Treating produced water from hydraulic fracturing: Composition effects on scale formation and desalination system selection

Produced water from unconventional gas and oil extraction may be hypersaline with uncommon combinations of dissolved ions. The aim of this analysis is to aid in the selection of produced water treatment technology by identifying the temperature, pH, and recovery ratio under which mineral solid formation from these produced waters is likely to occur. Eight samples of produced water from the Permian Basin and the Marcellus shale are discussed, with an average TDS of about 177 g/L but significant variability. Crystallization potential is quantified by the saturation index, and activity coefficients are calculated using the Pitzer model. The method is applied to estimate solid formation in the treatment of two design case samples: a 183 g/L sample representing the Permian Basin water and a 145 g/L sample representing the Marcellus. Without pretreatment, the most likely solids to form, defined by highest saturation index, are: CaCO[subscript 3], FeCO[subscript 3], MgCO[subscript 3], MnCO[subscript 3], SrCO[subscript 3], BaSO[subscript 4], CaSO[subscript 4], MgSO[subscript 4] and SrSO[subscript 4]. Some options for mitigating the formation of these scales are discussed. With appropriate pretreatment, it is estimated that recovery ratios of as high as 40–50% are achievable before NaCl, a major constituent, is likely to limit further concentration without significant crystallization.Center for Clean Water and Clean Energy at MIT and KFUPM (Project R4-CW-08)MIT Energy InitiativeMIT Martin Family Society of Fellows for Sustainabilit

Entropy generation in condensation in the presence of high concentrations of noncondensable gases

The physical mechanisms of entropy generation in a condenser with high fractions of noncondensable gases are examined using scaling and boundary layer techniques, with the aim of defining a criterion for minimum entropy generation rate that is useful in engineering analyses. This process is particularly relevant in humidification-dehumidification desalination systems, where minimizing entropy generation per unit water produced is critical to maximizing system performance. The process is modeled by a consideration of the vapor/gas boundary layer alone, as it is the dominant thermal resistance and, consequently, the largest source of entropy production in many practical condensers with high fractions of noncondensable gases. Most previous studies of condensation have been restricted to a constant wall temperature, but it is shown here that for high concentrations of noncondensable gases, a varying wall temperature greatly reduces total entropy generation rate. Further, it is found that the diffusion of the condensing vapor through the vapor/noncondensable mixture boundary layer is the larger and often dominant mechanism of entropy production in such a condenser. As a result, when seeking to design a unit of desired heat transfer and condensation rates for minimum entropy generation, minimizing the variance in the driving force associated with diffusion yields a closer approximation to the minimum overall entropy generation rate than does equipartition of temperature difference.Center for Clean Water and Clean Energy at MIT and KFUPM (Project R4-CW-08)Eni S.p.A. (Firm) (Eni-MIT Energy Fellowship

B cells are capable of independently eliciting rapid reactivation of encephalitogenic CD4 T cells in a murine model of multiple sclerosis

<div><p>Recent success with B cell depletion therapies has revitalized efforts to understand the pathogenic role of B cells in Multiple Sclerosis (MS). Using the adoptive transfer system of experimental autoimmune encephalomyelitis (EAE), a murine model of MS, we have previously shown that mice in which B cells are the only MHCII-expressing antigen presenting cell (APC) are susceptible to EAE. However, a reproducible delay in the day of onset of disease driven by exclusive B cell antigen presentation suggests that B cells require optimal conditions to function as APCs in EAE. In this study, we utilize an <i>in vivo</i> genetic system to conditionally and temporally regulate expression of MHCII to test the hypothesis that B cell APCs mediate attenuated and delayed neuroinflammatory T cell responses during EAE. Remarkably, induction of MHCII on B cells following the transfer of encephalitogenic CD4 T cells induced a rapid and robust form of EAE, while no change in the time to disease onset occurred for recipient mice in which MHCII is induced on a normal complement of APC subsets. Changes in CD4 T cell activation over time did not account for more rapid onset of EAE symptoms in this new B cell-mediated EAE model. Our system represents a novel model to study how the timing of pathogenic cognate interactions between lymphocytes facilitates the development of autoimmune attacks within the CNS.</p></div

Effect of mass extractions and injections on the performance of a fixed-size humidification–dehumidification desalination system

The impact of mass extractions and injections as a method for increasing the energetic performance of fixed-size humidification–dehumidification desalination systems is examined. Whereas previous studies of this problem have been restricted to thermodynamic models, the use of a more complete model that includes transport provides the ability to quantify the impact of mass extractions/injections on a realizable, fixed-size system. For a closed air, open water cycle, the results show that a single water extraction from the dehumidifier to the humidifier increases the gained output ratio by up to 10%, with extractions higher in the cycle proving more effective. The sizing problem for the humidifier and dehumidifier under thermodynamically optimized conditions found in literature is also discussed, as is the impact of system size on overall performance of a system without extractions/injections. For a range of sizes, it is shown that a rough doubling of both dehumidifier and humidifier size results in a two- to three-fold increase in gained output ratio, with diminishing returns as the absolute sizes increase.Center for Clean Water and Clean Energy at MIT and KFUPM (Project R4-CW-08)Eni S.p.A. (Firm)MIT Martin Family Society of Fellows for Sustainabilit

Energy consumption in desalinating produced water from shale oil and gas extraction

On-site treatment and reuse is an increasingly preferred option for produced water management in unconventional oil and gas extraction. This paper analyzes and compares the energetics of several desalination technologies at the high salinities and diverse compositions commonly encountered in produced water from shale formations to guide technology selection and to inform further system development. Produced water properties are modeled using Pitzer's equations, and emphasis is placed on how these properties drive differences in system thermodynamics at salinities significantly above the oceanic range. Models of mechanical vapor compression, multi-effect distillation, forward osmosis, humidification–dehumidification, membrane distillation, and a hypothetical high pressure reverse osmosis system show that for a fixed brine salinity, evaporative system energetics tend to be less sensitive to changes in feed salinity. Consequently, second law efficiencies of evaporative systems tend to be higher when treating typical produced waters to near-saturation than when treating seawater. In addition, if realized for high-salinity produced waters, reverse osmosis has the potential to achieve very high efficiencies. The results suggest a different energetic paradigm in comparing membrane and evaporative systems for high salinity wastewater treatment than has been commonly accepted for lower salinity water.Center for Clean Water and Clean Energy at MIT and KFUPM (Project R4-CW-08)Center for Clean Water and Clean Energy at MIT and KFUPM (Project R13-CW-10)National Science Foundation (U.S.). Graduate Research Fellowship (Grant 1122374)Masdar Institute of Science and Technology (Massachusetts Institute of Technology Cooperative Agreement 02/MI/MI/CP/11/07633/GEN/G/00

Oxidative Decontamination of Tritiated Materials Employing Ozone Gas

The Princeton Plasma Physics Laboratory has developed a process by which to significantly reduce surface and near surface tritium contamination from various materials. The Oxidative Tritium Decontamination System (OTDS) reacts gaseous state ozone (accelerated by presence of catalyst), with tritium entrained/deposited on the surface of components (stainless steel, copper, plastics, ceramics, etc.), for the purpose of activity reduction by means of oxidation-reduction chemistry. In addition to removing surface and near surface tritium contamination from (high monetary value) components for reuse in non-tritium environments, the OTDS has the capability of removing tritium from the surfaces of expendable items, which can then be disposed of in a less expensive fashion. The OTDS can be operated in a batch mode by which up to approximately 40 pounds of tritium contaminated (expendable) items can be processed and decontaminated to levels permissible for free release (less than1,000 dpm/100 cm 2). This paper will discuss the OTDS process, the level of tritium surface contamination removed from various materials, and a technique for ''deep scrubbing'' tritium from subsurface layers

Thermodynamic Balancing of the Humidification Dehumidification Desalination System by Mass Extraction and Injection

Humidification dehumidification (HDH) is a promising technology for small scale seawater desalination and has received widespread attention in recent years. The biggest roadblock to commercialization of this technology is its relatively high energy consumption. In this paper, we propose thermodynamic balancing of the humidifier or the dehumidifier through mass extraction and injection as a potential means of reducing the energy consumption of these systems. Balancing minimizes the entropy generation caused by imbalance in driving temperature and concentration differences. We outline a procedure to model the system, using on-design component variables, such that continuous or discrete extraction and/or injection of air from the humidifier to the dehumidifier or vice versa can be analyzed. We present an extraction profile (mass flow rate ratio versus non-dimensional position) in the dehumidifier and the humidifier for attaining close to complete thermodynamic reversibility in an HDH system with a 100% effective humidifier and dehumidifier. Further, we have examined in detail the effect of having finite-sized systems, of balancing the humidifier versus the dehumidifier, and that of the number of extractions.Center for Clean Water and Clean Energy at MIT and KFUPM (Project R4-CW-08)United States. Dept. of State (International Fulbright Science & Technology Award

The ALFALFA "Almost Darks" Campaign: Pilot VLA HI Observations of Five High Mass-to-Light Ratio Systems

We present VLA HI spectral line imaging of 5 sources discovered by ALFALFA. These targets are drawn from a larger sample of systems that were not uniquely identified with optical counterparts during ALFALFA processing, and as such have unusually high HI mass to light ratios. These candidate "Almost Dark" objects fall into 4 categories: 1) objects with nearby HI neighbors that are likely of tidal origin; 2) objects that appear to be part of a system of multiple HI sources, but which may not be tidal in origin; 3) objects isolated from nearby ALFALFA HI detections, but located near a gas-poor early-type galaxy; 4) apparently isolated sources, with no object of coincident redshift within ~400 kpc. Roughly 75% of the 200 objects without identified counterparts in the $\alpha$.40 database (Haynes et al. 2011) fall into category 1. This pilot sample contains the first five sources observed as part of a larger effort to characterize HI sources with no readily identifiable optical counterpart at single dish resolution. These objects span a range of HI mass [7.41 < log(M$_{\rm HI}$) < 9.51] and HI mass to B-band luminosity ratios (3 < M$_{\rm HI}$/L$_{\rm B}$ < 9). We compare the HI total intensity and velocity fields to SDSS optical imaging and to archival GALEX UV imaging. Four of the sources with uncertain or no optical counterpart in the ALFALFA data are identified with low surface brightness optical counterparts in SDSS imaging when compared with VLA HI intensity maps, and appear to be galaxies with clear signs of ordered rotation. One source (AGC 208602) is likely tidal in nature. We find no "dark galaxies" in this limited sample. The present observations reveal complex sources with suppressed star formation, highlighting both the observational difficulties and the necessity of synthesis follow-up observations to understand these extreme objects. (abridged)Comment: Astronomical Journal, in pres

The scale dependence and structure of convergence fields preceding the initiation of deep convection

Links between convergence and convection are poor in global models, and poor representation of convection is the source of many model biases in the tropics. State-of-the-art convection-permitting simulations allow us to analyze realistic convection statistically. The analysis of fractal dimension is used to show that in convection-permitting simulations (grid spacings 1.5, 4, and 12 km) of the West African monsoon, 50% of deep convective initiations occur in the near vicinity of low-level boundary layer convergence lines that are orientated along the mean wind. In these simulations, more than 80% of the initiations occur within large-scale (300 × 300 km) convergence, with some 20% in large-scale divergence, and almost all cases occur within local scale (60 × 60 km) convergence. The behavior alters in a simulation with a convection scheme and a grid spacing of 12 km; initiation is less frequent over convergence lines, and there is less dependency on high-magnitude low-level local convergence. Key Points Fifty percent of storms initiate along convergence lines Most initiations occur in large and local scale convergence Parameterized convection exhibits a weaker dependence on strong convergence ©2014. American Geophysical Union. All Rights Reserved

Comparison of symptomatic and functional responses to vagus nerve stimulation in ANTHEM-HF, INOVATE-HF, and NECTAR-HF

AIMS: Clinical studies of vagal nerve stimulation (VNS) for heart failure with reduced ejection fraction have had mixed results to date. We sought to compare VNS delivery and associated changes in symptoms and function in autonomic regulation therapy via left or right cervical vagus nerve stimulation in patients with chronic heart failure (ANTHEM-HF), increase of vagal tone in heart failure (INOVATE-HF), and neural cardiac therapy for heart failure (NECTAR-HF) for hypothesis generation. METHODS AND RESULTS: Descriptive statistics were used to analyse data from the public domain for differences in proportions using Pearson\u27s chi-square test, differences in mean values using Student\u27s unpaired t-test, and differences in changes of mean values using two-sample t-tests. Guideline-directed medical therapy recommendations were similar across studies. Fewer patients were in New York Heart Association 3, and baseline heart rate (HR) was higher in ANTHEM-HF. In INOVATE-HF, VNS was aimed at peripheral neural targets, using closed-loop delivery that required synchronization of VNS to R-wave sensing by an intracardiac lead. Pulse frequency was low (1-2 Hz) because of a timing schedule allowing ≤3 pulses of VNS following at most 25% of detected R waves. NECTAR-HF and ANTHEM-HF used open-loop VNS delivery (i.e. independent of any external signal) aimed at both central and peripheral targets. In NECTAR-HF, VNS delivery at 20 Hz caused off-target effects that limited VNS up-titration in a majority of patients. In ANTHEM-HF, VNS delivery at 10 Hz allowed up-titration until changes in HR dynamics were confirmed. Six months after VNS titration, significant improvements in both HR and HR variability occurred only in ANTHEM-HF. When ANTHEM-HF and NECTAR-HF were compared, greater improvements from baseline were observed in ANTHEM-HF in standard deviation in normal-to-normal R-R intervals (94 ± 26 to 111 ± 50 vs. 146 ± 48 to 130 ± 52 ms; P \u3c 0.001), left ventricular ejection fraction (32 ± 7 to 37 ± 0.4 vs. 31 ± 6 to 33 ± 6; P \u3c 0.05), and Minnesota Living with Heart Failure mean score (40 ± 14 to 21 ± 10 vs. 44 ± 22 to 36 ± 21; P \u3c 0.002). When compared with INOVATE-HF, greater improvement in 6-min walk distance was observed in ANTHEM-HF (287 ± 66 to 346 ± 78 vs. 304 ± 111 to 334 ± 111 m; P \u3c 0.04). CONCLUSIONS: In this post-hoc analysis, differences in patient demographics were seen and may have caused the differential responses in symptoms and function observed in association with VNS. Major differences in technology platforms, neural targets, VNS delivery, and HR and HR variability responses could have also potentially played a very important role. Further study is underway in a randomized controlled trial with these considerations in mind