Aim of the studyThe main aim of the research was to verify the thesis that formal and legal restrictions on the use of phosphorus compounds, particularly polyphosphates, in detergents extensively introduced in recent years reduced the concentration and load of this nutrient in raw sewage inflowing to the selected treatment plant. Additionally, it was tested whether the phosphorus decreasing in raw sewage reduced the concentrations and loads of total phosphorus in treated sewage, and thus reduced negative sewage anthropopressure of the water body.
Material and methodsThis paper presents observations accumulated during the 15-years study (2003)(2004)(2005)(2006)(2007)(2008)(2009)(2010)(2011)(2012)(2013)(2014)(2015), the concentrations and loads of total phosphorus in domestic sewage flowing into the selected treatment plant, as well as in treated sewage discharged into the receiving water body. A total of 148 samples of raw sewage and 114 samples of treated sewage were collected over the research period. The concentration of the total phosphorus in wastewater was determined by spectrometry with ammonium molybdate. The research results were analysed with the aid of advanced statistical analysis using, among others Mann-Kendall test, Kolmogorov Smirnov test, elements of descriptive statistics, as well as regression analysis with selected significance tests.
Results and conclusionsBased on the research, it was stated that multidirectional activities implemented both in Poland and Europe with the view to phosphates limitation in detergents have significantly reduced the concentration and load of this nutrient in domestic sewage inflowing to the treatment plant. Over the past 15 years, the total phosphorus concentration in household wastewater has decreased from 14.4 to 5.7 mg • dm -3 , i.e. by 60.4%. The observed tendency corresponds to the decrease in the unit load value per 1 inhabitant. This parameter decreased by 68% from 2.25 mg • person -1 • d -1 in 2003 to 0.72 mg • person -1 • d -1 in 2017. The total phosphorus concentration in treated sewage discharged from the tested sewage treatment plant decreased from 5.1 to 2.0 mg • dm -3 , i.e. by 60.8%, in the years 2003-2017. The observed regression of phosphorus content in the wastewater discharged into the sewage system translates into lowered risk of anthropopressure for flowing waters and the Baltic Sea, mainly in the aspect of initiating the eutrophication process. Based on the research, it was found Kaczor, G. B. (2020). Changes in concentrations and loads of total phosphorus in domestic and treated wastewater over a 15-year observation period in terms of limiting... Acta Sci. Pol., Formatio Circumiectus, 19 (2), 3-14.