Wet Systems Research Articles

Identification of Microbiological Activities in Wet Flue Gas Desulfurization Systems

Thermoelectric power generation from coal requires large amounts of water, much of which is used for wet flue gas desulfurization (wFGD) systems that minimize sulfur emissions, and consequently, acid rain. The microbial communities in wFGDs and throughout thermoelectric power plants can influence system performance, waste processing, and the long term stewardship of residual wastes. Any microorganisms that survive in wFGD slurries must tolerate high total dissolved solids concentrations (TDS) and temperatures (50–60°C), but the inocula for wFGDs are typically from fresh surface waters (e.g., lakes or rivers) of low TDS and temperatures, and whose activity might be limited under the physicochemically extreme conditions of the wFGD. To determine the extents of microbiological activities in wFGDs, we examined the microbial activities and communities associated with three wFGDs. O2 consumption rates of three wFGD slurries were optimal at 55°C, and living cells could be detected microscopically, indicating that living and active communities of organisms were present in the wFGD and could metabolize at the high temperature of the wFGD. A 16S rRNA gene-based survey revealed that the wFGD-associated microbial communities included taxa attributable to both thermophilic and mesophilic lineages. Metatranscriptomic analysis of one of the wFGDs indicated an abundance of active Burholderiaceae and several Gammaproteobacteria, and production of transcripts associated with carbohydrate metabolism, osmotic stress response, as well as phage, prophages, and transposable elements. These results illustrate that microbial activities can be sustained in physicochemically extreme wFGDs, and these activities may influence the performance and environmental impacts of thermoelectric power plants.

Wastewater Management of Wet Scrubbers in Waste-to-energy Facilities: a Life Cycle Analysis

Nowadays, increasing attention is focused on the indirect impacts of emission control technologies and the potential burden shifting. A clear example is the generation of wastewater when wet scrubbing systems are used for flue gas cleaning. The present study takes into consideration a typical wet scrubber for waste-to-energy plants and the available options for wastewater management: physicochemical treatment, evaporation or valorisation. A comparative assessment of the environmental footprint of the alternatives is performed by taking into account the burdens related to the supply of reactants, energy and the disposal of process residues (solid and liquid waste streams). It is thus shown that the recovery of a marketable product from the effluent produces a net environmental benefit, while the choice between wastewater discharge or evaporation represents only a shift of burden between the water and the soil compartments.

Residual dune ridges: Sedimentary architecture, genesis, and implications for palaeo‐climate reconstructions

AbstractSedimentary architecture and genesis of residual dune ridges in a temperate climate are presented and implications for their use as archive of changes in long‐term precipitation and wind climate are discussed. Residual dunes are common features of wet aeolian systems, where they form sets of shallow ridges, oriented perpendicular to the prevailing wind direction. Residual dune ridges of the study area are vegetated and typically elevate 0.6 to 2.5 m above the surrounding interdune flats. They develop on the lower stoss side of active transgressive dunes, triggered by periods of elevated groundwater table and hence colonization of the foot of the dune by rapid growing pioneer vegetation. Stabilized by plants, the growing ridge detaches from the active transgressive dune and gets abandoned within years in the course of the downwind‐migration of the transgressive dune. Grain‐size data suggest a main sediment supply from the transgressive dune and only minor input from other sources. Ground‐penetrating radar reveals that the residual dune ridges are composed of windward‐dipping as well as leeward‐dipping sedimentary beds. Leeward‐dipping strata reflect sediment supply from the parental dune, whereas windward‐dipping beds are seen to result from sediment redistribution along the ridge and sediment supply from the adjacent swales during the ridge growth period. Multi‐annual to multi‐decadal variability in precipitation leads to the development of sequences composed of tens of ridges, spanning time periods of several centuries. Spacing of individual ridges in these sequences is controlled not by long‐term variability in precipitation alone, but probably also reflects variable wind intensity which affects the migration rate of the parental dune. The important role of vegetation in ridge construction makes these landforms a demonstrative example of landscape development by geo‐biosphere interacting processes.

Vertical and seasonal changes in soil carbon pools to vegetation degradation in a wet meadow on the Qinghai-Tibet Plateau

Wet meadows provide opportunities to decrease carbon dioxide (CO2) and methane (CH4) released into the atmosphere by increasing the soil organic carbon (SOC) stored in wetland systems. Although wet meadows serve as the most important and stable C sinks, there has been very few investigations on the seasonal distributions of SOC fractions in high-altitude wet meadows. Here, we studied the effects of four vegetation degradation levels, non-degraded (ND), lightly degraded (LD), moderately degraded (MD), and heavily degraded (HD), on the measured vertical and seasonal changes of SOC and its different fractions. Among these vegetation degradation levels, 0–10 and 10–20 cm soil depths in ND plots had significantly higher SOC contents than the other degradation levels had throughout the year. This is attributed to the relatively greater inputs of aboveground plant litter and richer fine-root biomass in ND plots. Particulate organic carbon (POC) and light fraction organic carbon (LFOC) showed similar vertical and seasonal variations in autumn, reaching a minimum. Moreover, microbial biomass (MBC) and easily oxidizable organic carbon (EOC) contents were highest in summer and the smallest in winter, while dissolved organic carbon (DOC) content was highest in spring and lowest in summer, and were mainly concentrated in the 0–20 cm layer. Pearson correlation analysis indicated that soil properties and aboveground biomass were significantly related to different SOC fractions. The results indicate that vegetation degradation reduces the accumulation of total SOC and its different fractions, which may reduce carbon sink capacity and soil quality of alpine wet meadows, and increase atmospheric environmental pressure. In addition, vegetation biomass and soil characteristics play a key role in the formation and transformation of soil carbon. These results strengthen our understanding of soil C dynamics, specifically related to the different C fractions as affected by vegetation degradation levels and soil depth, in wet meadow systems.

A theoretical study of particle coalescence criteria for inelastic collisions of wet particles

Individual wet particle collisions can significantly affect the macroscale behaviors of granular flow systems. The collision process between two wet particles consists of deformation and non-deformation stages. In each stage, a force model is required to describe the interactive mechanics. Forces vary in a fashion that the energy dissipates during the entire collision process, which further impacts the particle coalescence. In this study, the force model and energy dissipation mechanism at each collision stage are investigated. For the deformation stage, combined effects of adhesion and plastic deformation at the contact surface are considered. For the non-deformation stage, combined effects of capillary and viscous force are studied. Based on energy conservation, the particle coalescence criterion is characterized into three distinct types. The developed explicit expression for the contact force, restitution coefficient, and corresponding coalescence criteria can be further applied in modelling of wet granular flow systems.

Simulation of SO2 absorption and performance enhancement of wet flue gas desulfurization system

At the present moment wet flue gas desulfurization systems (WFGD) are widely used in the SO2 emitting industries. With the improvement of the SO2 emission standards and the use of fuel with high sulfur content, there is an urgent need to develop advanced modelling tools to explore the enhancing method of SO2 absorption process on the condition of flue gas with high SO2 concentration. In this study, a detailed mathematical model of tray scrubbers, which are adopted in several China’s power plants in order to treat SO2 rich flue gas, is developed to investigate the influencing factors of the SO2 absorption process. The model is validated by an experiment using pilot-scale WFGD experimental system and can describe the SO2 absorption process in WFGD to a satisfactory level. The influence factors of SO2 absorption of droplets and in spray tower are studied through the model. The effects of pH and tray on desulfurization efficiency are analyzed. Using the tray scrubber is better in order to realize the desulfurization of flue gas with high SO2 concentration rather than adjusting the pH of the slurry. This model can be regarded as a useful tool for equipment selection and operation optimization of WFGD system.

Durability and Failure Modes of Concrete Beams Strengthened with Polyurethane or Epoxy CFRP

Externally bonded carbon-fiber-reinforced polymer (CFRP) composites are increasingly being used for repair of concrete infrastructure. Both the mechanical performance and the long-term durability of such a repair have resulted in a significant body of research. However, polyurethane-based composites for concrete repair have seen only limited treatment to date. This paper investigates the effect of seven different environments on the durability and failure modes of two different wet lay-up CFRP systems applied to flexural reinforcement of concrete: a two-part epoxy and a preimpregnated, water catalyzed polyurethane with aromatic chemistry as a matrix. Durability of concrete, CFRP laminates, and small-scale CFRP-strengthened concrete flexural beams was investigated for each duration (125, 250, and 365 days) and accelerated conditioning environment. Inverse analysis with a numerical model was used to develop conditioned bond–slip models for each composite system. Results and failure modes of control and conditioned specimens showed that degradation of CFRP-strengthened beams was controlled by the conditioned concrete tensile strength and bond cohesive energy in the epoxy and polyurethane systems, respectively.

Colorimetry to assess the visual impact of dust deposition on mosaics at sheltered archaeological sites

One of the most important alteration factors for archaeological sites is the deposition of dust, primarily onto horizontal surfaces, because it affects both the conservation state of the remains and their appearance. The deposition is responsible for visual changes that prevent proper appreciation of the site, and this is especially negative for the decorative elements such as mosaics. Dust deposition has been seen as a significant problem in sheltered sites as opposed to those located in the open air, where deposits are regularly washed away. However, there is a lack of knowledge on the visual effects of dust on sheltered archaeological remains despite the fact that this information could help to determine cleaning regimes. This research has been undertaken at the House of Hippolytus, a Roman villa located on the outskirts of Complutum, situated where the city of Alcalá de Henares (Spain) stands today. The site was covered with a partially enclosed shelter in 1999 and it contains a magnificent mosaic in the central area. This ornamental floor is the center of attention for visitors and has often been used as a promotional image because of its high artistic value. This study has objectively evaluated the visual changes (color and spectral characteristics) of the mosaic at the House of Hippolytus before and after being cleaned with dry and wet systems using a novel approach based not only on a spectrophotometer (CM-2600d Konica Minolta®) but also on a LumiCam® 1300 camera (Instrument Systems GmbH). Although wet cleaning implies the use of water, which is a decay factor, it has been found to be the best option for recovering the original aspect of the mosaic.

3D printing hydrogels for actuators: A review

Soft and wet actuator systems have attracted great attention in some applications, such as assistive technologies for rehabilitation, training and regenerative biomedicines. Three-dimensional (3D) printing methods have realized the rapid fabrication of complex structures without the need for expensive dies or post processing. In this review, a comprehensive description is presented on stimuli-responsive hydrogels fabricated by light-responsive and extrusion-based 3D printing technologies. Mechanisms of actuations have been introduced based on stimuli types. As the most common method for 3D printed hydrogel actuators, direct-ink-writing has been discussed, including the two printing parameters of resolution and rheology. In addition, applications of 3D printed hydrogel actuators are presented followed by introductions of recent contributions on enhancing the toughness of 3D printed hydrogel and robust design tools, such as finite element analysis and artificial intelligence.

Direct Observation of Sulfate Explosive Growth in Wet Plumes Emitted From Typical Coal‐Fired Stationary Sources

AbstractThe origins of atmospheric sulfate production have previously been explained by focusing on air quality models and complex chemical reaction processes. Here, we first report direct observations of sulfate production in stack plumes discharged from coal‐fired power plants, industrial boilers, and sintering plants equipped with wet desulfurization systems. Less than one third of the particulate SO42− in plumes is attributed to dust‐SO42− and SO3 measured in stacks. The SO2 aqueous‐phase oxidation process is critical in explaining the unknown sulfate formation in plume droplets with pH values ranging from 2.3 to 2.8. When the rapidly formed sulfate in wet plumes is included, a notable amount of underestimated sulfate (∼0.24 Tg in 2017) is emitted from industrial stacks in China and can partially explain the “missing sulfate” on driving most particle pollution episodes. Policy‐making targeting particulate emissions is suggested to substantially reduce sulfate emissions for further air quality improvement.

Dust emission reduction in iron ore concentrate production plant using value engineering method.

Dust emission is one of the critical problems of the mining industry. Dust emission can cause respiratory diseases among workers and adjacent residents of the factory and environmental pollution in the region. This study aims to reduce dust emissions of an iron ore concentrate plant in Iran. Applying dust control methods can affect the production process. Therefore, in this study, the value engineering (VE) method has been used, which focuses on improving the processes without affecting the main functions. This method is implemented in three stages. In the pre-study stage of VE, the prerequisites of study, such as determining the management requirements, study scope, evaluation criteria, forming the VE team, and planning, were met. In the study stage, the required information was collected; the studied process functions were identified and ranked; 62 ideas were created based on the functions and then evaluated; the final scenarios for the selected device, hopper, were developed and ranked using the VIKOR method; and finally, confirmation of the results by the management was obtained. In the post-study stage, the results will be implemented. The approach of this study was based on maintaining the functions of the production process and production rate and finding the most effective solution to reduce dust and environmental hazards, the most efficient solution in terms of performance, and the most cost-effective solution in terms of fixed and variable costs. According to the results, dry and wet dust suppression systems are the best options among the scenarios to meet the objectives of this study.

Landscape level effects of invasive plants and animals on water infiltration through Hawaiian tropical forests

Watershed degradation due to invasion threatens downstream water flows and associated ecosystem services. While this topic has been studied across landscapes that have undergone invasive-driven state changes (e.g., native forest to invaded grassland), it is less well understood in ecosystems experiencing within-system invasion (e.g. native forest to invaded forest). To address this subject, we conducted an integrated ecological and ecohydrological study in tropical forests impacted by invasive plants and animals. We measured soil infiltration capacity in multiple fenced (i.e., ungulate-free)/unfenced and native/invaded forest site pairs along moisture and substrate age gradients across Hawaii to explore the effects of invasion on hydrological processes within tropical forests. We also characterized forest composition, structure and soil characteristics at these sites to assess the direct and vegetation-mediated impacts of invasive species on infiltration capacity. Our models show that invasive ungulates negatively affect soil infiltration capacity consistently across the wide moisture and substrate age gradients considered. Additionally, several soil characteristics known to be affected by invasive ungulates were associated with local infiltration rates, indicating that the long-term secondary effects of high ungulate densities in tropical forests may be stronger than effects observed in this study. The effect of invasive plants on infiltration was complex and likely to depend on their physiognomy within existing forest community structure. These results provide clear evidence for managers that invasive ungulate control efforts can improve ecohydrological function of mesic and wet forest systems critical to protecting downstream and nearshore resources and maintaining groundwater recharge.

Synthesis of Amidation Agents and Their Reactivity in Condensation Reactions

AbstractNowadays, the development of new approaches which smartly bypass the use of harsh reaction conditions and hazardous chemicals covers a pivotal role. In this research paper the synthesis, characterization, and application of novel libraries of triazine bis-quaternary ammonium salts, employed as coupling agents to produce amides is reported. Full characterization of the novel compounds by 1H and 13C NMR, FT-IR spectroscopy, ESI-HRMS, and elemental analysis is provided. Furthermore, a comparison in terms of activity of the preformed triazine compounds versus in situ formulations has been evaluated for the formation of amides in the presence of phenylethylamine and different aliphatic or aromatic acids. A possible correlation between the chemical structure of the triazine and their reactivity for the formation of the triazine bis-quaternary ammonium salts is also reported. Moreover, best performing condensation agents have been further tested for the cross-linking of collagen powder as possible wet white tanning systems, for sustainable and environmentally friendly leather tanning.

Mineral sequestration of CO2 from Vernasca Ca-looping demo system: scale up to a pilot

In recent years, carbon sequestration into thermodynamically stable carbonates has been developed as a promising carbon capture, utilization and storage (CCUS) method, especially, when alkaline industrial wastes are used as sorbents. The use of industrial wastes to sequester CO2 plays a dual role in environment protection, creating opportunities not only for capture and disposal of CO2 but also for recycling of wastes and promoting the transition to circular economy. The CLEANKER project (Horizon 2020 Project Clean clinker production by Calcium looping process) aims to build a CO2 mineralization pilot incorporated into Ca-looping demo system in Vernasca cement plant and use the re-carbonated wastes in concrete applications. Different types of wastes such as burnt oil shale (BOS) from Eesti, Balti and Auvere power plants as well as from Enefit280 oil producing unit in Estonia, concrete demolition wastes (CDW), cement by-pass dust (CBD) from Robilante, Italy, blast furnace slag (NSF) from Bremen, Germany were tested first in laboratory scale via dry and wet direct carbonation routes under the conditions of CO2-rich model gas flow of 70 – 100% CO2, simulating the Ca-looping system. The results show that selected types of BOS and cement wastes could be used as efficient binders in both dry and wet CO2 mineralization systems with binding capacities up to 0.18 kg of CO2 per kg of BOS and up to 0.24 kg of CO2 per kg of CBD. The activating effect of hydration as a pre-treatment method showed that at lower operating temperatures, the same level of CO2 capture can be achieved, thereby rendering the carbonization processes of similar industrial wastes more energy efficient. Moreover, the CO2 mineralization tests with BOS in a 46 L concrete mixer confirmed the applicability of wet carbonization process also in larger scale. Based on the results, the most promising materials, BOS and CBD, were selected for in the proposed CO2-mineralization process in wet conditions at ambient temperature. The pilot (200 L) was designed based on a commercially available concrete mixer integrated into CLEANKER Ca-looping demo system and equipped with CO2 inlets and outlets, as well as CO2, temperature and moisture sensors to detect the reaction progress. The re-carbonated wastes will be tested via concrete casting in order to demonstrate the quality of the commercial product in the following stages of the project.

Prevention of a hydrogen explosion accident in the wet aluminum waste dust collection process based on L-malic acid

To essentially solve the hydrogen explosion risk in wet aluminum waste dust collection systems employed in aluminum product processing, nontoxic and environmentally friendly L-malic acid was used to inhibit the hydrogen production reaction between aluminum waste dust and water. Experiments and chemical kinetic model analysis showed that when the L-malic acid concentration reached 0.15 g L−1, the hydrogen production reaction was almost completely suppressed. Scanning electron microscopy (SEM) with energy dispersive spectroscopy (EDS), Fourier transform infrared (FTIR) spectroscopy and adsorption theory were used to analyze the hydrogen suppression mechanism. The results showed that L-malic acid forms a chemical adsorption film on the surface of aluminum waste dust particles that can prevent particles from contacting water and realizes hydrogen suppression by preventing the reaction from proceeding. This method provides a design safety measure to prevent hydrogen explosion in wet aluminum waste dust collection systems and has good application prospects.

Development of a system of energy technological processing of coal deposits for energy and other industries

In connection with the forthcoming toughening of environmental requirements, including during the operation of energy facilities, as well as in order to more fully use the resources of the fuel and energy complex and mineral deposits in the Russian Federation, it is proposed to review the principles of developing coal deposits and preparing energy coal and other resources coal deposits for burning at thermal power plants. The main resources of coal deposits considered in this work are steam coal and mine gas, which is present in most coal deposits of the Russian Federation. The gas content of coal seams can reach 35 m3 in terms of 1 ton of dry ashless coal mass. Direct coal combustion at thermal power plants leads to the formation of a large number of emissions of substances that negatively affect the environment. The main emissions from coal flaring are fly ash and slag, toxic sulfur and nitrogen oxides, carbon monoxide and carbon dioxide. The following technologies are used to reduce the amount of these substances in the flue gases: wet and dry scrubber systems, the organization of fuel combustion, aimed at reducing toxin emissions (in particular nitrogen compounds), the use of various types of filters to clean flue gases from volatile ash and slag particles and etc. To increase the effectiveness of the fight against toxic and polluting emissions, the team of authors proposes to use solid fuel pre-processing as part of the operation of the energy technology plant together with the used cleaning systems. The type of energy technology plant, depending on the tasks to be solved within the development region, can be different. To implement the processes of energy technological processing and in the framework of reducing effluents from energy facilities, the issue of the reuse of highly mineralized, oil-contaminated and oiled wastewater from thermal power plants and highly mineralized wastewater from coal deposits, as well as the reuse of spent TPP lubricants in the plant cycle, is being considered. To increase the calorific value of the synthetic gas produced in the plant’s cycle, the issue of its joint combustion with purified mine gas produced in the coal field under development is considered. Mine gas is also cleaned in the plant cycle.

Comparing conventional wet EEG vs dry‐sensor wireless EEG to probe sensory processing and neuronal function in the aging brain

AbstractBackgroundNeurodegenerative conditions such as AD, PD and MS can develop slowly, making early detection and on‐going characterisation a challenge. Current methods rely primarily on clinical opinion/self‐reports, or on burdensome and expensive clinic‐based methods. Visual and other sensory evoked potential tasks, particularly with steady‐state stimulation, have been used to probe neuronal function in healthy aging (Sridhar & Manian 2019), and neurodegeneration (Jacob et al 2002, Viallate et al 2010), in pre‐clinical and symptomatic stages (Shahmiri et al 2017) – but using conventional lab/clinic based wired wet EEG systems. In this proof‐of‐concept study, we evaluate wireless dry EEG as a less burdensome alternative. If feasible this could provide an easy‐to‐use, scalable and objective measure of neuronal function, for use in larger longitudinal studies of these conditions.MethodsWe compare signals recorded from a wireless dry‐EEG headset (BrainWaveBank Ltd – Murphy 2018, 2019), and state‐of‐the‐art conventional wet‐EEG hardware (Biosemi ActiveTwo). Informed consent was obtained from 8 healthy adult males for this methodological study. Each attended 2 separate in‐lab sessions, one week apart, in which both dry and wet recordings were made. Static and flickering steady state (14Hz) visual stimulus conditions were presented. Grand average VEPs were calculated for each recording and stimulus condition. Signal stability was quantified using a Monte Carlo process to estimate 95% confidence intervals. From the steady state VEP, scalp topographies of spectral power were also computed.ResultsAfter band‐pass and notch filtering, a grand average of a simple visual‐evoked potential (Figure 1) recorded at posterior recording sites with the wireless dry‐EEG headset has similar waveform morphology and noise levels to that from conventional wet‐EEG equipment – as does the steady state VEP (Figure 2). Topographies of spectral power at 14 and 28Hz (Figure 3) show a similar central/posterior scalp distribution.ConclusionsIn controlled environments, a wireless dry‐sensor EEG headset can yield aggregate data of comparable quality to a state‐of‐the‐art wet‐EEG, making much larger scale studies of sensory processing and broader neuronal function possible for the first time.

Coordinated effects of air pollution control devices on PAH emissions in coal-fired power plants and industrial boilers

Coal-fired power plants are important sources of polycyclic aromatic hydrocarbon (PAH) emissions in the world. The effects of various air pollution control devices (APCDs) on PAH emissions were investigated by analyzing samples from inlets and outlets of APCDs in six coal-fired power plants (A–F) and two coal-fired industrial boilers (G and H). The APCDs were electrostatic precipitators (ESPs), wet flue gas desulfurization systems (WFGDs), and wet ESPs (WESPs). The PAH congener patterns for the coal-fired plants were similar. Gas-phase PAHs were dominant in flue gases, and the most abundant PAH was naphthalene. Three- and four-ring PAHs were dominant in fly ash. Positive correlations were found between the PAH and total organic carbon contents of fly ash (R2 0.87) and slag (R2 0.92). Plants D–F, equipped with low-low-temperature ESPs (LLT-ESPs) and WESPs discharged the lowest PAHs. Circulating water was an important source of PAHs in the desulfurization except in plant A, which used desalinated seawater rather than circulating water in the desulfurization process. WESPs decreased PAH concentrations by an average of 20.67%, which can be spread to other plants to reduce PAHs.

Hydrogel-Based Transparent Subdural Electrode with Salt Bridge As Interface to Brain Surface

Intraoperative biomedical devices are used in many medical fields such as monitoring, diagnosis and treatment of diseases. Subdural electrodes used in monitoring cortical activity contribute to an identification of pathological lesions in an epilepsy surgery and also the advance of elucidation of brain function. These electrodes as an interface with living systems should be flexible, biocompatible, and conformable to the curved brain surface. However, conventional electrodes consisting of metals such as Pt electrodes and a silicone-based substrate have not fully resolved mismatches between electronics circuit of a machine and biological wet systems, which causes a decrease of measurement accuracy and damage to bio-tissue[1]. In a previous study, we have developed a totally organic hydrogel-based subdural electrode by embedding a carbon fabric (CF) modified with poly(3,4-ethylenedioxythiophene) (PEDOT) into a poly(vinyl alcohol) (PVA) hydrogel substrate[2]. This wet electrode showed a good softness similar to the living tissue, a high conformability to a curved surface such as brains, and easy handling. Moreover, the totally organic nature would contribute to obtain clear MRI images without image artifacts.In this study, we have developed a new type of the hydrogel-based transparent subdural electrode in which the salt bridge acts as interface to bio-tissue (Fig. 1A). The present electrode consisted of three different parts, a salt bridge made of PVA hydrogel insulated by the microchannel made of Poly(dimethylpolysiloxane) (PDMS) membrane embedded into the PVA hydrogel substrate. The unique feature of the hydrogel-based electrode with the salt bridge system was aqueous-based interface to bio-tissue on which can be decreased an effect of the electrochemical reaction. The aqueous-based electrode similar to bio-tissue enable to be flexible, biocompatible, and conformable due to the use of highly soft and wet biomaterial. In addition, the device has an optical transparency which can contribute to obtaining detailed visual information under the electrode during surgical operations and would be valuable to the neuroscience in optogenetics.The PDMS membrane-based channel (thickness: 600 µm, width: 500 µm, height 100 µm) was fabricated by spin-coating at 700 rpm for 15 seconds on the SU-8 mold and bonding with an oxygen plasma treatment. PVA (Mw~145000) hydrogels for both a salt bridge (10 wt%) and substrate (15 wt%) were dissolved in a mixture of dimethyl sulfoxide (DMSO) and saturated KCl solution (mass ratio = 4:1). The PDMS membrane-based channel connected to the silicone tube for extension was filled with PVA hydrogel as a salt bridge, sandwiched by glass slides with 1.5 mm-thickness spacer which was filled with the PVA hydrogel, and crosslinked by freeze-thaw cycles (as -30 °C for 10 min and 4 °C for 10 min, each repeated three times). The fabricated electrode was rinsed twice in Ringer’s solution for one hour and overnight. The conformability was evaluated by the rate of contact area between electrodes and the surface of the curved sheet with various curvatures. In vivo recording was conducted on a porcine which was anaesthetized with the head fixed in a stereotaxic apparatus, and the dura mater was partially removed by a neurosurgeon to expose the surface of the cerebral cortex. Then, electrodes were placed on the exposed cortex on each hemisphere for simultaneous electrocorticography (ECoG) recording (2019MdA-324).Figure 1B shows the conformability of the developed and conventional electrode to the curved surface. The contact area of the hydrogel electrode showed more than 80 %, which was higher conformable than that of the silicone-based conventional electrode (~ 50 %). Figure 1C shows that the hydrogel electrode consisting of PVA hydrogels and PDMS as a highly transparent and biocompatible material, showed a sufficiently transparent to recognize the condition under the device. In contrast, the commercially available electrode was opaque due to thick silicone-based substrate and metal. As shown in Figure 1D, we successfully measured brain waves by the hydrogel electrode with the salt bridge system in vivo measurements on porcine. From this result, the salt bridge acted as the resistance for ionical connection and ionically connected from bio-tissue to electronic measurement machine. We successfully developed a new hydrogel-based transparent subdural electrode with the salt bridge as a bio-friendly interface.

The role of dry anaerobic digestion in the treatment of the organic fraction of municipal solid waste: A systematic review

Anaerobic digestion (AD) has been seen as an attractive alternative for the treatment of the organic fraction of municipal solid waste (OFMSW), with the potential to provide useful products such as bio-methane, bio-hydrogen, and a highly concentrated compost. Among the different AD technological routes, dry AD stands out because it makes better use of resources and can handle higher solids concentration, being more robust and flexible as compared to wet AD systems. In this contribution, a systematic review was carried out on the evolution of AD systems, giving emphasis to the role of the dry AD route for OFMSW treatment throughout the last 15 years. As it has been seen as a current trend in the field, the opportunities for technological development of dry AD systems and the challenges to be faced for their implementation in large-scale settings were assessed. Furthermore, aspects associated with input substrates and biodigesters operating conditions were addressed, along with the most important dry AD reactor configurations and commercial technologies. The research studies show that dry AD is most implemented under mesophilic conditions in continuous processes. Furthermore, apart from being influenced by many operational factors (temperature, pH, total solids content, substrate to inoculum ratio, organic loading rate and hydraulic/solids retention time), the performance of dry AD systems in terms of biogas productivity depends on the characteristics of the substrates, co-substrates and inoculum. Laboratory-scale tests are found to be essential to overcome the operational obstacles in full-scale plants, allowing for better system performance, stability and process control.