John T. Novak

Virginia Polytechnic Institute and State University, Блэксбург, Virginia, United States

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Publications (191)259.88 Total impact

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    ABSTRACT: This study evaluates the biological solid reduction in a conventional activated sludge system with an anoxic/anaerobic side stream reactor receiving 1/10 of return sludge mass. Influent iron concentrations and feeding modes were changed to explore the consistency between the influent iron concentration and yield values and to assess the impact of feeding pattern. The results indicated that sludge reduction occurs during alternately exposure of sludge to aerobic and anoxic/anaerobic conditions in a range of 38-87%. The sludge reduction values reached a maximum level with the higher iron concentrations. Thus, it is concluded that this configuration is more applicable for plants receiving high iron concentrations in the wastewaters. Copyright © 2015. Published by Elsevier Ltd.
    Bioresource Technology 10/2015; 193. DOI:10.1016/j.biortech.2015.06.109 · 5.04 Impact Factor
  • Abhinav Gupta · John T. Novak · Renzun Zhao
    Journal of Environmental Chemical Engineering 08/2015; DOI:10.1016/j.jece.2015.07.029
  • Journal of Environmental Engineering 04/2015; 141(4):04014071. DOI:10.1061/(ASCE)EE.1943-7870.0000904 · 1.22 Impact Factor
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    John T. Novak · Chang Min Park
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    ABSTRACT: This study investigates the effect of landfill age on landfill leachate characteristics; two aspects are focused here. One is ultraviolet absorbance at 254 nm (UV254) property, as the discharge of landfill leachates to publically owned treatment works can cause interference with UV254 disinfection. The other is biorefractory organic nitrogen in leachates, as it can contribute to effluent nitrogen making it difficult to meet stringent effluent nitrogen regulations. To study variation in UV254-absorbing organic carbon and organic nitrogen, leachate samples ranging from cells with ages 2 to 30 y from a large landfill in Kentucky, were collected and fractionated on a basis of their molecular weight and chemical nature into humic acids, fulvic acids and a hydrophilic fraction. The effectiveness of long term landfilling and membrane treatment for organic matter and organic nitrogen removal was examined. Humic materials, which were the major UV254-absorbing substances, were mainly >1 kDa and they degraded significantly with landfill age. The hydrophilic organic fraction, which was the major contributor to organic nitrogen, was mainly <1 kDa and it became increasingly recalcitrant with landfill age. This study provides insight into the characteristics of the different leachate fractions with landfilling age that might aid the design of on-site leachate treatment techniques.
    Waste Management & Research 09/2014; 32(12). DOI:10.1177/0734242X14550739 · 1.11 Impact Factor
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    ABSTRACT: Prior research suggests that cold temperatures may stimulate the proliferation of certain ARGs and gene transfer elements during storage of biosolids. This could have important implications on cold weather storage of biosolids, as often required in northern climates until a time suitable for land application. In this study, levels of an integron-associated gene (intI1) and an ARG (sul1) were monitored in biosolids subject to storage at 4 °C, 10 °C, and 20 °C. Both intI1 and sul1 were observed to increase during short-term storage (less than two months), but the concentrations returned to background within four months. The increases in concentration were more pronounced at lower temperatures than ambient temperatures. Overall the results suggest that cold stress may induce horizontal gene transfer of integron-associated ARGs and that biosolids storage conditions should be considered prior to land application.This article is protected by copyright. All rights reserved.
    Letters in Applied Microbiology 09/2014; 59(6). DOI:10.1111/lam.12325 · 1.75 Impact Factor
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    ABSTRACT: To manage water quality in the Occoquan Reservoir, Virginia, a water reclamation facility discharges nitrified product water that reduces the release of undesirable substances (e.g., phosphorus, iron, and ammonia) from sediments during periods of hypolimnetic anoxia. Results showed that when the oxidized nitrogen (OxN) concentration input to the reservoir was lower than 5 mg N/L during periods of anoxia following thermal stratification, nitrate was depleted in the upper reaches of the reservoir resulting in the release of ammonia and orthophosphate from the sediments downstream. When the OxN input to the reservoir was operationally increased to a concentration greater than 10 mg-N/L, orthophosphate release was suppressed. Introducing OxN to the system decreased sediment ammonia release but did not eliminate it. By discharging reclaimed water that contained nitrate levels greater than 10 mg N/L, reservoir water quality was protected and the discharged nitrate was converted to nitrogen gas as it moved downstream.
    Water Environment Research 02/2014; 86(2):123-33. DOI:10.2175/106143013X13596524517067 · 1.00 Impact Factor
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    ABSTRACT: When landfill leachate, with or without biological pretreatment, is discharged to publically owned treatment works (POTWs), it can interfere with the installed treatment facilities. Biological treatment is ineffective for the removal of some of the bio-refractory organic matter, including UV254 quenching substances. Fenton's reagent treatment for biologically treated landfill leachates is examined in this study as a polishing step to make landfill leachates acceptable to POTWs. The optimum conditions for the Fenton's reagent treatment are explored. The molecular weight and hydrophobic-hydrophilic nature based fractions of the Fenton's treated leachate samples are analyzed to provide insight into the leachate fractions targeted by the Fenton's reagent. The results indicate that Fenton's reagent can act as a good compliment to biological treatment as it can remove leachate fractions which are widely considered to be bio-refractory. It exhibited good UV254 absorbance removal by removing larger molecular weight humic substances and thus, can help solve the UV254 quenching problem due to leachates discharged to POTWs.
    Chemosphere 01/2014; DOI:10.1016/j.chemosphere.2013.12.066 · 3.50 Impact Factor
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    Chang Min Park · John T Novak
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    ABSTRACT: The role of iron addition to sewage sludge prior to anaerobic digestion was evaluated to determine the effect of iron on digestion performance and generation of odor-causing compounds. Hydrogen sulfide (H2S) and volatile organic sulfur compounds (VOSCs) were the odorous gases evaluated in this study. Samples were obtained from seven municipal wastewater treatment plants (WWTPs), and batch anaerobic digestion tests were conducted using primary and secondary sludges at 30 day solids retention time (SRT) under mesophilic conditions. Volatile solid removal (VSR) was highly predictable with background iron concentrations measured in the combined sludge. They were likely to increase as influent iron content increased. 1.25% w/w ferric chloride (FeCl3) was added to the anaerobic digester feed in order to simulate iron addition for sulfide control in full-scale WWTPs. The results showed that it had a positive impact on digestion performance with higher VSR and odor control with reduced H2S and TVOSCs in the headspace gas of dewatered biosolids considered in the tests. Ferric chloride is considered a beneficial additive as a strategy for an odor mitigation, not to mention more efficient digestion under anaerobic conditions.
    Water Science & Technology 12/2013; 68(11):2391-2396. DOI:10.2166/wst.2013.507 · 1.21 Impact Factor
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    ABSTRACT: Water resource recovery facilities have been described as creating breeding ground conditions for the selection, transfer, and dissemination of antibiotic resistance genes (ARGs) among various bacteria. The objective of this study was to determine the effect of direct addition of antibiotic and silver nanoparticles (Ag NPs, or nanosilver) on the occurrence of ARGs in thermophilic anaerobic digesters. Test thermophilic digesters were amended with environmentally-relevant concentrations of Ag NP (0.01, 0.1, and 1.0 mg-Ag/L; corresponding to approximately 0.7, 7.0, and 70 mg-Ag/kg total solids) and sulfamethoxazole (SMX) that span susceptible to resistant classifications (1, 5, and 50 mg/L) as potential selection pressures for ARGs. Tetracycline (tet(O), tet(W)) and sulfonamide (sulI, sulII) ARGs and the integrase enzyme gene (intI1) associated with Class 1 integrons were measured in raw sludge, test thermophilic digesters, a control thermophilic digester, and a control mesophilic digester. There was no apparent effect of Ag NPs on thermophilic anaerobic digester performance. The maximum SMX addition (50 mg/L) resulted in accumulation of volatile fatty acids and low pH, alkalinity, and volatile solids reduction. There was no significant difference between ARG gene copy numbers (absolute or normalized to 16S rRNA genes) in amended thermophilic digesters and the control thermophilic digester. Antibiotic resistance gene copy numbers in digested sludge ranged from 10(3) to 10(6) copies per microL (approximately 8 x10(1) to 8 x 10(4) copies per microg) of sludge as result of a 1-log reduction of ARGs (2-log reduction for intI1). Quantities of the five ARGs in raw sludge ranged from 10(4) to 10(8) copies per microL (approximately 4 x 10(2) to 4 x 10(6) per microg) of sludge. Test and control thermophilic digesters (53 degrees C, 12-day solids retention time [SRT]) consistently reduced but did not eliminate levels of all analyzed genes. The mesophilic digester (37 degrees C, 20-day SRT) also reduced levels of sulI, sulII, and intI1 genes, but levels of tet(O) and tet(W) were the same or higher than in raw sludge. Antibiotic resistance gene reductions remained constant despite the application of selection pressures, which suggests that digester operating conditions are a strong governing factor of the bacterial community composition and thus the prevalence of ARGs.
    Water Environment Research 05/2013; 85(5):411-21. DOI:10.2175/106143012X13373575831394 · 1.00 Impact Factor
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    ABSTRACT: Landfill leachates strongly quench UV light. When discharged to POTWs, leachates can interfere with UV disinfection. To investigate the UV quenching problem of landfill leachates, a variety of landfill leachates with a range of conditions were collected and characterized. The UV blocking component was found to be resistant to biological degradation so they pass through wastewater treatment plants and impact the subsequent UV disinfection system. Leachate samples were fractionated into humic acids (HAs), fulvic Acids (FAs) and hydrophilic (Hpi) fractions to investigate the source of UV absorbing materials. Results show that for all leachates examined, the specific UV254 absorbance (SUVA254) of the three fractions follows: HA>FA>Hpi. However, the overall UV254 absorbance of the Hpi fraction was important because there was more hydrophilic organic matter than humic or fulvic acids. The size distribution was also investigated to provide information about the potential for membrane treatment. It was found that the size distribution of the three fractions follows: HA>FA>Hpi. This indicates that membrane separation following biological treatment is a promising technology for removal of humic substances from landfill leachates. Leachate samples treated in this manner could meet the UV transmittance requirement of the POTWs.
    Journal of hazardous materials 04/2013; 258-259C:1-9. DOI:10.1016/j.jhazmat.2013.04.026 · 4.33 Impact Factor
  • Renzun Zhao · John T Novak · C. Douglas Goldsmith
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    ABSTRACT: To explore the feasible treatment alternatives for organic contaminant, especially organic arsenic species in the landfill gas (LFG) condensate, a variety of treatment approaches were examined and evaluated in this study. Biological degradation, conventional and advanced oxidation, and physical absorption showed limited effectiveness to convert the methylated arsenic to inorganic arsenic. Reverse osmosis (RO) was found to be able to remove the organic arsenic and meet the discharge limits. Maximum removal efficiency and cost level were summarized for all treatment approaches tested, which can be a reference for the organic arsenic treatment method selection under different circumstances.
    Waste Management 02/2013; 33(5). DOI:10.1016/j.wasman.2013.01.013 · 3.16 Impact Factor
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    ABSTRACT: The distribution of natural organic carbon was investigated at a chloroethene-contaminated site where complete reductive dechlorination of tetrachloroethene (PCE) to vinyl chloride and ethene was observed. In this study, operationally defined potentially bioavailable organic carbon (PBOC) was measured in surficial aquifer sediment samples collected at varying depths and locations in the vicinity of a dense nonaqueous phase liquid (DNAPL) source and aqueous phase plume. The relationship between chloroethene concentrations and PBOC levels was examined by comparing differences in extractable organic carbon in aquifer sediments with minimal chloroethene exposure relative to samples collected in the source zone. Using performance-monitoring data, direct correlations with PBOC were also developed with chloroethene concentrations in groundwater. Results show a logarithm-normal distribution for PBOC in aquifer sediments with a mean concentration of 187 mg/kg. PBOC levels in sediments obtained from the underlying confining unit were generally greater when compared to sediments collected in the sandy surficial aquifer. Results demonstrated a statistically significant inverse correlation (p = 0.007) between PBOC levels in aquifer sediments and chloroethene concentrations for selected monitoring wells in which chloroethene exposure was the highest. Results from laboratory exposure assays also demonstrated that sediment samples exhibited a reduction in PBOC levels of 35% and 73%, respectively, after a 72-h exposure period to PCE (20; 000 mu g/L). These results support the notion that PBOC depletion in sediments may be expected in chloroethene-contaminated aquifers, which has potential implications for the long-term sustainability of monitored natural attenuation. DOI: 10.1061/(ASCE)EE.1943-7870.0000597. (C) 2013 American Society of Civil Engineers.
    Journal of Environmental Engineering 01/2013; 139(1):54-60. DOI:10.1061/(ASCE)EE.1943-7870.0000597 · 1.22 Impact Factor
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    ABSTRACT: This study evaluated the relationship between concentrations of operationally defined potentially bioavailable organic ‐carbon (PBOC) and hydrolyzable amino acids (HAAs) in sediments collected from a diverse range of chloroethene‐‐contaminated sites. Concentrations of PBOC and HAA were measured using aquifer sediment samples collected at six selected study sites. Average concentrations of total HAA and PBOC ranged from 1.96 ± 1.53 to 20.1 ± 25.6 mg/kg and 4.72 ± 0.72 to 443 ± 65.4 mg/kg, respectively. Results demonstrated a statistically significant positive relationship between concentrations of PBOC and total HAA present in the aquifer sediment (p Document Type: Research Article DOI: Publication date: November 1, 2012 $(document).ready(function() { var shortdescription = $(".originaldescription").text().replace(/\\&/g, '&').replace(/\\, '<').replace(/\\>/g, '>').replace(/\\t/g, ' ').replace(/\\n/g, ''); if (shortdescription.length > 350){ shortdescription = "" + shortdescription.substring(0,250) + "... more"; } $(".descriptionitem").prepend(shortdescription); $(".shortdescription a").click(function() { $(".shortdescription").hide(); $(".originaldescription").slideDown(); return false; }); }); Related content In this: publication By this: publisher In this Subject: Geology By this author: Thomas, Lashun K. ; Widdowson, Mark A. ; Novak, John T. ; Chapelle, Francis H. ; Benner, Ronald ; Kaiser, Karl GA_googleFillSlot("Horizontal_banner_bottom");
    Ground Water Monitoring and Remediation 11/2012; 32(4). DOI:10.1111/j.1745-6592.2012.01406.x · 1.25 Impact Factor
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    ABSTRACT: Recent studies have demonstrated that wastewater treatment plants (WWTPs) significantly alter the magnitude and distribution of antibiotic resistance genes (ARGs) in receiving environments, indicating that wastewater treatment represents an important node for limiting ARG dissemination. This study examined the potential for membrane treatment of microconstituent ARGs and the effect of native wastewater colloids on the extent of their removal. Plasmids containing vanA (vancomycin) and bla(TEM) (β-lactam) ARGs were spiked into three representative WWTP effluents versus a control buffer and tracked by quantitative polymerase chain reaction through a cascade of microfiltration and ultrafiltration steps ranging from 0.45 μm to 1 kDa. Significant removal of ARGs was achieved by membranes of 100 kDa and smaller, and presence of wastewater colloids resulted in enhanced removal by 10 kDa and 1 kDa membranes. ARG removal was observed to correlate significantly with the corresponding protein, polysaccharide, and total organic carbon colloidal fractions. Alumina membranes removed ARGs to a greater extent than polyvinylidene fluoride membranes of the same pore size (0.1 μm), but only in the presence of wastewater material. Control studies confirmed that membrane treatment was the primary mechanism of ARG removal, versus other potential sources of loss. This study suggests that advanced membrane treatment technology is promising for managing public health risks of ARGs in wastewater effluents and that removal may even be enhanced by colloids in real-world wastewaters.
    Water Research 10/2012; 47(1). DOI:10.1016/j.watres.2012.09.044 · 5.32 Impact Factor
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    ABSTRACT: Advanced anaerobic digestion processes aimed at improving the methanization of sewage sludge may be potentially impaired by the production of inhibitory compounds (e.g. free ammonia). The result of methanogenic inhibition is relatively high effluent concentrations of acetic acid and other soluble organics, as well as reduced methane yields. An extreme example of such an advanced process is the thermal hydrolytic pretreatment of sludge prior to high solids digestion (THD). Compared to a conventional mesophilic anaerobic digestion process (MAD), THD operates in a state of constant inhibition driven by high free ammonia concentrations, and elevated pH values. As such, previous investigations of the kinetics of methanogenesis from acetic acid under uninhibited conditions do not necessarily apply well to the modeling of extreme processes such as THD. By conducting batch ammonia toxicity assays using biomass from THD and MAD reactors, we compared the response of these communities over a broad range of ammonia inhibition. For both processes, increased inhibitor concentrations resulted in a reduction of biomass growth rate (r(max) = μ(max)∙X) and a resulting decrease in the substrate half saturation coefficient (K(S)). These two parameters exhibited a high degree of correlation, suggesting that for a constant transport limited system, the K(S) was mostly a linear function of the growth rate. After correcting for reactor pH and temperature, we found that the THD and MAD biomass were both able to perform methanogenesis from acetate at high free ammonia concentrations (equivalent to 3-5 g/L total ammonia nitrogen), albeit at less than 30% of their respective maximum rates. The reduction in methane production was slightly less pronounced for the THD biomass than for MAD, suggesting that the long term exposure to ammonia had selected for a methanogenic pathway less dependent on those organisms most sensitive to ammonia inhibition (i.e. aceticlastic methanogens).
    Water Research 09/2012; 46(19). DOI:10.1016/j.watres.2012.08.028 · 5.32 Impact Factor
  • Renzun Zhao · John T Novak · C Douglas Goldsmith
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    ABSTRACT: A cost effective and widely applied approach for landfill leachate disposal is to discharge it to a municipal wastewater treatment plant (WWTP). The recalcitrant nature of leachate organics and the impact on the downstream WWTPs were comprehensively investigated in this study. Size fractionation by ultrafiltration (UF) and microfiltration (MF) was employed in conjunction with various analyses (TOC, COD, nitrogen species and UV(254) absorbance) on raw and biologically treated landfill leachates to provide insight into biological treatability. Overall, landfill leachate organics showed bio-refractory properties. Less than half of the organic matter, measured as total organic carbon (TOC), could be removed in the biological processes examined. Size distribution data showed that the <1 thousand Daltons (kDa) fraction is dominant in most untreated and treated landfill leachates, indicating difficulties for membrane treatment. Also, most removal occurred for the <1 kDa fraction in the biological processes, while the intermediate size fractions increased slightly. This may be caused by bio-flocculation and/or partial degradation of larger molecular weight fractions. Organic nitrogen was investigated in this study as one of the first explorations for landfill leachates. Organic nitrogen in landfill leachates was more bio-refractory than other organic matter. UV quenching by landfill leachates was also investigated since it interferes with the UV disinfection at WWTPs. The combination of activated carbon and activated sludge (PACT) showed some effectiveness for reducing UV quenching, indicating that carbon adsorption is a potential method for removal of UV quenching substances. Fourier transform Infrared (FT/IR) data showed that aromatic groups are responsible for the UV quenching phenomenon.
    Water Research 04/2012; 46(12):3837-48. DOI:10.1016/j.watres.2012.04.022 · 5.32 Impact Factor
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    ABSTRACT: The presence of micropollutants can be a concern for land application of biosolids. Of particular interest are nonylphenol diethoxylate (NP(2)EO), nonylphenol monoethoxylate (NP(1)EO), and nonylphenol (NP), collectively referred to as NPE, which accumulate in anaerobically digested biosolids and are subject to regulation based on the environmental risks associated with them. Because biosolids are a valuable nutrient resource, it is essential that we understand how various treatment processes impact the fate of NPE in biosolids. Thermal hydrolysis (TH) coupled with mesophilic anaerobic digestion (MAD) is an advanced digestion process that destroys pathogens in biosolids and increases methane yields and volatile solids destruction. We investigated the impact of thermal hydrolysis pretreatment on the subsequent biodegradation of NPE in digested biosolids. Biosolids were treated with TH, anaerobic digestion, and aerobic digestion in laboratory-scale reactors, and NPE were analyzed in the influent and effluent of the digesters. NP(2)EO and NP(1)EO have been observed to degrade to the more estrogenic NP under anaerobic conditions; therefore, changes in the ratio of NP:NPE were of interest. The increase in NP:NPE following MAD was 56%; the average increase of this ratio in four sets of TH-MAD samples, however, was only 24.6 ± 3.1%. In addition, TH experiments performed in pure water verified that, during TH, the high temperature and pressure alone did not directly destroy NPE; TH experiments with NP added to sludge also showed that NP was not destroyed by the high temperature and pressure of TH when in a more complex sludge matrix. The post-aerobic digestion phases removed NPE, regardless of whether TH pretreatment occurred. This research indicates that changes in biosolids processing can have impacts beyond just gas production and solids destruction.
    Water Research 03/2012; 46(9):2937-46. DOI:10.1016/j.watres.2012.03.015 · 5.32 Impact Factor
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    ABSTRACT: Advanced anaerobic digestion processes that apply high temperatures or high solids loading rates create distinct chemical environments that are not routinely encountered by conventional digestion communities. Among the most important chemical changes that occur in high temperature and high solids digestion processes relative to conventional digestion are unfavorable shifts in the unionized fractions of both acetic acid and ammonia, the latter of which imparts inhibition on the acetic acid degrading methanogenic community. The objective of this paper is to identify and, where possible, to quantify the impact of digestion temperature and solids loading on the performance of advanced anaerobic digestion in the context of these shifts in ionized/unionized chemical species.Two case studies are discussed in order to reveal operational considerations to control ammonia sensitivity and to potentially improve digestion performance in these advanced digestion systems. In the first study, the operating temperature of a full-scale digestion process is reduced by several degrees Celsius, resulting in a rapid increase in biogas production during process start-up. In a second case study, bench scale digestion investigations of a moderately and a highly loaded digestion process are compared. The stoichiometric release of ammonia and alkalinity in the highly loaded process results in a calculated free ammonia concentration in excess of 8 times that of the moderately loaded process, resulting in an apparent inhibition of aceticlastic methanogenesis and a high residual concentration of volatile acids. The impacts observed in these case studies result in several suggested strategies to control ammonia sensitivity in anaerobic digestion processes where it is expected to occur.
    01/2012; 2012(2):1049-1059. DOI:10.2175/193864712811693335
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    01/2012; 2012(2):1221-1234. DOI:10.2175/193864712811693579

Publication Stats

3k Citations
259.88 Total Impact Points


  • 1989–2015
    • Virginia Polytechnic Institute and State University
      • • Department of Civil and Environmental Engineering
      • • Department of Crop and Soil Environmental Sciences
      Блэксбург, Virginia, United States
  • 2010
    • Sun Yat-Sen University
      • School of Environmental Science and Engineering
      Guangzhou, Guangdong Sheng, China
  • 2006
    • Bucknell University
      Lewisburg, Pennsylvania, United States
  • 1999
    • Gannon University
      Erie, Pennsylvania, United States