Proficiency tests - Wastewater

"Länderübergreifende" proficiency tests (LÜRV; inter-state proficiency tests) - PT programme - Evaluation and assessment

In AQS Leaflet A-3 on water, wastewater and sludge testing, the Working Group of the Federal States on Water (LAWA) has specified the way in which proficiency tests (PTs) are to be carried out in the legally regulated environmental field.
In order to carry out these PTs in a uniform and harmonised manner throughout Germany, PT providers of the Länder and representatives of notification bodies of the Länder have come together in a planning group under the supervision of the responsible LAWA subcommittee. The following PT providers are involved:

  • Baden-Württemberg: AQS Baden-Württemberg at ISWA, University of Stuttgart
  • Hamburg: Institute for Hygiene and Environment of the Free and Hanseatic City of Hamburg
  • Lower Saxony: Lower Saxony State Office for Water Management, Coastal Protection and Nature Conservation, Hildesheim
  • North Rhine-Westphalia: State Agency for Nature, Environment and Consumer Protection, Duisburg
  • Saxony: State Operating Company for Environment and Agriculture, Nossen

The planning group jointly determines all key points for these PTs and the PTs are then carried out simultaneously by several PT providers in an identical manner.

The PT programme is based on the requirements of the Fachmodul Wasser (module water), in which the parameters relevant to water testing in the legally regulated environmental area are subdivided into several sub-areas:

Sub-area 1: Sampling and general parameters
Sub-area 2: Photometry, ion chromatography, titrimetry
Sub-area 3: Elemental analysis
Sub-area 4/5: Group and sum parameters
Sub-area 6: Gaschromatographic methods
Sub-area 7: HPLC methods
Sub-area 8: Microbiological methods
Sub-area 9.1: Biological methods, bioassays (part 1)
Sub-area 9.2: Biological methods, bioassays (part 2)

The Fachmodul Wasser can be found in the LAWA enquiry system ReSyMeSa for laboratories and technical experts.

The PT programme is determined by the Expert Committee AQA of the Standing Committee on Surface and Coastal Waters of the Working Group of the Federal States on Water on the proposal of the planning group.

The evaluation and assessment of these interlaboratory comparisons is based on the specifications of DIN 38402 - A45 and LAWA leaflet A-3 ("Interlaboratory comparisons for external quality testing of laboratories" from LAWA: AQS leaflets on water, wastewater and sludge analysis).
The assigned value is determined on the basis of the robust mean of the measurement results of all participants. The standard deviation necessary for the calculation of the zU scores is also derived from the measurement results of the participating laboratories. The planning group sets upper and lower limits for the standard deviation before the PT is provided, which are intended to prevent the tolerance limits and thus the quality requirements for the laboratories from becoming too sharp or too lax.
All participating laboratories receive a data evaluation sheet after completion of the evaluation, which shows the evaluation of this individual value for all measured values by marking with "s" for successful, "q" for questionable and "n" for non satisfactory. In addition, it is documented for each parameter whether it was determined "successfully" or "unsuccessfully". Parameters are classified as "successfully" if at least 50% of the reported results are within the tolerance limits. Parameters for which no results were submitted are marked "not participated".

Participants also receive a certificate for the interlaboratory comparison on which the parameter evaluation (successful, unsuccessful or not participated) is noted for each parameter.

A detailed evaluation report is also published on the AQS Baden-Württemberg website, which contains the results of all participating laboratories in anonymised form and is presented in tabular and graphic form.

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