ODOUR MEASUREMENT AND CONTROL
Odour from waste-water treatment works and other operations such as waste facilities is a perennial problem particularly for those sites with houses nearby. As urban areas have expanded, pre-existing facilities on the edge of towns and cities have been surrounded by residential areas, bringing odour problems closer to people. Heatwaves increase the intensity of odour as temperature (and humidity) increases the evaporation of molecules, so odour problems may worsen with climate change increasing the frequency of extreme weather. Added to this, the regulation of pollution typically becomes stricter over time and communities demand more from regulators and industry. In the UK, a statutory nuisance abatement notice can be served by the local authority which can severely limit how a site is operated. Abatement notices stay in place with the site indefi nitely. In addition, water companies are driven by the Ofwat service incentive mechanism to reduce complaints logged from customers, or face a reduction in their “Ofwat score”. As the adage goes you can only control what you can measure. Accordingly, businesses have increased their expenditure to control and track odour impacts. But what is the defi nition of odour pollution? And how can it be measured, modelled and controlled?
Odour pollution is defi ned as ‘an offence to the senses’. In terms of regulation taking England as an example, the Environment Agency (EA) regulates waste sites and installations through permits to control environmental impacts. Environmental impacts, including odour incidents, are assessed and scored under a ‘Common Incident Classifi cation Scheme (CICS) using guidance (Box 1).
“There is an element of judgement by EA offi cers when assessing incidents [under the CICS] using the guidance framework, but the difference between a category 1 and category 2 odour incident is very obvious,” says Nick Sauer, Technical Advisor on waste at the EA.
Any potential breaches of permit conditions are assessed and scored under a Compliance Classifi cation Scheme (CCS). Under the environmental permitting regulations there are two objectives that are relevant to odour. The fi rst is that Best Available techniques (BAT) must be used to prevent, or if that is not possible, minimise pollution. (Across Europe the Industrial Emissions Directive (2010/75/EU) requires that BAT be implemented to prevent or at least minimise pollution.) The second objective is that unacceptable pollution must be prevented. If unacceptable pollution is caused and cannot be mitigated, then the EA has an obligation to revoke the permit for the site or installation. The EA can also refuse to
Box 1: Common Incident Classifi cation Scheme (CICS) Environment Impact Scores © Environment Agency, 2020
Category 1: Major serious, persistent and/or extensive impact or effect on the environment, people and/or property.
Category 2: Signifi cant impact or effect on the environment, people and/or property.
Category 3: Minor or minimal impact or effect on the environment, people and/or property.
Category 4: Substantiated incident with no impact. EA offi cer attended but no complaints were received.
Figure 1: Dashboard for a modelling software platform © Envirosuite, 2021. IET NOVEMBER / DECEMBER 2021
WWW.ENVIROTECH-ONLINE.COM permit sites where unacceptable pollution is anticipated.
In England, activities that cause odour are also regulated by the local authority, through statutory nuisance provisions under the Environmental Protection Act 1990. The local authority will issue a notice to control any activities, not just permitted sites, that cause a statutory nuisance. If a company or individual does not comply with the notice then the local authority can take enforcement action. For sites permitted by the EA, local authorities are required to obtain permission from the Secretary of State before they can
take enforcement action to avoid dual regulation by both the EA and the local authority.
Operators of facilities at risk of odour incidents can use monitoring (or modelling) to prevent complaints, achieve and prove their compliance with their permits, and defend themselves against odour complaints, to prove what the ambient odour levels were and/or that the odour originated elsewhere for example. Odour can be monitored at site boundaries or on site where odour control systems expel air. Various technologies are available, at a
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