Abstract: An improved system and novel components and methods for treating waste waters contaminated with a variety of commercial, municipal, and/or industrial contaminants. A mixing vessel according to the invention comprises upper and lower mixing chambers connected by an intermediate tubular section and a fluid exit tube running coaxially down the center of the intermediate tubular portion. The fluid stream to be treated flows in a spiral pattern vertically through the vessel, providing turbulent flow. The flow stream may be subjected to electric or magnetic fields. In one embodiment, streams of the fluid to be treated and of an ionized coagulant are combined prior to entry into the vessel; in another embodiment, the incoming flow stream is combined with the coagulants in the mixing vessel. The incoming flow may be split between annular passageways to improve mixing. Magnetite particles may be generated in situ and added to the flow stream to further encourage coagulation in the presence of a magnetic field.