An apparatus for separating water from a water-and-oil mixture, comprising: a first and a second elongated separator vessel, each said first and second elongated separator vessel having at its upper end an oil collection portion including an electrode and at its lower end a water collection portion including a water level control;and, each said first and second elongated separator vessel having an inlet located below the electrode and above the water level control and an oil outlet, the electrode being arranged to subject a water-and-oil mixture exiting the inlet and entering the elongated separator vessel subject to an electric field, the inlet to the second elongated separator vessel being the oil outlet of the first elongated separator vessel, the inlet arranged to provide a predetermined direction of flow within the elongated separator vessel of a water-and-oil mixture entering the elongated separator vessel; wherein each first and second elongated separator vessel further comprises a water outlet at its lower end configured to carry away water that has been separated by the system from the water-and-oil mixture; and wherein longitudinal axes of the first and second elongated separator vessels are parallel to each other and oriented at an incline relative to a horizontal plane and the oil outlet of the first elongated separator vessel is directly coupled to the inlet of the second elongated separator vessel by a short connection from the oil outlet at the oil collection portion of the first separator vessel to the inlet of the second separator vessel; and further wherein the electrodes are only located in each elongated separator vessel and each elongated separator vessel has only one electrode portion. a first and a second elongated separator vessel, each said first and second elongated separator vessel having at its upper end an oil collection portion including an electrode and at its lower end a water collection portion including a water level control;and, each said first and second elongated separator vessel having an inlet located below the electrode and above the water level control and an oil outlet, the electrode being arranged to subject a water-and-oil mixture exiting the inlet and entering the elongated separator vessel subject to an electric field, the inlet to the second elongated separator vessel being the oil outlet of the first elongated separator vessel, the inlet arranged to provide a predetermined direction of flow within the elongated separator vessel of a water-and-oil mixture entering the elongated separator vessel; wherein each first and second elongated separator vessel further comprises a water outlet at its lower end configured to carry away water that has been separated by the system from the water-and-oil mixture; and wherein longitudinal axes of the first and second elongated separator vessels are parallel to each other and oriented at an incline relative to a horizontal plane and the oil outlet of the first elongated separator vessel is directly coupled to the inlet of the second elongated separator vessel by a short connection from the oil outlet at the oil collection portion of the first separator vessel to the inlet of the second separator vessel; and further wherein the electrodes are only located in each elongated separator vessel and each elongated separator vessel has only one electrode portion.