CHAPTER - VIII

WATER TREATMENT TECHNIQUES

WATER TREATMENT TECHNIQUES

1.0 INTRODUCTION

For several hundred years, use of traditional technologies for the

treatment of drinking water has been in practice in many parts of India,

Africa and South America. The primary aim of water purification is to

remove any potentially dangerous chemicals or micro-organisms and also to

render the water aesthetically appealing. The drinking water should be free

from colour, odour, turbidity and micro-organisms. The sewage from

houses or villages is treated by the use of natural concepts like use of soil

~nfiltration systems, reed beads, ponds and wetlands. Improper disposal of

wastewater has led to both surface and ground water contamination

Water supplies have been contaminated by various pollutants such

as metals, organics and refractory compounds from municipal sewage,

industrial and agricultural discharges. The presence of low concentration of

a variety of refractory compounds cause a major difficulty in the use and

reuse of water streams. Water containing significant concentrations of these

pollutants is harmfbl to human beings, animals and aquatic organisms. It is

estimated that, worldwide, approximately 250 million new cases of water-

borne diseases occur each year with over 10 million resulting in death

(WHO, 1992). The toxic compounds enter the food chain resulting in

bioaccumulation.

The application of water treatment technologies available in

developed countries are not applicable in toto in developing countries

especially in rural areas because of

* Limitations of funds

* Import of water treatment chemicals

* Non-availability of skilled man power

In the present study efforts have been made to identify cost

effective suitable treatment methods to remove selected metals and

fluorides from the contaminated waters.

2.0 TRADITIONAL METHODS OF WATER TREATMENT

The treatment of contaminated water is done through different

physical, chemical and biological processes. The basic processes involved

are floatation, sedimentation, filtration and disinfection. '

2.1 Floatation

During floatation, the particles are allowed to float, when water to

be heated is accelerated with compressed air. As air saturated water enters

the bulk of water which is at a low pressure, fine air bubbles separate from

water and act as centers of floatation of light suspended impurities. Electro

floatation is a newly available technique where gas bubbles are generated

electrolytically instead of mechanical agitation or compressed air.

2.2 Sedimentation

In this the tendency of solid particles to settle by gravitational

force is made use of. Sedimentation can be accelerated by centrifugation

2.3 Filtration

Filtration depends on the flow of water through a porous solid, on

which the insoluble particles are retained

Residential filters are a common fonn of filtration.

The basic fonn of residential filter, used in nual areas where there

is no public water supply, is the tub filter. The tub filter consists of two tubs

made of mud or clay, pottery or plastic, and joined one above the other. The

upper tub contains the filter medium (sand, gravel, coal, stone, etc.), into

which the water to be treated is poured. It moves through the filter medium,

through holes in the base of the upper tub, to the lower tub, where it is

stored until used. A faucet is usually installed in the lower tub for

convenient access. Homemade filters, such as the tub filters, are usually

constructed with locally available materials. Both the gravel and the sand

are cleaned and dried in the sun, before use. The commercial systems

usually have a stainless steel frame, with appropriate connections that make

installation and operation relatively simple. Many commercial filters

contain filtration media like candle other than sand or gravel.

2.4 Disinfection

It is carried out for annihilation of pathogenic bacteria and viruses.

This can be achieved by boiling or using chlorine and its derivatives, ozone

or by other ultraviolet radiation.

(a) Boiling and chlorination

Boiling and chlorination are the most common water and

wastewater disinfection processes in use throughout the world. Boiling is a

very simple method of water disinfection. Heating water to a high

temperature, 100°C, kills most of the pathogenic organisms, particularly

viruses and bacteria that cause waterborne diseases. In order for boiling to

be most effective, the water must boil for at least 20 minutes. Since boiling

requires a source of heat, rudimentary or non-conventional methods of heat

generation may be needed in areas where electricity or fossil fuels are not

available.

Chlorination is another common type of wastewater and water

disinfection. It should be noted that it is designed to kill harmful organisms,

and generally does not result in sterile water (free of all microorganisms).

Two types of processes are generally used: hypochlorination, employing a

chemical feed pump to inject a calcium or sodium hypochlorite solution,

and gas chlorination, using coniprcssad chlorine gas.

Hypochlorination:- Calcium hypochlorite is available commercially in

either a dry or wet form. ~ i ~ h - t e s t calcium hypochlorite (HTH), the form

most frequently used, contains about 60% available chlorine. Because

calcium hypochlorite granules or pellets are readily soluble in water and are

relatively stable under proper storage conditions, they are often favored

over other forms. Sodium hypochlorite is available in strengths from 1.5%

to 15%, with 3% available chlorine as the typical strength used in water

treatment applications. The higher the strength of the chlorine solution, the

more rapidly it decomposes and more readily degraded by exposure to light

and heat. It must therefore be stored in a cool location and in a corrosion-

resistant tank. Typically, 30 minutes of chlorine contact time is required for

optimal disinfection with good mixing. Water supply treatment dosages are

established on the basis of maintaining a residual concentration of chlorine

in the treated water.

Water-based solutions of either the liquid or the dry form of

hypochlorite are prepared in predetermined stock solution strengths.

Solutions are injected into the water supply using special chemical metering

pumps called hypochlorinators. Positive displacement types are the most

accurate and reliable and are commonly preferred to hypochlorinators

employing other feed principles (usually based on suction).

(b) Ultra violet light disinfection of drinking Water

Ultraviolet was first used as disinfect in Marseilles, France in 1910,

but its wide application has been very recent. The advantages of using W

are:

* UV does not produce the chloro-organic by-products such as

trihalomethanes which are carcinogenic

* The biocide effects of UV light are essentially instantaneous

* The small space requirements and the absence of toxic chemicals

make W particularly safe.

* UV is a relatively simple and low cost technology which is suitable for

small communities as well.

* UV disinfection of waste water effluents is an environmentally

friendly, effective economically viable operator and community safe

method.

(c) Application of ozone in water treatment

Ozone is an unstable gas which has to be generated on site.

Generation of ozone is based on the electrochemical breaking down of

oxygen into oxygen radicals which can combine with molecular oxygen to

form ozone:

Application of ozone in water treatment includes:

* Bacterial quality control

4 Taste and odour control

* viral inactivation agent

4 An inducer for biological treatment process

* Prevents the formation of organohalogen compounds

* Removal of iron and manganese

Other processes employed in preparation of potable water include

softening (removal and precipitation of hardness, salts), addition of alkaline

reagents, desalination (reduction of total mineral content) by distillation, ion

exchange or electrodialysis.

3.0 ION EXCHANGE

Ion exchange is a process by which one type of ion contained in

water is absorbed into an insoluble solid material and replaced by an

equivalent quantity of another ion of the same charge. An example is the

sodium exchange water softening, in which calcium and magnesium ions

are removed by means of a cation exchange resin and replaced by sodium.

This method is generally used for upgrading municipal or private water

resources in industry for water softening, for the purification of boiler feed,

for nuclear power stations.

3.1 Desalination

Desalination is a separation process used to reduce the dissolved

salt content of saline water to a usable level. All desalination processes

involve three liquid streams: the saline feedwater (brackish water or

seawater), low-salinity prpduct water, and very saline concentrate (brine or

reject water).

The saline feedwater is drawn from oceanic or underground

sources. It is separated by the desalination process into the two output

streams: the low-salinity product water and very saline concentrate streams.

The use of desalination overcomes the paradox faced by many coastal

communities, that of having access to a practically inexhaustible supply of

saline water but having no way to use it. Although some substances

dissolved in water, such as calcium carbonate, can be removed by chemical

treatment, other common constituents, like sodium chloride, require more

technically sophisticated methods, collectively known as desalination. In

the past, the diff~culty and expense of removing various dissolved salts

from water made saline waters an impractical source of potable water. The

product water of the desalination process is generally water with less than

500 mg/l dissolved solids, which is suitable for most domestic, industrial,

and agricultural uses.

3.1.1 Reverse Osmosis

Reverse Osmosis is a physical process by which dissolved material

in a solvent may be separated from that solvent with the assistance of a

semi-permeable membrane. By applying the pressure in excess of the

natural osmotic pressure to the feed water, only the pure water can pass

through the membrane while the impurities are rejected and run to waste.

The basic type of membrane commonly used is cellulose acetate membrane.

The other type of membrane in use are poly-arnides, polyphenylene

bibenzimidazoles etc.

A by-product of desalination is brine. Brine is a concentrated salt

solution (with more than 35 000 mg/l dissolved solids) that must be

disposed of, generally by discharge into deep saline aquifers or surface

waters with a higher salt content. Brine can also be diluted with treated

effluent and disposed of by spraying on golf courses andlor other open

space areas.

A reverse osmosis system consists of four major components/processes:

(1) pretreatment, (2) pressurization, (3) membrane separation, and (4) post-

treatment stabilization.

(1) Pretreatment: The incoming feedwater is pretreated to be compatible

with the membranes by removing suspended solids, adjusting the pH, and

adding a threshold inhibitor to control scaling caused by constituents such

as calcium sulphate.

(2) Pressurization: The pump raises the pressure of the pretreated

feedwater to an operating pressure appropriate for the membrane and the

salinity of the feedwater.

(3) Separation: The permeable membranes inhibit the passage of

dissolved salts while permitting the desalinated product water to pass

through. Applying feedwater to the membrane assembly results in a

freshwater product stream and a concentrated brine reject stream. Because

no membrane is perfect in its rejection of dissolved salts, a small pexentage

of salt passes through the membrane and remains in the product water.

Reverse osmosis membranes come in a variety of configurations. Two of

the most popular are spiral wound and hollow fine fiber membranes. They

are generally made of cellulose acetate, aromatic polyarnides, or, nowadays,

thin film polymer composites. Both types are used for brackish water and

seawater desalination, although the specific membrane and the construction

of the pressure vessel vary according to the different operating pressures

used for the two types of feed water.

(4) Stabilization: The product water from the membrane assembly usually

requires pH adjustment and degasification before being transferred to the

d~stribution system for use as drinking water. The product passes through

an aeration column in which the pH is elevated from a value of

approximately 5 to a value close to 7. In many cases, this water is

discharged to a storage cistern for later use.

3.1.2 Electrodialysis

It is based on the characteristics of ion selective electrodes. The

apparatus consists of multitude of membranes (the stack) in which the feed

water flows through narrow compartments between cations and anion

membranes placed alternatively. Two electrodes apply the EMF across the

stack, causing the sodium ions to move towards the negative electrode.

Thus the water in one compartment will be desalted and the other will be

enriched with ions.

4.0 REMOVAL OF HEAVY METALS BY COFFEE AND TEA

POWDER

4.1 Introduction

Increasing industrialisation and urbanisation including

technological advancemen, vehicular traffic, refinery emissions have

grossly contaminated the environment. Many mineral, metallurgical and

chemical industries release heavy metals, which are toxic in nature. Toxic

elements in the untreated effluents that get discharged into streams and

rivers may find their way into sea thus affecting aquatic life and also enter

the food chain causing health hazards. Ash, slag and sludge disposed off for

dumping as land fill materials may contain heavy metals, excess of

nutrients etc that may contaminate the envronment. Several diseases have

been attributed to the excessive exposure of some toxic metals and their

specific compounds which show differential mobility in the ecosystem

(Garge, 1997).

Removal of heavy metals prior to discharge into waterways is

essential. Several works have been reported for the removal of heavy metals

from industrial effluents using processes like precipitation, ion exchange,

solvent extraction etc. Some of these methods are costly and some are

found to be non-feasible. Copper, manganese and zinc are widely used in

industries and their ingestion beyond permissible levels leads to various

chronic disorders. Activated carbon is used as adsorbent for removal of

copper and zinc (Viswanadhan, 1997). The pathological effects that

different heavy metals present in water can cause in man are presented in

A report published by an International team of scientists in April

2000 issue of Human and Ecological Risk Assessment commented on the

healthy part of the nutritional breakfast by drinking coffee. The team

speculates that ground coffee retain heavy metals through surface chelation.

To test this hypothesis an attempt has been made in this study for the

removal of heavy metals using locally available different brands of coffee

and tea powder.

Table: 47 Pathological effects of heavy metal contaminated

water pollutants in man

I SI.No 1 Metal Patholog~cal effects

2

3

4

5

1 I Mercury 1 Abdom~nal pam, headache, d~arrhoea.

I I

Source : Chhatwal et al., 1989

Lead

Arsenic

Cadmium

Copper

I

hemolysis, chest pain. Anaem~a. vomltlng. loss of appetite, 1 convuls~ons, damage to bra~n, liver and / kidney. 1 Disturbed peripheral circulation, mental disturbances, liver cirrhosis, hyperkeratosis, lung cancer, ulcers in gastrointestinal tract, kidney damage. Diarrhoea, growth retardation, bone deformation, kidney damage, testicular atrophy, anaemia, injury to CNS and liver, hypertension. Hypertension, uremia, coma, sporadic fever.

Vomiting, renal damage, cramps. 6 Zinc

7

8

Hexavalent Chromium Cobalt

Nephritis, gastrointestinal ulceration, diseases in the CNS, cancer. Diarrhoea, low blood pressure, lung initation, bone deformation, paralysis.

4.2 Methodology

Experiments were done to study the removal of heavy metals using

coffee and tea powder. Artificially spiked water samples were prepared in

the laboratory using metal salts. Batch contact method experiments were

conducted for the study of removal of metals using varying amounts (100-

250mg) of coffee and tea powder. Different concentrations of metal salts

were added to the samples having fixed concentrations of coffee and tea

powder and shaken mechanically for one hour. Samples were removed after

one hour and the clay was separated by filtration. The residual metal

concentration was determined by using Atomic Absorption

Spectrophotometer. Similarly experiments were conducted for the removal

of copper, zinc and manganese. Results are presented in the tables 48 to 55.

Table: 48 Removal of copper using raw coffee powder with different

concentrations of copper

% Removal of copper

Table: 49 Removal of copper using raw coffee powder with varying amounts of coffee powder

Table: 50 Removal of copper using Brand coffee powder (Coorg) with different concentrations of copper

Weight of coffee

powder(mg)

100

concentration of Copper

powder After treatment % Removal of

copper (mg)

% Removal of copper

'- 78.5

concentration of Copper

Before treatment Mg/l

2.0

- After treatment

mgfl

0.43

Table: 5 1 Removal of Manganese using Brand Coffee powder (Coorg) with different concentrations o f Manganese

Table: 52 Removal of Manganese using Raw Coffee Powder with different concentration of Manganese

Table: 53 Removal of Zinc using raw coffee powder with different concentrations of Zinc

Table: 54 Removal of Zinc using raw coffee powder with varying concentrations of coffee powder

Table: 55 Removal of Copper using different brands of Tea

4.3 Results and discussion

Weight of tea

powder(mg)

Tea Dust

200

200

200

Agnl Tea

200

200

200

Red Label

The results of the experiments indicate that since coffee powder

binds strongly with the metal ions that metal can be separated and removed.

The raw coffee powder is found to be more effective in removing copper

than brand coffee powders. 80.75 % of copper is removed by raw coffee

powder from 4.0 mg/l copper containing solution (Table.48) and 95.37 %

copper is removed, when 250 milligrams of the powder is used to remove

2.0 mgll of copper (Table 49).

(f0.66) 40.25

(M.55) (M.78)

200 3.53 41.16

(f0.58) (f0.75)

% Removal of copper

64.50 (f 1.40)

49.0 (f1.10) 45.33

(M.89)

44.0 (k0.67) 5 1.25

(f 1.50) 45.8

(iO.88)

concentration of Copper

Before treatment mgfl

2.0

4.0

6.0

2.0

4.0

6.0

After treatmcnt mI3/1

0.71 (M.60)

2.04 (f0.20)

3.28 (M.22)

1.12 (f 0.22)

1.98 (f 0.52)

3.28 (fO.50)

In the case of manganese, only 63 % of its removal is effected from

a solution of 1.0 mgll of manganese using 200 mg of the coffee powder

(coorg brand) (Table.5 1). In the case of zinc, 300 mg of raw coffee powder

could remove 54 % of Zinc (Table.54) from a solution containing 6.0 mgll

of zinc. The percentage of reduction of copper from the solution was higher

by coffee powder than that of manganese and zinc. The percentage

reduction is presented in Fig. 46.

Of the different brands of tea available, tea dust is found to be more

effective in removing copper. About 64 % of copper is removed from a

solution containing 2 mgll of copper with 200 mg of tea dust, whereas with

Agni tea brand only 44 5 % could be removed and with Red Label tea

powder 45 % of copper could be removed from the solution containing the

same concentration of copper (Table.55).

Surface chelation appears to be the active mechanism in the

separation of metal ions. The present finding corroborates with the report of

Allen, (2000) which states that since ground coffee has negatively charged

nolecules, the removal is possibly through surface chelation. Since heavy

netals in the solution are positively charged, the metal ions bind strongly to

he coffee.

5.0 REMOVAL OF FLUORIDE BY CLAY

5.1 Introduction

According to the guidelines given by the World Health

Organization (WHO, 1984) fluoride is an effective agent for preventing

dental caries if taken in 'optimal' amounts. But a single 'optimal' level for

daily intake cannot be universal because the nutritional status of the

individuals, which varies greatly, influences the rate at which fluoride is

absorbed by the body. A diet poor in calcium, for example, increases the

body's retention of fluoride.

Water is the major source for fluoride intake. WHO (1984)

guidelines suggest that in a warm climate, the optimal fluoride

concentration in drinking water should remain below l.Oppm, while in

cooler climates it could be upto 1.20ppm. The differentiation is derived

from the fact that individuals perspire more in hot weather and

consequently consume more water. The guideline value (permissible upper

limit) for fluoride in drinking water is set at 1.5 ppm, a threshold level

where the significant risk of dental fluorosis does not set in.

In many countries, fluoride is purposely added to the water supply,

toothpaste and sometimes to other products to promote dental health. It

should be noted that fluoride is also found in some foodstuffs and in the air

(mostly from production of phosphate fertilizers or burning of fluoride-

containing fuels), so the ainount of fluoride people actually ingest may be

higher than assumed.

5.2 Heatth effects due to fluoride

Fluoride in drinking water, when consumed, gets deposited in the

bones replacing hydroxide leading to a chronic effect called skeletal

fluorosis. It affects both young as well as older individuals. As a result of

skeletal fluorosis, severe pains and stiffness in the joints and backbone,

increased density of bone, along with calcification of ligaments and

paralysis are experienced. Fluoride can enter the human body through food,

toothpaste, mouth rinses, other eatable products and of course more swiftly

through drinking water. A colorless and odorless natural pollutant, fluoride

comes in contact with the groundwater via erosion of fluoride bearing rock

minerals. Three major sources of fluorine in India are fluorspars, rock

phosphates and phosphorities. Most of the fluoride compounds found in the

earth's upper crust are soluble in water.

Dental fluorosis, which is characterized by discoloured, blackened,

mottled or chalky-white teeth, is a clear indication of overexposure to

fluoride during childhood when the teeth were developing. These effects are

not apparent on a fully grown teeth prior to fluoride overexposure. However

the fact that an adult may show no signs of dental fluorosis does not

necessarily mean that his or her fluoride intake is within the safety limit.

Chronic intake of excessive fluoride can lead to the severe and

permanent bone and joint deformations of skeletal fluorosis. Early

symptoms include sporadic pain and stiffness of joints: headache, stomach-

ache and muscle weakness can also be warning signs. The next stage is

osteosclerosis (hardening and calcifying of the bones), and finally the spine,

major joints, muscles and nervous system are damaged.

Whether dental or skeletal, fluorosis is irreversible and no treatment

exists. The only remedy is prevention, by keeping fluoride intake within

safe limits.

5.3 A review of defluoridation techniques

The different methods involved in the removal of fluoride include

materials that are fluoride exchangers like tricalciumphosphate, anion

exchangers, activated carbon, magnesium salt or aluminium salts.

The NALGONDA technology developed by NEERI (1974), for

fluoride removal involves rapid mixing of water with lime, alum and

bleaching powder. This results in flocculation, sedimentation and

disinfection.

The PRASANTHI (1978) technology uses the activated alumina for

fluoride removal.

5.4 Use of clay in waste water treatment

Bentonites are formed due to an alteration in volcanic ash. Their

abundant availability makes them attractive economical adsorbents.

Bantonite is mainly composed of montemorillonite which is a smeetite or a

2: 1 layered silicate. Montemorillonite crystals consist of two silicon-oxygen

tetrahedral co-ordinated layers that sandwich an aluminum -oxygen-

hydroxide octahedrally coordinated layer. Isomorphous substitution of

magnesium for aluminum within the octahedral layer provides a net

negative charge. This charge is equalized by the attraction of cations and

their associated waters of hydration to the tetrahedral surfaces. Bentonitc

occurs in two forms in nature, namely a sodium variety and a calcium

variety. On contact with water the swelling capacity of sodium bentonite is

more than calcium bentonite. Table 56 gives a typical analysis of sodium

bentonite.

Table: 56 Typical analysis of bentonite

Source: (Alfaro, 1993) Note: All values mentioned are in % (wlw)

Removal of contaminants by clays may be enhanced by tailoring

the clay through a cationic exchange of the natural hydmphilic cations with

hydrophobic organic cations to strongly adsorb toxic compounds. The

ability of montemorillonite to adsorb small organic compounds is highly

dependent upon the electrostatic interaction between the negative charge of

the clay and the valence and polarity of the adsorbing molecule. Adsorption

is nonexistent for small anions and less significant for neutral molecules.

The large surface area of bentonite becomes available for adsorption of

organic molecules like benzene once the natural cations are exchanged with

an organophilic cation such as tetramethyl ammonium (TMA) ion.

Clay minerals possess a net negative charge which is compensated

by exchange cations on their surface. These exchange ions are mainly alkali

metal and alkaline earth ions like sodium and calcium.The hydration of

these metal exchanged cations impart a hydmphilic nature to the mineral

surface. Such mineral surfaces are often not good adsorbents for organic

compounds which cannot compete with water for adsorption on the clay

mineral surface (Boyd et al, 1988). The sorptive properties of smeetite clays

for poorly water soluble organics like benzene and TCE are greatly affected

by the nature of the exchange cation and water, which strongly competes

for adsorption sites on the mineral surface (Boyd et al. 1988).

Montemorillonite is composed of unit layers each of which consists

of two silica sheets that sandwich an alumina octahedral sheet. The bonds

between the unit layers are weak and water or other polar molecules can

penetrate into the lamellar spaces and cause expansion (Huang and Laio,

1970). The advantages of montemorillonite lies in its ability to expand its

lamellae, and also in its large cation exchange capacity. Thp it can adsorb a

varjety of neutral organic compounds like ketones, aldehydes, amines, and

phenols (Sarkar et al, 1990). While the rate of pesticide uptake by activated

carbon is governed by intra particle transport processes, non -expansive

clays do not possess fine pores or capillaries and hence rate control by intra

particle transport cannot be expected. Montemorillonite clays are gradually

expanded by the entering molecules and this diffusion of entering

molecules into the expanding interlamellar spaces can behave like the

diffusion of intra particle transport (Haung and Liao, 1970).

The adsorption of organic compounds on to organo clays from

aqueous solution depends upon several factors: the substituted cation, the

degree of organophillic substitution, the equilibrium between adsorption on

to the clay and desorption by water with the organophillic/hydrophilic

character of the adsorbent molecules controlling the position of equilibrium,

the polarity of the adsorbate and the ability for hydrogen bonding have

influences on the adsorption effectiveness. No clay is likely to remove all

refractory contaminants found in secondary effluent as effectively as

activated carbon but may contribute to advanced wastewater treatment by

removing specific contaminants.

5.5 Methodology

Black soil collected from Chittoor in Palakkad district, Kerala was

used for clay suspension. Physical properties such as pH, bulk density,

moisture content and porosity of the black soil were determined and are

presented in Table 57.

Table: 57 Physical properties of blqck soil

Parameters value

Moisture content (%)

Bulk density( gmlcc) 1.47 4 porosity - 44.42

Clay was separated from the soil by dispersing in 2 liters of dilute

ammonia solution and allowed to settle for 24 hours. The upper layer

containing clay particles was removed. The arnmoniacal suspension was

neutralized and 100 gms of clay was flocculated with 10% magnesium

chloride and then separated from the liquid by decanting and further

centrifuging. The flocculated material was then washed with ethanol and

finally dried and ground to pass through a sieve of 0.20mm size. Separated

clay was identified to be montemorillonite, which is 2: 1 layered silicate.

5.6 Removal of Fluoride using montemorillonite clay

Experiments were conducted using clay for the removal of fluoride

from the contaminated water. Montemorillonite was found to be a good

adsorbent for fluoride also. Batch experiments were conducted for the

removal of fluoride using mintemorillonite clay. Definite weights of clay

were added to samples (Table 58) having varying concentrations of fluoride

and shaken mechanically for one hour. Samples were removed at intervals

of one hour each and clay was separated by filteration. The efficiency of

clay in removing fluoride- from its initial concentration of 5.0 mgA of

solution was found to be 80% (Table 58 and Fig.47).

223

Table: 58 Removal of fluoride by montemorillonite clay

6.0 CONCLUSIONS

I SI No.

1.

2.

i 3

4

1. Removal of Heavy metal by coffee and tea powder

Copper, Manganese and Zinc are the heavy metals used in the

present study. Experiments were conducted using with definite quantity of

tea and coffee powder with both definite and varying concentrations of

metals equilibrated for a period of two hours at room temperature. For the

same the period of equilibrium a larger quantity of copper was removed

followed by manganese and zinc.

Weight of the Clay (mg)

200

200

200

200

200

Copper > Manganese > Zinc.

2. Fluoride removal by clay

Initial Concentration of fluoride, mg/l

1 .O

2.0

3 .O

4.0

5.0

Batch experiments were conducted for the removal of fluoride

using montemorillionite clay and the clay is found to be more efficient in

removing fluoride content present in water. 80 % of fluoride removal in the

water was achieved by 200mg of clay.

Final Concentrat~on of fluoride, mg/l

0.60 (k 0.52)

0.78 (f 1.0) 0.85

( f 0.98) 0.90

(f I .20) 1 .O

(k1.0)

Percentage of reductton of fluor~dc

40.0 (*I .O) 61 .O

( i 0.56) 7 1.67

(i1.20) 77.50

(2 0.98) 80.0

(i 1.30)

) I 1 Manganese

2 3 4 5 s Concentration.rng/l

Fi.46 Heavy metal removal by coffee powder

1 2 3 4 5 Fluoride contemn, rngn

Fig.47 Fluoride removal by d a y