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. The voltage and amperage of the electrical field chamber may be adjusted by placing selected reaction plates in electrical contact with the voltage source. One embodiment is adapted for treatment of fluid containing soluble or particulate organic compounds recalcitrant to biodegradation, including nitrogenous contaminants, such as ammonia or an ammonium compounds. The device and method of the invention include the use of an oxidizing agent such as sodium hypochlorite or hydrogen peroxide to aid in the removal of organic contaminants.