Abstract: The invention relates to an electrolysis method that uses iron particles and an aqueous solution containing sodium hypochlorite. The method is characterized in that said method uses direct current, the iron particles form the anode (46) and the sodium hypochlorite concentration of the aqueous solution is at least 1 g/L. The invention further relates to a method and to a plant for the pretreatment of raw water for producing water that can then be easily treated in order to produce drinkable water or a so-called technical water that cannot be consumed but that can be used for household, agricultural or industrial applications such as cleaning, washing, laundry, flushing, garden watering or irrigation.