WIT Press

Uncertainty Of Ammonium Nitrogen Determination In Wastewater


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A Drolc & M Roš


The measurement uncertainty of result of ammonium nitrogen determination in wastewater was evaluated. Ammonium was determined using distillation and titration method (IS0 5664). The major sources of uncertainty of the result of measurement were identified: preparation of the sample, preparation of the reagents, titration and overall repeatability of the procedure. Identification and evaluation of uncertainty sources was followed by combined uncertainty calculations. The results show that the major sources of uncertainty arose from repeatability and volumetric steps, thus leading to the conclusion what is the target operation for reducing the measurement uncertainty of this determination. 1 Introduction The determination of the ammonium nitrogen in wastewater is of highest importance for control of industrial and municipal wastewater treatment plants operation, wastewater effluent monitoring and taxation of wastewater pollution. The result of a measurement is only an estimate of the true value of the measurand, and therefore needs to be accompanied by an estimate of the uncertainty -the range of the stated results. It is now widely recognised that the evaluation of the uncertainty associated with a result is an essential part of any quantitative analysis. The \“Guide to the Expression of Uncertainty in Measurement” [1], published by the International Organization for Standardization established general rules for evaluating and expressing uncertainty for a wide range of measurements. The IS0 gude has subsequently been interpreted for analytical chemistry by Eurachem [2]. The guide recommends uncertainty be estimated from its components and by using rules for