MXPA99007128A - Sequential biological/chemical/biological treatment of organic waste - Google Patents

Abstract

A process for remediation of contaminated solid materials comprising polynuclear aromatic hydrocarbon contaminated solid materials, polychlorinated hydrocarbon contaminated materials, and mixtures thereof by sequential biological/chemical/biological treatment in which the contaminated solid materials are biodigested under suitable conditions by a first aerobic or anaerobic digestion, producing a first biodigestion product. The first biodigestion product is then contacted for chemical treatment with hydrogen peroxide in the presence of ferrous ion in amounts and under conditions suitable for chemical oxidation, forming a mixture and oxidizing the first biodigestion product, producing biodegradable hydrocarbon product materials having enhanced biodegradability. The product materials are then biodigested under suitable conditions by a second aerobic or anaerobic digestion.

Description

"BIOLOGICAL / CHEMICAL / BIOLOGICAL TREATMENT IN SEQUENCE OF ORGANIC WASTE" BACKGROUND OF THE INVENTION This invention relates to sequential biological / chemical / biological treatment that provides improved remedy of unwanted organic solid components in materials such as soils, sediments, slimes and slurries containing these solid organocontaminants, particularly polynuclear aromatic hydrocarbons (PAH's) and polychlorinated hydrocarbons (PCBs). The process generally involves the biological treatment of contaminated solid materials under aerobic conditions by chemical oxidation or partial oxidation with hydrogen peroxide in the presence of ferrous ion, such as the Fenton Reagent (H2? 2 / Fe ++), under specified conditions followed by digestion aerobic microbial DESCRIPTION OF THE PREVIOUS TECHNIQUE A number of references of the prior art disclose the treatment of effluents containing organic substances with hydrogen peroxide and iron.

- - US Pat. No. 4,321,143 discloses how to reduce the COD content of the effluent by treating it with hydrogen peroxide in the presence of a transition metal compound, for the decomposition of hydrogen peroxide, adjusting the pH of the effluent to approximately 4. to 5, adding from about 55 percent to 63 percent of the calculated amount of H2O2 that is required for the total oxidation of the total COD content, dissolving an iron compound in the effluent so that the molar ratio of H2O2 to iron is from about 20: 1 to 10: 1, maintaining the temperature at about 5o to about 100 ° C, adding a base to adjust the pH to approximately neutral, separating the flocculated material, and subjecting the effluent to biological degradation. The oxidation of certain aromatic chemicals using the Fenton Reagent is already known: US Patent Number 4,604,214 discloses the removal of nitrocresols from dinitrotoluene wastewater streams by adjusting the pH to less than about 4, with an aqueous acid followed by contact with the Fenton Reagent, from approximately 1.1 to 3.0 weight ratio of peroxide to the total nitrocresols and ferrous salt to provide 2.5-5X10 ~ 3M, at 70 ° C up to - - 90 ° C for about half an hour to an hour. U.S. Patent No. 4,804,480 discloses how to destroy polynitrophenols or their salts in an aqueous residue by treating with at least two moles of hydrogen peroxide per mole of nitrophenol in the presence of 0.002 to 0.7 mole of iron salt per mole of polynitrophenol, and at a pH lower than 4 and a temperature higher than 65 ° C; U.S. Patent No. 4,370,241 discloses the treatment of waste water containing phenol or a phenol derivative with hydrogen peroxide in the presence of iron or metallic copper with a specified activator which is a salt of an alkali metal, alkaline earth metal, zinc, Aluminum, nickel, manganese or insoluble silica, the activator is present in an amount of 0.1 percent to 0.2 percent based on hydrogen peroxide, and the treatment is said to be pH independent. US Patent Number 4,724,084 discloses the removal of toxic organic substances and heavy metals from the wastewater discharged from aircraft manufacturing processes using hydrogen peroxide catalyzed with ferrous sulfate at an initial pH of about 5 for the oxidation of phenol followed by flocculation of metals and repeating the oxidation step with hydrogen peroxide catalyzed with ferrous sulfate.

The decontamination of the earth by desorbing and dehalogenation of the polyhalogenated contaminants is disclosed by US Pat. No. 4,447,541 to be carried out by an alkaline constituent of an alkali metal hydroxide and a monohydric or dihydric alcohol., together with a sulfoxide catalyst followed by biological degradation of the most highly biodegradable hydrolyzed organic substances. U.S. Patent No. 4,387,018 discloses the removal of polychlorinated biphenyl from the oil by extracting the biphenyls in the methanol and separation by distillation. The publication "Biodegradation of Old Town Gas Site astes," Vipul J. Srivastava, John J. Kilbane, Robert L. Kelley, Cavit Akin, Thomas D. Hayes and David G. Linz, IGT Symposium on Gas, Oil, and Coal Biotechnology , New Orleans, Louisiana, from December 5 to 7, 1988, generally suggests the treatment of pyrene and thiantrene with hydrogen peroxide and ferrous sulfate to oxidize polynuclear aromatic hydrocarbons to complement biological treatment processes in situ. A recent review of bio-remediation of contaminated organic solid and liquid waste that points out many problems, particularly in the bio-remedy of solids contaminated with aromatic hydrocarbons, more - - particularly polynuclear aromatic hydrocarbon contaminants having from about 4 to about 6 rings, is provided in "Bioremediation of Gas Industry Wastes: Current Status and New Directions," W. Kennedy Gauger and Vipul J. Srivastava, Hazardous Waste and Environmental Management in The Gas Industry Symposium, Chicago, Illinois, June 13, 1990.

COMPENDIUM OF THE INVENTION An object of this invention is to provide a process for the effective degradation of polychlorinated hydrocarbon materials (PCBs) and polynuclear aromatic hydrocarbon materials (PAHs) in contaminated soils that can reduce the level of polychlorinated hydrocarbon materials and polynuclear aromatic hydrocarbon materials. by more than 90 percent. An object of this invention is to provide a process for biological degradation followed by high-grade chemical oxidation of polynuclear aromatic hydrocarbons and / or polychlorinated hydrocarbons using hydrogen peroxide in the presence of ferrous ion, followed by biological degradation to obtain high remedy of polynuclear aromatic hydrocarbon and / or solids contaminated with polychlorinated hydrocarbon.

Another object of this invention is to provide an integrated biological / chemical / biological treatment process for the remedy of solid waste materials contaminated with higher polynucleated aromatic hydrocarbons and / or polychlorinated hydrocarbons where the high concentration of solids can be treated at more or less ambient temperatures . Still another object of this invention is to provide an integrated biological / chemical / biological treatment process for solid waste materials contaminated with polynuclear aromatic hydrocarbon and / or polychlorinated hydrocarbon which is improved by the presence of methanol and / or ethanol, during the chemical treatment with hydrogen peroxide in the presence of a ferrous ion. These and other objects of this invention are aced by a sequential biological / chemical / biological treatment process for remedying contaminated solid materials comprising solid materials contaminated with polynuclear aromatic hydrocarbon and / or polychlorinated hydrocarbon contaminated materials, wherein the materials contaminated solids first biodegrade under appropriate conditions through a first aerobic or anaerobic digestion, producing a first product of biodigestion. The product of this first aerobic or anaerobic digestion is then contacted for chemical treatment with hydrogen peroxide in the presence of ferrous ion, preferably in a liquid solution forming a mixture, or slurry, at a temperature of about 20 ° C. at about 40 ° C, oxidizing the polynuclear aromatic hydrocarbons and / or the polychlorinated hydrocarbons, thereby producing materials of the hydrocarbon product more readily biodegradable. These more easily biodegradable hydrocarbon product materials are then biodegraded by a second aerobic or anaerobic digestion. The process can also be further improved by increased total oxidation of polynuclear aromatic hydrocarbons and / or polychlorinated hydrocarbons to carbon dioxide in the chemical treatment step by the presence of a lower alcohol in the aqueous slurry containing hydrogen peroxide. The process of this invention is extremely flexible providing combinations of biological treatments and various manner of recycling. The biological / chemical / biological treatment process integrated in accordance with this invention can also be carried out in in-situ solids, such as contaminated soil. This process is very effective in degrading PCB congeners. The preferred microorganisms to be used in the biodigestion steps are Alcal ± genes eutrophus and Pseudomonas sp. Surprisingly, we have found that biological treatment steps work best at a pH within the range of about 4.0 to 6.0, preferably at a pH of 5.0. This is particularly surprising in view of the fact that most of the research to date in Alcalissés eutrophus and Pseudomonas sp. has shown that a pH of 7.5 is optimal for maximum degradation of PCB congeners (Bedard et al., "Rapid Assay for Screening and Characterizing Microorganisms for the Ability to Degrade Polychlorinated Biphenyls," Applied and Environmental Microbio- logy, April 1986 pages 761 a 768). A pH within the range of about 4.0 to 6.0 is also beneficial for the chemical treatment step. The operation of the process of this invention under these conditions has led to a greater degradation of 99 percent of the PCBs in the solid material contaminated with PCB. It is already known that the hydroxylation of organic compounds is a necessary step for biological degradation and increases the solubility of polynuclear aromatic hydrocarbons. It is also known that the Fenton Reaction hydroxylates the organic compounds. As a result, it is evident that the chemical treatment of the polynuclear aromatic hydrocarbons and the polychlorinated hydrocarbons according to the present process of this invention increases the biodegradability and bioavailability of the polynuclear aromatic hydrocarbons and the polychlorinated hydrocarbons. By carrying out the step of chemical treatment with an aerobic digestion step in accordance with the process of this invention, we were able to improve the efficiency of the chemical process which in turn further improves the efficiency of the aerobic digestion step which follows the step of chemical treatment The experiments we have carried out demonstrate that the more polar intermediates are also formed in the chemical treatment step to provide improved biodegradability. Furthermore, the chemical treatment according to the process of this invention modifies the texture of the soil where the polynuclear aromatic hydrocarbons and the polychlorinated hydrocarbons are placed as well as the interaction between the absorbed organocontaminant and the earth matrix, causing the organocontaminant to remain more available for desorption and biodegradation. Although surfactant bioagents are known to be effective in lower molecular weight organic compounds, they have not been shown to be effective in higher molecular weight compounds such as hydrocarbons - polynuclear aromatics of 4 to 6 rings. J.G. Mueller, et al., "Isolation and Characterization of a Fluoranthane-Utilizing Strain of Pseudomonas pauczimobilis", Applied Environmental Microbiology, 56: 1079-1086 (1990) and Mueller, J.G. and others, "Action of Fluoranthene-Utilizing Bacterial Community on Polycyclic Aromatic Hydrocarbon Components of Creosote," Applied Environmental Microbiology, 55: 3085-3090 (1989) describe the improved biodegradability of fluoranthene and other polynuclear aromatic hydrocarbons by the addition of 200 parts by Million Tween 80, a known surfactant, that is, it is not a surfactant bioagent. It will also be apparent to those skilled in the art that the non-specific nature of the Fenton reaction requires sufficient hydroperoxide peroxide to degrade all organic substances. In direct contrast to this, we have found that polynuclear aromatic hydrocarbons and polychlorinated hydrocarbons absorbed in the ground matrices are selectively degraded and, as a result, good results are obtained by using less hydrogen peroxide.

BRIEF DESCRIPTION OF THE DRAWINGS - The invention will be more fully understood by describing the preferred embodiments together with the drawings in which: Figure 1 is a diagram showing the relative efficacy of the microorganisms used in the process of this invention for 2-chlorobiphenyl mineralization; Figure 2 is a diagram showing the effect of optical density (culture density) on the effectiveness of the process of this invention; Figure 3 is a diagram showing the efficacy of the biological-chemical treatment in sequence with respect to the mineralization of 2-chlorobiphenyl by the resting cells of Alcal ± genes eutrophus at a pH of 5.0; Figure 4 is a diagram showing the efficacy of the biological-chemical treatment in sequence by the mineralization of 2-chlorobiphenyl by resting cells of alkalis eutrophus of a pH of 7.0; Figure 5 is a diagram showing the efficiency of the biological-chemical treatment in sequence on the 2, 2 ', 4, 4' -tetrachlorobiphenyl mineralization by resting cells of alkalis eutrophus at a pH of 5.0; Figure 6 is a diagram showing the efficiency of the biological-chemical treatment in sequence on the mineralization of 2, 2 ', 4, 4' -tetrachlorobiphenyl by resting cells of Alcal ± genes eutrophus at a pH of 7.0; Figure 7 is a diagram showing the efficacy of the biological-chemical treatment in sequence on the 2-chlorobiphenyl mineralization by resting cells of Pseudomonas sp. at a pH of 5.0; Figure 8 is a diagram showing the efficiency of the biological-chemical treatment in sequence on the 2-chlorobiphenyl mineralization by resting cells of Pseudomonas sp. at a pH of 7.0; Figure 9 is a diagram showing the efficiency of the biological-chemical treatment in sequence on the mineralization of 2, 2 ', 4, 4' -tetrachlorobiphenyl by resting cells of Pseudomonas sp. at a pH of . 0; Figure 10 is a diagram showing the efficiency of the biological-chemical treatment in sequence on the mineralization of 2, 2 ', 4, 4' -tetrachlorobiphenyl by resting cells of Pseudomonas sp. at a pH of 7. 0; Figure 11 is a diagram showing the effect of different incubation times on the degradation of - PCB by biological treatment in accordance with this invention; Figure 12 is a diagram showing the effect of different incubation times on the degradation of PCBs by chemical treatment; Figure 13 is a diagram showing the effect of pH in the treatment with Fenton Reagents of the aqueous slurry of soil in bench scale studies; Figure 14 is a diagram showing the results of PCB degradation using various embodiments of the process of this invention compared to the biological-chemical treatment in sequence. Figure 15 is a diagram showing the results of an actual ground bank scale treatment in accordance with the process of this invention; and Figure 16 is a flow chart of the process for the degradation of polychlorinated hydrocarbons by the biological-chemical-biological treatment process in sequence of this invention.

DESCRIPTION OF THE PREFERRED MODALITIES As used throughout the specification and claims, the term "mineralization" is defined as implying essentially complete degradation of PCBs and PAHs to CO2 • "Degradation" is distinguished from "mineralization" since degradation involves the transformation of PCBs and PAHs in an environmentally benign way, even if not completely necessary in C02. Town gas or manufactured gas plants have contaminated earths with residues of molten ring compounds of organic polynuclear aromatic hydrocarbon, higher ring number compounds, particularly those having from about 4 to about 6 rings, generally being recalcitrant to bio -remedy. This recalcitrance is amplified when the contaminant is associated with a solid material, such as soil, and when the content of the organic waste is high, such as from more than 5,000 to 10,000 parts per million and up to 30,000 to 40,000 parts. per million, as is the case with many contaminated lands of organic polynuclear aromatic hydrocarbon. Removal of the solvent from the organic contaminant has been carried out to provide a liquid bio-remediation system that is known to be more effective than the solid treatment system, but in many cases, the extraction liquids were not compatible with the microorganisms and the uniformity - - of desired degradation, particularly of aromatic compounds of 4 to 6 rings, could not be obtained. When reference is made to polynuclear aromatic hydrocarbon compounds of 4 to 6 rings we mean that compounds such as pyrene, fluoranthene, chrysene, benz (a) anthracene, benzo (a) pyrene, benzo (e) pyrene are included. , benzo (b) fluoranthene, benzo (k) fluoranthene, benzo (g, h, i) perylene, indene (1, 2, 3-cd) pyrene, dibenzo (a, h) anthracene, - and their substituted derivatives. We have found that the chemical oxidation of hydrogen peroxide combined with biodigestion according to the present invention preferably destroys the polynuclear aromatic compounds of 4 to 6 molten rings, as compared to the polynuclear aromatic compounds of 2 to 3 molten rings. The synergism of the integrated chemical / biological treatment process according to the present invention with respect to the polynuclear aromatic hydrocarbon compounds of 4 to 6 molten rings which is further amplified by the simultaneous chemical treatment of the solids contaminated with hydrogen peroxide in presence of a lower alcohol, such as methanol or ethanol. This is especially unexpected because the addition of any organic compound was expected to rapidly cool the oxidation of the aromatic hydrocarbon compounds - - polynuclear by means of hydrogen peroxide, while in this case, the oxidation significantly increases, particularly of the polynuclear aromatic hydrocarbon compounds of 4 to 6 rings. It is known that the above addition of organic materials is detrimental; for example, before mixing with livestock manure, the desired oxidation effect of hydrogen peroxide significantly decreases because active hydroxyl ions are apparently consumed by active organic materials other than polynuclear aromatic hydrocarbon compounds. . Low molecular weight alcohols are believed to increase the aqueous solubility of polynuclear aromatic hydrocarbons, in particular polynuclear aromatic hydrocarbons of 4 to 6 rings, thereby rendering them more susceptible to oxidation by the Fenton reaction. The process for remediating contaminated solid materials comprising solid materials contaminated with polynuclear aromatic hydrocarbon and / or polychlorinated hydrocarbon contaminated materials by sequential biological / chemical / biological treatment, in accordance with one embodiment of this invention, comprises biodigesting the solid materials contaminated under appropriate conditions through a - first aerobic or anaerobic digestion, producing a first product of biodigestion, putting in contact for chemical treatment the first product of biodigestion with hydrogen peroxide in the presence of ferrous ion, in quantities and under appropriate conditions for chemical oxidation at a temperature within the scale from about 20 ° C to 40 ° C, forming a mixture and oxidizing the first biodigester product, producing biodegradable hydrocarbon materials having improved biodegradability. According to a particularly preferred embodiment of the process of this invention, the material produced from the chemical treatment is bio-digested under appropriate conditions by a second aerobic or anaerobic digestion. In accordance with a particularly preferred embodiment of this invention, the microorganisms for biodigesting these contaminated solid materials and the materials produced comprise a microbial culture that is selected from the group consisting of Alcal ± genes eutrophus, NRRL No. 15940, Pseudomonas sp. NRRL No. 18064, Rhodococcus globerulus Pe, ATTCC Strain No. 55255 and mixtures thereof. We carried out experiments using cultures of alkalis eutrophus and Pseudomonas sp. for a prolonged period of time for maintenance of 2-chlorobiphenyl. The results, as shown in the - Figure 1 suggest that both crops are equally effective in 2-chlorobiphenyl mineralization with a total mineralization approach of about 20 percent in incubation through more than 20 days. These experiments were carried out at an optical density for microorganisms of 1.0 and a pH of 7.0. Figure 2 shows the effect of the optical density, i.e. the concentration of the microorganisms, in the process of this invention. The experiments were carried out with Pseudomonas sp. using two different optical densities (O.D.) of 0.2 and 1.0. The results revealed some improvement of 2-chlorobiphenyl mineralization at an optical density of 1.0 compared to 0.2. These results suggest that the variation in optical density affects total mineralization. We have found that the mineralization of the polychlorinated hydrocarbons according to the process of this invention is greatly improved at optical densities greater than 1.0. According to a particularly preferred embodiment of this invention, the optical density of the medium comprising the microorganisms is within the range of about 2.0 to 4.0. Figures 3 to 6 show the effect of pH on mineralization of PCBs in accordance with the process of this invention. Studies were carried out where the PCBs were subjected to biological treatment with -A2ca2igre-nes eut-rop us for 26 days followed by treatment with the Fenton Reagent (4 percent H2O2). Optical densities of 2.0 and 4.0 were evaluated at pH 5.0 and 7.0 for alkalis eutrophus. The results for the mineralization of 2-chlorobiphenyl and 2, 2 ', 4,4'-tetrachlorobiphenyl are shown in Figures 3 to 6. The mineralization in excess of 98 percent was achieved for 2-fluorobiphenyl using Alcal ± genes eutrophus a a pH of 5.0 and an optical density of 4.0. However, even at an optical density of 2.0, 94 percent mineralization was achieved by suggesting that a pH of 5.0, compared to pH within the range of 7.0 to 7.5, as typically used with alkalis eutrophus, is very effective for the biological mineralization of 2-chlorobiphenyl using Alcal ± genes eutrophus. A comparison study carried out at a pH of 7.0 showed that biological mineralization of 82 percent and 71 percent was achieved at optical densities of 4.0 and 2.0, respectively using Alcal ± genes eutrophus. These results clearly demonstrate that a pH of 5.0 which is essentially lower than the pH normally employed with alkalis eutrophus, is more effective for the 2-chlorobiphenyl mineralization than the pH of 7.0. Mineralization of more than 56 percent was achieved with - 2 - biological treatment only in less than 26 days. After the chemical treatment with the Fenton Reagent according to the process of this invention, a 98% total mineralization was achieved within 106 days. The experiments carried out with 2, 2 ', 4,4'-tetrachlorobiphenyl at pH 5.0 and 7.0 and optical densities of 2.10 and 4.0, showed similar results. Mineralization of 74 percent and 82 percent of 2, 2 ', 4, 4' -tetrachlorobiphenyl was achieved at a pH of 5.0 and optical densities of 2.0 and 4.0, respectively. By comparison, mineralization of only 44 percent and 50 percent was achieved at a pH of 7.0 and optical densities of 2.0 to 4.0, respectively. Figures 7 to 10 show the results of the application of the process of this invention to Pseudomonas sp. As can be seen, the mineralization of more than 95 percent of the PCBs was achieved at an optical density of 4.0 and a pH of 5.0. The total pattern with Pseudomonas sp. it was similar to the results obtained with Alcal ± genes eutrophus. Therefore, it is evident from these results that a pH of 5.0 is more appropriate to achieve complete mineralization of 2-chlorobiphenyl using either alkaline genes eutrophus or Pseudomonas sp. followed by chemical treatment in accordance with the process of this - - invention. The operation of the process of this invention at a pH of 5.0 resulted in more than 90 percent PCB mineralization. Accordingly, it is preferred that the process of this invention be carried out at a pH of less than 7.0, preferably within the range of about 4.0 to 6.0. Alcal ± gßnes eutrophus or Pseudomonas sp. they are equally effective in the biological treatment of 2-chlorobiphenyl in accordance with the process of this invention resulting in more than 50 percent mineralization in 26 days. However, when applied to 2, 2'4, 4'-tetrachlorobiphenyl, the biological treatment resulted in mineralization of only about 23 percent in 26 days. The chemical treatment using the Fenton Reagent improved the mineralization regimes since the mineralization of 75 percent was achieved in a total time of less than 106 days, with a final degradation value of 82 percent obtained at 106 days. The effects of the biological, chemical and different combinations of these treatments were examined at different time intervals of 4 to 21 days. The results show that almost 50 percent of PCBs could be degraded within 4 days using the biological treatment (Table 1). However, the untreated land showed no significant degradation revealing that the - Bioaugmentation was necessary for the improvement of all the total degradation. At a pH of 7.0, the treatment of the aqueous slurry as a mixed culture of Pseudomonas sp. and Alcal ± genes eutrophus was more effective compared to the chemical treatment at the same pH. A combination of biological treatment followed by chemical treatment was slightly better compared to biological treatment alone. Subsequent biological treatment showed a further improvement in the revelation of PCBs with more than 70 percent of degraded PCBs within 15 days. This also shows that chemical treatment alters the total composition of PCBs in such a way that it improves accessibility through biodegradation.

Table 1. EFFECT OF THE CHEMICAL AND BIOLOGICAL TREATMENT OF PCBs IN AQUEOUS SUSPENSION EARTHED (pH 7.0) PCB treatment, ppm Initial Concentration 275.0 Not Treated 207.0 Chemical Only 194.5 Biological Only 110.0 Biological + Chemical 100.0 Biological + Chemical + Biological 60.0 - The chemical treatment portion of the process according to the present invention is carried out by contacting for chemical treatment the solid material contaminated with polynuclear aromatic hydrocarbon or the material contaminated with polychlorinated hydrocarbon after having been first bidigested aerobically or anaerobically with a liquid solution, preferably aqueous forming a mixture containing at least a sufficient amount and preferably an excess of ferrous ion to allow complete the reaction with the total hydrogen peroxide added to form the desired hydroxyl radical oxidant. We have found amounts based on the total mixture to be treated from about 0.1 weight percent to about 10 weight percent total hydrogen peroxide, and from about 0.1 weight percent to about 1 weight percent FeS04 as being effective . Preferred amounts of hydrogen peroxide are from about 0.5 weight percent to about 5.0 weight percent based on the total mixture being treated. We have found that such a low amount as well as 5.0 weight percent hydrogen peroxide preferably removes more than 70 percent of the polynuclear aromatic hydrocarbon compounds having 4 to 6 rings. The amount of hydrogen peroxide - - it can also be expressed as from about 10 milligrams to about 0.5 gram per gram of solids, such as earth in a slurry of aqueous suspension to be treated. The contact of the solid / liquid can best be achieved by suspending the solids in a liquid aqueous slurry. We have found that the chemical treatment portion of the process works well at comparatively high solids concentrations of about 10 percent to about 90 weight percent solids, based on the total aqueous slurry suspension. It is preferred that the agitation of the slurry is maintained for about 1 to about 12 hours after completion of the addition of the hydrogen peroxide. The pH of the aqueous slurry that is being treated should be acidic and preferably, a pH of about 4.0 to about 6.0 is appropriate. The chemical treatment portion of the biological / chemical / biological treatment process in sequence of this invention is carried out at a temperature of about 10 ° C to about 100 ° C. We have found a significant decrease in the desired oxidation of the polynuclear aromatic hydrocarbon compounds at both lower and higher temperatures. It is preferred to carry out the chemical treatment portion of the process of this invention at temperatures from about 20 ° C to about 40 ° C. In the preferred embodiments, due to the exothermic nature of the chemical reaction, the temperature is maintained by the slow addition of hydrogen peroxide to the aqueous slurry solution containing at least a sufficient amount of ferrous ion to react with all the hydrogen peroxide that is going to be added. The ferrous ion can be provided in an aqueous solution by hydrated FeS04 or any other iron salt or iron source, while providing the ferrous ion in a liquid solution. We have found suitable hydrogen peroxide addition regimes for the liquid solution in order to maintain the desired temperatures which are between about 1 milligram to about 300 milligrams of hydrogen peroxide per hour per gram of the contaminated solid material, depending on the material that is used. is treating and preferably about 1 to about 100 milligrams of hydrogen peroxide per hour per gram of the contaminated solid material. The chemical treatment portion of the process of this invention produces mainly carbon dioxide and water, which are environmentally acceptable and to a much lesser extent, partially oxidized products of the polynuclear aromatic hydrocarbon compounds such as hydroxylated or epoxidized compounds and polychlorinated hydrocarbon compounds, which are much more susceptible to bioremediation than the original polynuclear aromatic hydrocarbons particularly those containing from 4 to 6 rings of the original polychlorinated hydrocarbons. In the investigation we have completed a compound of 5 complex rings, the benzo (a) pyrene was irradiated with radioactive carbon and our tests showed that up to 40 percent of the irradiated carbon was collected as CO2 followed by a single chemical treatment in accordance with the present invention. This represents the total oxidation of a considerable portion of the bio-recalcitrant material. In accordance with one embodiment of the process of this invention, in the chemical treatment portion of the integrated process of this invention, a lower alcohol such as methanol or ethanol or mixtures thereof is added to the liquid solution. This addition of lower alcohol is particularly preferred when large numbers of polynuclear aromatic hydrocarbons of 4 to 6 weathered rings are present. Appropriate amounts of alcohol are from about 0.1 percent to about 80 volume percent based on the total aqueous slurry, and preferably from about 1 percent to about 10 percent by weight. one hundred in volume. The alcohol is miscible in water of the aqueous slurry and is not harmful to the last process of biodigestion. The presence of alcohol in the aqueous slurry results in unexpectedly high and often complete oxidation of the polynuclear aromatic hydrocarbons, particularly those with 4 to 6 carbon atoms. This result is unexpected because it was expected that the addition of any organic material would rapidly cool the activity of hydrogen peroxide in the polynuclear aromatic hydrocarbons. For example, we have found the inhibition of complete oxidation of benzo (a) pyrene in an amount of about 70 percent inhibition when 10 weight percent / volume of glucose or cellulose or lignin is added to the aqueous slurry in a manner similar. Optimization studies were carried out determining the operation of the biological treatment and the chemical treatment of the earth at different time intervals at a pH of 7. The results are shown in Figures 11 and 12. In summary, the results indicate that the 50 percent degradation of PCB, using biological treatment was obtained within 4 days with degradation increasing slightly up to 66 percent after 21 days of incubation. The chemical treatment was not very effective since only 21 percent of PCB degradation was achieved in 4 days of incubation of the batch with a maximum of 29 percent after 14 days of incubation. The chemical treatment was also examined at different pH, the results of which are shown in Figure 13. These results show that more than 41 percent of PCB degradation was obtained at pH 4.0 to 5.0, while only It obtained 21 percent degradation at a pH of 7.0. At a pH of 5.0 for the biological treatment, more than 83 percent degradation of PCBs by the integrated biological / chemical / biological approach according to the process of this invention was obtained (Figure 4). These results show that a patch of 5.0 is appropriate for the degradation of PCBs. Large reactor studies were carried out for degradation of PCBs in a stirred and aerated vessel. The experiments were carried out in a reactor of 7 liters capacity with an initial volume of 2.5 liters and 20 percent of the aqueous slurry. The purpose was to compare the PCB degradation pattern to the results of the study of the vial. The aqueous slurry was continuously aerated at low level by air spraying (20 milliliters per minute). A pH of 5.0 was used in this work and an optical density of 2.0 was used - for preparation of the aqueous thick biosuspension. The treatment was continued with the aqueous thick biosuspension consisting of mixed cultures of Alcal ± genes eutrophus and Pseudomonas sp. for 4 days. The pH of the reactor was continuously monitored using a data acquisition system. The pH increased from 5.17 to 5.61 in 4 days demonstrating the degradation of PCBs by the aqueous thick biosuspension. Subsequently, the Fenton Reagent (2 percent H2O2) was added to the aqueous thickened biosuspension mixture. The addition of the Fenton Reagent resulted in a slight drop in pH up to 5.47 which was further reduced to 5.2 by the addition of dilute HCl. The chemical treatment was continued for another three days. The pH increased to 5.72 demonstrating again the degradation of PCBs. The results, summarized in Figure 15, show that PCBs in contaminated lands were completely degraded in two months of treatment with more than 99 percent degradation occurring within one month after biological / chemical / biological treatment, in accordance with the process of this invention. Figure 16 is a schematic diagram of the process of this invention. The cells of the microorganisms suitable for use in the process of this invention were grown aerobically at 30 ° C on a rotary shaker. The medium was a means of sales - - phosphate stabilized minerals (PAS) containing diphenyl as a carbon source and supplemented with 0.005 percent yeast extract. The PAS medium was prepared by adding 77.5 milliliters of PA concentrate consisting of K2HPO4 (56.77 grams per liter), KH2PO4 (21.94 grams per liter) and NH4CI (27.61 grams per liter) and 50 milligrams of yeast extract to 910 milliliters of distilled water. After undergoing autoclaving and cooling, 10 milliliters of sterile PAS 100% salts comprising MgSO 4 (19.5 grams per liter), MnS? * H2? (5 grams per liter), FeS04 • 7H2O (1 gram per liter) and CaCl2 * 2H2? (0.3 gram per liter) together with several drops of concentrated H2SO4 per liter to prevent the precipitation of the basic salts. The commercially obtainable biphenyl was then added. The cell growth in the PAS medium was carried out for a period of 24 to 48 hours after which the cells were harvested and suspended in a phosphate stabilizer. Then, the cells were mixed with PCB congeners and incubated (bio-digested) for a period of 2 to 4 weeks. The resulting mixture was then chemically treated by contacting the Fenton Reagent (H2O2 4 percent volume / volume, FeS0 lOmM) followed by additional biodigestion for a period of 4 to 8 weeks.

- Although in the foregoing specification of this invention has been described in connection with certain preferred embodiments thereof, and many details have been disclosed for purposes of illustration, it will be apparent to those skilled in the art that the invention is susceptible to further embodiments and that certain of the details described herein may vary considerably without departing from the basic principles of the invention.

Claims (20)

R E I V I N D I C A C I O N E S:

1. A process for remedying contaminated solid materials that are selected from the group consisting of polynuclear aromatic hydrocarbon contaminated solid materials, polychlorinated hydrocarbon contaminated materials and mixtures thereof, by sequential biological / chemical / biological treatment comprising the steps of : biodigester the contaminated solid materials under appropriate conditions by means of a first aerobic or anaerobic digestion producing a first product of biodigestion; contacting for chemical treatment the first biodigester product with a hydrogen peroxide in the presence of ferrous ion in quantities and under conditions suitable for chemical oxidation, at a temperature within the range of approximately 10 ° C to 100 ° C, forming a mixing, and oxidizing the first biodigester product by producing biodegradable hydrocarbon materials that have improved biodegradability; and biodigester under appropriate conditions the materials produced by a second aerobic or anaerobic digestion.

2. A process according to claim 1, wherein a microorganism for biodigesting the contaminated solid materials and the materials produced comprises a microbial culture that is selected from the group consisting of Alcal ± genes eutrophus, Pseudomonas sp. , Rhodococcus and mixtures thereof.

3. A process according to claim 1, wherein the first aerobic or anaerobic digestion is carried out at a pH within the range of about 4.0 to 6.0.

4. A process according to claim 2, wherein the microorganism is concentrated to an optical density within the range of about 0.2 to 5.0.

5. A process according to claim 1, wherein the total hydrogen peroxide is from about 0.1 percent to about 10 percent by weight of the mixture.

6. A process according to claim 1, wherein the total hydrogen peroxide is from about 0.5 percent to about 5 percent by weight of the mixture.

7. A process according to claim 1, wherein the hydrogen peroxide is- add to a sufficient regimen to maintain that temperature.

8. A process according to claim 7, wherein the hydrogen peroxide is added at a rate of about 1 milligram to about 300 milligrams of hydrogen peroxide per hour per gram of the contaminated solid materials.

9. A process according to claim 7, wherein the hydrogen peroxide is added at a rate of about 1 milligram to about 100 milligrams of hydrogen peroxide per hour per gram of the contaminated solid materials.

10. A process according to claim 1, wherein the contaminated solid materials comprise at least one soil and one sediment.

11. A process according to claim 1, wherein the contaminated solid materials comprise from about 10 percent to about 90 percent by weight of the mixture.

12. A process according to claim 1, wherein the hydrogen peroxide and the ferrous ion are placed in a liquid solution comprising a lower alcohol. -

13. A process according to claim 12, wherein the lower alcohol is selected from the group consisting of methanol, ethanol and mixtures thereof.

14. A process according to claim 12, wherein the lower alcohol is present in an amount of about 0.1 percent to about 80 percent by weight based on the volume of the mixture.

15. A process according to claim 12, wherein the lower alcohol is present in an amount of about 1 percent to about 10 percent by volume based on the total mixture.

16. A process according to claim 1, wherein the predominant portion of the polynuclear aromatic hydrocarbon comprises from 4 to 6 carbon rings. A process according to claim 1, wherein the polynuclear aromatic hydrocarbon comprises predominantly from 4 to 6 carbon rings, the total hydrogen peroxide is from about 0.1 percent to about 10 percent by weight of the solid materials contaminated and mixed, and hydrogen peroxide is added at a rate sufficient to maintain that temperature. 18. A process for the one-site remedy of contaminated soil particles that are selected from the group consisting of soil particles contaminated with polynuclear aromatic hydrocarbon, soil particles contaminated with polychlorinated hydrocarbon and mixtures thereof by biological / chemical treatment / biological in sequence in situ, comprising the steps of: biodigesting contaminated soil particles under appropriate conditions through a first aerobic or anaerobic digestion producing a first product of biodigestion; contact for chemical treatment the first biodigestion product with hydrogen peroxide in the presence of a ferrous ion in quantities and under conditions suitable for chemical oxidation at a temperature of about 20 ° C to about 100 ° C, oxidize the contaminants that produce materials of biodegradable hydrocarbons that have improved biodegradability and biodigested under appropriate conditions of materials produced by a second aerobic or anaerobic biodigestion. 19. A process according to claim 18, wherein the hydrogen peroxide and the ferrous ion are placed in a liquid solution comprising a lower alcohol. 20. A process according to claim 19, wherein the lower alcohol is present in an amount of about 0.1 percent to about 80 volume percent based on the solid materials in the liquid.