Abstract: A thermo-oxidizer evaporator is provided with a combustion chamber, burners, and waste water injection system. The waste water injection system is preferably adapted to atomize the waste water stream. The waste water is injected near the flame from the burners so as to evaporate water in the waste water stream and combust contaminants in the waste water stream. The water leaves the combustion chamber as vapor, and contaminants collect at the bottom of the combustion chamber as dry ash. Heat exchange apparatus heats air prior to injection into the combustion chamber. A temperature controller controls fuel and air flow into the combustion chamber. Baffles in the combustion chamber increase the residence time to facilitate the settling of solid constituents from the gas stream leaving the combustion chamber. Methods for treating liquid wastes are also disclosed.