Water Quality - Urban Waste Water Treatment Directive
Sewage Treatment in the UK: Implementation of the
EC Urban Waste Water Treatment Directive
Improvements on the collection of waste water
The sewage treatment service providers in the UK are responsible for maintaining and improving the public sewers which serve most of the UK population. About 96% of the UK population is connected to sewers leading to sewage treatment works. Most of the remainder are served by small private treatment works, cesspits or septic tanks.
All sewerage systems that also collect rainwater (combined sewers) need overflow outlets (combined sewer overflows) to deal with the extra water collected during some rainstorms. Without these safety valves both domestic, other properties, and sewage treatment works would be at risk of flooding. The Directive recognises that although sewage in these overflow discharges is diluted with significant amounts of rainwater, it can affect the environment. The legislation therefore requires that pollution from these overflows is limited. In the UK we have the necessary regulatory controls and design criteria to limit pollution from combined sewer overflows. For example, in England and Wales for the five years to 2000, 1,200 unsatisfactory combined sewer overflows were improved. Furthermore, between 2000 and 2005 another 4,700 overflows will be brought up to standard in England and Wales.
Improvements in the treatment of waste water
The Directive specifies sewage treatment deadlines that are linked to the size of the communities (agglomerations) served by a sewerage network and the nature of the water receiving the treated effluent. It sets secondary treatment as the normal standard, but requires tertiary treatment where qualifying discharges affect SENSITIVE AREAS identified under the Directive.
At 31 December 2000 the UK was 90% compliant with the requirement of the Directive to provide secondary treatment for discharges from agglomerations of more than 15,000 pe.
By the end of 2002 the UK expects to be 98% compliant as a further 59 discharges, including all those in Scotland, will then receive secondary treatment. Work to provide secondary treatment for the remaining discharges will be completed as soon as practicable.
At the end of 2001 92 Sensitive Areas were identified in the UK. All except the three new sensitive areas (eutrophic) in Northern Ireland (Inner Belfast Lough, tidal River Lagan and Quoile Pondage) which were announced in December 2001 are shown in the maps from pages 11 to 13. More sensitive areas are expected to be identified in 2002 following reviews in 2001. More stringent treatment (than secondary) at qualifying sewage treatment works affecting identified areas (as at end 2000) has either been provided, or is to be in place at the latest by end 2004.
The Directive also allows the option of identifying LESS SENSITIVE AREAS, where at least primary treatment of discharges to coastal and estuarine waters is considered sufficient to protect these waters. In 1994 76 of these areas were designated around the UK. However, in 1998 most of these designations were revoked and work put in hand to provide secondary treatment for discharges to these areas. Northern Ireland has recently revoked its last two less sensitive areas, at Bangor and at Portush/Portstewart. Scotland has three less sensitive areas at Kirkwall, Lerwick and Stornoway.
Page published 25 April
2002;
Page last modified
29 September, 2002