Wastewater treatment is essential to protect aquatic ecosystems by removing harmful substances, including excess nitrogen and phosphorus. Nitrogen and phosphorus are nutrients that, if left unchecked, can lead to eutrophication, causing algal blooms and oxygen depletion in water bodies. Monitoring of nitrogen and phosphorus concentrations in wastewater allows optimisation of the treatment process, reducing operational costs. Effective wastewater treatment reduces the risk of nutrient pollution, which is the main driver of water quality deterioration worldwide. The aim of this work was to develop and validate a method for the determination of total nitrogen and phosphorus by ion chromatography (IC). Alkaline persulfate digestion was used as a method for determining total nitrogen and phosphorus. Alkaline digestion was performed with NaOH and K₂S₂O₈ solutions. Validation was performed by evaluating parameters such as linearity, limit of detection, limit of quantification and accuracy and Grubb's test was performed. The method did not meet the linearity criterion with a coefficient of determination of less than 0.9900. The accuracy of the method was shown by the injection precision and preparation precision parameter and was within the limits of 89 – 112% and the absence of systematic error was determined. The precision proved to be more satisfactory for use in the determination of phosphate ions than nitrate ones. Both the limits of quantification and the limits of detection for both compounds were determined. Grubb's outlier test detected three pieces of data as outliers.