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Urban waste water treatment

Due to their volume, discharges of urban waste water are the second most serious cause of water pollution in the form of eutrophication. This Directive seeks to harmonise measures relating to the treatment of such waters at Community level.

Council Directive 91/271/EEC of 21 May 1991 concerning urban waste water treatment [See amending acts].

SUMMARY

Directive 91/271/EEC

This Directive concerns the collection, treatment and discharge of urban waste water and the treatment and discharge of waste water from certain industrial sectors. Its aim is to protect the environment from any adverse effects caused by the discharge of such waters.

Industrial waste water entering collecting systems and the disposal of waste water and sludge from urban waste water treatment plants are subject to regulations and/or specific authorisation by the competent authorities.

The Directive establishes a timetable, which Member States must adhere to, for the provision of collection and treatment systems for urban waste water in agglomerations corresponding to the categories laid down in the Directive. The main deadlines are as follows:

  • 31 December 1998: all agglomerations of more than 10 000 “population equivalent”* (p.e.) which discharge their effluent into sensitive areas must have a proper collection and treatment system;
  • 31 December 2000: all agglomerations of more than 15 000 p.e. which do not discharge their effluent into a sensitive area must have a collection and treatment system which enables them to satisfy the requirements in Table 1 of Annex I;
  • 31 December 2005: all agglomerations of between 2 000 and 10 000 p.e. which discharge their effluent into sensitive areas, and all agglomerations of between 2 000 and 15 000 p.e. which do not discharge into such areas must have a collection and treatment system.

Annex II requires Member States to draw up lists of sensitive and less sensitive areas which receive the treated waters. These lists must be updated regularly.

The treatment of urban water is to be varied according to the sensitivity of the receiving waters.

The Directive lays down specific requirements for discharges from certain industrial sectors of biodegradable industrial waste water not entering urban waste water treatment plants before discharge to receiving waters.

Member States are responsible for monitoring both discharges from treatment plants and the receiving waters. They must ensure that the competent national authorities publish a situation report every two years. This report must also be sent to the Commission.

Member States must set up national programmes for the implementation of this Directive and must present them to the Commission.

The Directive also provides for temporary derogations.

Directive 98/15/EC

This Directive clarifies the rules relating to discharges from urban waste water treatment plants in order to put an end to differences in interpretation by the Member States.

It specifies, among other things, that:

  • the option of using daily averages for the total nitrogen concentration applies both to agglomerations of 10 000-100 000 p.e. and to those of more than 100 000 p.e.;
  • the condition concerning the temperature of the effluent in the biological reactor and the limitation on the time of operation to take account of regional climatic conditions only apply to the “alternative” method using daily averages;
  • use of the “alternative” method must ensure the same level of environmental protection as the annual mean technique.

Key terms used in the act

  • urban waste water means waste water from residential settlements and services which originates predominantly from the human metabolism and from household activities (domestic waste water) or a mixture of domestic waste water with waste water which is discharged from premises used for carrying on any trade or industry (industrial waste water) and/or run-off rain water;
  • eutrophication means 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;
  • population equivalent is a measure of pollution representing the average organic biodegradable load per person per day: it is defined in Directive 91/271/EEC as the organic biodegradable load having a five-day biochemical oxygen demand (BOD5) of 60 g of oxygen per day.

REFERENCES

Act

Entry into force

Deadline for transposition in the Member States

Official Journal

Directive 91/271/EEC

19.06.1991

30.06.1993

OJ L 135 of 30.05.1991


Amending act(s)

Entry into force

Deadline for transposition in the Member States

Official Journal

Directive 98/15/EC

27.03.1998

30.09.1998

OJ L 67 of 07.03.1998

RELATED ACTS

Communication from the Commission of 22 March 2007 entitled: “Towards sustainable water management in the European Union – First stage in the implementation of the Water Framework Directive 2000/60/EC” [COM(2007) 128 final – Not published in the Official Journal].
In this report the Commission notes that in 2003 significant amounts of waste water were still not being treated adequately before being discharged into the surface waters of the Member States. The main problems singled out are the lack of appropriate treatment and the lack of designation of “sensitive areas”. In 2003, 17 cities with populations of over 150 000 did not have treatment systems. Significant financial investment is still needed in order for Member States to comply fully with the Directive.

Report from the Commission of 23 April 2004 on the implementation of Council Directive 91/271/EEC of 21 May 1991 concerning urban waste water treatment, as amended by Commission Directive 98/15/EC of 27 February 1998 [COM(2004) 248 final – Not published in the Official Journal].
This report looks at the application of the Directive at 31 December 2000. The Commission notes that, since the previous report, considerable efforts have been undertaken by Member States and improvements in the waste water treatment sector have been achieved in many countries. Significant improvements have been achieved in terms of the identification of sensitive areas and waste water infrastructure in those areas, but the Commission considers that less than 50% of the waste water load impacting on sensitive areas is receiving the appropriate level of treatment. Meanwhile, the number of cities with populations of over 150 000 without proper waste water treatment has fallen from 37 in 1998 to 25. Despite improvements having taken place, however, the Commission is concerned about the considerable delays in implementing the Directive and stresses that implementation will be a particular challenge for the new Member States.

Report from the Commission of 21 November 2001 on the implementation of Council Directive 91/271/EEC of 21 May 1991 concerning urban waste water treatment, as amended by Commission Directive 98/15/EC of 27 February 1998 [COM(2001) 685 final – Not published in the Official Journal].
This report looks at the application of the Directive at 31 December 1998. On that date, a total of 37 European cities with a population of more than 150 000 were discharging their waste water untreated into the natural environment. Another 57 were also discharging a large proportion of their effluent either untreated or without proper treatment.

Report from the Commission of 15 January 1999 on the implementation of Council Directive 91/271/EEC of 21 May 1991 concerning urban waste water treatment, as amended by Commission Directive 98/15/EC of 27 February 1998 [COM(98) 775 final – Not published in the Official Journal].

Last updated: 07.09.2007
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