Abstract: A method of treating solid waste in soil or solid disposed waste containing unacceptable levels of leachable metals, such as lead, cadmium, arsenic, zinc, copper and chromium, includes mixing the solid waste or soil in place with a phosphate source or a carbonate source or ferrous sulfate. After the solid waste and the additive are mixed, if needed an additional pH controlling agent is mixed into the soil or waste and additive. After the solid waste and additive and pH controlling agent are mixed under conditions which support reaction between the additive, pH controlling agent and metals, the metals will be converted to non-leachable forms which are relatively stable under normal environmental conditions.

Abstract: An apparatus for injecting a mixture of pure oxygen or oxygen-enriched air (at least 25 percent oxygen) and purge water into a wet oxidation reactor operating at elevated temperature and pressure. An annular space between the oxygen carrying pipe and a second, larger pipe is filled with heat transfer resisting material, either maintained static or passed through the annular space to remove heat therefrom. The temperature of the oxygen and purge water is maintained at less than 250.degree. F., preferably less than 150.degree. F. to minimize evaporation of the purge water. Thus, backflow of organic matter into the oxygen pipe is prevented; plugging of the oxygen pipe by salts is also prevented.

Abstract: A method comprising operating steps required for safely operating wet oxidation reactors in which combustible substances are oxidized at elevated temperatures and pressures using pure oxygen. The steps satisfy the criteria that a potential of oxidation is established prior to introducing oxygen and maintained until after oxygen flow is stopped; that an inert gas, either from an external source or generated in situ, is present in the reactor from before oxygen flow is introduced until after oxygen flow is stopped; and that the oxygen introducing means is clean for oxygen use from prior to the introduction of oxygen flow until after the oxygen flow is stopped.

Abstract: A continuous process for wet oxidation of aqueous liquor containing combustible matter using oxygen or oxygen enriched gas. An inert diluent gas is injected into the aqueous liquor or reactor off-gas such that oxygen in the gas phase is diluted by the sum of generated water vapor, produced carbon dioxide and injected inert gas to a concentration less than required for spontaneous combustion at every location in the system having surfaces not continually exposed to a continuous liquid water phase.

Abstract: An improvement in the wet oxidation of caustic waste liquors wherein carbon dioxide produced in the wet oxidation is recycled to raw caustic waste to neutralize the latter, thereby reducing the corrosive nature of the waste.