Treating surface waters for rendering them drinkable, comprises e.g. pre­chlorinating water with specified dose of chlorine for specified period of time and coagulating with aluminum sulfate

The invention relates to a method for treating surface waters for rendering them drinkable. According to the invention, the method consists of that, in the first stage, there is performed the water pre­chlorinating with doses of 2.0...2.5 mg Cl2/l at a contact time of 30...60 min for water primarily disinfecting, coagulating with Al2(SO4), with doses of 2.5...3.0 mg Al3+/l, followed by decanting for 1 h which performs the separation of the organic compounds, afterwards there follows a stage of stage 1 post­chlorination with 2.0...2.5 mg Cl2/l at a contact time of 30 min, followed by the final post­chlorination with 0.60...0.70 mg/l of chlorine, which provides the final chloramination with the concentration reduction for trihalomethanes at values of 1 .8...2.5 ug/l.