This paper presents an evaluation of measurement uncertainty regarding the results of anion (nitrate and sulphate) concentrations in wastewater. Anions were determined by ion chromatography (EN ISO 10304-2, 1996). The major sources of uncertainty regarding the measurements’ results were identified as contributions to linear least - square or weighted regression lines, precision, trueness, storage conditions, and sampling. Determination of anions in wastewater is very important for the purification procedure, especially the amount of nitrate in waste and potable waters. The determined expanded uncertainty was 6.1 % for nitrate anions and 8.3 % for sulphate anions. The difference between measurement uncertainties determined by the two methods, the weighted and linear least - square methods, is negligible. [...]
This study investigated the effect of storage on certain sachet water quality indicators over a twelve-week period. Three brands of sachet water were collected within 24 h of production and analyzed for pH, nitrate, phosphate and dissolved oxygen. These were then placed in normal storage. According to out results, pH values increased significantly in all brands after week 8. Moreover, nitrate and dissolved oxygen values decreased throughout the investigation period, while phosphate values increased in all brands tested. All tested brands showed various degree of variation over the period of study. Still, all brands analyzed were within permissible limit by World Health Organization (WHO) stipulations. However, continuous storage can significantly alter the chemical quality indicators to a level that exceeds the limit set by WHO; hence, becoming harmful to human health. Therefore, it is recommended that sachet water should not be stored for more than 12 weeks from the date of production.
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