@article{ortiz-medina_poole_grunden_call_2023, title={Nitrogen Fixation and Ammonium Assimilation Pathway Expression of Geobacter sulfurreducens Changes in Response to the Anode Potential in Microbial Electrochemical Cells}, volume={3}, ISSN={["1098-5336"]}, DOI={10.1128/aem.02073-22}, abstractNote={Biological nitrogen fixation coupled with ammonium recovery provides a sustainable alternative to the carbon-, water-, and energy-intensive Haber-Bosch process. Aerobic biological nitrogen fixation technologies are hindered by oxygen gas inhibition of the nitrogenase enzyme.}, journal={APPLIED AND ENVIRONMENTAL MICROBIOLOGY}, author={Ortiz-Medina, Juan F. and Poole, Mark R. and Grunden, Amy M. and Call, Douglas F.}, year={2023}, month={Mar} }
 @article{mclamore_duckworth_boyer_marshall_call_bhadha_guzman_2023, title={Perspective: Phosphorus monitoring must be rooted in sustainability frameworks spanning material scale to human scale}, volume={19}, ISSN={["2589-9147"]}, DOI={10.1016/j.wroa.2023.100168}, abstractNote={Phosphorus (P) is a finite resource, and its environmental fate and transport is complex. With fertilizer prices expected to remain high for years and disruption to supply chains, there is a pressing need to recover and reuse P (primarily as fertilizer). Whether recovery is to occur from urban systems (e.g., human urine), agricultural soil (e.g., legacy P), or from contaminated surface waters, quantification of P in various forms is vital. Monitoring systems with embedded near real time decision support, so called cyber physical systems, are likely to play a major role in the management of P throughout agro-ecosystems. Data on P flow(s) connects the environmental, economic, and social pillars of the triple bottom line (TBL) sustainabilty framework. Emerging monitoring systems must account for complex interactions in the sample, and interface with a dynamic decision support system that considers adaptive dynamics to societal needs. It is known from decades of study that P is ubiquitous, yet without quantitative tools for studying the dynamic nature of P in the environment, the details may remain elusive. If new monitoring systems (including CPS and mobile sensors) are informed by sustainability frameworks, data-informed decision making may foster resource recovery and environmental stewardship from technology users to policymakers.}, journal={WATER RESEARCH X}, author={McLamore, Eric and Duckworth, Owen and Boyer, Treavor H. and Marshall, Anna-Maria and Call, Douglas F. and Bhadha, Jehangir H. and Guzman, Sandra}, year={2023}, month={May} }
 @article{mallick_hossain_takshi_call_mayer_2023, title={The challenge of non-reactive phosphorus: Mechanisms of treatment and improved recoverability using electrooxidation}, volume={11}, ISSN={["2213-3437"]}, DOI={10.1016/j.jece.2023.110295}, abstractNote={Recalcitrant phosphorus (P) species, i.e., soluble non-reactive phosphorus (sNRP), are generally not effectively removed or recovered in conventional wastewater treatment processes. This was substantiated in our meta-analysis, which showed that nearly one-third of wastewater facilities’ effluent P was primarily in the non-reactive form. Transformation of sNRP to more readily removable/recoverable soluble reactive phosphorus (sRP) may offer a viable pathway to enhance P removal and recovery. Electrooxidation (EO) may offer one route for sNRP to sRP transformation. During EO, different sNRP transformation pathways may occur, influencing the extent and efficiency of sNRP transformations as a function of water quality. To explore these mechanisms, we conducted oxidant quenching tests as well as cyclic voltammetry and chronoamperometry experiments using a synthetic water matrix spiked with the sNRP compound beta-glycerol phosphate (BGP). We found that direct electron transfer was responsible for BGP transformation. To assess the applicability of EO for wastewater sNRP to sRP transformation and improved recoverability, EO was used to treat municipal wastewater centrate, followed by tests of sNRP recoverability using the P-selective LayneRT™ ion exchanger. Complete transformation of centrate sNRP to sRP was not achieved with EO, but subsequent removal of sNRP using ion exchange increased after 2 hr of EO treatment. Longer periods of EO treatment did not improve sNRP removal. Improved sNRP adsorption after EO was likely due to decreased competing organics in the centrate after EO treatment. Overall, this study showed that EO can improve sNRP removal using subsequent ion exchange and facilitate enhanced P recovery.}, number={5}, journal={JOURNAL OF ENVIRONMENTAL CHEMICAL ENGINEERING}, author={Mallick, Synthia Parveen and Hossain, Mohammad Shakhawat and Takshi, Arash and Call, Douglas F. and Mayer, Brooke K.}, year={2023}, month={Oct} }
 @article{algurainy_call_2022, title={Improving Long-Term Anode Stability in Capacitive Deionization Using Asymmetric Electrode Mass Ratios}, volume={2}, ISSN={["2690-0645"]}, DOI={10.1021/acsestengg.1c00348}, abstractNote={Activated carbon (AC) electrodes are used for desalination in capacitive deionization (CDI) because they provide a large, porous surface area at a low cost. In short-term tests, AC electrodes can achieve relatively high salt adsorption capacities. In long-term tests, desalination performance degrades significantly. The poor performance has been attributed to the corrosion of carbon in the anode electrode. Here, we show a simple strategy to improve anode stability by changing the mass ratio of AC electrodes (asymmetric configuration) in flow-through CDI (FT-CDI). Increasing the anode mass by double and triple decreased the anode half-cell potential by up to 21 and 64%, respectively, relative to cells with single anodes. Less positive anode potentials were associated with smaller shifts in the anode potential of zero charge and lower acidity in the effluent. Additional evidence for improved anode stability in the asymmetric configurations was the significantly lower charge transfer resistance and oxygen to carbon ratio content of the anodes at the end of the tests. After 48 h of operation, the salt adsorption capacity decreased by 68% in symmetric cells, but, in asymmetric cells, it was more stable and decreased by only 47% (double anode) and 17% (triple anode). These trends were consistent when the anode was located upstream or downstream of the cathode. We attribute the improved anode stability to reduced oxidation in the asymmetric cells, which was driven by lower oxidative half-cell potentials. This, in turn, maintained a stable desalination performance over long-term operation. Our results demonstrate that increasing the anode mass is an effective strategy to extend anode stability and improve long-term salt removal in FT-CDI.}, number={1}, journal={ACS ES&T ENGINEERING}, author={Algurainy, Yazeed and Call, Douglas F.}, year={2022}, month={Jan}, pages={129–139} }
 @article{ding_barlaz_de los reyes iii_call_2022, title={Influence of Inoculum Type on Volatile Fatty Acid and Methane Production in Short-Term Anaerobic Food Waste Digestion Tests}, volume={12}, ISSN={["2168-0485"]}, url={https://doi.org/10.1021/acssuschemeng.2c04080}, DOI={10.1021/acssuschemeng.2c04080}, abstractNote={The anaerobic digestion of food waste can yield valuable volatile fatty acids (VFAs), especially when methane (CH4) production is inhibited. Selecting an inoculum with lower methanogenic populations may help reduce CH4 production and improve VFA accumulation. In this study, we investigated VFA and CH4 production in short-term anaerobic batch bioreactors as a function of three inocula compositions derived from a full-scale wastewater treatment facility: (1) anaerobic sludge (AnS), (2) thickened waste activated sludge (TWAS), and (3) TWAS with AnS. The highest VFA concentration (6.62 ± 0.08 g/L) and the lowest total CH4 volume (296 mL) were measured with TWAS only. In contrast, the highest CH4 volume (625 ± 3 mL) was measured in the TWAS + AnS, likely because the AnS was well adapted to digesting TWAS. 16S rDNA sequencing showed that TWAS alone had the lowest relative abundance of methanogens at the start and end of the incubations. The addition of TWAS significantly changed the initial community diversity. These insights suggest that TWAS improves VFA accumulation by providing a microbial community that is more diverse and lower in methanogen abundance relative to AnS. These findings will help guide the selection of inoculation strategies that promote VFA accumulation in anaerobic digesters.}, journal={ACS SUSTAINABLE CHEMISTRY & ENGINEERING}, author={Ding, Hezhou and Barlaz, Morton A. and de los Reyes III, Francis L. and Call, Douglas F.}, year={2022}, month={Dec} }
 @article{zhi_paterson_call_jones_hesterberg_duckworth_poitras_knappe_2022, title={Mechanisms of orthophosphate removal from water by lanthanum carbonate and other lanthanum-containing materials}, volume={820}, ISSN={["1879-1026"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-85123356200&partnerID=MN8TOARS}, DOI={10.1016/j.scitotenv.2022.153153}, abstractNote={Removing phosphorus (P) from water and wastewater is essential for preventing eutrophication and protecting environmental quality. Lanthanum [La(III)]-containing materials can effectively and selectively remove orthophosphate (PO4) from aqueous systems, but there remains a need to better understand the underlying mechanism of PO4 removal. Our objectives were to 1) identify the mechanism of PO4 removal by La-containing materials and 2) evaluate the ability of a new material, La2(CO3)3(s), to remove PO4 from different aqueous matrices, including municipal wastewater. We determined the dominant mechanism of PO4 removal by comparing geochemical simulations with equilibrium data from batch experiments and analyzing reaction products by X-ray diffraction and scanning transmission electron microscopy with energy dispersive spectroscopy. Geochemical simulations of aqueous systems containing PO4 and La-containing materials predicted that PO4 removal occurs via precipitation of poorly soluble LaPO4(s). Results from batch experiments agreed with those obtained from geochemical simulations, and mineralogical characterization of the reaction products were consistent with PO4 removal occurring primarily by precipitation of LaPO4(s). Between pH 1.5 and 12.9, La2(CO3)3(s) selectively removed PO4 over other anions from different aqueous matrices, including treated wastewater. However, the rate of PO4 removal decreased with increasing solution pH. In comparison to other solids, such as La(OH)3(s), La2(CO3)3(s) exhibits a relatively low solubility, particularly under slightly acidic conditions. Consequently, release of La3+ into the environment can be minimized when La2(CO3)3(s) is deployed for PO4 sequestration.}, journal={SCIENCE OF THE TOTAL ENVIRONMENT}, author={Zhi, Yue and Paterson, Alisa R. and Call, Douglas F. and Jones, Jacob L. and Hesterberg, Dean and Duckworth, Owen W. and Poitras, Eric P. and Knappe, Detlef R. U.}, year={2022}, month={May} }
 @article{cheng_call_2021, title={Developing microbial communities containing a high abundance of exoelectrogenic microorganisms using activated carbon granules}, volume={768}, ISSN={["1879-1026"]}, DOI={10.1016/j.scitotenv.2020.144361}, abstractNote={Microorganisms that can transfer electrons outside their cells are useful in a range of wastewater treatment and remediation technologies. Conventional methods of enriching exoelectrogens are cost-prohibitive (e.g., controlled-potential electrodes) or lack specificity (e.g., soluble electron acceptors). In this study a low-cost and simple approach to enrich exoelectrogens from a mixed microbial inoculum was investigated. After the method was validated using the exoelectrogen Geobacter sulfurreducens, microorganisms from a pilot-scale biological activated carbon (BAC) filter were subjected to incubations in which acetate was provided as the electron donor and granular activated carbon (GAC) as the electron acceptor. The BAC-derived community oxidized acetate and reduced GAC at a capacity of 1.0 mmol e− (g GAC)−1. After three transfers to new bottles, acetate oxidation rates increased 4.3-fold, and microbial morphologies and GAC surface coverage became homogenous. Although present at <0.01% in the inoculum, Geobacter species were significantly enriched in the incubations (up to 96% abundance), suggesting they were responsible for reducing the GAC. The ability to quickly and effectively develop an exoelectrogenic microbial community using GAC may help initiate and/or maintain environmental systems that benefit from the unique metabolic capabilities of these microorganisms.}, journal={SCIENCE OF THE TOTAL ENVIRONMENT}, author={Cheng, Qiwen and Call, Douglas F.}, year={2021}, month={May} }
 @article{de la cruz_cheng_call_barlaz_2021, title={Evidence of thermophilic waste decomposition at a landfill exhibiting elevated temperature regions}, volume={124}, ISSN={0956-053X}, url={http://dx.doi.org/10.1016/j.wasman.2021.01.014}, DOI={10.1016/j.wasman.2021.01.014}, abstractNote={There have been several reports of landfills exhibiting temperatures as high as 80 to 100 °C. This observation has motivated researchers to understand the causes of the elevated temperatures and to develop predictive models of landfill temperature. The objective of this research was to characterize the methanogenic activity of microbial communities that were derived from landfill samples excavated from a section of a landfill exhibiting gas well temperatures above 55 °C. Specific objectives were to: (1) determine the upper temperature limit for methane production; (2) evaluate the kinetics of methane generation when landfill-derived microcosms are incubated above and below their excavation temperature and derive a temperature inhibition function; and (3) evaluate microbial community shifts in response to temperature perturbations. Landfill microcosms were derived from 57 excavated landfill samples and incubated within ±2.5 °C of their excavation temperature between 42.5 °C and 87.5 °C. Results showed an optimum temperature for methane generation of ~57 °C and a 95% reduction in methane yield at ~72 °C. When select cultures were perturbed between 5 °C below and 15 °C above their in-situ temperature, both the rate and maximum methane production decreased as incubation temperature increased. Microbial community characterization using 16S rRNA amplicon sequencing suggests that thermophilic methanogenic activity can be attributed to methanogens of the genus Methanothermobacter. This study demonstrated that from a microbiological standpoint, landfills may maintain active methanogenic processes while experiencing temperatures in the thermophilic regime (<72 °C).}, journal={Waste Management}, publisher={Elsevier BV}, author={De la Cruz, Florentino B. and Cheng, Qiwen and Call, Douglas F. and Barlaz, Morton A.}, year={2021}, month={Apr}, pages={26–35} }
 @article{zhi_call_grieger_duckworth_jones_knappe_2021, title={Influence of natural organic matter and pH on phosphate removal by and filterable lanthanum release from lanthanum-modified bentonite}, volume={202}, ISSN={0043-1354}, url={http://dx.doi.org/10.1016/j.watres.2021.117399}, DOI={10.1016/j.watres.2021.117399}, abstractNote={Lanthanum modified bentonite (LMB) has been applied to eutrophic lakes to reduce phosphorus (P) concentrations in the water column and mitigate P release from sediments. Previous experiments suggest that natural organic matter (NOM) can interfere with phosphate (PO4)-binding to LMB and exacerbate lanthanum (La)-release from bentonite. This evidence served as motivation for this study to systematically determine the effects of NOM, solution pH, and bentonite as a La carrier on P removal. We conducted both geochemical modeling and controlled-laboratory batch kinetic experiments to understand the pH-dependent impacts of humic and fulvic acids on PO4-binding to LMB and La release from LMB. The role of bentonite was studied by comparing PO4 removal obtained by LMB and La3+ (added as LaCl3 salt to represent the La-containing component of LMB). Our results from both geochemical modeling and batch experiments indicate that the PO4-binding ability of LMB is decreased in the presence of NOM, and the decrease is more pronounced at pH 8.5 than at 6. At the highest evaluated NOM concentration (28 mg C L−1), PO4-removal by La3+ was substantially lower than that by LMB, implying that bentonite clay in LMB shielded La from interactions with NOM, while still allowing PO4 capture by La. Finally, the presence of NOM promoted La-release from LMB, and the amount of La released depended on solution pH and both the type (i.e., fulvic/humic acid ratio) and concentration of NOM. Overall, these results provide an important basis for management of P in lakes and eutrophication control that relies on LMB applications.}, journal={Water Research}, publisher={Elsevier BV}, author={Zhi, Yue and Call, Douglas F. and Grieger, Khara D. and Duckworth, Owen W. and Jones, Jacob L. and Knappe, Detlef R.U.}, year={2021}, month={Sep}, pages={117399} }
 @article{mueller_thomas_johnson_decarolis_call_2021, title={Life cycle assessment of salinity gradient energy recovery using reverse electrodialysis}, volume={25}, ISSN={["1530-9290"]}, DOI={10.1111/jiec.13082}, abstractNote={Abstract}, number={5}, journal={JOURNAL OF INDUSTRIAL ECOLOGY}, author={Mueller, Katelyn E. and Thomas, Jeffrey T. and Johnson, Jeremiah X. and DeCarolis, Joseph F. and Call, Douglas F.}, year={2021}, month={Oct}, pages={1194–1206} }
 @article{algurainy_call_2020, title={Asymmetrical removal of sodium and chloride in flow-through capacitive deionization}, volume={183}, ISSN={["1879-2448"]}, DOI={10.1016/j.watres.2020.116044}, abstractNote={Capacitive deionization (CDI) is an electrochemical method of removing salt ions from brackish water. A common assumption in CDI is that monovalent ions (e.g., Na+, Cl−) are removed in a 1:1 symmetry on the electrodes. Validation of this assumption with techniques such as ion chromatography is not commonly performed, but is important to better understand how parasitic process, such as faradaic reactions, affect ion removals. In this study, we quantified the removals of Na+ and Cl− as a function of electrode orientation in flow-through CDI. When the cathode was positioned upstream, Na+ and Cl− removals approached a 1:1 symmetry, but when the anode was located upstream, we observed a significant drop in Na+, but not Cl−, removals. We attributed this drop to oxygen reduction reactions at the cathode that competed with Na+ adsorption. Oxidation of carbon in the upstream anode yielded H+ that enhanced the reduction of oxygen to H2O2 at the downstream cathode, which in turn diverted electrons from Na+ adsorption. In the absence of oxygen, Na+ removals increased in the upstream anode orientation and were comparable to Cl− removals, confirming that competition with oxygen reduction reactions was the primary reason for decreased Na+ removal. In the upstream cathode orientation, we show that H2O2 generated at the cathode can be oxidized at the downstream anode, possibly enhancing Na+ removals via internal electron recycling. Salt adsorption capacities calculated using actual ion removals did not always agree with those estimated using changes in solution conductivity, with the largest disagreement observed when conductivity data were corrected for pH changes. Our results highlight that faradaic reactions, particularly oxygen reduction reactions, can contribute to asymmetrical removals of monovalent ions in flow-through CDI.}, journal={WATER RESEARCH}, author={Algurainy, Yazeed and Call, Douglas F.}, year={2020}, month={Sep} }
 @article{liu_coronell_call_2020, title={Effect of cross-chamber flow electrode recirculation on pH and faradaic reactions in capacitive deionization}, volume={492}, ISSN={["1873-4464"]}, DOI={10.1016/j.desal.2020.114600}, abstractNote={Mitigating faradaic reactions is critical for improving charge efficiency, reducing energy consumption, and protecting electrodes from degradation during desalination in capacitive deionization (CDI). In this study, we examined the influence of recirculating flow electrodes (FEs) within their respective anode and cathode chambers [within-chamber (WC)] or across them [cross-chamber (CC)] on pH, faradaic reactions, and energy demand under constant current operation. By changing from WC to CC (without FEs), the difference in pH between the anode and cathode chambers decreased from 10 to 4.5 units. Adding FEs to CC recirculation further reduced the pH gradient between anode and cathode chambers and resulted in the most stable pH (10.4 ± 0.08) of all treatments. We attributed the improvements in CC recirculation to faradaic consumption of anode-generated H+ at the cathode and neutralization of H+ and OH− via water formation. The capacitive behavior of FEs reduced several faradaic reactions by decreasing the whole-cell voltage. The energy consumption by the electrodes was reduced by 25% for the anode and 35% for the cathode when FEs were operated in CC instead of WC recirculation. These findings indicate that continuously recirculating FEs across the anode and cathode chambers can minimize detrimental faradaic reactions and pH changes in FE-CDI.}, journal={DESALINATION}, author={Liu, Fei and Coronell, Orlando and Call, Douglas F.}, year={2020}, month={Oct} }
 @misc{zhi_zhang_hjorth_baun_duckworth_call_knappe_jones_grieger_2020, title={Emerging lanthanum (III)-containing materials for phosphate removal from water: A review towards future developments}, volume={145}, ISSN={["1873-6750"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-85090951095&partnerID=MN8TOARS}, DOI={10.1016/j.envint.2020.106115}, abstractNote={The last two decades have seen a rise in the development of lanthanum (III)-containing materials (LM) for controlling phosphate in the aquatic environment. >70 papers have been published on this topic in the peer-reviewed literature, but mechanisms of phosphate removal by LM as well as potential environmental impacts of LM remain unclear. In this review, we summarize peer-reviewed scientific articles on the development and use of 80 different types of LM in terms of prospective benefits, potential ecological impacts, and research needs. We find that the main benefits of LM for phosphate removal are their ability to strongly bind phosphate under diverse environmental conditions (e.g., over a wide pH range, in the presence of diverse aqueous constituents). The maximum phosphate uptake capacity of LM correlates primarily with the La content of LM, whereas reaction kinetics are influenced by LM formulation and ambient environmental conditions (e.g., pH, presence of co-existing ions, ligands, organic matter). Increased La solubilization can occur under some environmental conditions, including at moderately acidic pH values (i.e., < 4.5–5.6), highly saline conditions, and in the presence of organic matter. At the same time, dissolved La will likely undergo hydrolysis, bind to organic matter, and combine with phosphate to precipitate rhabdophane (LaPO4·H2O), all of which reduce the bioavailability of La in aquatic environments. Overall, LM use presents a low risk of adverse effects in water with pH > 7 and moderate-to-high bicarbonate alkalinity, although caution should be applied when considering LM use in aquatic systems with acidic pH values and low bicarbonate alkalinity. Moving forward, we recommend additional research dedicated to understanding La release from LM under diverse environmental conditions as well as long-term exposures on ecological organisms, particularly primary producers and benthic organisms. Further, site-specific monitoring could be useful for evaluating potential impacts of LM on both biotic and abiotic systems post-application.}, journal={ENVIRONMENT INTERNATIONAL}, author={Zhi, Yue and Zhang, Chuhui and Hjorth, Rune and Baun, Anders and Duckworth, Owen W. and Call, Douglas F. and Knappe, Detlef R. U. and Jones, Jacob L. and Grieger, Khara}, year={2020}, month={Dec} }
 @article{schupp_de la cruz_cheng_call_barlaz_2020, title={Evaluation of the Temperature Range for Biological Activity in Landfills Experiencing Elevated Temperatures}, volume={1}, ISSN={2690-0645}, url={http://dx.doi.org/10.1021/acsestengg.0c00064}, DOI={10.1021/acsestengg.0c00064}, abstractNote={There have been reports of municipal solid waste landfills with waste and gas wellhead temperatures of at least 80–100 °C, which is in excess of temperatures reported at typical landfills. Landfill...}, number={2}, journal={ACS ES&T Engineering}, publisher={American Chemical Society (ACS)}, author={Schupp, Sierra and De la Cruz, Florentino B. and Cheng, Qiwen and Call, Douglas F. and Barlaz, Morton A.}, year={2020}, month={Oct}, pages={216–227} }
 @article{hossen_gobetz_kingsbury_liu_palko_dubbs_coronell_call_2020, title={Temporal variation of power production via reverse electrodialysis using coastal North Carolina waters and its correlation to temperature and conductivity}, volume={491}, ISSN={["1873-4464"]}, DOI={10.1016/j.desal.2020.114562}, abstractNote={Global estimates of electricity generation from coastal salinity gradient energy resources rely on the underlying assumption that these gradients are spatially and temporally stable. Refining these estimates requires a better understanding of coastal variations in water properties and their impact on power production. This study investigated power output in reverse electrodialysis (RED) cells by coupling seawater samples collected from three different sites along coastal North Carolina at five different sampling dates between 2016 and 2017 with wastewater effluent from a wastewater treatment facility as the dilute solution. We found that power density did not vary substantially across the sampling dates except for one notable drop in power for a sample collected during an approaching hurricane. For all sites, power output peaked during the summer season. Using our experimental results, we developed a semi-empirical predictive model of RED power output as a function of temperature and conductivity. The model was able to predict power density within approximately 20% of the experimental power densities for the seawater samples used in this study and others in the literature. Combining our modeling approach with temporal conductivity and temperature data may help identify promising sites for coastal salinity gradient energy installations.}, journal={DESALINATION}, author={Hossen, Elvin H. and Gobetz, Zoe E. and Kingsbury, Ryan S. and Liu, Fei and Palko, Hannah C. and Dubbs, Lindsay L. and Coronell, Orlando and Call, Douglas F.}, year={2020}, month={Oct} }
 @article{ortiz-medina_call_2019, title={Electrochemical and Microbiological Characterization of Bioanode Communities Exhibiting Variable Levels of Startup Activity}, volume={7}, ISSN={["2296-598X"]}, DOI={10.3389/fenrg.2019.00103}, abstractNote={Microbial electrochemical technologies require the establishment of anode biofilms to generate electrical current. The factors driving bioanode formation and their variability during startup remain unclear, leading to a lack of effective strategies to initiate larger-scale systems. Accordingly, our objective was to characterize the electrochemical properties and microbial community structure of a large set of replicate bioanodes during their first cycle of current generation. To do this, we operated eight bioanode replicates at each of two fixed electrode potentials (−0.15 V and +0.15 V vs. standard hydrogen electrode) for one fed-batch cycle. We found that startup time decreased and maximum current generation increased at +0.15 V compared to −0.15 V, but at both potentials the bioanode replicates clustered into three distinct activity levels based on when they initiated current. Despite a large variation in current generation across the eight +0.15 V bioanodes, bioanode resistance and abundance of Geobacter species remained quite similar, differing by only 10% and 12%, respectively. At −0.15 V, current production strongly followed Geobacter species abundance and bioanode resistance, wherein the largest abundance of Geobacter was associated with the lowest charge transfer resistance. Our findings show that startup variability occurs at both applied potentials, but the underlying electrochemical and microbial factors driving variability are dependent on the applied potential.}, journal={FRONTIERS IN ENERGY RESEARCH}, author={Ortiz-Medina, Juan F. and Call, Douglas F.}, year={2019}, month={Sep} }
 @article{ortiz-medina_grunden_hyman_call_2019, title={Nitrogen Gas Fixation and Conversion to Ammonium Using Microbial Electrolysis Cells}, volume={7}, ISSN={2168-0485 2168-0485}, url={http://dx.doi.org/10.1021/acssuschemeng.8b05763}, DOI={10.1021/acssuschemeng.8b05763}, abstractNote={Ammonia (NH3) is an important industrial chemical that is produced using the energy- and carbon-intensive Haber-Bosch process. Recovering NH3 from microorganisms that fix nitrogen gas (N2) may provide a sustainable alternative because their specialized nitrogenase enzymes can reduce N2 to ammonium (NH4+) without the need for high temperature and pressure. This study explored the possibility of converting N2 into NH4+ using anaerobic, single-chamber microbial electrolysis cells (MECs). N2 fixation rates [based on an acetylene gas (C2H2) to ethylene gas (C2H4) conversion assay] of a microbial consortium increased significantly when the applied voltage between the anode and cathode increased from 0.7 to 1.0 V and reached a maximum of ∼40 nmol of C2H4 min–1 mg protein–1, which is comparable to model aerobic N2-fixing bacteria. The presence of NH4+, which can inhibit the activity of the nitrogenase enzyme, did not significantly reduce N2 fixation rates. Upon addition of methionine sulfoximine, an NH4+ uptake i...}, number={3}, journal={ACS Sustainable Chemistry & Engineering}, publisher={American Chemical Society (ACS)}, author={Ortiz-Medina, Juan F. and Grunden, Amy M. and Hyman, Michael R. and Call, Douglas F.}, year={2019}, month={Jan}, pages={3511–3519} }
 @article{cheng_de los reyes_call_2018, title={Amending anaerobic bioreactors with pyrogenic carbonaceous materials: the influence of material properties on methane generation}, volume={4}, ISSN={2053-1400 2053-1419}, url={http://dx.doi.org/10.1039/c8ew00447a}, DOI={10.1039/c8ew00447a}, abstractNote={The impact of pyrogenic carbonaceous material amendments on methane production in short-term anaerobic batch reactors depended on multiple material properties, including, but not limited to, electrical conductivity.}, number={11}, journal={Environmental Science: Water Research & Technology}, publisher={Royal Society of Chemistry (RSC)}, author={Cheng, Qiwen and de los Reyes, Francis L. and Call, Douglas F.}, year={2018}, pages={1794–1806} }
 @article{zhu_kingsbury_call_coronell_2018, title={Impact of solution composition on the resistance of ion exchange membranes}, volume={554}, ISSN={["1873-3123"]}, DOI={10.1016/j.memsci.2018.02.050}, abstractNote={Resistance to ion transport in ion exchange membranes (IEMs) is detrimental to the performance of IEM-based processes. In this work we measured the resistance of representative IEMs, i.e. one cation (CEM) and one anion (AEM) exchange membrane, in 15 single-salt solutions using electrochemical impedance spectroscopy. Resistance was sensitive to solute identity only in the case of the CEM for which it depended on the counter-ion identity; the resistance of the CEM was mostly insensitive to the co-ion identity, and the resistance of the AEM was mostly insensitive to both the counter-ion and co-ion identity. For all solutes, membrane resistance decreased sharply with increasing solution concentration below 0.1 M, and remained approximately constant above 0.1 M. An empirical mathematical model comprising a concentration-dependent term and a concentration-independent term successfully described membrane resistance as a function of solution concentration. The model builds on that previously proposed by Galama et al. (JMS 467 (2014), 279–291). We found that for both membranes, the concentration-dependent and concentration-independent terms of the resistance increased with increasing counter-ion hydration free energy. This was rationalized as the energy barrier to counter-ions having to shed/reorient water molecules of hydration, due to steric effects, when permeating the membranes. Also for both membranes, the concentration-dependent term of the resistance generally had a non-linear relationship with salt concentration. This result suggests that the concentration-dependent term is not attributable to bulk solution, and that there is a degree of randomness to the interconnectedness between the different membrane regions that contribute to ionic resistance. Our findings improve the understanding of the relationships between electrolyte properties and IEM resistance, and provide tools for assessing IEM resistance. This improved understanding is critical to establishing a complete IEM resistance theory and to evaluating new applications for IEMs.}, journal={JOURNAL OF MEMBRANE SCIENCE}, author={Zhu, Shan and Kingsbury, Ryan S. and Call, Douglas F. and Coronell, Orlando}, year={2018}, month={May}, pages={39–47} }
 @article{kingsbury_flotron_zhu_call_coronell_2018, title={Junction Potentials Bias Measurements of Ion Exchange Membrane Permselectivity}, volume={52}, ISSN={["1520-5851"]}, DOI={10.1021/acs.est.7b05317}, abstractNote={Ion exchange membranes (IEMs) are versatile materials relevant to a variety of water and waste treatment, energy production, and industrial separation processes. The defining characteristic of IEMs is their ability to selectively allow positive or negative ions to permeate, which is referred to as permselectivity. Measured values of permselectivity that equal unity (corresponding to a perfectly selective membrane) or exceed unity (theoretically impossible) have been reported for cation exchange membranes (CEMs). Such nonphysical results call into question our ability to correctly measure this crucial membrane property. Because weighing errors, temperature, and measurement uncertainty have been shown to not explain these anomalous permselectivity results, we hypothesized that a possible explanation are junction potentials that occur at the tips of reference electrodes. In this work, we tested this hypothesis by comparing permselectivity values obtained from bare Ag/AgCl wire electrodes (which have no junction) to values obtained from single-junction reference electrodes containing two different electrolytes. We show that permselectivity values obtained using reference electrodes with junctions were greater than unity for CEMs. In contrast, electrodes without junctions always produced permselectivities lower than unity. Electrodes with junctions also resulted in artificially low permselectivity values for AEMs compared to electrodes without junctions. Thus, we conclude that junctions in reference electrodes introduce two biases into results in the IEM literature: (i) permselectivity values larger than unity for CEMs and (ii) lower permselectivity values for AEMs compared to those for CEMs. These biases can be avoided by using electrodes without a junction.}, number={8}, journal={ENVIRONMENTAL SCIENCE & TECHNOLOGY}, author={Kingsbury, Ryan S. and Flotron, Sophie and Zhu, Shan and Call, Douglas F. and Coronell, Orlando}, year={2018}, month={Apr}, pages={4929–4936} }
 @article{liu_coronell_call_2017, title={Electricity generation using continuously recirculated flow electrodes in reverse electrodialysis}, volume={355}, ISSN={0378-7753}, url={http://dx.doi.org/10.1016/j.jpowsour.2017.04.061}, DOI={10.1016/j.jpowsour.2017.04.061}, abstractNote={Capacitive flow electrode systems that generate electricity from salinity gradients are limited by low power densities, inefficient electrical current collection, and complex system operation. We show here the proof-of-concept that a single reverse electrodialysis cell using continuously recirculated activated carbon flow electrodes can generate uninterrupted electricity from an artificial sea/river water gradient. Power densities reached 61 ± 5.7 mW m−2 (normalized to total membrane surface area) and current densities 2.4 ± 0.13 A m−2 when a 10% by weight carbon loading was used with graphite plate current collectors. Using high-surface area graphite brush current collectors, maximum power densities increased more than 320% to 260 ± 8.7 mW m−2 and maximum current densities more than 400% to 14 ± 0.59 A m−2. The performance improvements were attributed to a more than 80% decrease in electrode resistances when brushes were used instead of plates. A control static capacitive electrode system obtained slightly higher average power densities (290 ± 8.7 mW m−2), but could not produce it continuously, highlighting the operational advantage of the recirculated flow electrode design.}, journal={Journal of Power Sources}, publisher={Elsevier BV}, author={Liu, Fei and Coronell, Orlando and Call, Douglas F.}, year={2017}, month={Jul}, pages={206–210} }
 @article{kingsbury_liu_zhu_boggs_armstrong_call_coronell_2017, title={Impact of natural organic matter and inorganic solutes on energy recovery from five real salinity gradients using reverse electrodialysis}, volume={541}, ISSN={["1873-3123"]}, DOI={10.1016/j.memsci.2017.07.038}, abstractNote={“Blue energy” technologies such as reverse electrodialysis (RED) have received significant research attention over the last several years as a means of generating clean electricity from natural salinity gradients (e.g., seawater and river water). To date, however, knowledge of RED is largely based on synthetic sodium chloride solutions that simulate natural waters. Accordingly, in this work we measured the RED performance of five real water pairs, including seawater, river water, desalination brine, saline wastewater from a pickling plant, and treated wastewater. We compared the performance of each real water pair with that of synthetic control waters to investigate the individual impacts of inorganic constituents (e.g., multivalent ions) and natural organic matter (NOM). Our results indicate that the presence of NOM has a larger impact on power density than ionic composition. Specifically, NOM reduced power densities by up to 43%, while inorganic constituents reduced power densities by up to 8% compared to control waters. Furthermore, UV-absorbing NOM present in the dilute compartment of the RED stack was strongly associated with reduced membrane permselectivity and energy efficiency. Taken together, our findings highlight the important role of organic matter in determining the RED performance of real waters.}, journal={JOURNAL OF MEMBRANE SCIENCE}, author={Kingsbury, R. S. and Liu, F. and Zhu, S. and Boggs, C. and Armstrong, M. D. and Call, D. F. and Coronell, O.}, year={2017}, month={Nov}, pages={621–632} }
 @article{siegert_yates_call_zhu_spormann_logan_2016, title={Correction to Comparison of Nonprecious Metal Cathode Materials for Methane Production by Electromethanogenesis}, volume={4}, ISSN={2168-0485 2168-0485}, url={http://dx.doi.org/10.1021/ACSSUSCHEMENG.6B01763}, DOI={10.1021/ACSSUSCHEMENG.6B01763}, abstractNote={[This corrects the article DOI: 10.1021/sc400520x.].}, number={9}, journal={ACS Sustainable Chemistry & Engineering}, publisher={American Chemical Society (ACS)}, author={Siegert, Michael and Yates, Matthew D. and Call, Douglas F. and Zhu, Xiuping and Spormann, Alfred and Logan, Bruce E.}, year={2016}, month={Aug}, pages={5088–5088} }
 @misc{cheng_call_2016, title={Hardwiring microbes via direct interspecies electron transfer: mechanisms and applications}, volume={18}, ISSN={["2050-7895"]}, DOI={10.1039/c6em00219f}, abstractNote={Direct interspecies electron transfer (DIET) has important implications for the design and operation of biological treatment processes.}, number={8}, journal={ENVIRONMENTAL SCIENCE-PROCESSES & IMPACTS}, author={Cheng, Qiwen and Call, Douglas F.}, year={2016}, month={Aug}, pages={968–980} }
 @article{hartline_call_2016, title={Substrate and electrode potential affect electrotrophic activity of inverted bioanodes}, volume={110}, ISSN={["1878-562X"]}, DOI={10.1016/j.bioelechem.2016.02.010}, abstractNote={Electricity-consuming microbial communities can serve as biocathodic catalysts in microbial electrochemical technologies. Initiating their functionality, however, remains a challenge. One promising approach is the polarity inversion of bioanodes. The objective of this study was to examine the impact of bioanode substrate and electrode potentials on inverted electrotrophic activity. Bioanodes derived from domestic wastewater were operated at − 0.15 V or + 0.15 V (vs. standard hydrogen electrode) with either acetate or formate as the sole carbon source. After this enrichment phase, cathodic linear sweep voltammetry and polarization revealed that formate-enriched cultures consumed almost 20 times the current (− 3.0 ± 0.78 mA; − 100 ± 26 A/m3) than those established with acetate (− 0.16 ± 0.09 mA; − 5.2 ± 2.9 A/m3). The enrichment electrode potential had an appreciable impact for formate, but not acetate, adapted cultures, with the + 0.15 V enrichment generating twice the cathodic current of the − 0.15 V enrichment. The total charge consumed during cathodic polarization was comparable to the charge released during subsequent anodic polarization for the formate-adapted cultures, suggesting that these communities accumulated charge or generated reduced products that could be rapidly oxidized. These findings imply that it may be possible to optimize electrotrophic activity through specific bioanodic enrichment procedures.}, journal={BIOELECTROCHEMISTRY}, author={Hartline, Rosanna M. and Call, Douglas F.}, year={2016}, month={Aug}, pages={13–18} }
 @article{fraiwan_call_choi_2014, title={Bacterial growth and respiration in laminar flow microbial fuel cells}, volume={6}, ISSN={1941-7012}, url={http://dx.doi.org/10.1063/1.4873399}, DOI={10.1063/1.4873399}, abstractNote={Application of micro-scale microbial fuel cells (MFCs) to power electronics is limited due to the high internal resistances associated with membranes. Laminar flow MFCs (LFMFCs) provide an advantage over conventional designs because the anode and the cathode are naturally separated due to the laminar flow regime that develops within the reactor, eliminating the need for membranes. However, our ability to fully harness the potential of LFMFC technology lags from a lack of in-depth understanding of anode/cathode analyte mixing and fundamental factors that maximize LFMFC's power-generating capabilities. We, therefore, investigated the anode colonization and respiration of the known exoelectrogenic bacterium, Geobacter sulfurreducens, in a micro-scale LFMFC. Current production was dependent on the location of the anode relative to the influent in continuous-flow operation, with the highest current density of 6.5 μA/cm2 recorded closest to the influent. Lateral diffusion of anode/cathode analytes, in addition to upstream substrate consumption, likely resulted in the observed differences in current production. As current increased, the number of bacterial cells on the anode measured using simultaneous microscopic observation, also increased. Although the current density obtained here was substantially lower than other micro-sized MFCs, these findings show that micro-scale LFMFCs adapted to microscopic observation can provide a unique tool for better understanding real-time anode colonization and overall reactor performance.}, number={2}, journal={Journal of Renewable and Sustainable Energy}, publisher={AIP Publishing}, author={Fraiwan, Arwa and Call, Douglas F. and Choi, Seokheun}, year={2014}, month={Mar}, pages={023125} }
 @article{siegert_yates_call_zhu_spormann_logan_2014, title={Comparison of Nonprecious Metal Cathode Materials for Methane Production by Electromethanogenesis}, volume={2}, ISSN={2168-0485 2168-0485}, url={http://dx.doi.org/10.1021/sc400520x}, DOI={10.1021/sc400520x}, abstractNote={In methanogenic microbial electrolysis cells (MMCs), CO2 is reduced to methane using a methanogenic biofilm on the cathode by either direct electron transfer or evolved hydrogen. To optimize methane generation, we examined several cathode materials: plain graphite blocks, graphite blocks coated with carbon black or carbon black containing metals (platinum, stainless steel or nickel) or insoluble minerals (ferrihydrite, magnetite, iron sulfide, or molybdenum disulfide), and carbon fiber brushes. Assuming a stoichiometric ratio of hydrogen (abiotic):methane (biotic) of 4:1, methane production with platinum could be explained solely by hydrogen production. For most other materials, however, abiotic hydrogen production rates were insufficient to explain methane production. At −600 mV, platinum on carbon black had the highest abiotic hydrogen gas formation rate (1600 ± 200 nmol cm–3 d–1) and the highest biotic methane production rate (250 ± 90 nmol cm–3 d–1). At −550 mV, plain graphite (76 nmol cm–3 d–1) performed similarly to platinum (73 nmol cm–3 d–1). Coulombic recoveries, based on the measured current and evolved gas, were initially greater than 100% for all materials except platinum, suggesting that cathodic corrosion also contributed to electromethanogenic gas production.}, number={4}, journal={ACS Sustainable Chemistry & Engineering}, publisher={American Chemical Society (ACS)}, author={Siegert, Michael and Yates, Matthew D. and Call, Douglas F. and Zhu, Xiuping and Spormann, Alfred and Logan, Bruce E.}, year={2014}, month={Feb}, pages={910–917} }
 @article{sun_call_wang_cheng_logan_2014, title={Geobacter sp SD-1 with enhanced electrochemical activity in high-salt concentration solutions}, volume={6}, ISSN={["1758-2229"]}, DOI={10.1111/1758-2229.12193}, abstractNote={Summary}, number={6}, journal={ENVIRONMENTAL MICROBIOLOGY REPORTS}, author={Sun, Dan and Call, Douglas and Wang, Aijie and Cheng, Shaoan and Logan, Bruce E.}, year={2014}, month={Dec}, pages={723–729} }
 @article{fraiwan_adusumilli_han_steckl_call_westgate_choi_2014, title={Microbial Power-Generating Capabilities on Micro-/Nano-Structured Anodes in Micro-SizedMicrobial Fuel Cells}, volume={14}, ISSN={["1615-6854"]}, DOI={10.1002/fuce.201400041}, abstractNote={Abstract}, number={6}, journal={FUEL CELLS}, author={Fraiwan, A. and Adusumilli, S. P. and Han, D. and Steckl, A. J. and Call, D. F. and Westgate, C. R. and Choi, S.}, year={2014}, month={Dec}, pages={801–809} }
 @article{zhang_xia_luo_sun_call_logan_2013, title={Improving startup performance with carbon mesh anodes in separator electrode assembly microbial fuel cells}, volume={133}, ISSN={0960-8524}, url={http://dx.doi.org/10.1016/j.biortech.2013.01.036}, DOI={10.1016/j.biortech.2013.01.036}, abstractNote={In a separator electrode assembly microbial fuel cell, oxygen crossover from the cathode inhibits current generation by exoelectrogenic bacteria, resulting in poor reactor startup and performance. To determine the best approach for improving startup performance, the effect of acclimation to a low set potential (−0.2 V, versus standard hydrogen electrode) was compared to startup at a higher potential (+0.2 V) or no set potential, and inoculation with wastewater or pre-acclimated cultures. Anodes acclimated to −0.2 V produced the highest power of 1330 ± 60 mW m−2 for these different anode conditions, but unacclimated wastewater inocula produced inconsistent results despite the use of this set potential. By inoculating reactors with transferred cell suspensions, however, startup time was reduced and high power was consistently produced. These results show that pre-acclimation at −0.2 V consistently improves power production compared to use of a more positive potential or the lack of a set potential.}, journal={Bioresource Technology}, publisher={Elsevier BV}, author={Zhang, Fang and Xia, Xue and Luo, Yong and Sun, Dan and Call, Douglas F. and Logan, Bruce E.}, year={2013}, month={Apr}, pages={74–81} }
 @article{yates_kiely_call_rismani-yazdi_bibby_peccia_regan_logan_2012, title={Convergent development of anodic bacterial communities in microbial fuel cells}, volume={6}, ISSN={1751-7362 1751-7370}, url={http://dx.doi.org/10.1038/ismej.2012.42}, DOI={10.1038/ismej.2012.42}, abstractNote={Abstract}, number={11}, journal={The ISME Journal}, publisher={Springer Nature}, author={Yates, Matthew D and Kiely, Patrick D and Call, Douglas F and Rismani-Yazdi, Hamid and Bibby, Kyle and Peccia, Jordan and Regan, John M and Logan, Bruce E}, year={2012}, month={May}, pages={2002–2013} }
 @article{pisciotta_zaybak_call_nam_logan_2012, title={Enrichment of Microbial Electrolysis Cell Biocathodes from Sediment Microbial Fuel Cell Bioanodes}, volume={78}, ISSN={0099-2240 1098-5336}, url={http://dx.doi.org/10.1128/aem.00480-12}, DOI={10.1128/aem.00480-12}, abstractNote={ABSTRACT}, number={15}, journal={Applied and Environmental Microbiology}, publisher={American Society for Microbiology}, author={Pisciotta, John M. and Zaybak, Zehra and Call, Douglas F. and Nam, Joo-Youn and Logan, Bruce E.}, year={2012}, month={May}, pages={5212–5219} }
 @article{call_logan_2011, title={A method for high throughput bioelectrochemical research based on small scale microbial electrolysis cells}, volume={26}, ISSN={0956-5663}, url={http://dx.doi.org/10.1016/j.bios.2011.05.014}, DOI={10.1016/j.bios.2011.05.014}, abstractNote={There is great interest in studying exoelectrogenic microorganisms, but existing methods can require expensive electrochemical equipment and specialized reactors. We developed a simple system for conducting high throughput bioelectrochemical research using multiple inexpensive microbial electrolysis cells (MECs) built with commercially available materials and operated using a single power source. MECs were small crimp top serum bottles (5 mL) with a graphite plate anode (92 m2/m3) and a cathode of stainless steel (SS) mesh (86 m2/m3), graphite plate, SS wire, or platinum wire. The highest volumetric current density (240 A/m3, applied potential of 0.7 V) was obtained using a SS mesh cathode and a wastewater inoculum (acetate electron donor). Parallel operated MECs (single power source) did not lead to differences in performance compared to non-parallel operated MECs, which can allow for high throughput reactor operation (>1000 reactors) using a single power supply. The utility of this method for cultivating exoelectrogenic microorganisms was demonstrated through comparison of buffer effects on pure (Geobacter sulfurreducens and Geobacter metallireducens) and mixed cultures. Mixed cultures produced current densities equal to or higher than pure cultures in the different media, and current densities for all cultures were higher using a 50 mM phosphate buffer than a 30 mM bicarbonate buffer. Only the mixed culture was capable of sustained current generation with a 200 mM phosphate buffer. These results demonstrate the usefulness of this inexpensive method for conducting in-depth examinations of pure and mixed exoelectrogenic cultures.}, number={11}, journal={Biosensors and Bioelectronics}, publisher={Elsevier BV}, author={Call, Douglas F. and Logan, Bruce E.}, year={2011}, month={Jul}, pages={4526–4531} }
 @article{hong_call_werner_logan_2011, title={Adaptation to high current using low external resistances eliminates power overshoot in microbial fuel cells}, volume={28}, ISSN={0956-5663}, url={http://dx.doi.org/10.1016/j.bios.2011.06.045}, DOI={10.1016/j.bios.2011.06.045}, abstractNote={One form of power overshoot commonly observed with mixed culture microbial fuel cells (MFCs) is doubling back of the power density curve at higher current densities, but the reasons for this type of overshoot have not been well explored. To investigate this, MFCs were acclimated to different external resistances, producing a range of anode potentials and current densities. Power overshoot was observed for reactors acclimated to higher (500 and 5000 Ω) but not lower (5 and 50 Ω) resistances. Acclimation of the high external resistance reactors for a few cycles to low external resistance (5 Ω), and therefore higher current densities, eliminated power overshoot. MFCs initially acclimated to low external resistances exhibited both higher current in cyclic voltammograms (CVs) and higher levels of redox activity over a broader range of anode potentials (−0.4 to 0 V; vs. a Ag/AgCl electrode) based on first derivative cyclic voltammetry (DCV) plots. Reactors acclimated to higher external resistances produced lower current in CVs, exhibited lower redox activity over a narrower anode potential range (−0.4 to −0.2 V vs. Ag/AgCl), and failed to produce higher currents above ∼−0.3 V (vs. Ag/AgCl). After the higher resistance reactors were acclimated to the lowest resistance they also exhibited similar CV and DCV profiles. Our findings show that to avoid overshoot, prior to the polarization and power density tests the anode biofilm must adapt to low external resistances to be capable of higher currents.}, number={1}, journal={Biosensors and Bioelectronics}, publisher={Elsevier BV}, author={Hong, Yiying and Call, Douglas F. and Werner, Craig M. and Logan, Bruce E.}, year={2011}, month={Oct}, pages={71–76} }
 @article{kiely_cusick_call_selembo_regan_logan_2011, title={Anode microbial communities produced by changing from microbial fuel cell to microbial electrolysis cell operation using two different wastewaters}, volume={102}, ISSN={0960-8524}, url={http://dx.doi.org/10.1016/j.biortech.2010.05.019}, DOI={10.1016/j.biortech.2010.05.019}, abstractNote={Conditions in microbial fuel cells (MFCs) differ from those in microbial electrolysis cells (MECs) due to the intrusion of oxygen through the cathode and the release of H2 gas into solution. Based on 16S rRNA gene clone libraries, anode communities in reactors fed acetic acid decreased in species richness and diversity, and increased in numbers of Geobacter sulfurreducens, when reactors were shifted from MFCs to MECs. With a complex source of organic matter (potato wastewater), the proportion of Geobacteraceae remained constant when MFCs were converted into MECs, but the percentage of clones belonging to G. sulfurreducens decreased and the percentage of G. metallireducens clones increased. A dairy manure wastewater-fed MFC produced little power, and had more diverse microbial communities, but did not generate current in an MEC. These results show changes in Geobacter species in response to the MEC environment and that higher species diversity is not correlated with current.}, number={1}, journal={Bioresource Technology}, publisher={Elsevier BV}, author={Kiely, Patrick D. and Cusick, Roland and Call, Douglas F. and Selembo, Priscilla A. and Regan, John M. and Logan, Bruce E.}, year={2011}, month={Jan}, pages={388–394} }
 @article{liu_yates_cheng_call_sun_logan_2011, title={Examination of microbial fuel cell start-up times with domestic wastewater and additional amendments}, volume={102}, ISSN={0960-8524}, url={http://dx.doi.org/10.1016/j.biortech.2011.04.087}, DOI={10.1016/j.biortech.2011.04.087}, abstractNote={Rapid startup of microbial fuel cells (MFCs) and other bioreactors is desirable when treating wastewaters. The startup time with unamended wastewater (118 h) was similar to that obtained by adding acetate or fumarate (110-115 h), and less than that with glucose (181 h) or Fe(III) (353 h). Initial current production took longer when phosphate buffer was added, with startup times increasing with concentration from 149 h (25 mM) to 251 h (50 mM) and 526 h (100 mM). Microbial communities that developed in the reactors contained Betaproteobacteria, Acetoanaerobium noterae, and Chlorobium sp. Anode biomass densities ranged from 200 to 600 μg/cm(2) for all amendments except Fe(Ш) (1650 μg/cm(2)). Wastewater produced 91 mW/m(2), with the other MFCs producing 50 mW/m(2) (fumarate) to 103mW/m(2) (Fe(III)) when amendments were removed. These experiments show that wastewater alone is sufficient to acclimate the reactor without the need for additional chemical amendments.}, number={15}, journal={Bioresource Technology}, publisher={Elsevier BV}, author={Liu, Guangli and Yates, Matthew D. and Cheng, Shaoan and Call, Douglas F. and Sun, Dan and Logan, Bruce E.}, year={2011}, month={Aug}, pages={7301–7306} }
 @article{call_logan_2011, title={Lactate Oxidation Coupled to Iron or Electrode Reduction by Geobacter sulfurreducens PCA}, volume={77}, ISSN={0099-2240 1098-5336}, url={http://dx.doi.org/10.1128/aem.06434-11}, DOI={10.1128/aem.06434-11}, abstractNote={ABSTRACT}, number={24}, journal={Applied and Environmental Microbiology}, publisher={American Society for Microbiology}, author={Call, Douglas F. and Logan, Bruce E.}, year={2011}, month={Oct}, pages={8791–8794} }
 @article{sun_call_kiely_wang_logan_2011, title={Syntrophic interactions improve power production in formic acid fed MFCs operated with set anode potentials or fixed resistances}, volume={109}, ISSN={0006-3592}, url={http://dx.doi.org/10.1002/bit.23348}, DOI={10.1002/bit.23348}, abstractNote={Abstract}, number={2}, journal={Biotechnology and Bioengineering}, publisher={Wiley}, author={Sun, Dan and Call, Douglas F. and Kiely, Patrick D. and Wang, Aijie and Logan, Bruce E.}, year={2011}, month={Oct}, pages={405–414} }
 @article{kiely_call_yates_regan_logan_2010, title={Anodic biofilms in microbial fuel cells harbor low numbers of higher-power-producing bacteria than abundant genera}, volume={88}, ISSN={0175-7598 1432-0614}, url={http://dx.doi.org/10.1007/s00253-010-2757-2}, DOI={10.1007/s00253-010-2757-2}, abstractNote={Microbial fuel cell (MFC) anode communities often reveal just a few genera, but it is not known to what extent less abundant bacteria could be important for improving performance. We examined the microbial community in an MFC fed with formic acid for more than 1 year and determined using 16S rRNA gene cloning and fluorescent in situ hybridization that members of the Paracoccus genus comprised most (approximately 30%) of the anode community. A Paracoccus isolate obtained from this biofilm (Paracoccus denitrificans strain PS-1) produced only 5.6 mW/m(2), whereas the original mixed culture produced up to 10 mW/m(2). Despite the absence of any Shewanella species in the clone library, we isolated a strain of Shewanella putrefaciens (strain PS-2) from the same biofilm capable of producing a higher-power density (17.4 mW/m(2)) than the mixed culture, although voltage generation was variable. Our results suggest that the numerical abundance of microorganisms in biofilms cannot be assumed a priori to correlate to capacities of these predominant species for high-power production. Detailed screening of bacterial biofilms may therefore be needed to identify important strains capable of high-power generation for specific substrates.}, number={1}, journal={Applied Microbiology and Biotechnology}, publisher={Springer Science and Business Media LLC}, author={Kiely, Patrick D. and Call, Douglas F. and Yates, Matthew D. and Regan, John M. and Logan, Bruce E.}, year={2010}, month={Jul}, pages={371–380} }
 @article{mehanna_kiely_call_logan_2010, title={Microbial Electrodialysis Cell for Simultaneous Water Desalination and Hydrogen Gas Production}, volume={44}, ISSN={0013-936X 1520-5851}, url={http://dx.doi.org/10.1021/es1025646}, DOI={10.1021/es1025646}, abstractNote={A new approach to water desalination is to use exoelectrogenic bacteria to generate electrical power from the biodegradation of organic matter, moving charged ions from a middle chamber between two membranes in a type of microbial fuel cell called a microbial desalination cell. Desalination efficiency using this approach is limited by the voltage produced by the bacteria. Here we examine an alternative strategy based on boosting the voltage produced by the bacteria to achieve hydrogen gas evolution from the cathode using a three-chambered system we refer to as a microbial electrodialysis cell (MEDC). We examined the use of the MEDC process using two different initial NaCl concentrations of 5 g/L and 20 g/L. Conductivity in the desalination chamber was reduced by up to 68 ± 3% in a single fed-batch cycle, with electrical energy efficiencies reaching 231 ± 59%, and maximum hydrogen production rates of 0.16 ± 0.05 m(3) H(2)/m(3) d obtained at an applied voltage of 0.55 V. The advantage of this system compared to a microbial fuel cell approach is that the potentials between the electrodes can be better controlled, and the hydrogen gas that is produced can be used to recover energy to make the desalination process self-sustaining with respect to electrical power requirements.}, number={24}, journal={Environmental Science & Technology}, publisher={American Chemical Society (ACS)}, author={Mehanna, Maha and Kiely, Patrick D. and Call, Douglas F. and Logan, Bruce. E.}, year={2010}, month={Dec}, pages={9578–9583} }
 @article{wagner_call_logan_2010, title={Optimal Set Anode Potentials Vary in Bioelectrochemical Systems}, volume={44}, ISSN={0013-936X 1520-5851}, url={http://dx.doi.org/10.1021/es101013e}, DOI={10.1021/es101013e}, abstractNote={In bioelectrochemical systems (BESs), the anode potential can be set to a fixed voltage using a potentiostat, but there is no accepted method for defining an optimal potential. Microbes can theoretically gain more energy by reducing a terminal electron acceptor with a more positive potential, for example oxygen compared to nitrate. Therefore, more positive anode potentials should allow microbes to gain more energy per electron transferred than a lower potential, but this can only occur if the microbe has metabolic pathways capable of capturing the available energy. Our review of the literature shows that there is a general trend of improved performance using more positive potentials, but there are several notable cases where biofilm growth and current generation improved or only occurred at more negative potentials. This suggests that even with diverse microbial communities, it is primarily the potential of the terminal respiratory proteins used by certain exoelectrogenic bacteria, and to a lesser extent the anode potential, that determines the optimal growth conditions in the reactor. Our analysis suggests that additional bioelectrochemical investigations of both pure and mixed cultures, over a wide range of potentials, are needed to better understand how to set and evaluate optimal anode potentials for improving BES performance.}, number={16}, journal={Environmental Science & Technology}, publisher={American Chemical Society (ACS)}, author={Wagner, Rachel C. and Call, Douglas F. and Logan, Bruce E.}, year={2010}, month={Aug}, pages={6036–6041} }
 @article{cheng_xing_call_logan_2009, title={Direct Biological Conversion of Electrical Current into Methane by Electromethanogenesis}, volume={43}, ISSN={0013-936X 1520-5851}, url={http://dx.doi.org/10.1021/es803531g}, DOI={10.1021/es803531g}, abstractNote={New sustainable methods are needed to produce renewable energy carriers that can be stored and used for transportation, heating, or chemical production. Here we demonstrate that methane can directly be produced using a biocathode containing methanogens in electrochemical systems (abiotic anode) or microbial electrolysis cells (MECs; biotic anode) by a process called electromethanogenesis. At a set potential of less than -0.7 V (vs Ag/AgCl), carbon dioxide was reduced to methane using a two-chamber electrochemical reactor containing an abiotic anode, a biocathode, and no precious metal catalysts. At -1.0 V, the current capture efficiency was 96%. Electrochemical measurements made using linear sweep voltammetry showed that the biocathode substantially increased current densities compared to a plain carbon cathode where only small amounts of hydrogen gas could be produced. Both increased current densities and very small hydrogen production rates by a plain cathode therefore support a mechanism of methane production directly from current and not from hydrogen gas. The biocathode was dominated by a single Archaeon, Methanobacterium palustre. When a current was generated by an exoelectrogenic biofilm on the anode growing on acetate in a single-chamber MEC, methane was produced at an overall energy efficiency of 80% (electrical energy and substrate heat of combustion). These results show that electromethanogenesis can be used to convert electrical current produced from renewable energy sources (such as wind, solar, or biomass) into a biofuel (methane) as well as serving as a method for the capture of carbon dioxide.}, number={10}, journal={Environmental Science & Technology}, publisher={American Chemical Society (ACS)}, author={Cheng, Shaoan and Xing, Defeng and Call, Douglas F. and Logan, Bruce E.}, year={2009}, month={May}, pages={3953–3958} }
 @article{call_merrill_logan_2009, title={High Surface Area Stainless Steel Brushes as Cathodes in Microbial Electrolysis Cells}, volume={43}, ISSN={0013-936X 1520-5851}, url={http://dx.doi.org/10.1021/es803074x}, DOI={10.1021/es803074x}, abstractNote={Microbial electrolysis cells (MECs) are an efficient technology for generating hydrogen gas from organic matter, but alternatives to precious metals are needed for cathode catalysts. We show here that high surface area stainless steel brush cathodes produce hydrogen at rates and efficiencies similar to those achieved with platinum-catalyzed carbon cloth cathodes in single-chamber MECs. Using a stainless steel brush cathode with a specific surface area of 810 m2/m3, hydrogen was produced at a rate of 1.7 +/- 0.1 m3-H2/m3-d (current density of 188 +/- 10 A/m3) at an applied voltage of 0.6 V. The energy efficiency relative to the electrical energy input was 221 +/- 8%, and the overall energy efficiency was 78 +/- 5% based on both electrical energy and substrate utilization. These values compare well to previous results obtained using platinum on flat carbon cathodes in a similar system. Reducing the cathode surface area by 75% decreased performance from 91 +/- 3 A/m3 to 78 +/- 4 A/m3. A brush cathode with graphite instead of stainless steel and a specific surface area of 4600 m2/m3 generated substantially less current (1.7 +/- 0.0 A/m3), and a flat stainless steel cathode (25 m2/m3) produced 64 +/- 1 A/m3, demonstrating that both the stainless steel and the large surface area contributed to high current densities. Linear sweep voltammetry showed that the stainless steel brush cathodes both reduced the overpotential needed for hydrogen evolution and exhibited a decrease in overpotential over time as a result of activation. These results demonstrate for the first time that hydrogen production can be achieved at rates comparable to those with precious metal catalysts in MECs without the need for expensive cathodes.}, number={6}, journal={Environmental Science & Technology}, publisher={American Chemical Society (ACS)}, author={Call, Douglas F. and Merrill, Matthew D. and Logan, Bruce E.}, year={2009}, month={Mar}, pages={2179–2183} }
 @article{call_wagner_logan_2009, title={Hydrogen Production by Geobacter Species and a Mixed Consortium in a Microbial Electrolysis Cell}, volume={75}, ISSN={0099-2240}, url={http://dx.doi.org/10.1128/aem.01760-09}, DOI={10.1128/aem.01760-09}, abstractNote={ABSTRACT}, number={24}, journal={Applied and Environmental Microbiology}, publisher={American Society for Microbiology}, author={Call, D. F. and Wagner, R. C. and Logan, B. E.}, year={2009}, month={Oct}, pages={7579–7587} }
 @article{call_logan_2008, title={Hydrogen Production in a Single Chamber Microbial Electrolysis Cell Lacking a Membrane}, volume={42}, ISSN={0013-936X 1520-5851}, url={http://dx.doi.org/10.1021/es8001822}, DOI={10.1021/es8001822}, abstractNote={Hydrogen gas can be produced by electrohydrogenesis in microbial electrolysis cells (MECs) at greater yields than fermentation and at greater energy efficiencies than water electrolysis. It has been assumed that a membrane is needed in an MEC to avoid hydrogen losses due to bacterial consumption of the product gas. However, high cathodic hydrogen recoveries (78 +/- 1% to 96 +/- 1%) were achieved in an MEC despite the absence of a membrane between the electrodes (applied voltages of 0.3 < E(ap) < 0.8 V; 7.5 mS/cm solution conductivity). Through the use of a membrane-less system, a graphite fiber brush anode, and close electrode spacing, hydrogen production rates reached a maximum of 3.12 +/- 0.02 m3 H2/m3 reactor per day (292 +/- 1 A/m3) at an applied voltage of E(ap) = 0.8 V. This production rate is more than double that obtained in previous MEC studies. The energy efficiency relative to the electrical input decreased with applied voltage from 406 +/- 6% (E(ap) = 0.3 V) to 194 +/- 2% (E(ap) = 0.8 V). Overall energy efficiency relative to both E(ap) and energy of the substrate averaged 78 +/- 4%, with a maximum of 86 +/- 2% (1.02 +/- 0.05 m3 H2/m3 day, E(ap) = 0.4 V). At E(ap) = 0.2 V, the hydrogen recovery substantially decreased, and methane concentrations increased from an average of 1.9 +/- 1.3% (E(ap) = 0.3-0.8 V) to 28 +/- 0% of the gas, due to the long cycle time of the reactor. Increasing the solution conductivity to 20 mS/ cm increased hydrogen production rates for E(ap) = 0.3-0.6 V, but consistent reactor performance could not be obtained in the high conductivity solution at E(ap) > 0.6 V. These results demonstrate that high hydrogen recovery and production rates are possible in a single chamber MEC without a membrane, potentially reducing the costs of these systems and allowing for new and simpler designs.}, number={9}, journal={Environmental Science & Technology}, publisher={American Chemical Society (ACS)}, author={Call, Douglas and Logan, Bruce E.}, year={2008}, month={May}, pages={3401–3406} }
 @article{logan_call_cheng_hamelers_sleutels_jeremiasse_rozendal rené a._2008, title={Microbial Electrolysis Cells for High Yield Hydrogen Gas Production from Organic Matter}, volume={42}, ISSN={0013-936X 1520-5851}, url={http://dx.doi.org/10.1021/es801553z}, DOI={10.1021/es801553z}, abstractNote={The use of electrochemically active bacteria to break down organic matter, combined with the addition of a small voltage (> 0.2 V in practice) in specially designed microbial electrolysis cells (MECs), can result in a high yield of hydrogen gas. While microbial electrolysis was invented only a few years ago, rapid developments have led to hydrogen yields approaching 100%, energy yields based on electrical energy input many times greater than that possible by water electrolysis, and increased gas production rates. MECs used to make hydrogen gas are similar in design to microbial fuel cells (MFCs) that produce electricity, but there are important differences in architecture and analytical methods used to evaluate performance. We review here the materials, architectures, performance, and energy efficiencies of these MEC systems that show promise as a method for renewable and sustainable energy production, and wastewater treatment.}, number={23}, journal={Environmental Science & Technology}, publisher={American Chemical Society (ACS)}, author={Logan, Bruce E. and Call, Douglas and Cheng, Shaoan and Hamelers, Hubertus V. M. and Sleutels, Tom H. J. A. and Jeremiasse, Adriaan W. and Rozendal René A.}, year={2008}, month={Dec}, pages={8630–8640} }
 @article{zuo_cheng_call_logan_2007, title={Tubular Membrane Cathodes for Scalable Power Generation in Microbial Fuel Cells}, volume={41}, ISSN={0013-936X 1520-5851}, url={http://dx.doi.org/10.1021/es0627601}, DOI={10.1021/es0627601}, abstractNote={One of the greatest challenges for using microbial fuel cells (MFCs) for wastewater treatment is creating a scalable architecture that provides large surface areas for oxygen reduction at the cathode and bacteria growth on the anode. We demonstrate here a scalable cathode concept by showing that a tubular ultrafiltration membrane with a conductive graphite coating and a nonprecious metal catalyst (CoTMPP) can be used to produce power in an MFC. Using a carbon paper anode (surface area Aan = 7 cm2, surface area per reactor volume Aan,s = 25 m2/m3), an MFC with two 3-cm tube cathodes (Acat = 27 cm2, Acat,s = 84 m2/m3) generated up to 8.8 W/m3 (403 mW/m2) using glucose [0.8 g/L in a 50 mM phosphate buffer solution (PBS)], which was only slightly less than that produced using a carbon paper cathode with a Pt catalyst (9.9 W/m3, 394 mW/m2; Acat= 7 cm2, Acat,s= 25 m2/m3). Coulombic efficiencies (CEs) with carbon paper anodes were 25-40% with tube cathodes (CoTMPP), compared to 7-19% with a carbon paper cathode. When a high-surface-area graphite brush anode was used (Aan = 2235 cm2, Aan,s = 7700 m2/m3) with two tube cathodes placed inside the reactor (Acat = 27 cm2, Acas, = 93 m2/m3), the MFC produced 17.7 W/m3 with a CE = 70-74% (200 mM PBS). Further increases in the surface area of the tube cathodes to 54 cm2 (120 m2/m3) increased the total power output (from 0.51 to 0.83 mW), but the increase in volume resulted in a constant volumetric power density (approximately 18 W/m3). These results demonstrate that an MFC design using tubular cathodes coated with nonprecious metal catalysts, and brush anodes, is a promising architecture that is intrinsically scalable for creating larger systems. Further increases in power output will be possible through the development of cathodes with lower internal resistances.}, number={9}, journal={Environmental Science & Technology}, publisher={American Chemical Society (ACS)}, author={Zuo, Yi and Cheng, Shaoan and Call, Doug and Logan, Bruce E.}, year={2007}, month={May}, pages={3347–3353} }