Rapid Start-up Research Articles

Aerobic granular sludge enhances start-up and granulation in single-stage partial nitritation anammox granular sludge systems: Performance, mechanism, and shifts in bacterial communities

The rapid start-up and granulation of a single-stage partial nitritation anammox granular sludge (PN/AnGS) system under limited seed sludge conditions is crucial for its practical application. This study proposed an aerobic granular sludge (AGS) − based strategy, enhanced the enrichment of anammox bacteria (AnAOB), and shortened the start-up time of PN/AnGS system by 20.5%. In addition, the inoculation of AGS can ensure the stable operation of the system during the selective sludge discharge to washout the flocs. Microbial community structure, particle size distribution, morphology results showed that niche shift was the key to promote the enrichment of AnAOB and AGS played a decisive role in the particle characteristics of PN/AnGS. Since AGS can be directly obtained from full-scale AGS wastewater treatment plants, integrating PN/AnGS with AGS processes can transition wastewater treatment from a “linear economy” to a “circular economy”, enhancing nitrogen removal efficiency and delivering significant economic and environmental benefits.

Synergistic effects of organic matter degrading and electroactive biofilms for rapid startup of sediment microbial fuel cells: From laboratory scale to in situ application

Synergistic effects of organic matter degrading and electroactive biofilms for rapid startup of sediment microbial fuel cells: From laboratory scale to in situ application

Internal temperature prediction and control strategy design of anode-supported solid oxide fuel cell for hot start-up process

Anode-supported solid oxide fuel cell (SOFC) has a high energy efficiency while suffering from a poor transient performance such as start-up. In this study, a model-based design method is proposed to develop a suitable strategy for the rapid hot start-up of anode-supported SOFC (AS-SOFC). First, a mathematical model is established for a 25-kW SOFC system and the internal temperature is predicted. Subsequently, three different strategies are compared during hot start-up process. The results indicate that the positive-electrolyte-negative (PEN) temperature variation magnitude is 50 K and the response time is 1300 s when the hydrogen and the air flow rates are fixed for the afterburner and the cathode. If a PID controller is employed to regulate the flow rate of H2 to the afterburner, the PEN temperature variation magnitude decreases to 16 K with a shorter response time of 158 s. When increasing the air flow rate synchronously, the PEN temperature variation magnitude is merely 8 K, reduced by 84 % and 50 % compared with the previous strategies. Additionally, the gas temperature exiting from the afterburner declines significantly for the third control strategy. Thus, the lifetime and reliability of AS-SOFC is enhanced. The results provide a reference for the SOFC systems control such as domestic combined heat and power (CHP) and mobile applications.

Pilot microbial electrolysis cell closes the hydrogen loop for hydrothermal wet waste conversion to jet fuel

The global shift toward net-zero emissions necessitates resource recovery from wet waste. In this study, we demonstrate the first feasibility of combining pilot-scale microbial electrolytic cells (MECs) with hydrothermal liquefaction (HTL) for simultaneous post-hydrothermal liquefaction wastewater (PHW) treatment and efficient hydrogen (H₂) production to meet biocrude upgrading requirements. Long-term single reactor operation revealed that fixed anode potential enabled rapid startup, and low catholyte pH and high salinity were effective in suppression of cathodic methanogenesis and acetogenesis – resulting in high current density of 16.6 A m−2 and 9.3 A m−2 when feeding synthetic wastewater and PHW respectively. Additionally, the anode biofilm exhibited spatial variations in response to local environmental conditions. Onsite parallel or serial operations of multiple MECs showed good performance using actual PHW with a record-high H2 production rate of 0.5 L LR day−1 for MEC over 10 liters scale, and the optimal chemical oxygen demand (COD)-to-H2 yield reached 0.127 kg-H2 per kg-COD, supporting a self-sufficient, closed-loop upgrade to jet fuel.

Efficient Data Exchange between WebAssembly Modules

In the past two decades, there has been a noticeable decoupling of machines and operating systems. In this context, WebAssembly has emerged as a promising alternative to traditional virtual machines. Originally designed for execution in web browsers, it has expanded to executing code in restricted and secure environments, and it stands out for its rapid startup, small footprint, and portability. However, WebAssembly presents significant challenges in data transfer and the management of interactions with the module. Its specification requires each module to have its own memory, resulting in a “share-nothing” architecture. This restriction, combined with the limitations of importing and exporting functions that only handle numerical values, and the absence of an application binary interface (ABI) for sharing more complex data structures, leads to efficiency problems; these are exacerbated by the variety of programming languages that can be compiled and executed in the same environment. To address this inefficiency, the Karmem was designed and developed. It includes a new interface description language (IDL) aimed at facilitating the definition of data, functions, and relationships between modules. Additionally, a proprietary protocol—an optimized ABI for efficient data reading and minimal decoding cost—was created. A code generator capable of producing code for various programming languages was also conceived, ensuring harmonious interaction with the ABI and the foreign function interface. Finally, the compact runtime of Karmem, built atop a WebAssembly runtime, enables communication between modules and shared memory. Results of the experiments conducted show that Karmem represents an innovation in data communication for WASM in multiple environments and demonstrates the ability to overcome challenges of efficiency and interoperability.

Achieving rapid start-up and efficient nitrogen removal of partial-denitrification/anammox process using organic matter in brewery wastewater as carbon source

ABSTRACT To find a cost-efficient carbon source for the partial denitrification/anaerobic ammonium oxidation (anammox) (PD/A) process, the practicability of using the organic matter contained in brewery wastewater as carbon source was investigated. Quick self-enrichment of denitrifying bacteria was achieved by supplying brewery wastewater as organic carbon source and using the mature anammox sludge as the seeding sludge. The PD/A process was successfully established after 33-day operation and then the average total nitrogen removal efficiency reached 92.29% when the influent CODCr: NO3 −-N: NH4 +-N ratio was around 2.5: 1.0: 0.67. The relative abundance of Thauera increased from 0.03% in the seeding sludge to 54.29% on day 110, whereas Candidatus brocadia decreased from 30.66% to 2.08%. The metagenomic analysis indicated that the sludge on day 110 contained more nar and napA (total of 41.24%) than nirK and nirS (total of 11.93%). Thus NO2 −-N was accumulated efficiently in the process of denitrification and sufficient NO2 −-N was supplied for anammox bacteria in the PD/A process. Using brewery wastewater as carbon source not only saved the cost of nitrogen removal but also converted waste into resource and reduced the treatment expense of brewery wastewater.

An enhanced maximum power point tracking and voltage control for proton exchange membrane fuel cell using predictive model control techniques

Proton Exchange Membrane Fuel Cells serve as sustainable devices for converting renewable energy sources into electricity, offering advantages such as rapid startup, high power density, and operation at low temperatures. They are highly efficient and environmentally friendly energy sources, yet their non-linear output characteristics under variable conditions present challenges in maximizing power output. Furthermore, they generates direct current, while many electrical devices rely on alternating current. This research addresses the necessity of enhancing the performance and efficiency through the development of an advanced maximum power point tracking technique and voltage control strategy. A modified finite-control-set model predictive control technique is proposed for both maximum power point tracking and voltage control. Specifically, a finite-control-set model predictive control technique approach is employed to modulate the switching signal for both the DC-DC boost converter and the DC-AC inverter. The DC-DC boost converter step up the fuel cell output voltage to the desired level, ensuring it reaches the maximum power point, and a DC-AC inverter to convert the direct current voltage to a pure sinusoidal alternating waveform. The investigation demonstrates the effectiveness of the proposed method in achieving its objectives. The proposed maximum power point tracking technique accuracy achieved the maximum power with a rate of 97 % with excellent respond time within 7 ms. For alternating current power, only less than 1.5 % of total harmonic distortion is recorded. The study evaluates the control scheme under robust operating conditions, demonstrating its effectiveness in optimizing PEMFC output and providing high-quality AC voltage.

Optimize the ratio of immobilized gel materials to improve gel performance and oxygen mass transfer rate: Achieve rapid start-up and efficient and stable operation of partial nitration

A gel filler with diatomaceous earth, activated carbon, and CaCO3 compounded with polyvinyl alcohol was prepared and optimized. Rapid start-up and efficient and stable operation of partial nitrification (PN) was achieved by immobilization of conventional activated sludge. The results showed that the proper material proportion synergistically improved the performance and oxygen mass transfer rate of the gel. The continuous flow reactor was operated for 10d to successfully start PN, and the maximum ammonia oxidation rate of this filler was 58.30 mg·(L·h)−1 during the stable operation, and the nitrite accumulation rate was maintained above 90 %. However, due to the greater mass transfer resistance of unoptimized fillers, more dissolved oxygen waste and nitrogen loss were caused, resulting in delayed expression of biological activity. Based on the kinetic characterization of ammonia-oxidizing bacteria (AOB) within the filler and high-throughput sequencing, it was demonstrated that the rapid start-up and efficient and stable operation of the PN system was due to the highly oxygenophilic and community-dominant position of AOB within this filler. This study provides new options and insights at the level of immobilization technology for the realization and efficient and stable operation of PN.

Innovative approaches for enhanced nutrient (N and P) removal and biosecurity in marine recirculating aquaculture systems using biofloc and ultrafiltration combined systems

Marine recirculating aquaculture systems (marine RAS) are increasingly utilized for their high productivity and minimal environmental impact. However, effective nutrient management and biosecurity measures remain crucial for sustainable operation of marine RAS. This study successfully established a simultaneous nitrification and denitrification (SND) process using a biofloc technology (BFT)–ultrafiltration (UF) combined approach. A stable autotrophic marine nitrification system was rapidly initiated within 23 days using a ceramic ring (CR)–granular activated carbon (GAC)–UF process (CGUF), followed by the substitution of polyhydroxyalkanoates (PHA) for GAC filter to achieve rapid start-up of SND in 24 h (CG/PUF). Soluble reactive phosphate (SRP) was removed in-situ via biofloc adsorption. The co-existence of ammonia-oxidizing archaea (Candidatus_Nitrosopumilus) and denitrifying bacteria (Stenotrophomonas, Ruegeria and Ilumatobacter) synergistic promoted the SND start-up in CG/PUF process. Stenotrophomonas emerged as the keystone species which closely linked to amoA/B/C, hao and nosZ genes (p < 0.05). The CG/PUF process effectively enhanced the biosecurity of marine RAS, with 100 % elimination of potential pathogens (Vibrio and Tenacibaculum). UF membrane could maintain fluxes at 15 L∙ m−2∙ h−1 (LMH) for 180 days, with a 2-day intermittent hydraulic flushing keeping transmembrane pressure below 50 kPa. These findings provide insights for broader application of BFT–UF combined process in marine RAS.

Optimization of hydrogen production in multi-Electrolyzer systems: A novel control strategy for enhanced renewable energy utilization and Electrolyzer lifespan

In large-scale water electrolytic hydrogen production system based on renewable energy, the allocation strategy of hydrogen production power among multi-electrolyzers plays a critical role in the efficiency of renewable energy utilization and the quantity of hydrogen production, given a fixed power output from renewable energy sources. This paper considers the minimum hydrogen production power constraint of electrolyzer and proposes a novel control strategy for multi-electrolyzers. The operational phase of multi-electrolyzers is divided into two distinct phases: 1) the rapid start-up phase; 2) the equal power allocation phase. During the rapid start-up phase, by reducing the power of electrolyzer that has reached its rated power to a predetermined level and using this saved power to start another electrolyzer, this strategy ensures that electrolyzers can proactively and quickly exceed the minimum operational power threshold. Upon the activation of all electrolyzers, the system enters second phase, wherein the power is evenly allocated among all electrolyzers. Besides, this strategy employs a priority scheduling method to ensure the uniformity of operating times across all electrolyzers. Compared to the existing three control strategies, this proposed strategy demonstrates significant advantages in minimizing unused wind energy and optimizing the lifespan of electrolyzers. The effectiveness of proposed strategy is validated by the simulation result.

Rapid start-up of mainstream partial denitrification /anammox and enhanced nitrogen removal through inoculation of precultured biofilm for treating low-strength municipal sewage

This study investigated the rapid start-up of mainstream partial denitrification coupled with anammox (PD/A) and nitrogen removal performance by inoculating precultured PD/A biofilm. The results showed mainstream PD/A in the anaerobic-anoxic-aerobic (A2O) process was rapidly established within 30 days. Nitrogen removal efficiency (NRE) improved by 23.8 % contrasted to the traditional A2O process. The mass balance showed that anammox contribution to total nitrogen (TN) removal were maintained at 37.9 %∼55.7 %, and reducing hydraulic retention time (HRT) strengthened simultaneously denitrification and anammox activity. The microbial community showed that the dominant bacteria such as denitrifying bacteria (DNBs) and glycogen accumulating organisms (GAOs) both in biofilm and flocculent sludge (floc), integrating with anammox bacteria (AnAOB) in biofilm might lead to enhanced nitrogen removal. Overall, this study offered a fast start-up strategy of mainstream PD/A with enhanced nitrogen removal, which are valuable for upgradation and renovation of existed municipal wastewater treatment plants (WWTPs).

Investigation on the Influence of Thermal Inertia on the Dynamic Characteristics of a Gas Turbine

In mini-grids and marine-isolated grids, power generation gas turbines are subjected to rapid start-up, shutdown, and acceleration/deceleration. This sudden load change can pose a significant impact on the power grid, severely affecting the operational characteristics of gas turbines. To understand the dynamic characteristics of the gas turbine in the transitional processes, this testing takes twin-shaft medium-sized power generation gas turbines as the test object, and goes through the process of startup, acceleration, deceleration, acceleration, shutdown in one hour, and repeats this process 40 times continuously. With fuel flow as the control parameter and power turbine outlet temperature and high-pressure turbine speed as the controlled parameters, the parameter response rate of the gas turbine under various transition processes is analyzed and the effect of thermal inertia on the gas turbine mass temperature as well as speed is studied. Research findings: During the transition processes, the gas temperature exhibited an axial gradient distribution in the channel. In both the acceleration and deceleration processes, the working fluid temperature gradually decreased along the flow direction. And thermal inertia posed different extents of impact on the dynamic characteristics of the gas turbine under different transitional processes. In the same transition process, the impacts of thermal inertia on the response speeds of temperature and rotational speed varied. The results of this study help to more accurately predict the operating state of the gas turbine during the transition process and lay the foundation for the dynamic simulation model of the non-adiabatic gas turbine.

Electrochemical Conversion of CO2 to Fuels and Useful Chemicals over Metal Supported Solid Oxide Electrolyzers

Electrochemical conversion of CO2 and H2O to fuels and chemicals provides a promising approach to simultaneously mitigate greenhouse emission and store surplus energy, which reduces electricity network variation due to increased intermittent renewable energy (such as solar and wind) utilization. Metal supported solid oxide electrolyzers (MS-SOEs) developed at Lawrence Berkeley National Laboratory provide advantages of rapid start-up, mechanical ruggedness, redox tolerance, dynamic operation, and low-cost materials. A relatively high operating temperature range of 600 to 750°C promotes energy efficiency and allows utilization of thermal energy such as steam.In this work, efficient and stable catalysts developed at the University of South Carolina have been infiltrated in the symmetrical and porous MS-SOE architecture. The phase purity has been analyzed by X-day diffraction. The morphologies of these infiltrated and posttest catalysts have been examined by scanning electron microscopy. Optimization of cell structure, processing temperature, cell voltage, and catalyst infiltration cycles for better cell performance will be presented. The stability of MS-SOEs has been evaluated during continuous operation for >200 hours. The cell degradation mechanisms revealed by electrochemical impedance spectroscopy and high-resolution scanning electron microscopy techniques will be presented.In addition to pure CO2 electrochemical conversion, effects of additional water and hydrogen in CO2 feedstock will be analyzed. Faradic efficiency and chemical selectivity calculated from gas chromatograph and electrochemical analyses will be presented.

Full-scale study on high-rate low-temperature anaerobic digestion of agro-food wastewater: process performances and microbial community.

The fast-growing global population has led to a substantial increase in food production, which generates large volumes of wastewater during the process. Despite most industrial wastewater being discharged at lower ambient temperatures (<20 °C), majority of the high-rate anaerobic reactors are operated at mesophilic temperatures (>30 °C). High-rate low-temperature anaerobic digestion (LtAD) has proven successful in treating industrial wastewater both at laboratory and pilot scales, boasting efficient organic removal and biogas production. In this study, we demonstrated the feasibility of two full-scale high-rate LtAD bioreactors treating meat processing and dairy wastewater, and the microbial communities in both reactors were examined. Both reactors exhibited rapid start-up, achieving considerable chemical oxygen demand (COD) removal efficiencies (total COD removal >80%) and generating high-quality biogas (CH4% in biogas >75%). Long-term operations (6-12 months) underscored the robustness of LtAD bioreactors even during winter periods (average temperature <12 °C), as evidenced by sustained high COD removal rates (total COD removal >80%). The stable performance was underpinned by a resilient microbial community comprising active acetoclastic methanogens, hydrolytic, and fermentative bacteria. These findings underscore the feasibility of high-rate low-temperature anaerobic wastewater treatment, offering promising solutions to the zero-emission wastewater treatment challenge.

Rapid start-up and stable operation of pilot scale denitrification-partial nitritation/anammox process for treating electroplating tail wastewater

This study explored a novel economical and efficient process for treating actual low-ammonia nitrogen electroplating tail wastewater. A pilot scale system of denitrification-partial nitrification/anaerobic ammonium oxidation (DN-PN/A) was constructed and operated for 190 days. The partial nitrification (PN) reactor, filled with zeolite, increased free ammonia concentration beyond the nitrite oxidizing bacteria threshold and successfully supplied NO2−-N, with nitrite accumulation rate exceeding 90 %. Over 109 days, the total nitrogen removal rate achieved was 80.2 ± 7.41 %, and the chemical oxygen demand removal rate reached 79.68 ± 9.53 %. The dominant functional bacteria were Nitrosomonas (5.45 %) and Candidatus Anammoxoglobus (28.84 %) in PN reactor and anaerobic ammonium oxidation (Anammox) reactor. This process, characterized by rapid start-up, strong shock resistance, and low cost, alleviates the pressure of ammonium pollution control, promotes the sustainable development of the electroplating industry and has the potential for application in the treatment of other industrial wastewater.

Enhanced sludge granulation and stable performance of an anammox expanded granular sludge bed (EGSB) reactor through the utilization of hydroxyapatite (HAP) particles

The reuse of hydroxyapatite particles (HAPs) as a granulation activator for anammox sludge was explored to address the remaining issues of time-consuming and unstable granular structure in anammox granulation. During the granulation, nitrogen removal capacity from 2.8 to 13.7 gN/L/d was obtained within 193 days, accompanied by an enhancement in bio-activity from 0.23 to 0.52 gN/gVSS/d. HAPs and anammox microorganisms coupled well to aggregate into granules for denser biomass, higher settleability, and stronger mechanical properties, which effectively improved the biomass retention capacity and structural strength of the sludge system. A skeleton structure formed by the HAPs was characterized during the transformation of the granules, playing a crucial role in strengthening the stability of the sludge. The intermediate processes of granulation were thus clarified to propose an evolutionary pathway for anammox-HAP granules. The pre-addition of HAPs is conducive to achieving faster anammox granulation and rapid process start-up for high-strength wastewater treatment.

Construction of wide-temperature-range proton exchange membrane by regulating proton transfer channels based on phosphate-functionalized carbon nanotubes

Phosphoric acid (PA) doped polybenzimidazole (PBI) high-temperature proton exchange membrane is favored because it can achieve faster proton transfer at 180 °C without additional humidification. However, the PA-PBI membrane is faced with slow PA proton conduction kinetics below 100 °C, and failing rapid start-up of fuel cells. Herein, carbon nanotubes functionalized with phosphate groups (P-CNT) and sulfonated poly [2,2'-(p-hydroxydibenzene)-5,5′-benzimidazole] (SOPBI) composite membranes are prepared as proton exchange membranes with wide temperature range (40–180 °C). Based on the regulation of monophosphate and bisphosphate groups on P-CNT, the bisphosphate group can strengthen the vehicular mechanism of proton transport by accelerating the formation and diffusion of H3O+ at low temperature/high humidity, and the Grotthuss mechanism of proton transport by constructing dense hydrogen bond network at high temperature/low humidity. The 2P-CNT(6 %)/SOPBI composite membrane shows excellent proton conductivity (131.8 mS cm−1 at 80 °C/90%RH, 170.5 mS cm−1 at 180 °C/0%RH) and peak power density (378 mW cm−2 at 80 °C/100 % RH, 531 mW cm−2 at 160 °C/0 % RH) under wide temperature conditions, surpassing SOPBI membrane and other composite membranes. Furthermore, the 2P-CNT(6 %)/SOPBI composite membrane exhibits high proton conduction and fuel cell stability at both 80 °C/100 % RH and 160 °C/0 % RH.

Rapid Start-up of Continuous Autotrophic Nitrogen Removal Reactor by Hybrid-inoculating PN and PN/A Granular Sludges

The rapid cultivation of partial nitritation/ANAMMOX （PN/A） granular sludge in a continuous-flow mode is one of the key technologies for efficient biological nitrogen removal in domestic wastewater treatment. Compared with that in PN/A granular sludge, PN granular sludge demonstrates a shorter incubation period and suitability for batch culture. It is also a good carrier for enriching ANAMMOX （AMX） bacteria. In this study, we established a continuous-flow autotrophic nitrogen removal process in three continuously stirred tank reactors （CSTR） （R1-R3） by hybrid-inoculating PN/A and PN granular sludge at the mass ratios of 3∶1, 1∶1, and 1∶3, respectively. By implementing high ammonium nitrogen loading and short hydraulic retention time, continuous autotrophic nitrogen removal processes were successfully started up in the three CSTRs. The results showed that compared with that of R1 and R2, R3 had a longer start-up time but a similar steady-state nitrogen removal performance. The total nitrogen removal load of R3 could be more than 2.6 kg·（m3·d）-1. Intriguingly, the inoculated PN granular sludge served as a precursor for PN/A granular sludge cultivation. This approach facilitated the enrichment of anaerobic ammonia-oxidizing bacteria （AMX） by introducing abundant ammonium-oxidizing bacteria （AOB） and nitrite nitrogen substrates into the CSTR. According to the results of high-throughput sequencing, the microbial abundance and diversity of the mature granules in R1-R3 were significantly higher than those of the inoculation sludge. AOB （genus Nitrosomonas）, AMX （genera Candidatus Kuenenia and Candidatus Brocadia）, and symbiotic heterotrophs, such as Chloroflexi, Bacteroidetes, and Chlorobi, drove the autotrophic nitrogen removal process and maintained the stability of the granular structure. In summary, a novel start-up strategy of hybrid-inoculating granular sludge was provided for a continuous-flow autotrophic nitrogen removal in engineering application.

Rapid start-up of carbon-free H2 production by ammonia oxidative decomposition over Co/Ce0.5Zr0.5O2 with microwave irradiation

Hydrogen is a promising combustion improver for use with ammonia fuels, but a cost-effective method for easily producing hydrogen from ammonia at a high rate has yet to be developed. Here, we show that microwave irradiation instantly triggers oxidative decomposition of ammonia over a Co/Ce0.5Zr0.5O2 catalyst to produce hydrogen at a high rate. The microwave irradiation rapidly heats the inside of the catalyst from room temperature to the catalytic auto-ignition temperature of ammonia, thus initiating exothermic oxidative decomposition of ammonia to produce hydrogen. This method provides a highly efficient means of producing hydrogen for potential use in a carbon-free, ammonia-fueled power generation process.

E-Learning system application in art entrepreneurship teaching based on multimodal feature fusion and neural network

College student entrepreneurship teams can leverage the advantages of mobile internet resource integration and online collaborative production platforms to easily integrate various resources, thereby achieving rapid start-up and development of entrepreneurial projects. This also makes the threshold for college students to start businesses lower and easier to achieve. This article designs an interactive aesthetic education and entrepreneurship teaching system based on multimodal feature fusion and interactive systems. The core concept of the interactive aesthetic education and entrepreneurship teaching system is multimodal feature fusion and interactive system. Multimodal feature fusion can integrate different teaching resources, so that students can better understand the factors that need to be considered in the entrepreneurial process and practice. Interactive systems can enable closer interaction and communication between students and teachers, thereby better understanding and mastering entrepreneurial knowledge and skills. The design and implementation of a systematic system will help enhance the entrepreneurial ability and quality of college students, help them better understand the entrepreneurial process and factors that need to be considered in practice, and provide entrepreneurial practice reference for students in Chinese universities who have the intention of designing entrepreneurship.