e-Digest Statistics about: Inland Water Quality and Use
Influences on freshwater quality and their control
Compliance with discharge standards
It is an offence to cause or knowingly permit pollution of controlled waters. Discharges may, however, be made under and in accordance with a discharge consent granted by the regulatory authorities (i.e. Environment Agency, Scottish Environment Protection Agency, and Environment and Heritage Service). Consents only apply to point source discharges and may be granted subject to conditions limiting the terms on which discharges can be made. In setting conditions, the regulator takes account of the quality standards for the receiving waters which will reflect the use to which they are to be put.
In 2004 there were about 100,000 water quality discharge consents in force in England and Wales. Of these, there were nearly 8000 'significant' consented discharges from sewage treatment works or trade (industrial) sites. 'Significant' discharges tend to be those with a flow greater than 5m³/day. The remainder of the 100,000 discharge consents belong to smaller sewage or trade discharges (less than 5m³/day) and other discharges such as storm overflows, emergency overflows and septic tanks. Most sewage treatment works discharges are small. Only about 1,600 serve population equivalents greater than 2,000 and only around 700 serve population equivalents greater than 10,000.
Table 16 summarises results for the UK for 1995 to 2004 of tests of rolling compliance with discharge standards for those works with numerical conditions. The percentage of works in compliance with standards varies substantially from region to region. The rolling compliance measures operator performance over the last 12 months against their consent conditions. The instantaneous standard measures gross failures - i.e. if an operator had a gross failure of a consent condition, then immediate enforcement action could be taken for failure of that standard. SEPA has previously reported compliance as a combination of the rolling compliance and instantaneous standards. From 2005, the compliance target will be based on 12 month rolling compliance to give direct comparability with England and Wales.
Some smaller works have only descriptive conditions. This partly reflects historical differences between regions in the stringency of standards and partly regional differences in the sewage operators' improvement programmes. Over time discharge standards have been substantially tightened, and so trends in compliance rates significantly under-estimate improvements in performance in reducing pollution.
In Detail:
Further Information:
Data Tables:
| Table
No. |
Title | Download
file type |
| 16 | Compliance with numeric discharge consents: 1995-2004, United Kingdom |
- Internet Links:
- For national and local information see:
- England and Wales: Environment Agency - Discharges to rivers and coasts
- Scotland: Scottish Environment Protection Agency - Discharge Consent Compliance
- Northern Ireland: Environment and Heritage Service - Regulation of Discharges
- Department of the Environment in Northern Ireland
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Page last modified: 6 February 2006
Page published: 6 February 2006