Blacksburg, VA, United States
Blacksburg, VA, United States

Time filter

Source Type

Chanton J.,Florida State University | Langford C.,Florida State University | Hater G.,Waste Management | Green R.,Waste Management | And 2 more authors.
Environmental Science and Technology | Year: 2011

Methane oxidation in landfill covers was determined by stable isotope analyses over 37 seasonal sampling events at 20 landfills with intermediate covers over four years. Values were calculated two ways: by assuming no isotopic fractionation during gas transport, which produces a conservative or minimum estimate, and by assuming limited isotopic fractionation with gas transport producing a higher estimate. Thus bracketed, the best assessment of mean oxidation within the soil covers from chamber captured emitted CH4 was 37.5 ± 3.5%. The fraction of CH4 oxidized refers to the fraction of CH4 delivered to the base of the cover that was oxidized to CO2 and partitioned to microbial biomass instead of being emitted to the atmosphere as CH4 expressed as a percentage. Air samples were also collected at the surface of the landfill, and represent CH4 from soil, from leaking infrastructure, and from cover defects. A similar assessment of this data set yields 36.1 ± 7.2% oxidation. Landfills in five climate types were investigated. The fraction oxidized in arid sites was significantly greater than oxidation in mediterranean sites, or cool and warm continental sites. Sub tropical sites had significantly lower CH4 oxidation than the other types of sites. This relationship may be explained by the observed inverse relationship between cover loading and fractional CH4 oxidation. © 2010 American Chemical Society.

Chanton J.,Florida State University | Langford C.,Florida State University | Spokas K.,U.S. Department of Agriculture | Hater G.,Waste Management Incorporated | And 3 more authors.
Waste Management | Year: 2011

The objective of this study was to determine the role of CH4 loading to a landfill cover in the control of CH4 oxidation rate (gCH4m-2d-1) and CH4 oxidation efficiency (% CH4 oxidation) in a field setting. Specifically, we wanted to assess how much CH4 a cover soil could handle. To achieve this objective we conducted synoptic measurements of landfill CH4 emission and CH4 oxidation in a single season at two Southeastern USA landfills. We hypothesized that percent oxidation would be greatest at sites of low CH4 emission and would decrease as CH4 emission rates increased. The trends in the experimental results were then compared to the predictions of two differing numerical models designed to simulate gas transport in landfill covers, one by modeling transport by diffusion only and the second allowing both advection and diffusion. In both field measurements and in modeling, we found that percent oxidation is a decreasing exponential function of the total CH4 flux rate (CH4 loading) into the cover. When CH4 is supplied, a cover's rate of CH4 uptake (gCH4m-2d-2) is linear to a point, after which the system becomes saturated. Both field data and modeling results indicate that percent oxidation should not be considered as a constant value. Percent oxidation is a changing quantity and is a function of cover type, climatic conditions and CH4 loading to the bottom of the cover. The data indicate that an effective way to increase the % oxidation of a landfill cover is to limit the amount of CH4 delivered to it. © 2010 Elsevier Ltd.

PubMed | e Cygnus Environmental Group, b Waste Management Inc., Florida State University, North Carolina State University and Alternative Natural Technologies Inc.
Type: Journal Article | Journal: Journal of the Air & Waste Management Association (1995) | Year: 2017

In the method termed Other Test Method-10, the U.S. Environmental Protection Agency has proposed a method to quantify emissions from nonpoint sources by the use of vertical radial plume mapping (VRPM) technique. The surface area of the emitting source and the degree to which the different zones of the emitting source are contributing to the VRPM computed emissions are often unknown. The objective of this study was to investigate and present an approach to quantify the unknown emitting surface area that is contributing to VRPM measured emissions. Currently a preexisting model known as the multiple linear regression model, which is described in Thoma et al. (2009 ), is used for quantifying the unknown surface area. The method investigated and presented in this paper utilized tracer tests to collect data and develop a model much like that described in Thoma et al. (2009 ). However, unlike the study used for development of the multiple linear regression model, this study is considered a very limited study due to the low number of pollutant releases performed (seven total releases). It was found through this limited study that the location of an emitting source impacts VRPM computed emissions exponentially, rather than linearly (i.e., the impact that an emitting source has on VRPM measurements decreases exponentially with increasing distances between the emitting source and the VRPM plane). The data from the field tracer tests were used to suggest a multiple exponential regression model. The findings of this study, however, are based on a very small number of tracer tests. More tracer tests performed during all types of climatic conditions, terrain conditions, and different emissions geometries are still needed to better understand the variation of capture efficiency with emitting source location. This study provides a step toward such an objective. [Box: see text].

Goldsmith Jr. C.D.,Alternative Natural Technologies Inc. | Chanton J.,Florida State University | Abichou T.,Florida State University | Swan N.,Cygnus Environmental Group | And 2 more authors.
Journal of the Air and Waste Management Association | Year: 2012

Landfill fugitive methane emissions were quantified as a function of climate type and cover type at 20 landfills using U.S. Environmental Protection Agency (EPA) Other Test Method (OTM)-10 vertical radial plume mapping (VRPM) with tunable diode lasers (TDLs). The VRPM data were initially collected as g CH4/sec emission rates and subsequently converted to g CH4/m2/day rates using two recently published approaches. The first was based upon field tracer releases of methane or acetylene and multiple linear regression analysis (MLRM). The second was a virtual computer model that was based upon the Industrial Source Complex (ISC3) and Pasquill plume stability class models (PSCMs). Calculated emission results in g CH4/m2/day for each measured VRPM with the two approaches agreed well (r2 = 0.93). The VRPM data were obtained from the working face, temporary soil, intermediate soil, and final soil or synthetic covers. The data show that methane emissions to the atmosphere are a function of climate and cover type. Humid subtropical climates exhibited the highest emissions for all cover types at 207, 127, 102, and 32 g CH4/m2/day, for working face (no cover), temporary, intermediate, and final cover, respectively. Humid continental warm summers showed 67, 51, and 27 g CH4/m2/day for temporary, intermediate, and final covers. Humid continental cool summers were 135, 40, and 26 g CH4/m2/day for the working face, intermediate, and final covers. Mediterranean climates were examined for intermediate and final covers only and found to be 11 and 6 g CH4/m2/day, respectively, whereas semiarid climates showed 85, 11, 3.7, and 2.7 g CH4/m2/day for working face, temporary, intermediate, and final covers. A closed, synthetically capped landfill covered with soil and vegetation with a gas collection system in a humid continental warm summer climate gave mostly background methane readings and average emission rates of only 0.09 g CH4/m2/day flux when measurable. Implications: The OTM-10 method is being proposed by EPA to quantify surface methane emissions from landfill covers. This study of 20 landfills across the United States was done to determine the efficacy of using OTM-10 for this purpose. Two recently published models were used to evaluate the methane flux results found with VRPM optical remote sensing. The results should provide a sense of the practicality of the method, its limitations at landfills, and the impact of climate upon the cover's methane flux. Measured field data may assist landfill owners in refining previously modeled methane emission factor default values. © 2012 Copyright 2012 A&WMA.

Zhao R.,Kruger Inc | Gupta A.,Virginia Polytechnic Institute and State University | Novak J.T.,Virginia Polytechnic Institute and State University | Goldsmith C.D.,Alternative Natural Technologies Inc. | Driskill N.,Virginia Polytechnic Institute and State University
Journal of Hazardous Materials | Year: 2013

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. © 2013 Elsevier B.V.

Gupta A.,Virginia Polytechnic Institute and State University | Zhao R.,Virginia Polytechnic Institute and State University | Zhao R.,Harbin Institute of Technology | Novak J.T.,Virginia Polytechnic Institute and State University | Douglas Goldsmith C.,Alternative Natural Technologies Inc.
Chemosphere | Year: 2014

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. © 2014 Elsevier Ltd.

Driskill N.M.,Virginia Polytechnic Institute and State University | Novak J.T.,Virginia Polytechnic Institute and State University | Goldsmith C.D.,Alternative Natural Technologies Inc.
Journal of Environmental Engineering (United States) | Year: 2014

Landfill leachates are often discharged through sewers or by trucks to publicly owned treatment works (POTWs) after on-site biological treatment. This discharge of landfill leachate is widely accepted because of its cost-effectiveness and reliability, but potential impacts of this practice include additional nutrient loading and interference with ultraviolet (UV) disinfection during subsequent biological treatment. Leachate was fractionated into humic acid (HA), fulvic acid (FA), and hydrophilic (Hpi) fractions based on chemical composition and solubility to determine the hydrophobicity distribution. The analysis showed that the specific UV254 absorbance (SUVA254) of the humic substances (HA and FA) was significantly higher than the Hpi fraction. The UV quenching materials were found to be resistant to biological treatment for the majority of leachates studied. Removal of humic substances was associated with decreased UV quenching and the aromatic content of landfill leachates after biological treatment. The size distribution of the hydrophilic fraction suggests that the majority of organic nitrogen in landfill leachate is associated with the low-molecular-weight (<1∈∈kDa) hydrophilic fraction. © 2014 American Society of Civil Engineers.

Zhao R.,Virginia Polytechnic Institute and State University | Novak J.T.,Virginia Polytechnic Institute and State University | Goldsmith C.D.,Alternative Natural Technologies Inc.
Water Research | Year: 2012

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. © 2012 Elsevier Ltd.

Zhao R.,Virginia Polytechnic Institute and State University | Novak J.T.,Virginia Polytechnic Institute and State University | Douglas Goldsmith C.,Alternative Natural Technologies Inc.
Waste Management | Year: 2013

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. © 2013 Elsevier Ltd.

PubMed | Alternative Natural Technologies Inc. and Virginia Polytechnic Institute and State University
Type: Journal Article | Journal: Waste management & research : the journal of the International Solid Wastes and Public Cleansing Association, ISWA | Year: 2014

This study investigates the effect of landfill age on landfill leachate characteristics; two aspects are focused here. One is ultraviolet absorbance at 254 nm (UV(254)) property, as the discharge of landfill leachates to publically owned treatment works can cause interference with UV(254) 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 UV(254)-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 UV(254)-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.

Loading Alternative Natural Technologies Inc. collaborators
Loading Alternative Natural Technologies Inc. collaborators