The invention relates to a method and a system for purification of water in a water purification system. The water purification system comprises first and second mixing reactors, first and second flotation reactors and first and second filters all serially and fluidly connected in a flow direction of the water as well as an electrolyzer. During the process, electrochemical synthesis of the reagents takes place in the cathode and anode chambers of the electrolyzer, respectively. Moreover, the electrochemically synthesized catholyte and anolyte are dosed into the water kept in the first and second mixing reactors, respectively. Then the mixtures in the first and second mixing reactors are mixed. After that, the flow of the treated water leaving the mixing reactors is passed through the first and second flotation reactors and afterwards through the first and second filters downstream of the first and second mixing reactors.