Institute for Hygiene and Applied Immunology - Water Microbiology, Medical University Vienna, Kinderspitalgasse 15, 1090, Vienna, Austria.
Division Water Quality and Health, Karl Landsteiner University of Health Sciences, Dr. Karl Dorrek Straße 30, 3500, Krems, Austria.
Environ Sci Pollut Res Int. 2024 Jul;31(33):45697-45710. doi: 10.1007/s11356-024-34190-0. Epub 2024 Jul 8.
The Danube River is, at 2857 km, the second longest river in Europe and the most international river in the world with 19 countries in its catchment. Along the entire river, faecal pollution levels are mainly influenced by point-source emissions from treated and untreated sewage of municipal origin under base-flow conditions. In the past 2 decades, large investments in wastewater collection and treatment infrastructure were made in the European Union (EU) Member States located in the Danube River Basin (DRB). Overall, the share of population equivalents with appropriately biologically treated wastewater (without disinfection) has increased from 69% to more than 85%. The proportion of tertiary treatment has risen from 46 to 73%. In contrast, no comparable improvements of wastewater infrastructure took place in non-EU Member States in the middle and lower DRB, where a substantial amount of untreated wastewater is still directly discharged into the Danube River. Faecal pollution levels along the whole Danube River and the confluence sites of the most important tributaries were monitored during four Danube River expeditions, the Joint Danube Surveys (JDS). During all four surveys, the longitudinal patterns of faecal pollution were highly consistent, with generally lower levels in the upper section and elevated levels and major hotspots in the middle and lower sections of the Danube River. From 2001 to 2019, a significant decrease in faecal pollution levels could be observed in all three sections with average reduction rates between 72 and 86%. Despite this general improvement in microbiological water quality, no such decreases were observed for the highly polluted stretch in Central Serbia. Further improvements in microbiological water quality can be expected for the next decades on the basis of further investments in wastewater infrastructure in the EU Member States, in the middle and lower DRB. In the upper DRB, and due to the high compliance level as regards collection and treatment, improvements can further be achieved by upgrading sewage treatment plants with quaternary treatment steps as well as by preventing combined sewer overflows. The accession of the Western Balkan countries to the EU would also significantly boost investments in wastewater infrastructure and water quality improvements in the middle section of the Danube. Continuing whole-river expeditions such as the Joint Danube Surveys is highly recommended to monitor the developments in water quality in the future.
多瑙河是欧洲第二长的河流，全长 2857 公里，也是世界上最具国际性的河流，流域内有 19 个国家。在整个河流中，基础流量条件下，粪便污染水平主要受来自城市处理和未处理污水的点源排放影响。在过去的 20 年里，欧盟成员国在多瑙河流域（DRB）投入了大量资金用于废水收集和处理基础设施建设。总体而言，人口当量中适当经过生物处理（不进行消毒）的污水比例从 69%增加到 85%以上。三级处理的比例从 46%上升到 73%。相比之下，多瑙河中下游的非欧盟成员国没有进行类似的废水基础设施改善，大量未经处理的废水仍直接排入多瑙河。在四次多瑙河考察期间，即联合多瑙河调查（JDS），对整条多瑙河及其最重要的支流的汇合点的粪便污染水平进行了监测。在所有四次调查中，粪便污染的纵向模式高度一致，通常在多瑙河的上游段污染水平较低，而在中游和下游段污染水平较高，且存在主要的热点地区。从 2001 年到 2019 年，在所有三个河段都可以观察到粪便污染水平的显著下降，平均降幅在 72%到 86%之间。尽管在微生物水质方面有了整体改善，但在塞尔维亚中部高度污染的河段并未观察到这种下降。在欧盟成员国进一步投资废水基础设施建设、在多瑙河中下游地区投资废水基础设施建设的基础上，预计未来几十年微生物水质将进一步改善。在上游 DRB，由于收集和处理的合规水平较高，通过升级具有四级处理步骤的污水处理厂以及防止合流污水溢流，可以进一步提高污水处理水平。西巴尔干国家加入欧盟也将大大推动多瑙河中游地区的废水基础设施投资和水质改善。强烈建议继续进行全河考察，如联合多瑙河调查，以监测未来水质的发展。
