Abstract: A process for treating wastewaters containing carbonaceous COD and at least one nitrogen-containing compound is disclosed comprising wet oxidizing the wastewater with an oxidizing agent at a temperature less than 373.degree. C. and a pressure sufficient to maintain a liquid water phase, to produce an oxidized wastewater containing a reduced concentration of COD. The nitrogen of the nitrogen-containing compound is substantially converted to ammonia, nitrate and nitrite. Sufficient inorganic nitrogen-containing compound is added to the oxidized wastewater to produce essentially equal concentrations of ammonia-nitrogen and nitrite-nitrogen plus nitrate-nitrogen. Mineral acid is added to the oxidized wastewater to produce a pH between 4 and 7, and optionally, a transition metal salt is added, to catalyze a thermal denitrification step. The wastewater is heated at temperatures between about 100.degree. C. and 300.degree. C. to decompose the nitrogen compounds, producing a purified wastewater.

Abstract: A process is described for monitoring pH in caustic liquor wet oxidation systems. An offgas carbon dioxide baseline value is established for the operating system where oxidized liquid effluent is at pH 7 or above. Offgas carbon dioxide content deviating by a selected proportion above the baseline vale indicates a drop in liquid effluent pH to 7 or less. Sufficient alkalinity is added to the raw wastewater to bring the effluent pH to 7 or above and prevent excessive corrosion to the materials of construction of the nickel-based or ferrous-based alloy wet oxidation system.

Abstract: A process is described for aerobically treating wastewater containing volatile compounds to degrade the volatile compounds without liberating them to the atmosphere. Influent wastewater and return sludge from an aerobic biophysical wastewater treatment system are contacted in a preaeration zone where a minimum dissolved oxygen concentration of about 1 mg/l is maintained. In this preaeration zone a significant portion of the volatile compounds are biologically degraded. The minimum oxygen concentration in the preaeration zone is attained by prior aeration of the return sludge or by adding a small amount of oxygen to the preaeration zone. The mixture of influent wastewater and biophysical solids depleted of volatile compounds then flows to an aeration zone for further removal of pollutants.

Abstract: This invention relates to a process and apparatus for dissipating the energy of a wet oxidation mixture after that stream traverses a pressure control valve. The depressurized stream is discharged into a phase separator vessel containing a gas phase and a liquid phase. The pressure control valve is positioned to discharge the oxidation mixture at a selected orientation below the surface level of the liquid phase in the vessel. This dissipates the energy of the mixture and prevents erosion of the phase separator vessel. The apparatus of the invention includes the separator vessel with gas and liquid phase exits, a control device for maintaining the liquid phase at the selected level in the vessel, a pressure control valve positioned at an aperture in the vessel for discharging the mixture below the surface level of the liquid phase in the vessel, and sealing device between the control valve and the separator vessel.

Abstract: An apparatus for mixing pressurized air with pressurized waste liquor at the inlet of a wet oxidation system heat exchanger device is disclosed. The apparatus is a T-shaped piping member with an inline first inlet and outlet and a second inlet oriented at about a right angle to said inline first inlet. The outlet is connected to an inlet tube of a tube and shell heat exchanger. A conduit supplies a pressurized waste liquor stream to the piping member through the second inlet. An oxygen-containing gas supply conduit, with circumferential sealing means, extends from exterior the T-shaped member, through the first inlet and terminates at a point beyond the intersection of the first and second inlets. The circumferential sealing means seals to the first inlet. The liquor entering the T-shaped member is heated to a selected elevated temperature prior to contacting a pressurized oxygen-containing gas supplied from the gas supply conduit.

Abstract: The invention is a process for purifying wastewater containing organic and color-causing pollutants. The three unit processes include a first stage aerobic or anaerobic biophysical treatment, a second stage oxidizer treatment, and a third stage adsorbent contact treatment. The biophysical treatment removes the majority of the pollutants while the oxidizer treatment destroys residual organics and color-causing pollutants. The adsorbent contact treatment destroys any residual oxidizer in the wastewater and/or adsorbs any residual oxidation products. The preferred adsorbent is powdered activated carbon and the preferred oxidizer is some form of chlorine, e.g. sodium hypochlorite. The process may be operated in either a continuous flow mode or a batch flow mode.

Abstract: A process for treatment of caustic sulfide liquor by wet oxidation in a ferrous-based alloy system at temperatures less than about 175.degree. C. is described. The liquor is first analyzed for alkalinity consuming species and for nonsulfidic alkalinity. If excess alkalinity consuming species is present compared to nonsulfidic alkalinity, then additional nonsulfidic alkalinity is added to the raw liquor such that excess alkalinity is present during wet oxidation treatment, thus preventing excessive corrosion to the ferrous-base alloy system.