Organic pollution has been on the rise in the Danube over the last century, as human activities have resulted in increasing loads of wastewater rich in organic matter. The most serious organic pollution problems occur in tributaries that regularly receive untreated or inadequately treated wastewater from industrial plants and municipalities. Thanks to the significant improvement of wastewater infrastructure and services in the Danube countries, the basin-wide organic emissions reduced by 60% since the mid 2000s.
Organic pollution refers to emissions of non-toxic organic substances that can be biologically decomposed by bacteria to a high extent.
The primary impact of organic pollution is the negative influence on the dissolved oxygen balance of the water bodies. Significant oxygen depletion can be experienced downstream of pollution sources mainly due to biochemical decomposition of organic matter. Microorganisms use the oxygen available in the water bodies to break organic compounds down to simple molecules. However, dissolved oxygen concentrations increase again once the oxygen enrichment rate via diffusion from the atmosphere and photosynthesis ensured by algae and macrophytes exceeds the rate of consumption. Organic pollution can be associated with the health hazard due to possible microbiological contamination. Due to the self-purification capacity of water bodies the water quality impacts of individual point sources are mostly local.
Urban wastewater emission inventories
The ICPDR develops and maintains comprehensive inventories on urban wastewater emissions. Information on all agglomerations above 2,000 population equivalents is collected including the size of the urban settlements, the connection rate of population to wastewater collecting systems and treatment plants, the treatment stage of the plants, the wastewater discharge rate and basic pollution figures. The last inventory was compiled in 2021 for the reference year 2018. These inventories serve the pollution assessments of the Danube River Basin Management Plans elaborated by the ICPDR every six years.
Policy recommendations on wastewater management
The ICPDR published the Recommendation paper on Wastewater Management, that communicates the overall challenges, specific needs and potential solutions related to wastewater management in the DRB. Moreover, it aims at highlighting certain aspects of the current legislation from technical perspective that have been emerging in the Danube countries. It also provides several recommendations and potential actions for national policy making to improve wastewater management.
ICPDR-World Bank-Danube Water Program initiative on capacity building in wastewater management
The ICPDR in close cooperation with the World Bank and the Danube Water Program and with support of the Priority Area 4 (Water Quality) of EU Strategy for the Danube Region (EUSDR), launched an initiative to guide and support Danube countries in achieving sustainable wastewater management by developing and implementing capacity building programs and information exchange in wastewater management and by facilitating proper dialogue among the international financing institutes, national and local administration bodies and utilities. The initiative aims to provide interested and committed government and utility representatives from the Danube region with the appropriate knowledge, exposure and expertise to support modernization efforts in wastewater management sector and development of optimal sector policies.