Education

Research Description

Dr. Call's research focuses on water and wastewater treatment technologies. He has expertise in both biological and electrochemical principles. Examples of current research interests include: 1) removal of emerging drinking water contaminants, including per- and polyfluoroalkyl substances (PFAS), using electrically-driven separation processes, 2) investigating microbial interactions with pyrogenic carbonaceous materials (e.g., activated carbon, biochar) to enable aqueous contaminant transformations (i.e., biological activated carbon) and energy recovery from wastewater (i.e., anaerobic digestion), 3) desalination of brackish water using capacitive deionization (CDI), 4) phosphate recovery from wastewater using nano-based sorbents, and 5) conversion of nitrogen gas into ammonium using microbial electrochemical technologies.

Honors and Awards

• Outstanding Young Alumni Award - Virginia Tech, 2019

Publications

Amending anaerobic bioreactors with pyrogenic carbonaceous materials: the influence of material properties on methane generation

Cheng, Q., Reyes, F. L., III, & Call, D. F. (2018), ENVIRONMENTAL SCIENCE-WATER RESEARCH & TECHNOLOGY, 4(11), 1794–1806. https://doi.org/10.1039/c8ew00447a

Impact of solution composition on the resistance of ion exchange membranes

Zhu, S., Kingsbury, R. S., Call, D. F., & Coronell, O. (2018), Journal of Membrane Science, 554, 39–47. https://doi.org/10.1016/j.memsci.2018.02.050

Junction potentials bias measurements of ion exchange membrane permselectivity

Kingsbury, R. S., Flotron, S., Zhu, S., Call, D. F., & Coronell, O. (2018), Environmental Science & Technology, 52(8), 4929–4936. https://doi.org/10.1021/acs.est.7b05317

Impact of natural organic matter and inorganic solutes on energy recovery from five real salinity gradients using reverse electrodialysis

Kingsbury, R. S., Liu, F., Zhu, S., Boggs, C., Armstrong, M. D., Call, D. F., & Coronell, O. (2017), Journal of Membrane Science, 541, 621–632. https://doi.org/10.1016/j.memsci.2017.07.038

Hardwiring microbes via direct interspecies electron transfer: Mechanisms and applications

Cheng, Q. W., & Call, D. F. (2016), Environmental Science-Processes & Impacts. https://doi.org/10.1039/c6em00219f

Substrate and electrode potential affect electrotrophic activity of inverted bioanodes

Hartline, R. M., & Call, D. F. (2016), Bioelectrochemistry, 110, 13–18. https://doi.org/10.1016/j.bioelechem.2016.02.010

Geobacter sp SD-1 with enhanced electrochemical activity in high-salt concentration solutions

Sun, D., Call, D., Wang, A. J., Cheng, S. A., & Logan, B. E. (2014), Environmental Microbiology Reports, 6(6), 723–729. https://doi.org/10.1111/1758-2229.12193

Microbial power-generating capabilities on micro-/nano-structured anodes in micro-sizedmicrobial fuel cells

Fraiwan, A., Adusumilli, S. P., Han, D., Steckl, A. J., Call, D. F., Westgate, C. R., & Choi, S. (2014), Fuel Cells, 14(6), 801–809. https://doi.org/10.1002/fuce.201400041

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Grants

Recovering High-value Acids from Anaerobic Co-digestion of Municipal Solid and Grease Interceptor Waste Using an Electrically Driven Separation Process

Environmental Research & Education Foundation(5/01/19 - 4/30/21)

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Recovering High-value Acids from Anaerobic Co-digestion of Municipal Solid and Grease Interceptor Waste Using an Electrically Driven Separation Process

Sponsor: Environmental Research & Education Foundation

Start Date: 5/01/19

End Date: 4/30/21

Abstract

Re-engineering the anaerobic co-digestion (AD) of municipal solids waste (MSW) to yield high-value chemical products could dramatically change the economics of this solid waste management strategy. Shutting down the biological pathways to CH4 production in AD (via inhibition of methanogenesis) can result in the production of volatile fatty acids (VFAs) without compromising solids destruction goals. VFAs are highly valued because they can serve as precursors to a wide-spectrum of chemicals, including fuels, paints, adhesives, cosmetics, and food additives. While the knowledge of how to operate AD to generate these VFAs exists, the primary challenge facing implementation of this approach is the lack of effective methods to separate and recover VFAs from AD. The objective of the proposed research is to investigate the potential of an electrically-driven, membrane-based technology to separate and recover VFAs during AD of MSW. The results will provide fundamental insight into VFA transport through membranes and apply the knowledge to the recovery of VFAs from representative MSW mixtures.

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EAGER Electrically Driving the Microbial Conversion of Nitrogen Gas into Ammonia

National Science Foundation (NSF)(8/15/18 - 7/31/20)

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EAGER Electrically Driving the Microbial Conversion of Nitrogen Gas into Ammonia

Sponsor: National Science Foundation (NSF)

Start Date: 8/15/18

End Date: 7/31/20

Abstract

Nitrogenous fertilizers are critical for sustaining small to large farms in the US. The Haber-Bosch process generates the majority of fixed nitrogen, but it comes at a high cost, both in terms of dollars and environmental impact. Requiring temperatures between 400-500oC and pressures of 150-250 bar, this process consumes 1-2% of global energy. Reliance on fossil fuels to power this process translates into unstable fertilizer prices and a significant release of greenhouse gases. Low-cost and carbon-neutral ammonia fertilizer production is therefore needed to improve the sustainability of our food production systems. Biological nitrogen (N2) fixation, as practiced in the farming of legumes, is attractive because of its low-energy demand, operation under ambient conditions, and point-of-use production; however, slow fixation rates and, in the case of non-legume crops, a lack of abundant N2 fixing symbiotic diazotrophs in the soil, limit the large-scale feasibility of this approach. Moreover, options to accelerate symbiotic N2 fixation rates to the industrial levels needed to compete with the Haber-Bosch process are lacking. As an alternative, we propose investigating a hybrid microbial electrochemical system to electrically enhance microbial N2 fixation rates. Bacteria in these systems consume organic matter (such as waste biomass) and generate electrical current when they respire (breathe) on anode electrodes. By exploiting their physiology, we hypothesize that we can electrically “boost” N2 fixation rates in these organisms. The overall objective of this proposal is to determine the influence of the electrical driving force on the rates, mechanisms, and pathways of microbial N2 fixation. The rationale is that with this knowledge, we can improve N2 fixation rates in these communities and optimize a scalable technological platform to produce fixed nitrogen from small-scale farms to industrial-scale applications.

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Electrically Assisted Sorption and Desorption of Per- and Polyfluoroalkyl Substances

Strategic Environmental Research and Development Program (SERDP)(5/16/18 - 5/16/20)

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Electrically Assisted Sorption and Desorption of Per- and Polyfluoroalkyl Substances

Sponsor: Strategic Environmental Research and Development Program (SERDP)

Start Date: 5/16/18

End Date: 5/16/20

Abstract

The removal of per- and polyfluoroalkly substances (PFASs) from contaminated groundwater is required to minimize human exposure to these compounds. Activated carbon is a widely used sorbent to remove PFASs, but it suffers from two limitations: 1) the inability to remove short-chain PFASs, and 2) the lack of cost-effective regeneration methods. The overall objective of this proposal is to electrically enhance adsorption of high priority PFASs onto activated carbon and electrically discharge them as an innovative, chemical-free regeneration technique.

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Methane Conversion to Electrical Current using Microbial Electrochemical Technologies

NCSU Research and Innovation Seed Funding Program(1/01/15 - 12/31/15)

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Methane Conversion to Electrical Current using Microbial Electrochemical Technologies

Sponsor: NCSU Research and Innovation Seed Funding Program

Start Date: 1/01/15

End Date: 12/31/15

Abstract

The unprecedented supplies of natural gas in the US could have a significant impact on our growing demand for transportation fuels. The lack of an appropriate natural gas distribution infrastructure coupled with complex and costly conventional methods to generate drop-in fuels from natural gas are major barriers to realizing this impact. In this collaborative proposal between CoE and CALS, we will investigate the ability of naturally occurring microorganisms to convert methane gas (the major component of natural gas) into electrical current using a cutting-edge, recently commercialized microbial electrochemical technology. This electrical current can subsequently be used to generate liquid fuels or their precursors in these devices. This approach is potentially transformative because it circumvents the complexity associated with recent efforts to accumulate and extract fuel precursors from within methane-oxidizing microorganisms. Seed funding from RISF will allow us to obtain essential preliminary data to secure multi-year external funding from sources with interests in Energy and the Environment, such as the DOE and NSF.

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Improving the Anaerobic Treatment of Biosolids and High-Strength Waste Streams through Addition of Electrically-Conductive Particles

NCSU Water Resources Research Institute(3/01/15 - 12/31/16)

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Improving the Anaerobic Treatment of Biosolids and High-Strength Waste Streams through Addition of Electrically-Conductive Particles

Sponsor: NCSU Water Resources Research Institute

Start Date: 3/01/15

End Date: 12/31/16

Abstract

North Carolina has a tremendous need for efficiently treating high-strength waste streams. These include agricultural residuals, food wastes, and wastewater-derived biosolids. Anaerobic digestion is one promising treatment and energy recovery method, but several limitations prevent widespread adoption. One of which is the instability that can arise from disruptions between key groups of microorganisms and another is the incomplete conversion of organics to methane gas (CH4). To overcome these limitations, we propose augmenting anaerobic digesters with electrically conductive micro-scale particles. These particles have proven effective as conduits for microbe-to-microbe direct electron transfer, resulting in improved rates of CH4 generation using pure strains in the lab. We hypothesize that supplementing anaerobic digesters with these particles will improve stability and CH4 recovery by strengthening interspecies electron transfer between the two central microbial communities: syntrophic bacteria and the methane-generating methanogens. Our objectives are to (1) determine the impact of various particle properties (type, conductivity, size) on organics removal and CH4 generation, (2) determine optimal particle loading densities for two distinct waste streams, and (3) assess the settleability of particle-augmented waste. To do this, we will operate lab-scale anaerobic digesters with and without conductive particles (activated carbon, magnetite, biochar). These findings will be especially beneficial for wastewater treatment facilities and farmers around the state looking for strategies to tip the economics in favor of anaerobic digestion technology while ensuring the health of our water resources.

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