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CHAPTER VIII

EFFECTS OF MINING AND COAL PROCESSING ON

ENVIRONMENT

8.1 INTRODUCTION

Coal, as a sedimentary rock, is a complex heterogeneous mixture of organic and

inorganic constituents containing intimately mixed solid, liquid, and gaseous phases of

allothigenic or authigenic origin (Vassilev and Vassileva 2009). When coal is separated

from its impurities by cleaning processes, coal tailings are formed and deposited usually in

close proximity to the coal washery area. According to Finney et al. (2009), this material

presents elements, such as carbon, hydrogen, nitrogen, and sulfur, in addition to various

metals, such as aluminium (Al), arsenic (As), calcium (Ca), chromium (Cr), copper (Cu),

iron (Fe), potassium (P), magnesium (Mg), molybdenum (Mo), sodium (Na), phosphorus

(P), lead (Pb), silicon (Si), and zinc (Zn). Some of these compounds are dangerous because

they have impact on the environment and human health (Silva et al. 2008).

The tailings from coal improvements constitute one of the major environmental

problems faced by the mining industry. Both nitrogen and sulfur emissions can react in the

atmosphere to form acid rain, which can then acidify lakes and streams, corrode buildings

and monuments, and cause adverse effects on growth of plant. Acid mine drainage, a

widespread environmental concern, is produced by the oxidation of pyrite in the coal or in

the strata overlying the coal. Reaction of sulfur in pyrite with water and air forms sulfuric

acid (Finkelman and Gross 1999). Moreover, adverse effects such as genotoxicity and

carcinogenicity have been attributed to metals present in coal, caused by oxidative stress

(Miadokova et al. 1999; Silva et al. 2000).

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The high levels of acidification resulting from the oxidation of pyrite might cause

dissolution of aluminosilicate minerals, increase the concentration of metals such as Al, Fe,

Mn, Cu, Ni, and Zn to toxic levels (Campos et al. 2003). Pyrite is the most abundant and

dominant sulfide in coal and its by-products. Earlier studies have shown that

pyrite/aqueous suspensions generate H2O2 in the absence of oxygen and during pyrite

oxidation. Although the formation of H2O2 has been established in pyrite suspensions, its

fate is not clear.

Coal refuse contains a lot of carbon, which is the source of CO2 emissions. Open-

air coal refuse dumps are easily weathered by wind and water, and the weathered particles

are also easily eroded by wind and rain, which ultimately enter in air and soil. Coal refuse

containing pyrite, sulfur, coal, etc., can easily cause spontaneous combustion and the

release of a large number of toxic and harmful gases, such as SO2, CO and H2S. With the

rainfall leaching and flushing, heavy metals in coal refuse could be released into surface

water and groundwater, resulting in heavy metals contamination of water bodies.

Earlier studies on environmental impacts of coal mining have shown that soil

acidity, toxic metal concentrations (Adriano, 2001) and vegetation damage (Madejon and

Murillo 2002) are the predominant negative impacts of Acid Mine Drainage (AMD).

Seepage of water from overburden dumps, exposed overburden and coal processing etc.

constitutes mining effluent, which contains heavy metals (Wong, 2003). Pollution of the

natural environment by heavy metals is a worldwide problem because these metals are

indestructible and most of them have toxic effects on living organisms above certain

concentration levels (MacFarlane and Burchett 2000).

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8.2 ENVIRONMENTAL EFFECT OF PABEDANA COAL MINING AND

WASHERY

In the process of development, coal mining is one of the prime industrial sectors

which inadvertently cause environment pollution. Pabedana area with an estimated

population of over 1,11,24,000 owes its urban and rural mixed status primarily due to the

existence of very large deposits of coal. Its present large population has during last two

decades both due to large number of coal mining and coal washing plant activities. Other

environmental pollution includes high suspended particulate matters in active mining areas

especially in opencast mining areas. It also includes devegetation and presence of noxious

gases like CO, H2S in the environment. Suspended particulate matters, SO2 and NOX are

found respectively in the range of 193.4 – 1242.5 µg/m3 and 54-76 µg/m3 in mining area of

the basin. CO level is found in the range of 1950-2210 µg/m3 which is partly due to

vehicular exhaust from heavy mining equipments.

8.2.1 Subsidence in mining area

Shadbolt (1978) provided a historical review of the various theories relating to

mining subsidence due to total extraction of coal. According to Lehman (1919), the

subsidence that occurs over a completely mined out area in a flat seam is trough-shaped

and extends outwards beyond the limits of mining in all directions. In trough subsidence

the resulting stratal and surface ground movements are regarded as largely

contemporaneous with mining, producing more or less direct effects at the surface

(Brauner, 1973). About 7 sq.Km area is subsided due to underground mining. Trough

shaped subsidence profiles develop tilt between adjacent points that have subsided

different amounts and curvature results from adjacent sections that are tilted by differing

amounts. Maximum ground tilts are developed above the limits of the area of extraction

and may be cumulative if more than one seam is worked up to a common boundary. Where

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movements occur, points at the subside downwards and are displaced horizontally inwards

towards the axis of the excavation.

8.2.2 Air Pollution around mining area

There are two main sources of air pollution during the coal production process in

Pabedana area. The first is methane emissions from the mines. Methane is a powerful heat-

trapping gas and is the second most significant contributor to global warming after carbon

dioxide. Coal mining results in the release of 2 million metric tons of methane per year,

which is equivalent to 51 million metric tons of carbon dioxide. Methane emissions from

Pabedana coal mines make up between 25 and 35 percent of anthropogenic methane

emissions in Iran. All coals contain methane, but the amount depends on the nature of the

coal. Pabedana coal mine produces 3- 7 % methane. More than 5% concentration of

methane causes inhalation problems. Generally, deeper coal seams have higher methane

content. Underground mines therefore are by far the largest source of coal mine methane

emissions. Most of the methane emitted from Pabedana mine escapes through ventilation

systems put in place for safety measures or through other shafts and portals. The remainder

is released during the handling and processing of the coal after it has been mined.

The second significant form of air pollution from coal mining is particulate matter

(PM) emissions. While methane emissions are largely from eastern underground mines,

PM emissions are particularly serious at western surface mines. Mining operations in the

arid, open, and frequently windy region creates a significant amount of particulate matter.

These wind-driven dust emissions occur during nearly every phase of coal strip mining in

the West, but the most significant sources are removal of the overburden through blasting

and use of draglines, truck haulage of the overburden and mined coal, road grading, and

wind erosion of reclaimed areas. The transportation trucks and equipment used in mining

are also a source of PM emissions.

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8.2.3 Pollution due to vehicular movement

The trains and trucks which are used for transporting coal from the Pabedana coal

mine are also a source of pollution of particulate matter that contributes two sorts of

pollutants: one is the exhaust of the vehicles with fine particles (~ 2.5 microns) and the

other is dust from the road, from fugitive emissions of dirt carried by all trucks. The truck

traffic from Pabedana Coal mine to Zarand coal washery will increase the air pollution

along the transport route. Heavy loads in trucks will also increase their stopping time. For

short distances, trucks play an important role in transporting the coal to a stop station

before the coal is shipped to coal washing plant.

8.2.4 Pollution of coal washery

Washing of coal has gained much more importance recently, as a result of the

increasing environmental concerns and to provide cleaner coal for subsequent use. Coal

washing processes have resulted in the generation of more and more finer particles as the

removal of pyrite and other mineral matter requires finer grinding. Efficient flotation,

which is based on the differences in the surface chemical characteristics of coal and

mineral particles, has become very important. Coal is a complex heterogeneous material

composed of a variety of organic constituents in different forms. Its surface properties,

such as wettability and floatability, can vary to a large extent due to its complex nature, as

well as alterations in-situ and through subsequent exposure to various environments.

In Zarand coal washing plant, as much as 7000 liter of water is consumed to

produce one ton of coal. In washing processes, waste materials are pumped to the tailing

pond (Akbar Abad tailing pond). Because of mixing of pond water with magnofluk

chemical the water of this pond contains lots of minerals and it is used as liquid manure for

the surrounding farms.

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In the washery plant, coal is transported by conveyor belt to the coal washing plant.

Initially water and the coal with diameter of less than 1mm enter to the pond (which is also

called as slush). In this pond, 2 liter of oil is added to each ton of coal (adding oil will

result in the production of more amount of coal). After this stage of flotation, small amount

of alcohol (about 40 ml of alcohol for each ton of coal) is added and it leads to the

formation of bubbles. These bubbles will float on the surface of the water because of their

low molecular weight and the coal particles will float to surface together with the bubbles

and they pass to the vacuum filter. In the vacuum filter coal is separated from the water and

then it enters the reservoir by suction power of about 1.5 atmospheres. A part of oil and

alcohol material enters the vacuum filters along with coal and finally these oil and alcohol

enter the tailing pond. Based on geochemical data, the amount of oil and grease within the

waste material is higher than the permissible limit. Zarand Coal washery produces large

volumes of tailings and solid wastes. Storage and handling of coal generates dust at rates

which is 3 kilograms per metric ton of coal mined, with the ambient dust concentration

ranging from 10 to 300 µg/m3 (above the background level) at the mine site.

8.2.5 Water pollution around coal washery

Raw coal will be invariably processed to remove noncombustible materials (up to

45% reduction in ash content) and inorganic sulfur (up to 25% reduction). Coal

beneficiation is based on wet physical processes such as gravity separation and flotation.

Beneficiation produces two types of waste: one is fine materials that are discharged as

slurry to a tailings pond, and the other is coarse material typically greater than 0.5

millimeters (mm) that is discharged away as a solid waste.

The quantity of tailings that can be stored in a dam of a given volume is dependent

on the density that can be achieved. The latter is influenced by the type of tailings, the

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method by which they are deposited, (viz., in water or subaerially), the drainage conditions

within the dam and evaporation.

Zarand Coal washing plant is one of the largest coal processing plants in Iran. It

provides coking concentrate for Eisfahan iron melting plant. Zarand coal washing plant

produces 4,50,000 tons/year waste materials. Flotation unit is one of the units of the plant

which produces most of the waste material. Wastes of the flotation unit are transferred by

pipe to tailings pond which is situated about 600 m west of the plant. Zarand coal washery

is located in the vicinity of Zarand city. Enormous quantity of water is required for coal

washing (Khoury 1981). Zarand coal washery utilizes groundwater for different washing

processes and as a consquence huge amount of coal fines is generated and constitute the

effluents. The amount of water used in each washery varies with the plant capacity. In

Zarand coal washery, every million ton of hourly capacity require 700-2000 gallons of

water per hour. On the basis of our survey and estimates, average water demand in the

washery reaches to 40-110 gallons/ton of feed coal and the average effluents discharge

varies from 70 m3 to 420 m3 to the tailings pond. All the washeries operating at present

fails to keep the exact record of process water and chemicals in the process plant, virtually

not maintaining the close water circuit conception. There occurs wide variation in

characteristics of coal due to supply of heterogeneous coal and even from the same coal

seam which creates imbalance in performance of equipment used. Thickeners will cause

blockage of overflow with subsequent loss of coal fines that is entries the effluents.

Finally, these waste materials are pumped to the tailing pond located at near Akbar Abad

village. Tailing pond occupies an area of 25 hectors and is 9m deep. (Fig. 8.1).

8.2.6 Road damage and public safety

Road damage can result from the transportation of coal from mines to coal

processing unit. Road damage from coal trucks is a concern in the study area. Overweight

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trucks are a contributing factor, especially in the vicinity of coal washery where coal trucks

sometimes exceed legal weight limits more than 10,000 pounds. Strict enforcement of legal

limits ensures public safety and reduces damage and costly repair to busy haul roads.

Fatalities have occurred on coal haul roads involving coal trucks, and at railway crossings

involving coal trains and thus, public safety is an issue.

8.2.7 Effect of coal gasification

Ground water pollution around coal gasification zones is mainly caused in one of

the following ways: dispersion and penetration of the pyrolysis products of the coal seam

to the surrounding rock layers, the emission and dispersion of high contaminants with gas

products after gasification and migration of residue by leaching and penetration of

groundwater. In addition, the escaped gases such as carbon dioxide, ammonia and sulfide

may change the pH value after being dissolved, which subsequently affect the demand for

chemical and biological oxygen content of groundwater.

8.2.8. Causes of the pollution from coal tailings

The pollution from coal tailings is mainly due to the existence of pollutants, large

quantities of tailings, oxidation and acidification, and spontaneous combustion.

8.2.8.1 Pollutants in coal tailings

Coal tailings are from coal mining and washing process, which includes the coal-

bearing rocks of roof and floor. The main mineral composition of coal tailins includes

kaolinite, quartz, as well as other components such as feldspar, calcite, siderite, pyrite and

illite. Coal tailings have a fixed carbon content of 56%-58%. There are number of toxic

elements in coal tailings, such as lead, cadmium, mercury, arsenic, chromium and sulfur.

Concentrations of trace elements in coal gangue are generally higher than those in raw

coals, and As, Hg, Cd, Pb, Cu, Zn concentrations are much higher than the crustal

abundance values. Trace elements could migrate to the surrounding environment, and

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extraction of leached amount increases with the decrease of pH, and its pollution is

becoming smaller with the increase of distance.

8.2.8.2 The dump of coal tailings on ground

Directly piled coal tailings on ground usually changes the regional landscape. Coal

tailings are mostly gray-black, it has become a marker of coal mine area. Bare and black

coal tailings have resulted in the serious impact on natural landscape of the mining area.

The pollutants in open-air coal tailings piles directly exposed to the wind and rain can

easily migrate and pollute the surrounding soil, water bodies and groundwater. Coal

tailings are easily weathered and oxidized, and it could cause spontaneous combustion and

explosion. Therefore, the exposed coal tailings piles are the main external causes of

pollution.

8.2.8.3 The oxidation of sulfur in coal tailings

The oxidation is the important cause of pollution. Studies showed that the acidity of

coal tailings are most serious pollution and most difficult to control (Akcil and Koldas

2006; Zhao et al. 2005). The spontaneous combustion of coal tailings, explosions,

landslides and pollution of soil and water are directly related to the acidity of coal tailings.

The acidity is mainly due to sulfur Holm et al. 2003; Hu et al. 2005), which could generate

acid mine drainage (AMD) as a result of oxidation, AMD may attain pH values of 2.0- 3.5

(Bi et al. 2003). In acidic conditions, the heavy metal activation and pollution of the

activity has been exacerbated. The process of sulfide oxidation also produces a lot of heat,

and can easily lead to spontaneous combustion of coal tailings, which inturn pollute the

environment and trigger explosions and environmental disasters. Therefore, the oxidation

of coal tailings is the main cause of acidic pollution, heavy metal activation, spontaneous

combustion, and explosion.

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Releases of AMD have low pH, high specific conductivity, high concentrations of

iron, aluminum, and manganese, and low concentrations of toxic heavy metals. Chemical,

biological and physical factors are important for determining the rate of acid generation;

physical factors, particularly the permeability of coal tailings piles, are particularly

important. Piles with high permeability have high oxygen ingress, which contributes to

higher chemical reaction rates, hence, higher temperatures and increased oxygen ingress

through convection. Bacteria like Acidithiobacillus ferrooxidans (eg. Thiobacillus

ferroxidans) involve oxidation of pyrite (FeS2); however, the bacterium may accelerate

oxidation of sulfides. It could be 106 times of normal chemical reaction. Therefore,

restraining the oxidation of pyrite.

8.2.8.4 Spontaneous combustion of coal tailings

The spontaneous combustion of coal tailings arising from oxidation is the main

cause for acid rain and the explosion disaster. The Oxidation of pyrite releases the heat

build up in the coal tailings, which could increase the rate of oxidation. As the tailings is

exposed to air, the pyrite in the tailings are also exposed to atmosphere, which makes air to

penetrate and provide oxygen for pyrite oxidation. According to statistics, the annual

spontaneous combustion of coal tailings, combustion emissions to the atmosphere with CO

=10.8 g, SO2 = 6.5 g, H2S and NO2 = 2 g per day per square meter. Soluble sulfate and

sulfuric acid not only affects the coal tailings, also result in the acidification of surrounding

water and soil environment and soil acidification, so it is difficult for vegetation to survive.

8.2.9 Pollutants migration

As shown in Fig.8.2, the pollution from coal tailings is mainly through the wind

and water. Wind carries the gaseous pollutants of the tailing to the atmosphere and soil.

Through the surface runoff, will pollutants and acidic water move to the vicinity of the soil

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and also infiltrate into the ground, which contaminate the groundwater. Therefore, the

degree of pollution is often associated with the distance and the wind direction.

Fig. 8.2: Pollutants migration from coal tailings.

8.2.10 In-situ control measures for coal tailings pollution

Many methods are in use to remove pollutants. Removal of carbon, desulfurization,

and removal of heavy metals required processing of the coal tailings, which involve high

costs. So pollution in-situ control is one of the most effective ways. Based on the analysis

of the causes of pollution, it could be concluded that exposure, oxidation and spontaneous

combustion of coal tailings are the main external causes of pollution. Therefore, in situ

control of pollution of coal refuse has to be taken up seriously by following appropriate

technology.

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Fig. 8.1: Photograph showing part of tailings pond and coal washery.

8.2.11 Effect of effluents of tailings on vegetation

Tailings pond water contains high concentration of TDS and variable amounts of

Na. Such waters can be used to irrigate salt-resistant crops like mustard, pistachio etc.,

(Fig. 8.3). These waters are not suitable for irrigating lands growing other crops.

Fig 8.3: Photographs show utilization of tailings water for growing pistachio trees.

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8.3 ASSESMENT OF HEAVY METALS DISTRIBUTION USING GIS

TECHNIQUES

Geographical Information System (GIS) which is a tool which allows synergism of

map data and tabular data in the most efficient manner. Now-a-days GIS is playing a vital

role to carrying out the interpretation and plotting of analytical data.

The data obtained by analysis is so voluminous and it is difficult to handle them on

paper, so to have proper arrangement and proper record we require the assistance of GIS

softwares as they help not only in the developmental planning but also in decision-making.

So not only we have proper record of information but also one can easily update the

information i.e. not possible manually as it become a tedious job, know that anthropogenic

activities are basically responsible for bringing heavy metals into our groundwater system.

The geochemical data plots of metals (Cu,Mn and Pb) are digitized through GIS software

and heavy metal concentration of surveyed area are also added to this analysis.

GIS maps are very helpful to decipher of the present groundwater bodies the

sources of heavy metals passing through industrial area, which in turn leads to their

adverse effect on different land units, like agriculture, urban areas, etc. The present data

can provide useful information for pollution control strategies and towns and village

located around the tailings pond.

Human activities is very much responsible for the sources of metal contamination

in the environment (eg., Chapman and Kimstach, 1992., Adriano, 1986). Heavy metal

toxicity disrupts natural ecosystem and affects the food chain leading to health problems in

humans and animals. Once metals are introduced into the environment, they undergo

several biological and chemical processes that lead to their distribution in environmental

compartments such as soils, sediments and surface and underground waters (eg., Beiger,

1986., Forstner and Wittmann, 1979., Misra et al., 1994., Herreweghe et al., 2002., Jung et

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al., 2002., Tahiri et al., 2005). Groundwater in several parts of the world are being polluted

by heavy metals which are released to the environment by anthropogenic sources (eg.,

industrial solid waste and effluents, fertilizers and pesticides, solid waste, urban sewage,

mine dumps, effluents from coal washeries etc.,).

As explained in section 7.4 in the groundwater of the study area two chemically

differing hydrochemical facies were identified which are designated as groundwater zone-

A and groundwater zone-B. Groundwater zone-B is polluted variant of groundwater zone-

A. The groundwater zone-B is being polluted with Ca2+, Mg2+, Na+ and SO42- rich

downward percolating water from coal washery tailings pond and soluble salts from other

anthropogenic inputs (fertilizers, pesticides, urban sewage, waste dumps etc.,).

To understand the source of heavy metals in groundwater of the study area, it is

necessary to measure the concentrations of heavy metals in groundwaters zone-A and B

and water from tailings pond. The obtained data will reveal the source of heavy metals in

groundwater of the study area. When the obtained data is compared with the permissible

limits of the toxic metals in natural waters provided by WHO(1993), quality of the

groundwater of the study area for drinking purposes can be evaluated from the point of

view of its heavy metals concentrations.

During the course present work, 11 water samples from groundwater zone-B and 8

water samples from coal washery tailings pond were analysed for As, Cd, Cr, Cu, Fe, Mn,

Ni, Pb and Zn. The analyses were carried out by ICP-MS, AA. The obtained results are

provided in table 8.1. Concentrations of all these heavy metals are expressed in µg/L. In

the following paragraphs concentrations of all heavy metals are in µg/L.

In the groundwater zone-A concentrations of As vary from below detection limits

(BDL) to 2.5., Cr from 7.3 to 11.6 (av.= 8.76)., Cu from 4 to 12.6 (av.= 9.39), Fe from

BDL to 320., Mn from 2.02 to 18.10 (av.= 5.76)., Ni from BDL to 3.4., Pb from 0.6 to 2.5

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(av.= 1.08) and Zn from 7.8 to 34.30 (av.= 22.81). Concentrations of Cd are found below

detection limits.

In the groundwater zone-B terrain concentration of As in water samples from 14

borewells is found below detection limits and in the remaining water samples from 5

borewells the concentrations of As vary from 1.6 to 2.1. Concentrations of Cd in water

samples from 5 borewells vary from 1.6 to 2.1 and in the remaining water samples from 14

borewells the concentrations of Cd are found below detection limits. Cr content in

groundwater zone-B varies from 7.00 to 30 (av.= 9.99)., Cu, from 10 to 726., Fe, <100 to

318., Mn from 9.15 to 400.5 (av.= 29.23). Concentrations of Ni are found below detection

limits. In the water from tailings pond, As content varies from BDL to 10., Cd content

from BDL to 1.0., Cr content from 6.4 to 9.0 (av.= 7.4)., Cu content from 8.3 to 23.0 (av.=

12.4)., Fe content from 1.3 to 17.0 (av.= 5.2) and Zn content from 11.9 to 474.0 (av.=

80.30).

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Table 8.1: Heavy metals concentration in groundwaters zone-A, B and Tailings pond.

Sample

No.

Al As Cd Cr Cu Fe Mn Ni Pb Zn

(µg/L) (µg/L) (µg/L) (µg/L) (µg/L) (µg/L) (µg/L) (µg/L) (µg/L) (µg/L)

Groundwater zone-A

W-1 34 2.1 BDL 8.5 12.6 295 7.51 2.3 2.5 34.3

W-2 107 1.8 BDL 8.5 7.8 275 18.1 2 1.3 9.7

W-3 60 1.5 BDL 9.2 5.5 75 3.41 1.8 0.8 8.8

W-4 25 1.4 BDL 9.7 4 87 2.02 2.2 0.5 13.3

W-5 26 1.3 BDL 11.6 4 123 2.36 2.6 0.9 110.1

W-26 28 BDL BDL 8.5 12 195 5.6 BDL 1.3 9.7

W-27 32 BDL BDL 7.4 12 BDL 3.2 2.7 0.7 8.6

W-28 41 BDL BDL 8.1 10 BDL 4.5 2.4 0.6 12.3

W-29 63 2.5 BDL 7.3 12 320 7.5 3.4 0.8 7.8

W-30 44 1.7 BDL 8.8 14 285 3.45 2.6 1.4 13.5

Average 46 1.23 BDL 8.76 9.39 165.50 5.765 2.20 1.08 22.81

Groundwater zone-B

W-6 135 BDL 1.9 30 726 318 62 BDL 1 23

W-7 137 BDL 1.8 15 744 247 19.4 BDL 10 26

W-8 29 BDL BDL 7 35 620 479 BDL 5 18

W-9 28 BDL BDL 7 18 178 359 BDL 4 31

W-10 38 BDL BDL 7 10 176 400.5 BDL 66 14

W-11 27 9 BDL 8 12 108 19.4 BDL 5 50

W-12 57 BDL BDL 7 12 BDL 149.5 BDL 17 36

W-13 41 BDL BDL 8 13 148 20.5 BDL 4 23

W-14 26 BDL BDL 7.5 12 165 136.25 BDL 8 34

W-15 47 BDL BDL 8.2 13 187 175.4 BDL 7 26

W-16 39 BDL BDL 7.3 11 BDL 70 BDL 7 18

W-17 94 BDL BDL 9.4 17 324 350.5 BDL 5 54

W-18 55 BDL BDL 8.6 15 245 247 BDL 54 15

W-19 21 1.9 BDL 9.4 26 281 41 BDL 4 21

W-20 31 2.7 BDL 6.8 24 243 96.3 BDL 19 9.5

W-21 22 3.9 1.6 12.3 342 308 68 BDL 6 39

W-22 102 1.9 1.7 14 415 86 62 BDL 4 24

W-23 76 BDL 2.1 10.5 325 129 55.1 BDL 11 64

W-24 36 BDL BDL 9.2 14 166 374.5 BDL 5 36

W-25 44 BDL BDL 7.6 11 148 9.15 BDL 3.2 23

Average 54.25 0.97 0.45 9.99 139.75 226.5 151.85 BDL 12.26 29.23

Tailings pond water

T-1 205 10.0 1.00 9.0 23.0 1136 623.10 12.0 17.0 474.0

T-2 91 5.0 BDL 8.0 11.0 425 550.70 8.0 6.0 30.0

T-3 73 BDL 0.80 8.0 14.0 735 602.00 9.0 5.0 30.0

T-4 238 BDL BDL 8.0 17.0 481 528.30 9.0 7.0 41.0

T-5 99 3.9 0.07 6.7 9.0 281 444.87 11.1 2.2 22.6

T-6 74 3.6 0.06 6.7 8.4 426 485.18 10.9 1.8 20.6

T-7 73 3.5 0.08 6.6 8.8 148 425.86 10.1 1.3 11.9

T-8 57 3.5 0.07 6.4 8.3 125 380.46 9.9 1.3 12.3

Average 114 3.7 0.26 7.4 12.4 470 505.06 10.0 5.2 80.3

WHO(1993) 200 10 3 5 2000 300 100 20 10 3000

Permissible upper limit

BDL: below detection limit

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Groundwater zone-B, in comparision with groundwater zone-A, consists of higher

concentrations of As, Cd, Cu, Fe, Mn, Pb and Zn. In comparision with water from tailings

pond, the groundwater zone-B consist of lower concentrations of Mn, Ni and Zn. Thus

groundwater zone-B, which is polluted than groundwater zone-A received the excess load

of Mn, Ni and Zn from downward percolating effluents from coal washery and the

additional concentrations As, Cd, Cr, Cu and Pb were possibly derived from other

anthropogenic sources (e.g., fertilizer, pesticides, urban sewage, waste dumps etc.,). In

water from tailings pond, Fe and Mn exceed the upper permissible limits of drinking water

(WHO, 1993) which can be due to chemical processing (magnetite used) in coal washing

plant.

WHO (1993) recommended the following upper permissible limits for the

concentrations of heavy metals in potable water (all values in µg/L),

Cd= 3., As= 50., Cu= 1500., Zn= 3000., Ni= 20., Pb= 20., Fe=300., Mn= 400 and Cr= 50.

Concentrations of heavy metals (viz., As, Cd, Cr, Cu, Fe, Mn, Ni, Pb and Zn) in

groundwaters zone-A and B are below the upper permissible limits of drinking water

(WHO, 1993). Hence, the concentrations of the above said heavy metals do not prohibit

the utilization of the groundwater for drinking purposes. However, other physico-chemical

parameters of groundwater of the study area have to be examined before recommending

the usage of the water for drinking purposes.

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Fig. 8.4: Spatial distribution of Cu, Mn and Pb in groundwater.