Supercritical water oxidation of a model municipal solid waste

Supercritical water oxidation has been focused on as an environmentally attractive technology by which organic materials can be oxidized to carbon dioxide, water, and nitrogen gas. We applied supercritical water oxidation to the treatment of dog food as a model municipal solid waste. The reaction was carried out in a batch reactor with hydrogen peroxide as the oxidant over the temperature range of 673-823 K. The liquid reaction products were analyzed to determine the total organic carbon (TOC), organic acid, and ammonium ion contents. When the oxidant was stoichiometrically insufficient, TOC decreased with an increasing temperature and amount of oxidant. Acetic acid and ammonium ion were detected as major refractory intermediates. Ammonium ion was completely decomposed more easily than in sewage sludge, presumably because hydrochloric acid produced Cr ion by corrosion of the wall of the reactor. The activation energy was 97.2 kJ/mol for the reduction of TOC and 130.8 kJ/mol for the reduction of ammonium ion, when analyzed by first-order kinetics.