Cincinnati, OH, United States
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Pinto P.X.,Pegasus Technical Services Inc. | Al-Abed S.R.,U.S. Environmental Protection Agency
Applied Geochemistry | Year: 2017

A series of leaching and partitioning tests (Toxicity Characteristic Leaching Procedure (TCLP), Synthetic Precipitation Leaching Procedure (SPLP), Controlled Acidity Leaching Protocol (CALP), Acid Neutralization Capacity (ANC), and sequential extraction) were applied to three different soils to study the potential mobility of metals into groundwater. Two of these soils were lead (Pb)-contaminated soils (Hotspot 1 and Hotspot 2) collected from an urban site associated with lead smelting and other industrial operations. The third sample (Stockpile) was soil affected by previous contamination in the area, removed from residential properties, stockpiled, and selected to be used as fill material in the studied site. The TCLP and CALP showed that Pb could be released from both hotspots, but were not released in the acidic rainfall extraction fluid of the SPLP. The sequential extraction showed that Pb in the hotspot soils was associated with the carbonate fraction, while As was associated with the Fe and Mn oxides. The stockpile released traces of Pb or As in the TCLP and CALP, but the ANC only released Pb under acidic conditions and the SPLP did not release Pb or As. Overall, the projected repository with Stockpile would not pose imminent danger to groundwater because, under the expected environmental conditions, Pb and As tend to remain in the solid phase. © 2017.

Lytle D.A.,U.S. Environmental Protection Agency | Nadagouda M.N.,Pegasus Technical Services Inc.
Corrosion Science | Year: 2010

Copper pitting is a complicated corrosion process for which exact causes and solutions are often uncertain. This paper presents the findings of a comprehensive investigation of a cold water copper pitting corrosion problem in a drinking water distribution system, including a refined process for preparing exhumed copper pipes for solids analysis. The investigation produced detailed structural, morphological and elemental details of copper pitting that strongly corroborated previous observations and theoretical models, and revealed new findings. For example, cross-sections revealed three components: the cap, characterized by two basic copper sulfate minerals; the cuprite membrane; and the pit containing cuprite crystals, and chloride. © 2010 Elsevier Ltd.

Virkutyte J.,Pegasus Technical Services Inc. | Varma R.S.,U.S. Environmental Protection Agency
RSC Advances | Year: 2012

An excellent visible light activated Ag and garlic loaded TiO 2 nanocatalyst was prepared by using AgNO 3 and garlic (Allium sativum) as the Ag + and sulfur sources, respectively. The catalyst resisted the change from anatase to rutile phase even at high (700 °C) calcination temperature. The photocatalytic efficiency of as-prepared nanocatalysts was evaluated by degrading (100 ppm) azodye, methyl orange (MO), and dichloro phenol (DCP) under visible light irradiation for 3 to 4 h from an incandescent light bulb (300 W). The process followed first order reaction kinetics with reaction rates ranging from 9.5 × 10 -4 to 19.4 × 10 -3 min -1. The dye was decomposed in 3 h and more than 70% DCP degraded in 4 h in the presence of Ag and garlic loaded-TiO 2 calcined at 700 °C. Demineralization of the solution was in the range 40 to 90%. A complete elimination of Vibrio fischeri was accomplished with 1 mg L -1 of nanocatalyst regardless the calcination temperature. The catalyst was used for up to 5 consecutive runs without the significant loss in the photocatalytic activity and could be regenerated by adopting a simple procedure of washing with water and acetone as well as drying at 200 °C for 2 h. © 2012 The Royal Society of Chemistry.

Virkutyte J.,Pegasus Technical Services Inc. | Varma R.S.,U.S. Environmental Protection Agency
RSC Advances | Year: 2012

To utilize visible light, Ag loaded and C, N-doped nano-TiO 2 was prepared using a "one pot" synthesis utilizing mild reaction conditions and benign precursors. The synthesis was optimized using appropriate experiment design that took the silver content and calcination temperature into account. The optimized nanocatalyst was characterized by XRD, BET, TEM, TGA, XPS as well as UV-DRS. Nanocatalysts were predominantly anatase as confirmed by XRD, thermally stable up to 1100 °C, as revealed by TGA studies and exhibited absorption in the visible light region as verified by UV-DRS analysis. Moreover, XPS results proved that Ag was dispersed on the surface of the TiO 2 nanoparticles and nitrogen, as well as carbon from guanidine nitrate was interlaced into the matrix of TiO 2. Co-doping of TiO 2 suppressed charge recombination and improved the visible light photo-activity up to the complete degradation of dichlorophenol (DCP) in 4 h of the reaction. Degradation followed first order reaction kinetics with k app ranging from 1.1 to as high as 15.1 × 10 -3 min -1 depending on the silver content and calcination temperature. Demineralization of the solution in terms of TOC was up to 92%. A complete elimination of Vibrio fischeri was accomplished with 1 mg L -1 of the nanocatalyst regardless of the Ag content. © 2012 The Royal Society of Chemistry.

Revetta R.P.,U.S. Environmental Protection Agency | Pemberton A.,Pegasus Technical Services Inc. | Lamendella R.,University of Cincinnati | Iker B.,U.S. Environmental Protection Agency | Santo Domingo J.W.,U.S. Environmental Protection Agency
Water Research | Year: 2010

Intracellular RNA is rapidly degraded in stressed cells and is more unstable outside of the cell than DNA. As a result, RNA-based methods have been suggested to study the active microbial fraction in environmental matrices. The aim of this study was to identify bacterial populations in drinking water by analyzing 16S rRNA-based clone libraries. Hollow-fiber ultrafiltration was used to concentrate bacterial communities from 40 l of tap water collected at 12 different times during three different summer months from a single point-of-use. Total RNA was extracted from the microbial concentrates and used to develop 16S rRNA-based clone libraries. Phylogenetic analyses of 1231 partial 16S rRNA gene sequences showed that difficult-to-classify bacterial sequences were the most predominant clones, representing 57.6% of the sequences analyzed. Within these unclassified clades, most sequences were closely related to sequences retrieved from previous DNA- and RNA-based drinking water studies. Other bacterial groups represented in this study included Proteobacteria, cyanobacteria, Actinobacteria, Bacteroidetes, and Planctomycetes. Overall, the results suggest that these bacterial groups are amongst potentially active bacteria in drinking water. Diversity analyses of clones generated show that while overall diversity is similar amongst the different months, membership changes with respect to time. The results from this study further improve our understanding of the molecular diversity and bacterial population dynamics of drinking water microbial communities. Moreover, these results provide the sequence foundation for the development of molecular assays that target active drinking water bacteria.

Venosa A.D.,U.S. Environmental Protection Agency | Holder E.L.,Pegasus Technical Services Inc.
Marine Pollution Bulletin | Year: 2013

We recently conducted a laboratory study to measure the dispersion effectiveness of eight dispersants currently listed on the National Contingency Plan Product Schedule. Results are useful in determining how many commercial dispersant products would have been effective for use on South Louisiana crude oil in the Deepwater Horizon oil spill. The test used was a modification of the Baffled Flask Test (BFT), which is being proposed to replace the current Swirling Flask Test (SFT). The modifications of the BFT in this study included use of one oil rather than two, increasing replication from 4 runs to 6, and testing at two temperatures, 5 °C and 25 °C. Results indicated that temperature was not as critical a variable as the literature suggested, likely because of the low viscosity and light weight of the SLC. Of the eight dispersants tested, only three gave satisfactory results in the laboratory flasks at both temperatures. © 2012.

Virkutyte J.,U.S. Environmental Protection Agency | Virkutyte J.,Pegasus Technical Services Inc. | Varma R.S.,U.S. Environmental Protection Agency
Chemical Science | Year: 2011

Current breakthroughs in green nanotechnology are capable of transformingmany of the existing processes and products that enhance environmental quality, reduce pollution, and conserve natural and nonrenewable resources. Successful use of metal nanoparticles and nanocomposites in various catalytic applications, electronics, biology and biomedical applications, material science, physics, environmental remediation and interdisciplinary fields as well as their toxicity essentially depends on the structural features such as size, shape, composition and the surface chemistry of nanomaterials. Moreover, to prolong the life span of metal nanoparticles and avoid undesired effects such as aggregation in aqueous solutions and organic solvents, toprevent contamination of the environment aswell as to reuseand recyclenanoparticles, it is vital to select stabilizing agents and functionalization pathways that are environmentally friendly, non toxic and easy to implement. In recent years, stabilization and surface functionalization of metal nanoparticles became 'greener' to the extent that biocompatible stabilizing agents, e.g. biodegradable polymers and enzymes among others were introduced. These agents were able to produce a great variety of extremely stable spherical-, rod- or flower-shaped metal nanoparticles that opened up vast opportunities for their utilization and potential mass production. This review summarizes the state-of-the-art in the use of biocompatible and biodegradable homo- and copolymers as well as enzymes for the production of stable, environmentally benign, selective and active metal nanoparticles for desired applications. © The Royal Society of Chemistry 2011.

Kanel S.R.,Pegasus Technical Services Inc. | Al-Abed S.R.,U.S. Environmental Protection Agency
Journal of Nanoparticle Research | Year: 2011

Widespread use of nanoscale zinc oxide (nZnO) in various fields causes subsurface environment contamination. Even though the transport of dissolved zinc ions in subsurface environments such as soils and sediments has been widely studied, the transport mechanism of nZnO in such environments is poorly understood. In addition, nZnO is often combined with stabilizers or dispersing agents to prevent its aggregation in products. The purpose of this study is to determine the influence of pH on the transport properties of pristine nZnO and carboxymethyl cellulose (CMC) stabilized nZnO (CMC-nZnO) suspensions in silica sand packed column under saturated flow conditions. Transport data were collected at different pHs (pHs: 3, 7, 9, and 11) under 1 mL/min flow rate conditions in a 1.1 cm diameter column. It is found that the transport trends of pristine nZnO and CMC-nZnO were different. For pristine nZnO, mobility of total Zn reached a minimum around its point of zero charge (pH 8.9). Whereas in the case of CMC-nZnO, the mobility of total Zn decreased as the pH of the solution pH increased from 3 to 11. ZnO and Zn ion mixture were separated using diafiltration membrane. It showed that most of the nZnO and CMC-nZnO exists as Zn ion at pH 3 before and after eluting from the sand packed column whereas at pH 11, they exist as particles. This study shows the strong influence of pH and stabilizing agents on nZnO transport. These factors should be considered during subsurface transport of nZnO. © Springer Science+Business Media B.V. 2011.

Virkutyte J.,Pegasus Technical Services Inc. | Jegatheesan V.,Deakin University | Varma R.S.,U.S. Environmental Protection Agency
Bioresource Technology | Year: 2012

Hybrid TiO 2/microcrystalline cellulose (MC) nanophotocatalyst was prepared in situ by a facile and simple synthesis utilizing benign precursors such as MC and TiCl 4. The as-prepared nanocomposite was characterized by XRD, XPS, BET surface area analyzer, UV-vis DRS and TGA. Surface morphology was assessed by the means of SEM and HR-TEM. Statistics-based factorial design (FD) was adopted to investigate the effect of precursors concentrations and therefore to optimize the nanocomposite synthesis through catalytic adsorption of methylene blue (MB) from aqueous solutions. The results indicated that TiO 2/MC nanocomposites were photocatalytically active in diminishing 40-90% of MB in 4h. © 2011 Elsevier Ltd.

Pegasus Technical Services Inc. and US Government | Date: 2015-05-13

A process for treatment of municipal wastewater plant sludge to the criteria of Class A biosolids. The process uses hydrogen peroxide and thermo-oxidation to reduce volatile suspended solids to meet the criteria. On a batch basis, waste activated sludge is introduced into a reactor; the concentration of the waste activated sludge is adjusted to about 1.5% total suspended solids with secondary effluent, if necessary; the reactor is mixed; the reactor is pre-heated to an operating temperature in a range of about 65 C. to about 90 C.; subsequently, a 50% solution of laboratory grade hydrogen peroxide is introduced into the bottom of the reactor; and the contents are heated for at least 4 hours.

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