God created 91 chemical Elements,man 15

and the devil just 1:Chlorine.

(Oto Huntsinger-Famous Austrian Chemist).


Chlorine was discovered in 1774 by the Swedish chemist

Carl Scheele.

It is symbolized as CL.

Its name comes from the Greek word  Chloros=Green.

It is produced by electrolyzing water to salt.

Hypochlorous Natrium (Hypochlorous Acid) is the main

disinfectant chemical of water.

The ions of chlorine destroy any micro-organisms with the

reaction of their cellular walls.

Chlorine as a gas has been used in the past in many wars

with tragic results.

The presence of Chlorine in water is necessary in order

to characterize drinking water as micribiologically safe.

In chlorination of water we follow the general rule-

we prefer the least harm(presence of controlled chlorine

doses) to the greatest harm (presence of microbic charge

in drinking water).

One of the most important consequences of chlorination

is that its reaction with the proteins of micro-organisms

creates the chloramines.

By-products of chlorination when reacting with the organic

carbon existing in water are:


Dibromochloromethane and Bromodichloromethane.

The total content of Trihalomethane in drinking water

must not exceed 100mg/l.




The color is not compatible with drinking water.It may be

due to either inorganic substances or to colloidal and

dissolved organic substances.The color in drinking water

does not necessarily mean danger for the human health.

It is very possible that discoloration is quite often

attributed to maintenance works done in the distribution

nets of drinking water.

It might also be there due to the presence of dissolved

colouring substances,either vegetable from plant roots

or inorganic (such as salt,iron from corrosion of the





Turbid water must definitely be checked for pollution.

In drinking water,the measurement of turbidity is one

of the most significant parameters to define water quality.

The desired level of turbidity in drinking water is <5NTU.

When using the term turbidity we mean the absence of

clearness in water.More specifically,turbidity is the water

resistance to light passing and it happens mainly due to

the existence of fine-grained particles,inorganic and

organic materials,which either float or are in colloidal

and are scattered in the liquid phase of water.

The biggest problem with turbidity is the fact that it

renders chlorination ineffective.




Every water has its own special and unique taste.

The unpleasant taste that is usually accompanied with

bad odor is caused in drinking water by several chemical

substances,as well as dissolved organic materials.

Still,we cannot exclude the fact that it may also be caused

by either the presence of micro-organisms or dissolved

gases in the water.A large concentration of dissolved

solids(TDS) over 1000mg/l can also cause a problem of

bad taste in drinking water.The concentration of the

Total Dissolved Solids had better not exceed 500mg/l;

this would not of course mean that an even larger

concentration would be considered as a pollutant.

Some dissolved salts such as ,for example,Magnesium

Chloride(MgCl2) can cause a bad taste and odor problem

in drinking water.However,what most people recognise as

bad taste and odor is the residual Chlorine in water.

Still,the biggest problem with chlorination is the

compounds created by the reaction of Chlorine with the 

organic materials of water.Such compounds are 

Chloroform and others known as chlorinated

hydrocarbons (THM's).Water with too intense taste

and odor should be checked for any pollutants.




Under the general terminology Volatile Organic

Compounds (VOC'S) a large and particularly harmful

group of drinking water pollutants is included such as

pesticides,weed-killers,dissolvers,free monomerics etc.

They come from industrialization in big cities and intensive

agriculture in rural areas.The pollution of water caused by

Volatile Organic Compounds is nowadays very common

and is also a problem that is constantly deteriorating.A

variety of facts may allow them to enter water.For

instance,benzole can enter drinking water from a leakage

in underground fuel tanks like petroleum or gasoline.

Dichloromethane is,for example,a dissolver used

extensively in industries and can end up in drinking water

through industrial waste.Trichloroethylene is used in

chemical industries as a component in cleaning products.

The contamination of drinking water from the usage of

pesticides and weed-killers in agricultural areas is also

very widespread.Chloramination of water itself creates

by-products which are even more dangerous than

chlorine itself.Unfortunately,the list of Volatile Organic

Compounds (VOC'S) is long and endless.The pollution

caused by them is almost everywhere and it is one of 

the problems that will keep on aggravating in the future. 




In large amounts in drinking water Chloride ions give

brackish or bitter taste.In areas close to the sea they

are probably easy to come into drinking water through

sea water.In other cases Chloride ions mainly come from

the corrosion of rocks and stones.However, they can also

be found in water because of the usage of fertilizers,

waste and industrial waste.They are usually chemical

compounds such as Sodium Chloride (NaCl),Potassium

Chloride (KCl),Calcium Chloride (CaCl2)and Magnesium

Chloride (MgCl2).

They do not have any direct impact on human health.

Their highest parametric level is defined at 250 mg/l.




We use this term in general for Sodium Sulphate,

Calcium Sulphate and Magnesium Sulphate.If their

concentration is over 700mg/l they can cause bad

or unpleasant taste in drinking water.The main sourse

of Sulphurous Ions is rain.They may also come from

sedimentary rocks that contain Calcium Sulphate or

Silicon Sulphate.

Their highest parametric level is defined at 250mg/l.




Nitrates are the last stage of oxidization of Ammonia

in water and their detection in drinking water must be

confronted immediately.They are mainly found in drinking

water because of fertilizers in agricultural cultivations,but

they may also come from human waste.Nitrates are and

will be,even more in the future,the biggest problem of

water pollution.Nitropollution is a whip that is constantly


Their highest parametric level is defined at 50mg/l.




Ammonium Ions are most often a sign of drinking water

pollution by waste substances.Yet,sometimes pollution 

can be caused due to minerals.They can cause a bad

taste and odor in drinking water .The biggest problem 

they cause though,is that they render the chlorination

of water ineffective.

Their highest parametric level is defined at 0,5mg/l. 




Fluoride exists in water in the form of dissolved fluoride

salts.In small amounts up to 1mg/l they are considered

to be beneficial for the human health.Amounts of fluorides

are most commonly found in underground waters rather

than in surface water.

Their highest parametric level is defined at 1,5mg/l.




Lead is extensively used in industries,therefore it is one

of the Heavy Metals which is widely scattered in the

environment.Its presence in water is a huge problem

since it is one of the most toxic metals.The corrosion

of lead hydraulic installations allows Lead to enter

drinking water and pollute it.However,its presence in

water can be due to industrial pollution.Lead in small

amounts exists in all natural sources of water.In recent

years the use of lead as an additive to gasoline to

increase the octane rating number,as well as its use in

several insecticides and pigments have worsened the

problem to a high level.This issue causes a huge alarm

considering the fact that Lead acts accumulatively in the

human organism.

Its highest parametric level is defined at 100mg/l.




Its name comes from the Greek word <Chroma=Color>.

We meet Chromium in drinking water in two forms.As

Trivalent Chromium and Hexavalent Chromium.The

biggest problem regarding drinking water is Hexavalent

Chromium (CR6+) and this is what we see almost

exclusively,because the salts of Hexavalent Chromium

are easily dissolved in water.Haxavalent  Chromium

usually contaminates surface water and this contamina-

tion comes therefore from metallurgic and metallizing

industries. Any contamination by Hexavalent Chromium

must be treated immediately,because their compounds

are extermely toxic and cause mutations in the human


Its highest parametric level is defined at 50mg/l.




Significant amounts of Copper are dissolved in drinking

water by the corrosion of copper pipes in water supply

nets.If the water stays stagnant in the pipes for many

hours the concentration of Copper in drinking water

could exceed 20mg/l.Copper in big concentrations

slightly colours drinking water and gives it a sour taste.

Its highest parametric level is defined at 2 mg/l.




Arsenic is a notorious poison.

Concentrations of Arsenic over the allowed limits in

drinking water are found in many areas in Greece and

all over the world.The natural sources of Arsenic are the

volcanic rocks,but it can also come from the decompo-

sition of vegetable organic matter.There are two forms

of Arsenic.The first form is the Pentavalent Arsenic and

the second and most toxic is the Trivalent Arsenic.

The biggest problem in drinking water is the Trivalent

Arsenic which is extermely dangerous and carcinogenic.

Most natural waters contain Arsenic in concentrations

usually over 5mg/l.

Its highest parametric level is defined at 10mg/l.




Mercury can enter drinking water as a waste of Chemical

Industries,since it is widely used in Electrical Equipment

Industries,in the production of colors,in Paper Industries

and in the Fungicide production.Inorganic Mercury is toxic

but not as much as organic Mercury,especially in the form

of Methylmercury(CH3Hg+).

Its highest parametric level is defined at 1mg/l.




Cadmium derives mainly from industrial waste and 

corrosed galvanized pipes.In soft water with low PH

concentrations of Cadmium can be found,because these

waters are more corrosive than others.Cadmium is one of

the most toxic metals.Contamination by Cadmium in

drinking water must be treated immediately.

Its highest parametric level is defined at 5mg/l.


IRON  (Fe)


Its name comes from the latin word Ferrum.

Water contamination by Iron is found mainly in deep

underground waters that go through rocks rich in Iron.

Even a small amount of Iron in drinking water gives a

bad taste when consumed.An even bigger problem than

that is the development of bacteria in drinking water with

Iron concentrations.Surface waters usually contain no

dissolved Iron.

Its highest parametric level is defined at 200 mg/l.




High concentation of Manganese in water gives a rather

unpleasant and bitter taste whilst colouring drinking water

light yellow.Manganese is considered to be one of the

least toxic elements in water quality.The problem

regarding Manganese is that its presence enables the

development of micro-organisms which increase turbidity.

Its highest parametric level is defined at 50mg/l.




Asbestos can enter drinking water through the asbestos

pipes,which have been used widely in the past in water

supply nets.Many scientific studies have repeatedly

confirmed that Asbestos can cause serious damages to

human health mainly when <Airborne Asbestos>is

inhaled.After a long lasting period of studies in the U.S.A.

and the U.K. it has now been proved ,I would say in 

absolute certainty,that drinking water does not contain

a larger amount of Asbestos Fibers than in its natural 

form in nature,where Asbestos can be also found in the

corrosion of rocks and stones.

The World Health Organization (WHO) does not set any

higher parametric level for Asbestos in drinking water.




For centuries microbial charge has been the biggest

problem for humanity.

Nowadays,by applying chlorination to drinking water

this problem has eliminated.Epidemics that were caused

by pathogen microbs and had waste sources belong to

the past.

The main contamination factors that are examined and

expected to act as microbic indicators are the following:


Total Coliforms

Faecal Coliforms

Faecal Streptococci


Measurement of Total Bacteria in drinking water


The discovery of each one of the above categories gives

close enough important information for the kind of 

contamination in drinking water.

Total Coliforms may either come from human or animal

waste,or from the ground and plants.

Faecal Coliforms come from the digestive system of

humans and animals.Escherichia Coli is the most repre-

sentative part of this group.

Faecal Streptococci because of their resistance to

chlorination must be checked thoroughly.

Chlostridium are sporogonial bacteria that survive in

adverse conditions and appear to have a big resistance

to chlorination.Their detection is of great importance in

order to reassure the best quality of drinking water.

The measurement of the Total Bacteria gives us a full

image of the microbiological cleanliness of water especially

when it is destined to be provided for human consumption

and food industries.It is very important every time we 

have measurements that they appear to have stable

numbers instead of big fluctuations.

In their overwhelming majority the Authorities today

reassure that chlorination of drinking water is done

properly by modern chlorinators and water is distributed

to consumers absolutely safe. 












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