Goals: Research objectives are to investigate suitability of deep-planted poplars as a vegetative remediation strategy all future measurements could be compared. Survival measurements and leaf samples have been taken. As of September 1995, 400 out of the original 576 trees were alive for an overall survival rate of 69.4%. Addition of manure to the trenches significantly increased growth via increases in height and trunk diameter. The data clearly show that tree cultivar and soil amendments can influence survival and growth parameters. Soil samples have been collected from eight different areas and analyzed for lead concentration. Soil lead concentrations will be compared to leaf tissue lead concentrations after those analyses are complete. This project is in its third year.
Rationale: Abandoned sites associated with old heavy metal mining and smelting activities often have a large proportion of their area without vegetative cover. This allows erosional forces to proceed at a maximum rate, and materials with high heavy metal concentrations are dispersed by wind and water. Little research has addressed use of poplar trees in such a situation.
Approach: This study will focus on an abandoned zinc and lead smelter site in southeast Kansas. The investigators propose to begin investigations whose ultimate goal is to immobilize the metals in place. This would be accomplished with grading to 3-5% slope, to encourage runoff without excessive erosion, and the use of rapid growing poplar trees that have a high water demand. This strategy would minimize net percolation through mine spoil material, thus minimizing impact on ground water. Surface erosion would be effectively controlled once the trees are established. A thin soil cover would be employed to establish a perennial grass cover to prevent surface erosion until the trees had become established.
Status: This project has utilized an abandoned zinc/lead smelter site near Dearing, Kansas, for its investigation. Poplar trees were first planted in June 1994 but survival as of September of that same year was only 7%. This was attributed to the late planting date (which was necessary because of extremely wet conditions), a reduction in tree viability due to storage, and droughty conditions following planting. The trees were replanted in March 1995, a more appropriate planting time, in a split-plot design with the main plots being the in-trench treatments with or without manure and the subplots being poplar cultivar. Height and trunk diameter of each tree was measured to serve as a baseline to which all future measurements could be compared. Survival measurements and leaf samples have been taken. As of September 1995, 400 out of the original 576 trees were alive for an overall survival rate of 69.4%. Addition of manure to the trenches significantly increased growth via increases in height and trunk diameter. The data clearly show that tree cultivar and soil amendments can influence survival and growth parameters. Soil samples have been collected from eight different areas and analyzed for lead concentration. Soil lead concentrations will be compared to leaf tissue lead concentrations after those analyses are complete. This project is in its third year.
Clients/Users: This research is of interest to the mining industry and regulatory community.
Key words: heavy metals, soil, poplar trees, zinc, lead.
Goal: The goal of this project is to quantify the process of heavy metals removal by binding to biopolymers from dilute aqueous solutions containing more than one metal.
Rationale: Extracellular polymers extracted from living microorganisms constitute an attractive alternative for heavy metals removal from dilute aqueous solutions. However, demonstrated technologies do not offer any rational means of predicting the process kinetics as a function of water chemical composition. Thus far the documented research effort is largely related to binding single metals from aqueous solutions. Such convenient simplification is unacceptable for most technical applications of the process. For example, it is a rare exception that a water is contaminated with a single heavy metal. In frequently encountered situations when more than one heavy metal is present in the solution, existing models do not apply, and the result of the process cannot be predicted.
Approach: Investigators propose describing the kinetics and thermodynamics of metals binding to biopolymers from solutions of many metals. Relevant parameters for process modeling will be obtained from measurements of binding constants, binding capacities, selectivity coefficients, diffusion coefficients, and rates of metal binding reaction. Predictive value of the models will be experimentally verified.
Status: Biopolymer gel bead binding to heavy metals in water taken from the Berkeley Pit has been studied, and field studies using beads for heavy metal uptake at acid mine drainage sites have been initiated. In order to make use of this technology economically feasible, the beads must be regenerated and reused many times. Regeneration and reuse studies have begun. In mixtures of copper and zinc, binding constants and binding capacities under competition have been determined, and hydrogen ion has been included as a cation. Since concentrations of metals in the solution were relatively high, metal alginate gel beads were formed in situ. The experimental data closely fit the extended Langmuir model, allowing binding group density and stability constants to be determined. A model which predicts final concentrations of divalent cations in solutions comprised of mixtures of the metal ions and protons in the presence of alginate biopolymer gel beads is being developed. The model predicts equilibrium concentrations of copper, zinc, and hydrogen ions in the presence of alginate gel beads. Results show that alginate is much more selective for copper than for zinc. A key finding has been that the maximum binding capacity for alginate is independent of metal type. Investigators are comparing bead regeneration efficacy using equilibrium shifting plus electrodeposition to equilibrium shifting alone and to electrodeposition alone. Investigators are preparing to submit a patent application related to biopolymer regeneration. This project is in its third year.
Clients/Users: Results are of interest to other researchers, private industry, and regulatory personnel.
Key words: heavy metals, water, biopolymers, sodium alginate.
Goal: The goal of the research is to determine feasibility and efficacy of vegetative remediation at a variety of sites with heavy metals soil pollution.
Rationale: Mine tailings and metals pollution of soils is a major problem globally, and it has been identified as a primary research priority area of the Great Plains/Rocky Mountain Hazardous Substance Research Center. The New York Times reported recently that mine tailings wastes account for almost half of all hazardous wastes worldwide. Risk assessments at Superfund sites often reveal that exposure to wind-blown dust by inhalation and ingestion of soil by children is the greatest risk to human health.
Approach: The proposed research is a comparative study at two sites (Dearing, Kansas, and Whitewood Creek, South Dakota) with greatly different problems, so the scope of the research is to expand the applications to determine more broadly the potential of this innovative approach. In this research the investigators will attempt to establish vegetation at these sites where it has not already been accomplished and to monitor movement of metals in the soil profile as a result of the remediation effort. The research will supplement and continue ongoing research of investigators at Whitewood Creek.
Status: This project has utilized an abandoned gold mining area near Whitewood Creek, South Dakota, for its investigation. Poplar trees were planted in May 1993, but survival has been compromised by frosts, hail damage, drought, deer browse, and apparent toxicity. Nevertheless, sufficient data have been collected to determine that poplar trees can survive in this relatively harsh environment and that the levels of arsenic and cadmium in leaf tissue are not of concern. In June 1995, there were approximately 150 poplar trees still living from a total of 3,000 that were planted in 1993. The surviving trees were sampled in order to understand long-term uptake and translocation of metals. Most of the poplar trees which grew well were concentrated in a specific area, and their heights were around 3.5 to 4.5 feet. The total number of well-developed poplar trees was approximately 80. The other poplar trees, which grew poorly, were scattered throughout portions of the site, and their heights varied from six inches to two feet. The poorly-developed poplar trees survived with native plants at the site. Fresh leaves and stems were sampled from poplar trees at eight different sites. Dead leaves and stems were collected from the ground where fresh leaves and stems were sampled. Surface soil was also collected from within a one foot radius around each sampled poplar tree. One whole tree was extracted, including roots. Soil samples at depths of 3, 9, 18, and 20 inches were collected from this same area. These samples will be analyzed for arsenic, cadmium, zinc, and lead. This project is in its third year.
Clients/Users: This research is of interest to the mining industry, regulatory community, and other researchers.
Key words: metals, soil, pollution, remediation, poplar trees.
Goal: This project will attempt to demonstrate an alternative, cost-effective, permanent mine tailing reclamation methodology through the marriage of mineral processing and land reclamation techniques. The approach to be used, Clean Tailing Reclamation (CTR), utilizes potentially field deployable mineral separation technologies to remove dense sulfide minerals from tailing material by gravimetric separation, followed by vegetative stabilization of the cleaned tailing material with native plants. CTR will allow for removal of environmental contaminants and acid-forming materials.
Rationale: Mine waste is a widespread and pervasive problem in EPA Regions VII and VIII. Historical mining activity has contaminated many thousands of acres of soil by uncontrolled waste disposal practices resulting in resource degradation that will cost billions of dollars to remediate. One of the principal problems associated with reclamation of hardrock mine sites is tailing reclamation. Tailing materials cover tens of thousands of acres of land in the region pair. This research specifically compliments research being conducted in Anaconda, Montana, on tailing reclamation and will provide comparisons on the relative strength of this technology, through plant performance, geochemical distribution of contaminants, and cost of implementation. Upon completion of this research, the findings will be useful to Superfund Managers and Potentially Responsible Party decision makers and to operational mines and regulators.
Approach: Research will be implemented at Montana State University. Outside expertise will be solicited from other experts in mineral separation in conjunction with the use of experimental equipment housed at Butte, Montana. Contract laboratories will be solicited and appropriate sample analyses will be submitted for analysis. Sample material used in research will be collected from three locations in coordination with regulatory personnel. Representative samples of tailings materials will be collected from each of the three locations and chemically characterized to identify the elemental and mineralogical distribution of the heavy metal and acid generating contaminants. Subsequent to sample characterization, mineralogical separation of the dense sulfide minerals will be performed using gravimetric techniques. For bench-scale work, mineral separation technologies considered will include technologies developed through the Superfund Innovative Technology Evaluation (SITE) Program. Following tailing material reprocessing activity, subsamples will be chemically characterized to determine the efficacy of the reprocessing/tailing cleaning technologies. Greenhouse studies will be implemented in the cleaned tailing material to compare performance of the cleaned tailing material with conventional reclamation approaches. The native grass species selected for use are Red top (Agrostis alba) and Basin wildrye (Leymus cinereus).
Status: This project is in the information gathering phase. Individuals who have equipment of sufficient capacity to separate large quantities of waste which will be necessary for field studies have been located. One of these will be contracted to carry out physical separation of the tailings prior to implementation of the field amendment and seeding. This project is in its first year.
Clients/Users: This research will be of interest to those in the mining industry and regulatory agencies.
Key words: vegetation, reclamation, metallic minerals, mining, tailings.
Goal: The goal of this project is to assess the full potential of chelating extraction technology in removing and/or recovering heavy metals from contaminated media, e.g., soils and mine tailings ponds. A large number of chelators will be examined, and those chelators which are suitable for selective removal or recovery of various heavy metals will be identified.
Rationale: Heavy metal contamination of soil is a common problem encountered at many hazardous waste sites. Lead, chromium, cadmium, copper, zinc, and mercury are among the most frequently observed metal contaminants. They are present at elevated concentrations at many National Priority List sites, are toxic to people, and threaten ground water supplies. Once released into the soil matrix, most heavy metals are strongly retained and their adverse effects can last for a long time. Chelating extraction of heavy metals from contaminated soils is a relatively new treatment method. There exists a need to assess the full potential of this technology in removing and/or recovering heavy metals from contaminated media. A methodology is needed to examine a large number of chelators and identify those chelators suitable for the selective removal or recovery of various heavy metals. Chelators that are identified, studied, and recommended as a result of this project could be used in on-site soil washing processes following excavation.
Approach: Investigators will assess the potential of extracting and recovering heavy metals from contaminated soils using chelators. Results of assessment of a large number of chelators will provide a guide to select suitable chelators for different metals. Equilibrium chemical modeling/calculation and connectivity index modeling will be performed to choose about ten chelators from the initial list for detailed experimental study. Study will be conducted on the extraction and recovery of the seven target metals from collected contaminated soils using ten selected chelators. Investigators will also demonstrate that through a proper choice of functional groups in a chelator, the selectivity of the chelator can be greatly enhanced and that through a proper choice of chelator, extracted mixed metals can be recovered separately through sequential treatment stages. Finally, stability of about six chelators will be evaluated with respect to biodegradation.
Status: Over 700 potential organic chelating agents have been screened and about two hundred selected for further evaluation. The complexation constants of about 170 chelators with lead and copper were used as a database to determine the quantitative structure-activity relationship. Results indicated that the complexation ability of the chelating agents are determined by factors including various molecular descriptors, numbers of hydroxyl, amino, carboxylic groups, as well as protons and heteroatoms. From modeling and computation results, ten chelators were selected for experiments. Results showed that (1) lead, copper, cadmium, and zinc can be extracted from contaminated soils using various chelating agents N-(2-acetamido)iminodiacetic acid (ADA), pyridine-2,6-dicarboxylic acid (PDA), and S-carboxymethyl-L-cysteine (SCMC); (2) the metals can be readily separated and recovered as metal precipitates by simply raising the solution pH; (3) the chelators that remained in solution after separation were successfully reused for further extraction during consecutive runs. Results suggest that ADA is particularly effective for extraction of lead while SCMC is especially effective for copper. Three additional chelators are currently being tested. Three organizations have expressed strong interest in the possible commercialization of these research results. This project is in its first year.
Clients/Users: This research will be of interest to public agencies such as U.S. Environmental Protection Agency, U.S. Department of Defense, and industry.
Key words: heavy metals, chelators, extraction, lead, copper.
Goals: The overall objective of this research is to determine whether establishment of vegetation in heavy metal and radionuclide contaminated soil will significantly affect retention of metals in soils and to mathematically predict the results using a calibrated model.
Rationale: Vegetation is often the primary method of reclamation in mining areas to stabilize waste with respect to wind and water erosion and to minimize downward translocation of contaminants. Plants reduce the possibility of metal leaching through decreased water infiltration, adsorption of metals to root surfaces, plant uptake of metals, and stimulated microbial immobilization in the rhizosphere. Plants may increase metal leaching through complexation with rhizosphere organic acids exuded by roots, produced by microbial activity, or generated by decomposition of soil organic matter. Field and laboratory determinations are needed to quantify effects of vegetation on the leaching of metals. Models that attempt to predict the fate of heavy metals in soils have focused primarily on the geochemical aspects of the problem and have not considered the effect of a plant's geochemistry. The difficulty associated with using models to simulate the fate of a heavy metal in the root-soil environment is properly accounting for all interactions between water movement, contaminant transport, uptake of water and metals by plant roots, and geochemistry.
Approach: Impact of vegetation and revegetation schemes on the mobility of metals (lead, cadmium, zinc, barium, etc.) is being investigated on contaminated soil and/or mine waste from zinc and lead mining regions of southeast Kansas, lead mines of Montana, and a paint-producing industry in southern Kansas. The following series of experiments will be employed to pursue the objectives: a sequential extraction procedure for determination of various fractions and mineral associations of the metals; batch (laboratory-scale equilibrations) and column experiments to directly assess impact of organic acids on heavy metal mobility; large soil columns to determine effects of vegetation overlying soil depth on mobility of metals and metal uptake by plants; sorption/desorption and determination of potential or existing solid phases of the metals to quantify the soil chemical aspects of metal retention; and integration of geochemical and solute transport modeling to predict and analyze the fate of metals as influenced by the presence of vegetation.
Status: Soils and mine tailings have been thoroughly characterized for their important chemical and physical properties as well as the chemical fractions of the metals. Investigators have used x-ray diffraction to identify predominant minerals. Conclusions drawn from this aspect of the study are that high concentrations of readily mobile metals exist in all the soils and tailings, but the predominant fraction depends upon the source of the material. The southeast Kansas mine tailings and soils tend to have the metals present as carbonates and/or sulfides. The Montana mining waste has significant amounts of heavy metals in organic and "unclassified" or residual fractions. Highly contaminated industrial soil from southern Kansas has lead present as oxides and carbonates. These results suggest that metals present in the mining wastes tend to be a long-term threat to the environment as the sulfides and carbonates weather. Lead in the industrial soil can be controlled if the soil is stabilized. Initial batch and column experiments coupled with geochemical modeling have determined that very few naturally occurring organic acids have the capability to mobilize heavy metals, and these acids must be present in concentrations not usually found in soil. For example, citrate will solubilize zinc and lead at concentrations of 3.0 mmol/L or greater, but citrate is usually present at < 0.05 mmol/L. There is also evidence that the presence of organic acids in concentrations typical of the rhizosphere will decrease metal mobility. Larger column experiments testing interaction between plants and metal mobility as affected by soil cover have been initiated. This project is in its first year.
Clients/Users: This project is intended to be of interest to any group that is involved in restoration of land contaminated by heavy metals, including U.S. Environmental Protection Agency, U.S. Department of Energy, Kansas Department of Health and Environment, and U.S. Department of Defense.
Key words: vegetation, heavy metals, radionuclides, soil, fate and transport.
Goals: This research has two purposes. First, the efficacy of different plant and microbial regimes in reducing surface water contamination from revegetated plots will be assessed. To determine the ability of various vegetation/microbial regimes to act as buffer strips, after the first year of the project the design of the experiment will be altered. Half of the plots will remain as non-interceptor strips, while half will receive surface runoff from contaminated tailings uphill from the plots. In this way the ability of the various vegetation strips to limit heavy metal contaminated runoff can be quantified.
Rationale: In southeastern Kansas where heavy metals were mined until the middle of this century, the presence of large piles of gravel tailings with extremely high levels of cadmium, lead, and zinc pose a serious environmental and health risk which led the U.S. Environmental Protection Agency to designate this area as a Region VII Superfund Site in 1985. In areas not designated as Superfund sites, a need also exists for development of economic strategies for containment of heavy metal contamination. While vegetation interceptor strips have been used extensively in agricultural settings to reduce surface water contamination by agricultural herbicides and pesticides, the ability of vegetation buffer strips to limit spread of heavy metal contamination in surface water has not been studied, but could represent an economical alternative with broad application to mine spoils and areas of acid mine drainage as well.
Approach: Revegetation of Superfund and non-Superfund areas will be undertaken to stabilize the sites and reduce wind and water erosion from the tailings. Previous research by these investigators and that of the Bureau of Mines has suggested that certain soil microorganisms, the mycorrhizal fungi, contribute significantly to and may be mandatory for survival and establishment of vegetation on minespoils. Both the ability of various vegetation regimes to limit surface water erosion and spread of heavy metal contamination, and the ability of these vegetation regimes to act as interceptor strips for contamination uphill from the vegetation strips will be studied in this project.
Status: A suitable site for the field experiment has been located northwest of the city offices in Galena, Kansas, and permission to conduct experiments has been granted by the city commission. Plots have been graded and barriers erected. Cattle manure has been used as an amendment in selected plots. Six treatments with four replications have been imposed on the 24 plots. Tall fescue was the species chosen for initial seeding. Treatments are an unamended control (not seeded), an amended control (not seeded), amended and seeded, amended and seeded and will receive benomyl (a fungicide), and 2 plots that were amended, seeded and inoculated with mycorrhizae, one of which will have trees planted in spring 1996. Soil samples were collected from each plot after manure was incorporated. A mulch and nylon mesh cover has been placed over all plots. Runoff measurements will begin in spring 1996. A surface transport model is being developed, and preliminary conceptualization of the model includes surface flow, sediment transport, and solute transport components. The influence of vegetation will be explicitly represented. This project is in its first year.
Clients/Users: This research will interest those in the mining industry, regulatory community, U.S. Environmental Protection Agency, and U.S. Department of Defense.
Key words: heavy metals, interceptor zones, mycorrhizal fungi, Superfund, vegetation.
Goal: The primary goal of this project is to design and develop a hydrometallurgical flow sheet to treat waste zinc residues containing iron and other heavy metal impurities such as lead and cadmium. The resulting flow sheet will be used at Big River Zinc Co., or any other industry desiring to treat similar wastes.
Rationale: A major problem faces the minerals industry in the form of huge tonnages of environmentally unacceptable zinc residues. Previously these oxidized dusts, which contain high iron and zinc contents with lead, cadmium, and other heavy metals, were precipitated in chemical forms acceptable for standard landfills. Under current laws, this practice will not be allowed and costs of compliance are expected to increase dramatically. In fact, it may even be necessary to re-process all the wastes that have been stored and accumulated over the years. The technical challenge is to develop metallurgical and chemical processes to treat these hazardous wastes in an economically viable manner. The most serious technical impediment preventing treatment of these wastes is the inability to separate the iron from the zinc. The investigator on this project has developed a process, galvanic stripping, to separate the iron from the zinc. As the next step, it is important to develop unique in-line processes specifically for handling diversity in feed stock, particularly when certain categories of impurities are present in low concentrations. Many existing processes are basically sound, but supplementary unit processes must be developed to make them more amenable to treat impure metal wastes and residues in an economic fashion.
Approach: This project will be conducted in conjunction with Big River Zinc Co., where the commercial plant to treat 50 tons per day residue will be located. In addition, two suppliers of the organic extractant and another zinc producer, Noranda Ltd., will also provide support and assistance. Ultimately, this technology will be transferred to others in the industrial sector for use in treating a variety of similar wastes generated in the mining and mineral community. Research will include the following three areas: evaluation of the process parameters to optimize the reduction of Fe+3 to Fe+2 in the D2EHPA organic phase; determination of the type of aqueous stripping solution and design procedure alternative to be used to separate and recover the Fe+2 and produce the best, salable iron product; and identification of the influence of the various heavy metal impurities in the solutions, their distribution (aqueous vs. organic) and effect on subsequent iron and zinc recovery.
Status: Research conducted to date has demonstrated that the galvanic stripping procedure is technically feasible. The process has been successfully demonstrated at a pilot and small plant scale level by Cominco, Ltd., in Canada. However, as with many complex reactions which are essentially under kinetic control, the operating parameters used have a major influence on the extent or efficiency of the process. In this case it is imperative to identify those factors which affect the reactions and attempt to quantify their sensitivity in changing the degree of iron removal if galvanic stripping is to be used on a large industrial scale. A number of parameters have now been identified which are capable of producing such changes and these include temperature, agitation, oxygen content, time, aqueous/organic (A/O) ratio, and pH of the aqueous strip solution. Each is important as an individual variable, but there are complex interactions among them as well, and these require clarification. Studies are now being made on the effect of these variables and the impact they may have on the economics of the industrial scale process. Based on the results obtained to date, the process continues to show promise as an alternative for treating waste zinc residues. One particularly encouraging feature has been the initial success obtained using high iron concentration stripping solutions. This would provide a technically and economically attractive outlet for the iron impurity. The current thought is to use the solution in water treatment applications where high iron and low zinc and other impurity concentrations are desirable. This project is in its first year.
Clients/Users: This research will interest those in the mining and metals industry, U.S. Department of Defense, and regulatory community.
Key words: heavy metals, extraction, flow sheet, galvanic stripping, zinc.
Goal: The purpose of this research is to demonstrate the effectiveness of air-sparged hydrocyclone (ASH) flotation technology in successfully recovering mineral values from tailings material through pilot plant testing with a 6-inch ASH.
Rationale: Mining activities have resulted in a number of abandoned tailing dumps and ponds containing significant amounts of metals such as cobalt, lead, zinc, copper, mercury, cadmium, gold, silver, etc. Recovery of mineral values from these tailing dumps and ponds and associated soil remediation by conventional technologies, though technically feasible, has several limitations. Low-grade and fine particle size of the material found at the tailing sites render recovery of the mineral values and removal of hazardous material highly inefficient and uneconomical. Also, due to the relatively low processing capacity of conventional equipment, significant investments in equipment and building floor space are required. In this regard, the ASH flotation technology may offer an excellent opportunity to minimize generation of hazardous mining and mineral processing wastes.
Approach: This project will investigate feasibility of the application of the air-sparged hydrocyclone flotation technology for treatment of hazardous mill tailings. Tailing sites located in Utah will be selected for the study. The research proposed includes plant surveying and sampling, physical and chemical characterization of mineral wastes, conducting testing, and optimization of the ASH removal efficiency. If the test program in laboratory scale experiments shows encouraging results, effort will be made to organize the next phase of the research program in order to conduct in situ tailings site testing of the proposed technology.
Status: Funding for this project began recently. A literature review has been conducted.
Clients/Users: Government agencies such as the National Science Foundation, U.S. Department of Energy, and U.S. Department of Defense are interested in this project. This project will also be of interest to those in the mineral and pulp/paper industry.
Key words: remediation, mill tailings, air-sparged hydrocyclone flotation, heavy metals.
Goals: Objectives are to develop a paired watershed research site sufficiently instrumented to develop a hydrologic, silt, and agricultural chemical movement database; to compile the watershed basin data in a form usable with existing EPA and USDA models to understand the impact of perennial tree buffers on the runoff water quantity and quality from "conventionally" farmed land; to install alternative perennial plant buffer designs to compare plant survival, biomass growth potential, sediment interception, subsurface nitrate movement in near-surface ground water, and herbicide movement from up-gradient application to the stream; to test equipment and tillage practices required by farmers to make this plant production practical; and to develop an education and technology exchange program to explain watershed-scale conservation and cropping concepts to agriculturists, farmers, media, and all ages of students.
Rationale: Tree-buffered riparian corridors can enhance sustainability of agricultural ecosystems and remove a portion of non-point source pollutants. They can provide a tree crop that does not compete with feed grains.
Approach: Two adjacent agricultural watersheds at Amana, Iowa, have been developed into a field research site, including the in-stream instrumentation required to measure flow and sample at desired intervals. One watershed stream is completely buffered using approximately 15,000 trees; the other watershed is unbuffered; annual tillage and cropping occurs up to the stream bank edge. Both watersheds are predominantly cropped with corn and soybeans; oats and hay are a small portion of the field area. Each watershed contains a portion of upland hardwoods.
Status: The concept of planting poplar trees as a perennial row-crop to manage field edges for reducing non-point source pollutants entering a first-order creek has been demonstrated to farmers, agribusiness, government officials, interested citizens, and the media. These watershed buffering concepts were shown to over 20,000 people during the 1993 Farm Progress Show. This demonstration has been called EPA's most successful technology transfer effort. Additionally, other field trips and press conferences have been held. Tours have been given to an agricultural attaché from Egypt, EPA research scientists from Athens Lab, and a press day has been held. A 12-minute video has been produced. In-stream water sampling stations have been monitored to measure water quality parameters. The nitrate nitrogen flow from an unbuffered watershed was consistently above the EPA MCL while the buffered watershed was consistently below the MCL. Ground water in the riparian stream border has been monitored for subsurface flows crossing the border. Tile drainage was the primary source of in-stream nitrate nitrogen. Little nitrate appeared to be added to the stream by base flow after the water flowed through the tree buffer. Buffer plots of grass and different tree varieties have been maintained to test alternative culturing practices. The Universal Soil Loss Equation was used to obtain estimates of relative soil loss potential in each watershed. This project has been completed.
Clients/Users: This research is of interest to those who are responsible for non-point source pollution control including regulators, farmers, and the USDA.
Key words: non-point pollution, poplar trees, pollution prevention, nitrate, atrazine.
Goals: Objectives are (1) year one--develop and refine analytical techniques required for identification of pesticide degradation products, develop and operate batch reactors under each of the four electron acceptor conditions, screen each reactor for major metabolic products, (2) year two--conduct kinetic experiments to quantify rates of formation and transformation of metabolic products and determine kinetic expressions to describe those reactions, obtain and analyze field samples from research site for metabolites, and (3) year three--complete kinetic experiments, and develop and test a mathematical model.
Rationale: Recent research has shown that while atrazine and alachlor are transformed in the environment under a variety of conditions, their rates of mineralization are likely much slower than their rates of initial transformation. Thus a number of degradation products are being formed and perhaps accumulating in the environment, and the nature of these products will likely be a function of the particular environment in which they are formed (e.g., the dominant electron acceptor condition). Therefore, it is desirable to gain information regarding the effect of these different environments on the formation and subsequent transformation of major degradation products.
Approach: Proposed research will employ both batch and column reactor techniques, some with soil-water suspensions. Soil obtained from an Iowa agricultural field known to have been treated in the past with atrazine and/or alachlor will be used. Liquid media used in all experiments will be a "synthetic" ground water designed to maintain one of the electron acceptor conditions of interest. All experimental reactors will be run at 16°C in an effort to keep experimental conditions as close as possible to those of a typical Iowa ground water. Reactors will be seeded with cultures which have been growing under desired electron acceptor conditions and have been shown to transform atrazine and alachlor. Acetate will be fed as a carbon and energy source. Pesticide, acetate, microbial biomass, and electron acceptors will be monitored over time during each experiment. Once a significant fraction of the fed pesticide has been transformed, products of atrazine and alachlor will be assayed in the effluents and/or soil samples of each reactor. Standards for some of the expected transformation products will be obtained. A number of analytical techniques will be employed for identification and quantification of these metabolic products, including use of selective GC detectors, GC-MS, or, if necessary, LC-MS. Unknown metabolites may be further analyzed using NMR spectroscopy.
Status: Initially, alachlor and atrazine disappeared in reactors maintained under all electron acceptor conditions, with the exception of aerobic. Resazurin, a color indicator of redox condition, was found to be involved in the transformation of alachlor and atrazine under denitrifying conditions. Second-order degradation coefficients for the biological transformation of alachlor and atrazine under denitrifying, methanogenic, and sulfate-reducing conditions were determined. Over the course of four experiments, the rate of alachlor transformation decreased considerably under methanogenic and sulfate-reducing conditions. Several metabolites of alachlor were positively identified in these systems. Under denitrifying conditions with organisms and resazurin present, aniline, m-xylene, acetyl alachlor, and diethyl aniline were positively identified as products of alachlor degradation. No metabolite accounted for greater than 35% of the initial mass of alachlor. m-Xylene was also detected in an abiotic reactor containing only resazurin, atrazine, and alachlor in ground water medium under denitrifying conditions. Because this compound is readily degradable, it is unlikely that m-xylene would persist in aerobic ground water as a result of alachlor contamination and subsequent transformation. Experiments indicated that resazurin may serve as an electron donor for organism growth, but it was unclear whether resazurin itself, or organisms capable of growth on resazurin, were responsible for the formation of metabolites. It is also possible that resazurin facilitated electron transfer, as vitamin B12 is known to do, under abiotic conditions. In the methanogenic and sulfate-reducing reactors, diethyl aniline, acetyl alachlor, and an unidentified metabolite (called SM4 for the purposes of reporting) were detected. No metabolite accounted for greater than 30% of the initial mass of alachlor. Acetyl alachlor was an expected product, likely formed as a result of reductive dechlorination. Some toxicity was noted during the course of the experiments, possibly the result of accumulation of unidentified metabolites, SM1, SM2, and SM4. Batch experiments were run on methanogenic and sulfate-reducing reactors using acetyl alachlor. Acetyl alachlor was never detected in the sulfate-reducing reactor after the initial dosing, due either to poor dosing technique or immediate abiotic transformation by sulfide/bisulfide ions present in the reactor. Acetyl alachlor was detected and monitored in the methanogenic reactor. Diethyl aniline and aniline were expected metabolites, though aniline and an unidentified compound were the only two transformation products identified by gas chromatography. No transformation products of atrazine were identified under any of the conditions investigated. Since atrazine disappearance was measured in the denitrifying, methanogenic and sulfate-reducing systems, and complete mineralization to carbon dioxide and water was very unlikely, metabolites should have been formed in these reactors. It is likely, however, that the extraction method used did not capture polar transformation products. This project has received its third and final year of funding, but some work is continuing.
Clients/Users: This research is of interest to those who are responsible for non-point source pollution control including regulators, farmers, and U.S. Department of Agriculture.
Key words: atrazine, alachlor, transformation products, kinetics.
Goals: Objectives include (1) investigation of NAPL entrapment; (2) mobilization of entrapped NAPL; (3) modeling of interphase mass transfer; (4) development of numerical models; (5) generation of data in soil flumes for model validation; and (6) field validation.
Rationale: Existing models of transport and entrapment behavior of nonaqueous phase organic chemicals based on traditional petroleum engineering formulations are inadequate for situations dealing with complex soils and chemical types found at wastes sites.
Approach: The proposed approach involves continuation of laboratory investigations with more realistic soil types and chemicals which are of relevance to waste problems in EPA Regions VII and VIII. Model development efforts will be continued, guided by the qualitative results of the fundamental processes and data generated in the laboratory investigations. Issues related to micro- and macro-scale entrapment, preferential flow, mobilization, and mass transfer between phases will be investigated further to develop realistic and accurate models. A radically new approach in which the core of the model becomes the available data will be utilized in the transport model development. Basic to this approach is that the models will be driven by the data rather than by a sophisticated numerical algorithm as in existing numerical models. The developed model will then be verified in the laboratory. The developed models will be used to conduct transport simulations to perform a retrospective performance analysis of a field treatment system. A waste site in Region VIII is being used to conduct this case study and field demonstration.
Status: Entrapment and mobilization experiments have been performed. Results of experiments on macro-scale entrapment in sandy soil demonstrated that preferential flow and macro-scale entrapment are not controlled by properties of a "mixing layer" at the coarse/fine interface. It is believed that these phenomena are dependent solely on the displacement pressure of the fine soil. NAPL mobilization experiments were conducted in a soil column where saturated zone entrapment was established using coarse sand layers embedded in a fine sand matrix. Possible mobilization by changing the water and NAPL fluid pressures which may result during water flooding and water table fluctuations were investigated. An experimental program was developed to investigate macro-scale retention of NAPL in the vadose zone. The experiment showed that macro-scale retention can be observed in a layered system and that it is semi-permanent (high saturations of NAPL found in the fine sand on top of the coarse sand did not decrease measurably in more than a month). Comparison with static pressure distribution profiles for capillary pressure and saturation show that the experimentally-found high saturations cannot be explained under assumption of a static pressure distribution. Thus it can be concluded that macro-scale retention is controlled by a dynamic process, or more specifically, by the minimum hydraulic conductivity in a soil profile. Modeling of flow and transport processes through fractures in soil formations was performed. Dissolution of trapped fluids has also been studied. Development and laboratory validation of numerical models are ongoing. The third year of this project has been completed.
Clients/Users: This research is partially supported through the Robert S. Kerr Environmental Research Laboratory. Other researchers, regulatory personnel, responsible parties, and private contractors have expressed interest in this research.
Key words: organic compounds, nonaqueous phase liquids, models, remediation.
Goal: The objective is to develop knowledge leading to improved methods of quantifying remediation processes for contaminated soil where a hydrocarbon-rich phase is present.
Rationale: Oil-rich phases are found in a variety of contaminated sites including locations of oil and gas exploration or drilling, coal-gas plants, leaking tanks, wood treating, and oil refining. Mathematical models of the remediation process should include composition and geometry of the hydrocarbon phase. Phenomena occurring in the vicinity of or on the hydrocarbon surface may be rate limiting.
Approach: Models will be developed for remediation of a single hydrocarbon deposit through bioremediation, diffusion of the hydrocarbon contaminant through water (pump-and-treat), and volatilization of the contaminant (vacuum extraction). This approach is based on the expectation that phenomena occurring in the vicinity or on the surface of the hydrocarbon deposit may be rate limiting, thereby determining the required remediation time.
Status: Research has shown that for both bioremediation and pump-and-treat models, aggregate and NAPL blob sizes have the greatest impact on remediation time, which has been found to be proportional to the square of the characteristic length. Other primary rate-controlling factors are NAPL solubility and diffusivity of the contaminant relative to that of oxygen. Contaminant dissolution is rapid compared to oxygen transfer in the saturated zone for more soluble compounds such as benzene than for less soluble compounds. For slightly soluble compounds such as phenanthrene, oxygen transfer is rapid compared to dissolution. Thus, for phenanthrene, microbial growth at the NAPL interface is expected. A simple equilibrium model has been used to examine bioremediation enhanced pump-and-treat remediation in the saturated zone. Dissolution, sorption, and biodegradation are included in the model. Studies with an advective flow model indicate that the NAPL dissolution rate may be an important factor for some extractive remedies. The third year of this project has been completed; however, work is continuing.
Clients/Users: This research is of interest to other researchers, contractors, and responsible parties.
Key words: organic phase, modeling, bioremediation, simulation.
Goal: The primary objective of this project is to determine the role of herbicide-tolerant plants and commodity plants in facilitating microbial degradation of herbicide wastes in soils. This information can then be used in defining the potential role of vegetation, under specific types of chemical contamination (herbicides, insecticides, industrial chemicals) in the bioremediation process.
Rationale: With the increase in pesticide usage since the early 1950s has come a rapid growth in the numbers of agrochemical dealerships. Unfortunately, many of these dealerships have, through normal operating procedures, contaminated the soil and water at these sites, creating one of the most ominous issues facing the agrochemical industry. The expense of most of the current technologies for cleanup of contaminated soil and water preclude their use at agrochemical dealership sites. Biological restoration of contaminated surface soils using indigenous microbial populations is potentially an effective remediation strategy, provided that a sufficient consortium of microorganisms capable of degrading contaminants are present, and that their activity is not limited by existing environmental conditions. Environmental conditions can be altered to enhance microbial populations and/or their activity, such as through nutrient additions or aeration.
Approach: Experimental procedures will utilize pesticides from different chemical classes and with different properties as model compounds in studies to identify critical environmental and biological variables affecting rate of degradation in the root zone. Experiments will be carried out using soils and plants collected from a pesticide-contaminated site in Iowa. An initial sampling trip to the site was used to document type and percent cover of vegetation as well as to collect soil and vegetation samples from the site. Initial studies in the laboratory have developed suitable extraction and analysis techniques for quantifying pesticide wastes in soils. Experiments on influence of vegetation on microbial degradation of pesticides were conducted utilizing sterile, nonvegetated, and rhizosphere scenarios in an environmental chamber. Results of these preliminary tests indicated enhanced degradation of atrazine, metolachlor, and trifluralin in the rhizosphere of Kochia sp., an herbicide-tolerant plant compared with nonvegetated soils and sterile control soils. In addition, Kochia sp. seedlings have emerged from rhizosphere soils spiked with additional concentrations of the three test chemicals, indicating the ability of these plants to survive in soils containing high concentrations of herbicide mixtures. In addition, radiotracer experiments will be conducted to provide further evidence for biodegradation of pesticides in root zones of plants from contaminated sites, as well as allow for mass balance calculations. Finally, small-scale field trials will be conducted.
Status: An appropriate study site was located and permission was obtained. The study site is an active agrochemical dealership in central Iowa. The site was characterized with respect to (1) soil physicochemical properties, (2) vegetation, and (3) presence and distribution of pesticide contaminants. Several candidate plant species for use in the study were identified, and rhizosphere soils from these plants were collected. Nonvegetated soil samples were also collected for use in pesticide degradation experiments. Greenhouse studies have focused on the ability of candidate plant species to germinate and survive in soil contaminated with pesticides (individual compounds and mixtures). Plant germination and survival is a critical variable affecting use of plants in remediating pesticide-contaminated sites. Tests have been conducted with commercially available seeds, as well as seeds collected in the field. In addition, herbicide-resistant plant seeds have also been included in these studies because of their ability to tolerate certain classes of herbicides. In addition to plant toxicity tests, investigators are also conducting microbial toxicity tests in order to determine if high concentrations of pesticide mixtures found at these contaminated sites are inhibiting microbial growth and activity as indicated by respiration rates of incubated soil samples. Initial screening tests on mineralization of 14C-labeled atrazine identified rhizosphere soil from Kochia scoparia as having enhanced degradative capability. In subsequent tests, it was concluded that Kochia scoparia rhizospheric soil had a significantly greater rate of 14C-atrazine mineralization than nonvegetated soil and sterile control soil. This project is in its first year.
Clients/Users: This research will interest agrochemical dealerships, for heavy metal contaminated sites; to determine effects of poplar tree cultivar on survivability and growth when deep-planted at a heavy metal contaminated site; to investigate effects of soil amendments on poplar tree survival and growth; to determine heavy metal concentrations in poplar leaves, roots, and wood when grown in a heavy metal contaminated environment; to investigate optimum depth of soil cover for establishment of a perennial grass cover; and to extend a current mathematical model that simulconsulting and remediation companies, and federal agencies such as U.S. Department of Defense.
Key words: vegetation, bioremediation, pesticides, agrochemicals, rhizosphere.
Goal: The overall objective of this research is to evaluate the effectiveness of solvent-mediated mobilization and photodegradation of chlorinated dioxins and furans as a means of soil decontamination. In order to meet this objective, a series of laboratory and field experiments have been planned.
Rationale: Many sites in the United States and abroad have become contaminated with polychlorinated dibenzodioxins and related polychlorinated aromatics, either as a result of accident or industrial activities. The only proven technology for decontaminating the soil at such sites is high-temperature incineration, which is extremely expensive. Destruction of dioxins and furans by natural or artificial sunlight is known to occur and has been shown to be highly efficient under certain conditions in the laboratory. This process, photodegradation, has not been regarded as promising for decontamination of soil, however, due to the sharp attenuation of light beyond a fraction of a millimeter in soil. If the substances to be photodegraded could be brought to the soil surface, the efficiency of the process could be dramatically improved and might provide an option less expensive than incineration.
Approach: Experiments will be conducted to study the following: (1) partition behavior of hepta and octachloro dibenzo-p-dioxins in soil and solvent systems which are environmentally acceptable and amenable to photodegradation. Emphasis will be placed on use of complexing agents such as sulfoxides; (2) effects of co-contaminants on dechlorination mechanisms of polychlorinated dibenzo-p-dioxins (PCDDs); (3) photodegradation rate of chlorinated dioxins and furans in suitable solvent systems; (4) quenching effect of co-contaminants on photodegradation; and (5) optimization of carbon adsorption/regeneration for recycling of solvents. Field trials will evaluate the efficacy of an optimized mobilization-photodegradation process on a pilot scale at contaminated sites in California and Missouri.
Status: Partition experiments have been carried out to study distribution of dioxins in soils and selected solvent systems. Solution phase photodegradation experiments have been carried out under natural and simulated sunlight conditions. Phototransformation rates were highest when both heterogeneous and homogeneous photocatalysts were used simultaneously. Experiments to monitor degradation of PCDDs which might escape into the atmosphere revealed no measurable release of PCDDs; however, this is still being monitored. Irradiation experiments revealed that different dioxin congeners degrade at different rates. The data revealed an inverse relationship between degree of chlorination and rate of disappearance. The data also indicated that more toxic laterally substituted congeners degrade at a slower rate than peri substituted congeners, in contrast to degradation observed in the solution phase. Field experiments have been initiated in California. Studies in the area of chemical dehalogenation have resulted in development of an innovative chemical dehalogenation process designated "CDP." Work with counterflow oxidative regeneration showed that photodegradation and chemical dehalogenation processes are efficient in degrading organic wood preservation chemicals. However, use of the processes over long periods can lead to build-up of residual contaminants and reaction byproducts. To maintain high extraction efficiency, these byproducts and constituents must be removed. Removal can be achieved through adsorption. This project is in its final year.
Clients/Users: Results of this project will be of interest to those in wood-treatment and agriculture industries, as well as to government agencies such as U.S. Environmental Protection Agency and U.S. Department of Defense.
Key words: photodegradation, mobilization, polychlorinated dibenzo-p-dioxins, furans, soil.
Goal: The goal of this project is to develop a slurry biotreatment process for soils contaminated with Pentachlorophenol (PCP) and creosote.
Rationale: PCP and creosote polyaromatic hydrocarbons (PAHs) are found in most contaminated soils at wood-treatment sites. Treatment methods currently being used for such soils include soil washing, incineration, and biotreatment. Soil washing involves removal of hazardous chemicals from soils using solvents, but the solvent stream must still be treated for destruction of contaminants. Incineration is an effective tool for destruction of contaminants but is costly and lacks public acceptance. Bioremediation has been considered and used for treatment of soils contaminated with wood-treatment chemicals, but bioremediation leaves the most toxic, carcinogenic, and regulated chemicals in the soil. Slurry-phase biotreatment of contaminated soils and sediments is an innovative treatment technology. Its advantages include easy manipulation of physicochemical variables and operating conditions to enhance rates of biodegradation and ease of containment of exhaust gases and effluent. Bioslurry technology is currently hampered by some bottlenecks that need to be relieved.
Approach: Engineering and process development aspects of bioslurry treatment of PCP- and creosote-contaminated soils from a Superfund site will be studied in this project in shake flasks and in 14-liter well-instrumented fermentors. Use of surfactants and cosolvents will be explored in order to enhance aqueous solubility of hydrophobic and sparingly soluble contaminants. The effect of cosolvents on microbial activity will be studied. Kinetic studies for biodegradation of PCP and PAHs will be carried out in sealed bioreactors so that accurate material balances can be taken. Experiments are planned to investigate the role of surfactant/cosolvent, temperature, carbon source, and oxygen delivery by sparging of pure oxygen in reduction of concentrations of PAHs and PCP in the contaminated soil slurry. Reactors with power measurement devices will be used to investigate several different types of mechanical agitators in order to keep the solids in suspension. The power requirement under aerated and unaerated conditions will be correlated with geometrical and system parameters such as particle size, nature of soil, solid density, and physical dimensions in the reactor. Oxygen transfer rate and oxygen transfer efficiency in the slurries with sufficient power input for minimal and complete suspension will also be studied in this reactor. All of the information will be used to develop a flow diagram of the bioslurry treatment process for cleanup of contaminated sites and to generate cost data that may be used to determine cost effectiveness of this process for field-scale treatment.
Status: Start-up activities have been completed. These include collection of contaminated and uncontaminated soils, procurement of agitators, assembly of set-up, and development of experimental protocols for the first phase of study. Studies of solubility enhancement, measurements of surfactants' adsorption equilibria in different soils, and mixing studies are currently being conducted. Procedures for analysis of surfactant concentrations are being standardized and will be followed by measurements of adsorption equilibrium isotherms in soil suspensions. PAH-solubility enhancements will be conducted mostly with contaminated soil and will be related to soil-characteristics, PAH partition coefficients, and surfactant adsorption isotherms. Measurements of power number versus Reynold number for the different impellers in soil-free systems are being conducted with and without aeration; these will be followed by measurements in different soil slurries. Rheology of soil slurries is also being measured. This project is in its first year.
Clients/Users: This project will interest those in the wood-treatment industry and federal agencies such as U.S. Environmental Protection Agency and U.S. Department of Defense.
Key words: soil, PCP, creosote, slurry bioreactor, wood treatment.
Goal: This project will address the possibility of using sodium salts of organic acids from 2 carbons to 10 carbons in length to support dehalogenation of chlorinated hydrocarbons.
Rationale: Previous work has demonstrated anaerobic biotransformation of chlorinated solvents both in laboratory settings and in field demonstrations. However, there has been no investigation of the addition of organic electron donors to both increase solubility and to act as the electron donor for dehalogenation. Also, there is no clear delineation of the upper concentrations at which reductive dechlorination is possible. This study will provide information regarding the potential for use of medium length fatty acids for bioremediation of chloroethenes. Applications of these results could facilitate development of technologies for in situ bioremediation of dense nonaqueous phase liquid (DNAPL) contaminated aquifers.
Approach: The project will consist of four phases: (1) evaluating different concentrations of the sodium salt of each acid on the solubility and diffusion rate of tetrachloroethene (PCE) and trichloroethene (TCE) into water; (2) delineating the concentrations of each acid which can support dehalogenation of PCE or TCE in slurries made using aquifer solids from an anaerobic zone in chloroethene-contaminated aquifer and site ground water; (3) determining the microbial community tolerance to high levels of PCE or TCE; and (4) modeling of the predicted movement of selected chloroethene, added electron donor, acetic acid, and partially dechlorinated chloroethene intermediates which are formed in the aquifer.
Status: Start-up activities for this project have been initiated. Eight surfactants have been selected for evaluation of the effect of their presence on PCE dechlorination. Polyoxyethylene ethers to be used are 10 Lauryl Ether, 10 Cetyl Ether, 10 Stearyl Ether, 10 Oleyl Ether, 20 Cetyl Ether, 20 Stearyl Ether, 20 Oleyl Ether, and 23 Lauryl Ether. Initial microcosms have been started to screen site material for the potential of the indigenous organisms to anaerobically degrade the surfactants in question at 1 mM concentrations. The R.S. Kerr Environmental Research Lab has been invited to collaborate on the project. This project is in its first year.
Clients/Users: This project will be of interest to other researchers and federal agencies.
Key words: organic acids, bioremediation, dense nonaqueous phase liquids, aquifers.
Goal: This research will investigate the hypothesis that both microbial and abiotic processes contribute to reductive dechlorination of xenobiotics in methanogenic incubations with elemental metals, such as iron, serving as an ultimate electron donor.
Rationale: Polychlorinated compounds such as carbon tetrachloride (CT) are known to be transformed via sequential reductive dechlorination by both abiotic and microbial mechanisms under aerobic conditions. However, existing treatment processes which utilize reductive dechlorination suffer from several drawbacks including inefficient transfer of electrons from the ultimate electron donor to the chlorinated compound and slow rates of reaction, thereby resulting in possible accumulation of transformation products of equal or even greater toxicity. Elemental metals in aqueous solution can act as an energy source for methanogens via production of hydrogen. Reductive dechlorination of chlorinated compounds could then proceed by three mechanisms: (1) abiotic processes whereby electrons are transferred directly from the elemental metal to the chlorinated compound, (2) microbial processes whereby electrons from H2 that are involved in biosynthetic processes are diverted to the chlorinated compound, and (3) microbial-catalyzed abiotic processes whereby electrons from the elemental metal are transferred to the chlorinated compound via biological electron carriers.
Approach: Experiments will be conducted in batch and column-reactor systems. Initial studies will investigate iron and carbon tetrachloride (CT). Other metals, such as aluminum, tin, and zinc will be used in later studies. Various chlorinated organics will also be assayed. A hydrogen-utilizing, mixed, methanogenic culture will be developed as an inoculum source for all experiments. Initial batch studies will be performed to determine the general time-course that the reactions will follow. Inhibition studies using 2-bromoethanesulfonate (BES), a specific methanogenic inhibitor, will address the role of methanogens. Analytes to be measured in headspace gas samples include CT, chloroform (CF), dichloromethane (DCM), chloromethane (CM), hydrogen, and methane. Subsequent, detailed, batch kinetic studies will be performed and, where appropriate, analytes will include ferrous iron, total soluble iron, CT, CF, DCM, CM, hydrogen, methane, and oxidation-reduction potential. The stoichiometry and kinetics of all pertinent reactions will be determined. Electron balances will be conducted to provide insight into important abiotic and biotic processes. Flow-through column experiments using adjustable-bed-length, glass chromatographic columns packed with steel wool will be conducted to simulate long-term in situ treatment and to validate the kinetics determined in batch studies. A one-dimensional, finite-difference, numerical model will be developed to simulate the performance of the column reactors. The model will include advection, dispersion, and sorption, and the appropriate degradation kinetics as determined from batch experiments.
Status: Initial experiments with carbon tetrachloride (CT), chloroform (CF), iron, and hydrogen have been performed. Column reactors have been constructed and have been seeded with anaerobic bacteria. Aqueous-phase CT was rapidly dechlorinated in anoxic treatments containing Fe0 powder. Investigators found that deoxygenation is not a prerequisite for treatment of CT-contaminated water with Fe0. Recent work investigating the role of oxygen in Fe0/CT systems indicates DO may be beneficial in controlling product formation. The amount of CT transformed to CF under initially toxic conditions was less than the amount transformed under anoxic conditions, indicating the operation of an alternative reaction pathway involving molecular oxygen. These results show that the dechlorination pathway(s) for CT may be controlled to a certain extent by dissolved molecular oxygen, resulting in the formation of a higher proportion of innocuous products (e.g., chloride ion and carbon dioxide) compared to the reductive dechlorination products (chloroform and methylene chloride) which are both increasingly recalcitrant under anoxic conditions and are toxic. In mixed culture experiments, the following treatments were investigated: (1) iron and live cells, (2) iron and cell-free methanogenic supernatant, or (3) live cells. This project is in its first year.
Clients/Users: This research will be of interest to other researchers and to U.S. Department of Defense.
Key words: dechlorination, xenobiotics, heavy metals, iron.
Goal: The goal of this project is to advance understanding of anaerobic and mixed-electron acceptor bioremediation of chlorinated aliphatics to a level that full-scale evaluation of these processes is possible. If successful, field-scale evaluation of technologies developed in this research will be pursued.
Rationale: The U.S. EPA Hazardous Substance Research Centers and national agencies such as the Department of Defense and Department of Energy have identified research on remediation processes for chlorinated aliphatic-contaminated subsurfaces as a high priority. A promising technique is use of in situ bioremediation, and full-scale evaluations of this process are ongoing at trichloroethene-contaminated sites. All of these efforts have focused on use of aerobic bacteria, particularly methanotrophs. However, several of the chlorinated aliphatics of greatest concern are not degraded by aerobic bacteria. Unlike aerobic biological processes, anaerobic biotransformations of all chlorinated aliphatics occur. This lack of specificity, coupled with the fact that most contaminated aquifers are anaerobic, may make anaerobic bioremediation an alternative or supplement to aerobic processes.
Approach: This research will focus on three chlorinated aliphatics that are not degraded by aerobic bacteria: perchloroethene, 1,1,1-trichloroethane, and carbon tetrachloride. If successful, field-scale evaluation of technologies developed in this research will be pursued. In order to accurately assess potential for anaerobic or combined electron acceptor bioremediation technology, all experimental systems will be operated under conditions similar to those observed in contaminated aquifers. Additionally, soil cores will be obtained from contaminated sites as a source of organisms that are indigenous to contaminated areas. These cultures may be considerably different than those obtained from anaerobic digesters and may contain organisms particularly suited for chlorinated aliphatic degradation.
Status: The scope of this project may need to be scaled back because some expected funding was not secured. Operational equipment which is necessary to the project is being updated. A new GC column which will allow separation of all parent compounds and all expected, volatile chlorinated metabolites has been purchased. Methanogenic enrichment cultures are well established and methanotrophic enrichments have begun. Column reactors have been constructed and seeded except for methanotrophic columns. Kinetic experiments will commence as soon as the GC has been calibrated and a detailed quality assurance/quality control plan developed. The anaerobic columns to be used in the sequential studies have been developed; methanotrophic columns will be seeded as soon as the methanotrophic enrichment culture has reached quasi-steady-state. This project is in its first year.
Clients/Users: Results from this research will be of interest to other researchers, U.S. Environmental Protection Agency, U.S. Department of Defense, U.S. Department of Energy, and others.
Key words: anaerobic, bioremediation, chlorinated aliphatics, mixed-electron acceptor.
Goal: The goal of this project is to develop a bench-scale, fluidized-bed bioreactor (FBBR) to degrade TCE in extracted ground water. This study of FBBRs is expected to yield the high performance necessary for pilot or field testing.
Rationale: Our knowledge of organic contaminant biodegradation has advanced from fundamental biochemical/microbiological studies to a stage of active treatment process development. Trichloroethene (TCE), once considered to be nonbiodegradable, can be cometabolized by microorganisms with oxygenase enzymes. The phenol-degrading organisms selected for this work readily form cohesive biofilms, which is a prerequisite for their use in biofilm reactors such as the fluidized-bed bioreactor (FBBR). Development of FBBRs for cometabolizing trace contaminants in extracted ground water is attractive because they are compact, relatively simple to operate, and their use is widespread in several industries. Biological oxidation of TCE should be less costly than advanced chemical oxidation techniques that use combinations of ultraviolet light, ozone, and hydrogen peroxide. Ongoing research with bioreactors continues to yield improvements in performance as better operating strategies and configurations are tested. Studies with FBBRs which will be conducted under this project are expected to yield the high performance necessary for pilot or field testing.
Approach: A mixed-culture of phenol-utilizing microorganisms enriched from domestic wastewater will be grown on sand to form bioparticles in a bench-scale FBBR. Reactor inlet conditions will be varied and TCE removal will be measured. Concentrations of phenol, oxygen, and TCE will be determined at various points in the reactor to select inlet conditions or design variations that improve TCE removal. Several sizes and types of sand will be evaluated to increase biomass hold-up and control biomass thickness. Facilitating spatial sequencing of bioparticles between growth and degradation zones will be an important factor in designing high performance FBBRs. High and low dispersion conditions in the reactor will be obtained by modifying the reactor inlet distributor. Periodic pulsing of phenol will be used in some experiments to increase TCE removal by temporal sequencing of substrates. A draft tube reactor will allow greater control over internal sequencing (via circulation) of bioparticles between phenol and TCE degradation. Performance of this innovative reactor type will be characterized in the same manner as the conventional type of FBBR.
Status: Culture isolation experiments verified that the culture cometabolizes TCE and that presence of phenol inhibits TCE cometabolism. A laboratory-scale conventional fluidized-bed reactor has been constructed. In TCE-loss rate studies, it was determined that only a small, inconsequential amount of TCE is lost in the continuous-flow TCE treatment reactor. A downflow bubble contacting aerator has been selected as the oxygen transfer device. This aerator may have large-scale advantages because it could be modified to redissolve all FBBR effluent off-gases into the FBBR influent. Fluidization rates of quartz, garnet, ilmenite, magnetite, and hematite filter sands have been determined in the FBBR. These studies provided information on sand density and expanded-bed porosity as a function of flow rate. Mixing and conductivity tracer studies have been conducted, and, generally, circulation was greater than expected and so the inlet distributor has been redesigned to reduce circulation. Dispersion numbers for the reactor are presently being determined. Preliminary experiments on growth of bioparticles in the FBBR showed that the phenol-utilizing culture grows rapidly and readily adheres to the sand. Size of bioparticles increased towards the top of the bed. Growth of bioparticles was vigorous and on one occasion recirculation pumps were damaged by bed overflow and carryover of bioparticles and sand through the aerator. As a result, investigators have made design modifications, adding a shearing pump that continuously withdraws bioparticles from the top of the bed, shears the biofilm from the sand, and introduces the sheared mixture at the reactor inlet. When the bed reached the desired height, TCE was introduced to the FBBR. TCE removal was not steady. Generally, these preliminary experiments indicated that phenol loading rate and TCE loading rate both affect TCE removal. Toxicity is an important factor because of the high rate of TCE degradation. Balancing opposing effects of phenol delivery to offset toxicity while avoiding excessive competition will continue to be challenging. This project is in its first year.
Clients/Users: This project will be of interest to other researchers, U.S. Department of Defense, and others.
Key words: trichloroethene, cometabolism, fluidized-bed bioreactors, chlorinated solvents, water.
Goal: The goal of this research is to determine feasibility and efficacy of vegetative bioremediation, specifically poplar trees, at sites contaminated with benzene, ethylbenzene, toluene, and xylene (BETX) compounds.
Rationale: Vegetative remediation has become a promising, inexpensive, publicly accepted, and innovative technique for cleaning contaminated hazardous waste sites. This technique is best suited for sites of shallow contamination that are in the zone of impact for deep-rooted poplar trees. BETX contamination is ideally suited for vegetative remediation. Being light nonaqueous phase liquid (LNAPL) contaminants, BETX compounds are often located near the surface at hazardous waste sites. BETX contamination is also ubiquitous in today's environment, and many of these sites are located at rural and abandoned sites where little money is available for more expensive traditional remediation techniques.
Approach: This research will attempt to determine whether vegetative remediation with poplar trees is a fundamental approach for remediation of BETX-contaminated sites. Poplar uptake of BETX compounds will be monitored and translocation within plant tissues will be studied. Plant tissues and aerial compartments will be examined to measure accumulation in plant tissues and volatilization from leaf surfaces, respectively. Poplars are widely adapted to a wide variety of temperate and boreal environments; they are fast growing, hardy, and easily reproduced from parental cuttings; they are easily rooted at variable and great depths; and they have been successfully grown from tissue cultures.
Status: Analytical techniques have centered on methods to measure low levels of 14C-labeled compounds and metabolites stored in poplar tissues, in aqueous and soil samples, and in headspace compartments. Combustion of poplar tissues, utilizing a biological oxidizer, with Liquid Scintillation Counting techniques has been shown to measure labeled benzene and possible metabolites. Techniques for HPLC analysis of aqueous samples and extracted solid phase samples are also under development. Analytical techniques have also been developed for GC/MS analysis of aromatics including biphenyl, chlorinated biphenyls, halogenated toluenes, and resulting metabolic products. Positive identification of suspected intermediate compounds was achieved utilizing ITD mass spectrometry. Concentrations of identified compounds were verified via HPLC analysis. Bioreactors have been designed to contain individual poplar trees. These reactors have proven to perform as expected in the laboratory setting. This project is in its first year.
Clients/Users: This research is of interest to the city of Houston, Texas, which has a petrochemical spill site. It will also be of interest to U.S. Department of Defense and for petrochemical "land farming" sites, U.S. Department of Energy sites, and agricultural locations.
Key words: vegetative remediation, poplar trees, BETX, soil, plants.
Goals: Objectives of this project are to develop experimental systems to improve oxygen availability for enhanced aerobic biodegradation; monitor transfer of contaminants through plants; apply a mathematical model to describe fate of water, contaminant, root exudates, plants, microbes, and oxygen in laboratory and field systems; and work with professionals elsewhere to apply this technology to one or more field sites.
Rationale: Much of the population in U.S. EPA Regions VII and VIII rely on ground water for its potable water, but many ground water aquifers within this region have been contaminated with hazardous organic chemicals. Such chemicals may be by-products of agricultural and industrial production or may have leaked from fuel storage tanks or ruptured soil liners at disposal sites. Soil contamination involved in these types of problems is often very dispersed so that conventional soil and ground water remediation techniques would be very expensive or, in some cases, impractical. Plants can play an important role in remediating soil and ground water contaminated with organic substances. To put this new technology to effective use, we need to better understand and predict effects that plants have on soil and ground water remediation, so that effective planting and management plans can be developed.
Approach: Previously a prototype system has been built by these researchers and used for study of bioremediation of ground water assisted by plants. Based on experience with the prototype system, a new system has been constructed with more but shorter path length channels and a depth of 60 cm. It will permit introduction of controlled amounts of air into the soil, either above or below the water table, in two of the channels. By use of evolutionary operation design, performance of the system will be optimized to minimize air input and maximize degradation of target substances. Material balance measures will be used to determine the fate of target substances. Potential intermedia transfer will be monitored by FTIR measurements on the gas phase above the growing plants, while changes in contaminant concentration in the ground water will be monitored by headspace gas chromatography or FT-IR of aqueous samples. The ground water flow and transport model will be used to model behavior of contaminants in the new system under several experimental conditions. The model will be further refined to improve the fit of predicted and observed behavior. It will then be applied to field situations where monitoring wells are in place, such as near landfills.
Status: A chamber system has been constructed. Water flow has been established in this system. It will be planted soon with field grown alfalfa from the site of initial soil collection. Microcosms prepared with soil from the prototype chamber have been monitored. These show degradation of trichloroethylene to a range of intermediates and products including dichloroethylenes, vinyl chloride, chloroethane, ethane, methane, and carbon dioxide. Microorganisms that are able to grow in the presence of toluene and/or trichloroethylene with no additional carbon source added to the solid medium have been isolated. Extensive studies have been conducted to measure movement of a range of compounds through plants from ground water to the atmosphere. Alfalfa was used as a follow-up to the chamber studies; salt cedar was chosen as an extreme phreatophyte; and a cultivar of poplar was used. Considerable success has been obtained in using the previously described model to simulate expected distributions of reactants and products through the prototype chamber under steady state conditions. Recent studies with burettes placed to various depths in the prototype chamber have indicated the importance of soil diffusional characteristics in movement of contaminants. Investigators have met with Riley County engineering staff to assist them in developing plans for control of leaching at the recently closed Riley County landfill. This project is in its first year.
Clients/Users: Contractors, regulators, professionals with manufacturing companies and government agencies, and researchers have expressed interest in this research. Riley County Public Works officials have also expressed interest in using this technology at the Riley County landfill. This research is also of interest to U.S. Department of Defense and U.S. Department of Energy.
Key words: plants, soil, ground water, alfalfa, poplar trees.
Goal: The primary goal of this research is to develop and implement systematic procedures for applying, in the field, treatment and remediation technologies that have been developed in the laboratories, taking into consideration the complexities which are encountered in the field.
Rationale: The primary hypothesis is that natural heterogeneities of soil and heterogeneities due to nonaqueous phase liquid (NAPL) entrapment result in preferential flow of water and treating agents. These constraints to flow and delivery of treating agents alter effectiveness of treatment schemes in the field. This research will attempt to identify the basic processes that are affected by these complexities and determine the parameters that control the behavior at the field scale.
Approach: A systematic procedure to extend to the field the knowledge gained through experimentation at the laboratory scales of pore, cell, column, and soil flumes will be developed. Laboratory, modeling, and field investigations will focus on issues related to transport, entrapment, recovery, dissolution, fingering, and physical chemical and thermal mobilization, blob dispersion to increase dissolution, etc., that are of fundamental importance in developing remediation technologies. Laboratory experiments in cells, columns, and large tanks will be continued to identify basic parameters which need to be up-scaled to field problems. Some of the parameters that have been identified for study include hydraulic conductivity, capillary pressure versus saturation, relative permeability, entry pressure, pore size distribution, dispersivity, sorption coefficient, mass transfer coefficients, and dissolution parameters. Investigators will use chemical mixtures to look at multicomponent mass transfer and realistic field soils. Sites in Kansas, Colorado, Wyoming, and Louisiana will be selected for field studies. Once effective parameters are identified, techniques will be developed to obtain these in the field.
Status: Focus has been on the processes of entrapment, fingering, vapor flow, dissolution, and enhanced dissolution using surfactants. Preliminary test simulations conducted in large pilot scale tanks suggest the critical role played by soil heterogeneities in entrapment and dissolution behavior of NAPLs. A set of experiments were conducted in large soil tanks to understand the mechanisms of spreading and to quantify distribution of NAPLs in fields of randomly packed soil heterogeneities that are more representative of field conditions. Experiments with light NAPL in the vadose zone and a dense NAPL in the saturated zone were conducted. Experimental results show that spreading is controlled by initial water saturations, capillary barrier effects, preferential flow, and fingering. Specifically in the DNAPL experiments, fingering played a critical role in the final distribution pattern. The final entrapment distribution exhibited a random pattern. Development of a characterization methodology that will attempt to obtain statistical parameters of the random field of entrapment using multiple tracers has been initiated. This project is in its first year.
Clients/Users: The developed technologies will be of use to environmental scientists, environmental engineers, geologists, and hydrogeologists who are employed by U.S. Environmental Protection Agency and other federal and state regulatory agencies, U.S. Department of Defense, U.S. Department of Energy, environmental consulting firms, and the manufacturing industry.
Key words: aquifers, organic chemicals, nonaqueous phase liquids, remediation.
Goal: Investigators are attempting to develop a new technology for one-step destruction of hazardous substances, including chlorocarbons, chlorofluorocarbons, organophosphorus, nitrogen, and sulfur compounds. This new technology is based on ultrahigh surface area metal oxides with reactive surfaces that behave as "destructive adsorbents" (surfaces that adsorb and break chemical bonds in the hazardous adsorbate). Research objectives are (1) to develop the best ways of synthesizing destructive adsorbents, (2) to understand the surface chemistry going on during the adsorption/destruction process, and (3) to develop a second generation of better destructive adsorbents based on multilayer oxide/oxide composites. Destructive adsorbent technology has promise as an alternative to incineration and for air purification systems.
Rationale: Organic compounds containing halogens can be completely destroyed under mild conditions using metal oxides. Destructive adsorbent technology has promise as an alternative to incineration and for air purification systems. Further research is needed to develop this technology so that it can be used in field applications.
Approach: Research work on the production of magnesium oxide, ferric oxide on magnesium oxide, and calcium oxide in nano-scale particle size and reactivity studies are being carried out. Adsorption and transformation of chlorinated hydrocarbons, phenols, and phosphorous compounds are being investigated.
Status: Work has been done with nanoscale calcium oxide (CaO) including Fourier Transform Infrared (FTIR) studies of the CCl4 + CaO reaction. In work on decomposition of trichloroethylene on CaO, trichloroethylene was adsorbed on calcium oxide at various temperatures under the pressure of 50 Torr of chlorocarbon. The amount of adsorbed TCE is determined by the gain in the weight of the oxide. The solid product is a black powder, CaOCl2 based on the powder XRD. Experiments related to surface area and OH groups on CaO revealed that autoclave prepared CaO has a larger number of OH groups compared to conventionally prepared CaO. Studies at lower temperatures are necessary to finish the comparison. A bench-scale fixed bed reactor has been built and is working well. Work on second generation destructive adsorbents has shown that [Mn2O3]MgO, [V2O3]MgO, [Fe2O3]MgO, and [Fe2O3]CaO are the most efficient for destructive adsorption. The [V2O3]MgO is the very best sample for the AP-MgO series. Experiments have been conducted with zero-valent metals to destroy chlorocarbons in water. Results from work with Znº + Cl2C = CHCl indicate that nanoparticle Znº is most reactive. Current work is aimed at determining products and material balance. This project is in its third year.
Clients/Users: Results of this research are of interest to other researchers and to those in private industry. Representatives from several government agencies have expressed interest in the research.
Key words: magnesium oxide, carbon tetrachloride, adsorption, calcium oxide.
Goals: Goals are to establish accurate predictions of desorption kinetics of munitions residues by elucidating changes in sorption characteristics over time; to characterize transport properties of both freshly added and aged RDX, TNT, and principal degradates; and to predict the fate and transport of munitions residues over time with a computer transport model.
Rationale: Past disposal practices of munitions production facilities have resulted in contamination of terrestrial and aquatic ecosystems. Efforts to date have documented the extent of contamination and estimated potential migration routes. To predict the fate and transport of munitions in soils, an accurate description of the adsorption-desorption process is critical.
Approach: Investigators hypothesize that munitions residues residing in soils for extended periods may be more tightly bound into a soil organic fraction and that this bound fraction may be more important in predicting the long-term fate and transport of munitions residues. The proposed research will elucidate the transformations, mechanisms, and reversibility of munitions residues in soils with traditional sorption experiments and diffuse reflectance (FTIR) spectroscopy. The validity of using transport equations that assume instantaneous equilibrium, isotherm linearity, and adsorption-desorption singularity in field contaminated soils will also be tested. The proposed research will characterize the sorption of munitions residues in soil and provide improved predictions on desorption kinetics.
Status: Results from TNT sorption and transport experiments indicate that TNT sorption, transport, and degradation are concentration-dependent. Researchers found that assumptions of linear adsorption and singular adsorption-desorption, commonly used in transport modeling, are likely invalid for predicting TNT transport in highly contaminated soils. Transport experiments indicated that the fate of TNT in soil is highly dependent upon concentration. Further experiments provide strong evidence for the formation of bound residues of TNT degradates to surface and subsurface soil. Due to reduced availability, this process provides one possible pathway for practical detoxification of TNT residues. Experiments provide strong evidence for denitrification of TNT by P. savastanoi, and investigators have determined environmental conditions favoring this degradation pathway. Chemical (abiotic) treatments of Fenton oxidation and metal reduction have an excellent potential to remediate munitions-contaminated soil and water. Using these two techniques, soils with TNT and RDX contamination in excess of 1000 mg kg-1 were successfully remediated below the remediation goals established for the Nebraska Ordnance Plant. The most common pathway for microbial transformation of nitroaromatics is by reduction of nitro groups to amino groups via nitroso and hydroxylamino intermediates. Results from a kinetic study of adsorption and abiotic transformation of TNT in the presence of clay minerals and iron metal indicate that adsorption of TNT to both vermiculite and iron is very rapid. This project is in its third year.
Clients/Users: This research will be of use to those in munitions production facilities, U.S. Department of Defense, and others.
Key words: fate and transport, munitions, soil, adsorption, diffuse reflectance spectroscopy.
Goal: The goal of this project is to conduct a detailed investigation of air sparging systems operated in a pulsed mode to provide a fundamental framework from which to evaluate the applicability and effectiveness of biosparging technology for a given set of site, soil, and waste constraints.
Rationale: Air sparging represents a highly attractive remediation alternative for contaminants located below the ground water table. It has been shown through anecdotal evidence that contaminant emission rates increase and ground water concentrations are greatly reduced at ground water monitoring well points. Specific mechanisms of air sparging system performance are yet to be investigated, and adequate monitoring of field scale systems to quantitatively document their performance throughout affected areas of injection well influence are yet to be developed.
Approach: The proposed research project will involve two integrated components, companion field scale and laboratory scale studies. The field study will be utilized to provide mass transfer and contaminant biodegradation rates resulting from a field scale biosparging system, as affected by media property and heterogeneity limitations inherent at field sites. The laboratory component of the proposed research will provide detailed analysis of mass transfer and contaminant degradation rates under controlled conditions. Laboratory investigations will include an evaluation of the effect of bubble size, air injection rate, air injection depth, media properties, and contaminant properties on observed mass transfer and contaminant degradation rates. Air injection versus inert gas injection will allow the separate evaluation of mass transfer and degradation, while air injection in clean water systems will allow an evaluation of system mass transfer relationships independent of effects due to contaminant properties and/or contaminant/media interactions.
Status: Development of an expert system shell has been initiated. This expert system is being designed to provide technical assistance to the regulatory community in evaluating potential effectiveness and applicability of various technologies for management and remediation of contaminated soils and ground water resulting from petroleum releases. It will provide a standard approach for the site assessment process, guiding the user through source characterization, vadose zone and saturated zone contaminant mass estimations, contaminant plume delineation, and intrinsic biodegradation rate estimates, and with results of this study, suggestions for air injection-based design and predictions of system performance. Work is also being directed toward design of an instrumentation bundle for use in collecting in situ measurements in a three-dimensional sampling grid surrounding the injection point at the field site. Other work included use of an analytical model to design the sampling grid, surveying the site to locate the injection point and sampling points, and carrying out an economic evaluation of sampling procedures and instrumentation to identify the most feasible data collection scheme for use in field testing. This project is in its second year.
Clients/Users: Results from this project will be of interest to other researchers, the U.S. Department of Defense, private industry, and regulatory personnel.
Key words: biosparging, biodegradation, mass transfer.
Goal: The overall goal of this research effort is to provide new information concerning the distribution of polycyclic aromatic hydrocarbon (PAH) biotransformation products among humic materials associated with the solid fraction of soil and the water soluble extract (leachate) fraction, and the effect of environmental variables and amendments on humification and leaching.
Rationale: There is a lack of information concerning transformation intermediates regarding their reactions, measurement, and management in soil bioremediation systems. Specifically, the role of the humification process is currently unknown in prepared bed systems. Disappearance of compounds within soil treatment systems does not necessarily indicate mineralization or detoxification of toxic and hazardous compounds. The formation of intermediates and the fate of those intermediates with regard to association with the soil solid phase in the process of humification is an area where information is needed in order to fully assess the treatment effectiveness of soil bioremediation systems. Development of information addressing behavior of transformation intermediates with an emphasis on characterizing humification of target organic chemicals would increase our understanding of soil bioremediation processes with regard to protection of public health and the environment. Based on information developed in this project, techniques for management of the humification process may be identified and applied to soil bioremediation systems.
Approach: The approach in this project is to use samples of soil taken from field-scale bioremediation systems treating creosote- and creosote/PCP-contaminated soil. Soil samples have been taken from the Champion International Superfund site. The first activity involves identification of PAH and PCP transformation products that occur in soil systems and that can be extracted. The second activity involves chemical mass balance and toxicity determinations during treatment and development of instrumental approaches for evaluating humification. The approach is used to generate information concerning: (1) chemical bonding of PAHs and PCP/intermediates with the soil solid phase, humic and fulvic acid fractions, and with leachate; (2) effects of environmental variables (light, temperature, soil moisture) on the humification process; and (3) effects of amending soil with electron acceptors on humification, mineralization, and volatilization.
Status: PAH microbial intermediates that could be obtained commercially and that were selected for further analysis in wood preserving-contaminated soil included: (1) 1-hydroxy-2-naphthoic acid, (2) 2-carboxygenzaldehyde, (3) 2-hydroxy-3-naphthoic acid, (4) 2,3-dihydroxynaphthalene, and (5) 3,4-dihydroxybenzoic acid. These intermediates have been tentatively identified in field site soil by HPLC instrumentation. Microtox Toxicity(TM) assay results indicated that both phenanthrene and PCP exhibited higher toxicities than the intermediates. An evaluation of the fate of the intermediates was undertaken using mass balance microcosms containing field site soil. Results indicated up to 50% mineralization of 1H2NA and up to 20% mineralization of 2,3-DHN over a 30-day period, measured as CO2 evolution. Additional tests are currently underway to determine the significance of volatilization of intermediates from site soil. In order to evaluate apparent humification potential through clay mineral "trapping," changes in d-basal spacing in montmorillonite and illite clays were measured in the presence of low dielectric constant solvents using X-ray diffraction instrumentation. Initial chemical mass balance experiments have been performed for both pyrene and PCP. This project is in its first year.
Clients/Users: Information generated from this project will be useful for regulators and the wood preserving industry. The U.S. Environmental Protection Agency has expressed interest in this project. The U.S. Department of Defense is also interested in this project.
Key words: bioremediation, humification, mineralization, leaching, volatilization, intermediates.
Goal: Through use of prompt gamma ray neutron activation analysis (PGNAA), the goal of this project is to develop analytical procedures for "de-convolution" of measured gamma ray spectra to yield contaminant concentration profiles.
Rationale: The prompt gamma ray neutron activation analysis (PGNAA) methodology is ideally suited to measurement of soil concentration profiles of the heavy-metal contaminants associated with mining and metallurgical enterprises. This project will lead to improved precision in site characterization, thereby minimizing quantities of soil to be decontaminated.
Approach: This project is concerned with in situ hazardous-waste site characterization for and diagnosis of the need for decontamination. This project will deal with analysis of factors affecting speed and accuracy of the PGNAA method and how both soil conditions and neutron-source/gamma-ray detector geometry need to be accounted for in optimization of data collection and analysis. The work output of this project will be documentation of methodology. Investigators will make every effort to work directly with commercial and government enterprises in implementation of optimization methods developed for data collection and analysis.
Status: A review of the literature has been conducted. Characterization of soils has been done to find representative chemical composition of soil for use in computer modeling. Mathematical models that relate contaminant concentration profiles to uncollided gamma-photon intensities have been developed. Both models assume a homogeneous soil with contaminant concentrations varying only with depth. The phase of the research investigating neutron transport in soil has begun. One-dimensional modeling for a broad beam of neutrons normally incident on the soil surface has been developed. Many aspects are being investigated for the determination of the contaminant profiles in the soil using the PGNAA method. This project is in its first year.
Clients/Users: This research is directed toward meeting technology needs of the U.S. Department of Energy. This project will also be of interest to those in mining and metallurgical enterprises and the U.S. Department of Defense.
Key words: prompt gamma ray neutron activation analysis, remote sensing, characterization, monitoring, sensor technology.
Goal: This project is designed to improve understanding of fundamental relationships between surfactant chemistry, contaminant solubilization, and subsequent biodegradation rates in soils, while developing novel methods which may be useful in the bioremediation of nonpolar organic compounds in soils.
Rationale: During the past decade, much discussion has centered on the unavailability of sorbed compounds to soil microorganisms; it is generally now assumed that desorption and diffusion of bound contaminants to the aqueous phase is required for microbial degradation. Furthermore, with aging, many nonpolar contaminants form irreversibly bound residues which are difficult to extract with nonpolar solvents and are essentially unavailable to indigenous microbial communities or to those added as an inoculum to stimulate biodegradation. In a recent workshop convened to discuss major research needs in bioremediation, the bioavailability of soil bound contaminants was consistently identified as a fundamental limitation in enhancing rates of contaminant biodegradation in soils. One of the strategies for enhancing desorption rates and subsequent biodegradation rates of nonpolar contaminants in soils is the use of surfactants.
Approach: A series of contaminant partitioning studies using a wide range of surfactants with varying structures will be performed. Functional relationships between surfactant concentration, surfactant structure, and extent of contaminant solubilized will be established using batch and column studies. Effects of surfactants on subsequent biodegradation rates of phenanthrene, PCP, DDT, and PCB will be studied under batch and transport conditions using two representative bioremediation strategies: indigenous microbial populations and addition of white-rot fungi. Degradation rates will be determined under batch and transport conditions in previously unconates fate of heavy metals in a vegetated soil and to use the model to develop a protocol for determining the most effective vegetative planting strategies for immobilizing heavy metals in contaminated soil.
Rationale: Abandoned sites associated with old heavy metal mining and smelting activities often have a large proportion of their area without vegetative cover. This allows erosional forces to proceed at a maximum rate, and materials with high heavy metal concentrations are dispersed by wintaminated soils with and without contaminant aging. In addition, contaminant degradation in soil samples from several field sites contaminated with PCP and polyaromatic hydrocarbons will be compared to controlled laboratory experiments.
Status: Collection of eight contaminated soils has been completed for use in surfactant experiments. These soils represent a range in creosote/hydrocarbon contamination. All soils are currently being characterized for chemical content, microbiological activity, and microbial community analysis. Development of laboratory methods for growing white-rot fungi in soil columns for use in surfactant experiments has been conducted. A preliminary screening experiment designed to determine the potential toxicity of biosurfactants on white-rot fungi has been performed. To date, white-rot fungi appear to grow well in the presence of biosurfactants. Several column transport experiments showing enhanced transport of DDT in the presence of micelle and nonmicelle forming surfactants have been conducted. Batch degradation experiments of phenanthrene in the presence of model soil organic matter phases have been performed. These experiments are designed to determine the extent of bioavailability of sorbed phenanthrene to various substrates. This project is in its first year.
Clients/Users: This research will be of interest to members of industry and to the U.S. Department of Defense.
Key words: surfactants, bioavailability, biodegradation, nonpolar organic compounds.
Goal: The goal of this research is to understand contaminant binding to soil organic matter, particularly the fraction known as humin.
Rationale: Most previous work on the nature of contaminant binding to soil organic matter has utilized 14C-labeled compounds to reconstruct the fate of contaminants introduced into a soil system. Essentially all of these studies have stopped at the point of assigning a fraction of the bound-radioactivity to one of the humic fractions of soil organic matter; no studies have been able to characterize the actual nature of bound-residues or the nature of their interaction with a humic material. The humin fraction of humic substances is usually the predominant organic material in most soils; humin organic-carbon typically represents more than 50% of the total organic-carbon in a soil, and a significant fraction of most anthropogenic organic compounds bind rapidly and, in many cases, irreversibly to it. Yet, despite these compelling reasons for a detailed understanding of the nature of contaminant binding to humin, very little is known about its environmental chemistry.
Approach: This study will utilize a new technique that not only isolates humin but, for the first time, permits the separation of humin's organic components from its inorganic component and fractionates the organic components into recognized compound classes. Carbon-14 and carbon-13 labeled contaminants; the polynuclear aromatic hydrocarbons napthalene, phananthrene, and benzo[a]pyrene; and the polychlorinated biphenyls 4,4'-dichlorobiphenyl and 2,2',5,5'-tetrachlorobiphenyl will be incubated with two soils of different composition in separate experiments. Organic components of the soil will be isolated by a combination of traditional and MIBK methods. Humin will be fractionated into its components using the MIBK method. Using ultrafiltration, scintillation counting, and 13C CPMAS NMR, the organic matter will be fractionated and the qualitative and quantitative nature of contaminant binding to humin assessed. The role of lipids in contaminant binding to humin will be investigated utilizing column adsorption studies with humin from which first the lipids and then the humic component have been selectively removed. These results will be evaluated in light of the partitioning model of contaminant sorption to soil organic matter.
Status: Incubation experiments have been started, and preliminary characterizations of humic material fractions in the soils have been performed. The first major results-oriented research milestone, construction of the mass balances to describe distribution of contaminants among the different soil organic matter fractions, has just begun. Preliminary results have shown that the adsorption of PAH and PCB to soil organic matter in the presence of water is rapid and essentially complete. This project is in its first year.
Clients/Users: Results of this project could be used by regulatory agencies, individuals conducting research into the fate and transport of environmental contaminants, or those attempting to produce more effective herbicides or pesticides. The U.S. Department of Defense will also be interested in this research.
Key words: contaminant binding, humin, soil organic matter, binding mechanisms.
Goal: The goal of this project is to develop a systematic approach to the design and management of vegetative remediation schemes and to implement this approach in a decision support system that can be used by environmental professionals to evaluate the potential use of vegetative systems for remediating a contaminated site.
Rationale: Several previous and current research projects have investigated the potential for vegetation to aid in remediation of soils and ground water that are contaminated near the soil surface. One of these projects produced models that can predict the fate of hazardous organic substances in the root zone of a soil. Preliminary comparisons between developed models and laboratory experiments were favorable, yet two significant modeling limitations were observed. First, the models could only simulate a limited number of contaminant degradation processes. Second, the models require a large amount of information about a site where vegetation is being considered as a remediation option. These limitations could prevent use of the models in predicting potential benefits of a vegetative remediation system designed by environmental professionals involved in soil and ground water remediation projects. To overcome these limitations requires development of a methodology that can synthesize the required modeling data from information that is available about a remediation site and use the model to systematically arrive at an efficient remediation design.
Approach: Objectives of this project related to the efficient design of vegetative remediation systems will be achieved by developing a general methodology based on systems theory. This involves forming a systems statement that includes the quantitative definition of goals of the remediation project, design variables that can be manipulated to attain these goals, and practical and legal constraints that limit attainment of these goals. Several conventional and heuristic solution procedures will be used to solve the systems statement. The most robust and computationally efficient procedures will be selected for continued use in this project. Once developed, the design procedure will be applied to a field site within U.S. EPA Regions VII and VIII that has near surface soils and ground water contaminated with hazardous organic substances. Then a graphically-based decision support system will be developed from this design experience for future use by environmental professionals.
Status: Anaerobic degradation is a significant element in degradation of TCE and TCA; hence, the models must provide a mechanism to simulate anaerobic degradation of contaminants to produce valid simulations. To this end, the model is being modified to include anaerobic degradation processes which are used when the simulated dissolved oxygen content of the soil water drops to near zero conditions. To allow for easier future model modification and use of site-specific degradation simulations, the current computer code is being reworked into a more efficient object-oriented programming style. It has been decided that an attempt to design a vegetative remediation system at the Riley County Landfill will be undertaken. An initial planting of alfalfa has taken place. Exploration and evaluation of alternative algorithms for solving complex optimization problems has begun. This project is in its first year.
Clients/Users: This project will be of interest to government agencies, such as the U.S. Department of Defense and U.S. Department of Energy, and to industry.
Key words: modeling, vegetation, phytoremediation, plant remediation.
Goal: This research will explore the possibility of using sonic pulse propagation, combined with advanced signal processing techniques, to determine the depth of coherent cement plugs in abandoned wells.
Rationale: Each year many wells are plugged and abandoned throughout the United States. These include water wells, mineral exploration wells, and oil and gas production wells. Many wells penetrate one or more aquifers. The wells also pierce formations containing oil and gas reservoirs, mineral deposits such as uranium and lead, and water contaminated with salt, iron, selenium, sulfates, and radon. The well borehole provides a mechanism for communication of fluids and gasses between formations. When aquifers are involved, this poses a severe pollution threat. For example, if the borehole passes through both an aquifer and a brine-bearing formation, the brine can invade the aquifer and compromise the quality and purity of the water. The problem escalates if the brine layer is pressurized with respect to the aquifer, causing continuous flow of brine into the fresh-water formation. Conversely, water will escape from the aquifer if its hydrostatic pressure exceeds the pressure in other porous layers. Improperly plugged wells can compromise the integrity of the aquifer layer since this natural isolation is destroyed, allowing water to come in contact with these potentially toxic materials.
Approach: In this project, investigators will develop, instrument, and test a borehole scale model. Research will be undertaken to understand wave propagation and plug reflections in the model. Investigators will simulate responses for selected borehole scenarios and evaluate various models and receiver configurations. They will develop a sensor system, analog-to-digital conversion, and portable computer-based analysis system for measuring plug reflections, develop signal processing methods to extract plug information from reflection data, and conduct field tests to characterize performance of the prototype system.
Status: Several preliminary tests to measure noise and signal levels have been conducted on a 900-foot-deep cased well. The signal-to-noise ratio was found to be too large for the planned experiments. An artificial borehole is being developed that will accommodate the experiments. The artificial borehole will consist of 100 to 200 feet of 5.25" steel well casing positioned horizontally on the ground. This setup can be readily extended to any required length. The resulting horizontal borehole will be easily accessible at all points along its length for attaching acoustic sensors. Ten sections of casing have currently been set up on the site. If needed, the horizontal borehole can easily be covered with sand and filled with fluid to better simulate actual borehole conditions. Collaboration with the Bureau of Land Management to locate wells on Federal property that could be used in field tests has begun. A finite-difference modeling software program to simulate the subsurface wavefield is being developed. Geophones are being investigated as sensors to detect low-amplitude reflection energy. Initial experiments on the artificial borehole are promising and show adequate reflection energy to resolve plugs in actual boreholes. This project is in its first year.
Clients/Users: This project will be of interest to agencies responsible for protecting subsurface aquifers. It will also be of interest to the Department of Justice, U.S. Environmental Protection Agency, and U.S. Department of Defense. Private oil and gas exploration companies may also be interested.
Key words: boreholes, aquifers, oil wells, gas wells, cement plugs.
Goal: The principal objective of this project is to determine--through a series of carefully controlled bench-scale tests designed to measure changes in hydraulic conductivity of soils treated with ultramicrobacteria compared to untreated soils--the feasibility of using biologically modified soils as waste containment barriers.
Rationale: The U.S. Environmental Protection Agency (EPA) is responsible for developing standards and regulations governing design, operation, and maintenance of landfills, surface impoundments, and waste piles used to treat, store, or dispose of hazardous wastes. A good deal of EPA effort, therefore, is focused on design and performance of waste containment systems. All such systems include one or more barriers to prevent transport of contaminants into the environment. Performance of contaminant barriers depends upon many factors, including type of wastes being contained, materials used to construct the barrier and their compatibility with the waste materials, quality of construction, and long-term durability under adverse environmental conditions. Materials used for barriers should be inexpensive, have low hydraulic conductivity and low molecular diffusivity, and must be durable enough to last for tens and possibly hundreds of years. This project will involve developing new, low-cost barrier materials bioengineered for waste containment.
Approach: In order to determine the feasibility of using biologically modified soils as waste containment barriers, a series of bench-scale tests will be performed to measure changes in hydraulic conductivity of soils treated with ultramicrobacteria (UMB) compared to untreated soils. The project will investigate the range of biological conditions under which UMBs have the ability to reduce soil hydraulic conductivity. Based on results of bench-scale tests, investigators will establish the range of physical and biological parameters most likely to result in successful application of biofilm technology to the design and construction of field-scale waste barriers. Finally, feasibility of using biofilm barriers at the prototype scale will be tested.
Status: A medium-grained quartz sand has been selected as the soil to be used. This soil has a high hydraulic conductivity and is relatively free of organic material and easily compacted into specimens which can be placed into a permeameter cell without any special handling. Initial tests have been conducted with the bacterium klebsiella pneumoniae. This bacterium is an excellent biofilm producer, but it has the potential to cause pneumonia in humans. Bierjerinckia, another biofilm-producing bacterium that is not pathogenic to humans, is an excellent candidate for further research. Three biofilm-treated soils have been tested. Similar behavior has been observed in specimens tested with klebsiella and bierjerinckia. This project is in its first year.
Clients/Users: Results of this project will be of interest to the U.S. Environmental Protection Agency, U.S. Department of Defense, environmental contractors, regulators, and the mining and agriculture industries.
Key words: biofilms, hydraulic conductivity, ultramicrobacteria, waste containment, barriers.
Goal: The overall goal of this project is to understand factors which promote or retard biomass accumulation in porous media with an intent to apply such understanding toward prediction and beneficial manipulation of permeability and mass transport properties.
Rationale: A concept which appears promising in the manipulation of biological and chemical processes for remediation of subsurface hazardous waste sites is the creation of biobarriers for containment and remediation of soil and ground water contaminated with organics and heavy metals. Biobarriers are formed by stimulating growth of microbial biomass so as to plug the free pore space flow paths through porous media, thereby reducing permeability and mass transport. Selective plugging of permeable strata is currently being explored as a means of preventing contaminant migration of ground water contaminants from hazardous waste sites. Penetration of bacteria through porous media varies between extensive penetration of ultramicrobacteria and formation of plugging biofilms on the proximal formations by well-fed cells of the same organisms. Investigators will attempt to use simple nutritional differences to deliver bacteria to any location in the subsurface environment to resuscitate and either plug the formation or carry out specific biodegradation.
Approach: Test organisms will include a Klebsiella pneumoniae as well as these same bacteria starved for ultramicrobacteria size. Experimental objectives will be carried out using a series of flowing packed bed reactors including flat plate flow cells and packed columns. Procedures will be developed for applying bacterial inoculum, along with subsequent resuscitation with nutrients, so as to produce controlled reduction of porous media permeability and dissolved oxygen transport. Researchers will quantify and model temporal and spatial variability in the biofilm accumulation (and mass transport) using bioluminescence. Finally, a mathematical model for biofilm accumulation and corresponding permeability and dissolved oxygen gradients in porous media will be developed and evaluated.
Status: Columns have been inoculated with streptomycin-resistant K. pneumoniae. The effluent cell density was not significantly higher than the initial effluent cell density. However, the number of streptomycin-resistant cells in the column effluent increased. Although inoculated cell recovery was less than 10%, the streptomycin-resistant inoculum comprised a significant proportion of the culturable microbial community in the column effluent. Next, the columns were treated with sodium citrate medium (SCM). Analysis of fluid samples taken throughout the column revealed that viable cells and nutrient medium components were uniformly distributed throughout the column. Nutrient resuscitation led to a uniform increase in bacterial numbers throughout the column. Examination of colony morphotypes on HPC enumeration plates suggested that use of SCM for resuscitation led to a selective advantage for colonization success of the inoculated K. pneumoniae population over the culturable indigenous bacterial population. Following 16 days of nutrient resuscitation, nearly 100% of the microbial population in the column effluent were culturable. Nutrient resuscitation of the starved bacterium inoculum resulted in a reduction in hydraulic conductivity throughout the length of the columns. This project is in its first year.
Clients/Users: This project will interest the U.S. Department of Energy, U.S. Department of Defense, environmental contractors, regulators, and those in the petroleum industry.
Key words: biofilms, hydraulic conductivity, ultramicrobacteria, waste containment, barriers.
Goal: The goal of this project is to conduct a detailed investigation of microbially-mediated containment mechanisms taking place near the source of trichloroethene (TCE) and dichloroethene (DCE) plumes at a site in Alaska.
Rationale: Intrinsic remediation represents a highly attractive remediation alternative, particularly for residual phase contaminants located at or below the ground water table. Mechanisms of attenuation of hydrocarbon plumes and general approaches for the assessment of their attenuation rates are at a fairly well developed stage, and this methodology and understanding of process mechanisms has been supported by numerous field studies at hydrocarbon release sites. Chlorinated solvent plume attenuation has been investigated to a much lesser extent. Mechanisms of cometabolic reduction of TCE, as well as TCE anaerobic dechlorination have been evaluated under field conditions. This research will provide additional data near to the source area of the selected site, where rapid TCE attenuation is taking place, to significantly improve our understanding of the fate of TCE under natural aquifer conditions.
Approach: This project will involve integration of field sampling and analysis work with a companion U.S. Air Force Center for Environmental Excellence (AFCEE) field scale study. Field work will be utilized to provide TCE and daughter product transformation rates and additional evidence of the existence and mechanisms involved in the anaerobic degradation of TCE under actual field conditions prevalent at the selected site. An additional 25 soil and ground water sampling probes will provide near field measurements of the apparent rapid transformation of TCE and DCE taking place in the aquifer. These probes will be placed at the site and will be sampled along with all existing locations. Samples from these new probes will be analyzed for TCE, intermediate products, electron acceptor composition, oxidation/reduction potential status and other sources of electron donor that could be driving the anaerobic metabolism of TCE. These data will be instrumental in verifying the current conceptual model for the site and in more precisely quantifying the intrinsic TCE remediation mechanisms taking place in what appears to be a highly reactive zone of the contaminated aquifer system.
Status: In previous complimentary work, investigators have been involved in field measurement of a range of aquifer conditions coupled with an extensive array of laboratory-determined water quality parameters focused on quantifying terminal electron acceptor composition and the nature and distribution of parent compound and intermediate compounds of the ground water system. Monitoring of these parameters has yielded ample evidence that anaerobic TCE degradation, via anaerobic dechlorination, appears to be taking place at the site. However, the sampling grid is not sufficiently fine near the source area to completely delineate the reaction pathways and to yield acceptable mass balance data for intermediate compound production versus parent compound reduction rates observed at the site. This project will provide data near the source area necessary to definitely describe reaction pathways and reaction rates for TCE
Approach: This study will focus on an abandoned zinc and lead smelter site in southeast Kansas. The investigators propose to begin investigations whose ultimate goal is to immobilize the metals in place. This would be accomplished with grading to 3-5% slope, to encourage runoff without excessive erosion, and the use of rapid growing poplar trees that have a high water demand. This strategy would minimize net p and intermediate product degradation taking place under natural, intrinsic site conditions. This project has begun recently.
Clients/Users: This project will be of interest to the U.S. Department of Defense, U.S. Department of Energy, regulators, and other researchers.
Key words: trichloroethene, dichloroethene, ground water, monitoring probes, northern climate.
Goal: The goal of this research is to develop intelligent or computer-aided systems tools for synthesizing and designing environment-friendly processes and controlling such processes with minimum waste generation.
Rationale: Waste minimization can be realized through source reduction and recycling. Efficient process synthesis and design, robust control, reliable diagnosis, and flexible production scheduling are important techniques to effectuate source control of waste.
Approach: The approach being employed is comprehensive and unique. Comprehensiveness of the proposed approach arises from the fact that all three levels of synthesis and design of processes and control systems for these processes, namely, macroscopic, mesoscopic, and microscopic levels, are incorporated into it. Uniqueness arises from the fact that the approach resorts to the most modern graph-theoretic methods, which are mathematically and theoretically rigorous, and to the techniques of artificial intelligence and neural networks, which are logically sound and computationally efficient.
Status: At the macroscopic level, the investigator has approached process synthesis by first identifying operating units represented by special directed bipartite graphs, specifically process or P-graphs, which uniquely specify each process structure in the synthesis. Materials are denoted by a classification scheme. For a given set of operating units, a large number of combinatorial structures are possible, but only an inordinately small fraction is actually feasible, which is determined on the basis of axioms stating self-evident facts. This results in a set of mixed integer nonlinear programming problems of relatively small size that can be solved effectively and speedily by means of the novel accelerated branch-and-bound algorithm. At the mesoscopic level, the structure of a process has been refined to improve its efficiency. This has been accomplished through heuristics rules much less computationally complex than traditional algorithmic techniques. It is envisioned that integration of these heuristic rules and the algorithmic method based on the P-graph can eventually give rise to a highly efficient technique at this level. At the microscopic level, detailed interconnections among process units have been identified, and the control system has been incorporated into the process structure. Improved systematic techniques based on AI methodology allow highly controllable mass and heat exchanger networks to be synthesized. The research to date has demonstrated that this comprehensive approach to process design or synthesis is highly effective and capable of synthesizing efficient systems for production, in-plant waste treatment, and integrated production and treatment. The third year of this project has been completed but some work is continuing.
Clients/Users: Results are of interest to design engineers who wish to incorporate waste minimization into process synthesis and control system design.
Key words: waste minimization, process synthesis, robust control, pollution prevention, graph theory.
Back to Annual Report Table of Contents
Back to HSRC home page