Incineration rules explained
The Waste Incineration and Large Combustion Plant directives are likely to impact on many operators, but what are the Environment Agency's requirements and how can mistakes be avoided?
The Waste Incineration Directive (WID) came into force on 28 December, 2005, while the Large Combustion Plant Directive (LCPD) will apply fully within another two years.
All of the installations covered by the WID, and LCPD installations above a certain thermal rating, will need to have continuous emission monitoring systems (CEMs).
These CEMs will in turn require quality assurance to EN14181, Quality Assurance of Automated Measuring Systems. So, during the next two years, a large and growing number of operators will have to apply EN 14181.
While there are now many test laboratories offering services to EN 14181, the Environment Agency (EA) and STA have observed a wide spectrum of quality in the application of the standard.
EN14181 specifies three levels of quality assurance, plus an annual surveillance test (AST). Under EN 14181, test laboratories have a critical role in the application of QAL2 and the AST for the calibration and verification of CEMs.
The core of both the QAL2 and AST procedures is a set of parallel tests using standard reference methods (SRMs). The purpose of the SRMs is two-fold.
Firstly, test laboratories use SRMs to establish the relationship - known as the calibration function - between the true value of the determinand in the stack, and the output of the CEM.
Secondly, the data from the SRMs can be used to determine whether the uncertainty of the CEMs is low enough, by analysing the scatter on the graph of corresponding measurements from the SRMs and CEMs.
This is known as the variability test. Valid calibration-functions and accurate variability-tests depend on a wide-enough spread of data, and an accurate and precise application of the SRMs.
The EA requires test laboratories performing services to EN 14181 to be accredited to ISO 17025, the MCERTS performance standards for manual stack monitoring, and the appropriate SRMs.
However, we have observed significant mistakes by some accredited laboratories, meaning that the application of QAL2 tests did not meet the requirements of EN 14181.
Mistakes made For example, even though EN 14181 requires a spread of data for a valid calibration function, this is often difficult to achieve in practice as a lot of data is seen in clusters.
Following trials of EN 14181, the EA, STA, process operators and test laboratories involved in these trials found the following:
Despite specifying these requirements in the guidance on EN 14181, the following examples have been seen several times:
Even if the SRMs were performed to the required accuracy and precision in the above cases, the QAL2 and AST applications would be flawed. But there have been cases where even the application of the SRMs was questionable.