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WO1999042382A9 - Procede de traitement de dechets et de preparation de materiaux de construction avec les dechets - Google Patents

Procede de traitement de dechets et de preparation de materiaux de construction avec les dechets

Info

Publication number
WO1999042382A9
WO1999042382A9 PCT/US1999/003690 US9903690W WO9942382A9 WO 1999042382 A9 WO1999042382 A9 WO 1999042382A9 US 9903690 W US9903690 W US 9903690W WO 9942382 A9 WO9942382 A9 WO 9942382A9
Authority
WO
WIPO (PCT)
Prior art keywords
waste
amended
agent
phosphate
percent
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Ceased
Application number
PCT/US1999/003690
Other languages
English (en)
Other versions
WO1999042382A1 (fr
Inventor
Charles E Baldwin
Alioune Sogue
Richard T Jensen
Joseph D Mckaig
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Rocky Mountain Remediation Services LLC
Original Assignee
Rocky Mountain Remediation Services LLC
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Rocky Mountain Remediation Services LLC filed Critical Rocky Mountain Remediation Services LLC
Priority to AU27762/99A priority Critical patent/AU2776299A/en
Publication of WO1999042382A1 publication Critical patent/WO1999042382A1/fr
Publication of WO1999042382A9 publication Critical patent/WO1999042382A9/fr
Anticipated expiration legal-status Critical
Ceased legal-status Critical Current

Links

Classifications

    • C—CHEMISTRY; METALLURGY
    • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
    • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
    • C04B28/00—Compositions of mortars, concrete or artificial stone, containing inorganic binders or the reaction product of an inorganic and an organic binder, e.g. polycarboxylate cements
    • C04B28/34—Compositions of mortars, concrete or artificial stone, containing inorganic binders or the reaction product of an inorganic and an organic binder, e.g. polycarboxylate cements containing cold phosphate binders
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B09—DISPOSAL OF SOLID WASTE; RECLAMATION OF CONTAMINATED SOIL
    • B09C—RECLAMATION OF CONTAMINATED SOIL
    • B09C1/00—Reclamation of contaminated soil
    • B09C1/08—Reclamation of contaminated soil chemically
    • C—CHEMISTRY; METALLURGY
    • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
    • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
    • C04B2111/00—Mortars, concrete or artificial stone or mixtures to prepare them, characterised by specific function, property or use
    • C04B2111/00474—Uses not provided for elsewhere in C04B2111/00
    • C04B2111/00767—Uses not provided for elsewhere in C04B2111/00 for waste stabilisation purposes
    • C—CHEMISTRY; METALLURGY
    • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
    • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
    • C04B2111/00—Mortars, concrete or artificial stone or mixtures to prepare them, characterised by specific function, property or use
    • C04B2111/10—Compositions or ingredients thereof characterised by the absence or the very low content of a specific material
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02W—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO WASTEWATER TREATMENT OR WASTE MANAGEMENT
    • Y02W30/00—Technologies for solid waste management
    • Y02W30/50—Reuse, recycling or recovery technologies
    • Y02W30/91—Use of waste materials as fillers for mortars or concrete

Definitions

  • the present invention relates to the field of treating wastes, including environmental media and other materials. More particularly, the present invention relates to a method of treating solid and liquid-containing wastes, whether such wastes are ordinary debris or are hazardous, toxic or radioactive wastes or combinations thereof, including, for example, wastes containing contaminants, pollutants, asbestos, pesticides, herbicides, polychlorinated biphenyls and metals. Such constituents may be defined in federal and state environmental, health and safety statutes such as RCRA, CERCLA, TSCA, AEA or subsequent statutes.
  • the current invention provides a simple method in which these diverse waste forms may be stabilized and encapsulated by treating the waste with a phosphate agent, with or without other additives, and compacting the amended waste.
  • Waste may also be classified as hazardous if it satisfies the criteria of "ignitability,” “corrosivity,” “reactivity” or “toxicity” as these terms are defined in applicable regulations.
  • Whether a waste meets the "toxicity" characteristics depends upon whether the waste leaches an unacceptably high level of a hazardous substance during a leaching test.
  • Contaminants considered to have toxic characteristics include the so-called “heavy metals,” including for example, arsenic, barium, cadmium, chromium, lead, mercury, selenium and silver.
  • Land disposal regulations prohibit the land disposal of wastes which exceed the maximum allowable concentrations when the waste is subjected to a leaching test.
  • Wastes failing the test must be treated appropriately to reduce leaching below the established limits or a permit or variance obtained.
  • leaching tests generally attempt to mimic the slightly acidic leaching conditions encountered at the interior of a municipal landfill site.
  • the United States Environmental Protection Agency has established a rule which requires that waste to be deposited in a landfill have an unconfined compressive strength of 50 pounds per square inch; this is to ensure adequate structural support for landfills.
  • Several general strategies have been developed to meet the foregoing requirements or at least to partially stabilize wastes.
  • the method probably most infrequently used is a method in which the waste is washed with a reagent capable of dissolving contaminants so they can be flushed from the waste.
  • the solubilized contaminants are subsequently removed from the rinse solution by precipitation or filtration.
  • this method suffers from lengthy processing time and cost.
  • Methods employing a washing step are described in U.S. Patents 5,009,793 to Muller and 5,045,115 to Ginunder.
  • a second method involves solidification.
  • This approach utilizes binders to produce an end product having low permeability characteristics, thereby significantly reducing the rate at which contaminants leach from the waste.
  • the solidification approach often involves the use of grout, cement, lime and/or silicates as the solidifying agent.
  • This treatment approach is limited by the fact that such treatments are costly, significantly increase the volume of the waste and often require long curing periods. Examples of this approach are U.S. Patents 4,049,462 to Cocozza; 4,375,986 to Pichat; 4,615,643 to Gouvenot and 5, 150,985 to Roesky.
  • Some methods utilize starting materials, such as fly ash, which have inherently high silica concentrations.
  • Chemical stabilization or fixation comprises a third method. These methods involve addition of one or more chemical additives to the waste so that contaminants are converted into an insoluble form.
  • a common chemical stabilization method for treating wastes contaminated with heavy metals is to add an alkaline reagent to produce insoluble metal complexes. This approach can be problematic in that certain metals may only form insoluble complexes within a narrow pH range. Lime and sodium carbonate are reagents typically used in this approach.
  • U.S. Patents utilize this method, including U.S. Patents 4,737,356 to O'Hara and Surgi; 4,671,882 to Douglas; 4,701,219 to Bonee;
  • Another chemical stabilization technique is to use phosphate compounds, usually in conjunction with a buffering agent or a secondary complexing agent, to stabilize heavy metal-containing wastes.
  • phosphate compounds usually in conjunction with a buffering agent or a secondary complexing agent.
  • Several U.S. Patents are directed at using phosphate compounds solely to treat lead-contaminated materials. Illustrative of this group are U.S.
  • the current invention provides a method for treating or stabilizing a variety of wastes.
  • the wastes may be solids, liquids or combinations thereof.
  • the wastes may include ordinary debris, including but not limited to, aggregate, glass, metal, plastic, paper, concrete, asphalt, wood, ceramics and combinations thereof.
  • the waste may also be a hazardous or toxic waste containing heavy metals, contaminants, or pollutants, or be a radioactive or mixed waste.
  • the method can be used to stabilize hazardous wastes containing, for example, contaminants, pollutants, asbestos, pesticides, herbicides, polychlorinated biphenyls, metals and combinations thereof.
  • the invention provides a method for treating such wastes by combining the waste with a phosphate agent and then compacting the amended waste mixture to form a solid material which encapsulates and stabilizes the waste.
  • a phosphate agent a phosphate agent
  • other additives such as fly ash, a metal oxide agent, an oxidizing agent or combinations of these can be added.
  • the method has the advantage of utilizing inexpensive and readily available materials and can be carried out at room temperature.
  • the method produces a solid monolith which stabilizes contaminants by both chemical and physical means such that the final product reduces the leaching of contaminants to below current regulatory limits.
  • the final product also exhibits high compressive strength and can be formed into any number of predetermined shapes.
  • the current invention also provides construction forms or materials prepared from a starting material, wherein the starting material includes contaminated soils and soil- containing compositions, mine tailings, mill tailings and combinations thereof.
  • FIG. 1 is a schematic diagram of a method for producing treated and compacted waste from solid waste according to the present invention.
  • FIG. 2 is a schematic diagram of a method for producing treated and compacted waste from liquid-containing waste according to the present invention.
  • FIG. 3 is a graph illustrating how compressive strength increases as the concentration of phosphate agent is increased.
  • This invention addresses the need to develop new methods for the treatment or stabilization of various waste forms such that the end product meets regulatory and disposal requirements for a number of waste streams.
  • the terms “treating” or “stabilizing” wastes are meant to refer to processes in which the waste is physically and/or chemically modified so that pollutants and/or contaminants located in the waste or material do not leach from the treated or stabilized material; the terms may also include processes which result in treated materials that can withstand physical and/or chemical degradation or forces.
  • waste is meant to generally refer to materials which are no longer deemed to be of value or to have use in their current form, including environmental media and other materials.
  • Waste may more specifically include hazardous waste, radioactive waste and mixed waste.
  • Such waste can include metal- contaminated waste, for example waste which is contaminated with heavy metals such as arsenic, cadmium, chromium, lead, mercury, selenium, silver and nickel.
  • Wastes may also contain contaminants, pollutants, asbestos, pesticides, herbicides, polychlorinated biphenyls, metals and combinations thereof.
  • Such constituents may be defined in federal and state environmental and safety statutes, such as RCRA, CERCLA, TSCA or AEA.
  • Solid waste does not mean solid waste as defined under RCRA, but refers to waste which is neither a liquid or gas.
  • Radioactive waste refers to wastes that are Naturally Occurring or Accelerator Produced Radioactive Material (NORM/NARM) or which contain radioactive contaminants as defined in the Atomic Energy Act (AEA).
  • Mated wastes are meant to refer to wastes which contain hazardous and radioactive contaminants. It is possible using the method of the present invention to encapsulate hazardous, radioactive and mixed wastes into a compacted and solid monolith which facilitates disposal.
  • This invention is also applicable to treating secondary waste streams from other processes such as soil washing and thermal treatment processes. Additionally, the method described herein can also be used to encapsulate debris including, but not limited to, paper, plastic, concrete, asphalt, wood, metal, glass, aggregate, ceramics and combinations thereof. This capability allows the disposal of secondary wastes from processing and construction which would otherwise require other treatment and disposal options.
  • this invention can utilize phosphate agents other than just phosphoric acid.
  • dry phosphate powders which, when combined with water, or when combined with water already present in the waste, can be safely and easily added to the waste form, thus making the process much more amenable to field operations.
  • the method has the additional advantages of being able to be performed at room temperature and can be accomplished economically with commonly used soil handling equipment at minimal capital cost. Further, this method is capable of using only a phosphate agent in conjunction with compaction to stabilize wastes; unlike many other methods, it is not necessary to add other additives.
  • sulfate agents including, for example, gypsum, anhydrite, alum and halites
  • carbonate agents including, for example, simple carbonate salts as well as lime and Portland cement
  • complexing agents including, for example, Fe(II), Fe(III) or A1(III)
  • metal oxides including, for example, MgO, CaO, FeO, Fe 2 0 3 and Fe 3 0 4 ), or hydroxides
  • the phosphate agents used in the present method effectively react with the contaminants in a waste, even wastes having very high concentrations of contaminants, to form stable compounds in which the leach rates are below regulatory limits.
  • this stabilization is a consequence of the phosphate agent reacting with contaminating metals to form highly insoluble metal phosphate complexes.
  • the metallic ion is inactivated and no longer participates in its usual chemical reactions.
  • the phosphate binder reacts with other constituents in the waste to form a matrix which further impedes leaching of the metal contaminants. Decreased permeability is also achieved by the compaction step.
  • the result is a hard ceramic-like material which binds contaminants and constituents in the waste by both chemical and physical means and thus has long-term stability for disposal.
  • the volume reduction also permits increased waste loading at disposal sites and the potential for using the compacted amended waste as a construction material, including, but not limited to, disposal pit liners.
  • solid waste feed material is preferably size reduced to less than 4 centimeters in all dimensions. Typically, such size reduction is achieved by grinding and then screening the ground waste. Grinding or pulverizing of the solid waste can be accomplished using equipment such as hammermills, ballmills, jawcrushers and shredders appropriate to the waste form. Screening is done using stationary or vibratory screen systems. The grinding step, however, does not require formation of a powder in which the average particle size is at the micron level.
  • a solution containing phosphate agent is prepared from a concentrated form of phosphate agent diluted with water. Although the use of a solution is preferable, it is possible to apply the phosphate agent as a dry powder, especially if the waste feed has sufficient inherent moisture.
  • the "phosphate agent” provided for in the invention is meant to broadly include chemicals capable of supplying a phosphate anion, including polymeric compounds.
  • a non-exhaustive list which illustrates the scope of such chemicals includes phosphoric acid and its salts.
  • the phosphoric acid salts may be of the monobasic, dibasic or tribasic form.
  • the counterion of these salts may include, but is not limited to, sodium, potassium, magnesium, calcium, aluminum, iron, zinc and ammonium ion, or combinations thereof.
  • the phosphate agent may come from a mineral source such as fluorapatite
  • phosphate rock used here to mean the naturally occurring rock which consists primarily of calcium phosphate.
  • the phosphate agent may also be in the form of single superphosphate, superphosphate and triple superphosphate, forms of phosphate which can be obtained from standard commercial fertilizers.
  • Superphosphate refers to a mixture of calcium sulfate and calcium phosphate; it is typically prepared by adding sulfuric acid to phosphate rock, bone ash or basic slag.
  • Triple superphosphate is defined as the P 2 0 5 such as can be found in commercial fertilizers.
  • the phosphate agent is a metaphosphate compound, a pyrophosphate or polyphosphoric acid or a salt thereof.
  • Polyphosphoric acid is defined to mean chemicals having the general formula of H n+2 P n 0 3n+1 where n is greater than 1. Polyphosphates include the salts of polyphosphoric acid.
  • the phosphate agent may also be a long chain compound including, for example, sodium hexametaphosphate (available from Monsanto in powder or granular form; CAS No. 68915-31-1).
  • the counterions associated with these chemicals may include those listed above for the phosphoric acid salts.
  • Combinations of the foregoing chemicals may also be used.
  • determining the effective amount of phosphate agent to employ in order to achieve a compacted amended waste which significantly reduces metal leaching it is useful to conduct an initial screening test with a small but representative sample of the waste to be treated.
  • the amount of phosphate agent required will depend upon the amount of contaminant in the waste and on the characteristics of the waste. In general, however, when the phosphate agent is phosphoric acid, 5 to 20 percent of phosphoric acid by weight is sufficient (unless stated otherwise, all phosphate agent weight percentages are expressed relative to the weight of the initial solid waste). In the case of triple super phosphate (TSP), 3 to 20 percent of TSP will effectively immobilize metal contaminants. Higher concentrations of hydroxyapatite and fluorapatite tend to be required; typically, 10 to 50 percent by weight is sufficient.
  • the phosphate agent is hexametaphosphate (HMP)
  • HMP hexametaphosphate
  • dry powdered sodium HMP is added to water, preferably in the concentration of 1.75 kg per liter.
  • the amount of HMP added to the waste varies but, based upon the dry weight of the powder, 0.5 to 8 percent by weight relative to the initial waste is typical and 1 to 3 percent by weight is preferred.
  • the solid waste feed material is then preferably mixed with the phosphate agent solution to yield an amended waste. It is possible to add one or more additives to the solid waste in the combining step as well. These additions may be prior to, at the time of, or after the phosphate agent is mixed with the solid waste. Like the solid waste, the debris is preferably size reduced to 4 centimeters or less in all dimensions prior to addition.
  • secondary waste or debris may also be mixed with the solid waste.
  • debris may include, but is not limited to, paper, plastic, concrete, asphalt, wood, metal, glass, ceramics and combinations thereof.
  • the amount debris added is 10 percent or less of the solid waste by volume.
  • Fly ash may also be added to the solid waste.
  • fly ash is meant to include by-products in the combustion of coal in large power plants.
  • the fly ash is Class C or Class F fly ash which can be purchased from a variety of sources.
  • the fly ash is generally added to provide additional strength to the compacted product.
  • the amount of fly ash added preferably does not exceed 25 weight percent based on the initial weight of the waste, and may be less than 15 weight percent in some instances.
  • metal oxide agent is meant to include metal oxides generally, and MgO, CaO, FeO, Fe 2 0 3 and Fe 3 0 4 in particular.
  • the amount of metal oxide agent added is typically less than 50 percent by weight relative to the initial solid waste; in some cases, the percentage by weight may be less than 15 percent.
  • An oxidizing or reducing agent may also be included in order to achieve the desired oxidation state of a particular metal.
  • suitable oxidizing agents include salts of hypochlorite (for example, Ca(OCl) 2 and NaOCl) and hydrogen peroxide.
  • the mixing or combining of the solid waste, phosphate agent and additive(s), if any, can be performed in any type of mixer which can adequately blend the components into a uniform mix, including, for example, a pug mill or other standard mixing equipment.
  • the phosphate agent can be pumped using conventional pumping into a spray bar which is located in the mixer and the phosphate agent sprayed over the mix.
  • the phosphate agent is typically added in minutes and mixed with the solid waste and any additives until the phosphate agent is uniformly distributed throughout the mix, thus yielding an amended waste.
  • This combining step can often be accomplished in as little as five minutes or less.
  • the moisture content of the amended waste is preferably 10 percent or less by weight. Based on the moisture content of the amended waste, additional water may be added as necessary to achieve the preferred moisture levels.
  • the preferred water content will also depend upon the physical characteristics of the solid waste and can be varied so that after compaction a physically stable product is obtained.
  • the general term "compaction” as used herein is defined to mean not just the addition of pressure, but the application of force which results in densification and volume reduction of the original material.
  • the term “harmonic compaction” refers to a method for fusing particles by rapidly accelerating and decelerating particles within a mold having at least one moveable side. Accelerations of at least 25 G's to 50 G's, and preferably several hundred to several thousand G's, are required. These rapid accelerations and decelerations are preferably accomplished by rapidly impacting opposing ends of mold between an oscillating member and a pneumatic ram.
  • the oscillating member is a table which rapidly reciprocates upward and downward and the pneumatic ram is part of an under damped pneumatic system adjusted to oscillate out of phase with the oscillating member.
  • the oscillating member propels the mold from itself toward the pneumatic ram.
  • the pneumatic ram is initially compressed backward but then rebounds, forcing the mold back toward the oscillating member. Deceleration and impact occurs as the pneumatic ram moves the mold toward the oscillating member which is simultaneously moving in the direction of the returning mold.
  • the oscillating impacts are repeated over and over in rapid succession, resulting in the desired compressive forces.
  • the frequency of the reciprocating movements of the oscillating member and the pneumatic ram must be appropriately timed to achieve the necessary impacts. Movement of the mold may be at the harmonic frequency of the oscillating member, hence the name harmonic compaction.
  • Patents 4,531,903 and 4,456,574 to Frey and Wier describe an example of a harmonic compactor and methods for achieving harmonic compaction.
  • the compaction step can also be accomplished using conventional compaction methods, i.e., non-harmonic compaction methods which do not involve the rapid accelerations and decelerations which characterize harmonic compaction.
  • Conventional compaction techniques and compactors may include vibratory compaction using vibratory tampers, plate compactors and rollers.
  • Compaction may also be accomplished using kneading compaction utilizing, for example, tamping rollers, sheepsfoot rollers, mesh or grid pattern rollers, and rubber tire rollers.
  • Static compaction may also be employed, including, for example, the use of compaction presses and hand-operated tampers.
  • Dynamic compaction is another option, including, for example, the dropping of weights. Any of the compactors, whether they be conventional or harmonic, may be at a fixed site or part of a mobile facility.
  • Compaction forces will vary depending on the composition of the amended waste and on the intended use of the compacted amended waste, but typically a force up to 3,000 pounds per square inch is applied. Volume reductions up to and greater than 50 volume percent are achieved depending on the composition of the original waste feed and the compaction force which is applied. Typically, compaction achieves a volume reduction of at least 20 percent.
  • the compacted amended waste is allowed to cure at room temperature.
  • Curing times vary and, in general, compressive strength increases with increasing cure time. However, adequate product strength is typically obtained within about one hour to approximately one month; generally, the cure period is approximately 7 days..
  • contaminated starting materials including contaminated soils, soil-containing compositions, mine tailings, mill tailings and combinations thereof (see FIG. 1).
  • the contaminant may include, but is not limited to, asbestos, pesticides, herbicides, polychlorinated biphenyls, metals and radioactive material.
  • the process described above effectively encapsulates such contaminants, thereby resulting in low leach rates from the construction form.
  • the compaction step it is possible using many of the compacting devices listed above to compact the mixture (starting material, phosphate agent and additive(s), if any) into any number of desired shapes.
  • bricks having a square, rectangular, hexagonal or "T" shape can be formed.
  • presses designed specifically for manufacturing bricks have been patented and could be used in the current invention, including the presses described in U.S. Patents 5,145,692 to Hereford; 4,640,671 to Wright; 4,559,004 to Augier; and 4,035,128 and 4,050,865 to Drostholm, et al.
  • a water-proofing agent may also be added to the construction form to enhance its durability when exposed to water.
  • the agent can be included during the combining/mixing step or applied after the construction form has been produced.
  • the water-proofing agent may include, but is not limited to, polyvinyl alcohol, polyurethane and asphalt emulsions.
  • liquid-containing waste is meant to include a liquid waste or a waste of which a significant portion is a liquid. More specifically, the term is meant to include wastes in which the water composition of the waste by weight is approximately 10 percent or more. Thus, the term is meant to encompass sludges, slurries and liquids.
  • the general method described above for solid waste applies (see FIG. 2 where the broken lines indicate an optional step).
  • a primary difference is that in a combining step the liquid portion preferably is initially reduced to approximately 10 percent by weight by adding an additive to absorb part of the liquid.
  • This additive may include any number of materials, but preferably includes soil, a quantity of debris, fly ash, a metal oxide agent, an oxidizing agent or combinations of these (terms are as defined above).
  • a compressible amended waste is formed which can be compacted using the procedures and apparatus described above.
  • Phosphate agent can be supplied in either solid or liquid form.
  • the type and concentration of phosphate agent is as described for solid waste treatment. If fly ash is added, it typically is added in an amount less than 25 percent by weight relative to the liquid-containing waste, and may be less than 15 percent.
  • a metal oxide, if added, is typically less than 50 percent by weight that of the initial waste; it may be less than 15 percent by weight. If debris is included, the amount added is typically 10 percent or less of the liquid-containing waste by volume.
  • Compaction may be accomplished using either the conventional compaction methods (e.g., vibratory, kneading, static or dynamic methods) or harmonic compaction method described earlier in the section on treating solid wastes.
  • the compacted amended waste is sufficiently stabilized through chemical and physical means so that contaminants and pollutants are immobilized, thereby satisfying regulatory leaching criteria, especially for metals.
  • in-situ waste treatment It is possible to treat and compact waste at its original site rather than compacting the waste at a site separate from the treating site.
  • This method of treating is referred to herein as "in-situ" waste treatment.
  • the initial step in this process is to obtain a representative sample of the waste to assess the amount of phosphate additive necessary. Multiple samples may be required if the site to be treated is large.
  • the treatment site is then divided into sections.
  • the appropriate amount of phosphate agent is then applied.
  • the phosphate agent may be applied in liquid or solid form.
  • phosphate agent may be evenly distributed over the treatment site.
  • the combining step may be accomplished, for example, by raking in the phosphate agent to an approximately uniform depth or by using standard rotary tillers that are either manually operated or attached to a tractor. If a quantity of debris, fly ash, metal oxide agents and/or oxidizing agents are also to be added, these materials may be combined with the waste in a like manner.
  • the phosphate agent For sites in which the contaminated zone runs more than a few feet below the surface, it may be necessary to apply the phosphate agent as a solution or slurry. Liquid application alone may be adequate for sufficiently porous soils. In other cases, it may be necessary to apply the phosphate agent and any other materials by first perforating the soil or by the use of injection nozzles which can be inserted to sufficient depths.
  • compaction may be performed in a number of ways. For example, kneading compaction may be employed by using a variety of rollers. Dynamic compaction methods utilizing pneumatic tampers or methods in which weights are dropped may also be used. Compaction can also be achieved by driving heavy machinery over the treatment site, in which case the tires provide the necessary compressive force.
  • compositions comprising a contaminated starting material and a phosphate agent, with or without the additives described above.
  • This composition has numerous applications including, for example, forming construction materials, especially bricks.
  • the composition has additional utility as a mortar to bond the construction forms provided for by this invention as well as other construction materials.
  • the construction materials or forms provided by the present invention comprise a compacted mixture including a phosphate agent and a contaminated starting material.
  • the construction material may also include debris, fly ash, a metal oxide agent and/or an oxidizing agent.
  • the contaminated starting material or waste may include contaminated soils, soil-containing compositions, mine tailings, mill tailings and combinations of these.
  • a non-exhaustive list of potential contaminants includes, asbestos, pesticides, herbicides, polychlorinated biphenyls, metals and radioactive waste.
  • the phosphate agent included in the composition includes those chemicals described above in the waste treatment section and is present at the levels listed earlier.
  • the composition may include one or more of the additives (debris, fly ash, metal oxide agent and/or oxidizing agent) at the concentration ranges listed earlier.
  • the composition is a compacted mixture.
  • the construction form is compressed to less than 3,000 pounds per square inch, and preferably between approximately 1,500 and 2,300 pounds per square inch, although the actual pressure will depend upon the nature of the starting material and the intended use of the construction form.
  • fly ash is a component in the composition, pressures may exceed 2,500 pounds per square inch.
  • the construction form typically has a density of approximately 128 pounds/in 2 ; at 40 percent volume reduction, the density is approximately 170 pounds/in 2 . Final densities are dependent upon the starting material and compressive pressure.
  • the construction form may be of a predetermined shape.
  • the options with regard to the final shape are essentially limitless. In general, a shape is desired which enables multiple construction forms to be interlinked with one another, thereby enhancing their use in construction projects. Examples of construction forms having particularly useful shapes include, but are not limited to, rectangular, square, hexagonal, and T-shaped bricks.
  • the construction form may also include a first interlocking member. Such a member might include, for example, a hole running through the construction form through which a connecting rod might be inserted to assist in stabilizing a stack of construction forms. More preferably, the construction form includes a first and second interlocking member, such that an interlocking member on one construction form is capable of interlocking with an interlocking member on another construction form.
  • a construction form may have a first and second face which are on opposing sides of the construction form.
  • a first interlocking member might be located on the first face; the second interlocking member might be located on the second face.
  • the interlocking members would be sized so that a first interlocking member on one construction form would be capable of interlocking with the second interiocking member on another construction form.
  • the first interlocking member might include a ridge, whereas the second interlocking member might include a depression sized to accommodate the ridge on another block. Numerous other variations on these general approaches could be successfully utilized.
  • the construction form composition may also include a water-proofing agent to increase the stability of the construction form when exposed to water for extended periods.
  • a water-proofing agent to increase the stability of the construction form when exposed to water for extended periods.
  • Numerous water-proofing agents could be utilized, including, for example, polyvinyl alcohol, polyurethane and asphalt emulsions.
  • An important feature of the present composition of the construction forms is its effectiveness in binding the contaminants within the composition, thereby resulting in a composition which can be prepared primarily from waste materials yet which exhibits leach rates which are below regulatory limits, especially for metals. As described earlier, this stabilization or immobilization of contaminants is a consequence of the phosphate agent forming a complex with the contaminant and also binding to constituents in the soil to form a matrix which limits leaching.
  • the construction forms have excellent strength, as well as good durability and workability.
  • the forms have the additional advantage of being in a form which provides for facile handling and transport; they can also be produced at room temperature using standard soil handling
  • the construction forms comprise compacted mixtures, the overall volume of the contaminated starting material is reduced, thereby decreasing the space needed if the forms are placed in a landfill.
  • the construction forms can also be utilized in various construction projects including, for example, pit liners, erosion control systems, construction barriers, road beds, embankments and retaining walls.
  • Example I Treatment of Sand/Clay Samples One waste type treated included soil samples composed primarily of sand and clay. Clay comprised 20% to 40% of the sample composition by weight and sand comprised the remaining 60 to 80%.
  • the sand/clay samples were tested on a bench-scale (0.25 pounds of waste material/block) and at full-scale (36 pounds of waste material/block). In field tests, the sand/clay samples were screened to obtain material which was less than 4 centimeters in all dimensions.
  • the phosphate agent employed in this test was dry, powdered sodium hexametaphosphate (HMP) purchased from Monsanto. HMP was added to water in the concentration of 1.75 kg per liter of water; dissolution was achieved at room temperature.
  • HMP sodium hexametaphosphate
  • the compacted amended waste was allowed to cure for approximately 7 days.
  • Compressive strengths were determined using a point load machine (e.g., an InstronTM machine) according to ASTM methods (unless otherwise stated, all compressive strength values are reported in kg/cm 2 ; these values can be converted to pounds per square inch by multiplying by 14.22).
  • Volume reduction i.e. the extent of compaction, was determined by subtracting the volume of the compacted amended waste from the bulk volume of the starting waste (including debris, if any), dividing the difference by the volume of the starting waste and then multiplying by 100.
  • TCLP Toxicity Characteristic Leaching Procedure
  • the TCLP methodology involves agitating a 100 g sample, randomly obtained from the waste being tested, in 2 liters of a specified extraction fluid after first sizing the waste to smaller than 3/8 inches or 9.5 mm. The agitation step is continued for 18 hours using a rotating agitator which is operating at a speed of 30 revolutions per minute. A sample of the extraction fluid is then tested for the particular contaminant or contaminants of interest.
  • TCLP results were within the regulatory limits established for the metals tested (cadmium, chromium and lead), except for cadmium at the bench-scale level when debris was included. Compressive strength was well above the test objective of 70 kg/cm 2 . Volume reductions of 28 to 44 percent were achieved.
  • Example II Treatment of Buried Waste Samples
  • HMP solutions were used to supply the phosphate agent and treatment and testing conditions were generally as described in Example I. Tests were performed at the bench-scale and full-scale level. Tests at the bench-scale level were done with and without added debris. As shown in Table 2, TCLP tests were conducted for cadmium, chromium and lead; the TCLP limits were met for each of these metals. Compressive strengths were well above the test objective of 70 kg/cm 2 , with or without the addition of debris, ranging from 318 to 409 kg/cm 2 . Significant volume reduction was also achieved, ranging from 43 to 64 percent.
  • Example V Dependence of Compressive Strength on Phosphate Agent Concentration
  • the dependence of the compressive strength of the compacted amended waste as a function of phosphate agent concentration was also examined.
  • Samples were composed of sand/clay mixtures. Different aqueous solutions containing increasing concentrations of HMP were prepared (0.70, 1.0, 1.20 and 1.75 kg/1). The waste samples were treated and compacted as described in Example I.
  • Compressive strength was determined using a point load machine (e.g., an InstronTM machine in compressive mode) according to ASTM methods. As shown in FIG. 3, compressive strength increased with increasing binder concentration. In particular, compressive strength doubled (600 psi to 1200 psi) as the concentration of HMP was increased from 0.70 kg/1 to 1.75 kg/1).
  • Grade 1 means the brick is nondispersive under the test conditions just described. In particular, no clay suspension is noticed in the dish used for the test; thus, the brick is classified as insoluble in water after 24 hours of immersion.
  • Grade 4 means the brick is dispersive. In this case, bricks subjected to the test disintegrate in water in less than 24 hours; thus, the bricks are classified as soluble in water.
  • Table 5 summarizes the results of the compressive strength and CRUMB tests.
  • the first number in the Sample I.D. in Table 5 represents HMP concentration; the second number represents fly ash concentration.
  • sample 1B-15A contained 1 percent HMP and 15 percent fly ash by weight, relative to the weight of the starting material.
  • the results show that compressive strength increased with increasing phosphate concentration. Yet, even at very low concentrations of HMP, excellent compressive strength was obtained. In all cases except one, the bricks were nondispersive as defined according to the CRUMB test.

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Ceramic Engineering (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Soil Sciences (AREA)
  • Environmental & Geological Engineering (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Inorganic Chemistry (AREA)
  • Materials Engineering (AREA)
  • Structural Engineering (AREA)
  • Organic Chemistry (AREA)
  • Processing Of Solid Wastes (AREA)

Abstract

L'invention concerne un procédé de traitement de divers matériaux notamment de déchets contenant des solides et des liquides. Ces matériaux peuvent comprendre des déchets communs ou des déchets dangereux, radioactifs ou toxiques. Ce procédé consiste à combiner les déchets à un agent phosphaté et le cas échéant à d'autres additifs, par exemple à une certaine quantité de détritus, de cendre volante et/ou un oxyde métallique, afin de produire des déchets modifiés qui sont ensuite compactés. Ce procédé permet d'obtenir un matériau dur de type céramique dans lequel les agents phosphatés lient chimiquement et physiquement les contaminants et les composants aux déchets, réduisant ainsi dans une mesure importante la libération par lessivage des métaux lourds, des éléments contaminants et des polluants hors des déchets et permettant d'obtenir un monolithe qui présente une résistance élevée à la compression et qui a subi une réduction de volume importante. Les déchets peuvent être compactés sous différentes formes de manière à pouvoir être utilisés comme matériau de construction.
PCT/US1999/003690 1998-02-18 1999-02-18 Procede de traitement de dechets et de preparation de materiaux de construction avec les dechets Ceased WO1999042382A1 (fr)

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US09/025,754 1998-02-18

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WO2007051479A1 (fr) * 2005-11-02 2007-05-10 Ciwatec Gmbh Procede et dispositif de traitement de dechets contenant des substances toxiques
ITMI20131426A1 (it) * 2013-08-30 2015-03-01 Consorzio Interuniversitario Nazion Ale Per La Sci Metodo per la decontaminazione di substrati inquinati da sostanze organiche ed elementi pesanti
CN107583945B (zh) * 2017-10-31 2021-05-28 爱土工程环境科技有限公司 一种有机污染土壤生产烧结砖的方法
CN109122143B (zh) * 2018-09-14 2021-02-05 国家地质实验测试中心 一种根系微地球化学障技术修复重金属污染抛秧种植水稻田的工艺
TWI783486B (zh) * 2021-05-18 2022-11-11 國立高雄科技大學 無戴奧辛危害之飛灰再生粒料製程
CN113332654B (zh) * 2021-05-25 2023-02-28 昆明理工大学 一种大宗固废基环保粉体材料的制备方法

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USRE32329E (en) * 1978-03-20 1987-01-13 Method of adhering mineral deposit in wood fragment surfaces
US5732367A (en) * 1990-03-16 1998-03-24 Sevenson Environmental Services, Inc. Reduction of leachability and solubility of radionuclides and radioactive substances in contaminated soils and materials
US5162600A (en) * 1990-12-28 1992-11-10 Rheox, Inc. Method of treating lead contaminated soil
FR2712726B1 (fr) * 1993-07-15 1995-12-15 Commissariat Energie Atomique Procédé de conditionnement de déchets radioactifs utilisant des apatites silicatées comme matrice de confinement.
US5512702A (en) * 1993-11-08 1996-04-30 The Ohio State University Research Foundation Method for in-situ immobilization of lead in contaminated soils, wastes, and sediments using solid calcium phosphate materials
US5678233A (en) * 1994-09-14 1997-10-14 Brown; Paul W. Method of immobilizing toxic or radioactive inorganic wastes and associated products
US5645518A (en) * 1995-01-31 1997-07-08 The University Of Chicago Method for stabilizing low-level mixed wastes at room temperature
US5674176A (en) * 1995-02-16 1997-10-07 Entact, Inc. Method for treatment of solid waste to minimize heavy metals
JPH08299935A (ja) * 1995-05-09 1996-11-19 Takei Teruo 特殊セメント系固化剤廃棄物処理用組成物
US5830815A (en) * 1996-03-18 1998-11-03 The University Of Chicago Method of waste stabilization via chemically bonded phosphate ceramics
US5846894A (en) * 1996-03-18 1998-12-08 The University Of Chicago Phosphate bonded structural products from high volume wastes

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WO1999042382A1 (fr) 1999-08-26
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