14 Surface Water Eutrophication in Poland: Assessment and Prevention
331
the lack of sunlight under conditions of high algae concentration can inhibit their
further development [37].
The transparency according to Secchi disc is the oldest and the simplest method
of trophic status assessment. However, this method does not always give an adequate
assessment result, because the turbidity of water may also be caused by other factors
and is not always associated with the concentration of algae. With a large turbidity
of water, the penetrating possibility of sunlight decreases and turbidity may become
a factor inhibiting the development of aquatic vegetation. So, the assessment based
on a set of traditional eutrophication indicators does not guarantee an accurate result.
14.2.3 Integrated Numerical Indicators
An alternative to the approach based on the reference values of traditional eutrophication indices are the integrated numerical indicators, so-called trophic state indexes.
The elaboration of such indexes is based on the established correlation between
the basic factors of eutrophication, such as chlorophyll-a, nitrogen and phosphorus
content, water transparency and other. For each trophic state the reference values
of the indexes are developed. The chosen numerical indexes elaborated by different
authors, that have found wide application in the assessment of water trophic status
in different countries are presented in Table 14.6.
The aggregated indexes were developed by different authors on the basis of various
methodological approaches and assumptions. The data base was the results of longterm monitoring carried out in various water bodies in different geographical regions.
A common feature of the aggregated indexes is that they are based on the established
correlation relationships and, to a greater or lesser extent, consider the key factors of
eutrophication and the water ecosystem response to these factors.
14.3 Eutrophication of Surface Waters in Poland
It is generally recognized, that the main cause of eutrophication is the increased
anthropogenic load of biogenic substances (nitrogen and phosphorus compounds)
introduced into aquatic environment. At the same time, wastewaters, especially
municipal, is considered one of the most dangerous source of nutrients. Therefore, in EU countries and the countries of the Baltic Sea catchment area, particular
emphasis was placed on the elimination of these substances from wastewater. Joining
the European Union Poland committed to fulfil the requirements of Council Directive 91/271/EEC concerning municipal wastewater treatment, therefore in 2003 the
National Program of Municipal Wastewater Treatment (NPMWW) was created [42].
NPMWW contains a list of agglomerations which must be equipped with collective
sewage systems and wastewater treatment plants within the time limits specified in
the Program. Until now, five Program updates have been carried out in 2005, 2009,
331
the lack of sunlight under conditions of high algae concentration can inhibit their
further development [37].
The transparency according to Secchi disc is the oldest and the simplest method
of trophic status assessment. However, this method does not always give an adequate
assessment result, because the turbidity of water may also be caused by other factors
and is not always associated with the concentration of algae. With a large turbidity
of water, the penetrating possibility of sunlight decreases and turbidity may become
a factor inhibiting the development of aquatic vegetation. So, the assessment based
on a set of traditional eutrophication indicators does not guarantee an accurate result.
14.2.3 Integrated Numerical Indicators
An alternative to the approach based on the reference values of traditional eutrophication indices are the integrated numerical indicators, so-called trophic state indexes.
The elaboration of such indexes is based on the established correlation between
the basic factors of eutrophication, such as chlorophyll-a, nitrogen and phosphorus
content, water transparency and other. For each trophic state the reference values
of the indexes are developed. The chosen numerical indexes elaborated by different
authors, that have found wide application in the assessment of water trophic status
in different countries are presented in Table 14.6.
The aggregated indexes were developed by different authors on the basis of various
methodological approaches and assumptions. The data base was the results of longterm monitoring carried out in various water bodies in different geographical regions.
A common feature of the aggregated indexes is that they are based on the established
correlation relationships and, to a greater or lesser extent, consider the key factors of
eutrophication and the water ecosystem response to these factors.
14.3 Eutrophication of Surface Waters in Poland
It is generally recognized, that the main cause of eutrophication is the increased
anthropogenic load of biogenic substances (nitrogen and phosphorus compounds)
introduced into aquatic environment. At the same time, wastewaters, especially
municipal, is considered one of the most dangerous source of nutrients. Therefore, in EU countries and the countries of the Baltic Sea catchment area, particular
emphasis was placed on the elimination of these substances from wastewater. Joining
the European Union Poland committed to fulfil the requirements of Council Directive 91/271/EEC concerning municipal wastewater treatment, therefore in 2003 the
National Program of Municipal Wastewater Treatment (NPMWW) was created [42].
NPMWW contains a list of agglomerations which must be equipped with collective
sewage systems and wastewater treatment plants within the time limits specified in
the Program. Until now, five Program updates have been carried out in 2005, 2009,