safety evaluation of chlorination as a process of...

Chapter-3

Safety Evaluation of Chlorination as a Process of Disinfection

Safety Evaluation of Chlorination as A Process of Disinfection

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3.1 INTRODUCTION

Chlorination is one of many methods that can be used to disinfect water. This

method was first used over a century ago, and is still used today. It is a chemical

disinfection method that uses various types of chlorine or chlorine-containing

substances for the oxidation and disinfection of what will be the potable water

source.

A leading advantage of chlorination is that it has proven effective against

bacteria and viruses; however, it cannot inactivate all microbes. Some protozoan

cysts are resistant to the effects of chlorine. In cases where protozoan cysts are not a

major concern, chlorination is a good disinfection method to use because it is

inexpensive yet effective in disinfecting many other possibly present contaminants.

The chlorination process is also fairly easy to implement, when compared to other

water treatment methods. It is an effective method in water emergency situations as

it can eliminate an overload of pathogens relatively quickly. An emergency water

situation can be anything from a filter breakdown to a mixing of treated and raw

water. Chlorine inactivates a microorganism by damaging its cell membrane. Once

the cell membrane is weakened, the chlorine can enter the cell and disrupt cell

respiration and DNA activity (two processes that are necessary for cell survival).

Chlorination can be done at any time/point throughout the water treatment

process - there is not one specific time when chlorine must be added. Each point of

chlorine application will subsequently control a different water contaminant

concern, thus offering a complete spectrum of treatment from the time the water

enters the treatment facility to the time it leaves. Pre chlorination is when chlorine is

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applied to the water almost immediately after it enters the treatment facility. In the

pre-chlorination step, the chlorine is usually added directly to the raw water (the

untreated water entering the treatment facility), or added in the flash mixer (a mixing

machine that ensures quick, uniform dispersion of the chlorine). Chlorine is added to

raw water to eliminate algae and other forms of aquatic life from the water so they

won’t cause problems in the later stages of water treatment. Pre-chlorination in the

flash mixer is found to remove tastes and odours, and control biological growth

throughout the water treatment system, thus preventing growth in the sedimentation

tanks (where solids are removed from the water by gravity settling) and the filtration

media (the filters through which the water passes after sitting in the sedimentation

tanks). The addition of chlorine will also oxidize any iron, manganese and/or

hydrogen sulphide that are present, so that they too can be removed in the

sedimentation and filtration steps.

Disinfection can also be done just prior to filtration and after sedimentation.

This would control the biological growth, remove iron and manganese, remove taste

and odours, control algae growth, and remove the colour from the water. This will

not decrease the amount of biological growth in the sedimentation cells.

Chlorination may also be done as the final step in the treatment process,

which is when it is usually done in most treatment plants. The main objective of this

chlorine addition is to disinfect the water and maintain chlorine residuals that will

remain in the water as it travels through the distribution system. Chlorinating filtered

water is more economical because a lower CT value is required. This is a

combination of the concentration (C) and contact time (T). The CT concept is

discussed later on in this fact sheet. By the time the water has been through


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sedimentation and filtration, a lot of the unwanted organisms have been removed,

and as a result, less chlorine and a shorter contact time is required to achieve the

same effectiveness. To support and maintain the chlorine residual, a process called

re-chlorination is sometimes done within the distribution system. This is done to

ensure proper chlorine residual levels are maintained throughout the distribution

system.

The chlorination process involves adding chlorine to water, but the

chlorinating product does not necessarily have to be pure chlorine. Chlorination can

also be carried out using chlorinecontaining substances. Depending on the pH

conditions required and the available storage options, different chlorine-containing

substances can be used. The three most common types of chlorine used in water

treatment are: chlorine gas, sodium hypochlorite, and calcium hypochlorite.

Chlorine gas is greenish yellow in colour and very toxic. It is heavier than air

and will therefore sink to the ground if released from its container. It is the toxic

effect of chlorine gas that makes it a good disinfectant, but it is toxic to more than

just waterborne pathogens; it is also toxic to humans. It is a respiratory irritant and it

can also irritate skin and mucus membranes. Exposure to high volumes of chlorine

gas fumes can cause serious health problems, including death. However, it is

important to realize that chlorine gas, once entering the water, changes into

hypochlorous acid and hypochlorite ions, and therefore its human toxic properties

are not found in the drinking water we consume. Chlorine gas is sold as a

compressed liquid, which is amber in color. Chlorine, as a liquid, is heavier (more

dense) than water. If the chlorine liquid is released from its container it will quickly

return back to its gas state. Chlorine gas is the least expensive form of chlorine to

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use. The typical amount of chlorine gas required for water treatment is 1-16 mg/L of

water. Different amounts of chlorine gas are used depending on the quality of water

that needs to be treated. If the water quality is poor, a higher concentration of

chlorine gas will be required to disinfect the water if the contact time cannot be

increased. When chlorine gas (Cl2) is added to the water (H2O), it hydrolyzes rapidly

to produce hypochlorous acid (HOCl) and the hypochlorous acid will then dissociate

into hypochlorite.

Chlorine can be toxic not only for microorganisms, but for humans as well.

To humans, chlorine is an irritant to the eyes, nasal passages and respiratory system.

Chlorine gas must be carefully handled because it may cause acute health effects and

can be fatal at concentrations as low as 1000 ppm. However, chlorine gas is also the

least expensive form of chlorine for water treatment, which makes it an attractive

choice regardless of the health threat.

In drinking water, the concentration of chlorine is usually very low and is

thus not a concern in acute exposure. More of a concern is the long term risk of

cancer due to chronic exposure to chlorinated water. This is mainly due to the

trihalomethanes and other disinfection byproducts, which are by-products of

chlorination. Trihalomethanes are carcinogens, and have been the topic of concern in

chlorinated drinking water. Chlorinated water has been associated with increased

risk of bladder, colon and rectal cancer. In the case of bladder cancer, the risk may

be doubled. Although there are concerns about carcinogens in drinking water, Health

Canada's Laboratory Centre for Disease Control says that the benefits of chlorinated

water in controlling infectious diseases outweigh the risks associated with

chlorination and would not be enough to justify its discontinuation.


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3.1.1 Chlorination Derived By-Products

Chlorine was discovered in 1774 by the chemist Karl Scheele. One of the

first known uses of chlorine for disinfection was not until 1850, when Snow used it

to attempt to disinfect London’s water supply during that now-famous cholera

epidemic. It was not until the early 1900’s, however, that chlorine was widely used

as a disinfectant. Chlorine revolutionized water purification, reduced the incidence

of waterborne diseases across the western world, and “chlorination and/or filtration

of drinking water has been ha iled as the major public health achievement of the

20th century”. Chlorine remains the most widely used chemical for water

disinfection in the United States. However, 1.1 billion people in the world still lack

access to safe drinking water, and new questions about health effects from chlorine

have led to questions about the advisability of using chlorine to provide safe water

for this population. This fact sheet summarizes information about the production,

and health effects, of disinfection by-products (DBPs). In disinfection, gaseous

chlorine (Cl2) or liquid sodium hypochlorite (bleach, NaCl) is added to, and reacts

with, water to form hypochlorous acid. In the presence of bromine, hypobromous

acid is also formed. Both chlorine and bromine are in the “halogen” group of

elements, and have similar chemical characteristics. Hypochlorous and

hypobromous acid form strong oxidizing agents in water and react with a wide

variety of compounds, which is why they are such effective disinfectants. A number

of different by-products can be produced from the reactions in the disinfection

process. By-products created from the reactions between inorganic compounds and

chlorine are harmless and can be easily removed from the water by filtration. Other

by-products, such as chloramines, are beneficial to the disinfection process because

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they also have disinfecting properties. However, there are undesired compounds that

may be produced from chlorine reacting with organic matter. The compounds of

most concern right now are trihalomethanes (THMs) and haloacetic acids (HAAs).

THMs and HAAs are formed by reactions between chlorine and organic material

such as humic acids and fulvic acids (both generated from the decay of organic

matter) to create halogenated organics. A greater level of THM formation has been

found in surface water or groundwater influenced by surface water. Trihalomethanes

are associated with several types of cancer and are considered carcinogenic. The

trihalomethane of most concern is chloroform, also called trichloromethane. It was

once used as an anaesthetic during surgery, but is now used in the process of making

other chemicals. About 900 ppm of chloroform can cause dizziness, fatigue, and

headaches. Chronic exposure may cause damage to the liver and kidneys. Other

harmful disinfection byproducts are: trichloracetic acid, dichloroacetic acid, some

haloacetonitriles, and chlorophenols. Trichloracetic acid is produced commercially

for use as a herbicide and is also produced in drinking water. This chemical is not

classified as a carcinogen for humans, and there is limited information for animals.

Dichloroacetic acid is an irritant, corrosive, and destructive against mucous

membranes. This is also not currently classified as a human carcinogen.

Haloacetonitriles were used as pesticides in the past, but are no longer

manufactured. They are produced as a result of a reaction between chlorine, natural

organic matter, and bromide. Chlorophenols cause taste and odour problems. They

are toxic, and when present in higher Concentrations, affect the respiration and

energy storage process in the body.


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In 1974, Rook discovered that hypochlorous acid and hypobromous acid also

react with naturally occurring organic matter to create many water disinfection

byproducts, including the four primary trihalomethanes:

• Chloroform - CHCl3,

• Bromodichloromethane (BDCM) - CHCl2Br,

• Dibromochloromethane (DBCM) - CHClBr2

• Bromoform - CHBr3.

At the centre of each of the four trihalomethanes is a carbon atom, and it is

surrounded by and bound to four atoms: one hydrogen and three halogens. These

four compounds are collectively termed trihalomethanes and are abbreviated as

either THM or TTHM (for total trihalomethanes).

Rook’s discovery of THMs in drinking water led to research on other

chemicals formed when chlorine is added to water, and to the health effects of these

chemicals. Richardson (2002), identified greater than 600 water disinfection

byproducts in chlorinated tap water, including haloacetic acids (HAAs). THMs, and

to a lesser extent HAAs, are currently used as indicator chemicals for all potentially

harmful compounds formed by the addition of chlorine to water. In many countries

the levels of THMs and HAAs in chlorinated water supplies are regulated based on

this assumption. Humans are exposed to DBPs through drinking-water and oral,

dermal, and inhalational contact with chlorinated water. In populations who take hot

showers or baths, inhalation and dermal absorption in the shower accounts for more

exposure to THMs than drinking water.

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The WHO International Agency for Research on Cancer (IARC)

Classification of THMs

Sl. No Humans Classification

1 Chloroform Inadequate evidence for human carcinogenicity.

Possible human carcinogen

(Group 2 B)

2 Bromodichloromethane

Inadequate evidence for human carcinogenicity

Possible human carcinogen (Group 2B)

3 Dibromochloromethane

Inadequate evidence for

human carcinogenicity

Not classifiable as to its

carcinogenicity in humans

(Group 3)

4 Bromoform Inadequate evidence for

human carcinogenicity

Not classifiable as to its carcinogenicity in humans

(Group 3)

WHO Guideline Values for Trihalomethanes in Drinking Water (WHO, 1996)

Sl. No WHO Guideline Value

1 Chloroform 200 µg/L

2 Bromodichloromethane 60 µg/L

3 Dibromochloromethane 100 µg/L

4 Bromoform 100 µg/L

3.1.2 Water Treatment

Wastewater is defined as “a combination of one or more of: domestic

effluent consisting of black water (excreta, urine and faecal sludge) and grey water

(kitchen and bathing wastewater); water from commercial establishments and

institutions, including hospitals; industrial effluent, storm water and other urban run-

off; agricultural, horticultural and aquaculture effluent, either dissolved or as


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suspended matter. (Raschid-Sally and Jayakody, 2008) The quality of water is

declining steadily and the situation is so bad that it is now necessary to process water

for certain uses for which in the past, no processing was ever considered necessary.

Therefore, highly advanced processes have been introduced for treatment purposes.

The fundamental reasons for treating wastewater is to prevent pollution, thereby

protecting the environment and protecting public health by safeguarding water

supplies and preventing the spread of water-borne diseases, as these ailments are

emerging globally breaking all boundaries.

Globally, about two million tons of sewage, industrial and agricultural waste

are discharged into the world’s precious water resources and at least 1.8 million

children under five years-old die every year from water related disease, or one every

20 seconds (Corcoran et al., 2010).

Adequate wastewater treatment and the disinfection of water supplies has

effectively eliminated these water-borne diseases from developed countries, but they

remain endemic in many parts of the world, especially those regions where

sanitation is poor or non-existent. Adequate wastewater treatment is vital to ensure

that the outbreaks of waterborne diseases that were so prevalent in the eighteenth

and nineteenth centuries do not reoccur.

Rivers are receiving large quantities of treated effluent while estuaries and

coastal waters have vast quantities of partially or completely untreated effluents.

Apart from organic enrichment endangering the flora and fauna due to

deoxygenation, treated effluents rich in oxidised nitrogen and phosphorus can result

in eutrophication problems. Thus, advanced or tertiary wastewater treatment

processes are required to remove these inorganic nutrients to protect rivers and

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lakes. Environmental protection of surface waters is therefore considered as a major

function of wastewater treatment.

Under- dimensioned and aged wastewater infrastructure is already

overwhelmed; the situation is only going to get worse. Without better infrastructure

and management, many millions of people will continue to die every year and there

will be further biodiversity losses and ecosystem resilience depletion, undermining

prosperity and efforts towards a more sustainable future. A healthier future needs

urgent global action for smart, sustained investment for improved wastewater

treatment and management.

Ignorance in managing wastewater not only compromises the natural

capacity of marine and aquatic ecosystems to assimilate pollutants, but also causes

the loss of a whole array of benefits provided by our waterways and coasts that we

too often take for granted; safe water for drinking, washing and hygiene, water for

irrigating our crops and producing our food and for sustaining ecosystems and the

services they provide. The financial, environmental and societal costs in terms of

human health, mortality and morbidity and decreased environmental health are

projected to increase dramatically unless wastewater management is given very high

priority and dealt with due significance.

A wastewater treatment plant is a combination of separate treatment

processes designed to produce an effluent of specified quality from a wastewater

(influent) of known composition and flow rate. The treatment plant is also usually

required to process the separate solids to a suitable condition for disposal. The

amount of treatment required depends largely on the water quality objectives for the

receiving water and also the dilution available.


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Wastewater treatment is essentially a mixture of settlement and biological or

chemical unit processes. The concentrated particles form a sludge that is to be

processed and disposed. Treatment plants are assembled from combinations of unit

processes, and as the range of available unit processes is large, by using suitable

combination of the available processes, it is possible to produce a final, effluent of a

specified quality from almost any type of influent wastewater. The unit treatment

processes can be summarized in five stages:

(i). Preliminary treatment: the removal and disintegration of gross solids, the

removal of grit and the separation of storm water. Oil and grease are also

removed at this stage if present in large amounts.

(ii). Primary (sedimentation) treatment: the first major stage of treatment following

preliminary treatment, which usually involves the removal of settle able solids

which are separated as sludge.

(iii). Secondary (biological) treatment: The dissolved and colloidal organics are

oxidised in the presence of micro-organisms.

(iv). Tertiary treatment: Further treatment of a biologically treated effluent to

remove BOD, bacteria, suspended solids, specific toxic compounds or

nutrients to enable the final effluent to comply with a standard more stringent

than 20:30 before discharge.

(v). Sludge treatment: The dewatering, stabilization and disposal of sludge

(Institute of Water Pollution Control, 1975 and Rae 1998).

The way in which particles settle out of suspension is a vital consideration in

the design and operation of sedimentation tanks, as well as other unit processes.

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There are four types of settling: type I or discrete, type II or flocculent, type III or

hindered which is occasionally referred to as zonal settling, and type IV or

compression settlement. Where particles are dispersed or suspended at a low solids

concentration, then type I or II settlement occurs. Types III or IV settlement only

occurs when the solids concentration has increased to such an extent that particle

forces or particle contact affects normal settlement processes. During settlement, it is

common to have more than one type of settling occurring at the same time and it is

possible for all four to occur in a settlement tank simultaneously (Gray, 2004).

Different water treatment Strategies

Water by its very nature is always pure, since the bond between its hydrogen

and oxygen atoms is extremely strong. The problem is that almost all of the world's

water supply must share space with organic material, chemicals, minerals and

manmade pollutants. The result is often an undrinkable solution, possibly containing

deadly bacteria, viruses and other disease-causing agents. Fortunately, mankind has

developed a number of water treatment methods which make our water supply much

safer for consumption. Not all of these water treatment methods work on a large

scale, but they all render untreated water drinkable to humans.

Perhaps the most basic form of water treatment is called settling. Untreated

water gathered from a natural source can be left undisturbed in a container, allowing

solids to settle out of the solution and fall to the bottom. After enough time has

elapsed, the uppermost level of water can be drawn out for consumption.

This water treatment has several major drawbacks, however. The settling

process can take several days or weeks to be effective, and there is no protection

against bacteria or other organic materials which may not settle out. If the water


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source is relatively clean, such as a mountain stream in remote territory, the settling

method of water treatment may be adequate

A more thorough and faster form of water treatment is the boiling method.

Water should first be filtered through a cloth to remove larger contaminants, then

placed in a clean metal container. Virtually every bacteria or other hazardous life

form will not survive the boiling process, although experts suggest maintaining a

rolling boil for several minutes to ensure success.

Once the water has cooled, it should be safer to drink. One drawback to the

boiling water treatment method is the possibility that inorganic solids may still

remain. Boiling large amounts of water can also be very time-consuming.

One form of water treatment which works on a large scale is chemical

disinfection. Questionable water can be rendered drinkable, if not particularly

flavourful, by the addition of iodine or chlorine-based tablets. Chemical agents

destroy many of the bacteria and other organic contaminants found in natural water

supplies. The water treatment pills carried by hikers and campers usually contain a

form of iodine, although some people with iodine allergies may use chlorine-based

tablets. Chemical water treatment is also the preferred method of swimming pool

operators, since the chlorine kills a number of contaminants brought in through fecal

matter.

For home owners concerned about their public water supplies, another form

of water treatment has become increasingly popular. Filtration through activated

charcoal or paper filters is a low-cost water treatment method used in many private

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homes. Tap water flows through a small filter at the end of a faucet or through a

more elaborate system in the basement or kitchen.

The principle behind the filtration method is that heavy metals, organic

contaminants and many bacteria are simply too large to pass through the mesh of a

filter. The water molecules which do pass through are much more pure, providing a

better tasting product. Filters must be changed regularly to be effective, however.

Bacteria can grow on filters clogged with organic material.

For those who may want an even more discriminating water treatment

method, there is reverse osmosis. Many water treatment companies and bottled

water producers use reverse osmosis along with other methods such as filtration or

ozonation. Reverse osmosis requires the use of a semi-permeable material with

extremely small openings. Untreated water is forced through this membrane, which

prevents even the smallest forms of bacteria and chemical pollutants from passing.

The water molecules themselves actually change in order to pass through the

membrane. The resulting water supply is said to be 'wetter', because the individual

water molecules have fewer sides and are more easily absorbed by the body.

Other forms of water treatment may included ozonation, ionization and

ultraviolet light exposure. Ultraviolet light treatment will destroy the DNA of any

harmful bacteria present in the water, but the cost of installing and operating such a

water treatment system in a home can be prohibitive. Chlorine has a huge variety of

uses; as a disinfectant and purifier, in plastics and polymers, solvents, agrochemicals

and pharmaceuticals, as well as an intermediate in manufacturing other substances

where it is not contained in the final product.


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Chlorine is used worldwide to purify water supply as the ultimate defense

against waterborne microbiological infection. Modern day cholera epidemics in

Peru, China, India or Africa exemplify the devastating consequences of poor

sanitation. Chlorine has a lot of applications. It is used with hygienic purposes and is

indispensable in water treatment, being also used for disinfecting of industrial

residues and pool cleaning. Due to its decolorizing properties it is used in the

whitening of vegetal fibers like cotton, linen etc., and of paper pulp. It is also used in

industrial production of organic compound, like carbon tetrachloride, chlorobenzene,

synthetic glycerin, etc.

Chlorine also plays a critical role in the productions of thousands of

commercial products. Products reliant on chlorine’s unique properties include every

household item such as bleach and disinfectant to bullet-resistant vests, computer

hardware, silicon chips and automotive parts. Chlorine is used in the manufacture if

many car components, including: nylon for car seatbelts and air bags; vinyl

upholstery; bumpers and mats; polyurethane seat cushions; dashboards; fan and

alternator belts; hoses gaskets and seals; petrol additives; brakes and transmission

fluids; and anti-freeze. In aircraft, it plays an important role through titanium in jet

engines and alluminum in fuselages. Chlorinated solvents are also used as

degreasing agents during manufacture of metal components for aircraft engines and

car-braking systems. Around the world, chlorine also plays an important part in

responding to natural disasters, decontaminating public water supplies damaged by

floods, tornadoes and earthquakes. Virtually every part of the home benefits from

chlorine chemistry. In house construction it is used: PVC window frames and

plumbing pipes; insulation; paint (chlorine is commonly used to make titanium

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dioxide, the mon-toxic white pigment used in paints); nylon carpeting; and garden

sprinkler systems. Inside the home, it is used to make a vast range of consumer

products, including toiletries and cosmetics, televisions and compact discs. Because

of its low flammability coupled with high solvency power, the chlorinated dry

cleaning solvent, perchlotoethylene, has become the most widely used fabric and

garment cleaner since it was introduced about 50 years ago. In hospitals, chlorine

compounds help protect patients from infections through their use in cleaning,

disinfection and antiseptics. Chlorine acts as a powerful disinfectant agent when

used either on its own or as sodium hypochlorite. When added to water in minute

quantities, it quichly kills bacteria and other microbes. It has the major advantage of

ensuring clean water right up to the tap, whereas the actions of other sisinfectants-

such as ozone, ultraviolet light and ultrafiltration-is only temporary. In addition to

purifying water, chlorine helps remove tastes and odours, controls the growth of

slime and algae in main pipes and storage tanks, and helps to remove unwanted

nitrogen compounds from water. Thoday, much of the world’s drinking water

depends on chlorinination.

A number of different by-products can be produced from the reactions in the

disinfection process. By-products created from the reactions between inorganic

compounds and chlorine are harmless and can be easily removed from the water by

filtration. Other by-products, such as chloramines, are beneficial to the disinfection

process because they also have disinfecting properties. However, there are undesired

compounds that may be produced from chlorine reacting with organic matter. The

compounds of most concern right now are trihalomethanes (THMs) and haloacetic

acids (HAAs). THMs and HAAs are formed by reactions between chlorine and


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organic material such as humic acids and fulvic acids (both generated from the

decay of organic matter) to create halogenated organics. A greater level of THM

formation has been found in surface water or groundwater influenced by surface

water.

Trihalomethanes are associated with several types of cancer and are

considered carcinogenic. The trihalomethane of most concern is chloroform, also

called trichloromethane. It was once used as an anaesthetic during surgery, but is

now used in the process of making other chemicals. About 900 ppm of chloroform

can cause dizziness, fatigue, and headaches. Chronic exposure may cause damage to

the liver and kidneys. Other harmful disinfection by-products are: trichloracetic acid,

dichloroacetic acid, some haloacetonitriles, and chlorophenols. Trichloracetic acid

is produced commercially for use as a herbicide and is also produced in drinking

water. This chemical is not classified as a carcinogen for humans, and there is

limited information for animals. Dichloroacetic acid is an irritant, corrosive, and

destructive against mucous membranes. This is also not currently classified as a

human carcinogen. Haloacetonitriles were used as pesticides in the past, but are no

longer manufactured. They are produced as a result of a reaction between chlorine,

natural organic matter, and bromide. Chlorophenols cause taste and odour problems.

They are toxic, and when present in higher concentrations, affect the respiration and

energy storage process in the body.

Chlorination is a very popular method of water disinfection that has been

used for many years. It has shown to be effective for killing bacteria and viruses, but

not for some protozoan cysts. With the concern about trihalomethanes, a

carcinogenic disinfection by-product, many communities have become hesitant in

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the continuation of this process. Although chlorination does have some drawbacks, it

continues to be the most popular, dependable, and cost-effective method of water

disinfection.

3.2 REVIEW OF LITERATURE

The quality of drinking-water is a powerful environmental determinant of

health. Assurance of drinking-water safety is a foundation for the prevention and

control of waterborne diseases. The life in aquatic system is largely governed by

physico-chemical characteristics and their stability. Water pollution is a major global

problem which requires ongoing evaluation and revision of water resource policy at

all levels. The specific contaminants leading to pollution in water include a wide

spectrum of chemicals, pathogens, and physical or sensory changes such as elevated

temperature and discoloration. High concentrations of naturally-occurring

substances can have negative impacts on aquatic flora and fauna. Microbiological

contamination of water has long been a concern to the public. Microbial

contamination of drinking water can pose a potential public health risk in terms of

acute outbreaks of disease. The illnesses associated with contaminated drinking

water are mainly gastro-intestinal in nature, although some pathogens are capable of

causing severe and life-threatening illness. Public water systems have been found to

supply drinking water of good quality. Monitoring and corrective measures to

reduce and eliminate levels of contaminants in treated water are essential

components in continuing to assure the safety of drinking water supplies. As the

population grows and more people rely on the drinking water supply from the lakes,

these control measures must be adequate to reduce the risk from exposure to


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microbes. Ultimately, however, source water protection (protection of the raw

waters) is the key to maintaining the good quality of drinking water supplies.

Waste water disinfection is generally considered an important stage of waste

water treatment as it was last barrier for protection and the response of BOD and

COD to chlorination is a function of chlorine dosage and the organic content of the

waste water. Regular monitoring of water quality should be carried out to ensure the

chlorine residual and Coliforms and maintain the recommendations by the agencies

such as EPA (Shaukat et al., 2008)

Faecal contamination of water may lead to higher bacterial load and thereby

subsequent water-borne diseases. It has to be routinely monitored, which help to

reduce the probability of pathogenic population in water that make it suitable for

human consumption.

Disinfection reduces pathogenic microorganisms in water to levels

designated safe by public health standards. This prevents the transmission of disease.

An effective disinfection system kills or neutralizes all pathogens in the water. It is

automatic, simply maintained, safe, and inexpensive. An ideal system treats all the

water and provides residual (long term) disinfection. The use of chlorine to protect

drinking water is one of the greatest public health advances in history. Chlorine

destroys disease-causing organisms in water and is the most commonly-used

disinfectant in all regions of the world. The chlorine residual concentration must be

0.5 mg/l at the entrance into the distribution system and 0.25 mg/l at consumers. The

major problem that occurs as water flows between treatment plant and the consumer is

water quality deterioration because of decrasing the residual chlorine concentration,

especially for long residence times. This can lead to high microbiological

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concentration in water downstream and it is necessary additional treatment with

chlorine (Diana Robescu et al., 2008). Chlorination could remove Faecal Coliforms

very effectively but it has a disadvantage of generating toxic disinfection byproducts

(Anju and Atul, 2007).

The chemical element chlorine is a corrosive, poisonous, greenish-yellow gas

has a suffocating odour and is 21/2 times heavier than air. It belongs to the group of

elements called halogens. Chlorine is used to destroy disease causing-organisms in

water, an essential step in delivering safe drinking water and protecting public

health. Chlorine is by far most commonly used disinfectant in all regions of the

world, where widely adopted, chlorine has helped to virtually eliminate water borne

diseases. Chlorine also eliminates slime bacteria, molds and algae that commonly

grow in water supply reservoirs, on walls of water mains and in storage tanks.

Chlorine is a versatile and low- coast disinfectant appropriate for any size water

system, whether it serves a remote rural village or a large modern city where piped

water supplies are not available, and can also be used for treating water in individual

households. Chlorine is applied to water either as elemental chlorine (chlorine gas)

or through the use of chlorinating chemicals such as calcium hypochlorite or

solutions of sodium hypochlorite. The excessive use of chlorine and leakage of

unused chlorine due to human or mechanical error was a serious threat to

chlorination process (Gangopadhyay, 2007).

More than one billion people do not have access to a safe water supply

within 1 km of their homes, relying instead on unprotected lakes, streams or shallow

wells to meet house hold needs. The chlorine reduce the risk of infectious disease

may account for a substantial portion of cancer risk associated with drinking water


135

One complication that arises in the control of microorganism is the formation of

byproducts during disinfection process. The yields of the reactions for the formation

of THM and non purgeable total organic halide compounds when water is

chlorinated and THM yield increases as the bromide concentration increases in the

river water (Rathbun, 1996). The formation and distribution of THM and halo acetic

acid strongly depended on the chlorination pH value. All the THM species formation

increase with the increase of pH Value except the bromoform that had not been

detected (Li Bo et al., 2008) The byproducts are chemicals that result from the

reaction of chlorine with organic substances in water trihalomethanes (THMs) refer

to one class of disinfection byproducts found in nearly every chlorinated public

water system. The common chlorination byproducts are Chloroform,

Bromodichloromethane, Bromoform, Chloroacetic acid, Dichloroacetic acid, and

Trichloroacetic acid. The natural organic matter (NOM) responsible for THMs

consists of human and fluvic acids production by decaying organic matter. WHO

guideline values for chlorine and trihalomethanes for drinking water quality

2004 are chlorine below 5 milligram per liter (mg/l), Bromodichloromethane-

below 0.06 mg/l, Bromoform-below 0.10 mg/l, chloroform below 0.02 mg/l, and

dibromochloromethane 0.10 mg/l.

3.3 MATERIALS AND METHODS

3.3.1Chlorination

A typical chlorination experiment consisted of dosing different portion of the

sample with varied chlorine amounts and mixing on a multi position magnetic stirrer

for 30 min. A control sample to which no chlorine was added was also processed

similarly. At the end of contact time residual chlorine was measured and a calculated

Chapter 3

136

amount of 0.025 N sodium thiosulphate solution was added for complete

dechlorination. The amount of thiosulphate added was carefully measured to give an

equivalent amount just enough to remove the residual chlorine and avoid any excess

thiosulphate. Then a sampling programme was conducted to investigate the

formation of disinfection byproducts (DBPs) and dissolved organic carbon. Changes

in the concentration of dissolved organic carbon, the Trihalomethanes potential ,

and the halo acetic acid potential in the finished drinking water were evaluated.DOC

was strongly related to DBPs in raw water (Jie- Chung et al., 2010) The formation of

brominated THM which was proved more carcinogenic than there chlorinated

analogues reported was very different at various water qualities. Chlorination

conditions and ratio of bromine consumption on the formation and distribution of

THMs – Br in chlorination. A good correlation between the bromine incorporation

factor and bromine consumption ratio were observed (Huan Wang., 2010). The

formation of chlorine derived byproducts was investigated through bench scale

chlorination experiments with river water was conducted by (Anastasia et al., 2004).

The dissolve organic carbon in the water plays an important role in the formation of

Trihalomethanes in chlorination process. (Xue Shuang et al., 2007)

Chlorination was done by using bleaching powder (Calcium hypochlorite at

different dosage, CDH). The required quantity of bleaching powder was weighted

accurately, and was transferred to a clean dirt free mortar. It was mixed with

accurately measured water sample and made into a paste using a clean pestle. After

adding the remaining water the mixture were filtered through an ordinary filter paper

to remove undissolved bleaching powder. The control also can be filtered in a

similar manner (El- Rehaili, 1995). To 25ml of chlorinated sample 1g KI and 10 ml


137

glacial acetic acid were added and the reaction was allowed to complete. To this

mixture a few drops of 1% of starch solution were added. The mixture was titrated

against 0.025 N sodium thiosulphate and the amount of sodium thiosulphate needed

for complete dechlorination were noted. An equivalent amount just enough to

remove the residual chlorine were added carefully to avoid any excess thiosulphate.

This dechlorinated sample was used for COD determination (El- Rehaili, 1995).

3.3.2 Solvent extraction

Samples after chlorination was subjected to solvent extraction and the

extracted samples were spectroscopically analysed. The samples were collected in

the sterilized cans of 2.5 litters. The different parameters BOD, COD, TOC etc were

analyzed according to the standard methods adopted by APHA and AWWA).

The extracted chlorinated samples were subjected to various spectroscopic

analysis like GC/MS, FT-IR and NMR using standard procedures at STIC, CUSAT,

Cochin.

3.3.3 Total Organic Carbon (TOC)

The supernatant of the chlorinated water samples at different concentration

were subjected to the analysis of Total Organic Carbon (TOC-5000A, Shimaduzu,

Japan). TOC was analyzed at seven day intervals up to twenty one days. A

uninoculated medium was also kept along each trial as control. Analysis was done at

School of Environmental Sciences, Mahatma Gandhi University, Kottayam.

Chapter 3

138

3.3.4 Fourier Transform-Infra Red Spectroscopy (FT/IR)

The structure and chemical changes occurred in the chlorinated water sample

were observed by FT-IR analysis. FT-IR analysis was done at STIC, CUSAT, Cochin.

3.3.5 Gas Chromatography/Mass spectrometry (GC/MS)

The different compounds present in the medium as degradation products

were separated by gas chromatography and later analyzed with their molecular

weight by mass spectroscopy. GC/MS was done at NIIST, RRL, Trivandrum

(Shimadzu varian)

3.3.6 Nuclear Magnetic Rescenence (NMR) Spectroscopy

Nuclear magnetic resonance (NMR) was done at Institute of Intensive

Research In Basic Sciences, Mahatma Gandhi University, Kottayam, Kerala, India.

(NMR 400MHz -Bruker Spectrometer)

3.4 RESULTS

Drinking water treatment plays an important role in maintaining public

health. Chlorine is the most often disinfectant used in the microbiological protection

of water. Chlorine providing high degree of sanitation at a relatively low coast. But

the process ofchlorination is equally harmful as it generates harful CDBs. The high

degree Chlorination results in increase of COD, BOD, and TOC. The effect of high

level chlorination on various parameters of pollution are represented in Table 3.1

The chlorine dosage above 10 mg/l resulted an increase BOD and COD level

of the water sample, and with above 30 mg/l resulted in almost double the original

BOD and COD value. TOC measurement showed obvious stability against chlorine

impact. The DOC was strongly related to DBPs in raw water.


139

The total Coliform content of polluted Pamba river water was extremely

high, and it was 1372±1.5/100 ml. On evaluation of the chlorine dose at

concentrations from 30 mg/L, it was observed that the complete removal of total

Coliform could be achieved at 30 mg/L concentration (Table 3.1, Figure 3.1). As

predicted, there was progressive increase in both BOD and COD. Initial BOD of the

water sample was 15±0.28 mg/L, which got enhanced to 93±0.14 mg/L on

chlorination at 30 mg/L concentration (Figure 3.2). Correspondingly the COD got a

better enhancement from 19±0.04 mg/L to 152±0.62 mg/L at 30 mg/L (Figure 3.3).

However the enhancement of TOC upon chlorination was moderate, it got increased

from 12±0.70 to 26±0.14 on chlorination at 30 mg/L (Figure 3.4).

Table 3.1

Effect of chlorination at different dosage on TC, BOD, COD and TOC of the polluted Pamba river water sample

Chlorine Dose (mg/l) TC(MPN/100 ml) BOD COD TOC

0.0 1372 ± 1.5 15±0.28 19±0.04 12±0.70

5 920±1.6 22±0.14 31±0.56 18±0.14

10 545±1.7 32±0.42 51±0.11 23±0.02

20 61±0.06 47±0.84 86±0.37 23±0.0

30 0±0.0 93±0.14 152±0.62 26±0.14

Chapter 3

140

0

250

500

750

1000

1250

1500

0 5 10 20 30

Chlorine dosage (mg/l)

MP

N/1

00

ml

TC(MPN/100ml)

Fig. 3.1

Effect of chlorination at different dosage on TC of the polluted Pamba river water sample

0

20

40

60

80

100

120

0 5 10 20 30


BO

D (

mg

/l)

BOD

Fig. 3.2

Effect of chlorination at different dosage on BOD of the polluted Pamba river water sample


141

0

20

40

60

80

100

0 5 10 20 30


CO

D (

mg

/l)

COD

Fig. 3.3

Effect of chlorination at different dosage on COD of the polluted Pamba river water sample

0

5

10

15

20

25

30

0 5 10 20 30


TO

C (

mg

/l)

TOC

Fig. 3.4

Effect of chlorination at different dosage on TOC of the polluted Pamba river water sample

Chapter 3

142

The effect of chlorination on the disslved organic matter in the water sample

was evaluated by spectroscopic analysis. The techniques used were FT-IR, GC-MS

and NMR. In all the cases samples before and after chlorination were individually

submitted to spectroscopic analysis. Figure 3.5 represented FTIR of the ether

extracted Pamba river water sample before chlorination (Control).

Fig. 3.5

FT/IR of the ether extracted Pamba river water sample before chlorination - Control


143

Subsequent FT/IR analysis of the samples were done in triplicates to reduce

the error rate and to confirm the functional groups and the structure of the

compounds within the sample. (Fig, 3.5 to Fig. 3.8). Fig. 3.6. Represented the

FT/IR of the ether extracted Pamba river water sample 1 after chlorination. In the

Fig, 3.6 band at 2880 cm-1 indicated Aliphatic CH2, and at 1258 cm-1 indicated

CH2, band at 1100 cm-1 indicated C Cl bond and band at 700 cm-1 indicated the

presence of residual chlorine Cl-.

Fig. 3.6

FT/IR of the ether extracted Pamba river water sample after chlorination – sample 1

Chapter 3

144

Fig. 3.7. represents the FT/IR of the ether extracted Pamba river water

sample 2 after chlorination and Fig. 3.10. represented FT/IR of the ether extracted

Pamba river water sample 3 after chlorination. Representations in Fig. 3.7 and Fig.

3. 8. were also similar to that of Fig. 3.6.

4000.0 3600 3200 2800 2400 2000 1800 1600 1400 1200 1000 800 600 400.0

71.0

72

74

76

78

80

82

84

86

88

90

92

94

96

98

100101.0

cm-1

%T

2954.16

2923.41

2853.81

2343.392297.30

1736.15

1602.62

1455.52

1376.79 1261.07

1216.96

1092.351021.07

802.37

747.32697.74

Fig. 3.7



145

4000.0 3600 3200 2800 2400 2000 1800 1600 1400 1200 1000 800 600 400.0

55.7

60

65

70

75

80

85

90

95

100.8

cm-1

%T

2952.73

2853.03

2354.012344.32

2298.18

1737.60

1602.58

1456.36

1376.63

1217.00810.45

746.09

527.14418.87

Fig. 3.8


The results of the GC/MS of the samples before and after chlorination are

being represented from Fig. 3.9. to Fig. 3.16. Fig.3.9 represented the GC/MS of the

ether extracted Pamba river water sample before chlorination (control) and the Fig.

3.10 represented the GC/MS of the sample 1 after chlorination. MS analysis of the

peak showed molecule weight as 83 which can be compared to the molecular weight

of CH2Cl2.

Chapter 3

146

5.0 7.5 10.0 12.5 15.0 17.5 20.0 22.5 25.0 27.5

0.5

1.0

(x100,000)TIC

50.0 75.0 100.0 125.0 150.0 175.0 200.00.0

25.0

50.0

75.0

100.0

%

44

69402198357 131

50.0 75.0 100.0 125.0 150.0 175.0 200.0 225.00.0

25.0

50.0

75.0

100.0

%

44

40 69222152131

50.0 75.0 100.0 125.0 150.0 175.0 200.00.0

25.0

50.0

75.0

100.0

%

44

121

40 69219131

BC

1 2 3

1

2

3

Fig. 3.9

GC/MS of the ether extracted Pamba river water sample before chlorination control

AS

40.0 45.0 50.0 55.0 60.0 65.0 70.0 75.0 80.0 85.00.0

25.0

50.0

75.0

100.0

%

83

44 6047 6940 8773

5.0 7.5 10.0 12.5 15.0 17.5 20.0 22.5 25.0 27.5

2.5

5.0

7.5

(x10,000)TIC

Fig. 3.10

GC/MS of the ether extracted Pamba river water sample after chlorination- sample 1


147

Fig. 3.11. represented the GC of the ether extracted Pamba river water

sample 2 after chlorination

Fig. 3.11

GC of the ether extracted Pamba river water sample after chlorination- sample 2

Chapter 3

148

Fig. 3.12. represents the MS of the peak obtained at 16.017 in the GC of the

ether extracted Pamba river water sample 2 after chlorination. The molecular peak

ion represented the molecular weight as 155 which corresponded to that of CCl4.

The molecular fragmentation also represented the same,

Fig. 3.12

MS of the peak obtained at 16.017 in the GC of the ether extracted Pamba river water sample after chlorination- sample 2


149

Fig.3.13. represented the MS of the peak obtained at 17.798 min. in the GC

of the ether extracted Pamba river water sample 2 after chlorination. The molecular

ion corresponded to a value of 163 which represented the molecular weight of

CCl3-COOH. The fragmentation also represented the same.

Fig.3.13

MS of the peak obtained at 17.798 min. in the GC of the ether extracted Pamba river water sample after chlorination- sample 2

Chapter 3

150

Fig.3.14. represented the GC of the ether extracted Pamba river water sample

3 after chlorination.

Fig. 3.14

GC of the ether extracted Pamba river water sample after chlorination- sample 3


151

Fig.3.15. represented the MS of the peak obtained at 17.823 min. in the GC

of the ether extracted Pamba river water sample 3 after chlorination.

Fig. 3.15

MS of the peak obtained at 17.823 min. in the GC of the ether extracted Pamba river water sample after chlorination- sample 3

Chapter 3

152

The molecular ion in the MS spectra corresponded to a value of 163 which

represented the molecular weight of CCl3-COOH. The fragmentation also

represented the same.

.

Fig. 3.16

MS of the peak obtained at 19.687 min. in the GC of the ether extracted Pamba river water sample after chlorination- sample


153

The MS of the peak at 19.687 min also represented chlorinated derivatives of

acetic acid preferably trichloroacetic acid.

Fig.3.17. represented the Proton NMR of the ether extracted Pamba river

water sample before chlorination (Control).

Fig. 3.17

Proton NMR of the ether extracted Pamba river water sample before chlorination- Control.

Chapter 3

154

Fig.3.18. represented the C NMR of the ether extracted Pamba river water

sample before chlorination (Control).

Fig. 3.18

Carbon NMR of the ether extracted Pamba river water sample before chlorination- control


155

Fig.3.19. represented the Proton NMR of the ether extracted Pamba river

water sample 1 after chlorination.

Fig. 3.19

Proton NMR of the ether extracted Pamba river water sample after chlorination- sample 1

Chapter 3

156


sample 2 after chlorination.

Fig. 3.20

C NMR of the ether extracted Pamba river water sample after chlorination- sample 2


157


sample 3 after chlorination.

Fig. 3.21

C NMR of the ether extracted Pamba river water sample after chlorination- sample 3

Proton NMR of the sample 1 after chlorination (Figure 3.19) represented

shielding effect at 1.609 representing aliphatic CCl bond which was totally absent in

control (3.18). The CNMR analysis is brought solid evidences for new aliphatic CCl

bond generations. The CNMR analysis of sample 2 represented effects for multiple

CCl bond confirming the presence of poly chlorinated aliphatic compounds which

was totally absent in control (3.17). Similar trend was observed in sample 3 where

there were evidences for more diverse CCl linkages.

Chapter 3

158

3.5 DISCUSSION

The life in aquatic system is largely governed by physico-chemical

characteristics and their stability. Faecal contamination of water leads to higher

bacteria load and subsequent water-borne diseases. The selected indicator organisms

like coliform bacteria, after having routinely monitored, help to indicate the

probability of pathogenic population in water that make it unsuitable for human

consumption (Triebskorn et al., 2002, Sharma and Sarang, 2004: Cunliff and

Nakagomi, 2005).

The most extensively used disinfection method to destroy all coliforms

irrespective of the treatment strategy is chlorination. The chemical element chlorine

is a corrosive, poisonous, greenish-yellow gas has a suffocating odor and is 21/2

times heavier than air. Chlorine is used to destroy disease causing-organisms in

water, an essential step in delivering safe drinking water and protecting public

health. Chlorine is a versatile and low- coast disinfectant appropriate for any size

water system, whether it serves a remote rural village or a large modern city. Where

piped water supplies are not available, and can also be used for treating water in

individual house holds. Chlorine is applied to water either as elemental chlorine

(chlorine gas) or through the use of chlorinating chemicals such as calcium

hypochlorite or solutions of sodium hypochlorite. The serious concern that arises in

the control of microorganism by chlorination is the formation of byproducts during

disinfection process. The byproducts are chemicals that result from the reaction of

chlorine with organic substances in water. Chlorine is a highly reactive gas. Effects

of chlorine on dissolved organic compounds depend on the amount of chlorine that

is present, pH of water sample, temperature of the water and the length and


159

frequency of exposure. The concern about cancer risks associated with chemical

contamination from chlorination byproducts have resulted in numerous

epidermiological studies. These studies generally support the notion that byproducts

of chlorination are associated with increased cancer risks.

The most frequent chlorination derived product is Trihalomethanes.

Ttrihalomethanes (THMs) refer to one class of disinfection byproducts found in

nearly every chlorinated public water system. The other common chlorination

byproducts are Chloroform, dichloro methane, dichloro methane, Chloroacetic acid,

Dichloroacetic acid, and Trichloroacetic acid. The natural organic matter (NOM)

responsible for THMs consists of human and fluvic acids production by decaying

organic matter. WHO guideline values for chlorine and trihalomethanes for drinking

water quality (2004) are chlorine below 5 milligram per liter(mg/l),

Bromodichloromethane-below 0.06 mg/l, Bromoform-below 0.10 mg/l, chloroform

below 0.02 mg/l, and dibromochloromethane 0.10 mg/l.

Studies by different researches questioned the benefits of chlorination against

the deleterious effect that arises from chlorine residuals and from the byproducts of

chlorination. A large number of studies have focused on the soluble volatile organic

content of chlorinated and non chlorinated waste waters using analytical techniques

like GC/MS rather than BOD and COD (Jolley, 1975), (Glaze and Henderson,

1975). The chlorination and its influence on COD, BOD and TOC at the Riyad

Sewage Treatment Plant were extensively studied (EL- Rehaili, 1995). Recent

epidemiological studies have reported association between consumption of

chlorinated drinking water and reproductive and developmental effects.

Chapter 3

160

Concern over the negative aspects of chlorination, especially super

chlorination had emerged n the early 1970 s. This came as a result of the toxicity

residual chlorine to fish and other sensitive aquatic organisms, and due to the

observed production of toxic and carcinogenic compounds such as the

trihalomethanes and other compounds. Several studies in the literature have

examined the history and credibility of water chlorination practices and questioned

the benefits of chlorination against the deleterious effects that arise from chlorine

residuals and by-products on aquatic ecosystems. Chlorine is a strong oxidising

agent and its application for water disinfection is likely to modify the chemical and

biological nature of water, most notably its organic characteristics. The organic

content of water is traditionally measured using lumped parameters such as BOD,

COD and TOC and the chemical identity of organic matter by spectroscopic

analysis.

Despite this environmental concerns super chlorination of organic waste

water is still practised in communities with and without de chlorination before final

discharge. Hence from a public health point of view it is high time to study the ill

effects of chlorination and chlorination derived byproducts.

The present study was undertaken to evaluate the safety aspects of

chlorination in Pamba river water. The Pamba river water is one of the mostly

polluted river system in Kerala and it carries many drinking water reservoir

compartments in the downstream region. Pamba river is also subjected to super

chlorination extensively to avoid the extremely high level of coliform content

consistently present through out the seasons. Hence the Pamba river water was taken

as an ideal sampling system for the evaluation of the safety aspects of chlorination.


161

On evaluation of the minimum dose of chlorination it was observed that 30

mg/l dose was the minimum dose required for complete removal. The dosage of

30 mg/l is extremely high concentration and could be considered as super

chlorination. Any dose less than 30 mg /l resulted in a residual coliform level. (Table

3.1, Fig. 3.1 to 3.4).

However along with the increase in the dosage of chlorination there was

progressive increase in COD and BOD. 10 mg/l dosage of chlorine resulted in

doubling of BOD where COD became three times.30mg/l dosage of chlorine

enhanced BOD by six times and COD by eight times. The increase in TOC on

chlorination was moderate and was from 12± 0.70 mg/l to 26 mg/l ±0.14 mg/l. All

these results clearly indicated the increase in the oxidisible organic load upon

chlorination. Chlorination results in the generation of more recalcitrant compounds.

The polluted water sample carried many dissolved organic compounds which on

chlorination got chlorinated resulting in the formation of more recalcitrant

chlorinated organic compounds. These chlorination derived byproducts were

responsible for the increase in BOD and COD during chlorination. The

biodegradability of the increased organic load in a contaminated water sample is

often calculated on the basis of BOD to COD ratio. Here the ratio was 0.789 in the

case of contaminated non chlorinated water. The BOD/COD ratio got reduced to

0.611 upon 30 mg/l chlorination. This clearly suggested the decreased

biodegradability of the increased organic nature of the water sample on chlorination.

Chlorination of organic compounds resulted in the generation of more recalcitrant

chlorinated derivatives contributing to less BOD/COD ratio. Decrease in the

Chapter 3

162

biodegradability induced by chlorination holds ample evidence for the stable and

toxic byproducts of chlorination.

As mentioned above, the nature of these products depend upon the extent of

chlorination, contact time, pH, temperature, presence of other contaminats and also

the nature of the organic compounds already dissolved in the water sample. It was

extremely difficult to trace all the components presence in the river water sample

particularly after chlorination where the type of the organic representation was much

diverse. However in the present investigation an attempt was made to establish the

presence of specific chlorination derived byproducts in the chlorinated water sample

.However no attempt could be made to quantify the amount of these contaminants.

The spectroscopical analysis was done for three chlorinated water samples

and was compared with that of the control,ie with unchlorinated water sample. All

the spectroscopical data supported the presence of various types of new - C-Cl

linkages being initiated during chlorination process (Fig.3.5 to 3.21).

The FT/IR data of the chlorinated samples gave strong evidence for the

presence of new C-Cl bonds in alkanes being represented by the bands in the region

of 2880 cm-1, 1288 cm-1, 1100 cm-1 and 700 cm-1. The analysis of the three samples

could bring sufficiently consistent representation regarding the presence of

chlorinated alkanes.

The presence of chloromethanes and chloro acetic acids were confirmed by

GC/MS analysis. The GC/MS analysis of the first chlorinated sample came out with

strong representations regarding the presence of CH2Cl2 after chlorination. This

result exactly complemented the earlier results of FT/IR and established the


163

formation of dichloromethane on chlorination of the contaminated water sample.

The GC/MS analysis of the subsequent samples gave strong evidences for the

presence of trichloro acetic acid and carbon tetra chloride.

NMR analysis was done to establish the generation of new C-Cl bonds .Both

proton and carbon NMR were done for the control .However carbon NMR could be

done for only second and third sample. The first sample analysis was done with only

proton NMR. The NMR analysis represented the new generation of C-Cl bonds

including the electrical field effects of C-Cl.

As treatment of the Pampa river water necessitated complete removal of

coliforms to avoid any possible outbreak of pathogens, chlorination at a minimum

dosage of 30mg/l is unavoidable. But this superchlorination resulted in increased

COD and BOD and decreased biodegradability. This elevated recalcitrance could be

attributed to the presence of chlorinated organic compounds specifically,

dichloromethanes, carbon tetrachloride, and trichloroacetic acids. It followed that

chlorination, the strategy adopted for the complete elimination of coliforms resulted

in more threatening situation contributing to carcinogenic and toxic chlorinated

compounds instead of coliforms. This is of much importance as chlorination is often

accepted as the most widely accepted and sometimes only the single method of

water treatment. The awareness about the toxic effects of chlorination has not drawn

the public attention yet, The government and the local bodies implementing these

treatment strategies should be properly educated about the toxic effects of

chlorination. At the same time it is high time for the various technical and scientific

communities of the society to come forward with new, effective and safely

acceptable solutions for the treatment of polluted water systems.

safety evaluation of chlorination as a process of...

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