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Electric vehicles, which are primarily powered by lithium-ion batteries, have gained much attention as the future of transportation for their environmental and economic benefits. However, the current economy of lithium-ion battery management is quite linear. A circular economy with reusing and end-of-life recycling of lithium-ion batteries, would reduce the social and environmental costs associated with the mining of metals, decelerate the depletion of natural resources, and prevent the improper management that often accompanies disposal. This research suggests improvements to the end-of-life management of lithium-ion batteries in the US, considering current and emerging recycling technologies, current collection and transportation infrastructure, current reuse applications, and an analysis of the current regulatory policies in place. Along with providing a comprehensive overview of these topics, this research compiles and provides a set of actionable End-of-Life (EOL) management recommendations for the US on policy, infrastructure, and technology.

Shale gas has become one of the important contributors to the global energy supply. The declining pattern of the gas production rate with time from an unconventional gas reservoir is due to the depletion of shale gas stored in the nanovoids of the shale formation. However, there are only limited ways to predict the variation of the gas production rate with time from an unconventional gas reservoir. This is due to the multiple transport mechanisms of gas in nano-scale pores and changes in shale gas permeability with pressures in nano-scale pores, which is impacted by the pore structure of the shale. In this study, the permeability-pressure (K-p) relationship for different shales (Eagle Ford, Haynesville, Longmaxi and Opalinus) were determined using an equivalent anisotropic pore network model (PNM). This PNM has REV-scale shale gas flow in randomly generated nanovoids and their connection in the shale matrix, and the multiphase flow of shale gas including viscous flow, slip flow and Knudsen diffusion. These predicted K-p correlations were then used in a finite element model (FEM) to predict the variation of the gas production rate with time (flux-time curves) at the macroscale. The simulation results show that the flux-time curves can be simplified to two linear segments in logarithmic coordinates, which are influenced by the fracture length and initial gas pressure. The predicted results using the PNM-FEM were validated by comparing them with the reported field test data. The method described in this study can be used to upscale the gas transport process from micro- to macroscale, which can provide a predictive tool for the gas production in shales.

Per- and polyfluoroalkyl substances (PFASs) are a family of highly toxic emerging contaminants that have caught the attention of both the public and private sectors due to their adverse health impacts on society. The scientific community has been laboriously working on two fronts: (1) adapting already existing and effective technologies in destroying organic contaminants for PFAS remediation and (2) developing new technologies to remediate PFAS. A common characteristic in both areas is the separation/removal of PFASs from other contaminants or media, followed by destruction. The widely adopted separation technologies can remove PFASs from being in contact with humans; however, they remain in the environment and continue to pose health risks. On the other hand, the destructive technologies discussed here can effectively destroy PFAS compounds and fully address society’s urgent need to remediate this harmful family of chemical compounds. This review reports and compare widely accepted as well as emerging PFAS destruction technologies. Some of the technologies presented in this review are still under development at the lab scale, while others have already been tested in the field.

Microplastics (MP) are plastic particles less than 5 mm in size. There are two categories of MP: primary and secondary. Primary or microscopic-sized MP are intentionally produced material. Fragmentation of large plastic debris through physical, chemical, and oxidative processes creates secondary MP, the most abundant type in the environment. Microplastic pollution has become a global environmental problem due to their abundance, poor biodegradability, toxicological properties, and negative impact on aquatic and terrestrial organisms including humans. Plastic debris enters the aquatic environment via direct dumping or uncontrolled land-based sources. While plastic debris slowly degrades into MP, wastewater and stormwater outlets discharge a large amount of MP directly into water bodies. Additionally, stormwater carries MP from sources such as tire wear, artificial turf, fertilizers, and land-applied biosolids. To protect the environment and human health, the entry of MP into the environment must be reduced or eliminated. Source control is one of the best methods available. The existing and growing abundance of MP in the environment requires the use of multiple strategies to combat pollution. These strategies include reducing the usage, public outreach to eliminate littering, reevaluation and use of new wastewater treatment and sludge disposal methods, regulations on macro and MP sources, and a wide implementation of appropriate stormwater management practices such as filtration, bioretention, and wetlands.

An in situ remediation method was developed based on low-frequency ultrasound, and ozone nanobubbles to remediate heavily contaminated Passaic River sediments. This study evaluated the performance ...

One attractive aspect of CO2 sequestration in shale formations is the preferential adsorption of CO2 compared to methane, which may provide enhanced methane production as well as sequestration of carbon dioxide. In this work, a comprehensive theoretical model of CO2 migration at the pore scale is developed to study CO2 migration properties in organic-rich shale formations. The proposed model takes into account dynamic competitive adsorption between CO2 and CH4, slip-flow effects due to the nanometer range of pore sizes, and pore-size changes due to adsorption. Because of the high pressure and temperature, the injected CO2 is in supercritical phase. Pore bodies in the shale matrix are irregular in shape, with roughness along pore wall. The structure of pore body affects the amount of surface areas and associated number of adsorption sites, and hence, a shape factor is proposed in this work to consider the irregularity of pore structure in shale matrix. The sorption of CO2 leads to an apparent retardation of the migration of CO2, which is quantified in this work. The developed pore-network model is extended to consider the impacts of different spatial distributions of the organic materials within the shale matrix.

In this paper, nonlinearity associated with intense ultrasound is studied by using the one-dimensional motion of nonlinear shock wave in an ideal fluid. In nonlinear acoustics, the wave speed of different segments of a waveform is different, which causes distortion in the waveform and can result in the formation of a shock (discontinuity). Acoustic pressure of high-intensity waves causes particles in the ideal fluid to vibrate forward and backward, and this disturbance is of relatively large magnitude due to high-intensities, which leads to nonlinearity in the waveform. In this research, this vibration of fluid due to the intense ultrasonic wave is modeled as a fluid pushed by one complete cycle of piston. In a piston cycle, as it moves forward, it causes fluid particles to compress, which may lead to the formation of a shock (discontinuity). Then as the piston retracts, a forward-moving rarefaction, a smooth fan zone of continuously changing pressure, density, and velocity is generated. When the piston stops at the end of the cycle, another shock is sent forward into the medium. The variation in wave speed over the entire waveform is calculated by solving a Riemann problem. This study examined the interaction of shocks with a rarefaction. The flow field resulting from these interactions shows that the shock waves are attenuated to a Mach wave, and the pressure distribution within the flow field shows the initial wave is dissipated. The developed theory is applied to waves generated by 20 KHz, 500 KHz, and 2 MHz transducers with 50, 150, 500, and 1500 W power levels to explore the effect of frequency and power on the generation and decay of shock waves. This work enhances the understanding of the interactions of high-intensity ultrasonic waves with fluids.

This paper discusses the feasibility of sustainable management of municipal solid waste without food waste. Many governments, states and cities are aware of the adverse impacts of food waste on the...

An experimental programme was developed to investigate the influence of three viscous–dominant contaminants on the stress–strain response of clay soils. Four degrees of contamination (by weight) – that is, C c = 2, 4, 6 and 8% – were examined. Natural and contaminated samples were prepared at their respective Proctor optimum condition and further subjected to unconfined compression tests. The dimensional analysis concept was implemented to quantify the stress–strain response. A sensitivity analysis with respect to the proposed dimensional models was also performed to examine the impact of various contamination scenarios on the strength properties. Lubrication at the particle contact level caused by the viscous nature of the contaminant agent portrayed a significant role in describing the stress–strain response. The stress–strain relationship was adversely affected by contamination. Peak strength and stiffness were inversely related to contaminant viscosity μ c and C c, with the former representing a more dominant role. An increase in μ c and/or C c, however, promoted a notable improvement in the ductility. The predictive capacity of the proposed dimensional models was examined and validated by statistical techniques. The proposed models contain a limited number of fitting parameters, which can be calibrated by minimal experimental effort and hence implemented for predictive purposes.

Nanobubbles have electrically charged interfaces; hence, the diffused double layer theory can be applied to explain the behavior of nanobubbles in different electrolytic solutions. In this research, oxygen nanobubbles were generated in NaCl solutions of different concentrations, and bubble size and ζ potentials were measured just after the generation and after 1 week. The measured data and diffused double layer theory were used to compute the surface charge density, the potential due to the surface charge, and the interaction energy between bubbles. With the increased NaCl concentration, bubble size, surface charge density, and the number of negative charges increased, while the magnitude of ζ potential/surface potential, double layer thickness, internal pressure, and the electrostatic repulsion force decreased. The same trend was observed after 1 week. The net total energy calculation for the 0.001 M NaCl solution showed that the bubble repulsion for an intermediate separation distance had a 6.99 × 10

The lower 12·875 km of the Passaic River (NJ, USA) is heavily contaminated due to industrial activities – specifically heavy metal extraction from chromium (Cr)-ore-processing plants and production of pesticides and herbicides. Conventional methods for remediating contaminated sediments have limited application due to the tidal action and urban development of the contaminated section of the Passaic River. Hence, this study proposes an in situ technology using ultrasound and ozone (O3) nanobubbles to remediate the sediments. Ultrasound is capable of desorbing heavy metals from soil, and ozone can oxidise the released heavy metals to a form that is mobile for ease of extraction. Nanobubbles are used as an effective ozone delivery method for the oxidation of heavy metals. Bench-scale tests were performed to evaluate the feasibility of the proposed technology. Ozone nanobubbles increased the solubility of ozone in water and reduced wastage. Also, due to the high ozone concentrations in water, chromium oxidation increased. A synthetic soil with a grain size distribution similar to that of actual river sediments was artificially contaminated with chromium and used in this research. Test results showed a 97·54% chromium removal efficiency, suggesting the feasibility of the proposed technology for pilot-scale studies.

There is a growing need to utilize large stockpiles of the industrial byproducts including coal gangue (CG), fly ash (FA) and red mud (RM) which can pose potential environmental problems. The CG, FA and RM contain aluminosilicates which can be precursors for the synthesis of geopolymers. This research studied the utilization of CG, FA and RM by silicate activation into geopolymers. Binary mixes of CG and RM and ternary mixes of CG, FA and RM were prepared and cured at temperatures ranging from 80 to 800 °C. The unconfined compressive strength tests were performed on the specimens to determine their mechanical strength. Nitrogen adsorption, mercury intrusion porosimetry, Fourier transform infrared spectroscopy and scanning electron microscopy were used to study the textural, structural and morphological characteristics of the end products. At lower curing temperatures, the ternary mixtures of CG, FA and RM showed higher strength gains when compared to the binary mixtures of CG and RM. The textural characteristics revealed that the reduction in pores and specific surface area do not necessarily result in higher compressive strength values. Furthermore, the cementitious gels formed at high temperatures resulted in well-bonded geopolymers with homogenous structures.

Electro-osmosis is an established method of dewatering fine soils, sediments, and sludge (SSS). The efficiency of electro-osmotic treatment is controlled by the electrical resistance of the system. Due to an increase in SSS resistance during treatment, its cost efficiency is reduced, limiting the widespread use of this technique. The aim of this paper is to discuss the main reasons for the increase in SSS resistance during treatment and then to analyze the most recent and widely spread modifications to classical electro-osmotic treatment that attempt to combat these issues and improve the efficiency of the technique. These modifications to electro-osmotic treatment are polarity reversal, an intermittent current, the injection of chemical solutions at the electrodes, and the use of geo-synthetics. The paper discusses the relevant research on the above adaptations, and the advantages and disadvantages of each are evaluated and compared using the available laboratory and field tests in the literature on electro-osmotic dewatering research. All four methods of modification are shown to provide significant improvements and can be successfully translated to the field for greater use. However, the improvements they bring about may not be sufficient to warrant their general use in geotechnical applications.

Background: A new generation of the sustainable landfill is designed to achieve sustainable Municipal Solid Waste (MSW) management. It is hybrid anaerobic/aerobic biodegradation landfill followed by landfill mining. However, there is limited information on landfill mining, especially the criteria and process for the practitioner to determine the end of the landfill biodegradation to commence landfill mining. Objective: Hence the overall objective of this research was to develop a comprehensive resource mining plan for bioreactor landfills. Method: When waste decomposition becomes slower or stopped, the landfill can be mined to recover resources and utilize the recovered space. The amount of the gas generated, landfill temperature and landfill settlement are indirect measures of landfill activity. Also, the concentration of cellulose (C), hemicelluloses (H), and lignin (L) can describe the biodegradable fractions of waste. Hence the biodegradation in landfills can be monitored by recording the change in methane production, temperature, settlement and the (C+H)/L ratio of waste. Once methane recovery is minimal, landfill reaches a maximum settlement and, ambient temperature plus the (C+H)/L value reaches a stable value of 0.25 indicating end of biodegradation. At this point landfill resources including compost material, non-recoverable waste, and recyclables such as plastics, metal and glass can be mined and recovered. Compost and recyclables can be sold at market value and the non-recovered waste with high energy content can be used as refuse-derived fuel. Once the landfill has been mined space can be reused thus eliminating the need to allocate valuable land for new landfills. Result: The landfill mining detailed in this manuscript utilizes principles from single stream type recycling facilities to ensure feasibility. The first landfill will be excavated and screened to separate the biodegraded soil and compost fraction from the recyclables. Then the screened recyclable materials are transported for further processing in a single stream type separation facility where they will be separated, bundled and sold. Conclusion: A cost calculation was performed for the resource mining of Calgary Biocell and if the mined resources are sold at market values, then the mining of Calgary Biocell would generate approximately $4M.

Solids such as soils and sediments contaminated with per- and polyfluorinated alkyl substances (PFAS) from exposure to impacted media, e.g., landfill leachate or biosolids, direct contaminated discharge, and contaminant transport from atmospheric deposition, have caused significant environmental pollution. Such solids can act as secondary sources of PFAS for groundwater and surface water contamination. There are currently no proven technologies that can degrade PFAS in soil and sediments in a cost-effective, environmentally-friendly, and energy-efficient manner. This study examines the use of coupled high and low-frequency ultrasound in desorbing and degrading PFAS in soil, thereby achieving concurrent treatment and destruction of PFAS in soil. Two common PFAS, namely perfluorooctanoic acid (PFOA) and perfluorooctane sulfonic acid (PFOS), were used to evaluate treatment performance in soils with both low and high organic matter contents. The test results showed that the ultrasound treatment could significantly reduce PFAS concentrations in artificially contaminated soil; however, no significant degradation was achieved. Ultrasound treatment did improve desorption of PFAS from solid particles, particularly from the highly absorbent organic soil; 68.8 ± 1.8% of PFOA and 45.4 ± 4.1% of PFOS were leached from the soil after ultrasound treatment compared to only 28 ± 0.2% of PFOA and 1 ± 3.1% of PFOSafter desorption in water. This work shows that sonication treatment is an effective technology for the removal of PFAS from solids, however, the presence of solids in the solid-liquid slurry can negatively impact ultrasonic cavitation, inhibiting the sonolytic degradation of desorbed PFAS.

Hydraulic fracturing is widely applied to economical gas production from shale reservoirs. Still, the gradual swelling of the clay micro/nanopores due to retained fluid from hydraulic fracturing causes a gradual reduction of gas production. Four different gas-bearing shale samples were investigated to quantify the expected shale swelling due to hydraulic fracturing. These shale samples were subject to heated deionized (DI) water at 100°C temperature and 1.2 MPa pressure in a laboratory reactor for 72 hours to simulate shale softening. The low-temperature nitrogen adsorption and density measurements were performed on the original and treated shale to determine the micro and nanopore structure change. The micro and nanopore structures changed during shale swelling, and the porosity decreased after shale treatment. The porosity decreased by 4% for clayey shale, while for well-cemented shale the porosity only decreased by 0.52%. The findings showed that the initial mineralogical composition of shale plays a significant role in the swelling of micro and nanopores and the pore structure alteration due to retained fluid from hydraulic fracturing. A pore network model was used to compare the permeability due to shale softening. The permeability results show a reduction from 3.76E-16 m2 to 2.62E-17 m2 after treatment based on the simulations.

© 2021 Institute of Rock and Soil Mechanics, Chinese Academy of Sciences Mechanical properties, such as the hardness H, Young's modulus E, creep modulus C, and fracture toughness Kc, are essential parameters in the design of hydraulic fracturing systems for prospective shale gas formations. In this study, a practical methodology is presented for obtaining these properties through microindentation experiments combined with quantitative observations of the mineralogical phases using X-ray diffraction (XRD), scanning electron microscopy (SEM) with backscattered electron (BSE) imaging, and energy-dispersive X-ray spectroscopy (EDS) analyses. We apply this method in the case of three types of Longmaxi shales with different mineralogies (i.e. carbonate-, clay-, and quartz-rich, respectively), which allows us to determine the characteristic indentation depth, hc = 8–10 μm, beyond which the mechanical response of the carbonate-rich shale is homogeneous and independent of its complex heterogeneous microstructure. Moreover, exploiting the results of a large number of indentation tests, we demonstrate that the indentation modulus M of the shale increases as a power-law of hardness H, and its creep modulus C increases linearly with H. We also compute the fracture toughness Kc from the indentation data by assuming a perfectly plastic behavior of the sample. Our results are in good agreement with independent measurements of Kc determined by microscratch tests. Finally, further tests on quartz- and clay-rich samples of the Longmaxi shale suggest further variations in the samples’ mechanical properties depending on their burial conditions and the mechanical properties of their dominant mineral phases.

Per- and polyfluoroalkyl substances (PFAS) are pollutants that have demonstrated a high level of environmental persistence and are very difficult to remediate. As the body of literature on their environmental effects has increased, so has regulatory and research scrutiny. The widespread usage of PFAS in industrial applications and consumer products, complicated by their environmental release, mobility, fate, and transport, have resulted in multiple exposure routes for humans. Furthermore, low screening levels and stringent regulatory standards that vary by state introduce considerable uncertainty and potential costs in the environmental management of PFAS. The recalcitrant nature of PFAS render their removal difficult, but existing and emerging technologies can be leveraged to destroy or sequester PFAS in a variety of environmental matrices. Additionally, new research on PFAS remediation technologies has emerged to address the efficiency, costs, and other shortcomings of existing remediation methods. Further research on the impact of field parameters such as secondary water quality effects, the presence of co-contaminants and emerging PFAS, reaction mechanisms, defluorination yields, and the decomposition products of treatment technologies is needed to fully evaluate these emerging technologies, and industry attention should focus on treatment train approaches to improve efficiency and reduce the cost of treatment.

With stable existence in liquids for over several weeks, nanobubbles have an extensive range of applications across many fields of science and engineering. For an effective and functional ...

Spurred by the advanced technologies, mainly including horizontal drilling and hydraulic fracturing, shale gas exploration has grown significantly over the past few decades. Upon exposure to the aqueous fracturing fluids in the high temperature and high pressure subsurface, the mechanical properties of shales such as elasticity, hardness, and strength usually deteriorate, a phenomenon termed “shale softening”. As a complex, multiphase, and multiscale material, shale is prone to the change in its mechanical properties upon exposure to fracture fluids. It is generally agreed that shale softening has great impact on the design and operation of shale gas exploration and the long-term gas production. This paper provides a critical review of the observed, phenomenological behavior of shale softening, and summarizes the currently recognized potential or hypothesized underlying mechanisms. The former includes: (1) reduction in fracture conductivity and hence the rate of gas production; (2) degradation of mechanical properties and reservoir fracability; (3) creep and long-term damage to the shale formations. The latter consists of clay-fluid interactions, electrical double layer (EDL) repulsion, solid mineral dissolution, short-term unloading, and long-term creep. However, to date, the dominant mechanisms controlling shale softening for a rock with known mineralogical compositions and the chemistry of fracturing fluids still remain unresolved. Our preliminary investigations suggest that the dominant mechanism depend on shale's compositions. Therefore, knowledge of the mineralogy of a shale is proposed as an essential requirement for the development of a framework for probing the mechanisms of shale softening. It is expected that such a newly proposed framework can practically facilitate the design and operation of shale gas exploration and help achieve stable gas production over an extended duration.

There are many methods to determine the specific surface area (SSA) of clay minerals. Some of these methods lack accuracy and some are time consuming. There are no methods available for the determination of in situ SSA. In this paper a new approach to predict the SSA of clays is proposed, which has been verified in the laboratory. This method is based on the electrical properties of soils. In this paper the experimental set up and the estimation of specific surface area is presented on the basis of variation of the dielectric constant and the conductivity of the clay–water system when subjected to alternating current in the frequency range of 1–100 MHz. The dielectric constant and conductivity respond differently for different soils with varying surface area corresponding to their mineralogy. When dielectric constants and conductivity were measured for sandy soils, there were no effects with the change of input frequency. The electrical method can identify clays and separate them from fine grained silts. Data are presented which shows a linear correlation between the magnitude of dielectric dispersion and SSA for various clay mixtures. The clay structure determines the value of in situ dielectric dispersion of the clay (Δeo) and hence the SSA, making this a good in situ method to estimate SSA of clays.

An integrated drainage information, analysis and management system (DIAMS) was developed and implemented for the New Jersey Department of Transportation (NJDOT). The purpose of the DIAMS is to provide a useful tool for managers to evaluate drainage infrastructure, to facilitate the determination of the present costs of preserving those infrastructures, and to make decisions regarding the optimal use of their infrastructure budgets. The impetus for DIAMS is the culvert information management system (CIMS), which is developed to manage the data for culvert pipes. DIAMS maintains and summarizes accumulated inspection data for all types of drainage infrastructure assets, including pipes, inlet/outlet structures, outfalls and manufactured treatment devices. DIAMS capabilities include identifying drainage infrastructure, maintaining inspection history, mapping locations, predicting service life based on the current condition states, and assessing present asset value. It also includes unit cost values of 72 standard items to estimate the current cost for new assets with the ability to adjust for future inflation. In addition, DIAMS contains several different repair, rehabilitation and replacement options to remedy the drainage infrastructure. DIAMS can analyze asset information and determine decisions to inspect, rehabilitate, replace or do nothing at the project and network levels by comparing costs with risks and failures. Costs may be optimized to meet annual maintenance budget allocations by prioritizing drainage infrastructure needing inspection, cleaning and repair. DIAMS functional modules include vendor data uploading, asset identification, system administration and financial analysis. Among the significant performance feature of DIAMS is its proactive nature, which affords decision makers the means of conducting a comprehensive financial analysis to determine the optimal proactive schedule for the proper maintenance actions and to prioritize them accordingly. Benefits of DIAMS include long-term savings that accrue by adopting optimized preventive maintenance strategies and facilitating compliance with Governmental Accounting Standards Board (GASB) and federal storm water regulations.

Prior video technologies such as closed-circuit television (CCTV) cameras have been used for culvert inspection. They are limited by the range of the area scanned and by the direction in wh...

Most river sediments are contaminated with organic and inorganic pollutants and cause significant environmental damage and health risks. This research is evaluated an in-situ sediment remediation method using ultrasound and ozone nanobubbles to remove organic and inorganic chemicals in contaminated sediments. Contaminated sediment is prepared by mixing synthetic fine sediment with an organic (p-terphenyl) and an inorganic chemical (chromium). The prepared contaminated sediment is treated with ultrasound and ozone nanobubbles under different operating conditions. For the samples with the maximum initial concentration of 4211 mg/kg Cr and 1875 mg/kg p-terphenyl, average removal efficiencies are 71% and 60%, respectively, with 240 min of sonication with 2-min pulses, whereas 97.5% and 91.5% removal efficiencies are obtained for the same, respectively, as a single contaminant in the sediment. For the same maximum concentrations, the highest removal of p-terphenyl is 82.7% with 127.2 J/ml high energy density, and for Cr, it is 77.1% using the highest number of the treatment cycle and ozone usage with 78.75/ml energy density. The Cr highest removal efficiency of 87.2% is recorded with the reduced initial concentration of 1227 mg/kg with the highest treatment cycles. The Cr removal efficiency depends on the availability of oxidizing agents and the number of washing cycles of sediments, whereas P-terphenyl degradation is most likely influenced by the combined effects of oxidation and ultrasound-assisted pyrolysis and combustion of organics.

The stability of nanobubbles in electrolyte solutions under different ion valence values was studied using deionized water, NaCl, Na2SO4, Na3PO4, CaCl2, and FeCl3. Nanobubbles were generated using hydrodynamic cavitation, and bubbles were tested for size and zeta potential. All the samples were stable for one week with no significant deviation in either bubble size or zeta potential values. The variation of size and zeta potential among six samples can be attributed to the solution properties and was mainly dependent on solution pH and the cation valency. The ion profiles revealed that the cation concentration at the bubble surface was higher than that of bulk, confirming that the bubbles were negatively charged for neutral and high pH values ( ≥ 4 ) under low valency cation adsorption. The high valency cations have the potential to neutralize or completely reverse the bubble charge. Anions or co-ions have minimal effect on the surface potential or the surface charge. The calculated internal pressures of bubble were unrealistically high, suggesting that the surface tension should be lower than that of water for nanobubble solutions. The interaction energy profile shows no significant energy barrier that overcomes the attractive van der Waals forces for all the solutions, except NaCl which had a 1.87 × 10−20 J barrier at a 5 nm separation distance. However, with the recorded stable bubbles, the calculation of the attractive van der Waals forces produced unrealistic values indicating that the Hamaker constant used for the calculation may not be valid at the nanobubble gas-liquid interface. This revealed that nanobubbles should contain exceptional interfacial properties that need to be carefully investigated and evaluated.

One of potential technologies applicable to chromium-contaminated soils is thermal treatment, for example, the vitrification. Literature showed the reduction of hexavalent to trivalent chromium at high temperature, thus converting highly toxic and water-soluble compound into less toxic and water-insoluble compound. At high temperature, such as that of vitrification, both iron and chromium oxides can experience stepwise reduction to potentially recyclable metallic iron and chromium under reducing environment. Hence the objective of this study is to investigate the feasibility to reduce iron oxides in chromium-contaminated soils. Using solid carbon as reducing agent, the reduction to metallic iron was observable at 1200 °C. At 1400 °C, the addition of 15 % carbon by weight is required for complete reduction. The reduction is very rapid at this temperature. The information on reduction at high temperature should prove useful in providing background information in thermal treatment and also the potential recycling of metal from contaminated soils.

The gas transport in shale matrix is of great research interest for optimised shale gas recovery. Pores and pore-throats in the gas-bearing shale are nano-scale, and hence transport of gas is governed by the slippage effect and Knudsen diffusion rather than viscous flow. Hence a proper mathematical model is needed for full understanding of shale gas transport. In this paper, a mathematical model that considers multi-flow regimes is proposed based on gas molecular kinetics theory. The flow regimes transition from slip flow to Knudsen diffusion, and can be adequately described by introducing a corrected intermolecular collision frequency. The proposed mathematical model predictions are compared with experimental data and found to match very well. Furthermore, the gas mass flux contributed by different flow regimes with the variation of Knudsen number is analysed. The numerical simulation results indicate that with the increase in Knudsen number, viscous flow becomes weakened, and the slippage flow reaches a peak and then decreases gradually. The contribution to the gas mass flux due to Knudsen diffusion starts at the early stage of transition flow, and becomes dominant at the later stage of transition flow.

The hydraulic fracturing or fracking and extraction of shale gas is vital to the continued success of the human race to provide a relatively clean energy source. However, there are several environmental issues that must be solved in order to make fracking environmentally acceptable. Once these issues are resolved, it could lead to a brighter future by allowing shale gas to act as a bridge to clean energy, while providing energy independence for the United States. To achieve these goals, there is a need to find suitable solutions to the following problems: methane gas leaks while fracking and during production, trigger of earthquakes due to fracking, and the disposal of the wastewater (largely comprised of fracking fluid) after the completion of fracking. To investigate the aforementioned environmental impacts, comprehensive research was performed using data for the Marcella formation. Although it is clear that additional research must be performed to fully deal with all the issues, the following s...

Extreme weather conditions(i.e. snow storm) in winter time have caused significant travel disruptions and increased delay and traffic accidents. Snow plowing and salt spreading are the most common counter-measures for making our roads safer for motorists. To assist highway maintenance authorities with better planning and allocation of winter maintenance resources, this study introduces an analytical model to estimate the required number of trucks for spreading operation subjective to pre-specified service time constraints considering road geometry, weather and traffic. The complexity of the research problem lies in dealing with heterogeneous road geometry of road sections, truck capacities, spreading patterns, and traffic speeds under different weather conditions and time periods of an event. The proposed model is applied to two maintenance yards with seven road sections in New Jersey (USA), which demonstrates itself fairly practical to be implemented, considering diverse operational conditions.

Electro-osmosis is an established method of consolidating soft fine-grained soils. Its efficiency is controlled by the electrical resistance of the soil-electrode system. Because of an increase in soil electrical resistance during treatment, its cost efficiency is reduced, limiting the widespread use of this technique, especially in developed nations. One of the main causes of electrical resistance is hydrolysis of water molecules around the electrodes. The acidification of the anode, in particular, reduces the negative surface charge of clay particles and, thus, the zeta potential. According to the Helmholtz-Smoluchowski model, the zeta potential is directly proportional to the electro-osmotic permeability. This article studies the use of ion exchange membranes to assess their ability to prevent flow of hydrogen ions into the soil. The test with an anion exchange membrane showed minimal change of the pH in the soil around the anode compared to a control, which is better for electro-osmotic consolidation.

The locked-wheel skid trailer (ASTM E274) is commonly used to estimate the skid resistance of pavements in the United States. However, this method is very expensive and disturbs the traffic flows during the test. Hence, a correlation was developed between skid resistance or skid number (SN40R) values obtained using skid tester and the texture data or mean profile depth (MPD), collected using a vehicle-mounted laser operating at highway speeds from nine highway test sections. This paper describes two field tests performed to validate the above-mentioned Skid Resistance versus MPD correlation and to also develop a rapid screening methodology for skid resistance of a network of pavements. In addition to the locked-wheel skid trailer and vehicle-mounted laser, several other tests such as the Dynamic Friction Test (DFT), circular texture meter (CTM) and sand patch tests were also performed. The MPD values obtained from the vehicle-mounted laser operating at highway speeds and cumulative daily traffic volumes f...

This manuscript presents a detailed discussion of the challenges faced and lessons learned during the initial phase of operation of the Calgary Biocell. The Calgary Biocell is a full-scale pilot project that has been implemented to acquire data and demonstrate the applicability of the biocell concept under severe winter conditions. The biocell concept involves operating a waste cell in three phases: first as an anaerobic bioreactor to recover biogas and produce energy, second as an aerobic bioreactor or an in-ground composter, and finally mined to recover processed waste and land for reuse. The Calgary Biocell has been in operation in its first phase, as an anaerobic bioreactor, for over the past five years. The cell was equipped with sensors to gather performance data during anaerobic and aerobic bioreactor operation. The settlement, moisture content, pressure, and temperature sensors provided early data, but failed after several months of cell operation. Regular monitoring and repairs were perfo...

Estimating truck fleet size for winter road maintenance, such as snowplowing, is a challenging task for highway maintenance agencies. To estimate the fleet size for a snowplowing operation, a mathematic model is developed considering road geometry, weather, and traffic speed, subject to service time limit. The complexity of the problem lies in the varying pavement width of road sections, different plowing patterns on the mainline and ramps, weather- and time-dependent traffic speed, and the use of mixed types of plows. With real-world data, the developed model is applied in a case study, and the model demonstrates itself to be considerably flexible in adapting to various circumstances in estimating fleet size for snowplowing operations.

An acoustic emission (AE) method was used to detect leaks and discern their location under flow conditions in a 304.8-m-long, 305-mm-diameter buried steel pipeline at the New Jersey Institute of Technology/U.S. Environmental Protection Agency (NJIT/USEPA) Buried Pipeline Test Facility in Edison, New Jersey. A 16.2 mL/s leak was successfully detected, and its discernible location was indicated to within 0.3 m, with a sensor separation of 65.5 m, and with water in the pipeline flowing at 11.4 L/s. Encouraging results were also obtained for a 1.3 mL/s leak that was discernible at a sensor separation of 21.3 m under the same flow conditions. Previous static pressure leak testing on this pipeline detected a 12.6 mL/s leak at sensor separations of up to 192.9 m, and it is expected that mitigating the effects of both externally produced and flow-induced background noise will allow for the detection of smaller leak rates under greater flow conditions. These results demonstrated that effective AE leak ...

Centrifugal model tests were performed to study the impact of the fabric of a fine-grained soil on transport of a light non-aqueous phase liquid (LNAPL). An image processing technique was developed to extract contaminant transport and fate data from the centrifugal model. Two unconsolidated sites with different moisture contents and a saturated site consolidated due to self-weight were simulated using the centrifuge. The LNAPL migrated in the vertical direction as a narrow plume and formed a free product pool above the saturated zone in unsaturated and unconsolidated soils. However, the LNAPL migrated in the horizontal direction before moving in the vertical direction as a broad plume in the consolidated site. The test results showed that the final width of the plume in the unsaturated zone of the consolidated site was nearly two times as large as that for the unconsolidated sites. In addition, the rate of leak from the underground storage tanks (USTs) on consolidated soils was substantially higher when c...

This chapter briefly discusses landfill design, construction, and operation. It presents siting considerations, regulations, and other important steps before the design stage. In recent years, the landfill design philosophy has shifted from the dry-storage concept to the bioreactor approach. In the bioreactor approach, the moisture content of the municipal solid waste (MSW) is increased by recirculating leachate to enhance biodegradation. Landfill design involves designing physical elements of the landfill and operational systems. The major design components of a landfill are sub-base, liner, leachate management system, gas management system, final cap, and stormwater management. Monitoring is an important task during landfill construction/operation and after closure. Leachate, possible leakage through the liner system, groundwater quality, landfill gas migration, and stability are among the most commonly monitored aspects.

The Road Weather Information System (RWIS) has been applied as an effective tool to collect weather and road surface temperature information and to assist operational decisions for snow and ice control activities. Current practices on siting regional RWIS stations rely on the knowledge and experiences of maintenance and operation personnel, which is subjective and inefficient. A two-stage sequential model is developed in this paper. The Stage-1 model optimizes the number and locations of RWIS stations, which intends to maximize spatial coverage with the least overlapping area, considering the variation of regional weather severity. The deployment of the optimized RWIS sites can be prioritized by the Stage-2 model, which maximizes the lifecycle profit subject to limited budget. The proposed methodology is applied to optimize a RWIS network for the State of New York.

SUMMARY Two approaches of generating pore networks of porous media are presented to capture the pore fabric. The first methodology extracted pore structure from a computer simulated packing of spheres. The modified Delaunay tessellation was used to describe the porous media, and modified Nelder–Mead method in conjunction with three pore-merging algorithms was used to generate the pore size and coordination number distributions of the randomly packed spheres. The Biconical Abscissa Asymmetric CONcentric bond was used to describe the connection between two adjacent voids. This algorithm was validated by predicting pore structure of a cubic array of spheres of equal radius with known pore sizes, throat sizes and coordination number distributions. The predicted distributions of pore structure agreed well with the measured. Then, the algorithm was used to predict pore structure and permeability of randomly packed spherical particles, and predicted permeability values were compared with published experimental data. The results showed that the predicted permeability values were in good agreement with those measured, confirming the proposed algorithm can capture the main flow paths of packed beds. The second methodology generated an equivalent pore network of porous media, of which the centers of voids were located in a regular lattice with constant pore center distance. However, this network allowed for matching both main geometrical and topological characteristics of the porous media. A comparison of the two approaches suggested that the second approach can also be used as a predictive tool to quantitatively study the microscopic properties of flow through porous media. Copyright © 2012 John Wiley & Sons, Ltd.

As species we humans generate excessive amounts of waste and hence for sustainability we should explore innovative ways to recover them. The primary objective of this study is to demonstrate an efficient and optimum way to recover chromium and iron from chromite ore processing residues (COPR) for the production of chrome steel and stainless steel. In Hudson County, New Jersey, there are more than two million tons of leftover COPR. Part of COPR was used as fill materials for construction sites, which spread the problem to a larger area. With high solubility along with their toxicity leached chromate from COPR is threatening the environment as well as human health. In this research, COPR was thermally treated to recover iron with chromium by applying techniques used in steel manufacturing. An extensive experimental program was performed using a Thermo-Gravimetric Analyzer (TGA) and bench scale tests to thermally treat the processed chromium contaminated soils with carbon and sand at varying temperatures and under reducing environment. The optimum chemical composition of COPR and additives to be used in the melts were evaluated based upon the thermodynamic properties of the mixture to ensure good phase separation, least amounts of iron and chromium oxides in the slag and minimum variability of final product (steel or iron with chromium). The impact of other oxides on the steel making process was evaluated to minimize the adverse impact on the process. The research demonstrated the feasibility of recovering a valuable construction material (chrome steel) from a waste (COPR).

This paper provides an overview of environmental issues in the coal-to-energy industry. Coal to energy will be the major energy source for foreseeable future. The waste generated from the coal-to-energy process and the ecological degradation during the mining and processing of coal are two main issues affecting coal as a future main energy source. Hence, this paper provides an overview of the solid waste and ecological issues during the coal-to-energy process and proposes ways to fully utilize coal fly ash and to mitigate the ecological issues. Fly ash, a major component of combustion waste of coal to energy, is an industrial by-product that is recognized as an environmental pol- lutant. Although it is treated as a waste, the mineral chemistry of fly ash is of economic value. The main reasons for the low utilization rate of coal fly ash and theways of achieving full utilization are discussed first. The issues involved in the storage of vast quantities of coal fly ash are also summarized. Based on the analysis, full utilization of coal fly ash is feasible in the United States by the processes of grinding fly ash and 40% cement replacement. However, such actions would require the development of a fly ash classification system accounting for pozzolanic activity and cementitious properties, alkali-aggregate reactivity, and sulfate resistance. Also discussed are the ecological issues and existing problems during coal mining including water pollution, coal mining waste, and land subsidence. Several proposed effective solutions were reviewed, and it was determined that the ecological degradation during mining could be minimized. DOI: 10.1061/(ASCE)HZ.1944-8376 .0000071. © 2011 American Society of Civil Engineers.