EU SPECIFIC WATER LEGISLATIONS

Designation of sensitive areas & more stringent treatment (article 5)

Another major provision is that of Article 5 which lays down a specific additional requirement that applies to “sensitive areas.” Member States shall ensure that urban wastewater entering collecting systems shall before discharge into such sensitive areas be subject to “more stringent treatment”, sometimes called “tertiary treatment” for all discharges from agglomerations of more than 10 000 p.e. (Art. 5(2)). By and large, sensitive areas are freshwater bodies, estuaries and coastal waters “which are found to be eutrophic or which in the near future may become eutrophic if protective action is not taken”, surface freshwater intended for the abstraction of drinking water “which could contain an excessive concentration of nitrate (…) if action is not taken”, and, as per some sort of a “catch-all clause”, all other “areas where further treatment than that prescribed in Article 4 of this Directive is necessary to fulfill Council Directives” (Annex II).

Waters must only be designated as sensitive areas if discharges contribute to the aquatic environment’s eutrophic nature or to the risk that the waters may become eutrophic. In a given instance, the existence of a causal link between nutrient input and the accelerated growth of phytoplankton was considered to be sufficiently probable to require the adoption of measures based on the precautionary principle, even though the ecological model on which it was based was not perfect . For example, sensitive areas were found to exist for the purpose of the requirement of more stringent treatment with respect to the whole of Finnish territory as well as with respect to the whole of Swedish territory .
Italy was found to be in breach because it did not subject urban wastewaters in the Milan area to more stringent treatment than the regular secondary treatment although they were discharged into the sensitive areas of the Pô Delta and the coastal areas of the North West Adriatic: it makes no difference whether the waste-water discharges directly into a sensitive area rather than indirectly, e.g. by going through the water basin of the Po . More recently, Italy was again found to be in breach because it failed to ensure that “the minimum percentage of reduction in the overall load entering all urban waste water treatment plants is at least 75% for the total quantity of phosphorus and at least 75% for the total quantity of nitrogen” in the sensitive areas of basin of the Po and Adriatic Delta, Lake Varese, Lake Como and in the basin of the Gulf of Castellammare (Sicily)”.
However, direct or indirect discharges from urban wastewater treatment plants situated in the same catchment area of a sensitive area, are required to meet the requirements applicable to sensitive areas only to the extent that those discharges contribute to the pollution of that area and a causal link is established between those discharges and the pollution of the sensitive areas.
In addition to the obligation imposed on Member States by Article 4 for adequate treatment and that under Article 5 for more stringent treatment in anticipation of a discharge in vulnerable areas, such discharges must comply with the requirements of Annex I-B. For instance, discharges from urban wastewater treatment plants shall meet quantified requirements as to biochemical oxygen demand, chemical oxygen demand, and total suspended solids (Annex I, Table 1).

The Court of Justice ruled that the obligation imposed on Member States by Article 4 that concerned agglomerations submit wastewater to adequate treatment , as well as their obligation under Article 5 that those waters be subjected to more stringent treatment than that described in Article 4 prior to being discharged into vulnerable areas and, in both situations, that such discharges comply with the requirements of Annex I-B, does not imply that samples be taken over a full year.

In 2021, the Court confirmed that “where a Member State is able to present a sample which satisfies the requirement of Annex I.B, the obligations deriving from article 4 of that directive must be regarded as having been complied with since that article does not require sampling to be carried out (…) for a whole year”. It also considered that “there is nothing to suggest that the situation is any different as regards compliance with the obligations arising from article 5 of directive 91/271” . The Court concluded that “a distinction must be draw between the Member States’ obligations as to the result to be achieved under articles 4 and 5 in order to verify that discharges from urban waste water treatment plants comply with the requirements of Annex I.B (…) and the continuous obligation to which they are subject under article 15 of that directive in order to ensure that, over time, those discharges meet the quality requirements which apply from time when the treatment is brought into operation” .
In addition, the natural retention of nitrogen is likely to be considered as a method for removing nitrogen from urban wastewater. In the context of infringement proceedings against Sweden and Finland, the Court has ruled that “no provision of Directive 91/271 precludes” this possibility.