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You are here: Home / Data and maps / Indicators / Oxygen consuming substances in rivers / Oxygen consuming substances in rivers (CSI 019) - Assessment DRAFT created Sep 2013

Oxygen consuming substances in rivers (CSI 019) - Assessment DRAFT created Sep 2013

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Topics:

Water Water (Primary topic)

Tags:
soer2010 | freshwater | csi | freshwater quality | bod5 | ammonium | water | thematic assessments | rivers
DPSIR: State
Typology: Descriptive indicator (Type A - What is happening to the environment and to humans?)
Indicator codes
  • CSI 019
Geographic coverage:
Albania Austria Belgium Bulgaria Cyprus Czech Republic Denmark Estonia Finland France Germany Greece Hungary Iceland Ireland Italy Latvia Liechtenstein Lithuania Luxembourg Macedonia (FYR) Malta Netherlands Norway Poland Portugal Romania Slovakia Slovenia Spain Sweden Switzerland United Kingdom
 
Contents
 

Key policy question: Is organic matter and ammonium pollution of rivers decreasing?

Key messages

Concentrations of BOD and total ammonium have decreased in European rivers in the period 1992 to 2011 (Fig. 1), mainly due to general improvement in wastewater treatment.

See also WISE interactive maps: Mean annual BOD in rivers and Mean annual Total Ammonium in rivers

Biochemical Oxygen Demand (BOD5) and total ammonium concentrations in rivers between 1992 and 2011

Note: Concentrations are expressed as annual mean concentrations. Only complete series after inter/extrapolation are included (see indicator specification). The number of river monitoring stations included per country is given in metadata (see downloads and more info). BOD7 data has been recalculated into BOD5 data. If data on total ammonium are not available, data on ammonium are included into the data series.

Data source:
Downloads and more info

BOD5 concentrations in rivers between 1992 and 2011 in different geographical regions of Europe

Note: The data series per region are calculated as the average of the annual mean for river monitoring stations in the region. Only complete series after inter/extrapolation are included (see indicator specification). The number of river monitoring stations included per geographical region is given in parentheses. BOD7 data has been recalculated into BOD5 data.

Data source:
Downloads and more info

Total ammonium concentrations in rivers between 1992 and 2011 in different geographical regions of Europe

Note: The data series per region are calculated as the average of the annual mean for river monitoring stations in the region. Only complete series after inter/extrapolation are included (see indicator specification). The number of river monitoring stations included per geographical region is given in parentheses. If data on total ammonium are not available, data on ammonium are included into the data series.

Data source:
Downloads and more info

BOD5 concentrations in rivers between 1992 and 2011 draining to different sea regions of Europe

Note: The sea region data series are calculated as the average of annual mean data from river monitoring stations in each sea region. The data thus represents rivers or river basins draining into that particular sea. Only complete series after inter/extrapolation are included (see indicator specification). The number of river monitoring stations included per sea region is given in parentheses. There were no stations with consistent data series on BOD7 in rivers draining to the Arctic Ocean. BOD7 data has been recalculated into BOD5 data.

Data source:
Downloads and more info

Total ammonium concentrations in rivers between 1992 and 2011 draining to different sea regions of Europe

Note: The sea region data series are calculated as the average of annual mean data from river monitoring stations in each sea region. The data thus represents rivers or river basins draining into that particular sea. Only complete series after inter/extrapolation are included (see indicator specification). The number of river monitoring stations included per sea region is given in parentheses. If data on total ammonium are not available, data on ammonium are included into the data series.

Data source:
Downloads and more info

Key assessment

Introduction

Biochemical Oxygen Demand (BOD) and total ammonium, are key indicators of organic pollution in water. BOD shows how much dissolved oxygen is needed for decomposition of organic matter present in water. Concentrations of these parameters normally increase as a result of organic pollution caused by discharges from waste water treatment plants, industrial effluents and agricultural run-off. Severe organic pollution may lead to rapid de-oxygenation of river water, a high concentration of ammonia and the disappearance of fish and aquatic invertebrates.

The most important sources of organic waste load are: household wastewater; industries such as paper industries or food processing industries; and silage effluents and manure from agriculture. Increased industrial and agricultural production, coupled with a greater percentage of the population being connected to sewerage systems, initially resulted in increases in the discharge of organic waste into surface water in most European countries after the 1940s. Over the past 15 to 30 years, however, the biological treatment (secondary treatment) of waste water has increased, and organic discharges have consequently decreased throughout Europe. See also CSI 024: Urban waste water treatment.

Overall trend in BOD and total ammonium (Fig. 1)

In European rivers, the oxygen demanding substances measured as BOD and total ammonium have decreased by 53 % (from 4.0 mg/l to 1.9 mg O2/l) and 75 % (from 473 to 119 µg N/l), respectively, from 1992 to 2011 (Fig. 1). The decrease is due mainly to improved sewage treatment resulting from the implementation of the Urban Wastewater Treatment Directive and national legislations. The economic downturn of the 1990s in central and eastern European countries also contributed to this fall, as there is an ongoing decline in pollution from manufacturing industries. This suggests that either further improvement in wastewater treatment is required or that other sources of organic pollution, for example from agriculture, require greater attention, or both.

Overall there has been a significant decrease in BOD concentrations at 60.1 % of the river stations (an additional 5.6 % marginally significant) between 1992 and 2011, while there has been a significant increase at only 3.3 % of the stations (an additional 0.7 % marginally significant). Similarly, there has been a significant decrease in total ammonium concentrations at 55.0 % of the stations (an additional 6.8 % marginally significant), while there has been a significant increase at only 2.3 % of the stations (an additional 1.1 % marginally significant).

BOD and total ammonium time series and trends per geographical regions (Fig. 2 and Fig. 3)

The largest proportion of monitoring stations with significant or marginally significant negative trend in BOD is found for the western and the southern European rivers, while the lowest proportion is found for the northern European rivers. Based on the sum of significant and marginally significant trends, the trends for the rivers in different geographic regions are:

  • West: 74.7 % negative, 0.9 % positive, and 1.52 mg O2/l average decrease;
  • South: 76.1 % negative, 0 % positive, and 3.99 mg O2/l average decrease;
  • East: 55.5 % negative, 9.5 % positive, and 1.14 mg O2/l average decrease;
  • Southeast: 52.1 % negative, 5.2 % positive, and 2.28 mg O2/l average decrease;
  • North: 46.7 % negative, 6.7 % positive, and 0.19 mg O2/l average decrease.


Countries with more than 60 % of the stations with negative trend in BOD are Austria, Bulgaria, the Czech Republic, Denmark, France, Ireland, Luxembourg, Slovakia, Slovenia, Spain and the United Kingdom.

The decrease of total ammonium from 1992 to 2011 is the largest in the southern (82 %) and eastern European rivers (78 %), closely followed by the decrease in the western European (75 %) and southeastern European rivers (74 %) (Fig. 3).

The concentrations in Eastern European rivers, as assessed for the period 1992-2011 (around 80 µg N/l), are significantly lower than those in the previous assessment (made in 2012, for the period 1992-2010: around 200 µg N/l). The reason is that in 1992-2010 assessment data for 96 monitoring stations in Poland were included, whereas in 1992-2011 assessment, only four stations in Poland are included. Monitoring stations in Poland had an important impact on the assessment of indicator for the Eastern European geographical region as a whole. The same difference can be observed for the South European region due to larger number of river monitoring stations in Spain included in the assessment, which are at the same time the only stations representing South European region (82 % decrease in 1992-2011 period, compared to 20 % decrease in 1992-2010 period). Southeastern and western European rivers also saw significant decrease in total ammonium concentrations (both around 75 %), however southeastern European rivers still have the highest total ammonium concentrations in Europe (around 300 µg N/l).

The largest proportion of monitoring stations with significant or marginally significant negative trend in total ammoniumis found for the western and southeastern European rivers, while the lowest proportion is found for the northern European rivers as follows (sum of significant and marginally significant trends):

  • West: 76.3 % negative, 2.4 % positive, 296 µg N/l average decrease through the whole period;
  • East: 64.2 % negative, 0.8 % positive, 201 µg N/l average decrease; 
  • Southeast: 74.2 % negative, 3.4 % positive, 785 µg N/l average decrease; 
  • South: 52.1 % negative, 0 % positive, 384 µg N/l average decrease; 
  • North: 30.5 % negative, 8.4 % positive, 10 µg N/l average decrease.


Countries with more than 60 % of the stations with negative trend in total ammonium are the former Yugoslav Republic of Macedonia, Slovenia, the United Kingdom, Germany, Lithuania, Ireland, Poland, Bulgaria, France, Austria, Luxembourg, Belgium and Norway.

BOD and total ammonium time series and trends per sea regions (Fig. 4 and Fig. 5)

The largest decrease of BOD from 1992 to 2011 has occurred in the rivers draining to the  Mediterranean Sea (63 %), resulting in the lowest concentrations in Europe  The lowest concentrations (about 1.6 mg O2/l) were found in the Mediterranean sea and Celtic Seas, Bay of Biscay and Iberian Coast sea region (Fig. 4). Due to ongoing decrease, the concentrations in these rivers have become lower than the concentrations in the Baltic Sea region, which remain fairly stable (about 1.8 mg O2/l). The second highest decrease of BOD has occurred in the rivers draining to the Black Sea (60 %). Even though still the highest among all sea regions, their concentrations (about 2.3 mg O2/l) have approached the average European concentrations . Similarly high, but also decreasing are the rivers of Greater North Sea (about 2.2 mg O2/l).. The decrease of BOD is 40 % for the rivers draining to the Greater North Sea and 58 % for the rivers draining to the Celtic Seas, the Bay of Biscay and the Iberian Coast.

The trend analysis also shows that the largest proportion of monitoring stations with significant or marginally significant negative trend in BOD is found for the rivers draining to the Mediterranean and the Black sea, while the lowest proportion is found for the rivers draining to the Celtic Seas, the Bay of Biscay and the Iberian Coast, and the Baltic Sea. The sums of significant and marginally significant trends are as follows:

  • Mediterranean Sea: 75.4 % negative, 2.9 % positive, 2.66 mg O2/l average decrease;
  • Black Sea: 78.2 % negative, 0 % positive, 2.46 mg O2/l average ;
  • Greater North Sea: 66.9 % negative, 3.7 % positive, 1.5 mg O2/l average decrease;
  • Celtic Seas, Bay of Biscay, Iberian Coast: 63.6 % negative, 0.8 % positive, 1.62 mg O2/l average decrease;
  • Baltic Sea: 43.2 % negative, 12.2 % positive, 0.48 mg O2/l average decrease.


Concentrations in rivers draining to different sea are the largest in the Greater North Sea (158 µg N/l) and the Black Sea regions (158 µg N/l). Somewhat smaller are concentrations in Mediterranean Sea (122 µg N/l) and Celtic Seas, Bay of Biscay and Iberian Coast regions (109 µg N/l). The Baltic Sea region has a lower record of 59 µg N/l. The lowest decrease has occurred in the rivers draining to the Arctic Ocean (45 %) with very low concentrations (about 5 µg N/l).

The decrease of total ammonium from 1992 to 2011 has been similar (70-80 %) in all sea regions except for Arctic Ocean (45 %). The largest proportion of monitoring stations with significant or marginally significant negative trend in total ammonium is found for the rivers draining to the Black Sea, Celtic Seas, Bay of Biscay and Iberian Coast, Greater North Sea, while the lowest proportion is found for the rivers draining to the Arctic Ocean (Black Sea: 80.6 % negative, 1 % positive; Celtic Seas, Bay of Biscay, Iberian Coast: 74.8 % negative, 0.8 % positive; Greater North Sea: 68.8 % negative, 2.8 % positive; Mediterranean Sea: 57.7 % negative, 4.2 % positive; Baltic Sea: 45.6 % negative, 5.3 % positive; Arctic Ocean: 38.5 % negative, 7.7 % positive; sum of significant and marginally significant trends).

BOD and total ammonium present concentrations by countries
See WISE interactive maps for information displayed for countries, for river basin districts (BOD) and for individual stations: Mean annual BOD in rivers and Mean annual Total Ammonium in rivers

Countries with more than 50 % of all river stations within the category of the lowest BOD concentrations (class 1: < 1.4 mg O2/l) for 2011 or the latest reported year are Slovenia, Spain, Cyprus, Ireland, France, the United Kingdom and Finland.  Countries with more than 20 % of the stations within the category of the highest BOD concentrations (class 5: >= 4 mg O2/l) are Turkey, Montenegro, Albania, the Former Yugoslav Republic of Macedonia, Greece, Kosovo under UNSCR 1244/99, Hungary and Romania.

Countries with more than 50 % of all river stations within the category of the lowest total ammonium concentrations (class 1: < 0.04 mg N/l) for 2011 or the latest reported year are Iceland, Norway, Finland, Ireland, Austria, Slovenia, Sweden, Latvia, Spain, France, the United Kingdom, Lichtenstein and Croatia. Countries with more than 20 % of the stations within the category of the highest total ammonium concentrations (class 5: >= 0.4 mg N/l) are Kosovo under UNSCR 1244/99, the Netherlands, Montenegro, Belgium, Albania, Luxembourg, Greece, Romania, the Former Yugoslav Republic of Macedonia and Bulgaria.

Data sources

More information about this indicator

See this indicator specification for more details.

Contacts and ownership

EEA Contact Info

Peter Kristensen

Ownership

EEA Management Plan

2013 1.4.2 (note: EEA internal system)

Dates

Frequency of updates

Updates are scheduled once per year in July-September (Q3)
European Environment Agency (EEA)
Kongens Nytorv 6
1050 Copenhagen K
Denmark
Phone: +45 3336 7100