UKAS accreditation for odour emission assessment: From sample collection to olfactory analysis
12 December 2008, News release from OdourNet UK Ltd
The importance of standardisation and accreditation in environmental monitoring
Standardisation of environmental analysis techniques across a sector is
widely acknowledged as of fundamental importance in improving accuracy
and ensuring repeatability of results. UKAS (United Kingdom Accreditation
Service) certification has long been the benchmark for quality assurance and
compliance to environmental standards within the UK and using a UKAS
accredited supplier is associated with reducing the risk of paying for, or more
seriously, acting upon invalid results.
The importance placed by UK regulators on the quality of sampling and analysis services for environmental monitoring is clearly evidenced by the Environment Agency Monitoring Certification Scheme (MCERTS), which was introduced into the UK in 1998. The MCERTS scheme was introduced by the EA in order to provide a framework of standards to which monitoring of environmental emissions could be undertaken. The scheme covers instruments, monitoring and analytical services and enables industry to confidently choose services that meet regulatory requirements.
MCERTS initially focussed on continuous emissions monitoring systems (CEMs) for stacks, however, the scope was extended to cover continuous ambient air-quality monitoring systems (CAMs) and manual stack emission monitoring, which is split into two components - the certification of personnel and the accreditation of organisations carrying out stack emission monitoring.
Under the scheme, emissions testing laboratories are accredited by UKAS to ISO 17025 for the MCERTS performance standard to undertake regulatory sampling and analysis of component substances within emissions to air. To gain MCERTS accreditation, testing laboratories must prove that they carry out monitoring in accordance with appropriate standard methods (detailed within the technical reference documents M1and M2, produced by the Environment Agency), use appropriately trained MCERTS certified personnel and work within a quality management system. This in turn provides confidence to both industry and regulators that laboratories carrying out test work are technically competent, and can produce technically reliable results.
Businesses that make emissions to air are regulated by the Environment Agency in the form of a permit, which usually requires an operator to monitor their emissions to atmosphere. Permits for operators often specify that regulatory monitoring must be carried out using the appropriate standard reference methods, using an MCERTS certified laboratory. This requires any external testing laboratory undertaking monitoring to be accredited to ISO 17025 for the MCERTS performance standard and that staff undertaking the work are trained in the appropriate sampling techniques.
Standardisation within odour monitoring...
Odour is becoming an increasingly important environmental concern, especially within the industrial and wastewater sector, but in comparison to other environmental emissions, standardisation of techniques has been slow. This has been due in no small part to the challenges that are posed by odour in terms of the development of robust analysis and sample collection techniques, in this rather unique area of environmental science.
In 2003, a British standard for olfactometry was introduced (BSEN 13725:2003), offering an approved standardised method for odour analysis. The standard describes the method for odour concentration measurement by olfactory analysis carried out by a panel of human assessors (delayed dynamic olfactometry), and was the culmination of over a decade of work by a European standardisation working group. The standard basically defined how the odour concentration of samples of air collected from industrial sites could be determined in units that were relevant to assessing the environmental impact of malodours on human populations. Shortly after publication of this standard, both of the two main olfactometry laboratories in the UK successfully achieved UKAS accreditation to ISO 17025 UKAS for odour concentration measurement (delayed dynamic olfactometry) which greatly improved the market confidence in odour analysis techniques.
There was however still a large missing piece to the quality system. The main laboratories had gained UKAS accreditation for odour analysis of samples collected from industrial sites. However, there were no standardised procedures for actually collecting samples which were presented for analysis on site. This situation was exacerbated by the fact that the British Standard for olfactometry contained very little detail on how sampling should be conducted other than to highlight the importance of maintaining sample integrity (e.g. avoiding moisture in sample bags) and ensuring that samples were analysed within a set period.
The main problems associated with a lack of quality endorsed standardised sampling procedures for odour sampling are summarised below:
> A wide variety of different methods are applied by different odour sampling providers to collect odour samples.
> There is a lack of clear understanding of the factors that may influence odour sample integrity during and following collection.
> There are often inconsistencies in how odour emission results are calculated, presented and interpreted.
> This is a lack of formal training of sampling staff and absence of any procedural controls or checks to ensure minimum standards of performance are achieved and maintained.
> This is a lack of consideration of the applicability and uncertainty associated with different sampling techniques.
Some examples of how these problems manifest in odour survey work reviewed by Odournet over the last year are provided below:
There is an increasing requirement for companies to undertake assessments of odour treatment performance of their odour control plant to demonstrate compliance to licence conditions or design specifications. The large variety of different methods applied by odour monitoring companies and general lack of quality control and consistency means that it is not uncommon for different companies to obtain different results from the same system even when it is operating under identical conditions. This provides little confidence to operators who are interested in making an objective assessment of the performance of the odour control system, not the relative performance or sensitivities of the sampling procedures employed.
It is well documented within the British standard for olfactometry that maintaining the integrity of odour samples prior to analysis is of critical importance to obtaining a representative analysis result. However, contamination of odour samples by moisture and particulate matter remains a common problem. Although many companies employ methods to eliminate condensation of moisture within bags at the time of collection (e.g. static dilution of nitrogen), the application of such measures remains 'ad hoc' at best. Little if any attention is given to the prevention of condensation within sample lines during sample collection, or following collection during storage. In one case encountered by Odournet, the analysis results collected by a company on the same source indicated variations of over a factor 10, which were entirely associated with moisture contamination of the sample. This issue can be particularly problematic during performance testing of odour control units such as bioscrubbers, incinerators and wet scrubbers, where moisture levels within the air stream are likely to be high.
Odournet are often asked to provide peer review of odour studies conducted by other odour monitoring companies for odour. The most common errors in terms of reporting of odour survey results relates to the lack of consideration of the reference conditions during sampling and calculation of emission rates; the use of arithmetic rather than geometric means when averaging odour survey results; and a lack of consideration of the uncertainty associated and performance limits of the monitoring/analysis result to the objective of the project. All of these can cause significant problems in terms of interpretation and veracity of odour survey data. The lack of consideration of uncertainty of the olfactometry analysis technique when designing sampling strategies can make some assessments of odour control plant performance effectively worthless.
....the way forward
The way forward for overcoming these problems clearly relies upon the development of robust, documented quality procedures which ensure all influences on odour analysis results introduced during sample collection are well understood and controlled. In the absence of such procedures, it is understandable why plant operators and regulators will retain a critical view in relation to odour measurement results.
It is therefore encouraging to report that after many years of developing and implementing standardised odour sampling procedures, Odournet UK Ltd have become the first company in the UK to achieve full UKAS accreditation for their ODOUR SAMPLING AND ANALYSIS services combined, to the rigorous standards defined in international quality standard ISO17025: 2005. The award of this certification clearly demonstrates that robust quality control for odour sampling is both possible and achievable, and represents a step change in quality assurance of odour monitoring undertaken in the UK.
The development of UKAS accredited quality management methods for odour also provides a real prospect for the standardisation of odour sampling techniques which could only be seen as a benefit in this rather unusual area of environmental science.
On an international level Odournet remains actively involved in standardisation of odour measurement and sampling, through participating in national standardisation activities such as the German working group VDI3880 on odour sampling and in France AFNOR X43F in France. These activities can be expected to feed into a more comprehensive sampling standard to be included in the European EN13725 standard when it is next revised.
For further information please email OdourNet UK Ltd