Supercritical Water Oxidation: Testing of Ersatz Wastewater

Supercritical Water Oxidation (SCWO) technology is under consideration by NASA for treatment of wastewater and other wet waste streams. The dramatic changes in water's thermophysical properties near its critical point (374 °C and 218 atm) result in nearly complete solubility of organics and gases. The absence of interphase phase transport processes and phase separation results in dramatically reduced reaction timescales. Organic waste conversions in SCWO are complete and result in product streams that are microbially inert, benign and highly compatible with resource recovery schemes.

This paper first describes the design and construction of a tubular SCWO reactor built at NASA Glenn. The reactor consists of separate "fuel" (i.e., watewater) and oxidizer inlets, which are independently heated and pressurized to conditions near the critical point of water. These independent injection streams are then either (i) premixed or (ii) injected as separate co?axial reactant streams upon introduction into the main reactor chamber, having a volume of 50 cc. The reactor section is heated to desired operating temperatures within a range of 450 °C - 650 °C. A pressure regulator maintains operating pressures between 230 atm and 250 atm. The product stream is captured downstream of the pressure regulator during experiment runs and a separate vent line is used for collection of volatiles.

The results of the SCWO experiments, using proxy waste streams comprising ethanol/water solutions or ersatz wastewater simulants, provided by NASA Ames, are presented. Concentration measaurements fomr a Raman diagnsotic system are presented as the metric for the conversion efficacy of the organic and inorganic constituents. Of particualr interest are ammonium compounds, typically found in wastewater streams. Supplementary chemical kinetics modeling results of ethanol oxidation with and without inclusion of nitrogeneous compounds (e..g., ammonia) is also be presented.