Anaerobic systems are widely used to treat sulfate-rich industrial wastewater, where competition and cooperation between sulfate-reducing bacteria (SRB) and methanogens determine carbon flux and energy recovery. Reactor configuration and conductive materials (CMs) strongly shape microbial metabolism and electron-transfer pathways in such systems. In this study, eight anaerobic reactors, operated in sequencing batch reactor (SBR) and continuous-flow reactor (CFR) modes, were used to investigate ethanol-driven sulfate reduction and methanogenesis at a COD/sulfate ratio of 8:1, with Fe3O4 or powdered activated carbon as CMs. All reactors maintained stable long-term performance, showing nearly complete ethanol removal (99%), high sulfate reduction (up to 99%), and minimal volatile fatty acid accumulation. Reactor configuration was the primary driver of metabolic behavior. SBRs favored ethanol conversion to propionate and enriched incomplete-oxidizing SRB (IO-SRB), particularly Desulfobulbus. CFRs promoted ethanol oxidation to acetate and sustained efficient substrate conversion despite lower IO-SRB abundance. Without sulfate, IO-SRB in SBRs shifted from sulfate reduction to syntrophic propionate fermentation. In contrast, CFRs enhanced extracellular electron transfer (EET), reflected by higher sludge conductivity and the enrichment of Geobacter and Methanothrix, supporting direct electron transfer-mediated methanogenesis. Fe3O4 further strengthened EET in CFRs, while CMs in SBRs mainly stimulated syntrophic propionate degradation. Overall, sulfate availability, operational mode, and CM type jointly governed carbon-flux partitioning and electron-transfer pathways in sulfate-reducing anaerobic systems.
Smog chambers provide controlled environments for studying atmospheric processes. This study presents the design and characterization of a novel vehicle-mounted dual-reactor smog chamber, capable of simulating atmospheric oxidation processes in both indoor and outdoor settings. Developed at the Guangdong Provincial Academy of Environmental Science, this innovative system consists of two 8 m3 cylindrical fluorinated ethylene propylene Teflon reactors housed in a van semi-trailer. The reactors can independently operate under black lamp irradiation or solar radiation, allowing seamless transitions between controlled laboratory conditions and real-world outdoor scenarios. Comprehensive characterization demonstrates excellent performance in temperature control (within ± 0.5 °C between 25 and 35 °C for indoor experiments), rapid mixing (2-3 min), high light transmission (> 88 % at 300-950 nm) and low wall loss rates for gases (10-5-10-4 min-1) and particles (0.12-0.17 h-1). Parallel experiments in two reactors yield consistent results, confirming the reliability of the system for comparative studies. Validation experiments, including toluene-NOx photochemical oxidation and α-pinene ozonolysis, showed strong agreement with box model simulations, demonstrating the chamber's utility for investigating atmospheric chemical mechanisms and secondary organic aerosol formation. The dual-reactor design, combining mobility and adaptability, enables versatile and high-fidelity simulations of oxidation processes.
The anaerobic membrane bioreactors (AnMBRs) present an efficient method for wastewater treatment, but the membrane fouling poses a primary barrier to sustained, large-scale operation. This study addresses the fouling mitigation in AnMBR by developing bio-based coagulants from microcrystalline cellulose (MCC) and rice straw (RS). The cationic derivatives (cMCC and cRS) were synthesized through a two-step process-periodate oxidation of cellulose, followed by cationization with Girard's reagent T. The resultant cationic celluloses exhibited hydrodynamic diameters of 231 nm (cMCC) and 148 nm (cRS) and zeta potentials of + 38 mV (cMCC) and + 26 mV (cRS). The structure of cationic celluloses was confirmed by 1H NMR and the nitrogen elemental analysis revealed a degree of substitution of 0.6-0.8 and a high cationicity index of 2.98-3.41 mmol/g. A single dose of 5 ppm cMCC and 7 ppm cRS was added at the beginning of a 60-day continuous AnMBR trial. These coagulants effectively neutralized the negative charges on the sludge particles through electrostatic patch interactions. The enlarged flocs (~ 367 μm) reduced pore blocking and formed a loosely bound cake layer, as confirmed by scanning electron microscopy of the membrane surface. With coagulant addition, the permeate flux remained stable for nearly 50 days and the fouling rates declined by almost 37% in the cRS reactor and by 53% in the cMCC reactor, while achieving 92% COD removal efficiency with no adverse impact on the reactor performance. These biomass-derived cationic coagulants offer a non-toxic, eco-friendly alternative to commercial additives to improve membrane performance in AnMBR systems.
Electrochemical degradation of halogenated aromatic compounds typically presents a fundamental trade-off between energy-intensive mineralization and partial dehalogenation, which can yield persistent toxic intermediates. Herein, we introduced a dual-anode electrochemical reactor employing sequential hydroxylation and direct electron transfer (DET) mechanisms for the efficient destruction of chlorinated aromatics coupled with carbon resource recovery. The reactor integrated a Ce-doped tin antimony oxide (Ce-ATO) anode and a defective ATO anode. As a proof of concept, 2,4-dichlorophenoxyacetic acid (2,4-D), a widely produced pesticide, was first converted into 2,4-dichlorophenol via hydroxylation reaction at the Ce-ATO anode. This intermediate subsequently underwent DET at the downstream defective ATO anode, generating organic radicals that underwent radical-radical coupling to form oligomers. The inclusion of a proton exchange membrane into the reactor maintained an acidic microenvironment, which enhanced •OH-mediated oxidation and promoted adsorption. The system achieved over 95% removal of 0.45 mM 2,4-D at a current of 1 mA and a membrane flux of 150 LMH, and a corresponding hydraulic retention time of 0.8 min, with an oligomer recovery rate of 62% obtained at 5 mM 2,4-D under otherwise identical conditions. The recovered oligomers were readily pyrolyzed into microporous carbon with a high surface area (454.47 m2·g-1) and demonstrated excellent adsorption capacity for 4-chlorophenol (217.31 mg·g-1). Furthermore, the system demonstrated robust performance when applied to complex pharmaceutical wastewater. This work offered a sustainable strategy for simultaneous decontamination and resource upcycling in high-salinity wastewater streams.
This paper presents a comprehensive safety analysis of the NuScale Small Modular Reactor, a next-generation nuclear technology. The NuScale design emphasizes enhanced safety, flexibility, and efficiency, achieved through a natural circulation cooling system and robust passive safety functions. The analysis is conducted using the RELAP5/SCDAPSIM3.4 system code for high-fidelity thermal-hydraulic simulations. The first part details the steady-state qualification of the reactor model, a crucial step to establish a reliable baseline for normal operation and subsequent accident analyses. The study confirms the model's accuracy against key design parameters including temperature distributions, coolant flow rates, and system pressure validating its predictive capability. Building upon this qualified model, the second part investigates a severe beyond-design-basis accident scenario. The initiating event is the inadvertent opening of one Reactor Vent Valve, leading to an inside containment Small Break Loss of Coolant Accident. This breach is compounded by the postulated total failure of both the Emergency Core Cooling System and the Decay Heat Removal System, creating a fully unmitigated scenario. The progression of this severe accident, simulated for a duration of  500 s, critically assesses the reactor's passive safety features and inherent resilience. The system's response is analyzed in detail, with key findings showing a consistent behavior comparable to the results of similar scenarios documented in the literature.
This study presents a novel three-zone fibers-based sequencing batch biofilm reactor designed to achieve simultaneous nitrification, denitrification, and phosphorus removal for the treatment of high-strength sewage. Online process control sensors continuously monitored ORP, pH, and DO to provide real-time insight into biological phase transitions within the reactor. A sliding window-based linear regression model was developed and applied as an AI-assisted predictive monitoring framework, enabling accurate forecasting of process control parameters. The SBBR consistently achieved high removal efficiencies for organics and nutrients, producing effluent quality of BOD <3 mg/L, COD <35 mg/L, TN <5 mg/L, and TP ≈1 mg/L, meeting stringent regulatory standards. The AI predictive model demonstrated strong agreement with measured data for all three parameters (pH: R2 = 0.982, RMSE = 0.042; ORP: R2 = 0.996, RMSE = 7.951; DO: R2 = 0.918, RMSE = 0.173), confirming its reliability as a process monitoring tool for identifying biological phase endpoints in real-time. These findings establish the integration of AI-based predictive monitoring with advanced biofilm reactor technology as a practically viable and scientifically sound for high-strength sewage treatment.
Immobilized enzyme reactors operated under flow conditions are promising for process intensification in biocatalytic transformations; however, systematic kinetic comparisons between batch and flow configurations remain limited. Using acetosyringone-mediated malachite green (MG) decolorization as a model reaction, the kinetic behavior of an immobilized laccase system was compared between batch and flow modes. Laccase immobilized on an amino-polyethylene glycol-dimethylacrylamide copolymer resin was applied in batch and packed-tube flow reactors, and MG decolorization was monitored spectrophotometrically. The reaction behavior was analyzed using a pseudo-first-order kinetic model, and rate constants and activation energies were determined for laccase solution, immobilized laccase in batch, and immobilized laccase in flow systems. The packed-bed flow reactor exhibited higher reaction rates, achieving approximately 70% MG decolorization within 6.28min compared with about 78% conversion after 60min in batch operation. Arrhenius analysis revealed a higher apparent activation energy in the flow system, indicating stronger temperature dependence under continuous operation. The immobilized enzyme was reused in repeated batch and flow runs without noticeable performance loss. Overall, these results demonstrate process intensification under continuous-flow operation and provide a quantitative kinetic framework for comparing batch and flow immobilized enzyme systems.
To address the challenges of high-density animal cell culture, this study developed a high-density culture system comprising a single-use bioreactor (SUB) with a nominal volume of 500 mL and a pulsed tangential flow filtration (ITF) unit. The reactor can be configured with two layers of 35 mm diameter impellers-either double Elephant Ear (EE-EE) or Elephant Ear combined with Ribbon (EE-RB). The flow field characteristics were rigorously characterized through CFD simulations (60-240 rpm; 90-480 mL) validated by experimental data. Engineering analysis revealed the system's robust culture environment: [Formula: see text] values ranging from 2 to 15 h-1 (60-180 rpm; 200-400 mL; 30-150 mL/min aeration), [Formula: see text] values from 0.1 to 10 W/m3, and mixing times between 1 and 10 s. Crucially, the system maintains a mild shear environment with an average shear strain rate (SSR) below 25 s-1, fully within the physiological tolerance range for mammalian cells. This low-shear, high-mass-transfer design was validated through perfusion cultures of CHO and HEK293 cells. The system achieved exceptionally high cell densities of 8.32 × 107 cells/mL and 1.17 × 108 cells/mL, respectively, with cell viability consistently exceeding 90%, demonstrating its suitability for high-intensity biopharmaceutical production.
Rapid detection of airborne bacteria is crucial for preventing disease transmission and safeguarding public health. However, conventional methods for bioaerosol collection and detection often rely on complex and expensive equipment with low integration and automation, limiting their use for real-time applications. Herein, a dual-function 3D-printed cyclonic collector/reactor-integrated colorimetric biosensor was innovatively developed for the collection, separation, and detection of airborne bacteria. This platform incorporated a custom-designed wet cyclone, which served as a bioaerosol collector and an immunoassay reactor by utilizing the cyclonic vortex for simultaneous bioaerosol collection and active mixing with immunoreagents. Airborne bacteria were first collected into the phosphate-buffered saline at a flow rate of 12 L/min, followed by pumping the immunomagnetic nanoparticles (MNPs) and palladium/platinum (Pd/Pt) nanozymes. Then, the flow rate was changed to 5 L/min within the wet cyclone to facilitate the mixing for forming MNP-bacteria-nanozyme sandwich complexes. After magnetic separation, a colorless mixture of 3,3',5,5'-tetramethylbenzidine (TMB) and hydrogen peroxide (H2O2) was pumped to resuspend these complexes, which were catalyzed by the Pd/Pt nanozymes on the complexes to produce the blue TMBox. The resulting absorbance was finally measured by a self-developed portable microreader, which showed high consistency with the traditional microplate reader. The entire processes, from bioaerosol collection to detection, were automatically controlled via a microcontroller, minimizing manual operation and cross-contamination risks. This platform was demonstrated to complete the airborne bacteria detection in 2.0 h with a detection limit of 459 CFU/m3. This highly integrated platform offers a promising tool for rapid and automated detection of bioaerosols.
Plasma-based CO2 conversion is an emerging defossilization technology that converts a potent greenhouse gas into valuable chemical feedstocks, yet its optimization is hampered by complex nonlinear behavior and resource-intensive experimentation. In this work, we collected a comprehensive database, comprising 358 data points with six key operational and geometric parameters, published in literature between 2010 and 2025. Leveraging this dataset, we developed a hybrid machine learning (ML) model integrating physics-informed neural network (PINN), random forest (RF) and extreme gradient boost (XGB) algorithms to predict CO2 conversion and energy efficiency (EE) in dielectric barrier discharge (DBD) reactors. Under a rigorous group 5-fold cross-validation (CV) protocol, the ensemble consistently outperformed all individual models, with the best-fold model achieving an R 2 of 0.791. Error-correlation analysis revealed that the ensemble weights adapt to the pairwise error correlation structure: PINN consistently provides complementary information, while RF and XGB, being largely interchangeable, are selected according to their individual performance. When applied to prospective experimental validation, the hybrid model achieves an R 2 of 0.92 on unseen data within the explored domain, and it eliminates unphysical predictions in data-sparse regimes, yielding strictly non-negative CO2 conversion estimates. SHapley Additive exPlanations (SHAP) analysis further identified flow rate and power as the dominant input features, collectively accounting for 61%-71% of the model's predictions. This work establishes a robust and interpretable framework while quantifying the generalizability of ML models in heterogeneous data environments, offering a practical tool to accelerate plasma-based gas conversion optimization.
High-rate partial nitritation (HRPN) provides new insights into the mainstream two-stage partial nitritation/anammox (PN/A) process, as its key operating parameters, including short sludge retention time (SRT) and hydraulic retention time, are similar to those of the high-rate activated sludge (HRAS) process commonly used as a pretreatment for PN/A. In this study, partial nitritation in the HRAS (HRAS/PN) process was proposed to simplify the two-stage PN/A process for municipal wastewater treatment. Stable HRPN was first achieved at ultra-short SRT of 2.7-1.7 days, demonstrating the technical feasibility of HRAS/PN. Then, a continuous-flow HRAS/PN reactor was operated for 117 days with SRT of 2.0-1.5 days, achieving nitrite accumulation ratio exceeding 95%, maintaining effluent NO2-‑N/NH4+‑N ratio at around 1.32, and reaching nitrogen loading rate of 0.7 kg N/m3/d with a chemical oxygen demand removal efficiency of 92%. Microbial analysis revealed that the maximum specific growth rate for ammonia-oxidizing bacteria (AOB) was 1.91 d-1, which effectively sustained retention of AOB. In contrast, nitrite-oxidizing bacteria were effectively washed out, with their abundance falling below the detection limit. Finally, a conceptual HRAS/PN-anammox configuration was proposed, offering a potentially compact and low-carbon option for municipal wastewater treatment, particularly in warm-climate mainstream scenarios.
Landfills remain an important endpoint for waste and waste residues, yet current management in the Netherlands requires eternal aftercare to protect public health and the environment. Enhanced waste stabilization in landfills through active treatment, i.e. aeration and leachate recirculation, has potential as a sustainable alternative to current landfill management. However, the influence of active treatment on solid waste properties and subsequent leaching of hazardous contaminants has only received limited investigation. This study investigates these influences in landfill simulation reactors containing 30 kg of waste from different origins, which were treated using aeration, leachate recirculation, and their combination. Large differences in leachate contaminant concentrations were found between treatments. A shift from leachate recirculation to aeration changed prevailing redox conditions from anaerobic to aerobic and decreased pH and dissolved organic and inorganic carbon. Consequently, concentrations of ammonium and inorganic contaminants with a high organic matter binding affinity decreased, whereas other inorganic contaminants first increased in concentration due to mineral dissolution followed by a decrease due to mineral precipitation or binding to reactive surfaces. The underlying mechanisms of these trends were identified based on geochemical modelling. The observed changes during aeration were accelerated when aeration was preceded by leachate recirculation, and concentrations rebounded when anaerobic conditions were reintroduced. Our findings ultimately demonstrate that active treatment of landfills requires careful consideration of the most effective strategy, as trade-offs in contaminant leaching mean their potential risks should be weighed against each other.
High load bioflocculation membrane reactor (HLB-MR) exhibits high organic matter capture efficiency and significant potential for energy recovery. However, its stable operation under high-loading conditions is often constrained by membrane fouling. In this study, a low-intensity, intermittent ex situ ultrasonic regulation strategy was proposed. Ultrasound was applied to the membrane-retained concentrate to synergistically regulate bioflocculation behavior and membrane fouling at the system level. The results showed that the ultrasound-assisted HLB-MR achieved an organic matter capture efficiency of up to 77.0% and reduced the transmembrane pressure (TMP) increase rate by 68.7%. The sustained stability of bioflocculation and the significant mitigation of membrane fouling can be primarily attributed to the "triple-coupling mechanism" induced by low-intensity ex situ ultrasound, including selective modulaton of the microbial community structure, reorganization of extracellular polymeric substances (EPS), and attenuation of metal ion bridging. From an engineering and system-level perspective, the municipal wastewater treatment system with HLB-MR as the core unit achieved a net energy recovery of 0.2035 kWh/m3, reduced total carbon emissions by approximately 26.0% compared with the conventional A2O process, and lowered membrane fouling-related operational costs by 57.7% relative to non-ultrasonic systems. In summary, the ultrasound-assisted HLB-MR demonstrates strong potential as a sustainable urban wastewater treatment technology, enabling synergistic benefits in organic matter recovery, energy production, and environmental improvement.
Effective decontamination and decommissioning (D&D) planning for facilities storing spent nuclear fuel requires comprehensive radiological characterization of structural materials. Although previous studies have quantified the spent fuel source term for Indonesia's G. A. Siwabessy research reactor, a significant gap remains in assessing neutron-induced activation inventories in the structures of the Interim Storage of Spent Fuel (ISSF) pool over a 50-year storage period. This study aims to model neutron transport and calculate the time-dependent specific activity (Bq/g) in the stainless steel (SS) rack, SS liner, and Portland concrete walls using the PHITS code coupled with the DCHAIN decay analysis method. The analysis confirms that the physical shielding provided by the substantial pool water is highly effective, reducing activation levels in the structural material by up to three orders of magnitude from the SS rack to the concrete base. The SS rack, positioned in direct contact with the spent fuel, exhibited the highest specific activity (3.65 × 10-1 Bq/g), dominated by the long-term buildup of 56Mn, 55Fe, and 60Co. The activity inventories calculated for the SS liner (3.62 × 10-3 Bq/g) and the concrete base structure (4.77 × 10-3 Bq/g), driven by long-lived radionuclides such as, 3H, 24Na, and 152Eu. These results confirmed the initial hypothesis that the majority of the pool structural volume may satisfy clearance under national regulations.
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Partial nitritation (PN) is an important source of nitrous oxide (N2O) emissions, and a low biodegradable chemical oxygen demand to ammonium (bCOD/NH4+-N) ratio tends to aggravate N2O emissions. However, the specific release characteristics and potential mechanisms with increasing bCOD/NH4+-N within a low ratio range have not been elucidated. In this study, a continuous-flow PN reactor was operated using food waste digestate characterized by fluctuating low bCOD/NH4+-N ratios. When the ratio rose from 0.12 to 1.36, the gaseous N2O emission factor increased from 3.2% to 25.8%. Three mechanisms were inferred to be associated with this increase: (1) To maintain the nitrite-to-ammonium ratio at higher bCOD/NH4+-N, the ammonia oxidation efficiency (AOE) was elevated from 57.7% to 75.1%, which increased the electron flux used for nitrite reduction; (2) to sustain the nitrite-to-ammonium ratio, the aeration coefficient was increased, which elevated the N2O mass transfer coefficient (KLa) from 32 to 705 d-1 and consequently enhanced N2O emissions; (3) the increasing bCOD/NH4+-N induced a nonuniform upregulation of functional genes, the (nirK+nirS)/nosZ rose from 2.62 to 3.14, enhancing the N2O-producing capacity. Overall, AOE-driven electron flux enrichment, aeration coefficient-driven KLa enhancement, and uneven functional gene promotion may have jointly contributed to the increase in N2O emissions with increasing bCOD/NH4+-N.
This paper describes solvent-free three-component coupling reactions in a mortar. The coupling of the water-insoluble aldehydes and alkylamines with resorcinol provided N-alkylmethyl-substituted resorcinols. The three-component coupling reaction was carried out at room temperature in the absence of a solvent, without a specific catalyst or promoter. The aldimine was initially produced by the dehydration of alkanal and primary amine, followed by arylation with resorcinol, which resulted in the formation of the coupling product. The reaction of the isolated imine with resorcinol revealed that the addition of a small amount of water is essential during the coupling process. The presence of a water molecule generated by the dehydration of the aldehyde and amine promoted the formation of new C-C bonds. On the basis of the experimental finding, the reaction mechanism is proposed.
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The possibility of anammox bacteria enrichment from municipal activated sludge inoculated in two batch reactors fed with N-loaded wastewater was investigated. In order to examine the effect of shear force on the N conversion pathways and cultivated biomass, the first reactor was not exposed to any shear force (without stirring-WS), whereas the second reactor was exposed to a shear force (stirring at 150 rpm-S). After about four months of enrichment, the bacterial communities in the inoculated activated sludge and the cultivated biofilms were identified and characterized. Analyses using Polymerase Chain Reaction (PCR) and scanning electron microscopy (SEM) validated the presence of anammox bacteria in the cultivated biofilms, which increased by 2.8 and 3.5 times in the WS and S reactors, respectively, compared to the original inoculum. The average ammonium and nitrite removal efficiencies in WS were 100% and 92%, respectively, while they were 84% and 80% in the S reactor, respectively, in the culture maintained at around 80 mg N/L ammonium under controlled environments. In both reactors, the conversion pathways of N compounds showed that the start-up of anammox began from day 28 with an optimized period that continued until day 98, signifying the enrichment feasibility of anammox from municipal sludge.
Radioiodine-131 (131I) is the most significant environmental contaminant during a short-term nuclear accident. When present in the atmosphere, it concentrates mainly in the thyroid gland through inhalation or ingestion. This can lead to partial or total destruction of thyroid cells, potentially causing hypothyroidism. It therefore negatively affects the thyroid in exposed populations. At high doses, radiation can also cause cellular mutations and increase the risk of thyroid cancer, particularly in children under five years old and those exposed during pregnancy. In such cases, nonradioactive iodine tablets are used to saturate the thyroid and block the absorption of radioactive iodine. This study aimed to quantify and compare total atmospheric emissions of 131I using the ORIGEN-JR code, and to assess the radiological impacts on the environment and humans by estimating and comparing the total effective dose (TED) and committed effective dose equivalent (CEDE) using the HOTSPOT code in the early stages following the Fukushima accident and at the TRIGA Mark-II research reactor in Bangladesh. The simulation results indicate that for the TRIGA MARK-II research reactor, the TED was approximately 379 mSv at a distance of 360 m, with a thyroid CEDE of 19 mSv. For the Fukushima reactor, the TED was approximately 875 mSv at 590 m, with a thyroid CEDE of about 63 mSv. Compared to the IAEA's annual regulatory limits, the TED and CEDE resulting from the Fukushima accident exceeded the permissible thresholds, requiring both evacuation of the population and iodine prophylaxis. Conversely, for the TRIGA MARK-II research reactor, the distribution of iodine tablets is not necessary; however, containment measures remain essential.