Water Quality - Sewage Treatment in the UK: Sensitive Areas
Sensitive Areas identified in the UK
Water bodies can be identified as Sensitive Areas on three grounds:
- (a) Where they are found to be eutrophic [1] or where they may become eutrophic in the near future if protective action is not taken.
- (b) Where they exceed or could exceed a specified concentration of nitrate - to protect water supply sources and/or the environment.
- (c) Where discharges affecting them are subject to more than secondary treatment to comply with the standards of other Directives.
Where required, more stringent treatment than secondary (tertiary) treatment is applied to sewage to protect Sensitive Areas. Tertiary treatment can be a variety of different types of treatment, as explained below. Sewage treatment service providers and the environmental regulators work together to assess what improvements and funding is needed.
Sensitive Areas identified under criteria (a) and/or (b)
Where Sensitive Areas are identified under criteria (a) and/or (b) additional treatment is required where they are affected by discharges from sewage works serving communities with populations greater than 10,000. The additional treatment involves reducing levels of nitrogen and/or phosphorus in discharges to standards set in the Urban Waste Water Treatment Directive within seven years of identification of these Sensitive Areas.
Waters are reviewed every four years to confirm the status of existing Sensitive Areas and to determine if further water bodies conforming to the criteria should be identified as Sensitive Areas (Eutrophic or Nitrate). Reviews are conducted by the environmental regulators: for England and Wales the Environment Agency; for Scotland the Scottish Environment Protection Agency; and for Northern Ireland the Environment and Heritage Service of the Department of the Environment. From the finding of these reviews recommendations are made to Ministers who make or authorise identifications of Sensitive Areas.
Sensitive Areas identified under criterion (c)
Where Sensitive Areas are identified under criterion (c) the water bodies will have been previously designated for the purposes of other Directives and a requirement for more than secondary treatment already established through a need to meet the standards of the other Directives. The time by which required tertiary treatment needs to be in place will vary according to the provisions set in the individual Directives. Also, the type of tertiary treatment will depend on the particular pollutants the other Directives are guarding against. For example, where necessary, disinfection will be applied to discharges affecting waters identified under the Bathing Waters or Shellfish Waters Directives, where secondary treatment alone would result in consistent failures of these waters.
Maps of identified Sensitive Area (Bathing Waters) and (Shellfish Waters), individually delineated, can be seen via the tables listing Sensitive Areas (Bathing Water) and (Shellfish Water) accessible through the Full listings tables of Sensitive Areas link to the left.
Sensitive Areas identified under criteria (a), (b) and (c)
The following summary table shows numbers of the different types of Sensitive identified in the UK.
Summary of Sensitive Areas identified in the UK
UK Sensitive Area types and dates designated |
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Type |
(criterion) | England |
Northern Ireland |
Scotland |
Wales |
Total |
|
| Eutrophic | (a) | 32 on 18.5.1994 45 on 30.7.1998 31 on 27.6.2002 24 on 15.10.2007 |
2 on 16.12.1994 3 on 20.12.2001 9 on 28.7.2006 |
3 on 18.5.1994 1 on 28.8.2000 1 on 18.6.2003 78 on 31.3.2006 |
1 on 18.5.1994 2 on 30.7.1998 2 on 1.10.2002 |
234 | |
| Nitrate | (b) | 3 on 25.2.1997 4 on 5.3.2002 1 on 27.6.2002 |
- | - | - | 8 | |
| Bathing Water | (c) | 180 on 5.3.2002 | 1 on 28.7.2006 | 9 on 26.2.2002 | 24 on 5.4.2002 | 214 | |
| Shellfish Water | (c) | 47 on 21.5.2003 | 1 on 28.7.2006 | 1 on 18.6.2003 | 12 on 2.7.2003 | 61 | |
| Freshwater Fish | (c) | - | - | 8 on 18.6.2003 | - | 8 | |
| Total | 367 | 16 | 101 | 41 | 525 | ||
|
Note: where appropriate pre-existing sensitive areas may be extended in subsequent review/identification rounds. The Sensitive Areas extended in subsequent identification rounds are not included in the numbers given of new Sensitive Area identifications in subsequent rounds. |
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Less Sensitive Areas
In waters where it is considered there will be no adverse environmental effects from a lower standard of treatment than secondary treatment of sewage discharges, treatment to a minimum of primary treatment is permitted providing certain conditions in the Directive are met.
Across the UK 85 Less Sensitive Areas were identified in 1994. Estuarine and coastal waters formerly identified as Less Sensitive Areas (High Natural Dispersion Areas under the transposing regulations) in 1994 are not shown on the maps as they have now all been revoked.
Less Sensitive Areas - identification and revocation dates |
||
UK Area |
Numbers and dates identified |
Dates revoked |
| England | 49 on 18.5.1994 | 13 on 30.7.1998 36 on 23.9.1998 |
| Northern Ireland | 3 on 16.12.1994 | 1 in May 1998 2 on 18.1.2002 |
| Scotland | 24 on 18.5.1994 | 12 in October 1998 9 on 28.8.2000 3 on 24.7.2002 |
| Wales | 9 on 18.5.1994 | 3 on 30.7.1998 6 on 23.9.1998 |
[1]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.
Page last modified: 28 September 2007
Page published 21 October 2002