Abstract: The invention concerns a method of treating liquids by means of oligodynamy, particularly of sullage waters. The waters are passed between metal electrodes supplied with electric current before being allowed to settle. The waters which have been subjected to the oligodynamic treatment are then submitted to at least one positive degassing operation and/or a part at least of the flocculate being formed is recovered and said flocculate is re-introduced into the water which has just flowed between the metallic electrodes. The flocculate resulting from the treated waters is then separated.