Dechlorination of Persistent Organic Pollutants with Palladized Magnesium: Dioxins and PCNs
Linda Rauch, University of New Hampshire, Durham, NH

Developments in Bioremediation of Soils and Sediments Polluted with Metals and Radionuclides:  2. Field research on Bioremediation of Metals and Radionuclides
Henry H. Tabak, US EPA, Cincinnati, OH

Innovative Systems for Dredging, Dewatering or for In-Situ Capping of Contaminated Sediments
Jerry Darlington, CETCO, Arlington Heights, IL

Scaling Contaminant Distributions and Contaminant Processes in Sediments
Peter Adriaens, The University of Michigan, Ann Arbor, MI

Issues of Biostimulation, Bioaugmentation and Bioavailability in the Remediation of a Coal Tar Soil
Joseph Pignatello, Connecticut Agricultural Experiment Station, New Haven, CT 

Entombment of Pure-Phase Tar Impacted Sediment in New Bedford Harbor: A Case Study
Timothy Condon, Lightship Engineering, LLC, Plymouth, MA

Pathways of Congener-Specific PCB Dechlorination by Palladized Magnesium

Emese Hadnagy, University of New Hampshire, 35 Colovos Rd., Durham, NH, 03824, Tel: 603-862-1197, Fax: 603-862-3957, Email: ehadnagy@unh.edu
Kevin H. Gardner, Ph.D., P.E., University of New Hampshire, 35 Colovos Rd., Durham, NH, 03824, Tel: 603-862-4334, Fax: 603-862-3957, Email: kevin.gardner@unh.edu
Jean C. Spear, University of New Hampshire, 35 Colovos Rd., Durham, NH, 03824, Tel: 603-862-1445, Fax: 603-862-3957, Email: jeannie.spear@unh.edu
Irina Calante, University of New Hampshire, 35 Colovos Rd., Durham, NH, 03824, Tel: 603-862-1197, Fax: 603-862-3957, Email: icalante@unh.edu

PCB contamination in sediments remains a significant problem in many rivers, harbors, and estuarine areas in the US and around the world, and continues to provide PCBs to the food chain despite the long ban on PCB manufacture and use. In this work, rapid degradation of single PCB congeners (BZ 3, 170 and 197) by palladium-coated magnesium (Mg/Pd, 99.9%/0.1% by weight) has been demonstrated in pure solvent systems (10% methanol in distilled water). More than 90% of the initial PCB was removed in 10 to 25 minutes. No degradation byproduct was observed in these experiments. The behavior of biphenyl, the expected degradation byproduct, was also investigated in the same pure solvent system. Rapid removal of biphenyl was observed in these studies (97% removal in 10 minutes). It was hypothesized that biphenyl was volatilized or adsorbed to the Mg/Pd surface. The last two hypotheses are currently under investigation and recent work on closing the mass balance will be presented.

Understanding the fundamentals of the dechlorination pathways of single PCB congeners, including the relative resistance of positional isomers towards degradation, is essential to be able to better predict treatment efficiencies in more complex sediment systems. Preliminary experiments in PCB-contaminated sediments from the Housatonic River, New Bedford Harbor, and Hunter’s Point indicate that there is PCB mass reduction occurring by Mg/Pd at a slower rate, over a period of a few days. Contaminant degradation by Mg/Pd is a potential promising technology that could effectively remediate PCB-contaminated sediment to very low levels with an in-situ process.

Dechlorination of Persistent Organic Pollutants with Palladized Magnesium: Dioxins and PCNs

L. Rauch, University of New Hampshire, Gregg Hall Rm. 330, 35 Colovos Rd., Durham, NH, 03824, Tel: 603-862-1197, Fax: 603-862-3957, Email: linda.rauch@unh.edu
J.C. Spear, University of New Hampshire, Gregg Hall Rm. 222, 35 Colovos Rd., Durham, NH, 03824, Tel: 603-862-1445, Fax: 603-862-3957, Email: jeannie.spear@unh.edu
K.H. Gardner, University of New Hampshire, Gregg Hall Rm. 336, 35 Colovos Rd., Durham, NH, 03824, Tel: 603-862-2206, Fax: 603-862-3957, Email: kevin.gardner@unh.edu

A significant issue in the field of contaminated sediments is the presence of contamination with persistent organic pollutants (POPs) such as polychlorinated biphenyls (PCBs), polychlorinated dibenzo-p-dioxins (PCDDs or Dioxins), polychlorinated dibenzofurans (PCDFs), and polychlorinated naphthalenes (PCNs).  These contaminants pose a serious public health concern as a result of their highly toxic nature.  POPs are ubiquitous in the environment on a global scale and have been shown to bioaccumulate in animals.   

A great deal of work has been undertaken by researchers studying and developing treatment approaches for PCBs.  To date, a lesser degree of effort has focused on some of the other POPs such as Dioxins or PCNs.  In particular, PCNs continue to be a little studied group of environmental toxins.  Yet these compounds have been found to be equal if not more significant contributors than PCBs to toxicity levels at certain contaminated sites. 

Previous work at UNH has shown that PCBs can be successfully dechlorinated by reaction with palladized magnesium.  This presentation will focus on recent work investigating the reactivity of palladized magnesium with Dioxins and PCNs in pure solutions as well as in contaminated sediments from the Passaic River.

Developments in Bioremediation of Soils and Sediments Polluted with Metals and Radionuclides:  2. Field research on Bioremediation of Metals and Radionuclides

Henry H. Tabak, US EPA, ORD, Environmental Research Center, National Risk Management Research Laboratory, Land Remediation and Pollution Control Division, Cincinnati, OH 45268, Tel: 513-569-7681, Fax: 513-569-7105, Email: tabak.henry@epa.gov
Terry C. Hazen, Lawrence Berkeley National Laboratory, Virtual Institute for Microbial Stress and Survival, Earth Sciences Division, Ecology Dept. Berkeley, CA, Tel: 510-486-6223, Fax: 510-486-7152, Email: tchazen@lbl.gov

The last 15 years have seen an increase in the types of contaminants to which bioremediation is being applied, including solvents, PAHs and PCBs.  Now, microbial processes are beginning to be used in the cleanup of radioactive and metallic contaminants of soils and sediments.  Microorganisms can interact with these contaminants and transform them from one chemical form to another by changing their oxidation state through the addition of (reduction) or moving (oxidation) of electrons.  In some bioremediation strategies, the solubility of the transformed metal or radionuclide increases, thus increasing the mobility of these contaminants and allowing them to more easily be flushed out from the environment. In other strategies, the transformed metal or radionuclide may precipitate out of the solution, leading to immobilization. Both kinds of transformations present opportunities for bioremediatioin of metals and radionuclides in the environments - either to immobilize or to accelerate their removal. Metal contamination of soils and sediments is especially problematic because of the strong adsorption of many metals to their particles.  Due to the difficulty of desorbing metal contaminants, some traditional remediation methods, simply immobilize metals in contaminated soils, by the addition of cement or chemical fixatives, by capping with asphalt, or by in-situ vitrification.  Alternatively, soils are often isolated by excavation and confinement in hazardous waste facilities.  Although rapid in effect, both of these options are expensive and destroy soil’s future productivity. The success of soil washing and pump-and-treat technologies to remove metals is severely limited by the slow desorption kinetics of adsorbed metals, with the result that additional additives (acids, chelates and reductants) are often used to promote metal transfer to the aqueous phase. These agents improve cost effectiveness but may introduce further harmful chemicals.

A primary strategy of bioremediation is the use of similar metal-immobilizing agents in conjunction with soil washing, with advantage that they pose no known environmental threat themselves. Biopolymers have been discovered that bind metals with high affinity and travel    relatively unimpeded through porous medium.  Certain microorganisms transform strongly-adsorbing metal species into more soluble forms and plants are being recruited that act as self-contained pump-and-treat systems.  Other methods employ enzymatic activities to transform metal species into volatile, less toxic or insoluble forms. Techniques for soil bioremediation are usually designed to be used in-situ, lowering costs; they avoid the use of toxic chemicals, and in nearly all cases, the soil structure and potential for productivity are preserved.

The first review paper, presented at the AEHS 2005 West Coast Conference provided a detailed information on the metal-microbe interactions and the application of these interactions for bioremediation of the metal contaminated soils and sediments. The paper described:  (1) microbial processes effecting bioremediation of metals and radionuclides and influencing their toxicity and transport (metal biotransformation, metal biosorption, metal bioaccumulation and biomineralization via microbially-generated ligands - degradation and synthesis of organic ligands of toxic heavy metals); and (2) microbial mechanisms involved in bioremediation of metal and radionuclide contaminated soils and sediments (dissimilatory metal reduction, microbial metabolism of iron bacteria, microbial metal leaching, microbial polymers and their use in bioremediation of metal contamination and microbial metal volatilization).

This paper will provide a review of published research on field studies on bioremediation of metal and radionuclide contaminated soils and sediments.  The paper will  (1) cite examples of field research and cases of field in-situ bioremediation of metal and radionuclide contaminated soils and sediments; (2) discuss the role of phytoremediation in the treatment of metal and radionuclide contaminated soils; and (3) provide information on the use and field-scale application of surfactants in the treatment of metal and radionuclide pollution of soils and sediments.  The following metal-microbe interactions that impact bioremediation of metal contamination in soils and that can be applied to field-scale biotreatment will be discussed:

(1) biotransformation (bioreduction and biooxidation); (2) bioaccumulation and biososrption; (3) biodegradation of chelators; (4) biosurfactants and biologically-assisted soil washing; (5) volatilization; and (6) biotreatment trains and natural attenuation. The paper will also discuss research on the treatment of metal contaminated soils, wetlands and mine areas with the use of biosolids, by providing information on (1) in-situ soil treatments to reduce phyto- and bioavailability of metals and (2) the use of biosolids to restore metal contaminated mining areas impacted by metal tailings.

Innovative Systems for Dredging, Dewatering or for In-situ Capping of Contaminated Sediments

James T. Olsta, Technical Manager, CETCO, 1500 West Shure Drive, Arlington Heights, IL 60004, Tel: 847-392-5600, Email: jim.olsta@cetco.com
Jerry Darlington, Technical Director, CETCO, 1350 West Shure Drive, Arlington Heights, IL 60004, Tel: 847-818-7214, Email:jerry.darlington@cetco.com

Objectives

The environmental remediation community is seeking innovative ways to conduct remediation of contaminated sediments.  

Challenge

Traditional dredging practices create challenges in dewatering, finding suitable disposal facilities, as well as, public concern over resuspension of contaminants.  In-situ capping (either in place of dredging or for capping residual contaminants) can be limited by concerns regarding navigation, uniform cap placement, biointrusion and geotechnical stability.

Solution

Innovative dewatering, solidification and stabilization practices, can be provided to improve the economics of dredging. A potential solution for many in-situ capping concerns is the use of a reactive material cap.  A reactive material cap could greatly reduce the thickness required for the cap compared to conventional sand caps.  Various reactive materials (e.g., activated carbon, organoclay, zero valent iron) are used for wastewater and groundwater treatment and may be applicable to in-situ capping.  Activated carbon and organoclay effectively adsorb many organics.  Zero-valent iron reduces organic solvents into less toxic byproducts.

There are several systems that could be used for in-situ capping with reactive materials.  One is a reactive material filled geotextile mat.  A reactive material mat would have several advantages over loose placement of reactive materials, including:

·         uniform and verifiable mass per area placement of reactive or absorptive material,

·         ability to mix reactive or absorptive materials in defined proportions,

·         geotextiles provide separation of the reactive material from the contaminated sediment and cover material,

·         geotextiles provide a barrier to biointrusion,

·         multiaxial strength of the geotextiles provides resistance to uplift and differential settlement,

·         and geosynthetic reinforcement provides stability on sloped areas.

Another reactive material system include utilization as of organoclay as a permeable reactive barrier in either a horizontal or vertical configuration to utilize the significant hydrocarbon adsorption capacity.

Results

At the Anacostia River Demonstration Project a coke-filled geotextile mat was successfully constructed and deployed.  A barge with crane was used to deploy the material.  Other deployment methods have also been used for geosynthetics from shoreline and would be applicable to a reactive material mat.

Scaling Contaminant Distributions and Contaminant Processes in Sediments

Peter Adriaens, Civil and Environmental Engineering, University of Michigan, 1351 Beal Ave, Ann Arbor, MI 48109-2125, Tel.  734-763-8032; Fax 734-763-2275; Email adriaens@umich.edu
Meng-Ying Li, Civil and Environmental Engineering, University of Michigan, 1351 Beal Ave, Ann Arbor, MI 48109-2125, Tel.  734-763-1464; Fax 734-763-2275; Email mengyl@umich.edu

Sediment site managers are often confronted with decisions on sampling density to properly capture spatial variability for site characterization, and with decisions regarding the scale of new technology demonstrations to enable efficacy assessment.  Reliable characterization of the spatial distribution of sediment site attributes, such as contaminant concentrations, the impact of microbial activity on contaminants, and microbial characteristics depends on how well sampled values represent all values throughout the entire site. Whereas geostatistical tools have been developed to interpolate the attribute values in space, these do not explicitly take into account the uncertainties associated with the various scales (field cores, columns, or microcosms) at which the data have been collected. A recently developed statistical model (M-Scale) takes into account multiple scales and multiple resolutions to optimize the reliability of sampled data. The model not only serves as a tool to evaluate parameter relationships over different scales by their covariances and data uncertainty, but also makes further use of these covariances and data uncertainty as basis for a precision-optimized estimator. These estimators can then be used to scale laboratory information to the field, and conversely, to use field-derived data for uncertainty-based decision-making for technology demonstrations. Information from each scale will be weighted by the projected similarity to the scales of interest, with adjustments considering the different precision they provide. Unlike conventional geostatistic tools that are based on the point-to-point spatial structures, the multi-scale model introduces a new framework for spatial analysis in which regional values at different scales are anchored by the correlations of each other.  Examples will be presented using dioxin distributions, the impact of microbial dechlorination activity on the patterns observed, and microbial abundance interpolations.

Issues of Biostimulation, Bioaugmentation and Bioavailability in the Remediation of PAHs in a Coal Tar Soil

Joseph J. Pignatello, Department of Soil and Water, Connecticut Agricultural Experiment Station, 123 Huntington St., New Haven, CT 06504-1106, Email: joseph.pignatello@po.state.ct.us

This presentation will include the results of a lab-scale study of enhanced bioremediation of polycyclic aromatic hydrocarbons (PAHs) in soil from a manufactured gas plant (MGP) site in Connecticut, as well as some results of peripheral studies on sorption reversibility in other soil-contaminant systems. Biodegradation and desorption experiments on the MGP soil were conducted in well-mixed aerobic suspensions containing various additives over a 93-106 day period.  Both biotransformation and desorption decreased with PAH ring size, becoming negligible for the six-ring PAHs.  Biodegradation by native organisms was strongly accelerated by addition of inorganic nutrients (N, P, K, and trace metals).  No further rate enhancement occurred by addition of a site-derived bacterial enrichment culture even though it boosted by ~100-fold the aromatic dioxygenase levels; nor by the addition of  chelating agents (citrate or pyrophosphate) even though they were previously found to enhance desorption in killed controls.  The strong ability of nutrients to stimulate degradation of the bioavailable PAHs by native cells indicates that their persistence for many decades at this site (and possibly others) is likely due to nutrient-limited natural biodegradation. It also suggests that an effective strategy for their bioremediation could consist simply of adding inorganic nutrients.

Rates of biotransformation of PAHs by biostimulated native organisms outpaced their maximal rates of desorption in sterilized flasks which contained desorption-enhancing chelating agents and an infinite sink polymer adsorbent, Tenax. This indicates that indigenous organisms facilitated desorption. This result contradicts other recent studies including our own which show correlations between physical and micro-biological availabilities of a given compound.

Despite the promising results obtained for this MGP soil, a minor fraction of each PAH, in intact form, remains recalcitrant to biodegradation. Recent work in our group on other soil-chemical systems has shown that organic compounds cause swelling and shrinking of natural organic matter during sorption and desorption. The act of desorption can lead to collapse of pore walls surrounding remaining sorbed molecules, leading to their physical immobilization.

Entombment of Pure-Phase Tar Impacted Sediment in New Bedford Harbor: A Case Study

Timothy Condon, P.E., LSP, Lightship Engineering, LLC, 36 Cordage Park Circle, Suite 312, Plymouth, Massachusetts, 02360, Tel: 508-830-3344, Fax: 508-830-3360, Email: tfcondon@LightshipEngineering.com
Michael J. Pierdinock, LSP, CHMM, Lightship Engineering, LLC, 36 Cordage Park Circle, Suite 312, Plymouth, Massachusetts, 02360, Tel: 508-830-3344, Fax: 508-830-3360, Email: mjpierdinock@LightshipEngineering.com

This case study involves the assessment and entombment of 10 feet of pure-phase tar currently impacting marine sediments associated with a Manufactured Gas Plant and Tar Processing Facility (“MGP”) in Massachusetts.  Lightship Engineering personnel was selected to assess the nature and extent of tar and MGP residuals, conduct hydrogeologic modeling, complete human health and Stage I and II environmental risk characterizations, develop strategies for achieving regulatory closure and, design and implement the selected remedial alternative. 

Alternatives to remediate the pure-phase tar in the boat slip included: capping; entombment; dredging; and solidification.  Detailed cost and engineering evaluations were conducted to assess the technologic and economic feasibility of each option.  Based upon the detailed evaluation, entombment using the Waterloo Barrier^® system was selected as the best remedial option.

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