Abstract: An apparatus comprises a settling chamber having an outlet pipe to discharge purified liquid and communicating with an electrocoagulation chamber in whose bottom part a system of soluble electrodes is disposed. The electrocoagulation chamber has an inlet pipe to feed contaminated liquid, disposed above said system of soluble electrodes, and an inlet pipe to feed electrolyte, disposed below said system of soluble electrodes. A separating partition with an aperture and a check valve as well as an injector to deliver a fluid under the check valve are installed in the electrocoagulation chamber between the system of soluble electrodes and the inlet pipe to feed contaminated liquid, the check valve being adapted for a vertical movement under the action of the flow of the fluid delivered by the injector and of the flow of a gas-liquid mixture, ascending from the system of soluble electrodes.