The effectiveness of river bank filtration system on nitrate removal (Śrem site, Poland)

In the river bank filtration systems (RBF) the extracted water quality is strongly depending on source (river or lake) water quality. It is well known that these systems can effectively remove emerging contaminants (pharmaceuticals, personal care products or pesticides) from polluted river waters. The common river water contamination is related to nitrate which is observed at high concentrations commonly. Moreover, the nitrate concentrations in the rivers are usually very changeable seasonally. The current work presents the effectiveness of the RBF system in nitrate removal from polluted source (river) water. For this purpose, the water chemistry changes during filtration between the river and productive wells were used, while for identification of denitrification processes the isotopes of d¹⁸O and d¹⁵N dissolved in nitrate were used. The RBF site located in Śrem (Wielkopolska region, Poland) was selected for the presented research. The water samples were taken from the river and six continuously pumped wells. The water sample representing ambient groundwater was analysed as well. The wells at a close distance from the river (40-50 m) and the wells located at a greater distance from the river (70 – 95 m) were chosen for investigation. The visible differentiation of nitrate concentration was observed. The highest nitrate concentrations were observed in the river and wells located at a close distance from the river (~5 mg/l) and then the nitrate concentrations decrease (to a level of <0,5 mg/l). The spatial differentiation of the isotopes of d¹⁸O and d¹⁵N dissolved in nitrate is correlated with nitrate decrease and indicates that the denitrification processes are responsible for nitrate removal. The research presented demonstrates that RBF systems are reliable methods for nitrate removal from source water. This work has received funding from the National Science Centre of Poland (grant no. 2021/41/B/ST10/00094).