The work concerns the effects of the treatment of groundwater contaminated with iron and manganese compounds taken from quaternary deposits. In the treatment process, a simple reagent-free technology based on aeration and rapid filtration processes was used. The article presents an analysis of the results of the quality of treated and abstracted water in the years 2008-2020. The period analyzed covers the modernization of the WTP, which was carried out in 2012. The purpose of modernization was to increase the efficiency of the WTP. After the modernization of the station, the efficiency of iron and manganese removal was found to be very high (99%), and the sequence of technological processes used was correct. The devices operated in the WTP work effectively by treating the water directed to the distribution system, which meets the Polish and EU quality requirements for water intended for human consumption.