Urban Wastewater

The fact sheet "Urban Wastewater" estimates the organic load rejected into water resources by the urban sector, taking into account the type of treatment to which the respective wastewater is subjected, with particular focus on agglomerations and wastewater treatment plants evaluated by the Urban Wastewater Directive, particularly as regards compliance with its requirements.

According to the legislation in force, urban wastewater is household wastewater or the mix of this wastewater with industrial wastewater and/or rainwater.

The treatment of wastewater in Portugal is regulated by Directive 91/271/EEC as subsequently amended by Directive 98/15/EC and by Regulation (EC) no. 1882/2003. These directives were transposed into Portuguese legislation, respectively, by Decree-Law no. 152/97 and by Decree-Law no. 348/98.

The quantification of the pressures exerted on waterbodies by rejections from wastewater treatment systems is an essential step in the process of assessing the state of water bodies, as set out in the Water Framework Directive (transposed by the Water Law, as amended and republished by Decree-Law no. 130/2012).

The rejection of urban waste water from agglomerations with a population equivalent (p.e.). under 2 000 into freshwaters and estuaries, as well as discharges from agglomerations with a p.e. under 10 000 tonnes into coastal waters shall be subject to appropriate treatment. The remainder must be subjected to secondary treatment if they are rejected into normal zones, or more advanced than the secondary treatment if they are rejected into sensitive areas and the p.e. is ≥ 10 000. Preliminary treatment includes the removal of the coarsest solids by screening/sieving and desanding and the primary treatment includes decantation for removal of smaller solids. Secondary treatment entails, in most cases, the removal of organic matter and the decantation of sludges formed in the biological treatment, and the more advanced or tertiary treatment includes stages for disinfection or removal of nutrients if the receiving medium so requires.

Sensitive areas should be designated wherever there are agglomerations ≥ 10 000 pe. rejecting into:

  • Water bodies that are eutrophic or likely to become eutrophic in the near future if protective measures are not taken;
  • Water bodies intended for the abstraction of drinking water with a nitrate content of up to 50 mg / l of nitrates;
  • Areas where treatment other than secondary treatment is required in order to comply with Council directives, in particular, those relating to fishery waters, bathing waters, bivalve mollusc production waters and surface water abstractions intended for the production of water for human consumption.

Conformity regarding agglomerations and wastewater treatment plants (ETAR) is assessed for:

  • the existence of collection systems;
  • the existence of suitable treatment according to the receiving environment and the size of the agglomeration;
  • control over ETAR rejections, particularly as regards the number of collected samples and the emission limit values, for certain parameters.

This fact sheet concerns Portugal and will be updated every two years, following the Urban Wastewater Directive report, the most recent data referring to 2016.

Objectives and targets: 
  • To decrease wastewater rejections into waterbodies, whether surface or groundwater, with particular attention to those whose status is lower than 'Good;'
  • To progressively increase the number of agglomerations in accordance with Directive 91/271/EEC, particularly as regards the appropriate treatment and compliance with the requisites for discharge by ETAR;
  • To eliminate all infringement proceedings under Directive 91/271/EEC by the end of 2019.
Progress analysis:

The total estimated load generated in mainland Portugal is about 15.6 million p.e. (population equivalent).

Last update: 
Wednesday, 17 April, 2019