152
These are sewage containers with permeable sides
from which sewage could filtrate into the groundwater and only the solid remnants are transported
away every so often. In developed countries this
type of sewage handling is generally no longer permitted, only insulated sewage containers can be
installed that has to be “sucked” regularly.
Municipal sewage contains a wide range of
pollutants. Pathogens (bacteria, fungi, viruses) are
always present the life of which is only longer if
they find hosts in aquatic organs. Shells are very
dangerous regarding this. They caused typhus and
cholera epidemics in Naples in 1979 because people ate them raw. Water from household water
drainage networks contains urine, faeces, detergents and bathing chemicals and dishwater.
Depending on the industrialisation of the given
settlement industrial sewage with a very variable
composition enters the public drainage network if
not treated separately. Regarding industrial pollutants, heavy metal compounds are especially dangerous since they could cause poisoning even in
very small concentration. One compound of mercury, methylmercury (causing Minamata disease
that is a mercury poisoning) and cadmium (causing itai-itai disease) are considered among the
most dangerous ones. Sewage from milk factories,
butcheries and hospitals contains a wide range of
organic contamination making the composition of
municipal sewage even more complex.
All materials that were discussed above flow
into rivers or lakes without any change if the
given settlement has no sewage treatment plants
or these apply only mechanical filtering which is
frequently the case in poorer countries.
Fortunately the receptive living waters have a
certain natural self-purification potential. This
means that external material in the water are
taken, transformed and degraded into simple,
harmless compounds by aquatic organs and in
this way the ecological system of the river is not
damaged. There is a limit, however, to this selfpurification potential which depends on several
factors. In the case of rivers, aquatic life and discharge are decisive. If the discharge of a river is
much higher than the amount of sewage released
into the river the latter may become diluted in
such a grade that the water cannot be regarded
polluted. If the sewage of a great city, however, is
released into a stream with small discharge it will
not be able to purify on its own, no matter how
rich its life is. In such cases sewage frequently
destroys life in small discharge streams. As a
consequence the most polluted rivers and lakes
can be found where many populous settlements
develop along or around them and sewage treatment was not raised to the adequate level.
Intensively cultivated agricultural areas are
also major pollution sources since great amount
of fertilisers and pesticides could be washed into
surface and subsurface waters from their area.
Manure from cattle farms could also pollute living waters if not treated properly. Considering
major rivers Ganges is strongly polluted with
around 600 million people living in its catchment
area and the infrastructure of the surrounding
settlements is poor with municipal sewage flowing untreated into the river in many places.
Much less people live along Volga River (61
million people in the settlements along the river)
but a lot of industrial plants were established
here that using not too developed technologies
and environmental regulations are not strict
either. Sewage treatment in most settlements
along the river has much room for improvement.
As a result, water of this river is also polluted.
Industrial hazards frequently cause very
severe ecological consequences, one is presented
in Box 4.7.
Box 4.7 Cyanide Catastrophe in the Tisza
River (Romania–Hungary)
Pollution in the Tisza River is rather regular
from the number of pollution sources in its
catchment area. The extent of pollution, however, did not threaten the complete destruction of life in the river until January 2000. On
30th January 2000 the dam of the purifier of
the Romanian–Australian company, Aurul at
Săsar (Romania) broke through due to
extreme precipitation and cyanide containing
water flew into the Lápos Stream and via the
Szamos River into the Tisza (in Hungary).
According to estimates, 100,000 m
3
of cyanide containing water entered the water sys4 Changes on Earth as a Result of Interaction Between the Society and Nature
These are sewage containers with permeable sides
from which sewage could filtrate into the groundwater and only the solid remnants are transported
away every so often. In developed countries this
type of sewage handling is generally no longer permitted, only insulated sewage containers can be
installed that has to be “sucked” regularly.
Municipal sewage contains a wide range of
pollutants. Pathogens (bacteria, fungi, viruses) are
always present the life of which is only longer if
they find hosts in aquatic organs. Shells are very
dangerous regarding this. They caused typhus and
cholera epidemics in Naples in 1979 because people ate them raw. Water from household water
drainage networks contains urine, faeces, detergents and bathing chemicals and dishwater.
Depending on the industrialisation of the given
settlement industrial sewage with a very variable
composition enters the public drainage network if
not treated separately. Regarding industrial pollutants, heavy metal compounds are especially dangerous since they could cause poisoning even in
very small concentration. One compound of mercury, methylmercury (causing Minamata disease
that is a mercury poisoning) and cadmium (causing itai-itai disease) are considered among the
most dangerous ones. Sewage from milk factories,
butcheries and hospitals contains a wide range of
organic contamination making the composition of
municipal sewage even more complex.
All materials that were discussed above flow
into rivers or lakes without any change if the
given settlement has no sewage treatment plants
or these apply only mechanical filtering which is
frequently the case in poorer countries.
Fortunately the receptive living waters have a
certain natural self-purification potential. This
means that external material in the water are
taken, transformed and degraded into simple,
harmless compounds by aquatic organs and in
this way the ecological system of the river is not
damaged. There is a limit, however, to this selfpurification potential which depends on several
factors. In the case of rivers, aquatic life and discharge are decisive. If the discharge of a river is
much higher than the amount of sewage released
into the river the latter may become diluted in
such a grade that the water cannot be regarded
polluted. If the sewage of a great city, however, is
released into a stream with small discharge it will
not be able to purify on its own, no matter how
rich its life is. In such cases sewage frequently
destroys life in small discharge streams. As a
consequence the most polluted rivers and lakes
can be found where many populous settlements
develop along or around them and sewage treatment was not raised to the adequate level.
Intensively cultivated agricultural areas are
also major pollution sources since great amount
of fertilisers and pesticides could be washed into
surface and subsurface waters from their area.
Manure from cattle farms could also pollute living waters if not treated properly. Considering
major rivers Ganges is strongly polluted with
around 600 million people living in its catchment
area and the infrastructure of the surrounding
settlements is poor with municipal sewage flowing untreated into the river in many places.
Much less people live along Volga River (61
million people in the settlements along the river)
but a lot of industrial plants were established
here that using not too developed technologies
and environmental regulations are not strict
either. Sewage treatment in most settlements
along the river has much room for improvement.
As a result, water of this river is also polluted.
Industrial hazards frequently cause very
severe ecological consequences, one is presented
in Box 4.7.
Box 4.7 Cyanide Catastrophe in the Tisza
River (Romania–Hungary)
Pollution in the Tisza River is rather regular
from the number of pollution sources in its
catchment area. The extent of pollution, however, did not threaten the complete destruction of life in the river until January 2000. On
30th January 2000 the dam of the purifier of
the Romanian–Australian company, Aurul at
Săsar (Romania) broke through due to
extreme precipitation and cyanide containing
water flew into the Lápos Stream and via the
Szamos River into the Tisza (in Hungary).
According to estimates, 100,000 m
3
of cyanide containing water entered the water sys4 Changes on Earth as a Result of Interaction Between the Society and Nature