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CHAPT£RAW1 Introduction

Studies On Technology Oriented Methods For Water Contaminants And The Geochemical Influences On Contaminated Plume

CHAPTER 1

INTRODUCTION AND PRESENT STATUS OF

KNOWLEDGE

PREAMBLE

Water is one of the most essential needs of every living being. This need stems from

the fact that it is the water which causes and sustains any life form. The first living

creature of earth took birth in the water only and even today the maximum number

of life forms and their population is supported by water only. The terrestrial life

forms came on the earth in view of the fierce competition for the life supporting

parameters within the water. The most notable among such limiting parameters was

the sunlight and the nutrients. This shifting to the land provided the ample quantity

of sun light and the nutrients which resulted into their fast growth and today we can

find the various life forms even in the supposedly inhospitable areas of the earth.

Yet these life forms could not alter their great dependence on water. It is the reason

that every life form be it is human; plant or animal cannot keep themselves away

from water.

However the success of human race in the matters of survival has brought

about many problems in its wake. The biggest among them is the serious shortage of

usable water for various human purposes. This shortage led the man to explore a

particular source which other living beings can never do i.e. the exploitation of the

groundwater. The groundwater is termed as mother's milk also by some poetic

scientists. Yet the overexploitation of this scarce source is poisoning this precious

and sacred source. A large number of human problems could be attributed to the

misuse of this resource. Severe depletion of the groundwater and its contamination

are the two broad categories of the problem. This thesis is an attempt to study some

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Studies On Technology Oriented Methods For Water Contaminants And The Geochem/co/Jnfluences On Contaminated Plume

of the aspects of the groundwater contamination and what could be done by the

scientific community to reduce or eliminate such contaminations.

INTRODUCTION

When even a simple change occurs in the physical environment, its effects percolate

through a complex net-work of physical, biological and social interactions, that feed

back and feed forwards. Sometimes the immediate effect of a change is different

from the long term effect, sometimes the local changes may be different from the

region-wide alterations. These environmental changes entail unusually large spatial

scales. They also entail temporal scales that extend decades, or further, into the

future. Some entail irreversible changes. In case of groundwater the extent,

magnitude and the enormity of problem may sometimes defy the human cognition.

Reason for such behaviour lies in the intricacies associated with groundwater.

WHAT IS GROUND WATER AND HOW CAN IT BE POLLUTED?

Ground water is a resource found under the earth's surface. Most ground water

comes from rain and melting snow soaking into the ground. Water fills the spaces

between rocks and soils, making an "aquifer".

Ground water- its depth from the surface, quality for drinking water, and chance of

being polluted -varies from place to place. Generally, the deeper the well, the better

the ground water. The amount of new water flowing into the area also affects

ground water quality. Worldwide, according to a UNEP study (UNEP, 2003), over 2 B

people depend on aquifers for their drinking water. 40 per cent of the world's food

is produced by irrigated agriculture that relies largely on groundwater.

Ground water may contain some natural impurities or contaminants, even with no

human activity or pollution. Natural contaminants can come from many conditions

in the watershed or in the ground. Water moving through underground rocks and

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Studies On Technology Oriented Methods For Woter Contaminants And The Geochemkallnfluences On Contamlnoted Plume

soils may pick up magnesium, calcium and chlorides. In addition to natural

contaminants, ground water is often polluted by human activities such as

• Improper use of fertilizers, animal manures, herbicides, insecticides, and

pesticides

• Improperly built or poorly located and/or maintained septic systems for

household wastewater

• leaking or abandoned underground storage tanks and piping

• Storm-water drains that discharge chemicals to ground water

• Improper disposal or storage of wastes

• Chemical spills at local industrial sites

WHERE DO GROUND WATER POLLUTANTS COME FROM?

Understanding and spotting possible pollution sources is important. It's the first step

to safeguard drinking water for our family. Some threats come from nature.

Naturally occurring contaminants such as minerals can present a health risk. Other

potential sources come from past or present human activity - things that we do,

make, and use such as mining, farming and using chemicals. Some of these activities

may result in the pollution of the water we drink.

Metal Leaching and Acid Rock Drainage

Metals are a natural part of our environment. Life has evolved in this natural milieu

and requires that metals be present in appropriate levels and combinations.

Concentrations of metals that are too low can lead to health problems as a result of

nutrient deficiencies, whereas metal concentrations that are too high can be toxic to

plants, animals, and humans.

Metal leaching and acid generation are naturally occurring processes, which may

have negative impacts on the receiving environment. The environmental impact of

Ml/ ARD will depend on their magnitude, the sensitivity of the receiving

environment and the degree of neutralization, dilution and/or attenuation. Factors,

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Studies On Technology Oriented Methods For Water Contom/tJQnts And The Geochemical Influences On Contaminated Plume

which enhance metal leaching, include rapidly weathering metal-containing

minerals, drainage conditions that increase solubility and high flow rates through

contaminated materials. Elevated metal leaching is associated with acidic drainage

due to high metal solubility and sulphide weathering rates under acidic conditions

(Pons et al., 1982). For many rock types/environmental conditions, metal leaching

will only be significant if drainage pH drops below 5.5 or 6.

However, neutral pH drainage does not necessarily prevent metal leaching from

occurring in sufficient quantities to cause negative impacts. While the solubility of

aluminum, iron and copper is greatly reduced in neutral pH drainage, elements such

as antimony, arsenic, cadmium, molybdenum, selenium and zinc remain relatively

soluble and can occur in significantly high concentrations. Unlike ARD, neutral pH

metal leaching is generally only a concern if discharge is into a sensitive resource

and/or with little dilution. High concentrations of metals in neutral pH drainage

often result from localized relatively small zones of acidic weathering (William and

John, 1998). Human activity can greatly enhance acid generation and metal leaching.

Sulphide oxidation resulting in very acidic pH values is common worldwide in marine

soils drained for activities such as farming (Pons et al., 1982). ARD also occurs where

mineralized bedrock is excavated for use in construction. While sulphide mineral

oxidation results in acid generation, mining operations that expose sulphide-bearing

rock do not always create Ml/ ARD. In many cases, drainage alkalinity or other

minerals neutralize the acid. Acid neutralization and the consequent reduction in

metal solubility can occur immediately or at some downstream point. Acidity will

only persist if acid generation is faster than the rate of neutralization or continues

after the available neutralization is exhausted. Even if net acid conditions result,

ML/ARD may not be a concern if there is adequate neutralization or dilution prior to

discharge, or if insufficient water exists to transpc;>rt acid weathering products

(Morin and Hutt, 1997).

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WHAT HUMAN ACI!VmES CAN POUUTE GROUND WATERl

Bacteria and Nitrates

These pollutants are found in human and animal wastes. Septic tanks can cause

bacterial and nitrate pollution. So can large numbers of farm animals. Both septic

systems and animal manures must be carefully managed to prevent pollution.

Sanitary landfills and garbage dumps are also sources. Children and some adults are

at extra risk when exposed to water-born bacteria. These Include the elderly and

people whose immune systems are weak due to AIDS or treatments for cancer.

Fertilizers can add to nitrate problems. Nitrates cause a health threat in very young

infants called "blue baby" syndrome. This condition disrupts oxygen flow in the

blood (EPA, 2002).

Heavy Metals

Activities such as mining and construction can release large amounts of heavy

metals into nearby ground water sources. Some older fruit orchards may contain

high levels of arsenic, once used as a pesticide. At high levels, these metals pose a

health risk.

Fertilizers and Pesticides

Farmers use fertilizers and pesticides to promote growth and reduce insect damage.

These products are also used on golf courses and suburban lawns and gardens. The

chemicals in these products may end up in ground water. Such pollution depends on

the types and amounts of chemicals used and how they are applied. local

environmental conditions (soil types, seasonal snow and rainfall) also affect this

pollution. Many fertilizers contain forms of nitrogen that can break down into

harmful nitrates. This could add to other sources of nitrates mentioned above. Some

underground agricultural drainage systems collect fertilizers and pesticides. This

polluted water can pose problems to ground water and local streams and rivers. In

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Studies On Technology Oriented Methods For Water Contaminants And The Geochemical Influences On Contomlnated Plume

addition, chemicals used to treat buildings and homes for termites or other pests

may also pose a threat. Again, the possibility of problems depends on the amount

and kind of chemicals. The types of soil and the amount of water moving through

the soil also play a role (EPA, 2002).

Industrial Products and Wastes

Many harmful chemicals are used widely in local business and industry. These can

become drinking water pollutants if not well managed. The most common sources of

such problems are:

a} Leaking Underground Tanks & Piping

Petroleum products, chemicals, and wastes stored in underground storage tanks and

pipes may end up in the ground water. Tanks and piping leak if they are constructed

or installed improperly. Steel tanks and piping corrode with age. Tanks are often

found on farms. The possibility of leaking tanks is great on old, abandoned farm

sites. Farm tanks are exempt from the EPA rules for petroleum and chemical tanks.

b) Landfills and Waste Dumps

Modern landfills are designed to contain any leaking liquids. But floods can carry

them over the barriers. Older dumpsites may have a wide variety of pollutants that

can seep into ground water.

Household Wastes

Improper disposal of many common products can pollute ground water. These

include cleaning solvents, used motor oil, paints, and paint thinners. Even soaps and

detergents can harm drinking water. These are often a problem from faulty septic

tanks and septic leaching fields.

Water Treatment Chemicals

Improper handling or storage of water-well treatment chemicals (disinfectants,

corrosion inhibitors, etc.) close to a well can cause problems.

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METALS AND THE GROUNDWATER CONTAMINATION

Metals, radionuclides and other inorganic contaminants are among the most

prevalent forms of environmental contaminants, and their remediation in soils and

sediments is rather a difficult task (Cunningham et al., 1997). Sources of

anthropogenic metal contamination include smelting of metalliferous ore,

electroplating, gas exhaust, energy and fuel production, the application of fertilizers

and municipal sludges to land, and industrial manufacturing (Raskin et al., 1994;

Cunningham et al., 1997; Blaylock and Huang, 2000). Heavy metal contamination of

the biosphere has increased sharply since 1900 (Nriagu, 1979) and poses major

environmental and human health problems worldwide (Ensley, 2000). Unlike many

organic contaminants, most metals and radio nuclides cannot be eliminated from the

environment by chemical or biological transformation (Cunningham and Ow, 1996;

NRC, 1997). Although it may be possible to reduce the toxicity of certain metals by

influencing their speciation, they do not degrade and are persistent in the

environment (NRC, 1999). It is estimated that all over the world huge areas have

contamination due to metals. Similarly, large number of industrial facilities also has

problems with metals. This, in conjunction with a paucity of innovative approaches

to deal with metal problems, means that metal contamination represents a serious

environmental concern and a significant market opportunity for environmental

service companies (Vance, 2002).

Metals (or other inorganics) typically become groundwater problems under the

following situations:

• Activities associated with plating shops, where a wide variety of metals are

present at high concentrations in forms that are soluble.

• Sites with releases of radionucleides that, due to unique health risks, can

have significant impact at very low concentrations. In addition, the use of

chelating and complexing agents, making these contaminants mobile in the

environment, is common during processing of these materials.

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Studies On Technology Oriented Methods For Water Contaminants And The GeO(hemlca/lnfluences On Contaminated Plume

• Metals and high levels of inorganic Total Dissolved Solids (TDS) are associated

with leaks from sanitary, solid waste and hazardous waste landfills.

• High TDS impacts are also associated with salt storage areas and petroleum

production activities.

Innovation in the area of hydrocarbon remediation has been significant in the last

decade. Metals may only be mobilized or immobilized, unlike hydrocarbons they

cannot be degraded to less innocuous components (C02 and H20 for example). This

limited reactivity is one of the reasons that innovative remediation technology has

not been developed for soils or groundwater contaminated with metals. This will

likely change between now and the turn of the century.

Often metal contamination is confined to the upper few feet of soil beneath a

contaminated area. However, there are instances where metal contamination has

impacted groundwater. The purpose of this column is to discuss the

physical/chemical behavior of metals with a particular focus on conditions that make

metals mobile and thus able to impact groundwater. The next column will look at

remedial alternatives to metal contaminated groundwater. The important issue with

regards to metals is mobility. Specifically, under what conditions are metals mobile

and what conditions immobile? Metals in the environment can take four

fundamental forms: as raw metallic elements, as hydrated ionic salts, in covalently

bonded molecules termed inorganic complexes, or associated with a chelating

agent.

Elemental metals are not highly soluble under normal groundwater conditions.

Although, particles of elemental metal may cause a soil sample to fail a TClP test.

The mobility of metals as hydrated ionic salts is dependent first, upon which metallic

element is participating as the positively charged ion (termed the cation) and

secondly, which anion makes up the negatively charged component of the salt.

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Studies On Technology Oriented Methods For Water Contom/nonts And The Geochemical Influences On Contaminated Plume

Following is a brief summary of cationic/anionic solubility relationships:

1. Sodium (Na•), Potassium (K+) and Ammonium (NH/) are cations that form

salts which are all soluble.

2. All metal salts of the Nitrate (No3·), Nitrite (N02.), Acetate (C2H30 2.),

Permanganate (Mn04.), Perchlorate (Cio4·), and Chlorate (Cio3·) anions are

soluble.

3. All Chloride (Cr), Bromide (Br"), and Iodide (r) salts are soluble except those

of Lead (Pb2•), Silver (Ag•), and Mercury (Hg2

•).

4. All Sulfate (So/·) salts are soluble except those of Barium (Ba2•), Strontium

(Sr2•) and Lead (Pb2

•).

5. All Oxides (02.), Sulfides (S2

.) and Hydroxides (OH.) are insoluble except those

of Calcium (Ca2•), Barium (Ba2

•) and Strontium (Sr2•).

6. With the exception of Sodium (Na•), Potassium (K+) and Ammonium (NH/),

all metallic salts of the following anions are insoluble: Carbonate (C03 2");

Phosphate (Pol·), Sulfite (So/·), Borate (BO/), Fluoride (F) and Silicate

(SiO{).

A covalently bonded inorganic molecule that contains several atoms (one of more

of which are metal atoms) is termed an inorganic complex. Of particular interest and

environmental concern are a class of inorganic complexes termed oxyanions. These

are compounds composed of metal and oxygen atoms forming an entire molecule

(rather than just an isolated metal ion) that is capable of forming a hydrated

complex ion. These oxyanionic complexes are often soluble and more importantly

have physical/chemical qualities that make them valuable in various industrial

processes. In a modern industrial environment, metallic and metalloid oxyanions not

rare substances.

The most troublesome and the most common industrial oxyanion is chromate which

contains hexavalent chromium Cr(VI). The chromate molecule in turn forms an

extremely soluble anionically charged ion. Contributing to its high mobility in the

environment is a property of the chromate ion that allows it to be soluble over the

entire range of pH. This high degree of mobility, in conjunction with its common use,

16


and the fact that it is a known carcinogen, makes it one of the most common

problem metals found to contaminate groundwater (Vance, 2002).

The ability of chromium to form soluble oxyanionic complexes is not unique to it

only. There are other metals and metalloids that form inorganic complexes having

more or less the same solubility profiles. This includes: molybdenum, vanadium,

tungsten, arsenic, selenium and tellurium. These compounds are not commonly

utilized by our industrial society. Although, arsenic and selenium can have significant

groundwater impact around mining areas and irrigation complexes in the west.

Industrial chemistry often makes use of complexing agents with more that one point

of attachment to a central metal atom in a complex. This type of complexing agent is

termed a polydentate ligand or a chelating agent. Chelating agents form strong

bonds with metals and are in turn extremely soluble. EDTA (ethylenediaminetetra

acetic acid) is a commonly used chelating agent. Chelating agents are used in

industrial chemical systems with transition metals, heavy metals and radionucleides.

If released into the groundwater these metal bearing chelates are extremely mobile.

It should also be remembered that under some conditions metals in groundwater

can be mobile as colloidal sized particles, even though the metal is in an insoluble

form. Although not soluble, colloidal particles are so small they may approach the

size of ionized species within an order of magnitude. As such they are transportable

in the pore spaces of tight aquifer formations.

Lastly, it is important to understand that metals in groundwater will interact with

and adsorb to components of the soil matrix. Clays, other mineral components, and

carbonaceous material (especially humic and fulvic substances) can all act in this

manner. However in the case of metals, the dominant adsorptive component of the

soil matrix is iron. Iron oxides particularly of Ferric (Fe•3) have a very high adsorptive

affinity and total capacity for metal ions and oxyanionic metal complexes. This

capacity is so great that ferric hydroxide is often used in waste water treatment

systems to aid in the removal of soluble metallic species. Knowing the total iron

17


content of the soil matrix is paramount in understanding the fate and transport of

metals in groundwater.

CONTAMINANT PLUME

A release of leachate to the groundwater may present several risks to human health

and the environment. The release of hazardous and nonhazardous components of

leachate may render an aquifer unusable for drinking-water purposes and other

uses. leachate impacts to groundwater may also present a danger to the

environment and to aquatic species if the leachate-contaminated groundwater

plume discharges to wetlands or streams. Once leachate is formed and is released to

the groundwater environment, it will migrate downward through the unsaturated

zone until it eventually reaches the saturated zone. leachate then will follow the

hydraulic gradient of the groundwater system.

A number of forces may act on or react with the migrating leachate, resulting

in changes of chemistry and a general reduction of strength from the original

release. These forces are physical (filtration, sorption, advection, and dispersion),

chemical (oxidation-reduction, precipitation-dissolution, adsorption-desorption,

hydrolysis, and ion exchange), and biological (microbial degradation). The extent of

these reactions depends on the materials underlying the landfill, the hydraulics of

the groundwater system, and the chemistry of the leachate (Fred and Jones, 1991).

• Dissolved-metal contaminants in the plume move much more slowly than

the plume water. Neutralization reactions in the carbonate aquifer slows the

rate of advance of the plume's acidic front and most of the dissolved metals

to a about one seventh of the rate of advective ground water-flow (Brown et

al., 2000).

• The oxidation and precipitation of iron is driven by the reductive dissolution

of manganese oxide minerals. This reaction is a source of additional acidity to

the plume and a source of dissolved manganese, which travels ahead of the

plume's acidic front in neutralized ground water.

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Studies On Technology Oriented Methods For Woter Contaminants And The Geach~mlcallnfluences On Contaminated Plume

• The downgradient decrease in dissolved concentrations of copper, cobalt,

nickel, and zinc was the result of the pH-dependent adsorption to iron

hydroxides in the aquifer.

• The exchange of gases between the plume and atmosphere affects the

geochemistry of the shallow part of the plume. The major controls on

exchange of carbon dioxide and oxygen from the plume across the water

table are (1) neutralization reactions involving carbonate minerals and (2)

oxidation of dissolved iron near the water table as shown in (Fig.l). Continual

movement of perennial streamflow into and out of areas of shallow ground

water beneath the stream (hyporheic zone) increases the contact of

streamflow with sediment surfaces. The increased contact stimulates

precipitation of dissolved manganese as oxide coatings on streambed

sediment (Harvey and Wagner, 2000)

• Chemical reactions in the hyporheic zone are enhanced by the activity of

manganese oxidizing bacteria, which are active in the zone because of input

of oxygenated streamflow, shown in (Fig.l). Approximately 20 percent of the

total load of dissolved manganese flowing out of the drainage basin is

removed in this manner.

• Precipitation of manganese in the hyporheic zone reduces the movement of

dissolved nickel and cobalt because manganese oxides are an excellent

sorbent for those metals. The loads of dissolved nickel and cobalt flowing

from the basin were reduced because of hyporheic exchange (Kay, J., 2000).

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ATMOSPHERE

STREAM

HYPORHEI

DISSOLVED· IVETAL REMOVAL

GROUND WATER

OXYGEN THROUGH

INCREASED CONTACT OF STREAM WATER WITH SEDIMENT &

MICROBES

HIGER pH AND OXYGEN THAN GROUND WATER

LOWER pH AND OXYGEN, HIGHER DISSOLVED METAL CONCENTRATION

DISSOLVED· METAL REMOVAL

Fig.l Hyporheic zone water movement showing removing of dissolved metals

HEAVY METAL TOXICITY

The body has need for approximately 70 friendly trace element heavy metals, but

there are another 12 poisonous heavy metals, such as Lead, Mercury, Aluminum,

Arsenic, Cadmium, Nickel, etc., that act as poisonous interference to the enzyme

systems and metabolism of the body. No matter how many good health

supplements or procedures one takes, heavy metal overload will be a detriment to

the natural healing functions of the body. Some metals are naturally found in the

body and are essential to human health. Iron, for example, prevents anemia, and

zinc is a cofactor in over 100 enzyme reactions. Magnesium and copper are other

familiar metals that, in minute amounts, are necessary for proper metabolism to

occur. They normally occur at low concentrations and are known as trace metals; for

example, high levels of zinc can result in a deficiency of copper, another metal

required by the body. Heavy or toxic metals are trace metals that are at least five

times denser than water. As such, they are stable elements (meaning they cannot

be metabolized by the body) and bio-accumulative (passed up the food chain to

humans). These include: mercury, nickel, lead, arsenic, cadmium, aluminum,

20


platinum, and copper (metallic form versus ionic form). Heavy metals have no

function in the body and can be highly toxic. Heavy metals are taken into the body

via inhalation, ingestion, and skin absorption. If heavy metals enter and accumulate

in body tissue faster than the body's detoxification pathways can dispose of them, a

gradual buildup of these toxins will occur. High-concentration exposure is not

necessary to produce a state of toxicity in the body tissues and, over time, can reach

toxic concentration levels.

Symptoms

Toxic metals could be the cause of symptoms like memory loss, increased allergic

reactions, high blood pressure, depression, mood swings, irritability, poor

concentration, aggressive behavior, sleep disabilities, fatigue, speech disorders, high

blood pressure, cholesterol, triglycerides, vascular occlusion, neuropathy,

autoimmune diseases, and chronic fatigue (B-Focasd, 2000).

Mechanism

Heavy metals poison us by disrupting our cellular enzymes, which run on nutritional

minerals such as magnesium, zinc, and selenium. Toxic metals kick out the nutrients

and bind their receptor sites, causing diffuse symptoms by affecting nerves,

hormones, digestion, and immune function. The heavy metals most often implicated

in human poisoning are lead, mercury, arsenic, and cadmium. Some heavy metals,

such as zinc, copper, chromium, iron, and manganese, are required by the body in

small amounts, but these same elements can be toxic in larger quantities. Once in

the body, they compete with and displace essential minerals such as zinc, copper,

magnesium, and calcium, and interfere with organ system function. Toxic heavy

metals may lead to a decline in the mental, cognitive, and physical health of the

individual.

There seems to be a higher level of heavy metal toxicity in children. The

evidence suggests that some children build up more of these toxic metals because of

an inability to excrete them. When they become lodged in the brain the brain does

not function normally, causing autistic symptoms and learning disorders (B-Focasd,

2000).

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Studies On Technology Oriented Methods F~r Water Contaminants And The Geochemical Influences On Contaminated Plume

ATIENUATION OF POLLUTION

Fundamentally, the objective of any groundwater cleanup (remediation) is to

minimize the risk posed by contaminants to human health and the natural

environment. This is accomplished by reducing the contaminant concentrations to

acceptable levels or controlling the migration of contaminants to other sensitive

receptors. Due to their mobility in natural water ecosystems and their toxicity to

higher life forms, ground water contaminants like soluble organics, soluble metals

(e.g., arsenic, lead) and soluble radio-nuclides (e.g., tritium) in surface and

groundwater supplies have been prioritised as major contaminants in the

environment. Other examples include:

• shallow groundwater contaminated by hexavalent chromium Cr(VI)

from electroplating waste disposal;

• ferrous iron Fe( II) and toxic metals in acidic groundwater as a

consequence of sulphide mineral oxidation in mine milling wastes;

• nitrate contamination from septic and sewage lagoon systems; and,

• contamination by constituents such as chloride and sulphate, and

• organics such as toluene and organic acids, from domestic landfills.

Even if these contaminants are present in dilute, undetectable quantities, their

recalcitrance and consequent persistence in water bodies imply that through natural

processes such as biomagnification, concentrations may become elevated to such an

extent that they begin exhibiting toxic characteristics. These metals can either be

detected in their elemental state which implies that they are not subject to further

biodegradative processes or bound in various salt complexes. In either instance,

metal ions cannot be mineralised. Apart from environmental issues, technological

aspects of metal recovery from industrial waste waters must also be considered

(Wyatt, 1988). Metal resources are non-renewable and natural reserves are

becoming depleted. It is therefore imperative that those metals considered

environmentally hazardous, or which are of technological importance, strategic

significance or economic value, be removed/recovered at their source using

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Studies On Technology Oriented Methods For Water Contamlnont5 And The Geochemlcollnfluences On Contaminated Plume

appropriate treatment systems. Effluent treatment processes are designed to

ensure that when waste waters are discharged into natural water courses, any

adverse effects are reduced or prevented. The extent of any such effect will be a

function of the volume and composition of the influent waste water and the dilution

capacity of the receiving water. It is for this reason that similarly operated

processing facilities may be required to meet different effluent discharge standards

according to their location (Saunders, 1987). The impact of industry on water

sources is immense and it is only through promotion of good pollution prevention

practices that contamination and deterioration of these waters will decrease. It is

therefore the responsibility of various water authorities to inform industry of the

methods available to them and encourage implementation of such practices to

safeguard the water environment.

There are various technologies currently used for groundwater remediation

at contaminated sites that are discussed below. A remediation program will often

employ more than one technology to achieve the cleanup of a given site.

1. Natural attenuation

Application of natural attenuation of groundwater is similar to that of soil.

2. Oxygen enhanced biodegradation

This is an In-situ Oxygen enhanced biodegradation of the groundwater which

involves pumping air, ozone, hydrogen peroxide, or other oxygen sources through

injection wells to enhance aerobic degradation of organic contaminants. This

innovative technology can remove the following contaminats

• Non-halogenated volatiles and semi-volatiles, fuel hydrocarbons.

• Less effective for some halogenated volatiles and semi-volatiles, pesticides.

Advantages:

• Can be a permanent solution.

• Low capital costs.

• Regulatory and public acceptance is moderate to high.

23


Disadvantages:

• Not effective in low permeability, heterogeneous soils.

• High iron content can reduce hydrogen peroxide concentrations

• High 0/M costs.

3. Passive treatment walls

This is also an In-situ degradation method where a permeable treatment wall is

installed in front of a migrating contaminant plume, allowing the plume to passively

move through the wall. The contaminants are degraded by interaction with a

catalyst contained in the porous media of the wall. This innovative technology could

be utilized for the destruction of following contaminants (USEPA, 1994).

• halogenated volatiles and semi-volatiles, inorganics.

• less effective for some non-halogenated volatiles and semi-volatiles,

• fuel hydrocarbons.

Advantages:

• Effective for treating chlorinated hydrocarbons.

• Low 0/M costs.

Disadvantages:

• Applicable only in shallow aquifers with well established flow

direction.

• The wall's reactive media must be replaced on a regular basis.

• High capital costs.

4. Air sparging

This is an In-situ separation technique in which air is injected into the groundwater

through a network of injection wells creating a subsurface air stripping system that

separates contaminants from the groundwater through volatilization. Air sparging

must operate in unison with a soil vapour extraction system to capture the volatiles.

This innovative technology could be used for remediation for the following

contaminants (USEPA, 1994):

• Volatiles, fuel hydrocarbons.

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Studies On Technology Oriented Methods For Water Contaminants And The G~hemkallnfluenc:es On Contaminated Plume

Advantages:

• Low capital and low 0/M costs.


• Regulatory and public acceptance is high.

Disadvantages:

• Channeling of air flow can occur in layered and fractured terrains,

adversely affecting system performance.

• Not effective in low permeable soils.

5. Free product recovery

This is an Ex-situ removal technique where pumping or passive collection methods

are used to remove undissolved liquid phase organics from the subsurface. This

method is used primarily to extract light non-aqueous phase liquid hydrocarbons

(LNAPLHs) floating on the water table. This is a conventional technique used for the

following contaminants:

• Non-halogenated semi-volatiles, fuel hydrocarbons.

Advantages:

• Low capital and low 0/M costs.



• Effective for contaminants that float on water.

Disadvantages:

• Large draw down cones associated with pumping may spread the

contaminant to lower levels of soil in the saturated zone.

• If dense non-aqueous phase liquids (contaminants that sink) are

present, then pumping can make the problem worse.

• Reuse or disposal of the recovered free product is required.

• Dissolved plume requires treatment.

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Studies On Technology Oriented Methods For Water Contaminants And The Geochemical Influences On ContamJnoted Plume

6. Bioreadors

In this Ex-situ destruction technique a contaminated groundwater is extracted and

treated with microbes ex-situ in bioreactors. The biological systems in a bioreactor

may be suspended or attached. In suspended growth systems, groundwater is

circulated through activated sludge where suspended particles promote microbe

growth and aerobic degradation of contaminants. In attached growth systems

contaminant degradation takes place on an inert support matrix such as trickling

filters. This method may prove to be a better one for the following contaminants:

• Non-halogenated volatiles and semi-volatiles, fuel hydrocarbons.

• Less effective for some halogenated volatiles and semi-volatiles,

pesticides.

Advantages:


• Low 0/M costs.

• Regulatory and public acceptance is generally high.

Disadvantages:

• Metals may need to be removed prior to treatment.

• Precipitation of in organics (e.g. iron, calcium) may clog treatment systems.

• Solid residuals that settle out in sludge systems may require treatment and

disposal.

7. Air stripping

This conventional Ex-situ separation technique involves the extraction of

groundwater and the trickling of the water through a device that volatilizes

contaminants by inducing air counter-current to the water. Types of aeration

methods include packed towers, diffused aeration, tray aeration, and spray aeration.

The following contaminants may be degraded by this method.

• Volatiles.

• Less effective for some semi-volatiles, fuel hydrocarbons.

Advantages:

• Treats high concentrations.

26




Disadvantages:

• Off-gases and residual liquids may require treatment.

• Regulatory and public acceptance is low.

• lnorganics can clog the stripping column packing material which then

requires washing or replacement.

• May require further treatment, by carbon adsorption on activated carbon,

for

example, to meet drinking water standards.

8. Carbon adsorption

Carbon adsorption is an ex-situ process, which involves pumping, contaminated

groundwater through a series of activated carbon cells. The activated carbon

adsorbs dissolved organic contaminants from the groundwater. This conventional

method could be a good one for the remediation of following contaminants:

• Semi-volatiles.

• Less effective for some halogenated volatiles, fuel hydrocarbons,

pesticides, inorganics.

Advantages:




Disadvantages:

• Activated carbon requires periodic regeneration or disposal.

• Metals can clog the activated carbon.

• High 0/M costs.

• Too expensive for high concentration contaminants, therefore, often

used after contaminants are first reduced by air stripping.

27

Studies On Technology Oriented Methods For Water Contaminants And The Geochemlcollnfluences On Contornlnated Plume

9. UV oxidation

UV oxidation is an ex-situ process where contaminated groundwater is exposed to

ultraviolet radiation to destroy organic contaminants. Ozone or hydrogen peroxide

are commonly used to enhance the oxidation and destruction of the contaminant.

Off-gases are treated by an ozone destruction unit. This innovative method could be

used for the following contaminants:

• Halogenated volatiles and semi-volatiles, pesticides.

• Less effective for some non-halogenated volatiles, fuel hydrocarbons.

Advantages:

• No residual produced.

• Low 0/M costs.

Disadvantages

• lnorganics and naturally occurring soil organics can adversely affect

system performance.


10. Slurry walls

A vertically excavated trench is filled with a bentonite-water slurry to form an

impermeable subsurface barrier. These walls are used to contain migrating

contaminant plumes that pose an imminent threat to surrounding receptors. They

are also used to redirect a contaminant plume to targeted extraction zones. This

method can be beneficial for all types of the contaminants:

Advantages:

• Usually a rapid method of dealing with migrating contaminants.

• Relatively simple to implement.

• Low 0/M costs.

Disadvantages:

• Full contaminant containment is difficult in high groundwater flow

regimes. • Bentonite may be degraded by some organic compounds and acid,

base, and salt solutions.

• Regulatory and public acceptance is low.


28

Studies On Technology Oriented Methods Ftx Water Contaminants And The Geochemlcailnfluences On Contaminated Plume

11. Permeability enhanced groundwater extra dian

This is a In-situ technique of remediation where fractures are induced into

impermeable sediments or bedrock to improve permeability and the pumping

efficiency of extraction wells. This is accomplished by injecting pressurized water

(hydro-fracturing) through injection wells or by blasting a linear zone. This method

may be helpful for the following contaminants:

• All dissolved or light non-aqueous phase liquid contaminants (less dense than

water).

• More caution required for dense non-aqueous phase liquid contaminants

(heavier than· water).

Advantages:

• Effective for groundwater extraction in highly impermeable materials

such as bedrock.

Disadvantages:

• Care must be taken not to fracture an underlying or adjacent

uncontaminated zone into which contaminants could spread.

• Blasting has high capital costs. Monitoring of groundwater capture

effectiveness will increase costs.

• Regulatory and public acceptance is low for blasting methods.

12. Chemical and physical treatment processes

Conventional chemical {precipitation/neutralisation) or physical (ion exchange,

activated carbon sorption and membrane technology) treatment techniques are

inherently problematic in their application to metal-bearing waste streams.

Chemical treatment methods can prove costly to the user as the active agent cannot

be recovered for reuse in successive treatment cycles. Also, the end product is

usually a low-volume highly concentrated metal bearing sludge that is difficult to

dewater and dispose of. After treatment, total dissolved solids (TDS) values of the

waste-water may still be unacceptably high due to the poor compact ion properties

of the sludge cake. Addition of natural or synthetic polyelectrolyte/flocculant may be

29

Studies On Technology Oriented Methods For Water Contaminants And The G~hemkallnfluences On Contaminated Plume

required to assist with precipitation. Introduction of chemicals increases the

conductivity/salinity of water through the production of soluble sulphates and

chlorides (Kuyucak, 1997).

TRADITIONAL METAL REMOVAL PROCESSES

Hydroxide Precipitation

Traditionally, dissolved metals have been removed from water by the process of

hydroxide precipitation. Since most metal hydroxides are insoluble, it would appear

easy to remove metals by this process. The main problems associated with this

process are that hydroxides of different metals have different pH levels for minimum

solubility and the reactions are of an equilibrium type, i.e., some of the metal

hydroxide will disassociate with the resulting metal ions going back into solution

(Brady and Humiston, 1986). The most common reagents used for hydroxide

precipitation are caustic soda, lime, and magnesium hydroxide.

Sulfide precipitation

Soluble metals can also be removed by precipitating them as a sulfide by the

addition of sodium sulfide to the solution. This method yields more complete metal

removal than hydroxide precipitation but can easily leave toxic sulfides in solution.

This method is much more expensive than hydroxide precipitation since the excess

sulfides are usually regulated and the resulting sludge may be difficult to landfill

(Solomon, 1992). Therefore, it is not as widely used as hydroxide precipitation.

MODERN METAL REMOVAL PROCESSES

Carbamates

Carbamates are chemical reducing agents that can be obtained as either sodium

dimethyldithiocarbamate or sodium diethyldithiocarbamate. Carbamate

precipitation is again an equilibrium reaction that does not go to completion. Metal

residuals of 1.0- 1.5 mgl·1 can usually be obtained. Carbamates are not effective at

acidic pH levels and are not always effective at treating chelated wastes (Hill, 1984).

30

Studies On Technology Oriented Methods For Water Contaminants And Th~ GeocMmlcallnfluen~s On Contaminated Plume

Sodium Borohydride

Sodium borohydride is an extremely strong reducing agent and can reduce both

chelated and non chelated metals. This process has the advantage of producing the

least amount of sludge of any process but it has a number of disadvantages that

almost always preclude its use in an efficient and cost effective system. A major

disadvantage, is that unless the liquid is removed from the sludge immediately,

metals tend to go back into solution with the water. Another problem is that pH

control is critical. Explosive hydrogen gas is evolved at acidic pH values. High cost of

this reagent has also been a problem, and as a result, it has been very difficult to

justify its use.

Organometallic Precipitation

In 1994 Steve Holtzman, pioneered a new more environmentally responsible

method of removing heavy metals. This process revolves around the formation of

insoluble organometallic compounds formed by reacting metal bearing wastes with

a proprietary organic agent. By forming specific types of insoluble organometallic

compounds, all regulated metals can be reduced to non-detectable levels. The

process is easily controlled with an inexpensive ORP controller and can adapt to

changing levels of contaminants in the waste stream influent.

13. Biosorption of inorganic contaminants

Biological methods of metal recovery, termed biosorption, have been suggested as

cheaper, more effective alternatives to existing treatment techniques. Biosorption

entails the use of either living or dead micro-organisms and/or their derivatives

which complex metal ions using ligands or functional groups situated on the outer

surface of the cell (Bolton and Gorby, 1995). This phenomenon has been directly

compared with chemical ion-exchange processes (Chang and Hong, 1994). The

process requires neither an active membrane transport mechanism nor metabolic

energy in order to function and is controlled in a non-directed physiochemical

reaction (Gadd, 1988; 1992). Certain biomass types are evidently more suitable than

others to a specific application. The affinity that a biosorbent material exhibits for a

specific metal cation will dictate the practicality of its implementation for

31

Studies On Technology Oriented Methods For Water Contaminants And Th~ G~och~mlcallnf1umus On Contomlnated Plume

remediation of a particular waste stream. Once laboratory trials are complete and a

potential biosorbent has shown the ability to adsorb and sequester the required

metal ions from solution, several questions need to be resolved in order to assist the

decision concerning its pilot-scale or industrial application.

There are basically two categories of industrial waste liquors that will require

treatment prior to discharge: large volumes bearing low concentrations of metal

contaminants (<100 mgl·1, i.e. mining waste water, and conversely, small volumes

characterized by high TDS values, i.e. metal plating liquors. In the first instance, one

would expect to employ a biosorbent exhibiting high affinity for the metal/s

concerned (Volesky, 1987). In the latter case, the active material should possess high

biosorptive capacity values to ensure saturation of biomass binding sites doesnot

occur prior to cessation of the treatment process (Volesky, 1987).

The use of non-living biomaterials as metal-binding compounds has the advantage of

not being affected by high levels of contamination. Moreover, they require

minimum care and maintenance and can be obtained more cheaply. Biosorption is

an emerging technique for metal sequestration. Nonliving biomass can be

regenerated and reused for many cycles. . The strong metal-binding ability of

biomass has attracted much attention in the fields of wastewater treatment and

environmental remediation contaminated by toxic heavy metals.

NATURAL BY PRODUCTS

In addtion to use of wild and cultivated species besides cell cultures, a wide variety

of agricultural and forestry by products have been used as biosorbents of toxic

metals in a bid to develop biofilters for specific applications. i.e.: i) Cotton - Hg;

Groundnut skins- Cu; Tree Bark (Pinus, Acacia etc.)- variety of metals; Agrowaste -

variery of metals; waste tea leaves- Pb, Cd, and Zn; Pinus radiata -U; Apple waste -

Variety of metals; Cellulose - Variety of metals; Rice hulls - Variety of metals;

Exhausted coffee grounds- Hg; Pinus pinaster bark- Zn, Cu, Pb. Saw mill dust (wood

waste)- Cr; Freshwater green algae - variety of metals; Marine algae- Pb, Ni; ii)

Sphagnum (moss peat) - Cr(VI); iii) Immobilized Aspergillus niger, A. oryzae - Cd, Cu,

Pb, and Ni ; Olive mill waste Olea europea Cr, Ni, Pb, Cd, and Zn, Cu and Ni;

---- -------------------------------32

Studies On Technology Oriented Methods For Water Contaminants And The Geochemlcoltnjfuences On Contaminated Plume

Streptomyces rimosus (bacteria); Saccharomyces cerevisiae (yeast); Penicillium

chrysogenum (fungi), Fuscus vesiculosus and Ascophyllum nodosum (marine algae)

Zn, Cu andNi; Phanerochaete chrysosporium, P. versicolar- Pb, Ni, Cr, Cd, Cu; Pinus

radiata - U; Immobilized Pseudomonas putida 5-X and Aspergillus niger, Mucor

rouxxi - Cu; Actionomycetes, Aspergillus niger, A.oryzae, Rhizopus arrhizus, R.

nigricans- Cd; Rhizopus arrhizus - Cr(VI), Pb; Rhizopus nigricans, Phanarochaete

chrysogenum -Pb; Aspergillus niger and Rhizopus arrhizus - Ni (Prasad and Freitas,

2000).

BIOSORPTION: A SOLUTION TO POLLUTION?

The knowledge of matter, how it is formed and how it can be modified was a puzzle

for people for a long time ever since someone took a piece of clay and shaped it into

a pot that could be hardened by fire. That pot, once fired, would retain liquid and

resist deformation even when it was set among hot coals. This happened in the

Neolithic, which started approximately 9,000 BC. Some 7,000 years later, Greek

philosophers speculated that all matter consisted of minute, indivisible particles of

the same basic substance. Those early attempts to understand the nature of

material things can be taken as the beginning of materials science. It was not until

the 19th century that chemistry and physics began to support the empirical efforts

of artisans and engineers with the development of applicable theories and novel

analytical tools. The key contribution of science was, understanding the coupling of

external properties of materials to their internal structure. Modern industry is, to a

large degree, responsible for contamination of the environment. Lakes, rivers and

oceans are being overwhelmed with bacteria and waste matter. Among toxic

substances reaching hazardous levels are heavy metals.

Some inland water bodies in Europe and America are closed for fishing.

Newspapers are full with reports of frequent ecological disasters in marine

environments. In Northern Brazil, fish from fresh waters are contaminated with

mercury as a result of ruthless, illegal, gold extraction. It was only in the 1990s that a

new scientific area developed that could help to recover heavy metals: biosorption.

The first reports described how abundant biological materials could be used to

33

Studies On Technology Oriented Methods For Water Contaminants And The Geothemlcallnfluences On Contaminated Plume

remove, at very low cost, even small amounts of toxic heavy metals from industrial

effluents. Metal-sequestering properties of non-viable biomass provide a basis for a

new approach to remove heavy metals when they occur at low concentrations. Note

that metals can be removed from solution only when they are appropriately

immobilized, the procedure of metal removal from aqueous solutions often leading

to effectively concentrating the metal. That aspect of biosorption makes the

eventual recovery of this waste metal easier and economical.

Many scientific studies are currently under way and contributions to welfare are

welcome in this world which grows each second and which needs to be in

equilibrium with so much progress. Some pollution seems inevitable, and one can

wonder what one should do to minimize it? Human populations need methods and

technologies to clean waters and diminish the environmental dangers related to

progress. Biosorption can be a solution to clean the environment contaminated by

heavy metals. When matter was first tamed, nobody could foresee how many

problems humans would have to face in the future.

To solve the water pollution problem by toxic heavy metal

contamination resulting from humans technological activities has for long presented

a challenge. Biosorption can be a part of the solution. Some types of biosorbents

such as seaweeds, molds, yeasts, bacteria or crab shells are examples of biomass

tested for metal biosorption with very encouraging results. The uptake of heavy

metals by biomass can in some cases reach up to 50% of the biomass dry weight.

New biosorbents can be manipulated for better efficiency and multiple re-use to

increase their economic attractiveness.

Various elements are being studied in this thesis for the bioremediation from the

aqueous solution, an elaborate study of those individual elements are been

discussed here.

34

CADMIUM

Cadmium is a naturally occurring metallic element, one of the components of the

earth's crust and present everywhere in our environment. Its presence results

mainly from gradual phenomena, such as rock erosion and abrasion, and of singular

occurrences such as volcanic eruptions. The natural level of cadmium in the

environment has been given in Tablel. The element's existence was revealed in

1817 and it owes its name to "cadmia fornacum", the "zinc flowers" which formed

on the walls of zinc distillation furnaces. Its industrial applications were developed

particularly during the first half of the 20th century, based on its unique chemical

and physical properties.

Table 1. Natural cadmium levels in the environment

Atmosphere 0.0001x10-6 - 0.005x10'6 mgl'1

Earth's crust 00.1- 0.5 j.lg g'1

Marine sediment - 1 j.lg g·l

Sea water -o.oo1 mgL-1

Even though the average cadmium concentration in the earth's crust is generally

placed between 0.1 and 0.5 11g g-1, much higher levels may accumulate in

sedimentary rocks, and marine phosphates and phosphorites have been reported to

contain levels as high as 500 11g g·1 (Cook and Morrow, 1995; WHO, 1992).

Weathering and erosion of parent rocks result in the transport by rivers of large

quantities, recently estimated at 15,000 metric tonnes (mt) per annum, of cadmium

to the world's oceans (WHO, 1992; OCED, 1994). Volcanic activity is also a major

natural source of cadmium release to the atmosphere, and estimates on the amount

have been placed as high as 820 mt per year (WHO, 1992; OCED, 1994; Nriagu, 1980;

Nriagu, 1989). Forest fires have also been reported as a natural source of cadmium

air emissions, with estimates from 1 to 70 mt emitted to the atmosphere each year

(Nriagu, 1980).

35

ANTHROPOGENIC SOURCES OF CADMIUM EMISSIONS TO AIR, WATER AND SOIL

Industrial and municipal wastes are a major source of cadmium pollution. Heavily

industrialized cities, especially those with nickel or copper smelters have the highest

concentrations of cadmium in the air {Health and Welfare Canada, 1992). Sewage

sludge can also contribute high amounts of cadmium, as well as other toxins such as

mercury and PCBs. These wastes come mainly from industrial effluents {Health and

Welfare Canada, 1992). Solid waste disposal and the application of municipal

sewage sludge on land are two sources. Another source is phosphate fertilizers,

which often have very high cadmium content. The percentage emission of cadmium

in the environment is shown in (Fig.2). Cigarette smoke most likely constitutes the

largest source of exposure for Canadians. The average non-smoking adult may

accumulate as much as 50 mg of cadmium over a lifetime, with this toxin

accumulating in kidney tissue. Cadmium, the most voluminous metal found in cured

tobacco is sprayed on the tobacco plant as a fungicide. A residual concentration of

cadmium in each cigarette averages 1.4 11g {Utell and Samet, 1995). One pack of

cigarettes deposits at least 4 11g of cadmium into the lungs (Casdorph and Walker,

1994).

Cadmium emissions to air arise, in decreasing order of importance,

from the combustion of fossil fuels, iron and steel production, non-ferrous metals

production and municipal solid waste combustion (Cook and Morrow, 1995; ERL,

1990; Jackson and Gillivray, 1993, Jones et al., 1993; Van Assche and Ciarletta, 1992).

In the second case, inputs to non-agricultural soils arise mainly from the iron and

steel industry, non-ferrous metals production, fossil fuel combustion, and cement.

manufacture (OCED, 1994; ERL, 1990; Jackson and MacGillivray, 1993). In the case of

cadmium present in controlled landfills, these amounts can arise from disposal of

spent cadmium-containing products, non-cadmium containing products which may

contain cadmium impurities, and naturally-occurring wastes such as grass, food and

soil which inherently contain trace levels of cadmium (Chandler, 1996). Cadmium

input to agricultural soils is of far greater relevance to human health than cadmium

input to non-agricultural soils, and input to controlled landfalls is of even less

importance because cadmium is largely immobilised in controlled landfills. For

example, numerous studies of the leachate from municipal solid waste landfalls has

36

Studies On Technology Oriented Methods For Water Contaminants And The Geochemical Influences On Contamfnated Plume

conclusively demonstrated that, even after long periods of time, the leachate from

these landfills contains only very low cadmium levels, sufficiently low enough to

meet the world's cadmium drinking water standards (Eggenberger and Waber, 1998;

NUS, 1987).

6%

• Phosphate fertilizer • Non ferrous • CD application El Natural

' 2%2% 8%

42%

o Combustion of fossil fuels o Iron and steel lllllCement lliJ Incineration

Fig. 2 Sources of human exposure to cadmium

CADMIUM APPLICATIONS

Cadmium is intentionally added to six major classes of products where it imparts

distinct performance advantages and is present as an impurity in five major classes

of products where its presence is regarded as an environmental disadvantage but

which generally does not affect the performance of the product. The major

intentional uses of cadmium are Ni-Cd batteries, cadmium pigments, cadmium

stabilisers, cadmium coatings, cadmium alloys and cadmium electronic compounds

such as cadmium telluride (CdTe) as shown in (Fig.3). The major classes of products

where cadmium is present as an impurity are non-ferrous metals (zinc, lead and

37

Studies On Technology Oriented Meth d f w o s or ater Contaminants And The Geochemical Influences On Contam(nated Plume

copper), iron and steel, fossil fuels (coal, oil, gas, peat and wood), cement, and

phosphate fertilisers (Cook and Morrow 1995).

8% 2%

•·Batteries D Pigments • Stabilizers D Coatings • Alloys and others

Fig. 3 Cadmium consumption in the world

Nickel-Cadmium Batteries

Cadmium hydroxide is utilised as one of the two principal electrode materials in Ni·

Cd batteries which have extensive applications in the railroad and aircraft industry

for starting and emergency power and in consumer applications such as cordless

power tools, cellular telephones, camcorders, portable computers, portable

household appliances and toys. Ni-Cd batteries are cost-effective well suited for high

power applications, and have high cycle lives and excellent low temperature and

high temperature performance relative to other battery chemistries (Morrow and

Keating 1997).

Cadmium Pigments

Cadmium sulphide and cadmium sulphoselenide are utilised as bright yellow to deep

red pigments in plastics, ceramics, glasses, enamels and artists colours. They are well

known for their ability to withstand high temperature and high pressure without

38

Studies On Technology Oriented Methods Ftx Water Contaminants And Th~ Geochemical Influences On Contaminated Plume

chalking or fading, and therefore are used in applications where high temperature or

high pressure processing is required (Cook 1994).

Cadmium Stabilizers

Cadmium-bearing stabilisers retard the degradation processes in polyvinylchloride

(PVC) which occur upon exposure to heat and ultraviolet light These stabilisers

contain organic cadmium salts, usually carboxylates such as cadmium laurate or

cadmium stearate, which are incorporated into PVC before processing and which

arrest any degradation reactions during subsequent processing and ensure a long

service life (Cadmium Association and Cadmium Council1991).

Cadmium Coatings

Cadmium coatings are utilised on steel, aluminium, and certain other non-ferrous

metal fasteners and moving parts to provide the best available combination of

corrosion resistance, particularly in salt and alkali media, and lubricity or low

coefficient of friction. They are also employed in many electrical or electronic

applications where a good combination of corrosion resistance and low electrical

resistivity are required. In addition, cadmium coatings exhibit excellent plating

characteristics on a wide variety of substrates, have good galvanic comparability

with aluminium, and are readily solderable (Morrow 1996).

Alloys and Minor Uses

Cadmium alloys include (a) electrical conductivity alloys, (b) heat conductivity alloys,

and (c) electrical contact alloys. Other minor uses of cadmium include cadmium

telluride and cadmium sulphide in solar cells, and other semiconducting cadmium

compounds in a variety of electronic applications (Cadmium Association and

Cadmium Council1991).

Food content

Foods found to be highest in cadmium are: organ meat (liver, kidneys), wheat and

bran cereals, potato chips and peanut butter although the form of cadmium found in

these foods is not thought to be readily absorbable in humans. A diet survey of

39

Studies On Technology Oriented Methods For Water Contaminants And The Geochemical lnPuences On Contaminated Plume

anglers and hunters found that eating fish and venison (deer meat) did increase

blood cadmium levels; however, the factor that contributed towards even greater

blood cadmium levels was smoking cigarettes {Cole and Kearney, 1997). For the

general world population, average daily cadmium intake, from all sources, is in the

range of 10-25 l!g per day and has decreased steadily over the past 20 years. Goyer,

a research scientist who has been monitoring cadmium content in food, reports a

slow but steady increase in concentrations of cadmium in vegetables over the years.

This increase is most likely the result of the growing agricultural use of this metal

(Goyer, 1996).

Cadmium in water

The average cadmium content in the world's oceans has variously been reported as

low as <5 ngl-1 (WHO, 1992) and 5-20 ngl"1 (OCED, 1994; Jensen and Bra

Rasmussen, 1992) to as high as 110 ngl"1 (CRC, 1996), 100 ngl"1 (Cook and Morrow,

1995) and 10 to 100 ngL-1 (Eiinder, 1985). Higher levels have been noted around

certain coastal areas (Eiinder, 1985) and variations of cadmium concentration with

the ocean depth, presumably due to patterns of nutrient concentrations, have also

been measured. Even greater variations are quoted for the cadmium contents of

rainwater, fresh waters, and surface waters in urban and industrialised areas. Levels

from 10 ngl-1 to 4000 ngl-1 have been quoted in the literature depending on specific

location and whether or not total cadmium or dissolved cadmium is measured

(Eiinder, 1985; WHO, 1992; OCED, 1994).

Cadmium is a natural, usually minor constituent of surface and

groundwater. It may exist in water as the hydrated ion, as inorganic complexes such

as carbonates, hydroxides, chlorides or sulphates, or as organic complexes with

humic acids. Cadmium may enter aquatic systems through weathering and erosion

of soils and bedrock, atmospheric deposition direct discharge from industrial

operations, leakage from landfalls and contaminated sites, and the dispersive use of

sludge and fertilisers in agriculture. Much of the cadmium entering fresh waters

from industrial sources may be rapidly adsorbed by particulate matter, and thus

sediment may be a significant sink for cadmium emitted to the aquatic environment

40

Studies On Technology Oriented Methods for Water Contaminants And The Geochemlc:ollnf/uen«S On Contaminated Plume

(WHO, 1992). Some data shows that recent sediments in lakes and streams range

from 0.2 to 0.9 mgl·1 in contrast to the levels of generally less than 0. 1 mgl·1 cited

above for fresh waters (Cook and Morrow, 1995). Partitioning of cadmium between

the adsorbed-in-sediment state and dissolved-in-water state is therefore an

important factor in whether cadmium emitted to waters is or is not available to

enter the food chain and affect human health.

Rivers containing excess cadmium can contaminate surrounding land,

either through irrigation for agricultural purposes, dumping of dredged sediments or

flooding. It has also been demonstrated that rivers can transport cadmium for

considerable distances, up to 50 km, from the source (WHO, 1992).

HEALTH EFFECTS

It has been well established that excess cadmium exposure produces adverse health

effects on human beings. For virtually all chemicals, adverse health effects are noted

at sufficiently high total exposures. For certain elements such as copper and zinc

which are essential to human life, a deficiency as well as an excess can cause

adverse health effects. Cadmium is not regarded as essential to human life. The

relevant questions with regard to cadmium exposure are the total exposure levels

and the principal factors which determine the levels of cadmium exposure and the

adsorption rate of the ingested/inhaled cadmium by the individual, in other words,

the pathways by which cadmium enters the food chain, the principal pathway of

cadmium exposure for most human beings.

Human Intake of Cadmium

Humans normally absorb cadmium into the body either by ingestion or inhalation. It

is widely accepted (WHO, 1992; ATSDR, 1997) that approximately 2% to 6% of the

cadmium ingested is actually taken up into the body. Much of the cadmium which

enters the body by ingestion comes from terrestrial foods. This is to say, from plants

grown in soil or meat from animals which have ingested plants grown in soil. Thus,

directly or indirectly, it is the cadmium present in the soil and the transfer of this

~------------------------

41

Studies On Technology Oriented Methods For Water Contaminants And The Geochemlcollnfiuences On Contomlnat<M Plume

cadmium to food plants together with the cadmium deposited out of the

atmosphere on edible plant parts which establishes the vast majority of human

cadmium intake, Some have estimated that 98% of the ingested cadmium comes

from terrestrial foods, while only 1% comes from aquatic foods such as fish and

shellfish, and 1% arises from cadmium in drinking water (Van Assche 1998). Because

of cadmium's high volatility, this metal is particularly hazardous for welders

(Shannon, 1998). The tolerable daily cadmium intake established by the World

Health Organization (WHO) is 60 llg per day for adult women and 70 llg per day for

adult men. The analysis acknowledges that most human cadmium exposure comes

from ingestion of food, and most of that arises from the uptake of cadmium by

plants from fertilisers, sewage sludge, manure and atmospheric deposition,

Specifically, (Fig.2) estimated the relative importance of various cadmium sources to

human exposure (Van Assche 1998).

Health effects related to cadmium consumption

Symptoms of acute toxicity are vomiting, choking sensation, abdominal pain and

diarrhea occurring within 30 minutes of exposure. Chronic or low level exposure can

include increased salivation, fatigue, weight loss, muscle weakness, and kidney

dysfunction (as late as 10 to 20 years after chronic exposure). Some late stage

effects may be anemia, hypertension, and skeletal effects which includes, back pain

and pain in the extremities, softening of the bone (an adult form of rickets) and

Japanese "itai-itai" (ouch-ouch) disease. Inhaling cadmium dust may produce

pulmonary emphysema (Pangborn, 1994). Cadmium has also been designated as a

category 1 carcinogen by the_IARC (Smith et al., 1997). An accumulation of cadmium

in kidney tissue has a biological half-life of 18 to 33 years (Pangborn, 1994).

Cadmium, an extremely toxic heavy metal, linked with learning disabilities (Jiang et

al., 1990) and kidney damage, (Pangborn, 1994) enters the environment mainly

through human activity.

Breathing high levels of cadmium may severely damage the lungs and can

cause death. Eating food or drinking water with very high levels severely irritates the

stomach, causing vomiting and diarrhea. The Minnesota Department of Health

(MDH) established a health risk limit (HRL) of 4 J..lgl 1 (parts per billion) for cadmium

42

Studies On Technology Oriented Methods For Water Contaminants And The G~hemlcaltnPuences On Contaminated Plume

(MPCA, 1999). Cadmium mainly accumulates in the kidneys and liver and can lead to

serious kidney failure, nephrotoxicity, renal stone formation, bone disease and

persistent proteinuria at high exposures. Cadmium stays in the body a very long time

and can build up from many years of exposure to low levels. Recent studies have

shown that the effects are reversible at low exposures, once exposure to cadmium is

reduced.

Iron is the most important metal in the universe. It is considered the most abundant

element (by mass, 34.6%) in the earth as a whole and it ranks fourth in abundance in

the earth crust after oxygen, silicon and aluminium. The concentration of iron in the

various layers of the Earth ranges from high at the inner core to about 5% in the

outer crust. Most of this iron is found in various iron oxides, such as the minerals

hematite, magnetite, and taconite. The iron contents in different rocks has been

given in Table.2. The earth's core is believed to consist largely of a metallic iron

nickel alloy (Lenntech, 2006). It occurs as minor constituents of all mineral classes.

Of the major chemical elements in the earth crust, iron is unusual in that it occurs in

several valence states. The fact that it may be oxidized or reduced in natural

environments markedly effects its geochemical cycle. Although iron is locally

markedly enriched in bodies is considered to have been formed by either magmatic

or hydrothermal processes, by far the most extensive anomalous concentrations are

found in groups of sedimentary rocks called iron- formations and ironstones.

43

Studies On Technology Oriented Methods for Water Contaminants And The Geochemlca/lnPuences On Contaminated Plume

Table 2. Average iron contents of various rocks

Rock type Fez03 FeO Total Fe Source

Igneous rocks

Average 2.9 3.3 4.6 Brotzen, 1966

Granites 1.6 1.8 2.5 Daly, 1933

Granodiorites 1.3 2.6 2.9 Nockolds, 1954

Diorites 2.7 7.0 7.3 Nockolds, 1954

Olivine basalts 3.7 8.1 8.9 Poldervaardt, 1955

Peridotites 2.5 9.9 9.4 Nockolds, 1954

Sedimentary rocks

Average 3.5 2.6 4.5 Garrels and Mackenzie, 1963

Sandstones 1.7 1.5 2.4 Pettijohn, 1963

Shales 4.2 3.0 5.3 Clarke, 1924

Limestones 0.36 Clarke, 1924

Iron formations 28.0 lepp and Goldich, 1974

Metamorphic rocks

Quartzo-feldspathic 1.6 2.0 2.7 Poldervaardt, 1955

gneisses

Mica schists 2.1 4.6 5.0 Poldervaardt, 1955

Precambrian slates 4.1 6.7 8.1 Nanz, 1953

The world resources of iron ore have been increasing over the last more than 30

years. This shows that as and when the mining activity intensifies, there is more

exploration and more discoveries of resources of iron ore world-wide. The world

iron ore reserves and reserve base as estimated by U.5.Geological Survey {USGS,

2005) are as under:


Table 3. World iron ore reserves

Qty: Million Tonnes

Crude ore Iron content

Reserves Reserve Base Reserve Reserve Base

United states 6900 15000 2100 4600

Australia 18000 40000 11000 25000

Brazil 21000 62000 14000 41000

Canada 1700 3900 1100 2500

China 21000 46000 7000 15000

India 6600 9800 4200 6200

Iran 1800 2500 1000 1500

Kazakhstan 8300 19000 3300 7400

Mauritania 700 1500 400 100

Mexico 700 1500 400 900

Russia 25000 56000 14000 31000

South Africa 1000 2300 650 1500

Sweden 3500 7800 2200 5000

Ukraine 30000 68000 9000 20000

Venezuela 4000 6000 2400 3600

Other 10000 30000 6200 17000

countries

World Total 160000 370000 80000 180000

(Rounded)

Source: U.S. Geolog1cal survey, 2005

45

Grade

Studies On Technology Oriented Methods For Water Contaminants And The Gtoeh~mlca/lnflu~nc~s On Contaminated Plume

Indian Resources

The Indian resources of iron ore have been made compatible with United Nations

Framework Classification (UNFC) which is more scientific and adopted in most

countries of the world. The resource position since 1.1.1980 till 1.4.2000 have been

tabulated in Table 4.

An important issue relevant to India's iron ore reserves is that unlike

Australia and Brazil, in India there have been no exploration programmes

undertaken exclusively for locating new additional deposits of iron ore. Our current

finds are a part of the Geological Survey of India's annual survey routinely carried

out for all minerals within the constraints of manpower and resources.

Table 4. Iron ore resources and production between 1980, 1990 and 2000

Resources Production Resources Difference Production Resources Difference

as on between as on in between as on in

1.1.1980 1980-1990 1.4.1990 resources 1990-2000 1.4.2000 resources

Haematite 11469 12197 +728 a)Reserves +709

6025

b)Remaining

resources

6881

Total12906

Magnetite 6095 10590 +4495 a)Reserves +92

286

b)Remaining

resources

10396

Total10682

Total 17564 470 22787 +5223 656 a)Reserves +801

6311

b)Remaining

resources

17277

Total23588

'--· Source: Indian Bureau of mmes, Nagpur

46

Studies On Technology Oriented Methods For Water Contaminants And The GtroCMmlca/Jnfluences On Contaminated Plume

REGIONAL DISTRIBUTION

Broadly there are two regions which produce iron ore: (a) Central and Eastern India

comprising Chhattisgarh, Jharkhand and Orissa; and (b) South-Western India

comprising Karnataka and Goa.

Region (a) comprising of Chhattisgarh, Jharkhand and Orissa together produced

69.33 million tonnes or 56.44% and 79.77 million tonnes or 55.90% of the total

production of iron ore in India in 2003-04 and 2004-05 respectively. This is the

region where all the integrated steel plants in public or private sectors are situated

who draws all their requirements of iron ore from their captive mines. NMDC looks

after the iron ore requirements of RINl. Gas-based sponge iron plants also draw

their maximum requirements from NMDC and source some quantity from

noncaptive mines in Eastern and Bellary-Hospet (Karnataka) sectors.

Region (b) comprising of Karnataka and Goa contributed 51.88 million tonnes or

42.23 %of the country's total iron ore production of 122.84 million tonnes in 2003-

04. In 2004-05, this was 59.48 million tonnes or 41.68% of the total production of

142.71 million tonnes in the country.

Unlike other metallic ores such as lead, zinc, copper, nickel and gold, where the

metal content in the ore varies from 5-10% to a fraction of even 1% per tonne of

ore, in the case of iron ore, the iron content averages 60% Fe and above. Whereas

other metals have to be concentrated or smelted at or near about the mine site, in

the case of iron ore, it can be transported over long distances where the steel plants

are situated. Since the steel plants are situated in the countries where the domestic

demand for steel is intense, the main raw material for steel such as iron ore and

coke have to be transported to these plants from far away countries.

STEEL PRODUCTION FROM IRON ORE

Nearly all iron produced commercially is used in the steel industry and made using a

blast furnace. Iron oxide, Fe20 3, is reduced with with carbon (as coke) although in

the furnace the actual reducing agent is probably carbon monoxide, CO.

47

Studies On Technology Oriented Methods For Water Contaminants And The G«Jchemlcallnfluences On Contaminated Plume

2Fe203 + 3C ~ 4Fe + 3C02

This process is one of the most significant industrial processes in history and the

origins of the modern process are traceable back to a small town called

Coalbrookdale in Shropshire (England) around the year 1773.

Steel is an alloy of iron usually containing less than 1% carbon. It is used most

frequently in the automotive and construction industries. Steel can be cast into bars,

strips, sheets, nails, spikes, wire, rods or pipes as needed by the intended user.

POLLUTION SOURCES IN STEELMAKING

In the 1980's it became apparent that iron and steel plant wastes, emissions and

effluents were a cause of concern due to, ground water contamination from

stockpiling or land filling, air born particulates were contaminating soils in

surrounding plant areas and there was concern of the greenhouse effect from gas

emissions. As a result, restrictions were put on land filling and stockpiling of wastes

and air born emissions from plants and a new era of monitoring and control was

established. The added cost to iron and steel making then dictated that new

technologies be developed for collecting the emissions and effluents and treating

the collected materials to reduce leaching into groundwater and potential health

hazards.

Slag, the limestone and iron ore impurities collected at the top of the

molten iron, make up the largest portion of iron making by-products. Sulfur dioxide

and hydrogen sulfide are volatized and captured in air emissions control equipment

and the residual slag is sold to the construction industry (USEPA, 1985). Blast furnace

flue gas is also generated during ironmaking. This gas is cleaned to remove

particulates and other compounds, allowing it to be reused as heat for coke furnaces

or other processes.

According to Toxic release inventory (TRI) data, the iron and steel industry

released and transferred a total of approximately 695 million pounds of pollutants

during calendar year 2003. About 75% of iron and steel establishments are

respons1ble for releases and transfers. The releases and transfers are dominated by

-~~~-~--~~~~~~~~~~~~~~~~~~~~--

48

Studies On Technology Oriented Methods For Water Contaminants And Th~ Geoclremkallnflumces On ContamJnoted PluTM

large volumes of metal-bearing wastes. The majority of these wastes (70 percent or

488 million pounds) are transferred off-site for recycling, typically for recovery of the

metal content. Transfers of TRI chemicals account for 86 percent of the iron and

steel industry's total TRI-reportable chemicals (609 million pounds) while releases

make up 14 percent (85 million pounds) (TRI, 2005). Metal-bearing wastes account

for approximately 80 percent of the industry's transfers and over fifty percent of the

releases.

HEALTH EFFECTS OF IRON IN WATER

The total amount of iron in the human body is approximately 4 g, of which 70% is

present in red blood colouring agents. Iron is a dietary requirement for humans, just

as it is for many other organisms. Men require approximately 10 mg iron on a daily

basis, whereas women require 18 mg per day (Carson et al., 1987). The body absorbs

approximately 25% of all iron present in food. When someone is iron deficit feed

iron intake may be increased by means of vitamin C tablets, because this vitamin

reduces tertiary iron to binary iron. Phosphates and phytates decrease the amount

of binary iron. In food iron is present as binary iron bound to haemoglobin and

myoglobin, or as tertiary iron. Iron is a central component of haemoglobin. It binds

oxygen and transports it from lungs to other body parts. It then transports C02 back

to the lungs, where it can be breathed out. Iron is a part of several essential

enzymes, and is involved in DNA synthesis (Lenntech, 2006). Normal brain functions

are iron dependent. In the body iron is strongly bound to transferrin, which enables

exchange of the metal between cells. The compound is a strong antibiotic, and it

prevents bacteria from growing on the vital element. When one is infected by

bacteria, the body produces high amounts of transferrin. When iron exceeds the

required amount, it is stored in the liver. The bone marrow contains high amounts of

iron, because it produces haemoglobin. Iron deficits lead to anaemia, causing

tiredness, headaches and loss of concentration. The immune system is also affected.

In young children this negatively affects mental development, leads to irritability,

and causes concentration disorder. Young children, pregnant women and women in

their period are often treated with iron (II) salts upon iron deficits.

Studies On Technology Oriented Methods For Water Contaminants And The Ge«ht!m/c:DIInf/ut!nct!S On Contaminated Plume

When high concentrations of iron are absorbed, for example by

haemochromatose patients, iron is stored in the pancreas, the liver, the spleen and

the heart. This may damage these vital organs. Iron compounds may have a more

serious effect upon health than the relatively harmless element itself. Water soluble

binary iron compounds such as FeCb and FeS04 may cause toxic effects upon

concentrations exceeding 200 mg, and are lethal for adults upon doses of 10-50 g. A

number of iron chelates may be toxic, and the nerve toxin iron penta carbonyl is

known for its strong toxic mechanism. Iron dust may cause lung disease.

FLUORIDE

Fluorine is the lightest member of Group 17 (VIlA) ofthe periodic table. This group,

the halogens, also includes chloride, bromine, and iodine. As with the other

halogens, fluorine occurs as a diatomic molecule, F2, in its elemental form. It has

only one stable isotope and its valence in all compounds is -1. Fluorine is the most

reactive of all the elements, which may be attributed to its large electronegativity

(estimated standard potential +2.85 V) (Hem, 1989). It reacts at room temperature

or elevated temperatures with all elements other than nitrogen, oxygen, and the

lighter noble gases. Fluorine is also notable for its small size; large numbers of

fluorine atoms fit around atoms of another element. This, along with its

electronegativity, allows the formation of many simple and complex fluorides in

which the other element is in its highest oxidation date. F easily combines with

several cations, viz., Al3•, Ca2

• and Fe3• and forms stable complexes. Hence,

partitioning of F between complexed form, and free ionic form !n, in an aqueous

system, is always expected.

GEOGRAPHICAL DISTRIBUTION

Fluorosis has been described as an endemic disease of tropical climates, but this is

not entirely the case. Waters with high fluoride concentrations occur in large and

extensive geographical belts associated with a) sediments of marine origin in

mountainous areas, b) volcanic rocks and c) granitic and gneissic rocks. High fluoride

50

Studies On Technology Oriented Methods For Water Contaminants And The Geochemical Influences On Contaminated Plumt!

containing groundwater was found in many parts of the developing world and

fluorosis is endemic in at least 25 countries across the globe (Tetsuji et al., 1997).

The worst affected areas are the arid parts of northern China {Inner Mongolia),

India, Srilanka, African countries like Ghana, Ivory coast, Senegal, North Algeria,

Kenya, Uganda, Tanzania, Ethiopia, northern Mexico and central Argentina.

High groundwater fluoride concentrations associated with igneous

and metamorphic rocks such as granites and gneisses have been reported from

India, Pakistan, West Africa, Thailand, China, Sri Lanka, and Southern Africa. In Kenya

and South Africa, the levels can exceed 25 mgl:1. In India concentrations up to 38.5

mgl-1 have been reported (Susheela and Ghosh, 1990). The highest concentration

observed to date in India is 48 mgl-1 in Rewari District of Haryana {UNICEF, 1999).

The high concentrations in groundwater are a result of dissolution of fluorite, apatite

and topaz from the local bedrock, and {Handa, 1975) noted the general negative

correlation between fluoride and calcium concentrations in Indian groundwater.

In 1991, 13 of India's 32 states and territories were reported to have

naturally high concentrations of fluoride in water (Mangla, 1991), but this had risen

to 17 by 1999 {UNICEF, 1999). The most seriously affected areas are Andhra

Pradesh, Punjab, Haryana, Rajasthan, Gujarat, Tamil Nadu and Uttar Pradesh

(Kurnaran, et al., 1971; Teotia et al., 1984). In India alone people of 196 districts in

35 states and union territories are drinking fluoride contaminated water above the

Maximum allowed concentration {MAC) (Susheela, 2001) and are confronte9;~G·~~::< '"·"''-' ... r """ -

the problems of fluorosis especially in rural and semi-urban areas. --~ Y-' ,-,. ..- ,...,

t/r --'r' ,lj, ' '

~·"· > 1 , ' 1 . 7'' . .,. (o . -- ... ' ) ... ~ '•'- '

'•\ FLUORIDE DISTRIBUTION IN WATER ·' .

Some fluoride compounds in the earth's upper crust are soluble in water, fluoride is

found in both surface and groundwater. In surface freshwater, fluoride

concentrations are usually as low as 0.01-{).3 parts per million. In groundwater, the

natural concentration of fluoride depends on geological, chemical, and physical

characteristics of the aquifer, the porosity and acidity of the soils and rocks, the

temperature, the action of other chemical elements and the depth of wells. The

fluoride concentrations in groundwater can range from well under 1 mgl'1 to more

than 35 mgl·l Seawater typically contains about 1 mgl'1 while rivers and lakes

I . . \\ ·jr. ., ....... T 2249!,

51

Studies On Technology Oriented Methods For Water Contaminants And The Geochemlcalln/fuenc~ On Contaminated Plume

generally exhibit concentrations of less than 0.5 mgL-1• In groundwaters, however,

low or high concentrations of fluoride can occur, depending on the nature of the

rocks and the occurrence of fluoride-bearing minerals. Concentrations in water are

limited by fluoride solubility, so that in the presence of 40 mgL-1 calcium it should be

limited to 3.1 mgl-1 (Hem, 1989). It is the absence of calcium in solution, which

allows higher concentrations to be stable (Edmunds and Smedley, 1996). High

fluoride concentrations may therefore be expected in groundwaters from calcium

poor aquifers and in areas where fluoride-bearing minerals are common.

FLUORIDE EXPOSURE TO HUMANS

Air

Due to dust, industrial production of phosphate fertilizers, coal ash from the burning

of coal and volcanic activity, fluorides are widely distributed in the atmosphere.

However, air is typically responsible for only a small fraction of total fluoride

exposure (USNRC, 1993). In non-industrial areas, the fluoride concentration in air is

typically quite low (0.05-1.90 Jlgm"3 fluoride) (Murray, 1986). In areas where

fluoride-containing coal is burned or phosphate fertilizers are produced and used,

the fluoride concentration in air is elevated leading to increased exposure by the

inhalation route. High levels of atmospheric fluoride occur in areas of Morocco and

China (Haikel et al., 1986, 1989). In some provinces of China, fluoride concentrations

in indoor air ranged from 16 to 46 Jlgm -J owing to the indoor combustion of high

fluoride coal for cooking and for drying and curing food (WHO, 1984). Indeed, more

than 10 million people in China are reported to suffer from fluorosis, related in part

to the burning of high fluoride coal (Gu et al., 1990).

Dental products

A number of products administered to, or used by, children to reduce dental decay

contain fluoride. This includes toothpaste (100D-1500 mgkg-1 fluoride), fluoride

solutions and gels for topical treatment (25D-24000 mgkg-1 fluoride) and fluoride

tablets (0.25, 0.50 or 1.00 mg fluoride per tablet), among others. These products

contribute to total fluoride exposure, albeit to different degrees. It is estimated that

-------------------------~

52

Studies On Technology Oriented Methods For Water Contaminants And The GNCMmlcallnPuences On Contaminated PI~

the swallowing of toothpaste by some children may contribute about 0.50 or 0.75

mg fluoride per child per day (Murray, 1986).

Food and beverages other than water

Vegetables and fruits normally have low levels of fluoride (e.g. 0.1-Q.4 mg kg-1} and

thus typically contribute little to exposure. However, higher levels of fluoride have

been found in barley and rice (e.g. about 2 mg kg-1) and taro, yams and cassava been

found to contain relatively high fluoride levels (Murray, 1986}. In general, the levels

of fluoride in meat (0.2-1.0 mg kg-1) and fish (2-5 mg kg-1) are relatively low.

However, fluoride accumulates in bone and the bones of canned fish, such as

salmon and sardines, which are also eaten. Fish protein concentrates may contain

up to 370 mg kg-1 fluoride. However, even Milk typically contains low levels of

fluoride, e.g. 0.02 mgl-1 in human breast milk and 0.02-D.05 mgl-1 in cow's milk

(Murray, 1986). Tea leaves contain high levels of fluoride (up to 400 mg kg-1 dry

weight). Fluoride exposure due to the ingestionof tea has been reported to range

from 0.04 mg to 2.7 mg per person per day

(Murray, 1986}.

HUMAN HEALTH EFFECTS

Fluoride in drinking water is beneficial at lower concentrations but hazardous to

health at higher levels. Health effect from prolonged intake of fluoride contaminated

water have been reported (Dissanayake, 1991) as: <0.5 mgl.1: dental carries; 0.5-

1.5 mgl"1: promotes dental health; 1.5-4.0 mgl-1: dental fluorosis; >4.0 mgl"1

: dental

and skeletal fluorosis; and >10.0 mgl.1: crippling fluorosis. According to the World

Health Organization (WHO), the maximum allowed concentration (MAC) of fluoride

in drinking water is 1.5 mgl·1 but it is not universally accepted. WHO (1984}

suggested that in warm climate the MAC of fluoride should be <1.0 mgl·1 while in

cooler climate it can go up to 1.2 mgl"1. In India the MAC for fluoride in drinking

water was lowered from 1.5 to 1.0 mgl"1 in 1998. There are several million people in

India exposed to drinking water sources with high fluoride content.

53

Studies On Technology Oriented Methods For Water Contomlncmts And The Grochemlcolln/fuences On Contamlfrat«< Plume

Effects on teeth

The beneficial and the detrimental effects of fluoride naturally present in water

were well established by the early 1940s. Fluoride accumulates in bones and teeth

as fluorapatite and causes bone to become brittle (Cauley et al., 1995; Fratzl, 1994;

Grynpas, 1990). High levels of fluoride present in concentrations up to 10 mgl-1 were

associated with dental fluorosis (yellowish or brownish striations or mottling of the

enamel) while low levels of fluoride, less than 0.1 mgl-1, were associated with high

levels of dental decay (Edmunds and Smedley, 1996). Concentrations in drinking

water of about 1 mgl-1 are associated with a lower incidence of dental caries,

particularly in children, whereas excess intake of fluoride can result in dental

fluorosis. In severe cases this can result in erosion of enamel. The margin between

the beneficial effects of fluoride and the occurrence of dental fluorosis is small and

public health programmes seek to retain a suitable balance between the two (IPCS,

2002).

Skeletal effects

It is primarily associated with the consumption of drinking-water containing elevated

levels of fluoride but exposure to additional sources of fluoride such as high fluoride

coal is also potentially very important. This is compounded by a number of factors

which include climate, related to water consumption, nutritional status and diet,

including additional sources of fluoride and exposure to other substances that

modify the absorption of fluoride into the body. Crippling skeletal fluorosis, which is

associated with the higher levels of exposure, can result from osteosclerosis,

ligamentous and tendinous calcification and extreme bone deformity. Evidence from

occupational exposure also indicates that exposure to elevated concentrations of

fluoride in the air may also be a cause of skeletal fluorosis (IPCS, 4002).

One possible feature of fluorosis is bone fracture, although some studies have

reported a protective effect of fluoride on fracture. In an epidemiological study the

relationship between fluoride intake via drinking-water and all other sources, and all

fractures, followed a U shaped dose response with higher rates of fracture at very

low intakes below 0.34 mgl - 1 and high intakes above 4.32 mgl - 1 (total intake 14 mg

per day) (Li eta/., 2001). It was concluded by the IPCS that for a total intake of 14 mg

-----------------------------54

Studies On Technology Oriented Methods For Water Contaminants And The Geochem/collnfluences On Contaminated Plume

per day there is a clear excess risk of skeletal adverse effects and there is suggestive

evidence of an increased risk of effects on the skeleton at total fluoride intakes

above about 6 mg per day {IPCS, 2002).

FLUORIDES IN INDUSTRY

Fluorides are important industrial chemicals with a number of uses but the largest

uses are for aluminium production, drinking water fluoridation and the manufacture

of fluoridated dental preparations {IPCS, 2002).

• Hydrogen fluoride {HF) is a colourless, pungent liquid or gas that is highly

soluble in organic solvents (e.g., benzene) and in water. It is mainly used

in the production of synthetic cryolite {Na3AIF6), aluminium fluoride

(AIF3), motor gasoline alkylates and chlorofluorocarbons {CFCs). It is also

used in etching semiconductor devices, cleaning and etching glass,

cleaning brick and aluminium and tanning leather, as well as in removing

rust.

• Calcium fluoride {Cah) is a colourless solid that is relatively insoluble in

water and dilute acids and bases. It is used to produce steel, glass and

enamel {because it lowers the melting temperature}, hydrofluoric acid

and anhydrous hydrogen fluoride (as raw material), and aluminium (as

electrolyte).

• Sodium fluoride (NaF) is a colourless to white solid that is moderately

soluble in water. It is used in the fluoridation of drinking water and in the

manufacture of dental preparations such as toothpaste. It is also used in

the production of steel and aluminium (to lower the melting

temperature). glass and enamel, or as an insecticide and a preservative

(for glues and wood).

• Sulfur hexafluoride (SF6) is a colourless, odourless, inert gas that is slightly

soluble in water and readily soluble in ethanol and bases. It is used

extensively in various electronic components and in the production of

magnesium and aluminium.

55

Studies On Technology Oriented Methods for Water Contaminants And rhe G~~mlcalln/luences On Contaminated Plume

• Silicofluorides such as fluorosilicic acid (H2SiF6) and sodium

hexafluorosilicate (Na2SiF6) are also used for the fluoridation of drinking

water supplies.

PROPOSED AND ATTAINED OBJEOIVES OF THESIS

This thesis has attempted to study the genesis of the groundwater contaminants

that are emerging either as a result of industrial activity or may be due to some

geochemical reactions and the possible remediation of the contaminants with the

help of emerging technology. Through the process of biosorption mitigation of

various elements present in the ground water, which show their toxic effects when

present even in small amounts was attempted. This would be certainly beneficial for

the society and also to the industries due to their cost effectiveness.

The main objectives proposed and the objectives attained are enlisted below:

Sr.

no.

1.

2.

'

Table 5. OBJECTIVES PROPOSED AND THE OBJECTIVES ATTAINED

Proposed research work Objectives attained Chapters

concerned

Introduction related to Detailed literature survey of the Chapter 1

elemental contamination in the groundwater contamination

ground water and the possible and the remedial techniques

remediation. has been carried out.

Mineral- water interfacial A complete analysis of ground Chapter 2

reactions and their effect on water of different locations in

elemental mobilisation. Durg -Bhilai region was carried

out to observe the metal L __ ~_L·-~-~~~~~~~~---'L-~~~~~~-~~-~...L~~~~_j

56

Studies On Technology Oriented Methods For Water Contaminants And The GeochemlcollnPuences On Contaminated Plume

3. Adsorption of iron from

groundwater and industrial

wastewater by the plant

biomass.

L_ ···-- -- -- ..

contamination at industrial,

central and boundary region of

Bhilai. Presence of Fe2•, Mn2

•,

As(lll), so/,cr, Alkalinity, Ca2•,

was

determined by analyzing ground

water in the lab. In view of the

frequent prevalence of Fe(ll)

and s2· detailed geo-chemical

interaction was studied to

identify the probable source of

contamination.

Groundwater contamination by

exceedingly high concentration

of iron has been successfully

sequestered by an indigenous

plant material. The effect of

various ions present in ground

water was also studied

simultaneously. Different

parameters like:

1) Effect of pH.

2) Effect of increasing metal ion

concentration.

3) Effect of biomass dosage.

4) Effect of contact time.

5) Effect of various interfering

ions.

6) Study of adsorption isotherm

was investigated using fresh

Chapter 3

57


and the leached biomass.

7) A study on the binding

mechanism of the biomass

with the help of FT-IR studies

was carried out.

8) An application of the biomass

with the synthetic effluent

was carried out.

4. Cadmium removal from A native plant of Chhattisgarh, Chapter 4

contaminated ground water and has been identified whose

industrial effluents by adsorbent cadmium uptake capacity

treatment. surpasses other reported

biosorbents. The biomass was

chemically treated to increase

the sorption capacity. Various

parameters _were optimized

during the experiment to

observe the maximum sorption

capacity of the related biomass.

Mechanism of metal binding

has also been extensively

studied by carrying out its FT-IR

study.Various Parameters like:

1) Effect of pH.

2) Effect of Increasing metal ion

concentration.

3) Effect of Biomass dosage.



ions. ~-- ____ J_~ _________ __l __________ L_ __ _____j

58

Studies On Technology Oriented Methods For Water Contaminants And The GNChem/calln/luenas On Contaminated Plume

5. Removal of fluoride from

aqueous solution by 'Fiuorofix'.

6) Study of adsorption isotherm.

7) Elution study

were investigated. For

applicability of the biomass a

synthetic solution was

prepared for the adsorption

study.

A metal doped biopolymer has Chapter 5

been synthesised to remove

fluoride from ground water. A

systematic study was done to

optimize the various

parameters so as to achieve

an increased adsorption.

Effect of tempertature on the

sorption behaviour was

investigated. The effect of

interfering ions naturally

present in ground water was

also studied. The parameters

optimized during the

experimental work were

1) Effect of pH.

2) Effect of Increasing metal ion

concentration.

3) Effect of Biomass dosage.



ions.

6) Study of adsorption isotherm. ··- . - c_ ______________ __L ____________ L_ ____ ..J

59

Studies On Technology Oriented Methods For Water Contaminants And 1M G~ochemlca/lnfluences On Contaminated Plum~

7) Effect of particle size.

8} Elution study.

9} Application of the Fluorofix

for the fluoride contaminated

groundwater was carried out

by preparing a synthetic

solution.

60

REFERENCES

ATSDR, 1997. Agency for Toxic Substances and Disease Registry, Draft Toxicological

Profile for Cadmium, Public Health Service, U.S. Department of Health &

Human Services, Atlanta, Georgia.

B-Focasd, Parent Support Group. e-mail: [email protected].

Blaylock, M.J., Huang, J. W., 2000. Phytoextraction of metals. ln:l. Raskin and B.D.

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