United States Environmental Protection Agency EPA/540/SR-94/531 March 1995 SUPERFUND INNOVATIVE TECHNOLOGY EVALUATION Emerging Technology Summary Bench-Scale Testing of Photolysis, Chemical Oxidation, and Biodegradation of PCB Contaminated Soils, and Photolysis of TCDD Contaminated Soils The tests reported herein were con- ducted by IT Corporation, Knoxville, TN, to investigate the feasibility of a two- phase detoxification process that would potentially have application to the treat- ment of soils contaminated with PCBs and 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). The first step in the process was to degrade the organic contami- nants by using ultraviolet (UV) radia- tion. The source of UV radiation was either artificial UV light or natural sun- light, but generally photolytic processes are more rapid with artificial UV light. Alternatively, advanced oxidation pro- cesses, such as iron catalyzed hydro- gen peroxide (Fenton's Reagent), were used to provide primary contaminant degradation. Both photolysis and chemical oxidation were expected to convert contaminants to more easily biodegradable compounds. Biological degradation, the second step, was then used to further destroy organic con- taminants and detoxify the soil. Bio- degradation is enhanced by the addition of microorganisms and nutrients to the UV-treated soil. The results of bench-scale testing on degradation of TCDD by using UV pho- tolysis, and PCB degradation by using both UV photolysis and chemical oxi- dation, indicate that there was no ap- parent destruction of the dioxin on the soil, 23% to 69% destruction of PCBs in UV Tests, and 0% to 53% reduction in chemical oxidation tests. Bioslurry experiments evaluated the biological reduction of PCB congeners in surfactant/UV-treated and untreated soils. Experiments were also conducted to evaluate the impact of PCB-blodeg- radation inducers, biphenyl and 4- bromobiphenyl, on congener removal. Bioslurry treatment did not provide sig- nificantly different results for the UV- treated surface soil versus the untreated soil. This Project Summary was developed by EPA's Risk Reduction Engineering Laboratory, Cincinnati, OH, to announce key findings of the SITE emerging tech- nology that is fully documented in a separate report of the same title (see Project Report ordering information at back). Introduction Polychlorinated dioxins, furans, and bi- phenyls (PCBs) are the most recalcitrant Printed on Recycled Paper ------- vvEPA United States Environmental Protection Agency EPA/540/SR-94/531 March 1995 SUPERFUND INNOVATIVE TECHNOLOGY EVALUATION Emerging Technology Summary Bench-Scale Testing of Photolysis, Chemical Oxidation, and Biodegradation of PCB Contaminated Soils, and Photolysis of TCDD Contaminated Soils The tests reported herein were con- ducted by IT Corporation, Knoxville, TN, to investigate the feasibility of a two- phase detoxification process that would potentially have application to the treat- ment of soils contaminated with PCBs and 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). The first step in the process was to degrade the organic contami- nants by using ultraviolet (UV) radia- tion. The source of UV radiation was either artificial UV light or natural sun- light, but generally photolytic processes are more rapid with artificial UV light. Alternatively, advanced oxidation pro- cesses, such as iron catalyzed hydro- gen peroxide (Fenton's Reagent), were used to provide primary contaminant degradation. Both photolysis and chemical oxidation were expected to convert contaminants to more easily biodegradable compounds. Biological degradation, the second step, was then used to further destroy organic con- taminants and detoxify the soil. Bio- degradation is enhanced by the addition of microorganisms and nutrients to the UV-treated soil. The results of bench-scale testing on degradation of TCDD by using UV pho- tolysis, and PCB degradation by using both UV photolysis and chemical oxi- dation, indicate that there was no ap- parent destruction of the dioxin on the soil, 23% to 69% destruction of PCBs in UV Tests, and 0% to 53% reduction in chemical oxidation tests. Bioslurry experiments evaluated the biological reduction of PCB congeners in surfactant/UV-treated and untreated soils. Experiments were also conducted to evaluate the impact of PCB-blodeg- radation inducers, biphenyl and 4- bromobiphenyl, on congener removal. Bioslurry treatment did not provide sig- nificantly different results for the UV- treated surface soil versus the untreated soil. This Project Summary was developed by EPA's Risk Reduction Engineering Laboratory, Cincinnati, OH, to announce key findings of the SITE emerging tech- nology that is fully documented in a separate report of the same title (see Project Report ordering information at back). Introduction Polychlorinated dioxins, furans, and bi- phenyls (PCBs) are the most recalcitrant Printed on Recycled Paper ------- environmental contaminants. To remove or destroy contamination on soils, rela- tively high-temperature thermal treatment or harsh chemical treatment is required. These treatments are expensive and can significantly alter the composition of the soil. The use of UV light to destroy dioxins or RGBs in solutions has long been known. More recently, the use of UV light to de- stroy these compounds on soils was in- vestigated. Typically, the reaction is aided by the presence of a solvent or solubiliz- ing aid, such as a surfactant, which is transparent to the UV radiation in the re- gion of activity (generally 254 nanometers) and which has increased solubility for the contaminants being destroyed. The irra- diation process can be performed on ex- cavated soils or in situ with the use of enhanced radiation from lamps or natural sunlight. The process usually involves the continued application of the solubilizing aid and continued exposure of fresh sur- face to the irradiation source. The solubil- ity aid helps to transfer the contaminant from the pores of the soil to the surface of soil where the reactions can take place. The surfactant or solubilizing aid may also act as a medium for the degradation pro- cess by providing labile protons to allow the reaction to proceed more easily. Chemical oxidation by Fenton's Reagent has been used to destroy organic com- pounds such as formaldehyde, azo dyes, and chlorinated phenols in groundwaters and wastewaters. The reaction is ideally performed at a pH of 2 to 4 by using hydrogen peroxide as the oxidant in the presence of a ferrous salt. Ferrous ions catalyze the decomposition of hydrogen peroxide. In the process of decomposi- tion, the reactive hydroxyl radical is pro- duced, and it is capable of oxidizing organic contaminants. If, however, the de- sired oxidation reaction is slow, significant amounts of hydrogen peroxide can be con- sumed in unproductive decomposition in- stead of participating in the desired process. Reaction conditions must be es- tablished to provide useful rates of con- taminant oxidation with efficient use of hydrogen peroxide reagent. Aerobic biodegradation of the lower chlo- rinated PCB congeners (1 to 3 chlorines) has been well documented. The more highly chlorinated congeners are, however, generally resistant to microbial attack, al- though there have been reports of micro- bial degradation of the higher-chlorinated PCB congeners (>4 chlorines). Biological degradation of PCB congeners is highly affected by the chlorination pattern and the number of chlorines per biphenyl. Fur- ther hindering microbial biodegradation of PCB is their hydrophobicity, which inhibits their bioavailability. To increase the rate and extent of PCB biodegradation, two conditions are necessary: the bioavailability of the PCB should be increased, and the chlorination level per biphenyl ring should be decreased. This study addressed the bioavailability and microbial attack of PCB after the combined surfactant/UV treat- ment of highly contaminated PCB soil. Process Description This two-phase treatment is envisioned as a potential in-situ process for shallow contamination on soils. More probable, however, is the use of the technology for ex-situ on-site treatment of excavated soils in a specially constructed shallow treat- ment basin—one meeting the requirements of the Resource Conservation and Recov- ery Act (RCRA). The entire process may require longer treatment times than other technologies, but have a trade off in economy. In addition, the only residue gen- erated from this combination of technolo- gies is soil contaminated with surfactants and the end metabolites of the biodegra- dation processes. The end metabolites will depend on the original contaminants, and the surfactants are common materials used in agricultural formulations. UV Photolysis Performance UV photolysis testing was performed on three soils, one containing TCDD con- tamination and two containing PCB con- tamination. The tests were conducted independently by using a medium-pres- sure Hg lamp, a 10-Hz pulsed lamp and sunlight, and by employing different sur- factants and surfactant application proce- dures. Tests were carried out with either the 450-watt medium pressure Hg lamp or the 70 watts/in, pulsed lamp operating approximately 10 in. above the soil with a parabolic reflector above the lamp. A composited TCDD soil from a Vertac site in Jacksonville, AR, using two surfac- tant levels, 2.5% and 5% by weight of the dry soil, was tested. TCDD concentrations on the soil ranged from about 200 to 300 ppb. The soil was mixed and sprayed at 1/2-hr intervals with either surfactant solu- tion or water for a total irradiation time of 48 hr. Results from these tests indicated no apparent destruction of the dioxin on the soil in any of the tests. Surface soil from a Texas Eastern Gas Pipeline site in Armaugh, PA, contami- nated with about 10,000 ppm PCBs (Aroclor 1248) and a pit soil from the same site containing about 200 ppm PCBs were tested under the same conditions given above using different surfactants, application procedures, soil mixing, etc. The results of all of the experiments are summarized in Table 1. Chemical Oxidation Performance Five batch experiments using the H20,/ Fe (Fenton's) reagent system were done at ambient temperature. All five used the same clay/humic surface soil that was used in the UV photolysis testing. This soil pro- vided samples for treatment that ranged from 5000 to 10,000 ppm PCBs (Aroclor 1248). Conditions were established to pro- vide the best opportunity for observing an effect due to treatment. Each experimen- tal mixture was pH adjusted to a pH be- tween 2 and 4 and continuously stirred. Hydrogen peroxide concentration was monitored throughout each experiment and additions were made as necessary to maxi- mize concentration. Reagent-to-soil ratios were high, and Fe concentrations were varied between experiments to investigate the effect. The treated soil was analyzed either at the end of the treatment time or sampled at selected times throughout the run if sufficient soil was used in the test. Results from testing are summarized in Table 2. Biological Treatment Performance The ability of selected organisms to biotransform PCB congeners in surfac- tant/UV-treated and untreated soil was evaluated during two bioslurry treatment experiments. The first bioslurry experiment evaluated the biological reduction of PCB congeners in surfactant/UV-treated and untreated soils. A subsequent enhanced bioslurry experiment evaluated the impact of PCB-biodegradation inducers on con- gener removal. Previous studies show that the addition of biphenyl, 4-bromobiphenyl (4-BB), 4-chlorobiphenyl, 2-chlorobiphenyl, or other monochlorobiphenyls have in- duced and enhanced aerobic PCB bio- degradation. The bioslurry experiments were con- ducted under aerobic conditions at 25°C using PCB-degrading organisms from two sources. PCB-degrading organisms were isolated from an impacted New England Superfund Site soil (BAG 17). In addition, known-PCB degrading microorganisms were obtained from General Electric Cor- poration (GE; H850). Three PCB-contami- nated soils were evaluated for biological reduction of PCB congeners. Soils em- ployed were identified as untreated sur- face soil from the UV photolysis testing, surfactant/UV-treated surface soil, and New England Superfund Site soil. In sepa- rate tests, each soil was treated with the bacteria cultures, BAG 17 and H850. In ------- Table 1. Summary ofUV Photolysis Results on PCB Contaminated Soil Test 1 2 3 4 5 6 7 8 9 10 11 Soil Type surface surface surface pit pit pit pit pit pit surface surface Soil Depth in. 0.25 0.25 0.25 0.5 0.5 0.5 1.0 1.0 1.0 0.25 0.25 Surfactant, % 2 2 2 2 2 2 4.5 2 0 2.5 2.5 Lamp Type pulsed medium pressure pulsed medium pressure Hg medium pressure Hg pulsed pulsed solar irradiation solar irradiation solar irradiation medium Hg medium Hg Temperature °C 25 28 40 30 28 28 30-40 30-40 30-40 Time (Hr) 12 7 7 16 16 12 25 days 25 days 25 days 20 20 Initial PCB Cone., ppm 7240 7430 8440 140 157 170 132 159 171 10000 10000 Final PCB % Reduction <15 <15 33 30 13 23 <15 <15 <15 52* 32 'Increase in concentration noted for di-PCBs, decrease in concentration for tetra through hepta-PCBs. Table 2. Summary of Chemical Oxidation Testing Test 1 2 3 4 5 Amount of Soil, g 10 8.0 8.1 170 196 w/surfactant Water/Soil Ratio 9.7 8.4 9.5 10.1 8.0 pH 2.8 2.5 2.2 3.1 2.9 Fe, % of Soil 2.5 0.1 0.5 .09 .09 H2O2Conc. (%) Average .07 1.8 0.87 1.6 0.88 Time (Hr) 162 118 118 845' 184 Percent Reduction of Starting PCB Concentration 44 55 45 35 <,5 'No further decrease in PCB concentration observed after 211 hr. ------- addition a killed control sample was pre- pared for each soil. Table 3 summarizes the reductions measured for the PCB ho- mologs after four weeks. In the enhanced bioslurry experiment, the effect of adding 1,000 mg/L biphenyl inducer and 1,000 mg/L 4-BB inducer on PCB biodegradation was investigated. The BAG 17 culture was used with the New England Superfund Site soil and the un- treated soil because these combinations demonstrated the highest PCB reductions in the bioslurry experiment. The soils were tested with both inducers. Table 4 sum- marizes the reductions measured for the PCB homologs after one week. Conclusions UV photolysis treatment gave no de- tectable decrease in soil TCDD concen- tration in the tests conducted and minimal reduction of PCBs. The PCB reductions ranged from less than 15% to a maximum of 52% The decreases in concentration were highest for higher level chlorinated PCBs (tetra through hepta-PCBs). In some cases greater decreases in concentration of lower chlorine level PCBs were noted. These were suspected to have been lost due to volatilization in tests at increased temperatures caused by the heat gener- ated by the UV lamp, along with the high soil surface area exposed. Chemical oxidation with Fe catalyzed hydrogen peroxide also provided minimal reduction of PCBs on the highly contami- nated surface soil tested. The PCB con- centration reductions ranged from less than 15% to a maximum of 55% in reaction times of well over 100 hours. Highest re- ductions were observed with higher Fe-to- soil ratios and maximized concentrations of hydrogen peroxide, up to 2%, by peri- odic additions. Where concentrations were reduced, the losses of PCBs were ob- served more from the lower chlorinated homologs (di and tri-PCBs) and less from the higher chlorinated homologs (tetra through hepta-PCBs). . Bioslurry treatment did not provide sig- nificantly different results for the UV-treated surface soil versus the untreated soil. This was not surprising since UV treatment was not successful in significantly degrading the higher chlorine level PCB homologs. Percent reductions of PCBs were highest for a New England Superfund Site soil that had a significantly lower concentra- tion of PCB contamination. The culture isolated from the New England soil gave 70% 20% and 30% reduction of the di, tri and tetra-PCBs, respectively, in the New England soil. PCB reductions less- ened with increasing level of chlormation with no significant reduction noted for penta, hexa, or hepta-PCBs. Similar re- sults were obtained with inducer additions to the soils. Biphenyl addition gave even greater reduction in PCB concentrations for the New England site soil with reduc- tions of 82%, 54%, 63% and 16% for di, tri, tetra, and penta-PCBs, respectively. Recommendations Although the percent of PCB degrada- tion was low, meaningful destruction rates may have been masked by the high con- centration of PCBs in the surface soil that was used in many of these tests. Although the lower PCB concentration pit soil was used in some of the photolysis tests with little difference in results, a more detailed analysis of the processes would be al- lowed if soils with lower, but still practical PCB concentrations (<1000 ppm), were used in this early phase of testing. High amounts of surfactant were car- ried through the treatment process and may have been inhibitory to bacterial ac- tivity or promoted non-PCB degrading ac- tivity. Likewise, the treated soil had a pH of 5.5, which may have been inhibitory to the bacteria and probably was a result of surfactant addition. An additional soil wash- ing step may be necessary to remove/ recycle surfactant from the soil and neu- tralize the pH before biological treatment. In addition, correlations of PCB-degrad- ing activity with soil type, PCB concentra- tion and composition, biphenyl/PCB concentrations, and bacterial populations need to be explored. Both of these processes may be en- hanced by adding surfactants to the soil to solubilize the contaminants and to pro- vide a medium for reaction mass transfer processes. . The full report was submitted in fulfill- ment of Cooperative Agreement No. CR816817-02-0 by IT Corporation under the sponsorship of the U.S. Environmen- tal Protection Agency. Table 3. Percent Loss of Homolog Groups at Four Weeks Bioslurry Evaluation Dichlorobiphenyl Trichlorobiphenyl Tetrachlorobiphenyl Pentachlorobiphenyl Hexachlorobiphenyl Heptachlorobiphenyl 24 0 0 0 0 0 21 16 0 0 0 0 Untreated Soif 67 0 0 0 0 0 0' 0 0 0 0 0 New England So//0 70 20 30 0 0 0 40 0 0 0 0 0 *Surfactant/UV-treated surface soil - 4000 mg/Kg total PCB. "Untreated surface soil - 8400 mg/Kg total PCB. 'New England Superfund Site soil - 350 mg/Kg total PCB. " Segrad^on /ess tnan 15% is not considered significant and is reported as zero.. ------- |