C10 - BOD and concentration of ammonium in rivers of Georgia
Is organic matter and ammonium pollution in rivers of Georgia decreasing?
Figure 1 - Rivers – Annual mean biological oxygen demand (BOD) and ammonium concentration (2004-2018)
Data sources:
Data was provided by National Environmental Agency of the Ministry of Environmental Protection and Agriculture under the ENI SEIS II East project activities
Note: The data series are calculated as the average of annual mean of BOD5 (mg O2/l) (top), and ammonium concentration (mg NH4-N/l) (bottom) for river sites in the two major river basins of Georgia (Black Sea and Caspian Sea basins) and for the whole country for the period 2004-2018. The total number of river sites is given in parenthesis.
Biochemical oxygen demand (BOD) and ammonium are key indicators of organic pollution in water. BOD shows how much dissolved oxygen is needed for the 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, high concentration of ammonia and disappearance of fish and aquatic invertebrates. Some of the year-to-year variation can be explained by variation in precipitation and runoff.
Average BOD has decreased somewhat over the time period 2004-2018. Comparing the average of the last three years to that of the first three years, average BOD has decreased by 11% for the country as a whole. The main decrease is seen for the Black Sea basin (21%). The average for the Caspian Sea basin increased towards 2006 but has decreased since then.
Average ammonium concentration showed a more pronounced decrease (50% for the whole country). The largest decrease was observed for rivers draining to the Caspian Sea (62%).
The middle of the time series should be treated with some caution, due to lower number of samples per year. This goes in particular for the years 2011-13 and the Caspian Sea basin. This may explain some of the variability observed for ammonium concentration in this period.
The decrease in BOD and ammonium concentrations can be attributed to measures taken, e.g. improvement of the urban and industrial wastewater treatment. Further improvement is expected in particular for the Black Sea river basin where the large cities have not had waste-water treatment plants. Treatment plants are currently under construction in Zugdidi and Poti and construction of a treatment plant in Kutaisi is planned.
What is the current state of organic matter and ammonium pollution of rivers in Georgia?
Figure 2 - Rivers- BOD and Ammonium (2016-2018)
Data sources:
Data was provided by National Environmental Agency of the Ministry of Environmental Protection and Agriculture under the ENI SEIS II East project activities
Note: Distribution of river monitoring sites to BOD5 (left) and ammonium concentration (right) classes in the two major river basins of Georgia (Black Sea and Caspian Sea basins), based on average of the annual mean concentrations for 2016-2018. The total number of monitoring sites per river basin is given in parenthesis.
The class system is the same as the one used in the EEA indicator WAT 002- Oxygen consuming substances European rivers. See the indicator specification section there for further information.
All river sites have average BOD below the maximum permissible concentration of 6 mg O2/l. Moreover, only two sites in the Caspian Sea basin have BOD above the stricter criteria set in the EU Directive 78/659/EEC for salmonid fish (3 mg O2/l).
For ammonium the highest concentrations are observed for rivers in the Black Sea basin, probably reflecting the so far poor level of waste-water treatment in this region. 79% of the sites in this region had average concentration above the maximum permissible concentration (0.39 mg NH4-N/l) in 2016-2018. Moreover, this level is quite high in comparison with e.g. the recommended levels in the EU Directive 78/659/EEC (cyprinid fish: 0.16 mg NH4-N/l; salmonid fish: 0.03 NH4-N/l). Only three river sites in Georgia had average concentration below the threshold for cyprinid fish in 2016-2018, and none were below the threshold for salmonid fish.
Indicator specification
Indicator definition
The level of oxygen concentration in water bodies, expressed as biochemical oxygen demand (BOD)—which is the amount of dissolved oxygen required for the aerobic decomposition of organic matter present in water—and the level of concentrations of ammonium (NH4/N-NH4) in rivers.
Units
The annual average BOD after five days of incubation (BOD5) at 20 degrees Celsius is expressed in mg of O2/litre; the ammonium concentration is expressed in mg of N/litre.
Rationale
Justification for indicator selection
Large quantities of organic matter (microbes and decaying organic waste) can result in reduced chemical and biological quality of river water, impaired biodiversity of aquatic communities, and microbiological contamination that can affect the quality of drinking and bathing water. Sources of organic matter are discharges from wastewater treatment plants, industrial effluents and agricultural runoff. Organic pollution leads to higher rates of metabolic processes that demand oxygen.
Scientific references
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Council Directive 91/271/EEC of 21 May 1991 concerning urban wastewater treatment
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Directive 2000/60/EC of the European Parliament and the Council of 23 October 2000 establishing a framework for Community action in the field of water policy (Water Framework Directive) http://ec.europa.eu/environment/water/waterframework/index_en.html;
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National Environment Agency, 2016. Annual report on surface water quality of Georgia, Ministry of Environmental Protection and Agriculture, Tbilisi.
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National Environment Agency, 2017. Annual report on surface water quality of Georgia, Ministry of Environmental Protection and Agriculture, Tbilisi.
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National Environment Agency, 2018. Annual report on surface water quality of Georgia, Ministry of Environmental Protection and Agriculture, Tbilisi.
Policy context and targets
Context description
National policy context
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Law of Georgia on Water, 16 October 1997. №936; http://mepa.gov.ge/Ge/Laws;
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Resolution # 425 of the Government of Georgia of 31 December 2013 on approval of technical regulations for protection against surface pollution of Georgia;
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The third National Program of Environmental Action of Georgia (NEAP-3)
International policy context
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There are several EU directives that aim to improve water quality and reduce impacts, the major one being the Water Framework Directive, which requires the achievement of good ecological status or good ecological potential of surface water bodies. In accordance with the EU-Georgia Association Agreement, the country has an obligation to comply with the requirements of these Directives.
Targets
National targets
The general target is to achieve good ecological status or potential of surface water bodies.
The national maximum permissible concentrations are:
BOD: 6 mg O2/l
Ammonium: 0.39 mg NH4-N/l
<3>International targets
The UN Sustainable Development Goal 6 target 6.3 aims to achieve, by 2030, improve water quality by reducing pollution, eliminating dumping and minimizing release of hazardous chemicals and materials, halving the proportion of untreated wastewater and substantially increasing recycling and safe reuse globally.
Related policy documents
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Resolution # 425 of the Government of Georgia of 31 December 2013 on approval of technical regulations for protection against surface pollution of Georgia;
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The third National Program of Environmental Action of Georgia (NEAP-3)
Methodology
Methodology for indicator calculation
The National Environmental Agency undertakes monitoring of freshwater quality in Georgia. Monitoring data from monitoring conducted at 48 locations of 17 rivers was used. Mostly the sampling frequency is once per month. The number of monitoring sites has increased over the years.
Annual time series for each site are calculated by averaging the values for individual samples per year. Aggregated time series are calculated as the average of the individual annual time series and are calculated for the two major river basins (rivers draining to the Black Sea or the Caspian Sea), as well as for the whole country. Only time series that are complete after gap filling are included in the aggregated time series. This is to ensure that the aggregated data series are consistent, i.e. including the same sites throughout the time series. In this way assessments are based on actual changes in concentration, and not changes in the number of sites.
For the present state analysis, the monitoring sites were assigned to different concentration classes, based on the average of annual mean concentrations for 2016-2018. All sites with data from 2016-2018 were included in the analysis, independent of the number of years with data within the time period.
Methodology for gap filling
Gaps of up to three years are filled by linear interpolation. At the beginning and end of the time series values are extrapolated by copying the first or last value, respectively, for up to three years. Time series with more than three consecutive years missing within the selected time period are not included.
Methodology references
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EEA, 2005. EEA core set of indicators guide. EEA Technical report No 1/2005, ISBN 92-9167-757-4, Luxembourg.
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UNSD and UNEP, 2013. Questionnaire 2013 on Environment Statistics. United Nations Statistics Division and United Nations Environment Programme, Questionnaire 2013 on Environment Statistics, Section Water.
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UNECE, 2018. Guidelines for the Application of Environmental Indicators, Description of C10. Biochemical oxygen demand (BOD) and concentration of ammonium in rivers.
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UNECE, 2018. Guidelines for the Application of Environmental Indicators, Glossary of terms – C10. Biochemical oxygen demand (BOD) and concentration of ammonium in rivers.
Uncertainties
Methodology uncertainty
No uncertainty has been specified.
Data sets uncertainty
No uncertainty has been specified.
Rationale uncertainty
No uncertainty has been specified.
Data sources
Data was provided by National Environmental Agency of the Ministry of Environmental Protection and Agriculture under the ENI SEIS II East project activities