Free Motion for Summary Judgment - District Court of Federal Claims - federal

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Exhibit 14

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United States Patent i191
Pal et al.
[54] FIXATION AND STABILIZATION OF LEAD IN CONTAMINATED SOIL AND SOLID WASTE [75] Inventoi's: Dhiraj Pal, Chicago. Heights; Karl Yost, Crete, both of Ill. Assignee: MAECORP Incorporated, Chicago, [73] Ill. [21] Appl. No.: 721,935 [22] Filed: Jul. 23, 199i

US005193936A [ll] Patent Number:

5,193,936

[45] Date of Patent:
4,671,882 6/1987 4,701,219 10/1987 4,889,640 12/1989 4,935.146 6/1990

Mar. 16, 1993

Douglas el al ........L; ...... 210/912 X Bonee .................................. 106/118 Stanforth ............................ 210/751 O'Neill el al ................... 210/912 X Primary Examiner--David H. Corbin Attorney, Agent, or Firm--Andrew B. Katz; Leonard D. Bowersox [57] ABSTRACT A two-step treatment process is disclosed for application of lead-toxic wastesto fixate and stabilize leachable lead contained therein. The process, employs the use of a sulfate compound, such as gypsum, in a first step; and a phosphate reagent, stfch as phosphoric acid, in a seco.nd step. After thorough mixing and curing, a substantially solid end product is formed in which the lead is chemically fixed and remains in stabilized form for indefinite geologic periods. The process reduces Toxicity Characteristic Leaching Procedure lead levels below the regulatory threshold of 5 mg/l as required by the U.S. Environmental P.rotection Agency. The waste also beneficially undergoes volume reduction in a short curing time, and is applicable in a variety of situations. 20 Claims, 1 Drawing Sheet

Related U.S. Application Data Continuation-in-part of Set. No. 494,774, Mar. 16. 1990, abandoned. [51] Int. CIP ........................... B09B 3/00;.E02D 3/00 [52] U.S. CI ..................................... 405/128; 210/751; 405/263; 588/256 [58] Field of Search ............... 405/128, 129, 263, 266; 106/900; 210/751,912, 747; 588/256 [56] References Cited U.S. PATENT DOCUMENTS 4,443,133 4/1984 Barrett ................................ 405/263 4,530,765 7/1985 Sabherwal ...................... 210/912 X [63]

STEP T]" LIQUID REAGENT --1 (PHOSPHORIC ACID)

t (90
I

WATER
SUPPLY

PUGMILL (HOMOGENEOUS MIXI,NG)

CURING DRYING TREATED SOIL p~l:50 OR SOLID WASTE (NON-TOXIC BYTCL CRITERIA)

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STEP "IT FSO
LIQUID REAGENT (PHOSPHORIC ACID)
! t

'(,90~

#o ,,,
GRADING I ICONVEYOR

I OO'~I

I .SUPPLY I WATER

I

PUGMILL (HOMOGENEOUS MIXING)

!

CURING
DRYING

TREATED SOIL 1150 OR SOLID WASTE (NON-TOXIC BY TCLP CRITERIA)

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2

Effective Nov. 8, 1990, USEPA established the treatFIXATION AND STABILIZATION OF LEAD IN ment standard for lead wastes (D008), and particularly CONTAMINATED SOIL AND SOLID WASTE for lead contaminated soils and solid wastes, at a toxicity characteristic level of 5 milligrams per liter in the This application is a continuation-in-part of U.S. Pat. 5 extraction fluid according to the TCLP Test, The application Ser. No. 07/494,774, filed Mar. 16, 1990,.TCLP Test is much more rigorousmand is more uninow abandoned. formly applicable to a larger number of parameters--thar~.the EP Toxicity Test. It replaced the EP toxicFIELD OF THE INVENTION ity method for RCRA waste determination. The TCLP The present invention belongs to the field of chemicat 10 Test requires sizing of waste material to less than ~ treatment technology applicable to contaminated soils inches o~" 9.5 mm and agitation of a 100g waste sample and solid waste materials containing unacceptable levels in 2 liters of specified extraction fluid for 18 hours on a of ieadhable lead. It is applicable to the managemen! of rotating agitator at a spee~ of about 30 revolutions per le.ad-toxic hazardous solid wastes under D008 waste minute. The lead conceritration is determined in the code assigned bY the United States Environmental Pro- 15 extraction fluid after filtration under pressure, and exte~tion Agency (USEPA). pressed in units of milligrams per liter (mg/1). Any. solid waste that contains leachable TCLP lead BACKGROUND OF THE INVENTION levels, in excess of 5 milligrams per liter is considered Lead as a contamifiant is often found in the soils characteristically toxic and hence hazardous. Such hazaround lead smelters, battery breaking/recycling facili. 20 ardous waste must be treated with a~ least one of the ties, incinerator ash facilities and foundries including Best Demonstrated Available Technologies (BDAT) metal and leaded gasoline manufacturing plants. Con- and/or, with an alternative technology to decharactertamination occurs when lead-containing chemicals are ize the Waste .for lead toxicity. In other words, treatused in the plants, an.d waste containing the lead is alment of the lead-bearing waste with a BDAT for delowed to spill over or drain into the soil. Many.aban- 25 creasing TCLP lead to a level below 5 rag/1 is required cloned hazardous waste sites are heavily contaminated " before land disposal is permitted. Land disposal methwith lead, threatening human health, the food chain, the ods include waste staging on a land surface, placing ecosystem and the environment. Federal legislation, waste into a landfill, using surface impoundment techsuch as the National Contingency Plan (NCP), the 30 niques, waste piling, disposing of waste in injection Superfund Act (CERCLA) and the S~perfund Amend-." v, ells, or land treatment facilities (tand farming), or imments Reauthorization.Act (SARA) specify the remedi~ pounding the waste in salt domes, salt bed formations, ation of Sites containing lead-toxic soils and solid underground mines or caves, and bunkering the waste wastes. in concrete vaults. Land disposal restrictions ban The Resource" Conservation and Recovery Act of 35 treated wastes with TCLP lead levels greater than 5 mg/l in the leachate. Such characteristic lead toxic 1976, commonly known as the RCRA, provided for federal classification of hazardous waste. The statutory wastes must be treated with a cost effective and practilangUage defines "hazardous waste" as solid waste or cal technology that is commercially available and that combinations of solid waste which pose a "substantial provides substantial treatment, and that beneficially present or potential hazard...when improperly treated, 40 results in a decrease in risk to human health and the stored, transported, or disposed of, or otherwise misenvironment: managed." Any solid waste that exhibits one of the Prior to the present invention for treatment of conhazard characteristics defined in subpart C of Part 261, tamifiated soils and D008 solid wastes, there existed no Volume 40, Code of Federal Regulations is, by defini- technology that cou]d be applied (i) cost effectively on tion, a hazardous waste. 45 a commercial scale to treat lead-toxic soils and solid A solid waste is considered to be a hazardous waste if wastes, (ii) to decrease the waste volume and at the same time work under substantially dry conditions with it is listed, or it exhibits characteristics of either ignitano generation of wastewater or other byproducts, (iii) bility, corrosivity, rea6tivity, or toxicity as determined to comply with th~ latest and final land ban regulations by the Toxicity Characteristic Leaching Procedure (TCLP) (USEPA Method 1311). Historically, toxicity 50 (55 Fed. Reg. 22693-94 (1990)), (iv) to cure the wastes characteristic regulations had been;based on the Extrac- in few hours for rapid sampling and final internment evaluation and (v) to a wide variety of lead-toxic solid ¯ lion Procedure (EP) Toxicity Tegt (USEPA Method wastes, soils and sludges with a tremendous flexibility of 1310), which specified laboratory steps to be followed scale and mobility. in analyzing samples. The test was aimed at identifying Various conventional methods have been tried to the tendency of wastes to generate a leachate with con- 55 eentratio.ns of contaminants greater than the values remove leachable, mobile lead from soils and solid waste materials. Those methods include washing, leachlisted in Appendix II of the Code of Federal Reg6laing and extracting the lead. According to conventional tions, Part 261.24, page 406, revised July 1, 1988. If practice, contaminated soil or solid waste material is concentrations of leachable, mobile lead were found to be greater than 5 milligrams per liter, the material was 60 excavated from the ground for processing and/or washconsidered ~haracteristically toxic for lead and hence ing..During washing, the contaminated material is imhazardous with respect to lead content. Such charactermersed or supersaturated in water or other specified solutions while it is being agitated. Removal of lead istically toxic wastes required treatment to comply ~vith from Contaminated soils and solid wastes by leaching, the USEPA regulations defining the t.reatment standards for lead .and other parameters of concern. This 65 extraction and/or washing procedures is extremely expensive and cost-prohibitive because this method EP Toxicity Test.is now obsolete, and has been regenerates vast quantities of lead-toxic wastewaler placed by the TCLP for 39 different parameters includwhich requires further trealment and disposal. ing lead.

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As understood by the inventors, none of the earlier slum), Stanfortfi cited the work of Inglis (U.S..Pat. No, processes reduced the TCLP lead content to below 5 4,652,381) in which crystalline and non-reactive forms mg/l of lead in the extract from lead contaminated, soil of calcium carbonate (such as limestone) were mixed or solid waste material. with a highly acidic waste\vater (pH 2) to precipitate Wet methods for removing lead from contaminated lead, copper and zinc out with formation of a sludge 5 soil or solid waste involve the use of water in the forma- that might contain significant amounts of leachable tion of slurries, which require cumbersome equipmenl metals. This solid waste sludge requires further treatfor the separation of l.ead from the waste material. The ment in order to render it non-hazardous prior to its separated solids are usually wet, so that the end product¯ disposal. As recognized in stanforth, however, limefails the Paint Filter Test (USEPA Method 9095 under stone (6alcium carbonate) is relatively inefficient at 10 SW-846), Further processing of these wet materials is removing heavy metals such as lead and cadmium from therefore required before disposal as a stabilized mate- hazardous solid or sludge waste because of the slow rial: The additional steps required in the treaiment by release of carbonates to react with heavy metals. Furconventional wet processing of contaminated soil and thermore, it is common knowledge that carbonates solid waste are prohibitively expensive. 15 decompose under acid conditions and liberate carbon Otherconventional techniques involve the chemical dioxide as well as metals that may endanger the envi-fixation of lead in contaminated soils" and'solid waste. ronment in the presence of acid rain or landfill leachate. One well-known technique according to the Interna- Bonee U.S. Pat. No. 4,701,219, discloses the treattional Technical Ir~formation Institute involves the ex- ment of spent sorbent wastes (containing leachable vatraction of lead using nitric acid and/or aqua regia, and nadium, nickel, and sodium) with alkaline earth metal 20 a subsequent purging of the resultant lead niti'ate solu- compounds, including calcium sulfate. According to tion with hydrogen sulfide gas to precipitate the lead that patent, powdered lime (calcium hydroxide or calnitrate as lead sulfide, The use of noxious hydrogen cium oxide) and calcium fluoride were most effective in sulfide gas, however, necessitates specific healih and decreasing the leachable vanadium and nickel. safety measures that increase environmental remedia25 Douglas et al. U.S. Pat. No. 4,671,882, discloses the tion costs. generation of non-hazardous sludge from wastewater Fatk et al. U.S. Pat. No. 4,687,373, describes a com- . containing a mixture of metals by first adding phosposition which encapsulates contaminants such as lead phoric acid to lower the pH of the wastewater less than in soils, sludges, sediment and ash. A cementitious ma- 5.0. Thereafter, the acidified wastewater was treated trix in the form of metal metasilicates is formed to en- with a coagulant, ferric chloride, and the pH was raised 30 capsulate the con.taminants. The metal metasilicates, to a range of 7 to 8.5 with calcium hydroxide. An anihowever, detrimentally increase the volume and weight onic polymer (DREW FLOC 270) was employed as a of the treated soil or solid waste material. flocculent to aid dewatering of the sludge. The resulting Hemwa]l U S. Pat. No, 3,201,268, describes a method sludge contained heavy metals in non-leachable form by for stabilizing cla.y soils by mixing phosphoric acid, or 35 EP Toxicity Test criteria. The method developed by a combination of phosphoric and sulfuric acids, with the Doug!as et al. for industrial wastewater treatment cresoil, This mixture is further combined with a waler-sol- ates sludge that is characteristically non-hazardous by ub]e lead salt. The resulting composition may be com- EP toxicity criteria for zinc, lead, chromium, nickel, pacted and q.ured to produce a stabilized mass, strength copper and cadmium, but which may not pass the Paint as compared with untreated soil This method is suitable Filter Test and the TCLP criteria. There is no disclo40 for the stabilization of argillaceous soils and clays con- sure of TCLP testing conducted on this sludge or taining aggregates. ' wastewater. The method disclosed by Douglas et al. Webster et al. U.S. Pat. No. 4,028,130, describes a does, however, generate a supernatant wastewater method for disposing of municipal sewage plant waste stream containing 1 ppm lead as compared to a standard materials, particularly digestive sewage sludge. The limit of 0.05 ppm lead for drinking water under the Safe 45 sludge is treated with cementitious reactants, including Drinking Water Act (SDWA), therefore requiring furcalcium sulfate, to form a hardened product for subse- ther treatment of the supernatant during dewatering quent disposal. The sewage sludge contains heavy met- operations for removal of residual metals. The method als, such as lead, which may be involved in the cementi- disclosed in Douglas et al. does. not appear to be transtious reaction. 50 ferable to lead contaminated soils or solid wastes at any Gouvenot U.S. Pat. No. 4,615,643, describes a scale. method of sealing a mass of stored waste containing The conventional processes as described above typiheavy metal cations in soil. A grout is added to the soil cally do not reduce levels of leachable lead below the which comprises cement, clay, silicate, sodium carbon- maximum concentration of contaminant allowed under ate and an al.kali-metal pyrophosphate or tartrate. The current land ban regulations as per the TCLP Test. 55 lead cation forms a .water-insoluble compound upon Moreover, some of the conventional methods involve reaction with the sodium carbonate and pyrophosphate. wet processing, which is burdensome, cost prohibitive, The process requires a long curing time and has limitei:l and requires a considerable amount of equipment to commercial application. separate the lead from the contaminated soil or solid Stanfonh U.S. Pat. No. 4,889,640, discloses a method waste material in addition to treatment steps. 60 of fixation using reactive calcium carbonate, reactive A.n innovative and cost-efficient technology is theremagnesium carbonate, and reactive calcium magnesium fore n~eded that does not generate wastewater or supercarbonate for reaction with lead and cadmium in haz- natant and that quickly treats the lead-toxic soils and ardous solid wastes (pH 6 to .9) from foundries and D008 solid wastes under relatively dry conditions while metal operations. Stanforth's technique reduces EP fixing the leachable lead to levels below 5 mg/l. by 65 Toxicity Test lead and cadmium in hazardous wastes TCLP Test criteria as required under EPA regulations. when treated with a water-softening lime sludge (a Solidification methods based on cementation technolsource for reactive carbonates of calcium and magne-. ogy require at least 28 days of curing time. increase the

4

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5,193,936
waste volume, and may raise the pH to a range from BRIEF DESCRIPTION OF THE DRAWINGS 12.5 to 13.5. Hardened concrete material is not conducive to retreatment in the event treatment fails TCLP FIG. 1 is a block diagram of one embodiment of the confirmatory testing. Solidification methods utilizing treatment technology of the present invention. lime kiln dust, calcium carbonate and/or powdered lime DETAILED DESCRIPTION OF A PREFERRED for lead fixation are temporary solutions for lead ti'eatEMBODIMENT merit. Furthermore, those methods increase the waste The treatment technology according to the present volume and mass, and therefore, dilute the lead in the final waste matrix. invention consists of a two-step process for treating The use of phosphoric acid alone for fixing lead in l0 contaminated soils and/or solid waste materials with solid waste and soils fails to pass the TCLP lead criteria chemical treating agents that convert leachable lead to in many cases for lead contaminated soils. Addition of synthetic (man-made) substantially insoluble lead mingypsum powder to phosphoric acid treated soils, howeral crystals. As used here, "substantially insoluble" ever, further lowers the TCLP lead levels below the means the leachable lead content in the treated waste regulatory threshold as illustrated in. the examples 15 sample is less than 5.0 mg/l in the extract by the TCLP herein. Stabilization of lead in D008 soils and solid Test. waste is crucial, and a BDAT is therefore urgently The first step of this novel process comprises the needed that is (a) relatively simple and feasible for treatreaction of leachable lead in contaminated soils or solid ing hazardous solid wastes; (b) cbmmercially practicawaste materials with a gypsum powder, calcium sulfate ble, (c).economic~dly applicableand transferable to 20 dihydrate (CaSO4. 2H20). Calcium sulfate dihydrate different lead contaminated sites, (d) rapid, and (e) free powder reacts with leachable and mobile lead species in Of side streams or byproduct wastes. The technology wastes to form hard sulfates, which are relatively insoldisclosed herein generates an end product that is easily uble in water. In this invefition, the powder form of dry handled and thak passes the Paint Filter Test used. for calcium sulfate dihydrate, or gypsum, is preferred for solid waste. 25 blending with lead contaminated materials because it provides a uniform cover or dry coating over the surSUMMARY OF THE INVENTION faces of the waste particles and aggregates under low The presenl invention relates to a chemical treatment moisture conditions. The greatest benefit and fastest technology.for immobilizing leachable lead in contami- reaction is achieved under condition wherein 95% of nated soils and solid waste materials. According to the 30 the powder is passable through a 100 mesh sieve, and present invention, a process for treating lead-toxic solid the remaining 5% is passable throug.h a 20.mesh sieve. wastes in order to stabilize the leachable lead is disThe amount ofgypsum powder employed is typically closed, comprising the steps of:. (i) mixing the solid from 0-30 percent of the weight of solid waste material waste with a sulfate compound, such as calcium sulfate being treated. The actual amount employed will vary dihydrate (gypsum powder) or sulfuric acid, having at 35 with the degree and type of lead contamination in the least one sulfate ion for contacting waste particles and waste material or soil, and with the initial composition reacting with said leachable lead to produce a substanas well as the condition of the waste material, among tially insoluble lead composition, such as ang]esite andother factors. /or calcium-substituted anglesite; and, (ii) mixing said Alternatively, sulfuric acid, or alum in liquid or powsolid wasle and sulfate compound with a phosphate 40 der form can also be used as sources of sulfate ion in reagent, such as pl~osphoric acid, having at least one certain solid wastes that contain sufficient calcium prior phosphate ion for reacting with said leachable lead to to treatment. produce a substantially insoluble lead composition, The In the first step of the instant process, a thorough and treated material from this pro~ess is substantially solid ¯ uniform mixing of gypsum powder with the solid waste in form and passes the Paint Filter Test while satisfying 45 is accomplished by mixing shredded and screen waste the regulatory standard for TCLP lead. In all instances, particles with small gypsum particles in, for example, a application of this process has been found very reliable grizzly or other mixing device. The calcium ions from in meeting the treatment objectives and in consistently the gypsum powder displace lead from soil complexes decreasing waste volume. and organic micelles present in the contaminated soil It is an object of the present invention to provide a 50 and solid waste material. The following equations (1) technology for treatment of lead-containing solid Waste and (2) describe the reaction of leachable lead with and soil that produces an acceptably low level of leachgypsum. able lead in the final product to comply with the statutory requirements of TCLP and to pass the Paint Filter Test. Another object of the invention is to provide such a Pb-Micelle + CaSO4,2H20 @ process while producing no wastewater or secondary waste streams during said process. PbSO4 + Ca-Micelle + 2H/O Anglesite Still another object of the invention is to provide such a process which also causes the solid waste material to undergo a volume reduction as a result of treatment. Pb(HCO3)2 + CaSO,~.2H20 ~ (2) Yet another object of the invention is to cause fixation of the leachable lead in the solid waste that is perPbSO4 + CaCO3 + 3H-~O + CO2 Anglesite manent under both ordinary and extreme environmen65 tal conditions. These and other objects of the invention Will be apThe reaction of lead with gypsum forms a "hard sulfate" which crystallizes into mineral species of the parent from the detailed description of the invention set barite familywanglesites and calcium-substituted anforth below.

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glesites--which are insoluble in water. The solubility. droxyl group, (OH-), and release of water molecules. product of lead sulfate is 1.8× 10-8, indicating that As the water evaporates and carbon dioxide molecules anglesite crystals would continue to develop over the are lost to the atmosphere, the treated waste mass and geologic periods, volume are decreased significantly. In the second step of the process, the solid waste 5 The solid sulfate powder and the phosphate-supply. material as amended with gypsum powder is treated ing reagent are added to contaminated soil and solid with a phosphate-supplying reagent, such as (for examwaste material having a typical moisture content rangple), phosphoric acid. Upon contact with the soil or ing from about 10 percent to about 40 percent by solid waste, the phosphate-supplying reagent reacts. weight. At a moisture level within the foregoing range, chemically to immobilize the remaining leachable lead. the curing time of the treated materials is approximately 10 The phosphate.supplying reagent includes phosphate 4 hours, which provides adequate time for chemical ion sources having one or more reactive phosphate ions, reactions to occur and immobilize the leachable lead such as phosphoric acid, trisodium phosphate, a potasspecies. Crystals of various lead mineral species begin to sium phosphate and monobasic or dibasic calcium phos. form immediately, but will continue over long time phates. 15 periods with an excess of treatment chemicals present. The quantity of phosphate-supplying reagent emThis contributes to "self-healing," as noted during treatployed will vary with the characteristics of the solid ability studies as well as full scale ti'eatmenl operations. waste being treated, including particularly such factors foregoing immobilization as leachable lead content, total lead, and buffering ca- of Under the lead occursconditions, thedry environment leachable in a relatively pacity, among other factors. It has been determined that 20 because no wet byproducts, slurries or wastewater are in most instances a quantity of phosphoric acid up to 30 p~rcen~ of the weight bf the waste material is sufficient. produced by the process of the present invention, Operation of the .process under relatively dry conditions The concentration of phosphoric acid in solution will typically range from about 2-75 percent by weighl. The beneficially allows cost-efficient handling of the contaminated soils Paint Filter Test for solid wastes resolution and treatment process are maintained above 30* 25 compliance withand the waste materials. This allows F. to permit the handling of the phosphoric acid as a liquid reagent. Below 30* F., the phosphoric acid tends quired by USEPA and RCRA approved solid waste to gel while water freezes to form ice, thus creating landfill facilities, Effective mechanical mixing, as by a pug mill or other such mixing device, eliminates the material handling problems. Free lead, along with calcium ions found in the solid 30 need for diffusion in the nonaqueous solid waste matrix. The water resistant and insoluble lead minerals synwaste (including those imparted through the first step of the process), reacts with thg phosphate to form insolu.thesized in soils and solid wastes according to this process are stable, and would behave like naturally occurble superhard rock phosphates or calcium substituted ring rock phosphates and hard sulfates. A list of these hydroxy lead apatites as shown in eqhation (3a and b): 35 synthetic lead mineral species and complexes is presented in Table I below, in order of the relative abun(3n) 4PbCO3 + CaCO3 + 3H3PO4 ~ dance found during characterization of treated soil by x-ray florescence spectrometry, polarized light microsPb4Ca(OH)(PO4).~ + 5CO2 ÷'4H20 copy (PLM) and scanning electron microscopy (SEM),
Hydroxy Lead Apatiles

40
(3b)

TABLE I
Synthetic Mineral Species of Lead De~ected in a Treated'Sample (Listed in Decreasing Order of Abundance) 31-41% Calcium Substituted H.vdrcrxy Lead Apatiles. Cao,5- I,sPb3,5-4,s(OH~( PO4)3 28-29% Mixed Calcium Lead Phosphale Sulfates, Cao,05-0.2 Pb0.8-0,95( PO4)o, 15-0.5( SO4)0,25-0.75 21-22% Mixed Calcium Anglesites, Ca0.05-0.3Pbo.7-0.95SO4 Anglesites, PbSO4 3-6% 2-7% Lead HYdroxy/Chlor Apatite, Pbs(PO4)3(OH)o.5CI0.5 Pyromorphite, Pb3(PO4)2 1-3% 1-2% Organo.Lead Phosphate Sulfate, Humus-o-Pb3(PO~,)(SO4)

4PbCO3 + CaSO4.2H20 + 3H3PO4 @

Pb,~Ca(OH)(PO4)3 + H2SO.~ + 4CO2 + 5H20 Hydroxy Lead Apatites

45

The phosphate ions are added to the conthminated soils in solution form; for example, phosphoric acid may be added to water in amounts ranging from about 250 percent to about 75 percent by weight, Phosphoric acid decomposes carbonates and bicarbonates in wastes leading to the synthesis of apatites and evolution of carbon dioxide gas. Destruction of carbonates and bicarbonates Some of the chemical reactions that occur during the contributes to.desirable volume reductions. 55 curing stage, and lead to the development of mixed ¯ Although water molecules are generated during the minerals containing both sulfates and phosphates, are carbonate and bicarbonate decomposition process, it is illustrated in equations (4) and (5). preferred to have soil moisture at about 10 per cent to about 40 per cent by weight of the soil in order to aecel(4) : ei'ate the fixation of the leachable lead with the phos- 60 18PbCO3 + 5CaSO4.2H20 + phate ions. At this moisture range, material handling is Cure Time = 4 hrs under Ambient 12H3PO4 Temperature (>30' F,) & Pressue ~'also easy and efficient. It is apparent from Equations (2), (3a) and (3b) that gypsum and phosphoric acid decom20Cao.lPbo.9(PO4}0.5(SO4)0.25 + Ca3(PO4)2 + 18CO2 + 28H20 pose carbonates and bicarbonates during synthesis of Mixed Calcium Lead new stable minerals of the barite, apatite, and pyromor- 65 Phosphate Sulfate phite families in soils (as shown in Table I). Decomposition of carbonates and bicarbonates is usually associated 6Pb[Humus] + 2CaSO4,2H20 + (5) with the evolution of carbon dioxide, formation of by-

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9
-continued 3H3PO,~ Cure Time = (>30' under Amblent ~) Temperature 4 hrs F.) & Pressure

5,193,936

10

conveying means to an area where an effective amount of phosphoric acid solution 80 of specified strengths in water 90 is added or sprayed just prior to thorough mixing in a pug mill 100 (or other mixing means). The Ca(9H )[Humus]-Pba(PO4)SO4 + 5 temperature of the phosphoric solution is preferably Organo-Lead Phosphate maintained above 30* F. to prevent it from gelling. The Sulfate treated soil and wastes are subject to curing 110 and 2H20 + Ca0.3Pb0.TSO4 + Cao.TPb2.3(POa)2 drying 120 on a curing/drying pad, or may less preferaAngleshe Pyromorphite I0 bly be-cured and dried using thermal or mechanical (Ca substituted) techniques, The. end product of the process passes the Paint Filter Test. During the curing time of about four The process of the present invention beneficially hours, various "super-hard phosphate" mineral species, decreases the volume of the waste materials through: (i) the evolution of carbon dioxide during the chemical such as calcium-substituted hydroxy lead-apatites and decomposition of carbonates and bicarbonates, upon 15 mixed calcium-lead phosphate-sulfate mineral species, are frrmed in treated waste media 130. Crystals of these reaciiori with the acidic components in gypsum and phosphoric acid, and (ii) hardening and chemical com- mineral species (in early stages of development) have paction as a result of the synthesis of new minerals been identified in the treated soil materials and solid which result, in changes in interstitial spaces and interwastes by geo-chemical and microscopy techniques like lattice structures. Applications of the process on a lead 20 PLM and SEM. ¯ contaminated soil was associated with pore space deThe proportions of waste materials and reagents,used crease from 38,8% to 34.3% by volume. A decrease in in the process may be varied within relatively wide pore space was associated with increased compaction of limits. For example, the amount of gypsum powder the treated soils and a decrease in overall waste volume should be sufficient to produce lead sulfate in contamiranging from 21,4% to 23.0%. For different waste 25 nated soil or solid waste material. In addition, the types, the volume decrease varies with the amount of amount of phosphate.supplying reagent is prescribed in trea!ment chemicals used in the process. In another lead an amount sufficient to produce mineral species such as toxic solid waste, application of this process resulted in hydroxy-lead apatile in contaminated soil or solid waste a volume decrease of the order of 36.4% while decreasing the leachable lead to levels below the regulatory 30 material ddi'ing relatively short curing time of 4 hours, usually ranging from about 3 to about 5 hours. Further threshold. This reduction in volume of the contaminated soil ¯ drying of the treated material may take 24 to 96 hours, but has not been required in any application to date. and the solid waste material makes the process of the Table II documents the optimum curing time of 4 hours present invention particularly beneficial for off-site disposal in a secured landfill by cutting down the costs 35 for the process. In all instances, the leachable lead as of transportation and storage space. The process can be measured by the EP Toxicity Test Procedure was accomplished at a cost-efficient engineering scale on- found below 0.6 mg/l and the differences between annsite or off-site for ex-situ treatment of lead-toxic solid lyrical values below this level are statistically insignifiwastes. This innovative treatment technology also ofcant. fers a great potential for in-situ application to immobil- 40. TABLE II ize lead most economically without generation of any Documentation of Optimum Curing Time wastewater or byproducts. Using EP Toxicity Test criteria for lead fixation FIG. 1 illustrates schematically the process of the EP Toxic EP Toxic Pb concemration present invention. The lead-contaminated uncontrolled Pb in rag/1 found in processed h~zardous waste site 10 with lead.toxic wastes is subject 45 Waste (Untrealed ~ample at a Curin~ Time of 'to excavation and segregation 20 of waste piles based on Matrix Sample) 4 Hrs, 48 Hrs, 96 Hrs. their total lead and TCLP lead contents into (a) heavily Category mg/t mg/1 mg/] mgi] contaminated pile 30A, (b) moderately contaminated Pb Toxic 495 0.4 0,4 0.6 waste pile 30B and (c) least contaminated waste pile Soil A" 30C. The .staged soil and solid waste material in piles 50 46 0.3 0.2 0.2 Pb Toxic 30A, 30B and 30C is subjected to grinding, shredding, Soil B mixing 40 and screening 50 through an appropriately Pb Toxic' 520 0.3 0.5 0.5 Soil C sized mesh sieve. The screening yields particles that are usually less than 5 inches in diameter for mixing with gypsum powder 60 in a grizzly that allows a uniform 55 The amount of the gypsum powder and the phoscoating of gypsum over the soil particles and waste phoric acid employed will be dependent on the amount aggregates during the grinding, shredding and/or mixof contaminant present in the soil, initial characteristics 'ing step. Alternatively,. as shown by the dashed line, of the solid waste material, whether the material is ingypsum po.wder 10 may be added continuously to the screeni~d solid waste material in prescribed amounts as 60. ~itu or is excavated and brought to an off-site facility for treatment; the same is true for other sulfate compounds determined during treatability trials. Most of the leachand phosphate reagents. The following Example I deable lead binds chemically with.gypsum at molecular scribes various ratios of the chemical reagen.ts for applilevel to form lead sulfate, which crystallizes into a synthetic nucleus of mixed calcium anglesite and pure an- cation to the excavated lead-contaminated solid wastes glesite minerals identified in the t~'eated material by65 in order to render ihe leachable lead substantially insoluble; i.e., to reduce the leachable lead to levels below chemical microscopy techniques. 5.0 mg/l by EP Toxicity Test lead and TCLP Test The gypsum-coated waste particles and aggregates are then transported on a belt conveyor 70 or other criteria no in force under current land-ban regulations.

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11

5,193,936

be applied to a wide variety of lead contaminated EXAMPLE I wastes as exhibited in Example II. Nearly twenty (20) different .chemicals and products A three-step process, as set forth in Table I, was not from various vendors and supply houses were screened perceived to be as economically viable as a two-step for chemical fixation of leachable lead in hazardous 5 treatment process, despite its ability to reduce lead levsolid waste samples. Only six (6) of these treatment els insatisfaction of the TCLP Test criteria. A process chemicals were found effective in decreasingthe leachemploys the treatment able lead as measured by: (I) the EP.Toxicity Test and that with a sulfate beneficial combination ofphosphate compound and then with a (2) the TCLP Test. Table Ili presents a summary of first reagent in accord with the present invention, in combileachable lead found in untreated and treated waste .samples allowed t9 cure for a minimum of 4 hours after10 nation with one or more additional treatment steps, may treatment with at lease one of the effective chemicals. nevertheless be within the scope of the invention. In order to illustrate the relative proportions of two Treatment chemicals found relatively ineffective for lead fixation included a variety of proprietary products chemicals, e.g., gypsum and phosphoric acid, needed from American Colloid Company and Oil Dri, different for treatment of lead-toxic wastes, three soil samples 15 sesquioxides like alumina and silica, calcium silicate, from a lead contaminated test site were processed using sodium silicate, Portland cement, lime, and alum from the present invention, in which gypsum powder was different vendors. Results for these ineffective chemiused in the first step, and phosphoric acid solution in cals are not shown in.Table IIl, water at concentrations of about 7, 15 and 22 percent by TABLE lII 20 weight in the second step. The soil was measured for lead content in accordance with the EP Toxicity Test Relative effectiveness of various before and after treatment. A level of leachable lead treatment chemicals screened to decharacterize the lead-toxic solid wastes below 5 mg/l was considered non-hazardous according Leachable Lead to thig procedure. During these test runs, the EP Toxicin mg/l 25 ity Test criteria were in force for treated waste material EP The results of these tests are set forth in Table IV: ¯ Toxicity TCLP
Treatment Chemical (Step) Test
221.4

12

Test
704.5

TABLE IV
Effectiveness in Fixation and Stabilization of Leachable Lead in lead toxic soils 30 EP TOX LEAD TEST RESULTS Process Steps Before After Soil Sample Gypsum Phosphoric TrealTreat-~ (Leadqoxic Step I Step II meat ment 35 wasle) (g/kg soil) (g/kg soil) milligrams per liter 20 1. Low lead 10 8 <0.1 contamination 2. Moderate 30 20 61 <0.1 contamination 3. High lead 40 30 3,659 1.7 40 contamination

1.

Untrealed Conlrol

I1.

IlL

¯ IV.

The foregoing results demonstrate that the process of the present invention was effective in all three samples, representing 3 different levels of lead contamination. 'N.D. means non-detectable at ~0.5 me/I. 45 The process is flexible and is usually optimized during Evaluation of a single treatment chemical in one step bench scale treatability studieg for each waste type to reveals that phosphoric acid was most effective in fixaimmobilize the leachable lead and to decharacterize or tion of leachable lead followed by granular super-phostransform the lead-toxic waste into non-toxic solid phate, a fertilizer grade product ayailable in nurseries 50 'waste acceptable to TSD facilities under current land and farm supply houses; However, neither treatment ban regulations. A net reduction of 36.4% in waste effectivdy treati:d leachable lead to the USEPA treatvolume through use of the instant process has been meat standard of 5.0 mg/l by TCLP methodology. observed. Typical volume reductions are set forth in Although both phosphoric acid and granular SuperTable V. phogphate were effective in meeting the now obsolete 55 TABLE V EP Toxicity Test criteria at 5,0 me/l, this test has been replaced by TCLP Test criteria for lead of 5.0 mgil. Change in Solid Waste Volume as a Result of Treatment with the Two-Step Process Single application of the phosphoric acid, granular suSOLID WASTE VOLUME perphosphate or any other chemical was short of meeting the regulatory threshold of 5.0 mg/'l by TCLP Test 60 Final (After Decrease SOLID WASTE Application of lnilial (Before in Waste criteria for lead. MATERIAL Application of Process and Volume In a two-step treatment process, application of gyp(Treatment Scale) Process) Curing) (%) sum during Step I and treatment with phosphoric acid 1~ Lead toxic soil 3850 cu. yd. 2450 cu. yd. 36.4 in Step 11 resulted in decrease of TCLP-Iead consis(full scale) tently and repeatedly b~low the regulatory threshold of 65 2. Lead-toxic 5.0 mg/l. The results of this two-step treatment process Solid Waste ntilizing gypsum in Step 3[ and phosphoric acid in Step (Bench Scale) II are most reliable and hence, the two-step process may Test Run I 106.1 cu. in. 81.51 cu. in. 23.0
N.D.* 1.4

Sinf.le Treatment Chemical (One Step Treatmenl) a. Sulfuric Acid (I) b. Phosphoric Acid (I) c. Superphosphate Granular (I) d. Liquid Phosphate Fertilizer (1) e. Gypsum Powder (I) f. Sodium Phosphate (I) Two Step Trcatm~0t g. Sulfuric (I) & Lime {I1) h. Gypsum Powder (1) & Alum (II) i. Sodium Phosphate (I) & Phosphoric (1I) j. Gypsum 11) & Phosphoric (II) Three Step Treatment k. Gypsum (I), Alum (11) & Sodium Phosphate (III) I. Gypsum (I), Phosphoric (II) & Sodium Phosphate (Ill)

11.7 1.0 2.7 19.4 24.9. 28.7 20.6 3.9 3.1 N.D.* 12.8

39.8 5.9 11.4 64.3 81.8 93.9 68.1 15.3 12.6 1.6 43.3

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13
TABLE V-continued

5,193,936

I4
TABLE VI Typical changes in solid waste characterisli~:~ 'due to process effect~ MEASURED VALUES After SOLID WASTE Before Treatment & Curing CHARACTERISTICS Treatment
I. Lead,toxic SW-A

Change in Solid Waste Volume as a Result of Trealmenl with the Two.Step Process SOLID WASTE VOLUME . Final (After Decrease SOLID WASTE Initial (Before Application of in Waste MATERIAL Application of Process and Volume (Treatment Scale) Process) Curing) (~) Tesl Run I1 22.0 cu. in. 17.3 cu. in. 21.4

force under the land ban regulations of the United States Environmental Protection Agency.

10

Total lead, % 1.442 1,314 The mosi profound effect of the process of the presTCLP-Lead, mg/l ¯ 542.0 2,0 ent invention is at a structural level, where the breakMoisture, % 23,0 33,0 pH, S.U, down of granular aggregates is associated with a loss of 8,1 4.8 II. Lead-toxic SW-B fluffiness and a decrease in pore space and increased 15 Total lead, % 0,847 0.838 compaction due to physical, mechanical and chemical 2,4 TCLP-Lead, mg/l 192.0 forces at different levels. At a molecular level, phosMoisture, % 27 36 phoric acid breaks down the minerals containing carpH, S.U. 8.0 5.3 III. Lead.Toxle SW-C bonates and bicarbonates, including cerussites, in stoiTotal Lead, °k 3.968 3.066 ehiometric proportions, Soon after the addition ofphos- :20 257.6 TCLP-Lead, mgfl 1.0 phoric acid to a solid waste containing cerussites, exten-Moisture, % 10.0 18.1 sive effervescence and frothing becomes evident for pH, S, U, 7,2 4.5 IV. Lead-Toxic SW-D several minutes and sometimes for a few hours. The Total Lead, % 2,862 2.862 phosphoric acid breaks down the acid sensitive carbonTCLP-Lead, rag/1 245.3 0.38 ates and bicarbonates leading to the formation of carbon 25 71.6 84.1 'Moisture, % dioxide, water and highly stable and inso'luble sulfate pH, S.U. 8.1 6.3 and phosphate mineral compounds. Thus, structural V. Lead-Toxic Soll SW-E changes due to interlattice reorganization as well as. Total Lead, % 0,16 0.12 TCLP-Lead, mg/l 7,5 1.87 interstitial rearrangement in waste during processing Molst ui'e, % 12,3 23.0 are associated with an overall decrease in waste vol- 30 pH, .S.U. 7.0 5.4 ume. Depending on the extent of carbon dioxide loss from .the breakdown of carbonates and bicarbonates It is obvious from Table VI that the instant process present in the lead-toxic solid waste, the process may operates over a wide range of moisture and pH condilead to a slight loss of waste mass as well. Water gener35 tions. It is associated with 8 tO 11% rise in moisture ated during the chemical reactions is lost by evaporaContent. The end product of the treatment process may tit,n, which further decreases the mass and volume of contain moisture in a typical range of 18% to 36% on a the treated solid wastes and soils. dry weight basis. The end product passes the Paint The cost of the process of the present invention is Filter Test..for solids and there are no other byproducts moderate to low, depending upon (i) waste characteristics, (ii) treatment system sizing, (iii) site access, (iv) 40 or side streams generated during the process. The treated solid waste is cured in 4 to 5 hours and may be internment of final disposition of treated material and allowed to dry for 2 tO 3 days after treatment for loss of (v) site support requirements: The costs of treatment unwanted moisture prior to final internment and dispoand disposal are presently on the order of $115 per ton sition. This time is sufficient for the TCLP Tests to be of lead-toxic wast.e, as compared to off-site conven- 45 completed as part of the disposal analysis under land tional treatment and disposal costs of over $250 per ton ban regulations enforced by the USEPA. if no treatment in accord with the invention had been It is necessary to establish the quantities of gypsum performed, Moreover, recent land ban regulations and phosphate.reagent on a case-by-case basis, because would prohibit the disposal of all lead-toxic wastes in the consumption of these materials will depend not only .landfills. The foregoing Example makes clear that the 50upon the initial lead level in the waste or soil, bul also process of the present invention provides an efficient upon other waste characteristics such as cation extechnology that is economically attractive and commerchange capacity, total buffering capacity, and the cially viable in meeiing regulatory criteria for landfills. amounts of carbonates and bicarbonates present, among

others. Bench scale treatability studies for each solid EXAMPLE II 55 waste considered will be necessary to determine the The process of the present invention was applied On optimum levels of material that are employed. The bench scale to five different lead-toxic waste materials treatability studies are designed to optimize the amount that were characterized for total lead, TCLP-lead, an'd grade of gypsum powder (or other sulfate commoisture content and pH before and after treatment. A pound) needed during step I, and the amount and concuring time of 5 hours was allowed for. completion of 60 centration of phosphoric acid (or other phosphate comthe treatment process. The results compiled in Table VI Bound) needed in step I1 for cost-effective operation of exhibit the profound effects of the process in decreasing the treatment system. Those skilled in the art are knowlthe TCLP lead in a wide range of lead-toxic soils and edgeable of such bench studies, which are usually carsolid wasles containing total lead as high as 39, 680 ried out as precursors to full scale treatment. mg/kg and TCLP lead as high as 542 mg/]. In each of 65 The present invention has been described with rethe five cases, the instant process immobilizes the leachspect to certain embodiments and conditions, which are able lead to levels below the regulatory threshold of 5 not meant to and should not be construed to limit the mg/l set by the TCLP Test criteria for lead currently in invention. Those skilled in the art will understand that

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variations from the embodiments and conditions de- phosph.ale~sulfate mixed mineral crystals, calcium-subscribed herein may be made without departing from tlie stitti(ed anglesites, anglesites, and pyromorph[tes. invention as claimed in the appended claims. 11, The treatment process of claim 1, wherein the What is claimed is: sulfate composition is employed in an amount of up to I. A treatment process for treating lead-toxic solid 5 about 30 percent of the weight of waste material being wastes to stabilize leachable lead contained therein, said treated, process comprising the steps of: 12. The treatment process of claim 1, wherein the mixing a solid waste containing leachable lead with a phosphate reagent is employed in an amount of up to sulfate compound having at least one sulfate ion for about 30 percent of the weight of waste material being reacting with said leachable lead to produce a first 10 treated. mixture, said first mixture containing a substan13, The treatment process of claim 1, wherein the tially insoluble lead compound or mineral species; solid waste is permitted to cure for 3-5 hours. and 14, A treatment process according to claim 1, mixing said first mixture with a phosphate reagent wherein said solid waste has a moisture content of from having at least one phosphate ion for reacting with 15 about 10 to about 40 percent by weight. leachable lead remaining said first mixture to pro15. A treatment proqess according' to claim I, duce a second mixture, said second mixture con' raining a substantially insoluble lead compound or wherein said step of curing lasts for a period of 3 to 5 hours. mineral species; ' IIi. A treatment process for treating solid wastes to curing said second mixture for a period 20 stabilize leachable lead contained therein, said process such thai the material so treated is substantially solid in form at the end of curing, the material passes the comprising the steps of: containing leachable lead with mixing a solid waste paint filter test, TCLP lead levels are decreased gypsum to produce a first miJcture, said first mixbelow 5.0 mg/l, the volume of said solid waste is ture containing a substantially insoluble lead cornreduced as a rest~lt of treatment and curing, and no 25 pound of mineral species; and secondary waste streams are generated. mixing said first mixture with phosphoric acid for. 2. The treatment process of claim 1, wherein said reacting with leachable lead remaining in said firsl sulfate compound is selected from the group consisting mixture to produce a second mlxtu.re, said second of calcium sulfate, gypsum, sulfuric acid and alum. mixture con.taining a substantially insoluble lead 3. The treatment process of claim 1, wherein said30 compound or mineral species; sulfate compound is supplied in the form of a dry po\vcuring said second mixture for a period der homogeneously mixed with the said solid waste. such that the material so treated is substantially solid 4. The treatment process of claim 2, wherein said in form at the end of curing, the material passes the sulfate composite is supplied in the form of a dry powpaint filter test, TCLP lead levels are decreased der homogeneously mixed with the said solid waste. 35 below 5.0 mgil, the volume of said solid waste is 5. The treatme~at process of claim 1, wherein said reduced as a result of treatment.and, curing, and no sulfate compound is supplied in the form of a liquid secondary waste streams are generated, homogeneously mixed with the said solid waste. 17. The treatment process of claim 16, wherein the 6. The treatment process of claim 2, wherein said sulfate compound is supplied in the form of a liquid 40 gypsum is employed in an amount of up to about 30 percent of the weight of waste material being treated. homogeneously mixed with the said solid waste. 18, The treatment process of claim 16, wherein the 7. The treatment process of claim 1, wherein said phosphoric acid is employed in an amount of up to phosphate reagent is selected from the group consisting of phosphoric acid, mono-, di- and tri-basic phosphates. about 30 percent of the weight of waste material being 8. The treatment process of claim 1, wherein said45 treated. phosphate reagent is supplied as an aqueous solution. 19. A treatment process according to claim 16, 9. The treatment process of claim 1, wherein.said wherein said solid waste has a moisture content of from phosphate reagent is supplied in the form of a solid from about 10 to about 40 percent by weight. the group consisting of mono-, di- and tribasic phos20. A treatment process according to claim 16, phates. 50 wherein s~ild step of curing lasts for a period of 3 to 5 10. The treatment Process of claim 1, wherein the hours. leachable lead is converted to superhard phosphates and
55

15

16

65

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REEXAMINATION CERTIFICATE (2819th) United States Patent Ill~ B1 ~5,193,936
Pal et al.
[541 FIXATION AND STABILIZATION OF LEAD
IN CONTAMINATED SOIL AND SOLID WASTE Yost, Crete, both of Ill.

[45] Certificate Issued Mar. 19, 1996
[58] Field of Search ..................................... 4051128, 129, 405/263, 266; 106/900; 210/751, 912, 747; 588/256

[751 Inventors: Dhiraj Pal, Chicago Heights; Karl
[731 Assignee: MAECORP Incorporated, Chicago, Ill. Reexamination Request: No. 90/003,305, Jan. 13, 1994 Reexamination Certificate for: Patent No.: 5,193,936 Issued: Mar. 16, 1993 Appl. No.: 721,935 Filed: Jul. 23, 1991 Related U,S~ Application Data [63] Continuation-in-part of Ser. No. 494,774, Mar. 16, 1990, abandoned. Int. CI.6 ................................. B09B 3100; E02D 3!00

156]

References Cited U,S. PATENT DOCUMENTS

4,373,356 411988 O'Hara et al ........................... 4,804,147 2/1989 Hooper ...................................... 5,040,920 811991 Forrester ................................. 5,162,600 11/1992 Cody eta] .............................. Primary Examiner--David H. Corbin ABSTRACT [57]

4231659 241/24 405/128 5881236

[51] [52] U.S. CI ........................... 4051128; 210/751; 405/263; 588/256

A two-step treatment process is disclosed ['or application of lead-toxic wastes to fixate and stabilize leachable lead contained therein. The process employs the use of a sulfate compound, such as gypsum, in a first step; and a phosphate reagent, such as phosphoric acid, in a second step. After thorough mixing and curing, a substantially solid end product is formed in which the lead is chemically fixed and remains in stabilized form for indefinite geologic periods. The process reduces Toxicity Characteristic Lqaching Procedure lead levels below the regulatory threshold of 5 mg/] as required by the U.S. Environmehtal Protection Agency. The waste also beneficially undergoes volume reduction in a short curing time, and is applicable in a variety of situations.

STEP ]:[ LIQUID REAGENT (PHOSPHORIC ACID)

/-80
,

' }o
GRADING

.7O

,o%,
I

I

I (9O

WATER SUPPLY

I

[CONVEYOR

(HOMOGENEOUS MIXING)

!

I

l

liOn[ CURING

1
OR SOLID WASTE ¯ ,,CRITERIA) TREATED,, SOIL (NON-TOXIC BYTCL P1Li30

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B1 5,193,936 1 2 AS A RESULT OF REEXAMINATION, IT HAS BEEN REEXAMINATION CERTIFICATE DETERMINED THAT: ISSUED UNDER 35 U.S.C~ 307
¯ The patentability of claims 5 and 6 is confirmed. Claims 1-4, 7-20 are cancelled. THE PATENT IS HEREBY AMENDED AS INDICATED BELOW.