal Jane,a high density sludge (HDS) treatment is
preferential, could with the introduction of lime slurry to increase pH and precipitate out any heavy
metal contaminants.
This evaluation describes the current abiotic and biotic remediating strategies that are currently
utilised to alleviate AMD. Comparisons on the strengths and weaknesses of each are assessed, with
new and emerging technologies described. The factors that currently effect the application of a
treatment system are discussed.
Keywords
Acid, Mine, Drainage, Mitigation, Passive, Active, Wheal Jane

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Contents
List of Figures.............................................................................................................................. v
List of Tables ............................................................................................................................... v
List of Plates................................................................................................................................ v
1. Introduction ...................................................................................................................... 1
2. Aims and objectives .......................................................................................................... 2
3. Methodology..................................................................................................................... 3
4. Acid Mine Drainage: A definition & nature of the problem .................................................. 5
5. The Chemistry and Occurrence of Acid Mine Drainage ....................................................... 7
5.1 The Sulphur Cycle............................................................................................................. 8
5.2 The Iron cycle..................................................................................................................10
5.3 AMD Equation 1..............................................................................................................11
5.4 AMD Equation 2..............................................................................................................11
5.5 AMD equation 3...............................................................................................................11
5.6 AMD equation 4...............................................................................................................12
6. Legislation and policy.......................................................................................................14
6.1 Government Acts: Examples .............................................................................................14
7. Mitigation of Acid Mine Drainage.....................................................................................17
7.1 Point source control vs. migration control ..........................................................................18
7.1.1 Point source control..........................................................................................................19
7.1.2 Migration control .............................................................................................................19
7.2 Bioremediation.................................................................................................................20
7.2.1 Passive bioremediation .....................................................................................................20
7.2.2 Active bioremediation ......................................................................................................21
7.3 Case Study; CL:AIRE Wheal Jane Tin Mine ......................................................................22
7.3.1 Pilot passive treatment......................................................................................................23
7.3.2 Active treatment...............................................................................................................24
8. Discussion .......................................................................................................................28

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8.1 Iron .................................................................................................................................30
8.1.1 Toxicity...........................................................................................................................30
8.1.2 Iron Bioremediation..........................................................................................................30
8.2 Toxicity of Other Heavy Metals and Metalloids .................................................................30
8.2.1 Cadmium.........................................................................................................................30
8.2.2 Lead................................................................................................................................32
8.2.3 Arsenic............................................................................................................................33
8.3 Treatment........................................................................................................................33
9. Conclusions .....................................................................................................................34
10. References.......................................................................................................................35

v
List of Figures
Figure 1 Sources and pathways of mine pollution (Younger et al. 2002)............................................ 7
Figure 2 The Sulphur cycle (O'Neill, 1993) ..................................................................................... 8
Figure 3 Eh-pH diagram for Fe Compounds Garrels, R.M., 1965) .................................................. 10
Figure 4 Various ways that have been assessed to prevent AMD (Johnson & Hallberg, 2005) .......... 18
Figure 5 Schematic of the RAPS systems (Younger et al., 2003) .................................................... 20
Figure 6 Catchment area of the Wheal Jane Tin Mine (Environment Agency, 2007) ........................ 22
Figure 7 The pilot passive scheme at Wheal Jane (Claire, 2004) ..................................................... 24
Figure 8 Outline of the active treatment plant at Wheal Jane (Brown et al., 2002) ............................ 25
Figure 9 Soil cap to dried out sediments from leaching back into the environment (Johnson &
Hallberg, 2005) ........................................................................................................................... 25
Figure 10 Aerial view of the Wheal Jane active treatment plant (Environment Agency, 2007) .......... 26
Figure 11 A chart displaying the effects of AMD on the biosphere (Gray, 1997).............................. 28
Figure 12 Graphical representation of the percentage (%) decrease of the heavy metal concentration
one treated in the active treatment (based upon table 3).................................................................. 29
List of Tables
Table 1 Environmental Quality Standards (Mestre, 2009)............................................................... 15
Table 2 Average Composition of effluent water from Wheal Jane 1995-98 (Claire, 2004) ................ 23
Table 3 Simplified table of actual Wheal Jane data (Fowler, M., 2015, pers. Comms., 24 April) ....... 26
Table 4 Discharge limits of the Wheal Jane mine as set by the Environment Agency (Wheal Jane staff
2015, pers. Comms., 24 April)...................................................................................................... 27
Table 5 Threshold toxicity values of cadmium (Cd) (Health Protection Agency, 2011) .................... 31
Table 6 Threshold toxicity values of lead (Pb) (Health Protection Agency, 2007) ............................ 32
Table 7 Threshold toxicity values of Arsenic (As) (Health Protection Agency, 2011)....................... 33
List of Plates
Plate 1 The Wheal Jane Tailing Dam with Wheal Jane Mine in the background (Environment Agency,
2007)…………………………………………………………………………………………………....6
Plate 2 Photograph showing the red-orange precipitate (Ochre) from a stream receiving Acid Mine
Drainage (Stoker, C., 2003, NASA, retrieved from
http://www.nasa.gov/centers/ames/news/releases/2003/03images/tinto/tinto.html)..............................11

vi
Acknowledgments
I would like to extend my gratitude to Dr Mike Fowler for guiding me throughout this dissertation,
dealing with my frequent stressed out states and seemingly endless e-mailing, often asking stupid
questions. But most of all for the knowledge past down throughout my 3 years at the University of
Portsmouth.
To the entire SEES faculty I have being in contact with, in the three years I have attended the
University of Portsmouth, for giving the best guidance and education on offer.
I also extend gratitude to my granddad, Mr William “Bill” Moore, who worked in the coal fields of
Yorkshire throughout his life, and inspired me to begin research into acid mine drainage.
A constant source of belief, inspiration and support throughout my life.
To mum and dad for always pushing me to strive for the best and for not letting me quit when I
consider giving up
A special mention to my aunt Cheryl, for her English skills aiding in the proof read and grammar
checks of this dissertation.

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1. Introduction
Abandoned mines from Britain’s past are a legacy causing a significant pollution problem in many
waterways around Britain. This is an ongoing threat as historical mines are currently leaching acidic
mine waters in surrounding waterways and more recently closed mines are filling with flooding
groundwater and precipitation, and in turn will discharge contaminated mine water (Johnston, et al.,
2008). Mining waste is difficult to deal with due to the fact that it leaves a lasting impression on the
environment. Younger and Adams (1999) state that even thirteenth century mine workings in Scotland
still discharge acidic and iron rich waters into the River Esk. This pollution is collectively called acid
mine drainage (AMD).
Acid mine drainage (AMD) is a particular type of pollution that arises from the oxidation of sulphide
containing minerals, namely those containing Iron Pyrite (FeS2). This occurs naturally when sulphide
containing rocks begin to oxidise and are then subjected to moisture during weathering processes
(Jennings, et al., 2008). AMD occurs both naturally and also due to anthropogenic activities, and, as
the name suggests, the majority of Acid Mine Drainage occurs due to mining. However,AMD can
further be caused by other land disturbances, such as that of construction (Jennings, et al., 2008),
increasing the surface area of FeS2 exposed to the oxidising agents. Acid mine waters further decrease
the quality of water bodies, by dissolving metals into them. This increased influx of metals into
freshwater bodies causes serious environmental implications (Jennings, et al., 2008).

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2. Aims and objectives
This dissertation shall give an overview and definition of Acid Mine Drainage (AMD) in a scientific
yet concise way so that the reader understands not just what it is, but how it arises in the natural world
and the subsequent environmental implications that occur due to high concentrations of pollutants
discharging. It also aims to describe the processes and chemistry that initiate Acid Mine Drainage with
a simplistic breakdown of the chemical processes.
A summary of the Water Framework Directive 2000/60/EC (WFD) and various relevant
legislation, shall be analysed so that the reader shall be able see how certain laws control the way
discharging mine water is to be tackled and to compare current legislation to what is been done to
mitigate such pollution.
The bulk of study shall be delving into mitigation techniques, giving a comparison and exploring
whether current techniques can deal with the increasing levels of discharging pollution. Conclusion
shall be drawn as to whether passive or active treatments are working to mitigate mine drainage
pollution, and which as a whole performs better in the realenvironment. Discussion shall lead on to
whether passive/active mine water treatments are economical and sustainable. Further evaluations
shall arise to compare what other large mining nations are doing to combat this particular type of
pollution and discuss whether what other nations do can be utilised in our own environment.

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3. Methodology
The methodological approach to the research of acid mine drainage arose in the form of a literature
review of several books, scientific reports and papers. Early guidance from Dr Mike Fowler led me to
start research with the help of “Abandoned mines and the waterenvironment, Science project
SC030136-41” which details the strategic approach of the Environment Agency, Scottish Environment
Protection Agency (SEPA) and Coal Authority to reduce the impact of the significant mine pollution
problem in England, Scotland and Wales. Below is a summary of this project published by the
Environment agency in collaboration with Scottish Environment Protection Agency (SEPA) and The
Coal Authority.
Abandoned mines and the water environment, Science project SC030136 -41
Many mines throughout Britain have been abandoned and now discharge mine water containing a
substantial concentration of heavy metals and other pollutants into kilometres of watercourses. More
recently closed mines are beginning to fill up with groundwater and infiltrating precipitation and will
start discharging in the immediate future. As a consequence,nine percent of rivers in England and
Wales and two percent in Scotland are at risk of failing to meet their Water Framework Directive (The
European Union Water Framework Directive (2000/60/EC)) targets of good chemical and ecological
status. These failing rivers carry some of the largest discharges of metals such as cadmium, iron,
copper and zinc into the seas around Great Britain, which is further supported by evidence that
seventy-two percent of failures to achieve the cadmium quality standard in freshwater are located in
mined areas. The legal position in the United Kingdom means that no-one can be held liable for the
pollution from the majority of mines. It is only since 1999 (Pollution Prevention and Control Act
1999) that the operator of a mine has had any obligation to deal with the consequences of
abandonment.
Fifty four mine water treatment plants have been implemented, which inhibit 2,500 tonnes of iron
and other metals from entering our rivers per annum, protecting over 200 km of rivers and aquifers.
The majority of plants are maintained and operated by the Coal Authority, to highlight the worst
discharges from abandoned mines and detect forthcoming problems. The largest mine water treatment
plant in Britain has been implemented to deal with pollution from the Wheal Jane tin mine, Cornwall
(which shall be studied further in section 7).
Sustainable technology for treating coal mine water discharges is well developed, but is not
directly applicable to most metal mine discharges, due to location, the sheer volume of discharge or
both. It is important to mention the need to develop more passive treatment methods which do not
depend on costly equipment or considerable raw materials and power, as to act in an environmentally
sustainable manner. Further work is needed in many areas,including:

4
 New technologies and methods to regain energy and other resources from mine water and
residues;
 The development of remedial methods.
 Monitoring of mine water flow and quality;
 Understanding the influences of past discharges on sediment quality and ecosystem health;
(Environment Agency (2008), Abandoned mines and the water environment,Science project
SC030136-41, Bristol)
Throughout the early proposal stage, between the end of April 2014 and September 2014, an initial
review of the literature that had been sourced through “ScienceDirect” and other scientific reports sites
was conducted. During this process, basic knowledge of Acid Mine Drainage and how it is synthesised
through several chemical processes was acquired.
From September 2014 onwards, a further literature review occurred to examine the various mitigation
techniques that are implemented around the globe. It was discovered that mine drainage remediation is
split into two categories; active and passive, one requiring energy and resources and the latter
requiring none or very little energy and resources.
Further research led to the discovery of several scientific reports and papers that detailed the existence
of severalspecies of bacteria that can, and do, initiate acid mine drainage through the natural oxidation
of sulphur-containing minerals. This also led to the discovery of species of bacteria that can “reverse”
the process of mine drainage by reducing the sulphate and initiate heavy metal precipitation.

5
4. Acid Mine Drainage:A definition & nature of the problem
Sulphur-rich wastewaters are the by-products of a variety of industrial operations such as galvanic
processing and the scrubbing of flue gases at power plants (Johnson, 2002), yet the chief, worldwide
culprit is the seepage of contaminated effluent resulting from the flooding of abandoned mine
workings. The term acid mine drainage (AMD) is used to describe low pH, polluted waters emanating
from abandoned mine workings that often contain great concentrations of toxic heavy metals.
AMD typically forms in underground workings of deep mines, although this is generally regarded
as of negligible importance when a mine is in active day-to-day production. Rising water tables, due to
infiltrating precipitation and flooding aquifers, are kept artificially low through mechanical pumping
(Johnson & Hallberg, 2005). However,when mines are decommissioned and abandoned, and the
pumps are turned off, the abrupt flooding of the water table can lead to contaminated groundwater
being discharged, sometimes to the extremes, such as at the Wheal Jane mine in 1992. (Younger et al.,
2003) (Nealet al., 2004).
The pollution is caused by the exposure of sulphide ores to atmospheric oxygen, thus initiating the
process of oxidation. This process is elevated by increasing the surface area of sulphide containing
minerals to be readily exposed to atmospheric oxygen and moisture (Jennings, et al., 2008). Such
flood waters,draining from active and, more so, abandoned mines and wastes,such as tailing ponds
and slag heaps, are often have net acidity (Johnson & Hallberg, 2005). Increased concentration of the
waste in the tailings, can mean drainage that discharges from these area may be more aggressive than
that which discharges from the mine itself (Plate1) (Johnson & Hallberg, 2005). Acid generation
resulting from the exposure of sulphide bearing minerals often surpasses the buffering capabilities of
surrounding rock and water resources,due to the excess of accessible hydrogen ions within solution
(Jennings, et al., 2008).

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Plate 1 The Wheal Jane Tailing Dam with Wheal Jane Mine in the background (Environment Agency, 2007)
Acidic mine effluent often poses a serious, additional risk to the environment by containing
substantial concentrations of metallic elements, dissolved into solution by the net acidity of
contaminated seepage waters. The metals present are iron, aluminium and manganese. It has been
stated by Johnson & Hallberg (2005), that an estimated 19,300 km of streams and rivers, and 72,000
ha of lakes and reservoirs around the globe have been seriously impaired by effluents originating from
decommissioned mines (Johnson & Hallberg, 2005).
Clarke (1995), states that the initial effluent waters of a decommissioned mine are typically more
polluting than subsequent discharges due to the acidic salts that reside in rock pores of the mine.
It is vital to understand that not all effluent water from mining activities are acidic: alkaline mine
exists. It is often stated that alkaline mine drainage does not have as much of an environmental impact
as its acidic counterpart (Akcil & Koldas, 2006). Alkaline mine drainage may occur due to many
factors which include: a low sulphide content of surrounding rock; limited oxidation of pyrite due to
an decreased surface area; neutralisation of the acid by carbonate minerals, engineering factors (which
include cement or rock flour from demolition and construction); infiltrating naturally highly alkaline
groundwaters, flooding influent water not making effective interaction with the sulphide containing
minerals (Banks et al., 2002). In some areas,the limestone geology buffers the AMD to near-neutral
conditions, causing the metals to precipitate. Many alkaline waters display an increased concentration
of ferrous iron, which, upon oxidation and hydrolysis radically lowers the pH, causing the effluent to
be acidic.

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5. The Chemistry and Occurrence ofAcid Mine Drainage
Acid mine drainage is caused by a sequence of chemical reactions. During operation of a typical mine,
an artificially dry environment begins the process of oxidation as iron pyrite is exposed to oxygen.
Flood waters subsequently cease the oxidation process, but dissolve the exposed metal ions and
sulphates synthesising sulphuric acid (Environment Agency, 2008). However,the now acidic mine
water will naturally dissolve any metallic compounds present causing high concentrations of metals,
predominantly iron, zinc, copper, lead, cadmium, manganese and aluminium (Environment Agency,
2008). When the rising, acidic water finally breaches the surface it may dissepate out via old
workings, springs, seepage through the ground or even through the bed of a river (Environment
Agency, 2008). Figure 1 below shows these potential sources and passageways of pollution associated
with minewater.
When polluted waters first emerge,they often display a clear appearance. This is cheifly because
underground water is particulary low in oxygen and metals are dissolved. Once the water begins to
aerate in the host waterbody, iron hastily oxidises and is identified as an orange deposit of “ochre” as
shown in plate 1 (Environment Agency, 2008). It is possible that in some deeper mines, levels of
polluted water may never reach the surface but may well flow into underground aquifers, which may
have significant impacts upon water intended for human consumption (Environment Agency, 2008).
Figure 1 Sources and pathways of mine pollution (Younger et al. 2002)
The prediction of surface emergences of polluted mine waters is rather problematic as there are
many contributing factors. It is possible for predictions to be wrong; for example, Blaenant colliery

8
closed in South Wales and it was predicted that pollution would discharge from the main shaft at the
mine site. However,the discharge managed to make its way out through much older mine-workings at
Ynysarwed. (Environment Agency, 2008). Underground blockages or roof falls can also inhibit
discharges or change path. (Environment Agency, 2008). Furthermore, minewater chemistry is also
rather difficult to predict to due having many factors controlling them. It is possible for these factors to
differ within the same mine depending on whether they arise from shallow seams or from deeper
levels. Very large interconnected collieries, with severalseams that are worked at various depths, may
lead to the possibility of large uncertainties in predicting the quality of the mine water (Environment
Agency, 2008).
5.1 The Sulphur Cycle
= x109
kg S
Figure 2 The Sulphur cycle (O'Neill, 1993)
The occurrence of iron pyrite starts within the sediments on the sea bottom, with the abundance of
sulphur reducing micro-organisms, which allow the formation of Hydrogen sulphide (H2S) (O'Neill,
1993). The hydrogen sulphide produced reacts with metals within the sediments, iron being the chief
metal due to its large quantities in marine sediments as iron (III) hydroxide (Fe(OH)3),and produces
the sulphide mineral Trolite (FeS). Trolite reacts further with dissolved sulphur to produce iron pyrite.
2Fe(OH)3 + 3H2S  2FeS + S + 6H2O
FeS + S  FeS2
As pyrites are often associated with coal, once they exposed to the atmosphere due to either uplift,
mining or weathering, oxidation leads to the synthesis of sulphuric acid (H2SO4) (O’Neill, 1993).

9
2FeS2 + 2H2O + 7O2  2FeSO4 + 2H2SO4

10
5.2 The Iron cycle
The changes in oxidation state of the iron in the crust are be important in understanding its mobility.
The unstableness of iron (II) and iron (III) is so great, that even small changes in the environment can
cause iron (II) to be oxidised to iron (III), or iron (III) to be reduced into iron (II) with significant
changes in solubility of the element (O'Neill, 1993).
Figure 3 Eh-pH diagram for Fe Compounds Garrels, R.M., 1965)
As seen in figure 3, it is easily observable to see the possible conditions in soil. The Fe2+
species (FeS2
included) reside in acidic conditions (O’Neill, 1993). Because the boundary is just acidic, relatively
small changes in Eh or pH can cause precipitation or the dissolution of the iron ions (O’Neill, 1993).
This can be witnessed when polluted waters emerge from spring, when the Eh exponentially increases
due to the dissolution of oxygen and a red-brown precipitate of iron (III).
The reason behind why so many metals are dissolved in waters suffering from acid mine drainage is
due to the high surface area of the precipitate and as such, many other metals are attracted towards the
slightly negative dipole of the oxygen (O’Neill, 1993).

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5.3 AMD Equation 1
The reaction between O2, H2O and Iron pyrite produces ferrous sulphate and sulphuric acid in a
solution. Equation 1 shows this below (Jennings, S.R.,et al., 2008).
2FeS2 (S) + 7O2 + 2H2O  2Fe+2
+ 4SO4
-2
+ 4H+
(Akcil & Koldas, 2006)
This redox oxidation occurs swiftly in the presence of water and O2, more so in the company of
microorganisms. Nordstrom, et al., 1997 states that the ferrous iron produced in this initial reaction,
can be oxidised further to give additional acidity, through sulphur oxidising bacteria.
5.4 AMD Equation 2
Once sufficient oxygen has been dissolved into the mine water,oxidation of ferrous iron (Fe+2
) to
ferric iron (Fe+3
) occurs. Exposure of mine water to atmospheric oxygen can also be the causation of
the chemical reaction below.
2Fe+2
+ ½ O2 + 2H+
 2Fe+3
+ H2O
Equation 2 is a key chemical point in Acid Mine Drainage, as two pathways can be taken to further
increase the pollution in the globes waterways.
5.5 AMD equation 3
Pathway one allows Ferric iron (Fe(OH)3) to precipitate out of solution, giving waterways the
distinctive red-orange hue as shown below in Plate 2 (Jennings, S.R., et al., 2008).

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Plate 2 Photograph showing the red-orange precipitate (Ochre) from a stream receiving Acid Mine Drainage (Stoker, C.,
2003, NASA, retrieved from http://www.nasa.gov/centers/ames/news/releases/2003/03images/tinto/tinto.html)
The equation for production of this ochre stain is as stated below;
2Fe+3
+ 6H2O  2Fe(OH)3 (S) + 6H+
As shown above this reaction this produces 6 moles of Hydrogen ions increasing the acidity of the
mine waters further.
5.6 AMD equation 4
Pathway two comes about from the ferric iron reacting directly with exposed pyrite, which further
increases the acidity of the mine waters. From the equation below, it is possible to see why so many
rivers that have mine waters flowing into them fail Water framework Directive due to having such low
pH levels (Jennings, S.R., et al., 2008).
14Fe+3
+ FeS2 (S) + 8H2O  2SO4
-2
+ 15Fe+2
+ 16H+
As shown above its possible to see why there is dramatic decrease in pH when Fe(OH)3 reacts with
pyrite due to the excess of SO4
-2
ions and the synthesis of 16 moles of hydrogen ions, allowing the
synthesis of sulphuric acid (Jennings, et al., 2008).
It is important to state that if sufficient oxygen is dissolved alongside the ferrous iron produced in
equation 4, the reaction of equation 2 & 3 are perpetuated (Younger et al., 2002). Contrastingly,
without the excess of dissolved oxygen, mine water shall only show elevated levels of ferrous iron as
the reaction in equation 4 terminate at completion (Younger et al., 2002).

13
Upon the oxidation of a sulphide or sulphide containing mineral, subsequent acidic products can either
be immediately swept away by water moving over the rock or, in the case of no water movement, can
amass in pores in the rock, where it shall be discharged later (Akcil & Koldas, 2006).
Akcil & Koldas 2006, state that the primary factors that affect the rate of which acid mine
drainage is generated are;
 pH;
 Temperature;
 Oxygen concentration in the water phase;
 Degree of saturation with water;
 Chemical activity of Fe3+
;
 Surface area of exposed metal sulphide;
 Bacterial activity
Akcil & Koldas 2006, go on to explain that the factors stated above are important for calculating the
rate of acid generation. Physical factors, are particularly important, principally a mine that has a high
waste rock dump permeability, a dump with a high permeability naturally has high oxygen ingress,
which contributes to higher chemical reaction rates,which in turn leads to higher temperatures and
increased oxygen ingress through the process of convection.
Bacterial activity can have an impact upon the generation of acid mine drainage. One such bacterium
is Acidithiobacillus ferrooxidans,and is involved in the oxidation of pyrite (FeS2) (Akcil & Koldas,
2006). Environmental conditions must be favourable, for bacteria to thrive and grow. A. ferrooxidans,
for example, is more suited to thrive in water with a pH of less than 3.2 (Akcil & Koldas, 2006). If
conditions are not favourable for the bacteria,the influence on acid generation will reside at a
minimum.

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6. Legislationand policy
Legislation that governs the way the mining industry acts, has expanded over recent years. Legislation
is often implemented following a disaster, which has led to a need for specific laws to control
operations or eliminate risks of certain operations within mine workings. Until recently, legislation
was chiefly concerned with the working environment of the pit and little concern towards the
environmental consequences of mining (Bgs.ac.uk,n.d.). Consequently, there were few regulations
governing the environment beyond the actual mine site (Bgs.ac.uk,n.d.). Thus any discharges that
occurred from mine tailings, the owner could not be held accountable. The early examples of
legislation were intended to provide a safer working environment for miners with an introduction of
regulations concerning the control of ventilation to inhibit gas explosions. As mining grew into an
industry and thrived, further legislation was introduced to include of working mine plans, mine
abandonment plans and the creation of a Mine Inspectorate to enforce the regulations and ensure these
provisions were in place throughout the working environment (Bgs.ac.uk,n.d.).
6.1 Government Acts: Examples
The EU Water Framework Directive (WFD)
The Water Framework Directive 2000/60/EC (WFD) is legislation delivered from the European Union
(EU) that became part of the law in December 2000. The directive pursues the protection of all waters
from all of the European Union member states (Mestre,2009). The Water Framework Directive sets
out two initial objectives which are:
 Prevention of degradation of all surface and groundwater bodies
 Protect,enhance and restore all surface water and groundwater bodies, with the aim of
attaining good surface water status and good groundwater status by the year 2015
The Water Framework Directive states that Environmental Quality Standards (EQS) are required for
many polluting substances. These EQS are used as thresholds which, if exceeded,will have adverse
effects upon flora and fauna around a body of water (UKTAG,2008). A selection of EQS are
summarised below in Table 1.

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Table 1 Environmental Quality Standards (Mestre, 2009)
Substance EQS (ppm)
Nitrate 17.5
Sulphate 87.5
Phosphate 0.04-0.1
Zinc 0.12
Iron 1
Manganese 0.0175
Cadmium 0.001
Copper 0.001
Lead 0.004
Chromium 0.005
Nickel 0.05
pH 6-9
In the United Kingdom, work is currently being undertaken by the Environmental Agency (EA) in
partnership with the Scottish Environment Protection Agency (SEPA),to identify the major causes of
the many failures to meet a good ecological statuses in surface and groundwater bodies, as described
by the WFD, which includes diffuse pollution from quarrying and mining (EA, 2008) (SEPA,2009). It
is to be understood that eight of the twelve River Basin Districts in the UK identify mine pollution as a
significant problem. This has subsequently resulted in 9% of rivers in England and Wales and 2% in
Scotland being at risk of failing to meet good ecological status, as set by the European Union
(Johnston and Rolley, 2008). In order to tackle coal mine pollution problems in accordance with the
WFD in the UK,The Coal Authority (CA) has developed a mitigation plan of corrective and
preventive measures, which in its current state consists of forty six treatment systems cleaning and
protecting up to 200km of rivers (Johnston and Rolley, 2008). Mestre,2009 states that there are future
remediation schemes planned to be constructed within the next three planning cycles established by
the Water Framework Directive, high (by 2015), medium (by 2021) and low (by 2027) (Mestre, 2009).

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Mining Waste Directive (MWD) (2006/21/EC)
The Mining Waste Directive (MWD) (2006/21/EC) introduces methods to prevent or significantly
minimise the environmental impacts and adverse effects to human health which are caused through the
extraction of the Earths mineral resources via the process of mining (Directive 2006/21/EC).
The key provisions of this piece of legislation means there are controls the physical aspect of the tips
and failure to maintain good stability may impact on human health or the water,air, soil, fauna and
flora aspects of the biota. It further describes the need for control measure to inhibit the seepage from
abandoned mines by controlling surface and groundwater mixing with contaminated waste (Directive
2006/21/EC).
This European Directive, means that mine owners are responsible to put control measure in place to
avoid detrimental effects towards the environment, therefore this is a means of mitigation of acid mine
drainage. EU 2006/21/EC puts in place enforceable laws to control seepage of contaminated effluent
into the environment.

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7. Mitigation of Acid Mine Drainage
Hundreds of mines worldwide have been forced to stop production due to a variety of economic and/or
environmental factors. Naturally, the groundwater table has been allowed to rise, and in the majority
of countries in the developed world proves a rather substantial environmental problem (Wolkersdorfer,
2002). Historically, it has been noted that treatment of polluted effluent is a rather costly venture, thus
forcing mine owners/operators into finding more efficient and sustainable, therefore less expensive,
methods of control the hydrology of abandoned mines as to inhibit the amount of pollution discharge
into watercourse around the globe (Wolkersdorfer, 2002). With the aim to have an “in-place” passive
treatment after a mine flood (Younger, 2000).
Initial tracer tests are required,to find the flow pathway of seepage water between the mine cavern and
surface (Wolkersdorfer, 2002). The aim of tracer tests is to assess the hydrodynamic conditions whilst
locating networks between mine and surface and making assumptions on the increase or decrease of
contaminants (Wolkersdorfer, 2002), therefore can be used in monitoring an abandoned mine, which,
in turn, can be used to aid mitigation of further mine seepages and be used as a means of education for
future mines, with the possible outcome of being a future prerequisite of acquiring permission to
reclaim land, previously utilised as mine workings. There are severaltracers in use, and the more
favourable tracer is selected on the results obtained from laboratory testing, cost of the tracer material
and the cost of analysis to be undertaken (Wolkersdorfer, 2002).
The success and feasibility of water treatment is exceedingly variable depending upon the treatments
employed, which are often grouped into two types: passive and active. The site characteristics also
play a vital role in whether a treatment scheme is to be a success or failure. Passive water treatment
systems are typically used in a wetland environment largely operated without an input of chemicals
and mechanised support (Jennings, et al., 2008). On the other hand, the active-style of water treatment
systems are characteristically highly engineered projects, commonly employing chemical clean-up of
acid mine water to achieve a water quality standard specified in the Water Framework Directive
(Mestre,2009). Active treatment systems are operational in large open mines and are often utilised to
deal with large volumes of polluted effluent. (Jennings et al., 2008).
Akcil & Koldas (2006) state that currently, acidified mine drainage is often treated with the addition of
lime (CaOH) to neutralise the acid and precipitate the heavy metals out as hydroxides. These,when
allowed to coagulate, form a high density sludge (HDS),which once settled can give a relatively clear
overflow, and then discharged into rivers (the HDS process) (Akcil & Koldas, 2006).
Two developments utilised in South Africa may prove to be a notable opportunity. The first is a
widely utilised process, which is a well-known method used to de-ionise solutions. This uses cation
and anion exchange resins to absorb cations and anions (SO4
2-
) by replacing them with hydrogen (H+
)
and hydroxide ions (OH-
) (Akcil & Koldas, 2006). When the pollutants fill the resin, they have to be

18
restored with an acid and an alkali (Akcil & Koldas, 2006). After the calcium sulphate precipitate is
removed, it can be sold as a fertiliser which is similar to the industrial product which, is synthesised
between these same acids and alkalis (Akcil & Koldas, 2006). This in turn means that the regeneration
of the resins has a net zero cost, plus reduces environmental impact as the by-products can be recycled
and utilised rather than regarded as waste. The second stage of the development was the increase in
agricultural practices at Western Areas Gold Mine (Akcil & Koldas, 2006) which uses treated mine
drainage with additives of fertiliser, with the aim to produce crops. This activity is still operating
successfully on waste land surrounding the mine (Akcil & Koldas, 2006).
7.1 Point source controlvs. migration control
Techniques that prevent Acid mine drainage rather than “cure” it, are collectively known as source
control. Figure 4 below displays various ways that have been assessed to prevent Acid mine drainage.
Figure 4 Various ways that have been assessed to prevent AMD (Johnson & Hallberg, 2005)
As both water and oxygen are needed for Acid Mine Drainage occurs,it is to be assumed that by
excluding either of these factors, it should be possible to minimise, or better, prevent Acid Mine
Drainage synthesis. One way in which this may be achieved is by flooding and sealing abandoned
deep mines. The dissolved oxygen (DO2) present in the flooding waters (ca. 8–9 mg/l) will be
consumed by mineral-oxidising (and other) microorganisms present, and replenishment of DO2 by
diffusion will be inhibited by sealing of the mine. However,this is only effective where the location of
all shafts and adits is known and where influx of oxygen-containing water does not occur (Johnson &
Hallberg, 2005).

19
7.1.1 Point source control
Neutralisation methods, are often considered the least detrimental to the environment as a means of
combating acid mine drainage (Hilson & Murck, 2001). For the subsequent seepage to be in
accordance with compulsory standards several factors are taken into account. These include: the
chemistry of the mine drainage; volume of water flow to be treated; terrain and the projected life of the
plant (Akcil & Koldas, 2006). Severalneutralisation agents are often used to combat acid mine
drainage. Of these,the one most utilised is the “Lime neutralisation” process (Kuyucak, 2001). During
this process mine drainage is allowed to flow rapidly into a mixing chamber, along with dry hydrated
lime (Ca(OH)₂). At low concentrations of ferrous iron (typically less than 50mg/L) the pH is raised to
6.0-8.0 in which it is then transferred to the settling chamber. Alternatively at high concentrations of
ferrous iron the pH is raised to between 8.0-10.0 and passed through an aeration tank, which changes
ferrous hydroxide precipitate into ferric hydroxide, then flowing into the settling chamber (Kuyucak,
2001) (Akcil & Koldas, 2006). The settling chamber allows heavy metals to precipitate out of solution,
meaning effluent waters can be returned to surface flows or stored for agriculture and consumption.
The simplest technique of neutralising acidic mine drainage lines a stream with limestone, and
contaminated water is treated as it flows over the limestone bed. However,this is not generally
effective due to the limestone rapidly becoming coated with iron (Fe), calcium sulphate (CaSo4) and
biological growth, which inhibits interaction with mine water (Kuyucak,2001) (Akcil & Koldas,
2006). It would seem that the most effective treatment would be the utilisation of both treatment
methodologies, much like that used in the case of WhealJane tin mine (see 7.2).
7.1.2 Migration control
Water is the mode of transport for contamination during acid mine drainage events, thus all intentions
to control the migration of mine drainage are aimed at water flow control, with the main concern of
inhibiting influent into the site as a means of impeding acid production (Akcil & Koldas, 2006). The
inhibition of water influent into abandoned mine workings can be controlled through severalmeans:
the controlled storage of acidic waste as to reduce contact with moisture which will initiate the process
of mine drainage; Prevention of seepage into mine workings; Prevention of infiltrating groundwater
floods, and surface water (rivers,streams,runoff etc.) diversion from the site (Akcil & Koldas, 2006).
The diversion of surface water is easily constructed but is rather difficult to maintain for significant
periods of time. Drainage systems can be implemented in locations allowing contaminated water to
infiltrate through a series of sealing layers (Akcil & Koldas, 2006). Open pit mines utilise several
approaches in the treatment of acid mine drainage. Of these, the two most utilised are as follows:
flushing, neutralisation (Akcil & Koldas, 2006).

20
 Flushing is the method where water from spoil heaps is drained promptly before ferrous
iron can begin to oxidise, which inhibits the reaction between pyrite and ferric hydroxide.
The major problem that is characteristic of this method is the acidity produced outside the
spoil heaps (Akcil & Koldas, 2006).
 In cases where mine drainage cannot be prevented, or it is difficult to do so, neutralisation
systems are often utilised. (Akcil & Koldas, 2006).
7.2 Bioremediation
Bioremediation of mine drainage originates from the capabilities of microorganisms to produce
alkalinity and immobilise metals, which in turn reverses the reactions responsible for the synthesis of
mine effluent (Johnson & Hallberg, 2005). As with other forms of mitigation there are two types of
bioremediation: active and passive.
7.2.1 Passive bioremediation
Bioremediation options for mine drainage are generally passive systems,with very few being used of a
large scale.
Compost bioreactors are one typical treatment of acid mine drainage and the key reactions involved
are all anaerobic (Johnson & Hallberg, 2005). In this process the microorganisms catalyse the
reactions which synthesise net alkalinity which in turn neutralises any net acidity in mine effluent
(Johnson & Hallberg, 2005). A variant on the compost bioreactor is the reducing and alkalinity
producing system (RAPS) systems (Figure 5) (Younger et al., 2003) (Johnson & Hallberg, 2005). Acid
mine drainage percolates downwards through a layer of compost, which promotes the removal of
dissolved oxygen, in turn causing a reduction of iron and sulphate. The contaminated water then
permeates through a limestone gravel bed, raising the pH further (Johnson & Hallberg, 2005).
Figure 5 Schematic of the RAPS systems (Younger et al., 2003)
Bioremediation schemes that employ a blend of both aerobic and anaerobic treatments are often used
for full-scale treatment of mine drainage, much like the system used at the Wheal Jane site (see section
7.3) (Johnson & Hallberg, 2005). The Acid Reduction Using Microbiology (ARUM) system (Kalin et
al., 1991) is just one example of a system that uses a combination of aerobic and anaerobic treatments.

21
In this system mine drainage first passes through two ARUM cells within which, alkali and sulphide
(SO4
2-
) are generated. The ARUM system then utilises two oxidation cells within which, iron (Fe) is
oxidised and precipitated. The organic materials that promote sulphate reduction in the ARUM cells
originate from the sulphate reducing bacteria in solution (Johnson & Hallberg, 2005).
7.2.2 Active bioremediation
The main active bioremediation system currently utilised is the sulfidogenic bioreactors, which has
three potential advantages over the passive counterpart.
 The performance can be controlled more easily
 Concentrations of sulphate are lowered considerably
 Heavy metals (Cu, Zn etc.),can be recovered to reuse
Although, like all active treatments, construction and day-to-day operational costs are expensive
(Johnson & Hallberg, 2005).
This particular type of bioreactor utilises hydrogen sulphide, produced by bacteria to generate
alkalinity and to remove metals as metal sulphides. The sulfidogenic bioreactors are constructed and
operated to enhance the production of hydrogen sulphide. Additionally the sulphur reducing bacteria,
which are particularly sensitive to slight changes in pH, are protected from the raw mine drainage
(Johnson & Hallberg, 2005).

22
7.3 Case Study; WhealJane Tin Mine
The most notorious case of acidic mine water pollution within the last couple of decade is the Wheal
Jane Tin Mine. The Wheal Jane tin mine is located in the Carnon River valley in Cornwall (Figure 6).
Wheal Jane operated as a tin mine from the early 18th century until 1991 when it was closed and
abandoned under the Mines and Quarries Act. This closure meant the halting of mine water pumping
and a subsequent increase in water levels. In January 1992, there was a discharge of contaminated
effluent into the Carnon River and into the Fal estuary. Brown (2002) is quoted to say that a
downstream drainage of 6.5 x 106 m2
of mine water with significant concentrations of iron generated
orange-brown discolouration (Brown et al., 2002). 2 years later in 1994, a pilot passive treatment
system was assembled to carry out a study into possible long term passive counteractive solution at
Wheal Jane. An active treatment system was constructed and became operational in 2000 (Claire,
2004).
Figure 6 Catchment area of the Wheal Jane Tin Mine (Environment Agency, 2007)

23
7.3.1 Pilot passive treatment
Shown below is a table with a breakdown of the seepage water, emanating from the Wheal Jane tin
mine. When you compare this with the water framework directive environmental quality standards
(Table 1) it paints a rather alarming picture (ppm =mg/L). The levels of iron in the Wheal Jane mine
are 150x the quality limits with sulphate (SO4
2-
) levels little over 3x the European standard, this
Table 2 Average Composition of effluent water from Wheal Jane 1995-98 (Claire, 2004)
Wheal Jane was an environmental crisis and thus needed a remediation plan implemented
immediately. Initially a pilot passive scheme was employed to research whether a passive treatment
would be feasible over a long period of time and be capable of the large volumes of water.
The passive treatment, which ran adjacent to the Carnon River, was made up of three components,
which treated the water in a slightly different manner. These were and can be seen in figure 7 below:
 Five artificial reed beds (aerobic cells) (yellow) which enabled precipitation of iron as ferric
hydroxide (ochre), with the additional benefit of arsenic removal, which precipitated onto the
iron precipitate
 The anaerobic cell (green) encourages bacterial growth which facilitate the reduction of
sulphate, increasing the pH and encouraging the precipitation of heavy metals (Cu, Zn, Cd &
Fe) as metallic sulphides
 The shallow rock filters (black) stimulate the growth of algae raising the pH of the water
further. Before entering these rock filters influent water is lime dosed as to raise the pH to 4.5
(Claire, 2004).

24
Figure 7 The pilot passive scheme at Wheal Jane (Claire, 2004)
This pilot scheme has a maximum design flow capacity of 0.6 l/s and can receive short term flows of
up to 1.9 l/s (Brown et al., 2002) (CLAIRE,2004). This is estimated to be less than 1 % of the total
mine water discharge from the Wheal Jane mine (CLAIRE,2004), which is rather insignificant. Scott
Wilson Mining Ltd, concluded that although the pilot passive scheme worked well, it required far too
much land that was necessary to completely treat the contaminated effluent arising from the mine
(Environment Agency, 2007).
7.3.2 Active treatment
The results of the pilot passive treatment determined that treatment using oxidation and chemical
neutralisation would be the most cost effective design. The active treatment plant was commissioned
in 2000 and designed to treat all of the mine water flow seeping from Wheal Jane (CLAIRE,2004),
The preferred design was a high density sludge (HDS) treatment system (Coulton et al., 2003) (Brown
et al., 2002). The treatment is a three part process which begins with the mixing of the mine effluent
and sludge, from there the mine water/slurry mix moves to an aeration chamber and further along to
the clarifier (CLAIRE,2004).
Contaminated water flowing from the mine workings is pumped using six pumps with a capacity of 55
l/s (total capacity 6 x 55 = 330 l/s) to the treatment plant. Water from the tailings pond and seepage
from the passive treatment plant are also treated (CLAIRE,2004).

25
Figure 8 Outline of the active treatment plant at Wheal Jane (Brown et al., 2002)
As seen in figure 8 and 10, contaminated effluent is transferred,via pumping, to the initial treatment
tank where recirculated sludge is added, at this stage the pH is raised to approximately 8.5 (CLAIRE,
2004). At the second stage aeration tank a slurry of 5 % lime is mixed into the sludge/effluent mix.
Aeration takes place through a diffuser in the base of the chamber. Due to the introduction of the lime
slurry the pH here is raised to 9.25. From the aeration chamber the fluid mix is piped into the clarifier
stage. Here the solids are allowed to settle towards the bottom of the tank and removed to the sludge
surplus tank or may be recirculated back to stage one (CLAIRE, 2004). The tailing dams are intended
to have all water evaporate with the intention to sealall remaining sediments in a soil cap as shown in
figure 9.
Figure 9 Soil cap to dried out sediments from leaching back into the environment (Johnson & Hallberg, 2005)
The sealing that covers the spoil (Figure 9) is usually fabricated from clay (Swanson et al., 2007),
which provides an anoxic environment preventing interaction between the acid producing minerals
and atmospheric oxygen (Johnson & Hallberg, 2005).

26
Figure 10 Aerial view of the Wheal Jane active treatment plant (Environment Agency, 2007)
During the first 2 years of operation, the system treated approximately 12,310,000 m3 of water
(CLAIRE,2004) (Coulton et al., 2003) (Brown et al., 2002). Furthermore Brown et al. (2002), states
that approximately 3,200 tonnes of metal was removed at an average efficiency of 99.2 % (CLAIRE,
2004) (Brown et al., 2002). As of April 2007 the treatment plant had treated 36,993,000 m3 of
contaminated mine water removing 7,537 tonnes of heavy metals (Environment Agency, n.d.)
Table 3 Simplified table of actual Wheal Jane data (Fowler, M., 2015, pers. Comms., 24 April)
Above in Table 3 is a simplified version of the Wheal Jane Treatment Plant Analysis Record located
in the appendix. It details the influent mine water pH and heavy metal concentrations and the effluent
once the contaminated water has passed through the active system. When compared with Table 1 and
15/10/2012
pH 3.900 9.000
Cadmium (Cd) 0.016 <0.001
Copper (Cu) 0.080 <0.01
Zinc (Zn) 22.730 0.120
Iron (Fe) 91.480 0.560
Nickel (Ni) 0.220 <0.01
Manganese (Mn) 3.680 0.160
Arsenic (As) 1.706 0.029
Aluminium (Al) 8.920 0.850
Calcium (Ca) 92.970 208.510
Lab results Minewater (ppm) Effluent (ppm)

27
4 below you can see the active system not only works, but exceeds performance benchmarks and
remains within the environmental quality standards (Table 1).
Table 4 Discharge limits of the Wheal Jane mine as set by the Environment Agency (Wheal Jane staff 2015, pers. Comms., 24
April)
From the data presented it is quite clear that the effluent discharging from the Wheal Jane tin mine is
under control and significant concentrations of heavy metal pollution has,and will continue to be,
reduced to values below Environment agency and Water Framework Directive environmental quality
standards

28
8. Discussion
From the results provided above it is clear to see the sheer volume of contaminants that are leaching
from not only Wheal Jane, but countless mines around the world, and it is a significant environmental
problem. Mine drainage puts both direct and indirect complications upon organisms in a particular
habitat (Gray, 1997) this is shown in Figure 11 below.
Figure 11 A chart displaying the effects of AMD on the biosphere (Gray, 1997)
The effects of Acid mine Drainage are so detrimental that often when a community collapses, recovery
is significantly repressed due to elimination of the habitat, highly toxic sediments and the
bioaccumulation of heavy metals in the organs of fauna (Gray, 1997).
Contrastingly from the data acquired from the Environment Agency with regards to the Wheal Jane
Tin Mine, it is clearly visible to see that the active style of treatment is working and significantly
reducing concentrations of heavy metals and increasing the pH to within Water Framework Directive
2000/60/EC (WFD) environmental quality standards (EQS) (Table 1).

29
Figure 12 Graphical representation of the percentage (%) decrease of the heavy metal concentration one treated in the
active treatment (based upon table 3)
Figure 12 shows the percentage decrease of the discharging effluent re-entering the Carnon River once
treated by the active system. It remarkably shows that the performance of the active treatment
reducing the major heavy metal contaminants between 87% - 99.5% with a high average of 95%
meaning that nearly all heavy metals seeping from Wheal Jane are removed out of solution. This
further visualises how well active treatments work.
It is often quoted that active treatments are increasingly expensive when compared to their passive
counterparts. With construction, maintenance and day-to-day running of the plant the costs amount.
However,in recent years every effort has been made to reduce the costs of running a treatment plant.
The Environment Agency, in collaboration with United Utilities, has made significant progress in
reducing costs and use of raw materials (Environment Agency, 2007).
 £1.8 million savings (15%) on the design, build and operation costs
 An 11% decrease in the use of lime per m3
of water processed
 1/3 decrease in the use of chemicals per m3
of water processed
 1/4 reduction in sludge production per m3
of water processed
This allowed The Environment Agency to purchase the tailing dam for sludge disposal from the
owners, which in turn allowed the site owners to remediate the area,attracting many new businesses

30
8.1 Iron
8.1.1 Toxicity
Iron (Fe), alongside Sulphate (SO4
2-
), is the main contaminant of mine drainage as seen in Table 2 &
3. When Iron enters the environment at significant concentrations, much like Wheal Jane, it poses not
only an environmental problem but a substantial effect upon the fauna that reside close to
contaminated waterways (Cheney et al.,1995). If high levels are ingested (10-20 mg/kg of elemental
iron) (Webmd.com, 2015), the free iron will react and damage DNA and Proteins (Cheney et al.,
1995). Table 4 shows that on average 180mg/L of iron potentially was entering the Carnon River more
than enough to be toxic for human, therefore smaller mammals it may prove fatal. (Cheney et al.,
1995) (Webmd.com, 2015).
With the introduction of the active treatment at WhealJane, levels of iron are significantly reduced (by
up to 99.39% in Figure 12).
8.1.2 Iron Bioremediation
Iron oxidising bacteria are often utilised in both active and passive forms of mine drainage treatment.
Several species of iron oxidising bacteria are utilised; Acidithiobacillus ferrooxidans (which favours
highly acidic conditions, perfect for treating mine drainage), Leptospirillumferrooxidans,and
Sulfobacillus thermosulfidooxidans (Gadd,2009). Each of these species oxidises iron through enzyme
action (Gadd, 2009). Another noteworthy species, is the fungus Aspergillus niger which was first
discovered thriving in Gold solutions (Singh, 2006). Aspergillus niger also can reduce heavy metal
sulphides, increasing solubility allowing them to dissolve back into the water (Singh, 2006).
8.2 Toxicity of Other Heavy Metals and Metalloids
Many of the heavy metals and metalloids that leach into the environment are highly toxic to humans
and animals, affecting their biology in many ways, these shall be discussed below.
8.2.1 Cadmium
An organism may be exposed to elemental Cadmium (Cd) through many pathways but the two chief
sources are in soils around heavily industrial areas of land or through consumption of contaminated
water,such as mine drainage or groundwater infiltration.
Exposure to cadmium can have severaldetrimental effects upon the body; more severe contact with
cadmium can cause severalpulmonary implications (Jarup, 1998). Furthermore, the kidneys of
organisms may lose function to remove acids from the blood (Jarup, 1998). Additionally, the kidneys

31
of organisms may shrink up to by up to a quarter of their original size (Jarup, 1998), with added
problems including the synthesis of kidney stones. Jarup (1998) states that the damage to the kidney
inflicted by cadmium poisoning is often irreparable, and may lead to renal failure in extreme cases.
As shown in table 4, the levels seeping from Wheal Jane,even at maximum recorded of 0.15ppm,
would only cause a cough or irritation to the respiratory system. However,ingestion at the
concentration emitted from Wheal Jane would cause nausea,vomiting and abdominal pain shown in
Table 5 below.
Table 5 Threshold toxicity values of cadmium (Cd) (Health Protection Agency, 2011)

32
8.2.2 Lead
Lead (Pb) is highly toxic in humans due to the detrimental effect of severalbiological systems within
the body: gastrointestinal, neuromuscular, and neurological (Pearce,2007). Shown in table 6 below
you can see the severe effects of ingesting lead into the body. At the maximum recorded concentration
of lead leaching from Wheal Jane of 0.60 ppm (table 4) (µg dL-1
) there are severe gastrointestinal
implications in adults
Table 6 Threshold toxicity values of lead (Pb) (Health Protection Agency, 2007)

33
8.2.3 Arsenic
Arsenic (As) is highly lethal in humans (table 7) even a dose as small as 1-3ppm (mg kg-1
) will result
in death. Arsenic results in the disruption of Adenosine triphosphate (ATP) synthesis in the
mitochondrion of organisms (Casarett,et al., 2003). This is often results in death from multi-organ
failure, which is a consequence of necrotic cells (Casarett,et al., 2003).
Table 7 Threshold toxicity values of Arsenic (As) (Health Protection Agency, 2011)
The mine water effluent had extreme concentrations of Arsenic, with an average of 3.00ppm up to a
maximum of 16.00ppm recorded (table 4) more than 3x the lethal dosage in humans (Casarett,et al.,
2003).
8.3 Treatment
Each process has its pro and cons in dealing with effluent arising from abandoned mines with the
passive style of treatment often being the less expensive but incapable of dealing with large volumes
of contaminated mine water,whereas an active style of treatment is often increasingly expensive and
use numerous resources, but can deal with all mine effluent and treat it removing up to 99% of heavy
metals (figure 12). All current evidence suggests that a more active style of treatment is the “best fit”
as to prevent acid mine drainage.
However,anoxic limestone drains (ALD) are an effective, economical forms of passive alkalinity
addition for AMD having dissolved O2, ferric iron and aluminium concentrations.
The coupling of both active and passive technologies could improve the capacity of passive treatments
without using large areas of land, whilst reducing the energy, raw materials and money needed to run
and maintain a sole active treatment scheme. One method of achieving this could be having a passive
treatment as a primary stage reducing the contaminant and heavy metal pollution. The active
secondary stage would then require less raw materials, such as lime, to carry out effective effluent
treatment, cutting costs further.

34
9. Conclusions
 Acid mine drainage is a significant pollution problem and has called for real investment into
technologies to alleviate the environmental impacts that occur due to discharging mines.
 Consensus agrees that active treatments can deal with large capacities of discharging mine
drainage.
 In order to not further add to polluting the environment passive techniques have been studied,
but can only deal with low volumes of discharging mine waters.
 Passive treatments would be viable to use on smaller water courses,such as creeks or streams.
 Pilot passive at WhealJane scheme clearly proven the potential for natural reduction of acid
mine drainage, particularly iron oxidation, by microorganisms.
 Wheal Jane tin mine is under control and significant concentrations of heavy metal pollution
has, and will continue to be, reduced to values below Environment agency and Water
Framework Directive Environmental Quality Standards
 A number of processes have been established to successfully characterise,manage and
remediate AMD synthesising mine sites with the aim to protect surface and groundwaters.
 The importance of a procedure with clear objectives is imperative to positive renovation of
abandoned mines and prolonged environmental protection.
 It would seem that there is no perfect way in treating acid mine drainage. Many factors
contribute to what system can be utilised to remediate mine drainage in the best way.
 Much like the Environment agency are doing at Wheal Jane,focus on reducing the
environmental impact of active treatment is imperative.
1. Couple both passive and active treatments together.
2. Utilising the passive treatment as a primary stage,cleansing the AMD
at its natural capacity.
3. This allows the active treatment to become smaller, reducing costs of
construction, running and maintenance; less raw materials are needed
as the passive treatment would remediate some of the effluent
4. Due to this design less land would be needed to utilise a sole passive
treatment to deal with the large volumes of AMD

35
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39
Appendices.
Appendix 1.
The Wheal Jane treatment plant analysis record from an external laboratory. It records the pH, Total
Suspended Solids (TSS) and heavy metal pollution of the sample mine water and compares it to
effluent that has passed through the active treatment. It shows a significant reduction in pollutants,
providing evidence that the treatment works.

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