Patent Number: 048448397
Section: summary

BACKGROUND OF THE INVENTION This invention relates generally to treatment of hazardous wastes, and particularly to the in situ analysis of contaminants and treatment of hazardous waste disposal sites. In various industries it has been common practice to discharge aqueous, dry or semi-solid waste chemicals or radioactive materials into ponds, which waste material after a period of time tends to become pasty or solid due to the evaporation of water therefrom. After the waste material has assumed a substantially solid state, dry particles thereof that are exposed to the ambient atmosphere tend to become airborne and are a health hazard. In addition, the toxic material in such an impoundment tends to leach into the soil adjacent thereto as well as contaminate ground water. In the past, various methods have been proposed to lessen the danger inherent to such hazardous impounded materials, but such methods have not been effective. One such method includes the removal of a portion of the waste material, and erecting a concrete or betonite isolation wall in an attempt to contain the balance of the impounded material. Also it has been proposed to excavate the impounded material and transport the same to existing or newly built disposal sites that may or may not be sealed with a liner. However, when either of the above identified methods is used, the impounded material is subjected to mechanical action that renders a portion of it airborne with consequent health hazards. SUMMARY OF THE INVENTION A major object of the present invention is to provide an insitu method treating impounded toxic and radioactive materials, and one that transforms the impounded material into a solid substantially insoluble mass from which toxic materials will not leach out into adjoining land or water table, nor will any substantial surface particles of the mass become airborne even when the mass is subjected to elements of weather. Another object of the invention is to supply a method of treating hazardous impounded materials in such a manner that the danger of transporting the same over public highways is eliminated. A further object of the invention is to furnish a method of treating hazardous waste material that is more rapid to carry out and less dangerous to the personnel involved than prior art methods that attempted to attain the same results. A further object of the present invention is to treat an impoundment containing radioactive material to minimize the escape of radon gas therefrom and to render radioactive compounds in the impoundment insoluble to the extent that they will not leach out from the treated impoundment. The in situ impoundment treating an assembly of adjacently disposed, power driven, rotating cutter-injectors supported on the lower ends of vertically disposed hollow kelly stems or drill pipe that may move up and down. The assembly is supported by a boom or the like that extends outwardly from a power driven vehicle such as a tractor pipelayer crane or the like. The boom supported assembly may be extended out over the impoundment a substantial distance, while the power driven vehicle remains on solid land adjacent the impoundment. The assembly cutter-injectors are sequentially lowered into adjacent areas or stations of the impoundment while rotating to homogenize the hazardous waste material therein to a desired depth. After the desired depth has been reached, the cutter-injectors are moved upwardly while rotating, and simultaneously treatment chemicals for the hazardous waste material are injected therefrom. The depth to which the cutter-injectors are moved downwardly and then raised upwardly as above described produce different results. If the cutter-injectors are moved downwardly and then upwardly in only the land beneath the impoundment, an impervious liner to contain the hazardous waste may be formed without removing the hazardous material from the impoundment. By lowering the cutter-injectors to the bottom of the impoundment and the raising them upwardly, the entire contents of the impoundment may be transformed to an inert insoluble mass that has substantial strength, and may remain in place. Should the cutter-injectors be moved downwardly below the surface of the impoundment and then upwardly, a rigid cap of a desired thickness may be placed over the hazardous waste in the impoundment that will bear a substantial load and prevent particles of the hazardous waste becoming airborne. Released odors or toxic vapors that escape from the hazardous waste material during the treatment thereof, and that are not destructed by the treatment of chemicals, are reeded to the surface of the impoundment and collected for scrubbing within a confined space defined within a protective collection shroud that extends over the treating area. The multi-head rotating cutter-injectors are so spaced that the circular area through which they rotate overlap to assure complete mixing of the hazardous waste material being treated and the treatment chemicals therewith. Engineering values of the treated material may be predetermined by bench testing representative samples or are taken periodically to determine shear compression, and the load bearing strength of the treated material, and on the basis of these results the rate of injection of the treatment chemicals is varied to obtain treated waste having desired physical characteristics. The specific treatment chemical used will depend on the composition of the hazardous waste material which is determined by an analysis thereof. Waste materials found in impoundments include cyanide waste; toxic metals; metal plating waste; inorganic compounds that may be acid or base solvents and reactive sludges; pestiside compounds; halogenate and nonhalogenate volatile organics, transformed from oil and the like. Impoundments may also contain drilling muds and fluids; oily waste sludges; pasty sludges; pharmaceutical, agricultural and municiple waste water sludges; and low level radioactive waste and uranium mill tailings. The specific treatment chemicals selected for use at a particular impoundment can result in aqueous waste being dewatered and the volume thereof accordingly reduced. Free standing liquids are blended with the solid fraction to eliminate the removal of the liquid phase. Toxic substances in the impoundment are transformed into a stable, inert, insoluble sediment which may be solidified into a nonpermeable matrix. Waste odors or toxic vapors arising during the impoundment treatment are either chemically destroyed, or scrubbed to remove objectionable components prior to being released to the ambient atmosphere. Impounded hazardous waste are not removed from or surfaced on the impoundment during the present treatment method and exposure of workmen to toxic emitions is minimal or completely eliminated. Aqueous waste immediately after treatment are transformed into a dry, earthlike friable material that may be handled safely and transported by use of conventional earth moving equipment. The major chemical use in carrying out the insitu treatment to immobilize, detoxify, destroy or precipitate the toxic substances and transform them into an insoluble state as well as into a highly impermeable and dense matrix, includes limes in form of calcium oxide, calcium hydroxide and milk of lime and suitable clay products. Other chemical additives include a wide range of oxidizing additives of which sodium bisulfate, sodium hydrosulfite, chlorine dioxide, hydrogen peroxide, ozone and acids and alkaline products in various forms are examples. Other chemicals dependent on the composition of the waste material.