Rijkswaterstaat Environment

Implementation EC Urban Wastewater Treatment Directive

The Council Directive 91/271/EEC concerning urban wastewater treatment was adopted on 21 May 1991. Its objective is to protect the environment from the adverse effects of discharges and discharges from certain industrial sectors (see Annex III of the Directive) and concerns the collection, treatment and discharge of:
  • Domestic wastewater
  • Mixture of wastewater
  • Wastewater from certain industrial sectors (see Annex III of the Directive)

Specifically the Directive requires:

  • The Collection and treatment of wastewater in all agglomerations of >2000 population equivalents (p.e.).
  • Where the establishment of a collecting system is not justified either because it would produce no environmental benefit or because it would involve excessive costs, individual systems or other appropriate systems which achieve the same level of environmental protection will be used.
  • Secondary treatment of all discharges from agglomerations of > 2,000 p.e., and more advanced treatment for agglomerations >10,000 population equivalents in designated sensitive areas and their catchments.
  • A requirement for pre-authorisation of all discharges of urban wastewater, of discharges from the food-processing industry and of industrial discharges into urban wastewater collection systems.
  • Monitoring of the performance of treatment plants and receiving waters.
  • Controls of sewage sludge disposal and reuse, and treated wastewater reuse whenever appropriate.

Situation in the Netherlands
Municipalities maintain and control the public sewerage systems. The management of public UWWPs and the quality of surface water are the responsibility of the Water Boards. The Netherlands has an extensive sewerage system connected to urban wastewater treatment plants (UWWP). Most of the sewer wastewater comes from Dutch households. A small volume comes from industries and rainwater drainage. Not all the wastewater is collected in a sewer system. Outlying households discharge on surface water or on soil. Before discharge, this wastewater is always treated in an individual wastewater treatment system (a septic tank or a small biological wastewater treatment facility). The Netherlands hereby complies with the Council Directive for all p.e.

Problems with overflows
Not all the wastewater collected in a sewerage system reaches an UWWP. With heavy rainfall, sewerage systems run over, causing overflows in the surface water. In some cases this happens frequently. Last year's policy was designed to reduce these wastewater overflows. The fact that there are too many overflows in Dutch sewerage systems is caused by the widespread system and the fact that all kinds of wastewater are discharged in this system. To reduce overflows, legislation has been created to ensure that clean groundwater and rainwater is not collected in a sewerage system. This legislation includes a preference to allow this clean water to flow back in/on soil or into surface water. Furthermore the legislation includes an assurance that only industrial wastewater which contains biological compounds (and which is similar to domestic wastewater) may be treated in a public UWWP. Other industrial wastewater must be treated in industrial wastewater treatment plants (owned by the companies). These preferences of wastewater are implemented in the Environmental Protection Act (EPA) which contains the following steps:

  1. Prevention production
  2. Prevention pollution
  3. Separated collection
  4. Domestic wastewater, other water similar to domestic wastewater collected in a public sewer system and UWWP
  5. Other wastewater: owner responsible, preferably returned to the environment