Successful Long-term Operation Research Articles

Deconfinement of runaway electrons by local vertical magnetic field perturbation

Runaway electron (RE) deconfinement and subsequent suppression is of prime importance for successful long-term operation of any tokamak. In this work, to deconfine and mitigate REs, the efficacy of local vertical field (LVF) perturbation has been explored numerically. LVF perturbation-assisted RE loss studies are carried out by simulating the drift orbits of the REs in magnetostatic perturbed fields and estimating the resulting orbit losses for different initial energies and magnitudes of LVF perturbation. To this end, the pre-existing PARTICLE code has been extended to the relativistic full-orbit-following code PARTICLE-3D (P3D) integrated with the magnetic field calculation code EFFI and plasma equilibrium field calculation code IPREQ to include the required fields for studying particle dynamics in general; this is then used to numerically model LVF perturbation-assisted RE deconfinement experiments conducted in the ADITYA tokamak. Simulation results show a significant (∼90%) deconfinement of REs with the application of LVF perturbation of a suitable amplitude (∼0.1% of the total magnetic field) in a preferred direction. The existence of a threshold magnitude of the applied field is also established, which is observed to be dependent on the energy of the REs. The simulation results reproduce all the experimental observations and reveal other interesting features of RE mitigation using LVF perturbation. The temporal map of orbiting time of REs shows that REs originating from the inboard side edge region ( ψ N > 0.5) of the plasma are relatively more prone to be lost with the application of suitable LVF perturbation than those originating from the plasma core. Interestingly, the simulation results demonstrate the existence of strong correlation between the safety factor (q) profile in the plasma edge region ( ψ N > 0.7) and the level of RE deconfinement using LVF perturbation.

A Critical Review of Systems for Bioremediation of Tannery Effluent with a Focus on Nitrogenous and Sulfurous Species Removal and Resource Recovery

Tanneries generate copious amounts of potentially toxic sludge and effluent from the processing of skins and hides to leather. The effluent requires remediation before discharge to protect the receiving environment. A range of physicochemical methods are used for pre- and post-treatment, but biological secondary remediation remains the most popular choice for the reduction of the organic and macronutrient fraction of tannery effluent. This review provides an update and critical discussion of biological systems used to remediate tannery effluent. While the conventional activated sludge process and similar technologies are widely used by tanneries, they have inherent problems related to poor sludge settling, low removal efficiencies, and high energy requirements. Treatment wetlands are recommended for the passive polishing step of beamhouse effluent. Hybrid systems that incorporate anoxic and/or anaerobic zones with sludge and/or effluent recycling have been shown to be effective for the removal of organics and nitrogenous species at laboratory scale, and some have been piloted. Novel systems have also been proposed for the removal and recovery of elemental sulfur and/or energy and/or process water in support of a circular economy. Full-scale studies showing successful long-term operation of such systems are now required to convince tanneries to modernize and invest in new infrastructure.

100 W-class green hydrogen production from ammonia at a dual-layer electrode containing a Pt-Ir catalyst for an alkaline electrolytic process

Ammonia allows storage and transport of hydrogen over long distances and is an attractive potential hydrogen carrier. Electrochemical decomposition has recently been used for the conversion of ammonia to hydrogen and is regarded as a future technology for production of CO2-free pure hydrogen. Herein, a heterostructural Pt-Ir dual-layer electrode is developed and shown to achieve successful long-term operation in an ammonia electrolyzer with an anion exchange membrane (AEM). This electrolyzer consisted of eight membrane electrode assemblies (MEAs) with a total geometric area of 200 cm2 on the anode side, which resulted in a hydrogen production rate of 25 L h−1. We observed the degradation in MEA performance attributed to changes in the anode catalyst layer during hydrogen production via ammonia electrolysis. Furthermore, we demonstrated the relationship between the ammonia oxidation reaction (AOR) and the oxygen evolution reaction (OER).

Sub-surface drainage: A win-win technology for achieving carbon neutrality and land amelioration in salt-affected Vertisols of India

This study aims to investigate the long-term impact of subsurface drainage (SSD) in restoring the soil quality and sugarcane productivity of waterlogged saline Vertisols. A combination of methodologies including analytical techniques, collection of soil and water samples and field survey with farmers was applied to collect the data, and drawing the inferences. The results indicated that successful long-term operation of SSD improved soil quality. A significant reduction in soil salinity (ECe) (Kavathesar site: 13.27 to 2.61, Shedshal site: 33.21 to 13.72 dS m−1) was observed. An appreciable improvement in soil bio-physico-chemical properties including organic carbon (OC%) (Kavathesar site: 0.48 to 0.63, Shedshal site: 0.22 to 0.44%) and dehydrogenase activity (DHA) (Kavathesar site:10.22 to 13.87, Shedshal site: 4.01 to 17.16 μg g−1 24 h−1), alkaline phosphatase (ALPA) (Kavathesar site:74.00 to 93.00, Shedshal site: 34.00 to 61.00 μg P-NP g−1 h−1), bulk density (BD) (Kavathesar site: 1.17 to 1.13, Shedshal site: 1.19 to 1.07 Mg m−3), saturated hydraulic conductivity (SHC) (Kavathesar site: 2.38 to 3.20, Shedshal site: 1.70 to 2.95 cm day−1) was found on surface (0–30 cm) layer comparing to their control sites (without SSD). The principal component analysis (PCA) showed that % OC, ECe, BD, and available K content were the most contributing factor for soil quality index (SQI). The improved soil quality has resulted in increasing the sugarcane yield by 226.8 and 585.5% at Kavathesar and Shedshal sites, respectively. The farmers' perception revealed that SSD technology (adopted on community scale) could play substantial role in improving the soil condition, and thereby enhancement in the yield of sugarcane crop. Thus, SSD technology was observed to have great potential in improving soil quality, crop (sugarcane) productivity, farmers' income and ensuring land degradation neutrality goal under saline Vertisols of India. Therefore, the large-scale adoption of SSD, managed with regional planning and strong cooperation among the stakeholders, may fulfil the promise of Sustainable Development Goals (SDGs) including Life on Land, No Poverty and Zero Hunger in degraded black saline soils.

Enhancing coking tolerance of flat-tube solid oxide fuel cells for direct power generation with nearly-dry methanol

The state-of-the-art Ni/yttria-stabilized zirconia (YSZ) anodes in direct methanol solid oxide fuel cells (SOFCs) are vulnerable to carbon deposition. We propose two strategies to enhance coking tolerance of the cell, focusing on promoting the oxygen storage capacity of the Ni/YSZ anode and the methanol conversion in flat-tube SOFCs with an active area of 60 cm2. The Ni/YSZ anodes are decorated with nanosized gadolinia-doped ceria (GDC) by wet impregnation method and the fuel channels are filled with extra GDC-Ni/YSZ catalyst. Through these measures, carbon deposition in the modified cells is mitigated, and therefore the steam/carbon (S/C) ratio for successful long-term cell operation is significantly lowered, and the cell durability is improved. A GDC-Ni/YSZ cell with extra catalyst is operated for over 1200 h directly on methanol under low S/C ratios at 750 °C and carbon deposition is considerably suppressed. In addition, the degradation mechanism of the cell directly fueled with nearly-dry methanol (S/C = 0.1) is investigated. This work provides insight into efficient and durable SOFCs using biofuels, towards renewable energy conversion in large-scale commercial applications.

Causes of defects in subway tunnels, their influence on the operational condition and remedy methods

Problem. The most important task in the field of construction and operation of subway tunnels is to solve the issue of assessing their technical condition. Timely detection, objective assessment of the development process of damage and defects of underground structures and their timely elimination are the key to successful long-term operation. Goal. The goal is to find the causes of defects and destruction of elements of subway tunnels in the process of operation and construction for their analysis and gaining experience in their prevention and methods of their elimination. Methodology. The experience of operating subways shows that destructive processes often occur in underground structures, which are not immediately visible during supervision. Therefore, the real condition of the building is revealed already in emergency conditions. To prevent this, it is necessary to clearly understand the nature and causes of damage at an early stage and eliminate them in a timely manner. Results. Considering geotechnological processes and the human factor in the process of construction and operation of underground structures is of great importance in modern conditions. Originality. Studies of the nature of more common defects and destructions in the load-bearing structures of tunnels confirm the difficulty of predicting the possible causes that lead to emergency situations. Practical value. During the construction and operation of tunnels and subways, it is necessary to take into account hidden processes that occur in underground structures.

High-Power Hybrid Solid-State Lithium–Metal Batteries Enabled by Preferred Directional Lithium Growth Mechanism

Solid electrolytes are revolutionizing the field of lithium–metal batteries; however, their practical implementation has been impeded by the interfacial instability between lithium metal electrodes and solid electrolytes. While various interlayers have been suggested to address this issue in recent years, long-term stability with repeated lithium deposition/stripping has been challenging to attain. Herein, we successfully operate a high-power lithium–metal battery by inducing the preferred directional lithium growth with a rationally designed interlayer, which employs (i) crystalline-direction-controlled carbon material providing isotropic lithium transports, with (ii) prelithium deposits that guide the lithium nucleation direction toward the current collector. This combination ensures that the morphology of the interlayer is mechanically robust while regulating the preferred lithium growth underneath the interlayer without disrupting the initial interlayer/electrolyte interface, enhancing the durability of the interface. We illustrate how these material/geometric optimizations are conducted from the thermodynamic considerations, and its applicability is demonstrated for the garnet-type Li7–xLa3–aZr2–bO12 (LLZO) solid electrolytes paired with the capacity cathode. It is shown that a lithium–metal cell with the optimized amorphous carbon interlayer with prelithium deposits exhibits outstanding room-temperature cycling performance (99. 6% capacity retention after 250 cycles), delivering 4.0 mAh cm–2 at 2.5 mA cm–2 without significant degradation of the capacity. The successful long-term operation of the hybrid solid-state cell at room temperature (approximately a cumulative deliverable capacity of over 1000 mAh cm–2) is unprecedented and records the highest performance reported for lithium–metal batteries with LLZO electrolytes until date.

Recovery Mechanisms in Aged Kesterite Solar Cells.

For successful long-term deployment and operation of kesterites Cu2ZnSn(SxSe1–x)4 (CZTSSe) as light-absorber materials for photovoltaics, device stability and recovery in kesterite solar cells are investigated. A low-temperature heat treatment is applied to overcome the poor charge extraction that developed in the natural aging process. It is suggested that defect states at aged CZTSSe/CdS heterojunctions were reduced, while apparent doping density in the CZTSSe absorber increased due to Cd/Zn interdiffusion at the heterojunction during the annealing process. In situ annealing experiments in a transmission electron microscope were used to investigate the elemental diffusion at the CZTSSe/CdS heterojunction. This study reveals the critical role of heat treatment to enhance the absorber/Mo back contact, improve the quality of the absorber/buffer heterojunction, and recover the device performance in aged kesterite thin-film solar cells.

Finite Element Method Study of Nanostructured Metal Oxide Based on NiO for Nonenzymatic Urea Sensors

Urea electrooxidation has attracted increasing attention because urea is an essential biomarker for diagnosing kidney conditions. Most urea sensors are based on the enzyme; however, enzyme-based sensors have a moderately complicated assembling method [1] due to poor stability. Different from the bulk diffusion of urea in the enzymatic urea oxidation [2], the nonenzymatic urea oxidation has reactions between the reductive and oxidative at the electrode surface [3]. Moreover, in order to use nonenzymatic urea sensors in a biomedical application area, high conductivity and catalytic activities are required. Therefore, a study of nonenzymatic urea sensor on a nanostructured electrode is of substantial interest.For urea detection, various metal oxides, such as ZnO [4], CuO [5], and NiO [6], have been broadly proposed. Practically, NiO catalysts were studied extensively for urea electrooxidation due to successful long-term operation [7]. Typical nonenzymatic catalysts for urea electrooxidation mainly focused on designing new nanostructures and maximizing their catalytic ability. However, quantitative models integrating the physical, chemical, and geometrical design properties still need improvement to develop sensor devices. The urea reaction occurs on the surface of nanostructured metal oxide. Thus, the effect of electrode geometry on the electrochemical reactions is motivated to explore urea sensors application.In the present study, we studied three different NiO structures such as nanorods, nanoflakes, and nanoparticles, for the nonenzymatic electrochemical sensor. Additionally, we developed a new analytical model to understand the nonenzymatic urea sensor using the finite element method. To further adjust the model, the morphology and the composition of the NiO catalysts were investigated using transmission electron microscopy, scanning electron microscopy, and X-ray photoelectron spectroscopy. The NiO catalysts showed remarkable electrochemical achievement with acceptable linear sensitivity and selectivity to urea electrooxidation. Comprehensive information of the modeling concerning NiO as a catalyst in the nonenzymatic urea sensor will be given.References FATEMA, Kamrun Nahar, et al. “New Design of Active Material Based on YInWO4-G-SiO2 for a Urea Sensor and High Performance for Nonenzymatic Electrical Sensitivity.” ACS Biomaterials Science & Engineering, 2020.Debata, Suryakanti, et al. "Design of CdV2O4-V6O13 micro flowers for non-enzymatic electrochemical detection of urea." In AIP Conference Proceedings, vol. 2115, no. 1, p. 030058. AIP Publishing LLC, 2019.YOON, Jaesik, et al. “Silver-Nanoparticle-Decorated NiOOH Nanorods for Electrocatalytic Urea Sensing.” ACS Applied Nano Materials, 2020, 3.8: 7651-7658.YOON, Jaesik, et al. “Ag/ZnO Catalysts with Different ZnO Nanostructures for Non‐enzymatic Detection of Urea.” Electroanalysis, 2019, 31.1: 17-21.Goda, M. A., et al. “Enhanced Electrocatalytic Oxidation of Urea at CuOx-NiOx Nanoparticle-Based Binary Catalyst Modified Polyaniline/GC Electrodes.” Journal of The Electrochemical Society, 2020 167(6), 064522.Tyagi, Manisha, et al. "NiO nanoparticle-based urea biosensor." Biosensors and Bioelectronics 2013, 41:110-115.BARAKAT, Nasser AM, et al. “Influence of nitrogen doping on the electrocatalytic activity of Ni-incorporated carbon nanofibers toward urea oxidation.” International Journal of Hydrogen Energy, 2017, 42.34: 21741-21750.

Gas Absorption in Package Using Au/Pt/Ti Bonding Layer

Vacuum packaging is required for the successful long-term operation of various kinds of micro-electromechanical system (MEMS) devices. The following points are important to complete and maintain encapsulated internal vacuum conditions: Degassing MEMS assemblies before packagingPackaging MEMS devices without leakageAbsorbing residual gases after packaging Our research group has developed a simplified MEMS packaging process using a Au/Ti layer (from top to bottom) as a bonding and gettering layer[1]. The assemblies were firstly metalized with thin Au/Ti films. The Au surfaces formed direct bonding without leakage even at room temperature. Moreover, when the packaged structure was annealed at 200 °C, the Ti atoms diffused to the inner surface of the package and absorbed residual gas molecules. This approach allows the simplification of the MEMS packaging process as the bonding and gettering layers can be simultaneously fabricated.However, we found that the Au/Ti film cannot form bonding after degas annealing at 200 °C because Ti oxides were formed on the surface. The annealing at 200 °C effectively removes the water molecules physi and chemi-sorbed on the MEMS assemblies, which deteriorate the packaged environment. The purpose of this study is to develop a metal multilayer that enables both the packaging after degassing at 200 °C and the absorption of residual gas at higher temperatures. The diffusion of Ti atoms can be controlled by fabricating a Pt barrier layer between the Au and Ti layers. A thick Pt layer enables bonding after degassing by preventing the diffusion of Ti during degassing. However, the gas absorption process requires a moderate thickness of the Pt layer because the Ti atoms should reach the surface at high temperatures. In this study, the packaging using thin Au/Pt/Ti multilayers were performed for the advanced MEMS packaging process.For the fabrication of packaged environments, a Si substrate with cavities was bonded with a flat Si substrate using the Au/Pt/Ti layers, as illustrated in Fig. 1. They were thermally oxidized before the bonding procedures. Firstly, the substrates were metalized with Au/Pt/Ti layers of 3/5/40 nm in thickness. The substrates were annealed at 200 °C under vacuum conditions for degassing. Immediately after degassing, the Au surfaces were brought in contact and pressed for the bond formation. Figure 2 shows the mapping of the interfacial gaps observed using a scanning acoustic microscope. Ultrasonic waves reflected in the bright areas, indicating the presence of unbonded areas at the interface. The bright square-shaped regions were due to the packaged areas. While particles on the surface were observed as tiny round voids, there was no leak path for the packages.For the absorption of residual gas molecules, the bonded specimens were annealed at 450 °C for 180 min. Figure 3 depicts the X-ray photoelectron spectra obtained from the inner surface of the annealed package. While the Ti atoms were absent on the surface before the high-temperature annealing step, Ti compounds were present after the high-temperature annealing. This is indicated that the Ti diffused through the Au and Pt layers and reacted with the residual gas molecules on the surface.These results suggested that the 3/5/40-nm-thick Au/Pt/Ti layers can form direct bonding after degassing and also absorb residual gas molecules in the package. We expect that this packaging technique would contribute to future MEMS manufacturing because high-vacuum sealing can be obtained by the simple metal multilayer structure.[1]. Y. Kurashima et al., 45th International Conference on Micro and Nano Engineering, 2019. Figure 1

Corrosion of duplex stainless steel 2205 in hot flue gas environments produced at advanced oxy-fired pressurized fluidized bed combustion plants

The selection of constructional material of flue gas components is crucial for the successful deployment and long-term safe operation of the newly developed oxy-fired pressurized fluidized bed combustion plants. In this study, the corrosion performance of a candidate steel, duplex stainless steel 2205 (DSS 2205) was investigated in simulated flue gas mainly composed of CO2/H2O/O2/N2/SO2/HCl with a total pressure of 1.50–1.64 MPa at 270−320 °C. The oxidation kinetics of DSS 2205 followed parabolic law, and the formed surface oxide was a double-layer structure with outer Fe-rich oxide and inner Cr-rich oxide. Besides general oxidation, SO2 and HCl-induced pitting also occurred. Increasing temperature led to enhanced general oxidation and accelerated pitting. Extending exposure duration resulted in increased pit density, but did not noticeably affect the maximum pit depth. These results indicate that the steel is a promising candidate for further pilot- and industrial-scale assessments.

Measurement and Evaluation of Shaft Torsional Vibrations Using Shaft Instantaneous Angular Velocity

Online evaluation of possible failures of a turbine is a key factor for a successful long-term turbine operation. Fluctuations of generator air-gap torque, caused for example by nonstationary conditions of electrical power grid, influence shaft torsional vibrations as well as rotating blades vibrations. Symptoms of shaft torsional vibrations are not measurable by normally used relative shaft vibrations sensors, so special measurement must be used. The direct consequence of shaft torsional vibrations is local acceleration or deceleration of shaft circumference when it is measured by a stationary sensor. This paper deals with a measurement method using an optical probe measuring the passage of black and white stripes of a zebra tape, which is stuck on the rotor. The shaft torsional vibrations manifest themselves as a phase modulation of the optical probe output signal, so the sampling rate influence the achievable resolution of the calculated shaft vibrations. The presented method for the calculation of the shaft torsional vibrations is based on the evaluation of shaft instantaneous angular velocity. The advantage of this method is a direct compensation of possible nonregular geometry of the zebra tape. The analysis of shaft torsional vibrations evaluation using this method is supplemented by two case studies from the authors' current work.

Glutamate as sole carbon source for enhanced biological phosphorus removal

Enhanced Biological Phosphorus Removal (EBPR) is based on the enrichment of sludge in polyphosphate accumulating organisms (PAO). Candidatus Accumulibacter is the bacterial community member most commonly identified as PAO in EBPR systems when volatile fatty acids (VFA) are the carbon source. However, it is necessary to understand the role of non-Accumulibacter PAO in the case of wastewater with low VFA content. This work shows the first successful long-term operation of an EBPR system with glutamate as sole carbon and nitrogen source, resulting in the enrichment of sludge in the genus Thiothrix (37%), the family Comamonadaceae (15.6%) and Accumulibacter (7.7%). The enrichment was performed in an anaerobic/anoxic/oxic (A2/O) continuous pilot plant, obtaining stable biological N and P removal. This microbial community performed anaerobic P-release with only 18–29% of the observed PHA storage in Accumulibacter-enriched sludge and with slight glycogen storage instead of consumption, indicating the involvement of other carbon storage routes not related to PHA and glycogen. Thiothrix could be clearly involved in P-removal because it is able of accumulating Poly-P, probably without PHA synthesis, but with glutamate involvement. On the other hand, Comamonadaceae could participate in degradation of glutamate and denitrification, but its involvement in P-uptake cannot be reliably concluded.

Comparison of different chemical cleaning reagents on fouling recovery in a Self-Forming dynamic membrane bioreactor (SFDMBR)

Abstract Self-forming dynamic membrane bioreactor (SFDMBR) using large pore size (>5 μm) membrane material is regarded as a cost-effective technology with less fouling and high permeate flux. However, no successful long-term operation without chemical cleaning is achieved. Therefore, an optimum chemical cleaning reagent needs to be explored with the understanding of foulants structure. This study compared the cleaning effects of three typical chemical cleaning reagents, i.e. sodium hydroxide (NaOH), sodium hypochlorite (NaClO), and sodium dodecyl sulfate (SDS), using a lab-scale SFDMBR. NaClO is identified as the most effective cleaning reagent in view of its trans-membrane pressure (TMP) reduction and permeability recovery efficiency. NaClO could achieve 99.0% of permeability recovery and full TMP reduction, while NaOH and SDS could only recover 87.7% and 76.5% of initial permeability and showed limited efficiency in TMP reduction, although all three reagents can achieve over 70% of extracellular polymeric substances (EPSs). The major foulant of the SFDMBR was a complex mixture of sludge flocs with EPS. NaClO cleaning can largely remove the flocs and EPS by oxidization effects while NaOH and SDS were only effective in EPS removal, which explained why NaClO cleaning showed the best performance. β-polysaccharide attached on the mesh fibers and acted as the binding substance between the foulants and mesh fibers is the main reason for irremovable inner pore fouling, which only could be significantly removed with NaClO cleaning. These results well explain the difference of filtration performance after three types of chemical cleaning.

A method to monitor and measure the water transparency in LHAASO-WCDA using cosmic muon signals**Supported by U1332201, U1532258 and NSFC (11375224, 11675187)

The Large High Altitude Air Shower Observatory (LHAASO) is to be built at Daocheng, Sichuan Province, China. As one of the major components of the LHAASO project, a Water Cherenkov Detector Array (WCDA), with an area of 78000 m2, contains 350000 tons of purified water. The water transparency and its stability are critical for successful long-term operation of this project. To gain full knowledge of the water Cherenkov technique and investigate the engineering issues, a 9-cell detector array has been built at the Yangbajing site, Tibet, China. With the help of the distribution of single cosmic muon signals, the monitoring and measurement of water transparency are studied. The results show that a precision of several percent can be obtained for the attenuation length measurement, which satisfies the requirements of the experiment. In the near future, this method could be applied to the LHAASO-WCDA project.

Novel Syntrophic Populations Dominate an Ammonia-Tolerant Methanogenic Microbiome.

Biogas reactors operating with protein-rich substrates have high methane potential and industrial value; however, they are highly susceptible to process failure because of the accumulation of ammonia. High ammonia levels cause a decline in acetate-utilizing methanogens and instead promote the conversion of acetate via a two-step mechanism involving syntrophic acetate oxidation (SAO) to H2 and CO2, followed by hydrogenotrophic methanogenesis. Despite the key role of syntrophic acetate-oxidizing bacteria (SAOB), only a few culturable representatives have been characterized. Here we show that the microbiome of a commercial, ammonia-tolerant biogas reactor harbors a deeply branched, uncultured phylotype (unFirm_1) accounting for approximately 5% of the 16S rRNA gene inventory and sharing 88% 16S rRNA gene identity with its closest characterized relative. Reconstructed genome and quantitative metaproteomic analyses imply unFirm_1's metabolic dominance and SAO capabilities, whereby the key enzymes required for acetate oxidation are among the most highly detected in the reactor microbiome. While culturable SAOB were identified in genomic analyses of the reactor, their limited proteomic representation suggests that unFirm_1 plays an important role in channeling acetate toward methane. Notably, unFirm_1-like populations were found in other high-ammonia biogas installations, conjecturing a broader importance for this novel clade of SAOB in anaerobic fermentations. IMPORTANCE The microbial production of methane or "biogas" is an attractive renewable energy technology that can recycle organic waste into biofuel. Biogas reactors operating with protein-rich substrates such as household municipal or agricultural wastes have significant industrial and societal value; however, they are highly unstable and frequently collapse due to the accumulation of ammonia. We report the discovery of a novel uncultured phylotype (unFirm_1) that is highly detectable in metaproteomic data generated from an ammonia-tolerant commercial reactor. Importantly, unFirm_1 is proposed to perform a key metabolic step in biogas microbiomes, whereby it syntrophically oxidizes acetate to hydrogen and carbon dioxide, which methanogens then covert to methane. Only very few culturable syntrophic acetate-oxidizing bacteria have been described, and all were detected at low in situ levels compared to unFirm_1. Broader comparisons produced the hypothesis that unFirm_1 is a key mediator toward the successful long-term stable operation of biogas production using protein-rich substrates.

METHODIQA - Development of a Quality Assurance Methodology for Renewable Heat Systems Based on Intelligent Operational Monitoring

The continuous monitoring and analysis of renewable heat installations is the key for successful long-term plant operation. Since an ongoing detailed monitoring process requires high efforts regarding time and human resources, it is too costly and thus not feasible for smaller plants. The METHODIQA project aims at developing the technical and scientific methodology for a quality assurance system based on intelligent operational monitoring which is cost-effective, meets high quality standards and exhibits a high degree of automation. The core parts of the methodology comprise the data acquisition and data pre-processing, the analysis and diagnostics based on mathematical algorithms as well as an automated reporting and notification system. METHOTHIQA is not fully automated yet, since the required plant modeling and internal data structure are currently still under development. Nevertheless, the system is functional and a proof-of-concept could be achieved: a broad range of algorithms have already been implemented, and each algorithm is assigned to several graphical outputs (charts), aiming at a straightforward, intuitive interpretation of the algorithms’ results. Example algorithms include the calculation of basic key figures and several complex algorithms which e.g. calculate the collector field efficiency based on intervals with stationary operating conditions. First results generated from the METHODIQA system are promising and indicate the high potential of the methodology. This paper focuses on the methodic approach chosen in the data pre-processing and on the algorithm based analyses.

Autotrophic hydrogen-producing biofilm growth sustained by a cathode as the sole electron and energy source

It is still unclear whether autotrophic microbial biocathode biofilms are able to self-regenerate under purely cathodic conditions without any external electron or organic carbon sources. Here we report on the successful development and long-term operation of an autotrophic biocathode whereby an electroactive biofilm was able to grow and sustain itself with CO2 as a sole carbon source and using the cathode as electron source, with H2 as sole product. From a small inoculum of 15mgCOD (in 250mL), containing 30.3% Archaea, the bioelectrochemical system operating at −0.5V vs. SHE enabled an estimated biofilm growth of 300mg as COD over a period of 276days. A dramatic change in the microbial population was observed during this period with Archaea disappearing completely (<0.1% of population). The predominant phyla enriched were Proteobacteria (57.3%), Firmicutes (12.4%), Bacteroidetes (11.6%) and Actinobacteria (1.1%). Up to 9.2LH2m−2day−1 (1.88Am−2) was achieved when the cathode potential was decreased to −0.75V vs. SHE. This study demonstrates that purely autotrophic biofilm growth coupled to proton reduction to hydrogen alone can be sustained with a cathode as the sole electron source, while avoiding the development of H2-consuming microorganisms such as methanogens and acetogens.

Geophysical Investigation of Seepage Beneath an Earthen Dam

A hydrogeophysical survey is performed at small earthen dam that overlies a confined aquifer. The structure of the dam has not shown evidence of anomalous seepage internally or through the foundation prior to the survey. However, the surface topography is mounded in a localized zone 150 m downstream, and groundwater discharges from this zone periodically when the reservoir storage is maximum. We use self-potential and electrical resistivity tomography surveys with seismic refraction tomography to (1) determine what underlying hydrogeologic factors, if any, have contributed to the successful long-term operation of the dam without apparent indicators of anomalous seepage through its core and foundation; and (2) investigate the hydraulic connection between the reservoir and the seepage zone to determine whether there exists a potential for this success to be undermined. Geophysical data are informed by hydraulic and geotechnical borehole data. Seismic refraction tomography is performed to determine the geometry of the phreatic surface. The hydro-stratigraphy is mapped with the resistivity data and groundwater flow patterns are determined with self-potential data. A self-potential model is constructed to represent a perpendicular profile extending out from the maximum cross-section of the dam, and self-potential data are inverted to recover the groundwater velocity field. The groundwater flow pattern through the aquifer is controlled by the bedrock topography and a preferential flow pathway exists beneath the dam. It corresponds to a sandy-gravel layer connecting the reservoir to the downstream seepage zone.

Technical and operational feasibility of psychrophilic anaerobic digestion biotechnology for processing ammonia-rich waste

Ammonia nitrogen plays a critical role in the performance and stability of anaerobic digestion (AD) of ammonia rich wastes like animal manure. Nevertheless, inhibition due to high ammonia remains an acute limitation in AD process. A successful long-term operation of AD process at high ammonia (>5gN/L) is limited. This study focused on validating technical feasibility of psychrophilic AD in sequencing batch reactor (PADSBR) to treat swine manure spiked with NH4Cl up to 8.2±0.3gN/L, as a representative of N-rich waste. CODt, CODs, VS removals of 86±3, 82±2 and 73±3% were attained at an OLR of 3gCOD/L.d, respectively. High-ammonia had no effect on methane yields (0.23±0.04L CH4/gTCODfed) and comparable to that of control reactors, which fed with raw swine manure alone (5.5gN/L). Longer solids/hydraulic retention times in PADSBRs enhanced biomass acclimation even at high-ammonia. Thus VFA, an indicator for process stability, did not accumulate in PADSBR. Further investigation is essential to establish the maximum concentrations of TKN and free ammonia that the PADSBR can sustain.