A high-pressure (20 MPa) and high-temperature (350 o C) liquid water processing environment was used to treat various wastewaters and model compounds. Organics were converted to methane and carbon dioxide in the presence of a fixed bed of nickel or ruthenium catalyst. Nitrates were destroyed by reaction with methanol in the presence of a nickel catalyst. Noncatalytic hydrolysis of carbon tetrachloride and chloroform was also demonstrated. Three scales of continuous-flow reactors were used in these tests. Extended tests to demonstrate catalyst lifetimes were also performed. Several examples of test results with actual industrial waste streams showed that this process can be effectively used with appropriate catalysts to clean wastewater and recover waste organics as useful fuel gas