Recital 15

(15)Discharges in high mountain regions, namely regions above an altitude of 1 500 m, and small agglomerations of below 2 000 p.e. in cold climate areas with a quarterly average temperature of below 6 o C in the inlet, in which it is difficult to apply an effective biological treatment because of low temperatures, should be allowed to use treatment less stringent than secondary treatment, provided that detailed studies demonstrate that such discharges do not have adverse effects on the environment or human health. Similarly, discharges into deep marine waters from smaller agglomerations of below 150 000 p.e. located in less-populated outermost regions, with fewer than 275 000 inhabitants characterised by difficult topography, such as steep slopes, and discharging their urban wastewater into deep marine waters in the open ocean, favouring a high level of dilution of those urban wastewater discharges into the receiving waters, should also be able to benefit from that derogation. Nevertheless, in order to ensure the equal treatment of all Member States and a high level of protection of the environment and human health on the whole territory of the Union, that derogation should be limited to 20 years, which is the time required to progressively upgrade the remaining urban wastewater treatment plants to secondary treatment in those areas where secondary treatment might be more difficult to apply. That derogation should be granted provided that detailed studies demonstrate that such discharges do not have adverse effects on the environment or human health and do not impact the compliance of the receiving waters with other relevant Union law, such as Directive 2000/60/EC, 2006/7/EC ⁸ , or 2008/56/EC ⁹ of the European Parliament and of the Council.