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  1. Introduction
  2. Summary

Biological Remediation of Contaminated Sediments, with Special Emphasis on the Great Lakes

Report of a Workshop
Manitowoc, Wisconsin
July 17-19, 1990

Edited by C.T. Jafvert and J.E. Rogers

Co-Chairmen:
Chad T. Jafvert and John E. Rogers
Environmental Research Laboratory
U.S. Environmental Protection Agency
Athens, Georgia 30613

Support was provided by the U.S. Environmental Protection Agency's Great Lakes National Program Office, through the Assessment and Remediation of Contaminated Sediments (ARCS) Program, by Environment Canada, and by the U.S. Environmental Protection Agency's Biosystems Technology Development Program.

Environmental Research Laboratory
Office of Research and Development
U.S. Environmental Protection Agency
Athens, Georgia

 

FOREWORD

As environmental controls become more costly to implement and the penalties of judgment errors become more severe, environmental quality management requires more efficient analytical tools based on greater knowledge of the environmental phenomena to be managed. As part of this Laboratory's research on the occurrence, movement, transformation, impact, and control of environmental contaminants, research is performed on the biological remediation of contaminated sediments.

The Assessment and Remediation of Contaminated Sediments (ARCS) Program is a major activity of the U.S. Environmental Protection Agency that evaluates and demonstrates remediation alternatives for contaminated sediments within the Great Lakes Basin and associated risk assessments. In the summer of 1990, more than 60 scientists from the United States, Canada, and The Netherlands participated in a special workshop to present the current state-of-the-science concerning the biodegradation of polychlorinated biphenyls and polyaromatic hydrocarbons and the biological treatment of metal species. This proceedings provides a synopsis of the information exchanged at that workshop.

Rosemarie C. Russo, Ph.D.
Director
Environmental Research Laboratory
Athens, Georgia

ABSTRACT

These proceedings describe a workshop held July 17-19, 1990 in Manitowoc, WI, at which biological remediation of contaminated sediments was discussed. For the purpose of the workshop, contaminated sediments of primary interest were those within six of the Areas of Concern (AOC) identified by the U.S./Canada International Joint Commission's Great Lakes Water Quality Board; five of which are priority concerns of the U.S. Environmental Protection Agency's Assessment and Remediation of Contaminated Sediments (ARCS) program.

The workshop was organized around four topic areas: (1) Overview of the Areas of Concern; (2) Biological degradation of PCBs; (3) Biological degradation of PAHs; and (4) Biological treatment of metal species. For the first topic area, presentations were made describing site characteristic of the Ashtabula River, OH; Buffalo River, NY; Sheboygan River, WI; Grand Calumet River, IN; Saginaw River and Bay, MI; and Hamilton Harbor, Ontario, Canada. For the remaining topic areas, presentations were made by investigators actively involved in either bench, pilot, or full-scale studies concerning these areas. In this document extended abstracts written by the presenters are given, as well as brief summaries of the presentations and discussion sessions.

ACKNOWLEDGEMENT

We gratefully acknowledge the efforts of all those individuals who contributed in one form or another to the origination of this report. The Workshop and this report, truly, were group projects. Recognition is extended to David Cowgill and Paul Horvatin of E.P.A.'s Great Lakes National Program Office (GLNPO) and members of GLNPO's Engineering and Technology Workgroup, and its Chairman, Steve Yaksich of the U.S. Army Corp of Engineers, Buffalo District, for their support and planning input. Also, we deeply appreciate the support and planning input provided by Griff Sherbin and Ian Orchard of Environment Canada. Direction by all these individuals has enhanced this report considerably by their endeavor to assure its applicability to contaminated sediment scenarios within the Great Lakes. Appreciation is given to Paulette Altringer of the Bureau of Mines, Salt Lake City Research Center, who was instrumental in organizing the Metals session. Janice Heath of Technology Applications Inc. and Patricia Van Hoof of The University of Georgia provided indispensable assistance in making Workshop arrangements and coordinating activities during the Workshop. In particular, we wish to acknowledge Janice Heath for her singular effort of synthesizing the many diverse forms of material submitted by the speakers into a consistently formatted and understandable document.

1 INTRODUCTION

The current state-of-the-science of biological remediation of contaminated sediments was discussed in a workshop held July 17 - 19, 1990, in Manitowoc, WI. Special emphasis was devoted to remediation alternatives for sediments within the Great Lakes Basin. The workshop was supported by the U.S. EPA's Great Lakes National Program Office, through the Assessment and Remediation of Contaminated Sediments (ARCS) Program, by Environment Canada, and by EPA's Biosystems Technology Development Program. More than 60 scientists from state and federal agencies, academia, and the private sector from the United States, Canada, and The Netherlands participated.

For the purpose of the workshop, the sediments of primary interest were those within the Areas of Concern identified by the U.S./Canada International Joint Committee's Great Lakes Water Quality Board. Most of the 42 Areas of Concern are located in harbors, bays, or river mouths; 25 are located within U.S. waters, 12 within Canadian waters, and 5 within inter-national channels. Remedial Action Plans currently are being developed for these areas under the 1987 revision of the Great Lakes Water Quality Agreement. A major purpose of EPA's ARCS Program is to evaluate remediation alternatives for the cleanup of these sites with special emphasis given to five sites. These five are Ashtabula River, OH; Buffalo River, NY; Sheboygan River, WI; Grand Calumet River, IN; and Saginaw River and Bay, MI. Two of these five overlap EPA Superfund sites to some extent.

The Workshop was organized around four topic areas:

  1. Overview of the Primary Areas of Concern
  2. Biological Degradation of PCBs, Laboratory and Field Studies
  3. Biological Degradation of PAHs, Laboratory and Field Studies
  4. Biological Treatment of Metal Species

For the first topic area, presentations were made describing site characteristics of the five primary U.S. Areas of Concern and for Hamilton Harbour, Ontario. Major contaminants within these and other areas include polychlorinated biphenyls (PCBs), polycyclic aromatic hydrocarbons (PAHs) and various heavy metal species. The toxicity and recalcitrant nature of these compounds have caused serious environmental concern. Moreover, these classes of contaminants present serious and rather complex treatability problems for essentially all remediation technologies (including biological processes).

For the remaining topic areas, presentations were made by investigators actively involved in either bench-, pilot-, or full-scale studies within these topic areas. To focus dialogue on the Workshop intent, the participants were asked to address or keep in mind the following general questions during presentations and discussion periods:

  1. What stage of development have specific bioremediation technologies reached (e.g., laboratory research, laboratory-field development, or full-scale operation)?
  2. Which development directions are logical continuations for the specific laboratory studies (e.g., above ground reactor treatment, in situ treatment, CDF modification, land farming, or other)?
  3. What level of development is necessary before a full-scale application of this technology is feasible?
  4. What are the rate limiting factors controlling the optimization of the laboratory or field process? These factors may be site characteristic considerations, process operation considerations, or both.
  5. What types of costs are or will be associated with the development of proposed treatment (e.g., capital, labor, maintenance)? How is this cost dependent on site location and characteristics?
  6. What other waste streams may be generated? What losses to the environment will result from specific treatment alternatives? What contaminant residues will result?
  7. What concerns you the most regarding the application of specific bioremediation technologies to the problems associated with Great Lakes sediments?
  8. Given the dissimilarity between bioremediation technologies and other physical or chemical treatment technologies, how should one compare the environmental and financial costs associated with each?

These questions were intended to be used as a guideline. Answers to some were addressed in detail for specific bioremediation alternatives and are addressed in the Summary sections and in several of the Abstracts. The answers to others were only alluded to or are presently unknown. To a large extent this is because biological remediation to treat contaminated sediments may take several forms. Each form (or process design) has its own list of factors or parameters associated with it that must be considered when optimizing treatment. Hence, there are generally no simple answers to questions regarding the feasibility of biological remediation alternatives. Sediments are generally not contaminated with single compounds or even classes of compounds. Additionally, the interactions among the various organisms responsible for the decomposition of anthropogenic compounds and the sediment matrix are unknown in many cases. Such intricacies make a concise summary of this diverse workshop difficult; however, several general conclusions can be drawn. We hope this Proceedings will benefit scientists and engineers who must make choices among diverse treatment technologies. A brief summary of the Proceedings of this workshop has been published by C. T. Jafvert (J. Great Lakes Res. 16(3):337-338, 1990).

Chad T. Jafvert
John E. Rogers

September 1990

2 SUMMARY

2.1 Areas of Concern

Janice K. Heath
Technology Applications, Inc.
c/o Environmental Research Laboratory
U.S. Environmental Protection Agency
Athens, GA 30613

The locations of the 42 Areas of Concern (AOC) identified by the U.S./Canada International Joint Commission's Great Lakes Water Quality Board are illustrated in Figure 2.1.1. Environmental characteristics of the five U.S. AOC whose names are given in this figure were described by either the State AOC Remedial Action Plan Coordinator or the Superfund Site Coordinator for the adjacent Superfund site. A description of Hamilton Harbour, Ontario, was given by Thomas Murphy of Environment Canada.

John McMahon, of the New York State Department of Environmental Conservation (DEC), presented information on the Buffalo River AOC and the Remedial Action Plan Strategy. The Buffalo River, located in western New York State, flows into Lake Erie near the mouth of the Niagara River. Historically, the Buffalo River was used by industries as a transportation channel, a source of cooling water, and a means of disposing of wastewater. These industries were involved in chemical manufacturing (dyes and acids), coke and steel production, and oil refining. Only two of these facilities are still in operation and they are under strict pollution control regulations. Over the years, however, the pollution these industries generated contaminated the river sediments and left hazardous waste on the banks. The bottom sediments contain PAHs, PCBs, and heavy metals, which continue to be a source of contamination to the Buffalo River, as are hazardous waste sites along its banks. Another source of pollution to the river are combined sewer overflows that release dilute sewage and associated contaminants into the river during storm events. In order to restore the Buffalo River's integrity, a Remedial Action Plan (RAP) strategy was devised. The short term goal is to restore the river's ecological system, while the long term goal is to eliminate the sources of pollutants to the river. Presently, the DEC has committed to several initial actions recommended by the RAP for dealing with the sources of contaminants and remediation of the area.

An overview of the Fields Brook Superfund site and the Ashtabula River AOC was given by Pete Sanders of the U. S. Environmental Protection Agency, Region V. The area involved is located in northeast Ohio. Fields Brook flows into the Ashtabula River about 8000 feet from the point at which the river empties into Lake Erie. The Fields Brook site has been on the National Priorities list since the first list was established under Superfund in 1983. Contamination of sediments in this area has resulted from a variety of chemical manufacturers located along Fields Brook. The sediment contaminants include a variety of organic compounds and heavy metals. Clean up and remediation efforts for the Superfund site will involve excavating, dewatering, and either landfilling or thermally treating the contaminated sediment. The option to landfill or thermally treat the sediment will be decided after investigating the mobility of the contaminants, the toxicity and concentration of the contaminants, and the concentration of PCBs. Thermal treatment was indicated in the Record of Decision (ROD) signed by the U.S. EPA in 1986. The ROD also advised a Remedial Investigation (RI)/Feasibility Study (FS) to recognize current sources of contamination to Fields Brook and to examine the extent of contamination to the Ashtabula River. The Ashtabula River investigation included sediment, water, and fish sampling, and started late in 1989. A plan is being developed by the Army Corps of Engineers to dredge the upper portion of the contaminated sediment from the river and place it in a confined disposal area.

Robert Bunner of the Indiana Department of Environmental Management gave an overview of the Indiana Harbor/Grand Calumet River AOC. He showed the initial segment of a video tape entitled "The Grand Calumet River, A River of Contradictions." A copy of this tape can be obtained by contacting Robert Bunner, Indiana Department of Environmental Management, 105 S. Meridian Street, Indianapolis, Indiana 46225. The geographical region associated with the harbor and river has had a long history of industrial activity, beginning in the early part of this century. In fact, over the decades, this portion of the Grand Calumet River has been modified dramatically from its preindustrial state. The major industrial complexes associated with this site over this time period are steel plants. Currently, the dredging of contaminated sediments is proposed in the harbor primarily for navigational purposes, and in the river for remediation purposes. Within this system, deposition of sediments is to the point where it is no longer safe to navigate large ships. The sediments within the river and harbor are contaminated with PCBs, PAHs, and heavy metals including cadmium, chromium, and lead. To give some historical context as to the industrial nature of this area, it is estimated that the land extending one mile from Lake Michigan in the harbor area consists of fill generated from the steel industries over the decades.

Bonnie Eleder of the U.S. Environmental Protection Agency, Region V, presented an overview of the Sheboygan River and Harbor Area of Concern including the Superfund site. The Superfund site includes about 14 miles of the river from the dam at Sheboygan Falls, Wisconsin, east to the harbor on Lake Michigan, including the flood plain of this part of the river. The Area of Concern includes the entire watershed of the Sheboygan River. From 1950 until 1969, the Army Corps of Engineers dredged the lower river and harbor for navigation purposes. The dredging was stopped when heavy metals were found in the sediment. After more testing and sampling, high levels of PCBs also were found. In 1986, the area was added to Superfund's National Priorities List. Three potential sources of contamination were named, and after negotiations, one of the potentially responsible parties agreed to undertake a Remedial Investigation/Feasibility Study (RI/FS) to determine the extent of contamination and look at potential remedial alternatives to deal with the contamination. An engineering firm was hired to conduct the RI/FS. Certain remediation alternatives and associated alternatives are now being assessed including: biological treatment within a pilot confined treatment facility, sediment removal, in situ armoring, and monitoring programs.

Greg Goudy of the Michigan Department of Natural Resources presented a summary of the Remedial Action Plan for the Saginaw River and Bay AOC. The Saginaw River empties into Saginaw Bay, located along the eastern shore Michigan's lower peninsula. As he stated, the water quality of the Bay and River have improved over the last 20 years, but problems still remain. Three primary water quality problems have been recognized in this area. The first is eutrophication which has lead to extensive algal blooms causing taste and odor problems with drinking water from the bay. Second is bacterial contamination caused by combined sewer overflows that discharge raw sewage into the Saginaw River during heavy rains. Finally, there is contamination by anthropogenic compounds such as PCBs and chlorinated dioxins. These have been found in fish tissue and have resulted in public health advisories against fish consumption. The intent of the RAP is to restore the river and bay area to a water quality that is safe so that the areas can once again be used as originally intended without risk to human or environmental health.

Tom Murphy from Environment Canada, discussed the Hamilton Harbour AOC. Hamilton Harbour is located in Hamilton, Ontario on the western bank of Lake Ontario. The main pollutants in the harbor are PAHs, coal tar, and heavy metals. These chemicals have led to the unhealthy fishery, which is of great concern to the public, who have formed a citizens action group. Source controls imposed on the industries in this area have reduced air and water contamination; however, some contaminated "hot spots" still exist. In the areas with low metal contamination, there has been natural degradation of the PAHs and coal tar. Pretreatment methods to make the metals less bioavailable so the bacteria can more easily degrade the PAHs and coal tar are being tested. Another concern, however, is oxygen availability in the sediments. For the biological degradation of PAH compounds, oxygen is necessary; however, the sediments are largely under anoxic conditions. At this time, the recommendation is to dredge and treat the "hot spots" while continuing to study remedial alternatives to this problem.

2.2 Polychlorinated Biphenyls

Chad T. Jafvert
Environmental Research Laboratory
U. S. Environmental Protection Agency
Athens, GA 30613

The congener mixtures of polychlorinated biphenyls (PCBs), produced by Monsanto, were sold under the trade name Aroclor, and contained from 30 to 60 individual congeners (chlorinated analogs of the parent biphenyl of 209 congeners theoretically possible). The last two digits of the number specifying each Aroclor mixture, i.e., 1248 relate the percent chlorine content by weight of that mixture. Hence, Aroclors 1242 and 1248 are generally referred to as the lower (molecular weight) Aroclors and contain mostly di-, tri-, and tetrachlorobiphenyls, whereas Aroclors 1254 and 1260 are referred to as the higher Aroclors and contain mostly penta-, hexa-, and heptachlorobiphenyls. Recent evidence, much of which was presented during this session, shows that the complete microbial degradation of Aroclors is possible. However, the complexity of the microbial processes responsible for degradation, the complexity of the compounds themselves, and the complexity of sediment interactions with microbes and individual congeners makes this class of compounds one of the greatest challenges to bioremediation technologies.

Ronald Unterman presented information regarding the aerobic biodegradation of PCBs. Under aerobic conditions, PCB biodegradation is a cometabolic process in which another substrate, such as biphenyl, is required as a carbon and energy source. Because no advantage may be gained by the indigenous microorganisms in degrading PCBs (no energy is gained), the introduction of exogenous organisms, specifically isolated for their PCB degrading abilities, may facilitate this process. He noted that Envirogen, Inc. is actively involved in isolating bacterial strains with PCB-degrading capabilities, elucidating the biochemical pathways by which these compounds degrade, and isolating the genes responsible for the various steps involved in this degradation. Only the lower chlorinated congeners (i.e., mono-, di-, tri-, tetra-, and some penta-) are amenable to aerobic degradation. As the number of chlorine substituents increases on the biphenyl moiety, aerobic degradation is reduced. The positional selectivity of PCB-degrading strains was also noted, suggesting that the use of several strains may result in the widest range of degradation of all congeners. Several key parameters that must be evaluated when optimizing aerobic degradation in the field include bioavailability, temperature, and utilization of proper microbial strains. He stressed that experiments purporting to show biodegradation of PCBs by simply quantifying total GC peak areas must be carefully evaluated.

John Quensen presented results of laboratory experiments designed to elucidate the anaerobic biodegradation processes of PCBs. He stressed that anaerobic reductive dechlorination occurs only for the more heavily chlorinated PCB congeners. Several of the mono- and di-chlorinated congeners do not appear to be dechlorinated to any extent and represent terminal products of the higher chlorinated congeners. Reductive dechlorination may be of selective advantage to microorganisms in that it can result in a gain in energy for the organisms and can serve as a terminal electron sink. Terminal electron acceptors are often limiting for microbial growth in anaerobic systems. Drs. Quensen, Boyd, and Tiedje have developed a method of transferring PCB-degrading organisms from acclimated sediment to clean or sterilized sediments. Such transfers of activity have now been made for over 10 serial passes. He discussed the difference in dechlorination patterns within sediments from various locations historically exposed to different Aroclor mixtures. In all studies, however, accumulation of ortho-substituted products was observed. The extent of dechlorination was shown to be concentration dependent. This may result both from decreased bioavailability of compound at lower concentrations and/or from increased growth of organisms at higher compound concentrations. He related these studies to the potential for bioremediation of contaminated sites, suggesting either that anaerobic biodegradation alone will reduce sediment toxicity, or that anaerobic/aerobic sequential treatment may reduce the total concentration of PCB congeners. Site assessment should involve evaluation of the presence of dechlorinating microorganisms, in situ dechlorination patterns, sediment type, nutrient and organic carbon concentrations, inhibitor concentrations, and the bioavailability of the PCBs.

G-Yull Rhee reported on laboratory studies of the anaerobic dechlorination of Aroclor 1242 and a single congener (2,3,4,2',4',5'-hexachlorobiphenyl) in Hudson River sediment. In the Aroclor 1242 studies, dechlorination patterns were investigated as a function of Aroclor concentration (100 to 1500 ppm on a sediment dry weight basis, and reducing conditions (sulfide-reduced synthetic medium). After 3 months, significant changes in congener patterns were evident, especially at 300 and 500 ppm Aroclor 1242 with mono-, di-, and trichlorobiphenyls comprising 98% of the total remaining PCBs. Ortho-substituted congeners showed the most significant increases. After 6 months of incubation, congener profiles for the 100 and 800 ppm concentrations showed significant dechlorination, whereas no difference was observed at 1200 and 1500 ppm. Similar to the results of others, no biodegradation other than dechlorination was found. Anaerobic incubation of the single hexachlorobiphenyl produced congeners with two to five chlorines per molecule. The relative concentration of these products varied with incubation time.

William Sonzogni addressed the issue of whether PCBs are being biologically dechlorinated in the Sheboygan River under ambient conditions. The contamination in this river is believed to be primarily from Aroclor 1248 and 1254. Total PCB concentration ranged from 1586 ug/g downstream from the site of contamination, to 0.04 ug/g upstream from the site, with the highest PCB concentrations found in areas of sediment deposition. He presented strong evidence that biological dechlorination was occurring in the river. This evidence included the following observations: a shift in congener profiles (compared to 1248 and 1254) from the higher chlorinated to the lower chlorinated congeners exists in sediment samples; meta- and para- chlorinated congeners were depleted more than ortho-chlorinated congeners; several specific congeners were found in abundance; and finally congener patterns were found to by PCB-concentration dependent with only samples with greater than 50 ug/g total PCB showing these patterns. The physical and chemical processes that affect congener distribution were also discussed. Abiotic degradation was ruled out because of the extreme conditions (temperature, pH) necessary for this to occur over a reasonable time frame. Similarly, preferential sorption of the more hydrophobic congeners would not result in the observed patterns. Laboratory experiments with river sediments have yet to confirm these patterns. He also reported on a multidimensional gas chromatography technique used to resolve congeners which normally co-elute with conventional gas chromatographic methods. This analytical method is useful in analysis of co-planar PCBs (those with dioxin-like toxic properties). Concentrations of these congeners represent a fractional percentage of Sheboygan River PCBs.

Daniel Abramowicz presented results of laboratory studies in which the rate of anaerobic dechlorination of PCB mixtures was enhanced by the addition of either nutrients, a complex carbon source, a reducing medium, or surfactant. Additionally, he presented information regarding the aerobic treatment of Hudson River sediments that had been previously dechlorinated in the environment. The addition of minimal medium to Hudson River sediment slurries was shown to increase the rate and magnitude of anaerobic dechlorination. Addition of trace metals (at concentrations of less than 0.02 ppm) also increased the rate of PCB dechlorination. The addition of the minimal medium and a chemical reducing agent (cysteine hydrochloride) resulted in different patterns of dechlorination, indicating growth of different microbial populations. Dechlorination was shown to occur in numerous, aged PCB-contaminated sediments, including those from the Hudson River, the South Glens Falls dragstrip (amended with Hudson River sediment), and Woods Pond. Aerobic treatment of Hudson river sediments that had previously undergone extensive dechlorination of the higher-chlorinated congeners (>85% mono- and dichlorobiphenyl remaining) resulted in greater than 70% reduction of PCB concentration after one day of treatment.

Dawn Foster reported on the Sheboygan River and Harbor Remedial Investigation/ Feasibility Study Program. In the first phase of this program, the contaminants of concern were identified to include PCBs and eight metals. This investigation led Tecumseh Products Company (one of three potentially responsible parties) to propose an Alternative Specific Remedial Investigation, which consists of pilot-scale studies to investigate various bioremediation alternatives and bench-scale studies to investigate other alternatives. The primary objectives included: evaluation of the potential to enhance biodegradation within a confined treatment facility (CTF); evaluation of in situ armoring and the anaerobic biodegradation of PCBs associated with these capped sediments; evaluation of mechanical dredging methods and monitoring of the impact of these activities on the water column; and bench-scale tests of other innovative technologies. The pilot-scale CTF constructed for the enhancement studies has a capacity of 2500 cubic yards and has four cells that can be used to test various treatment scenarios. In addition, various schemes will be examined for the treatment of the cell effluent. Bench-scale studies are currently underway at the University of Michigan that will provide information for the design of CTF enhancement studies by the addition of various amendments. Armoring of in-place sediments was accomplished by placing a geotextile material over the in-stream sediments followed by successive layers of bank run off material (6 inches), another geotextile layer, and a final layer of stones and gabions. Sampling ports through these layers will allow for the monitoring of the natural biodegradation process.

Questions and comments during the PCB discussion sessions encompassed a number of issues; some related and others very specific and unique. The topics dealt with in some detail, in order of their deliberation, included the following.

Development of a Sediment Testing Protocol. The speakers described many laboratory experiments which all have a common theme - that of measuring biodegradation of PCB compounds in sediment systems, and amending these systems to enhance rates of transformation. However, no standardized testing protocol exists to facilitate testing by other scientists or engineers for assessing the feasibility of bioremediation at other sites. It was suggested that such a protocol be developed, and could be used as a guideline, as opposed to a methods document, simply because of the continuously developing nature of this science, and the rapidly expanding data base. It was mentioned that the EPA's Biosystems Technology Development Program is currently developing a testing protocol for contaminated aerobic soils, and that much could be learned from this other effort in developing one for PCB-contaminated sediments. Such a document would be of value to Regional (Superfund) scientists and engineers who must evaluate and oversee bench-scale and pilot-scale studies, and to Remedial Action Plan coordinators who must develop remedial options for contaminated sites.

Deposition of Other Contaminated Sediments on Armored Material. Several questions were asked concerning the integrity of the armored sediments and/or the possibility of re-sedimentation of other contaminated sediments on the armored areas, necessitating re-armoring of the Sheboygan sediments. In response, the pros and cons of armoring were discussed. Basically, armoring can only be evaluated as an option in areas where (1) dredging of sediments is not necessary, and (2) high currents will not disturb the armoring material. In the case of the Sheboygan sediments, re-sedimentation of contaminated sediments should not occur because of the elimination of the source (basically, the sediments are the current source).

Bioaccumulation of PCBs in Lower Organisms. It was asked whether the trends in bioaccumulation of PCBs in lower organisms should coincide with those found in higher organisms (i.e., fish). The discussion that followed addressed the issues of both chemical phase distribution and chemical metabolism. From a thermodynamic standpoint, the potential to bioaccumulate (normalized to organism lipid content) in higher and lower organisms is the same. Factors limiting the kinetic uptake and depuration of these compounds in these organisms, however, may differ. In addition, the ability of some organisms to metabolize these compounds may result in body burdens less than those found in other organisms that can not metabolize them. The thermodynamic potential, the limiting kinetic factors (including such things as migratory patterns), and the organism's ability to metabolize the compounds must all be factored into the observed environmental bioaccumulation of these compounds.

Natural Substrates of the Aerobic Pathways of PCB Degradation. Because the aerobic degradation of PCBs occurs through a cometabolic pathway, a question was raised concerning the identity of the natural substrates for which this metabolic pathway exists, and the natural distribution of the organisms containing the responsible enzymes. The point was raised that, in natural systems, either the concentration of the final electron acceptor and/or carbon source is sometimes the growth limiting factor, not the energy source, per se. It was suggested that diagenetic humic material, which contains a considerable amount of aromatic structure and already contains fairly reduced carbon, is the natural substrate. This would account for the relatively ubiquitous distribution of PCB-degrading organisms in the environment.

Mass Balance Accounting of PCBs in the Environment. Part of the problem in identifying natural PCB degradation is that the historical mass loadings of PCBs into various river and harbor systems is not known, and therefore mass balance estimates on losses cannot be easily made. From sampling exercises on the Hudson River between the mid '70s and '80s, it appears that half of the PCBs estimated to be present from the first sampling period (approximately 500,000 lbs) have been lost from the system. It was suggested that long-term sampling programs be initiated in areas where physical transport mechanisms are minimized and where good mass balances can be measured to get a better idea of the extent to which natural biological decay processes are occurring. Such studies may be possible using existing confined disposal facilities.

Effects of Toxic Metals on PCB Degradation Rates. In most of the Areas of Concern, when PCBs are present, heavy metal contamination coexists to some extent. Very little information is available, however, concerning the toxicity of various metal species to PCB degraders. Also, it should not be assumed that high concentrations of metals will decrease degradation rates or are responsible for low degradation rates. Speciation and redox state is important, as well as how the metals are associated with the sediment material. It was generally agreed that metal toxicity should be addressed to some extent in bench-scale studies as metal toxicity will be very site-specific.

Questions of Scale-Up and Number of Pilot Studies. The basic question "where do we go from here" was asked. Do we start new studies, and at what level of effort should these studies proceed (i.e., bench, pilot)? The general consensus of the group seemed to be that currently we are working with a fairly small data base. Several studies have shown positive results, and several have so far been negative. All the effects of, and relationships among, the various controlling factors are not known; hence, the clearest path to site-specific optimization is not always obvious. It was generally agreed that as the results of more studies become available, biological treatment technologies will be refined, and the limits of these technologies will become clearer. Because each level of scale-up involves different aspects of treatability, the design of more pilot-scale studies, based on the results of bench-scale studies was suggested.

Acceptable Clean-Up Concentrations. A concern was raised regarding the fact that there is generally good success at high PCB concentrations (> 50 ppm) and poor success at low concentrations (< 50 ppm): Whereas, even single digit ppm concentrations of PCBs in sediment (dry weight basis) may relate to significant concentrations in fish species. The suggestion was made that engineered systems should focus on these lower concentrations where other chemical or physical destruction technologies do not appear to be economically feasible as final remediation remedies. The point was raised that this phenomenon (concentration dependence) may be largely a consequence of reaction kinetics (including mass transfer limitations) or microbial induction. Both of these causes can be assessed at the bench-scale level.

2.3 Polycyclic Aromatic Hydrocarbons

Patricia L. Van Hoof
University of Georgia
Athens, GA 30613

Polycyclic aromatic hydrocarbons (PAHs) are a major class of environmental contaminants that are byproducts of 1) burning of fuel, 2) generation of synthetic fuels from fossil fuels, and 3) wood treatment. This class of compounds exhibits a wide range of toxicity, hydrophobicity, and recalcitrance in aquatic systems. While biodegradation of low-molecular-weight PAHs by a wide variety of microorganisms is well documented, there is limited information on the microbial utilization of the more recalcitrant and toxic PAHs consisting of four or more fused rings. In order for bioremediation to be considered a viable treatment of PAH-contaminated sites, the organisms, the processes, and the environmental conditions necessary for the degradation of these compounds must be identified. The speakers in this session address this challenge.

Carl Cerniglia discussed the use of a Mycobacterium sp. in the remediation of PAH wastes. The pyrene-degrading bacterium was isolated by direct enrichment from sediment taken from an oil field in Port Aransas, Texas. The bacteria were found to be quite versatile, degrading both low and high-molecular-weight PAHs possessing up to five fused rings. In microcosm studies, the organism was able to compete against bacteria indigenous to a variety of environments (freshwater, marine, pristine, polluted), and enhanced the mineralization of PAHs. He noted that the rates of degradation were dependent on compound structure and site history. Lower-molecular-weight PAHs were degraded faster than higher-molecular PAHs, and contaminated sites (freshwater and estuarine) demonstrated higher degradation rates than pristine ones. Low levels of organic nutrients were reported to be necessary to initiate growth, suggesting the degradation process is co-oxidative. In addition, inorganic nutrient supplements (N and P) enhanced PAH degradation. He pointed out that the mechanism of oxidation is unique as the Mycobacterium has both mono-and dioxygenases to catalyze PAH degradation.

H.J. van Veen addressed the problem of contaminated sediments (oil, PAHs, and metals) in the Netherlands. These sediments are of particular concern not only because of their environmental impact, but also because of the need for frequent dredging of the country's many waterways. The speaker gave a survey of the current state of full-scale sediment remediation and the development of biological treatment. Volume reduction of dredged sludge consists of a combination of two techniques: hydrocyclones and dewatering. The "heavier" sand fraction is separated from the finer and often more highly-contaminated fraction using a hydrocyclone, which utilizes tangential flow and centrifugal force. He stressed that this operation will not benefit cleanup of dredged sediment consisting mainly of fine particles or with a high organic carbon content. After separation, the fines fraction is dewatered with a belt press, filter press or decanter using polyelectrolytes. The results of a number of practical cases demonstrate that this type of treatment is fairly successful; however, a couple of problems were pointed out. First, the composition of the sludge often deviates from that expected based on preliminary investigation. Second, in some cases, the sand fraction has high PAH concentrations. When all size fractions are contaminated, a sludge can only be treated intensively in a bioreactor. Whereas sludges that can be fractionated are more effectively treated extensively, i.e. the sand fraction can be land-farmed and the fine fraction can be considered a waste liquid and treated in an aeration basin. Intensively treating PAH-contaminated sediments was shown to be faster than the extensive treatment of the fractionated material; however, over longer time periods both processes were equally effective. He noted that practical considerations, such as material volume, rates of degradation, space and cost will determine whether intensive (bioreactors) or extensive processes are required.

John Rogers presented the work of James Mueller and colleagues on the microbial degradation of PAHs and their relevance to bioremediation. The efforts of this group have been focused on the isolation of microorganisms capable of degrading high-molecular-weight (HMW) PAHs. Mixed bacterial cultures capable of utilizing HMW PAHs as sole sources of carbon and energy for growth have been isolated. He described how they are making use of these microorganisms in a recently developed tri-phasic sequential treatment system for the remediation of creosote and similarly contaminated soil and water. Under a Federal Technology Transfer Act, they were able to transfer some of their biotechnology to an engineering firm which provided separation technology. The steps in this remediation process include conventional soil washing, membrane extraction, and biodegradation of extracted pollutants. Each step in this process results in the volume reduction of contaminated material. Depending on the type of starting material, soil washing can reduce the contaminated volume to as little as 10% of the initial value. While the soil washing process reduces the volume of material requiring treatment, the process generates large amounts of contaminated wash water along with accumulated fine particles. To address this problem, reverse osmosis hyperfiltration through porous stainless steel membranes is applied to dewater and concentrate pollutants. While the effectiveness of this system on soil wash water is currently being evaluated, they have demonstrated that >99% of creosote components present in contaminated groundwater are removed. The speaker emphasized the potential capabilities of the membranes to : 1) fractionate mixtures of chemicals to increase degradation efficiencies or reduce toxicity (e.g. metals), and 2) recycle surfactants used in soil washing. Finally, the wash water is fed to specially enriched microbes housed in continuous flow bioreactors. The ability of these organisms to degrade artificial creosote mixtures has been demonstrated. Field demonstrations of this sequential treatment system are currently being evaluated.

John Glaser discussed the use of white rot fungi (Phanerochaete chrysoporium and P. sodida) to degrade a variety of target pollutants, including PAHs, in a variety of media. Phanerochaete sp. grow quite rapidly on decaying wood. Consequently, this fungus possesses great potential to degrade aromatic components of hazardous waste, based on its ability to degrade lignin. The enzymes of this fungus are extracellular, extremely strong oxidizers, largely non-specific, and not commonly found in other organisms. The speaker pointed out that the non-specificity of these enzymes provides this organism with a capacity to degrade a wide range of substrates (e.g. PAHs, PCBs, pesticides, and dyes). Two types of media have been recently tested, liquid treatment using rotating contactors, and soil treatment. The liquid treatment shows promise and is currently under pilot-scale evaluation to better control pH and the mixing domain within the reactor. The application of wood chips inoculated with Phanerochaete chrysosporium and P. sodida to soil contaminated with pentachlorophenol resulted in 82% and 85% reduction, respectively, after 46 days. He noted that this fungus does not grow naturally in soil and is non-pathenogenic to plants and animals. The required field conditions (e.g. target compound and oxygen levels, temperature, reactor configuration) for optimal biodegrading activities are currently being investigated.

2.4 Metals

Paulette B. Altringer
U.S. Bureau of Mines
729 Arapeen Drive
Salt Lake City, Utah 84108

To summarize the metals session, a brief overview of the Bureau of Mines and the related areas of research it is involved with are given. This is followed by a summary of the session presentations which addressed the research ongoing at the Bureau of Mines and associated research at the Department of Energy's Idaho National Engineering Laboratory (INEL) related to this area and the possible application of this research to the remediation of inorganic-contaminated sediments. The presenters stressed that all the remediation answers to metal-contaminated sediments do not currently exist, but rather that some interesting possibilities in this area, analogous to other current ongoing research in the field of mining and metallurgy, show potential applicability.

The Bureau of Mines was established in 1910 as a Federal Agency in the Department of the Interior. The Bureau is a relatively compact and mature agency by Washington standards. The Bureau employs 2,200 people and is organized into three main directorates: Finance and Management, Information and Analysis, and Research. The research component of the Bureau is the largest element of the Bureau's overall program, employing about 1,300 people, with nine dedicated laboratories located across the country. The Bureau is different from most Federal agencies in that the Bureau performs its research in house instead of contracting it out: the one exception to the inhouse research is a healthy program in concert with the Department of Energy's Idaho National Engineering Laboratory (INEL), where two of the sessions speakers (Arpad Torma and Peter Pryfogle) are employed. Bureau of Mines research is targeted at three main areas: (1) Health, Safety, and Mining Technology, (2) Minerals and Materials Science, and (3) Environmental Technology. The Bureau is responsible for a number of major activities related to the minerals industry. Among these responsibilities is the performance of research on mining and metallurgical technologies. This research has led to a number of major developments that have benefitted the industry and the people of this country.

The 75 years of research and technical experience have also resulted in the Bureau becoming the government's principal expert in the area of selective extraction of inorganic ions. This includes technology to extract low concentrations of metals and other inorganic materials from their host environment, solid or liquid. This capability includes another relatively new technique: "biotechnology", which is the use of bacteria to treat metal-contaminated solids and liquids. The "newness" really refers to the use of biotreatment, under controlled conditions, as part of a metallurgical treatment process; nature has employed this approach for millions of years. These mechanisms have been and are being employed in the minerals industry on a daily basis as part of leaching operations, for example, for the production of copper. Bacteria were enhancing copper leaching long before man was aware of the bacterial leaching interaction. This same basic mechanism, operating on an uncontrolled basis, contributes to acid drainage from coal mines. Leaching inorganics from solids can be enhanced using bacteria and, alternatively, other types of bacteria can precipitate metals and destroy toxic inorganic processing chemicals in solutions. Both aerobic and anaerobic microorganisms are involved in these processes. This biotechnology can be applied beyond the minerals industry to the field of Superfund and RCRA remediation. Biotechnology often produces a lower level of contaminants in the treated material than is possible to achieve using conventional physical and chemical treatments. In some cases, combinations of biotechnical, chemical, and beneficiation techniques might be the only way to achieve the low level of contaminants in treated materials required by environmental legislation.

Almost half of the Bureau researchers are involved in research that can be generally described as "metallurgical" in nature. Research on extractive processes -- selective capture of one or more elements from host materials that are either natural or recycled materials --represents a large component of this part of the Bureau's program. Four of the nine Bureau of Mines laboratories have ongoing projects involving bioextraction of metals and INEL is actively involved in associated biotechnical research.

In the first presentation, I presented the Salt Lake City Research Center's work involving the bioaccumulation of elements such as arsenic, cadmium, lead, mercury and selenium, from solution using both viable bacteria and biomass immobilized in what we call "BIOFIX" beads. In addition, the destruction of cyanide in process streams using viable bacteria was discussed. This research may have direct application to inorganics removal from sediment-associated waters. This research is being expanded at the Salt Lake Research Center to include bioleaching of inorganic contaminants from sediments and mine tailings using bacteria. The nature of these low-level, high-volume wastes makes most processing options extremely expensive. Bacterial leaching in situ or on heap pads may provide an answer to this wide-spread problem.

Hank Edenborn, from the Pittsburgh Research Center, reported on biotechnology for the remediation of acid mine drainage from coal mines. He described the use of "wetlands" technologies for this purpose, and how this technology may be directly applicable to sediment remediation. He also described the use of bactericides to inhibit bacterial leaching in the event that sediments should have to be dredged from waterways immediately, but could not be treated for a period of time. Bactericides would prevent the biologically mobilized inorganic contaminants from leaching from the sediments and entering the surface or groundwater during storage prior to treatment.

Betty Baglin reported on research at the Reno Research Center on the bacterial leaching of manganese, platinum and gold ores as a means of improved leaching technology. She related the applicability of this work to remediation of contaminated sediments.

The Department of Energy's Idaho National Engineering Laboratory (INEL) has been studying the mechanisms of bacterial metals removal from solids and the application of these results in conjunction with the Bureau of Mines. Arpad Torma from INEL discussed biochemical possibilities of inorganic sediment remediation and Peter Pryfogle provided information on INEL's research capabilities.

Robert Lambeth from the Spokane Research Center presented information on linking biological and hydrogeochemical mechanisms (models) of sediment leaching. This is a complex research area and involves (1) field and laboratory data requirements, and (2) computer model requirements. The Bureau's Spokane Research Center has been using geochemical computer models to interpret hydrogeochemical mechanisms of mine tailings and sediment leaching. Recently, personnel from the Spokane and Salt Lake City Research Centers conducted a joint sampling trip to a copper-gold tailings impoundment in Washington State in the hope of linking biological to hydrogeochemical mechanisms of inorganic leaching. Currently a "cook-book" for predicting contaminant fate at new sites does not exist, but rather the presentation focused on an approach to developing techniques for predicting contaminant fate at new sites based upon knowledge gained from sites that have already been studied.

The research presented during this session and described in the abstracts has great potential for biotreatment of inorganics in sediments. Successful development of the biotechnical techniques may provide on-the-shelf technology for environmental problems untreatable with conventional technology today.

2.5 Conclusions

During the past decade, a great deal has been learned regarding biological processes that act to transform or mineralize anthropogenic pollutants, including those discussed in detail during the Workshop. The ability of microorganisms to degrade or transform chlorinated organic compounds such as the PCBs, polycyclic aromatic hydrocarbons (PAHs), and metal species is now well documented. Yet, an understanding of how these mechanisms function in environmental systems, to the extent that we can consistently optimize them for bioremediation purpose, is not totally understood. Two general areas in which information gaps can be grouped for the problem at hand include: (1) The specific processes and mechanisms controlling observed degradation rates and patterns, and (2) issues associated with extrapolation of bench-scale studies to pilot or full scale field studies. A majority of the specific questions and issues that were discussed during the workshop fell into these two areas.

Clearly, a significant amount of information on the biological transformations of pollutants already is known from process research. Much of this research is at the phenomenological level. The results have helped identify empirically, or allude to mechanistically, the interactions among microorganisms, pollutants, and the sedimentary and aqueous media in which they exist. These interactions can be rather complex, even for rather simple systems, such as the transformation of a single compound by a pure microbial culture in an homogeneous solution. In this simple system, characterization of the degradation process requires an understanding of nutrient and growth requirements, the kinetics of transformation reactions, degradation pathways, pollutant concentration dependencies, effects of alternative substrates and electron acceptors, temperature dependencies, the effects of metabolic inhibitors, and in some cases, the effects of varying carbon sources. The additional complexity associated with investigating the same microbial decay process in natural or manipulated sediments is obvious. Additional consideration must be given to organic and inorganic inhibitor availability, combined inhibitory effects, pollutant bioavailability and the kinetics of this availability, and microorganism competition or cooperation of the indigenous bacteria. Although a complete understanding of how these processes interact at specific sites would result in the most obvious approaches to treatability, a comprehensive understanding may not always be necessary. In many cases, biological treatment efficiency may be significantly enhanced (above background levels) by regulating a few critical factors limiting activity. These factors must be identified at the bench-scale level through simple process studies. In many cases, differences in these controlling factors are reasons for the site (or sediment) specific nature of biological treatability successes. Clearly, while much is known, a better definition of the chemical, physical, and biological processes (or factors) controlling observed transformation rates and pathways in natural and manipulated sediments will enhance the frequency and degree of bioremediation successes.

On the other hand, the extrapolation of results from bench-scale studies to pilot or full scale studies is largely untested for remediation of sediments contaminated with the pollutants of concern. Examples of extrapolation were presented during the Workshop. They include technologies developed for the separation or removal of metal species from mine tailings or drainage, and other bioremediation technologies evolving the remediation of soils or liquid waste streams containing organic contaminates. Also, applied bioremediation may take many forms, from simple low energy in situ (in place or CDF) systems to highly engineered, high energy systems. Each form has its own list of design factors or parameters that must be considered when optimizing treatment. As more field-scale efforts become realities, however, systems obviously will be refined, and a clearer connection between bench-scale methods (and treatment efficiencies) and applied field scale processes will become evident.

Abstracts

3 Areas of Concern
4 PCBs
5 PAHs
6 Metals

Appendix I - Program
Appendix II - List of Attendees

List of Figures

2.1.1 Areas of Concern
3.1.1 Buffalo river area of concern location map
3.2.1 Vicinity map, Fields Brook
3.2.2 Fields Brook site map
3.2.3 Design investigation sequence
3.5.1 Location of the Saginaw River/Bay Area of Concern
3.5.2 Spatial distribution of PCB in surficial sediments of the Saginaw River
3.5.3 Vertical distribution of PCB in sediments near Bay City WWTP
4.2.1 Capillary gas chromatograms showing the anaerobic dechlorination of 700-ppm Aroclor 1242 after 16 weeks of incubation
4.2.2 Decrease in the average number of chlorines by position at three Aroclor 1242 concentrations as a result of dechlorination by Hudson River microorganisms
4.2.3 Effect of incubation temperature on the dechlorination of Aroclor 1242 by Hudson River microorganisms
4.2.4 Decrease in the average number of chlorines for four Aroclors as a result of dechlorination by Hudson River microorganisms
4.2.5 Comparison of the dechlorination rates of 3,3',4,4'-CB, 2,3,3',4,4'-CB,and selected tetra- and penta- CBs present in Aroclor 1242
4.5.1 Acceleration of the reductive dechlorination of PCBs upon addition of nutrients (8 week timepoint). A) autoclaved control; B) includes distilled water; C) includes RAMM minimal medium. All samples contain 500 ppm PCB (70% Aroclor 1242, 20% Aroclor 1254, 10% Aroclor 1260) inoculated with sediments from the Hudson River
4.5.2 Dechlorination patterns observed under different conditions (18 week timepoint). A) autoclaved control; B) includes RAMM (pattern M); C) includes RAMM + cysteine hydrochloride at 1 g/L (pattern Q)
4.5.3 Dechlorination of endogenous PCB contamination in Hudson River sediments with sediments with RAMM (18 week timepoint) A) autoclaved control;B) experimental
4.5.4 Dechlorination of endogenous PCB contamination in South Glens Falls soil with 25% Hudson River sediment (23 week timepoint). A) autoclaved control; B) experimental
4.5.5 Sequential Anaerobic/Aerobic treatment of endogenous PCB contamination in Hudson River sediments. A) Aroclor 1242; B) environmentally dechlorinated Aroclor 1242; C) B+ aerobic treatment (1 OD cells; 1 day timepoint)
5.1.1 The structures and chemical and toxicological characteristics of polycyclic aromatic hydrocarbon
5.1.2 Schematic representation of the environmental fate of polycyclic aromatic hydrocarbons
5.1.3 Major pathways of bacterial oxidation of polycyclic aromatic hydrocarbons
5.1.4 Photograph of Mycobacterium sp. colonies on MBS agar containing low-levels of nutrients and coated with pyrene. The clear zones around the bacterial colonies indicate pyrene utilization
5.1.5 Mineralization of naphthalene, phenanthrene, pyrene, fluoranthene, 1-nitropyrene, 6-nitrochrysene and 3-methylcholanthrene by the Mycobacterium sp
5.1.6 The pathways utilized by the Mycobacterium sp. for the oxidation of pyrene
5.1.7 The pathways utilized by the Mycobacterium sp. for the oxidation of naphthalene
5.1.8 The pathways utilized by the Mycobacterium sp. for the oxidation of fluoranthene
5.1.9 The pathways utilized by the Mycobacterium sp. for the oxidation of 1-nitropyrene
5.1.10 Mineralization of phenanthrene, 2-methylnaphthalene, pyrene and benzo[a]pyrene in microcosms from De Gray Reservoir sediments and water with and without Mycobacterium inoculation
5.3.1 Tri-phasic treatment approach
5.4.1 Hydrocyclone
5.4.2 Hydrocyclone results
5.4.3 Volume reduction by dewatering
5.4.4 Intensive versus extensive treatment (Geulhaven Rotterdam)
6.1.1 CN removal in single-pass 3-column trickling reactor
6.1.2 Metal sorption using BIO-FIX beads
6.1.3 Conceptual configuration for bioleaching sediments
6.3.1 Shake-flask bioleaching of Three Kids ore, 5 pct. factory molasses
6.3.2 Column bioleaching of Three Kids ore, 3 pct. food-grade molasses

List of Tables

3.1.1 Great Lakes water quality agreement impairment indicators
3.1.2 Summary of impairments, causes and sources
3.2.1 Priority pollutants found in sediment at the Fields Brook site
3.2.2 ARI - Main stem river sediment samples selected parameters - statistical data presented on dry weight basis(locations 12201 through 20502)
4.2.1 Maximal observed dechlorination rates (means with standard deviations) of the Aroclors tested for microorganisms collected from the two sites
4.5.1 Effect of RAMM components on dechlorination rate
5.4.1 Results of practical hydrocyclone applications
5.4.2 Results of biodegradation for various sediment samples
6.3.1 Shake-flask bioleaching of Manganese ores
6.3.2 Abiotic leaching of Three Kids ore with organic acids
6.3.3 Column and heap bioleaching of Three Kids ore
6.3.4 Stillwater ore minerals
6.3.5 Bio-oxidation of stillwater flotation concentrate
6.3.6 Cyanidation of bioleached and As-received stillwater concentrate

 

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