The present invention relates to a process of treating contaminated water containing microorganisms comprising feeding a contaminated water stream at a volumetric flow of about 1 to about 1000 m3/h through an electrolyser zone, said water stream having a conductivity from about 0.0001 to about 100 S/m, electrolysing said water stream in said electrolyser zone defined by at least one electrode pair enabling treatment of microorganisms, said at least one electrode pair comprising an anode and a cathode without separator means, said water stream being guided substantially perpendicularly through said at least one anode and cathode while imposing a voltage across said anode and cathode and supplying a direct current to said anode and cathode, withdrawing from the electrolyser zone a treated water stream. The invention also relates to an electrolytic cell in which said process can be performed, and to the use of the electrolytic cell.