The term “sensitive areas” comes from Directive 91/271/EEC and is used to picture water recipients which are or can become eutrophic – a condition of nutrients enrichment (nitrogen and phosphorus). This condition is linked to fast growth of algeas which changes the balance and deteriorates the water quality.
The term is transposed in Ordinance 6 and according to the Ordinance the Minister of environment and water isses an Order for designation of the sensitive areas.
With an order of the Minister of environment (available only in Bulgarian) from year 2003, the Danube and Black Sea catchment areas and parts of the rivers Struma, Arda, Maritsa and Tundja are designated as sensitive areas. Normal areas is only the Northeast part of the country characterized with dry river beds and Mesta river. Map with the sensitive areas can be found in the 2011 public report (available only in Bulgarian).
In case a water recipient is declared as a sensitive area all wastewater arising from agglomeration of above 10 000 population equivalent should before discharge be subject to more stringent treatment with nutrients removal according to the emission limit values in the discharge permit. Thus the recipient is protected from further deterioration.