Mine waste management completes notes for iitbhu m.tech syllabus

1. MN5226: WASTE MANAGEMENT IN MINES
Mine waste due to-
 Extraction
 Beneficiation
 Mineral processing
Mining wastes is generated during the process of extraction, beneficiation and
processing of minerals. Extraction is the first phase that consists of the initial removal of
ore from the earth. This is normally done by the process of blasting, which results in
generation of large volume of waste (soil, debris and other material). This is useless for
the industry and is normally just stored in big piles within the mine lease area, and
sometimes, on public land. The bigger the scale of the mine, greater is the quantum of
waste generated. Opencast mines are therefore more pollution intensive as they
generate much higher quantities of waste compared to the underground mines. Open-
pit mines produce 8 to 10 times as much waste as underground mines.
Once the ore is brought to the surface, it is processed to extract the mineral, which itself
generates immense quantities of waste. That’s because the amount of recoverable
metal in even high-grade ores is generally just a small fraction of their total mass.
Moreover, as the higher grade mineral deposits are getting exhausted, the mineral
industry is generating more and more quantity of waste, as they have to now depend on
lower grades of reserve. For example, in the United States, the copper ore mined at the
beginning of the 20th century consisted of about 2.5 percent usable metal by weight;
today that proportion has dropped to 0.51 percent.
Waste
Waste rock Mining operations generate two types of waste rock - overburden10 and mine
development rock. Overburden results from the development of surface mines, while mine
development rock is a byproduct of mineral extraction in underground mines. The quantity and
composition of waste rock varies greatly from site to site, but these wastes essentially contain the
minerals associated with both the ore and host rock. The ratio of overburden excavated to the amount
of mineral removed is called the overburden ratio or stripping ratio. For example a stripping ratio of
4:1 means that 4 tonnes of waste rock are removed to extract one tonne of ore. Lower the ratio, the
more productive the mine. Stripping ratio varies with the area under mining. For example, stripping
ratio of limestone in Himachal Pradesh is almost zero whereas in Rajasthan it is 0.308 (i.e. 300 kg of
waste per tonne of limestone mined).11 The overburden ratio for surface mining of metal ores
generally ranges from 2:1 to 8:1 depending on local conditions.1

2. Chemical aspects of environmental pollution by mine
wastes and their impact.

3. Chemical aspects of environmental pollution by mine wastes and their impact, organized
by topic:
1. Heavy Metals:
 Mine waste pollution often involves the release of heavy metals such as lead,
mercury, cadmium, arsenic, and copper.
 These metals are toxic to living organisms, even at low concentrations, and can
cause various health problems.
 Heavy metals can accumulate in the food chain through a process called
bioaccumulation, leading to higher concentrations in organisms at higher
trophic levels.
 Humans consuming contaminated food, such as fish from contaminated water
bodies, can suffer from neurological disorders, kidney damage, and increased
cancer risks.
2. Acid Mine Drainage (AMD):
 Acid mine drainage is a significant concern associated with mine waste
pollution.
 It occurs when sulfide minerals, such as pyrite, are exposed to air and water
during mining activities or weathering of tailings.
 Sulfide minerals react with oxygen and water, producing sulfuric acid and
lowering the pH of the surrounding environment.
 Acidic drainage can contaminate surface and groundwater, leading to the
destruction of aquatic habitats and the death of aquatic organisms.
 Acidic conditions increase the solubility of heavy metals, accelerating their
release and mobility in the environment.
3. Cyanide and Other Chemicals:
 Cyanide is commonly used in gold mining to extract gold from ore.
 Improper management of cyanide can result in its release into water sources,
causing acute toxicity for aquatic life.
 Polycyclic aromatic hydrocarbons (PAHs) are organic compounds that can be
released from mine wastes.
 PAHs have the potential to cause cancer and other health issues in both
humans and wildlife.
4. Waste Management and Remediation:
 Proper waste management practices are essential to mitigate the
environmental impact of mine wastes.

4.  Engineered tailings storage facilities, liners, and covers can prevent the release
of contaminants into the environment.
 Techniques such as neutralization and chemical stabilization can be employed
to mitigate acidity and reduce the mobility of heavy metals in mine wastes.
 Regular monitoring and assessment of mine waste sites are crucial to identify
risks and implement appropriate remediation measures.
5. Regulations and Standards:
 Enforcing stringent regulations and standards for mining operations is crucial
to minimize the generation of mine wastes.
 Responsible disposal practices should be implemented to ensure the proper
management of mine wastes.
 Compliance with regulations helps prevent and mitigate the chemical aspects
of environmental pollution from mine wastes.
By understanding these topics related to the chemical aspects of mine waste pollution, it
becomes possible to address the associated environmental risks and work towards
sustainable mining practices that minimize the impact on ecosystems and human health.
 Production and characterization of solid wastes in different
types of mines.
Here's a detailed explanation of the production and characterization of solid wastes in
different types of mines, organized by topic:
1. Types of Mines:
 Surface Mines: These mines involve the extraction of minerals or resources
that are located near or at the surface of the Earth. Examples include open-pit
mines and quarrying operations.
 Underground Mines: These mines involve extracting minerals or resources
from below the Earth's surface. They typically involve tunneling and drilling to
access the desired materials.
 Placer Mines: Placer mining involves the extraction of minerals, such as gold,
from alluvial deposits found in riverbeds, beach sands, and other sedimentary
environments.
 Subsurface Mines: These mines involve the extraction of resources from
subsurface deposits, such as coal mines and some metal ore deposits.
2. Solid Wastes in Mines:

5.  Overburden: Overburden refers to the soil, rock, and other materials that are
removed to access the desired minerals or resources. It is often the largest
component of solid waste in mining operations.
 Mine Tailings: Tailings are the finely ground rock and mineral waste materials
that remain after the desired minerals have been extracted from the ore. They
are typically in the form of a slurry or a dry material.
 Spoils: Spoils are the waste materials generated during the extraction of
minerals, such as coal, from underground mines. They consist of rock, soil, and
other materials that are displaced during the mining process.
 Waste Rock: Waste rock refers to the non-mineralized rock or rock that has low
mineral content that is excavated during mining operations. It is often stored in
waste rock piles or used for construction purposes.
 Slag: Slag is a waste product generated during the smelting or refining of metal
ores. It consists of impurities and non-metallic materials that are separated
from the desired metal.
3. Characterization of Mine Wastes:
 Physical Properties: Mine wastes can vary in terms of particle size distribution,
density, and moisture content. For example, tailings can range from fine-
grained slurries to coarser dry materials.
 Chemical Composition: Mine wastes can contain various minerals, metals, and
elements depending on the type of mine. For instance, tailings can contain
residual amounts of the desired metal, as well as potentially toxic elements like
arsenic or mercury.
 Geochemical Properties: The geochemical properties of mine wastes are
important in understanding their potential for leaching or releasing
contaminants into the environment. Factors such as pH, redox conditions, and
mineralogy can influence the mobility of pollutants.
 Stability and Behavior: The stability and behavior of mine wastes are critical
considerations for waste management. For example, the potential for acid
generation and acid mine drainage is influenced by the presence of sulfide
minerals in the waste rock or tailings.
4. Environmental Impacts:
 Erosion and Sedimentation: Improper management of mine wastes can lead to
erosion and sedimentation, which can impact water bodies, aquatic habitats,
and downstream ecosystems.
 Contamination of Water and Soil: Mine wastes, particularly tailings, can release
chemicals and heavy metals into nearby water bodies and soil. This

6. contamination can harm aquatic life, pollute drinking water sources, and affect
agricultural productivity.
 Acid Mine Drainage: The presence of sulfide minerals in mine wastes can result
in acid mine drainage, leading to the release of acidic water with high
concentrations of heavy metals. This can have severe environmental
implications for aquatic ecosystems.
 Habitat Destruction: The disposal and accumulation of mine wastes can result
in the loss or degradation of natural habitats, impacting flora and fauna in the
surrounding areas.
5. Waste Management and Mitigation Strategies:
 Tailings Management: Proper storage and containment of tailings are crucial to
prevent their release into the environment. Techniques such as tailings dams,
liners, and covers can be employed to minimize the risk of contamination.
 Waste Rock Management: Waste rock can be stored in designated areas, and
measures like revegetation and erosion control can be implemented to reduce
environmental impacts.
 Rehabilitation and Reclamation: Rehabilitating and reclaiming mining sites
after operations cease can help restore ecosystems and minimize long-term
environmental impacts.
 Monitoring and Regulation: Regular monitoring of mine wastes and compliance
with environmental regulations are essential to identify potential risks and
implement appropriate mitigation measures.
Understanding the production and characterization of solid wastes in different types of
mines is crucial for developing effective waste management strategies and minimizing the
environmental impact of mining operations. By implementing sustainable practices and
adhering to strict regulations, it becomes possible to mitigate the adverse effects of mine
wastes on ecosystems and human health.
Solid waste in mines can be classified as mine waste or ore beneficiation plant waste.
Mine waste is usually in large quantities but mostly inert. It can include:
Tailings
A granular waste material that is a composite of clay, silt and sand-sized particles. Tailings are produced when
rock containing economic grades of ore-forming minerals is crushed.
Waste rock
Additional waste rock that must be separated from the ore when extracting the seams.
Gangue

7. Additional waste rock that is finely ground to produce more waste material.
Gaseous wastes
Compounds produced during smelting or other processing, such as sulfur dioxide.
Solid mine wastes
Include slag, metallurgical materials, and contaminated river sediments.
 Generation and characterization of mine effluents and
leachate.
1. Generation of Mine Effluents and Leachate:
 Mine Effluents: Mine effluents refer to the liquid waste streams that are
generated during mining operations. These effluents can originate from various
sources, including dewatering of underground mines, water used for mineral
processing, and runoff from mining areas.
 Leachate: Leachate is the liquid that percolates through mine wastes, such as
tailings or waste rock, and picks up dissolved or suspended contaminants. It is
typically formed when water interacts with the waste materials, facilitating the
release of substances into the leachate.
2. Composition of Mine Effluents and Leachate:

8.  Suspended Solids: Mine effluents and leachate can contain suspended solids,
including fine particles of rock, minerals, and ore residues. These solids can
contribute to turbidity in water bodies, affecting light penetration and aquatic
ecosystems.
 Chemical Contaminants: Mine effluents and leachate can contain various chemical
contaminants, such as heavy metals (e.g., lead, mercury, arsenic), metalloids,
acids, metal salts, and other toxic substances. These contaminants can pose risks
to aquatic life, human health, and overall ecosystem integrity.
 pH and Acidity: Depending on the type of mine and the presence of sulfide
minerals, mine effluents and leachate can exhibit acidity or high/low pH levels.
Acidic effluents can result from acid mine drainage (AMD) when sulfide minerals
react with air and water, leading to the release of sulfuric acid.
3. Environmental Impacts:
 Water Pollution: Mine effluents and leachate can contaminate nearby water
bodies, including rivers, lakes, and groundwater sources. The discharge of these
pollutants can degrade water quality, harm aquatic organisms, and disrupt
ecosystems.
 Soil Contamination: If mine effluents or leachate come into contact with soil, they
can contaminate it with various chemical substances. This contamination affects
soil health and may limit its ability to support plant growth and other ecosystem
functions.
 Human Health Risks: The presence of harmful substances, such as heavy metals or
acidic compounds, in mine effluents and leachate can pose risks to human health.
These contaminants can enter the food chain through the consumption of
contaminated water or crops, leading to long-term health effects.
4. Characterization and Monitoring:
 Sampling and Analysis: Characterizing mine effluents and leachate involves the
collection of representative samples and subsequent laboratory analysis.
Techniques such as water sampling, ion chromatography, spectrophotometry, and
atomic absorption spectroscopy can be used to identify and quantify
contaminants.
 Parameters of Interest: Important parameters to consider during characterization
include pH, electrical conductivity, total suspended solids, turbidity, dissolved
oxygen, and concentrations of various chemical pollutants.
 Monitoring Programs: Regular monitoring programs are essential to assess the
quality of mine effluents, leachate, and the receiving environment. Monitoring
helps identify trends, evaluate the effectiveness of mitigation measures, and
ensure compliance with environmental regulations.

9. A holistic approach to mineral waste management
The 3Rs pyramid is commonly used in policy making, e.g. in the European Union . It
was primarily designed for post-consumer waste, as for example the term ‘re-use’ fits
a type of waste that has already had a use phase, i.e. a discarded product. Likewise,
the 3Rs pyramid places ‘re-use’ higher than ‘recycling’ because preserving the
integrity and the function of a product is more desirable - and energy efficient - than
tearing it apart to recycle its individual elements. The paper from Lottermoser (2011)
is an example from academia of application of the 3Rs pyramid to mining wast.
ottermoser (2011) adapts the terms ‘re-use’ and ‘recycle’ to mining waste. re-use is
defined as making use of the total mine waste without any prior reprocessing,
whereas recycling involves a reprocessing stage which aims at either extracting ‘new
valuable resource ingredients’, or making the entire mine waste usable for a new
application. re-use is then considered superior to recycling as the absence of
reprocessing stage saves energy, water and other resources. Although valid, this
categorisation does not consider the minerals contained within mining waste, and
which - under certain conditions - justify the use of additional resources for its
extraction.

10.  Tailings – characterization, technical issues, sampling and
analysis, site selection and design of tailings impoundment,
tailings dam failure.
Tailings are waste materials produced by mining mineral resources. They can be
liquid, solid, or a slurry of fine particles. Tailings are usually highly toxic and
potentially radioactive.
Tailings have the following characteristics:
 Chemical composition: Includes changes to chemistry through mineral processing and its
ability to oxidize and mobilize metals
 Physical composition and stability: Includes static and seismic loading, behavior under
pressure, and consolidation rates
 Erosion stability: Includes wind and water
Tailings dams are earth-fill embankment dams used to store byproducts of mining
operations. They can be huge in size, as big as lakes, and reach 300 meters high.
Some technical issues with tailings dams include:
Failure
Tailings dams are failing with increasing frequency and severity. Failure can be caused by multiple
factors, such as increased loading of the tailings dam, earthquakes, rainfall, floods, and dam foundation
subsidence
Design
The design procedure for tailings dams has been intertwined with structural and pollution requirements
including stability, geological and geotechnical investigations on site, materials used, seepage control,
and erosion

11. Some steps for analyzing a tailings dam breach include:
 Estimation of the release tailings volume
 Estimation of the water in the tailings (moisture contents) and the free water in the facility
(pond size)
 Calculation of tailings concentration
 Development of the breach hydrograph
 Routing the hydrograph
Explanation of tailings, covering characterization, technical issues, sampling and analysis,
site selection and design of tailings impoundment, and tailings dam failure:
1. Tailings Characterization:
 Definition: Tailings are the waste materials generated from mineral processing
operations. They consist of finely ground rock particles, water, and residual
chemicals used during the extraction of valuable minerals from ore.
 Physical Properties: Tailings can vary in physical properties depending on the
type of ore being processed, the mineral processing techniques employed, and
the characteristics of the rock. They can range from fine-grained sandy
materials to slurry-like substances.
 Chemical Composition: The chemical composition of tailings is determined by
the type of ore and the chemicals used during mineral processing. Common
constituents include residual reagents, heavy metals, metalloids, and other
trace elements. The composition of tailings is an important factor in assessing
their potential environmental impact.
2. Technical Issues Related to Tailings:
 Stability: Tailings must be deposited and stored in a manner that ensures their
stability over time. This involves considering factors such as slope stability,
consolidation, and liquefaction potential to prevent catastrophic failures.
 Water Management: Tailings often contain significant amounts of water, which
must be managed to prevent excessive seepage, minimize the risk of dam
failure, and facilitate the consolidation and compaction of the tailings.
 Geotechnical Considerations: Geotechnical factors, including the composition
and physical properties of the tailings, affect their behavior and stability.
Factors such as particle size distribution, shear strength, and settlement
characteristics must be considered in the design and management of tailings
storage facilities.
3. Sampling and Analysis of Tailings:

12.  Representative Sampling: Proper sampling techniques are essential to obtain
representative samples of tailings for analysis. Samples should be collected at
various locations and depths to capture the heterogeneity of the tailings.
 Laboratory Analysis: Once samples are collected, laboratory analysis is
conducted to determine the physical and chemical properties of the tailings.
This may involve tests for particle size distribution, settlement characteristics,
moisture content, and chemical composition, including the presence of
contaminants.
4. Site Selection and Design of Tailings Impoundment:
 Site Selection: The selection of a suitable site for a tailings impoundment
involves considering factors such as geology, topography, hydrogeology, and
proximity to water bodies and communities. Environmental and social impact
assessments should be conducted to evaluate potential risks and impacts.
 Design Considerations: Tailings impoundments are typically designed as
containment structures to store and manage tailings. Design considerations
include slope stability, liner systems to prevent seepage, erosion control
measures, and water management systems. The design must comply with
regulatory requirements and consider long-term stability and closure plans.
5. Tailings Dam Failure:
 Causes of Failure: Tailings dam failures can occur due to various factors,
including improper design, inadequate maintenance and monitoring, extreme
weather events, seismic activity, or human error. Failures can result in the
sudden release of large volumes of tailings, posing significant risks to human
life, the environment, and infrastructure downstream.
 Consequences: Tailings dam failures can have severe environmental and socio-
economic consequences. They can lead to the contamination of water bodies,
destruction of ecosystems, displacement of communities, loss of livelihoods,
and long-term environmental damage. The impacts can extend far beyond the
immediate area of the failure.
 Mitigation and Prevention: To mitigate the risk of tailings dam failures,
measures such as regular inspections, monitoring of dam performance, proper
maintenance, and emergency response plans should be implemented.
Advances in dam design, including improved construction techniques and the
incorporation of advanced monitoring systems, can help prevent failures.
Management of different types of mine wastes
Here are some ways to manage mine waste:
Mine wastewater

13. Mine water is usually monitored and treated before it's released back into the environment.
Mill tailings
A mud-like, toxic material that's a product of mineral processing. Tailings can contain large amounts of
processing chemicals and should not be released into the environment. Tailings can be disposed of in a
variety of ways, including pond storage, dry sacking, into underground workings, or in the ocean.
Waste management
Proper management of mining waste can help prevent or minimize the release of contaminants into the
environment. This can include using lined storage facilities, implementing recycling and reprocessing
techniques, and employing proper disposal methods.
Acid mine drainage
This is one of the most difficult mine waste problems to deal with. It degrades both surface and
groundwater quality and can continue to pollute even after mines are closed.
Bioremediation
Stimulating the development of microbially reducing conditions, for example in constructed wetlands,
can be beneficial for remediating many metals associated with mine wastes.
1. Overburden and Waste Rock:
 Definition and Generation: Overburden refers to the rock and soil that must be
removed to access mineral deposits during mining operations. Waste rock is
the rock material that is not economically viable for mineral extraction.
 Management Practices: Overburden and waste rock are typically stored in
designated areas called waste rock dumps. These dumps are engineered to
minimize erosion, control water infiltration, and prevent the release of
contaminants. Stability assessments and monitoring are conducted to ensure
the long-term integrity of the dumps. Reclamation measures, such as covering
the waste rock to reduce erosion and promoting vegetation growth, may also
be employed.
2. Tailings:
 Definition and Generation: Tailings are the waste materials produced during
mineral processing operations. They consist of finely ground rock particles,
water, and residual chemicals.
 Storage and Containment: Tailings are often stored in impoundments, known
as tailings storage facilities or tailings ponds. These facilities are designed to
contain and manage the tailings, preventing their release into the
environment. Measures such as liners, embankments, and water management
systems are implemented to ensure stability and minimize the risk of
contamination.

14.  Rehabilitation and Closure: After mining operations cease, tailings storage
facilities undergo rehabilitation and closure. This involves stabilizing the
tailings, recontouring the land, and implementing erosion control measures.
Long-term monitoring and maintenance may be required to ensure the
stability and environmental integrity of the closed facility.
3. Acid Mine Drainage (AMD):
 Definition and Formation: Acid mine drainage occurs when sulfide minerals in
mine wastes or exposed rock surfaces react with air and water, leading to the
generation of acidic conditions and the release of harmful substances.
 Prevention and Treatment: Preventive measures include minimizing the
exposure of sulfide minerals to air and water through proper waste
management and covering exposed surfaces. Treatment techniques for AMD
include neutralization through the addition of alkaline substances, such as
lime, and the use of wetlands or constructed wetland systems to naturally
treat the acidic water.
4. Cyanide and Heavy Metal Contamination:
 Cyanide Contamination: Cyanide is commonly used in gold mining to extract
gold from ore. Effective management involves employing proper containment
and treatment systems to prevent the release of cyanide into the environment.
Cyanide destruction processes, such as chemical oxidation or biological
degradation, may be employed.
 Heavy Metal Contamination: Heavy metals, such as lead, mercury, and arsenic,
can pose significant environmental risks if released from mine wastes.
Management strategies include proper containment, such as the use of liners
and covers, to prevent leaching or runoff. Treatment methods may include
chemical precipitation, ion exchange, or biological remediation techniques.
5. Radioactive Waste:
 Definition and Handling: Radioactive waste can be generated during mining
and mineral processing operations, particularly in uranium mining or rare earth
element extraction. Strict protocols are in place to handle and manage
radioactive waste. This involves containment and isolation measures to
prevent radiation exposure to workers and the environment.
 Long-Term Storage: Radioactive waste is typically stored in specially designed
facilities, such as underground repositories or engineered containment
structures. These facilities ensure the isolation and containment of radioactive
materials for extended periods, following strict regulatory requirements and
safety standards.
6. Reclamation and Closure:
 Reclamation Planning: Reclamation planning starts during the early stages of
mine development. It involves developing comprehensive plans to restore

15. mined areas to a stable and environmentally sustainable condition after mining
activities cease. This includes addressing the physical, chemical, and biological
aspects of the site.
 Landform Reconstruction: Landforms are reconstructed to resemble the pre-
mining topography as closely as possible. This may involve reshaping,
regrading, and stabilizing the land to establish suitable conditions for
vegetation establishment.
 Revegetation: Revegetation is a key component of mine reclamation, aiming to
restore plant communities and ecosystem functions. Native plant species are
often selected to promote biodiversity and ecological resilience. Soil
amendments and erosion control measures may be implemented to support
successful plant establishment.
COAL WASHERY
A coal washery is a process that uses water and mechanical techniques to remove
non-combustible impurities from coal. This process is an integral part of coal
production.
Coal washing uses the difference in density between coal and its impurities to
enrich the coal. Impurities are usually more densely packed because they are
inorganic. Washing coal increases its quality and efficiency, which increases its
price.
Coal washing machines have a rotating drum that separates impurities from the coal
and other coal washing plants.
Coal consumer or an operator on their behalf can set up coal washeries to obtain
coal of desired quality
A coal washery, also known as a coal preparation plant (CPP), is a facility designed to
remove impurities from coal before it is used as fuel in power plants or other
industrial processes. The process of coal washing involves various techniques to
separate and remove unwanted materials, such as rock, soil, and mineral matter,
from the raw coal, thereby improving its quality and reducing environmental
impacts.
Here are the key aspects of a coal washery:
1. Raw Coal Handling: The process begins with the reception of raw coal from
the mine. The coal is typically delivered by trucks or conveyors and stored in
stockpiles before further processing.

16. 2. Sizing and Crushing: The raw coal is then crushed to a desired size to facilitate
efficient separation of coal and impurities. Crushing can be done using
crushers or through a combination of crushers and screens.
3. Dense Medium Separation (DMS): DMS is a widely used coal washing
technique. In this process, the crushed coal is mixed with a dense medium,
typically a suspension of fine magnetite particles in water. Different densities
of coal and impurities cause them to separate in a dense medium cyclone or
bath. The heavier coal particles sink, while the lighter impurities float and are
removed.
4. Jigging: Jigging is another common coal washing method that relies on the
principle of gravity separation. In this process, the crushed coal is fed into a
pulsating water-filled chamber where the heavier coal particles settle to the
bottom, while the lighter impurities are carried away by the water flow.
5. Froth Flotation: Froth flotation is used to separate fine coal particles from
mineral matter and other impurities. In this process, air bubbles are introduced
into a suspension of coal and water, causing the coal particles to attach to the
bubbles and rise to the surface as a froth. The froth is then mechanically
skimmed off, leaving behind the impurities.
6. Dewatering: After the coal washing process, the clean coal undergoes
dewatering to reduce its moisture content. Various techniques such as
centrifuges, filters, or thermal drying methods may be employed to achieve
this.
7. Product Handling and Storage: The final product, known as clean coal, is then
transported to storage facilities or directly to customers. It may be stored in
stockpiles or loaded onto trains or trucks for delivery.
8. Water Management: Coal washery operations require significant amounts of
water for the washing process. Efforts are made to minimize water
consumption through recycling and reuse systems. Water treatment facilities
are also employed to remove pollutants and ensure compliance with
environmental regulations.
9. Environmental Considerations: Coal washery operations have environmental
implications due to the generation of waste materials, such as discarded rock
(rejects) and water contaminated with impurities. Proper management of these
waste materials, including their disposal or utilization, is necessary to minimize
environmental impacts.

17. What is the process of coal washing?
Coal washing is accomplished by one of two major processes, by density separation or by
froth flotation. Both processes depend on the fact that the particles of which a coal sample are
made have different densities. When water is added to the sample, particles sink to various
depths depending on their densities.