An electrocoagulation treatment device includes a plurality of spaced reaction plates disposed within a reaction chamber. A voltage is applied to selected reaction plates to create an electrical field within the electrocoagulation chamber. The plates are arranged vertically which induces a vertical flow of liquid through a device. Gases formed in the electrocoagulation process are allowed to rise and can be vented to the atmosphere. The solids which precipitate out of the liquid stream are carried by the liquid stream to secondary separation. The device includes various embodiments adapted for use as a large industrial unit, a portable unit or for use within the home. The device may be operated in a pressure controlled environment, thus eliminating the need for a pump. The voltage and amperage of the electrical field chamber may be adjusted by placing selected reaction plates in electrical contact with the voltage source.