Assessment and control of odour nuisance from waste water treatment: code of practice

Voluntary code of practice on odour control from sewage works.


1.1 Scope and Structure of this Code

There are many different measures that can be used to prevent, reduce or control odour nuisance from waste water treatment works ( WWTW). It is acknowledged at the outset that these facilities are likely to produce odours from time to time. This Code of Practice (CoP) provides a framework within which Scottish Water and its contractors, other WWTW operators and local authorities can operate to minimise the impacts of such odours, and identify steps to tackle odours of a significant nature.

This CoP will be of interest to all stakeholders involved with, and affected by, odour from WWTW. Part 1 of this CoP is specifically written to assist local authority Officers and the public in the investigation and assessment of potential odour nuisance from WWTW. Parts 1 and 2 of the CoP will assist when considering enforcement action against odorous works in forming a view on whether the operator has instigated measures which reflect the use of the best practicable means to control odour nuisance. The public, from whom odour complaints invariably arise, will find this CoP better informs them of the possible sources of odours, the steps involved in assessment of complaints and the complexity of the task the operator sometimes faces in implementing control measures.

The contents on Part 2 will be of particular relevance to operators as it outlines technical and management controls that are appropriate for the control of odour, because of their responsibility and ability to put in place the measures to prevent, stop or minimise odour problems from their plant.

Part 2 of this CoP describes appropriate measures which include:

  • the general management of the WWTW;
  • the design, installation and maintenance of plant, buildings and structures
  • the operation of the WWTW and its processes; and
  • engineering solutions, e.g. containment, enclosure with venting and end-of-pipe treatment

There is no simple "one-size fits all" solution to odour problems: often there is a combination of measures that go towards resolution of the problem. These can range from very simple (and often very inexpensive) measures, to very complex (and often costly) measures. Therefore, it is important that a timely, realistic, cost effective and proportionate approach is taken to resolve odour issues.

1.2 Legal Status of this Code

This is a voluntary CoP in that it is not underpinned by new legislation and therefore does not confer any new obligations or rights on any party. Its purpose is to inform both operators and regulatory agencies of the best practicable means of administering the existing legislation available within the Statutory Nuisance provisions contained within Part III of the Environmental Protection Act 1990. The Scottish Executive intends to produce statutory codes of practice on odour control at sewerage works by April 2006, using new powers granted to Scottish Ministers contained within the Water Services etc Act (Scotland) 2005.

This CoP is based on the state of knowledge and understanding at the time of writing. It draws on research work carried out for Defra and the Scottish Executive and may be amended from time to time to keep abreast of new developments.

1.3 What this Code applies to

This CoP focuses specifically on odour nuisance from WWTW. Whilst there are many potential odour sources at waste water facilities, this CoP applies to odour nuisance from WWTW themselves, rather than to the wider sewerage network.

This CoP does not apply to the small number of WWTW which are subject to the Integrated Pollution Prevention and Control ( IPPC) regime regulated by the Scottish Environment Protection Agency ( SEPA) under the Pollution Prevention and Control ( PPC) Regulations. Separate guidance on the applicable standards for these processes will be produced in due course by SEPA.

In addition there may be some sites subject to the waste management licensing regime of Part II of the Environmental Protection Act 1990. However, in many cases the waste management licence will only apply to a limited range of operations at WWTW. In this case it is recommended that the local authority and Scottish Environment Protection Agency agree a common approach. In the final assessment of odour, the provisions of this CoP should apply to all releases from a WWTW that are likely to lead to potential odour nuisance.


Email: Central Enquiries Unit

Back to top