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
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.
UNPLEASANT TASTE AND ODOR
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.
VOLATILE ORGANIC COMPOUNDS
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.
CHLORIDE IONS (CL)
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
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
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
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
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.
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
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 main contamination factors that are examined and
expected to act as microbic indicators are the following:
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.