A - Urban wastewater treatment and nitrates from agricultural source
Eutrophication is defined as “the enrichment of water by nutrients, especially compounds of nitrogen and/or phosphorus, causing an accelerated growth of algae and higher forms of plant life to produce an undesirable disturbance to the balance of organisms present in the water and to the quality of the water concerned” 
. Algal blooms on beaches and shoreline and cyanobacterial blooms in lakes and rivers pose a significant, even deleterious health (drinking water, bathing water) and ecological hazard.
The EEA underlines that phosphorus and nitrates are the two key nutrient and substance for eutrophication .
The reduction of nutrient discharges requires controlling human activities, such as wastewater, or nitrate pollution from agricultural activities. In 1991, two EU specific water directives were adopted in this respect, and to contribute to improving the quality of water bodies: Council Directive 91/271/EEC concerning urban-waste water treatment (1) and Council Directive 91/676/EEC concerning the protection of water against pollution caused by nitrates from agricultural sources (2). Both are highly technical and require both legal and extra-legal expertise to interpret and to implement them. They also require substantial financial investment, especially for the collection and treatment of urban wastewater. Several Member States regularly report financial and technical difficulties in complying with the Urban Wastewater Directive.
Finally, the two directives introduce a modulation of the resulting obligations according to the vulnerability and/or sensitivity of the aquatic environment to eutrophication. Member States have to identify sensitive /vulnerable areas according to certain criteria, and apply more strict obligations. These directives are at the origin of numerous cases brought before the CJEU, including financial penalties against Member States (failure to comply with judgment of the CJEU ).