Michael Healey (Ontario) and Duane Graves, Ph.D. (Tennessee) will present at World of Coal Ash 2022 at the Northern Kentucky Convention Center in Covington, Kentucky, May 16-19, 2022.

Michael is the Treatability and SP3™ Services Supervisor at SiREM with eight years of experience. Michael has managed numerous bench-scale studies evaluating remediation technologies for contaminants including chlorinated solvents, petroleum hydrocarbons, emerging contaminants and other recalcitrant compounds in soil, sediment, and groundwater. Michael has several years of passive sampling experience and was a lead member in the development and commercialization of the SP3™ sampler.

Duane Graves is a Senior Principal Scientist based in Tennessee with more than 30 years of experience focused on environmental biotechnology; environmental forensics; in situ groundwater, soil, and sediment remediation; evaluation of airborne biological contaminants; and remediation of groundwater in karst formations.

WOCA is an international conference organized by the American Coal Ash Association (ACAA) and the University of Kentucky Center for Applied Energy Research (CAER). The 2022 conference is the 9th joint biennial meeting with a focus on the science, applications, and sustainability of worldwide coal combustion products (CCPs) as well as gasification products.

The American Coal Ash Association was established in 1968 as a trade organization devoted to recycling the materials created when we burn coal to generate electricity. Their members comprise the world’s foremost experts on coal ash (fly ash and bottom ash), and boiler slag, flue gas desulfurization gypsum or “synthetic” gypsum, and other “FGD” materials captured by emissions controls. While other organizations focus on disposal issues, ACAA’s mission is to advance the management and use of coal combustion products in ways that are: environmentally responsible; technically sound; commercially competitive; and supportive of a sustainable global community.

SiREM Presentations

Title: Building Defensibility for MNA Remedy Selection
Session D14: Groundwater and Environment
Presenters: Michael Healey, Herwig Goldemund, Bob Glazier, Andrzej Przepiora (Geosyntec)
Date/Time: Thursday, May 19 at 10:30 – 11:00 a.m. EDT
Characteristics that make a site a potential candidate for a Monitored Natural Attenuation (MNA) groundwater remedy were presented at last year’s workshop. This year, laboratory treatability studies and field sample collections that are commonly used for proof-of-concept and/or derivation of site-specific design parameters will be presented. These methods have been used to develop groundwater remedial options for a wide variety of contaminants including those found at coal combustion residual (CCR) sites. An important consideration in groundwater remedy selection is the suitability of MNA as a remedy component or as a stand-alone passive remedy. Part of evaluating whether MNA is an appropriate remedial technology at a CCR site involves the demonstration of the type(s) and longevity of ongoing natural attenuation processes, including the capacity of an aquifer to attenuate site-specific constituents. This requires the characterization of groundwater and/or aquifer solids geochemistry as well as subsequent column and/or leachability testing. This presentation will focus on the use of (i) a suite of field sample collection tools and data analysis approaches and (ii) microcosm and column treatability testing to evaluate groundwater treatment options for CCR-associated metals such as arsenic (As), including enhanced and natural attenuation options.
In one demonstration, an electron donor (emulsified vegetable oil) was used together with other reagents to reduce As solubility and mobility by decreasing the oxidation-reduction (redox) potential and precipitating insoluble (or sparingly soluble) As sulfides. In another demonstration for a CCR site, a comprehensive laboratory program was developed and performed based upon the USEPA’s tiered approach to identify the natural attenuation processes, rates, attenuation capacities, and longevity. The program included a detailed evaluation of the aqueous geochemistry, aquifer matrix minerology and chemical composition, As speciation, adsorption and desorption reactions, and stability of the immobilized constituents. The laboratory results, along with a detailed conceptual site model, were used to develop a hydrogeochemical site model that described the fate of dissolved As downgradient of a CCR impoundment.

Application of Monitored Natural Attenuation for Both Mobile and Reactive Species – A Case Study
Monitored natural attenuation (MNA) is a groundwater remedial alternative (or remedy component) often considered for sites with source control measures, stable plumes, low to moderate constituent concentrations, and incomplete exposure pathways. MNA uses one or more natural processes to attenuate constituent concentrations to below cleanup goals. We will present a case study on an MNA demonstration to support a corrective measures analysis for boron, lithium, molybdenum, and sulfate in groundwater at a legacy site regulated under the new Illinois state CCR rules (IL 35 Ill. Admin. Code 845) where source control measures were not yet complete.

The MNA evaluation followed the tiered approach, which is recommended by USEPA and EPRI guidance, to progressively increase the understanding of site conditions and the potential applicability of MNA. Evaluations of attenuation mechansims, rate, capacity, and reversibility were completed to as part of the tiered demonstration. While the site plans to complete aggressive source control measures (closure-by-removal), these measures have not yet started. Thus, groundwater fate and transport modeling and a risk analysis were used to estimate future mass released and potential risks to receptors. Results of X-ray diffraction (XRD) and sequential extraction procedure (SEP) analyses completed on aquifer solids collected from the site were used to gain insight to the attenuation mechanisms and to design batch adsorption and desorption tests which characterized the natural attenuation capacity and (ir)reversibility. This case study provides a real-world example of preparation of a tiered MNA evaluation at site where source control is planned but not yet complete and where both conservative and reactive species are evaluated.

Application of Biogeochemistry and Environmental Microbiomics for Managing CCR and CCR-impacted Groundwater
Session D6: Groundwater and Environment
Speaker: Duane Graves
Date/Time: Wednesday, May 18 at 02:00 – 02:30 p.m. EDT
Environmental microbiomics is a rapidly evolving field that enables understanding of the interplay of microbial communities and their environment. This practice area is widely applicable, including the development of predictive models and optimizing beneficial activities in virtually any microbial system. Given the metabolic diversity of naturally occurring microbial communities, microbes may perform several beneficial reactions that may directly or indirectly influence constituents in groundwater near CCR impoundments and landfills. For example, natural attenuation involving inorganic biogeochemistry relies on the stabilization of elements by forming insoluble sulfides, hydroxides, carbonates or phosphates as a result of bacterial redox reactions. These transformative reactions have the potential to favorably influence the cost and complexity of long-term CCR management.   Information about microbial communities is instrumental in understanding biogeochemical reactions available for in place CCR management and protection of natural resources. However, a critical data gap exists in our understanding of the microbial populations present in CCR. Advances in environmental microbiomics and biogeochemistry as it relates to CCR includes the following case studies: (1) characterization of bacterial population diversity and potential metabolic function in CCR; (2) investigation of arsenic fluxes in groundwater affected by biogeochemistry; and (3) the use of biogeochemical datato support alternate source demonstrations. Results from these investigations provide unprecedented resolution of microbes present in CCR wastes anddemonstratehow those microbial communities may influence the geochemical state (solubility and mineral phases) or inorganics and metals. This information defines the types of biogeochemical reactions that can be applied to fine tunea remedial approach whether it is engineered or natural. Based on the successfulapplication of microbial reactionsto support cleanupsin other industries and current knowledge of CCR microbial communities, this technically advanced strategy offers sustainable, durable, and cost-effective options for managing CCR, associated leachate, and groundwater/surface water impacts.

Methods for Biogeochemical and Microbial Community Analysis Yield Insightful Data for CCR Management
Session K3: Emerging Technologies
Speaker: Duane Graves
Date/Time: Wednesday, May 18 at 03:30 – 4:00 p.m. EDT
The growing awareness of the role of microorganisms in altering the chemical state of CCR-related mineral elements and compounds requiresdifferent analytical methodsto discern biogeochemical reactions than those typically used to characterize CCR impoundments and associated groundwater.   Specifically, the biological reactions that can alterthe solubility of arsenic, selenium, cationic metals, and anions has been largely under-valued in the evaluation of CCR impoundment closure and remediation alternatives evaluations.   Analytical methods are now available for high resolution characterization of microbial communities and the ways they may interact with CCR and CCR impacted media. Molecular and genomic analytical methodsprovide insights into the mechanisms forbiogeochemical stabilization of metals, monitored natural attenuation (MNA) and beneficial or deleteriousshifts in microbial populations directly related to biogeochemical reactivity and enhanced bioremediation. The role of microorganisms is evaluated by  complementing  chemical  and  geochemical  characterization  results  with  an  assessment  of  the biochemical reactivity supported by different members of the microbial community. This is accomplished using techniques forthe isolation and investigation of the genetic material (i.e., DNA) from in situ microbial communities. The specific molecular or genomic strategy is dictated by the project objectives and can include approaches such as polymerase chain reaction (PCR)-based screening, microarrays, next generation sequencing of16S rRNA gene, and shotgun metagenomic sequencing. Each of these approaches provides differing levels of understanding of the potential metabolic capability of keystone species and/or microbial communities and theirfunctional genes. The selection of the best method for a site is decided based on the information required to address data gaps in the conceptual site model and the types of information that are most likely to support the design of the management strategy for the CCRimpoundment. Nextgeneration sequencing is currentlythe preferred method for identifying the bacteria present in CCR, leachate, andCCR-impacted environments (i.e., groundwater and soils). Bacterial community data obtained from NGS can be used identify likely reactions that can occur naturally or be engineered to occur in CCP and further correlated with geochemical and metal data to support remedial decisions.This presentation will describethe methods and interpretationof genomic analytical data, how the results are intertwined with more traditional chemical and geochemical data, and the potential benefits gained from a conceptual site model that more fully integrates site characteristics with the microbiology that directly and indirectly influences subsurface conditions.

More Information

About the event: World of Coal Ash 2022
About American Coal Ash Association: American Coal Ash Association – Home (acaa-usa.org)
For consultation regarding Groundwater Remedies, contact Michael at mhealey@siremlab.com
Learn more about Michael: Michael Healey | LinkedIn