Stable Reactor Operation Research Articles

T2-LSTM-Based AI System for Early Detection of Motor Failure in Chemical Plants

In the chemical industry, stable reactor operation is essential for consistent production. Motor failures can disrupt operations, resulting in economic losses and safety risks. Traditional monitoring methods, based on human experience and simple current monitoring, often need to be faster and more accurate. The rapid development of artificial intelligence provides powerful tools for early fault detection and maintenance. In this study, the Hotelling T2 index is used to calculate the root mean square values of the normal motor’s x, y, and z axes. A long short-term memory (LSTM) model creates a trend model for the Hotelling T2 index, determining an early warning threshold. Current anomaly detection follows the ISO 10816-1 standard, while future anomaly prediction uses the T2-LSTM trend model. Validated at a chemical plant in Southern Taiwan, the method shows 98% agreement between the predicted and actual anomalies over three months, demonstrating its effectiveness. The T2-LSTM model significantly improves the accuracy of motor fault detection, potentially reducing economic losses and improving safety in the chemical industry. Future research will focus on reducing false alarms and integrating more sensor data.

Experimental investigations on physical mechanisms of RMP-induced intrinsic rotations at EAST

Plasma spontaneous rotation significantly affects confinement performance and stability in tokamaks. Effectively inducing this rotation is essential for stabilizing resistive wall modes (RWMs) and ensuring the stable operation of the International Thermonuclear Experimental Reactor (ITER). Recent experiments conducted on the Korea Superconducting Tokamak Advanced Research (KSTAR) device demonstrated that resonant magnetic perturbations (RMPs) can induce neoclassical toroidal viscosity (NTV) torque under certain conditions, successfully driving plasma rotation. Similarly, on the Experimental Advanced Superconducting Tokamak (EAST), an increase in plasma rotation in the direction of the plasma current has been observed following RMP application. However, unlike the KSTAR findings, the NTV torque simulations for EAST are two orders of magnitude lower than experimental measurements, indicating additional mechanisms beyond NTV may drive the observed plasma rotations. To investigate these mechanisms, momentum balance, causality, and statistical analyses are performed at EAST. An increase in rotation velocity is found to correlate with significant changes in the <inline-formula><tex-math id="M4">\begin{document}${\boldsymbol{E}}\times{\boldsymbol{B}}$\end{document}</tex-math></inline-formula> flow, matching the RMP-induced torque distribution. This alignment suggests that residual stress, arising from variations in <inline-formula><tex-math id="M5">\begin{document}${\boldsymbol{E}}\times{\boldsymbol{B}}$\end{document}</tex-math></inline-formula> shear, may cause the observed rotation to increase. The effects of stochastic fields on multi-scale turbulence are considered as a possible explanation for correlations between <inline-formula><tex-math id="M6">\begin{document}${\boldsymbol{E}}\times{\boldsymbol{B}}$\end{document}</tex-math></inline-formula> velocity and toroidal rotation. Stochastic fields appear to enhance the inertia of large-scale turbulence while driving small-scale turbulence to maintain quasi-neutrality. The resulting turbulent Reynolds stress, generated by small-scale turbulence, may account for the increases of the observed <inline-formula><tex-math id="M7">\begin{document}${\boldsymbol{E}}\times{\boldsymbol{B}}$\end{document}</tex-math></inline-formula> velocity during RMP application. Statistical analysis further highlights the importance of island width in understanding the threshold RMP current in ramping-up RMP experiments, supporting the conclusion that turbulence-driven <inline-formula><tex-math id="M8">\begin{document}${\boldsymbol{E}}\times{\boldsymbol{B}}$\end{document}</tex-math></inline-formula> shear-related residual stress is the key mechanism of driving plasma rotation following RMP application.

Towards Optimisation of Microalgae Cultivation through Monitoring and Control in Membrane Photobioreactor Systems

This research lays a foundation for optimised membrane photobioreactor performance and introduces novel control parameters crucial for advancing microalgae cultivation techniques and promoting environmental sustainability. Particularly, this study presents an innovative solids retention time (SRT) controller designed for a pilot-scale membrane photobioreactor. Employing a fuzzy-logic knowledge-based approach, this controller uses the first derivative of pH data dynamics (pH′) as an input variable, directly correlated with nitrogen recovery rate and biomass productivity when normalised by average light irradiance (I2). Through a feedback mechanism, it regulates daily SRT variations, ensuring stable reactor operation, optimal volatile suspended solids concentration, efficient nitrogen removal, and enhanced biomass productivity. Normalised nitrogen recovery rate, considering solar light irradiance and volatile suspended solids concentration, increased by 51% compared to previous studies employing fixed SRT and hydraulic retention time (HRT). Combining this SRT controller with a previously studied HRT controller could potentially amplify biomass productivity efficiency. In addition, controlling or not controlling the HRT and SRT are assessed in terms of filtration performance and GHG emissions. Finally, a new dissolved-oxygen-based parameter shows promise for continuous microalgae culture control.

The influencing mechanism of AD-MEC domesticated sludge to alleviates propionate accumulation and enhances methanogenesis

Anaerobic digestion combined with microbial electrolysis cell (AD-MEC) could maintain stable reactor operation and alleviating the anaerobic digestion (AD) propionate accumulation. In this study, the addition of sludge to AD-MEC was examined as a way to enhance system performance and explore the microbial interaction mechanism after electric field domestication. The results showed that under 1000 and 4000 mg/L propionate, the methane production of the sludge from AD-MEC increased by 34.29 % and 9.70 %, respectively, as compared to the AD sludge. Gompertz fitting analysis showed that sludge after electric field domestication enhancing its continuous methanogenic capacity. Further analysis showed that sludge extracellular electron transfer capacity was enhanced in AD-MEC and that its domesticated granular sludge formed a microbial community function with acid-degrading synergistic methanogenesis. The results of the study may provide theoretical support and optimization strategies for the application of AD-MEC system.

Investigation of pipelines defect localization for fusion reactor by using T(0,1) mode ultrasonic guided waves

The stable operation of a fusion reactor depends on the reliable functioning of various accessory systems, many of which comprise extensive pipelines with different diameters and diverse cladding. Defects in pipelines can occur due to manufacture, thermal stress, and fatigue, threatening the systems’ safety and reliability. Ultrasonic guided waves (UGWs) testing offers a promising approach for remotely locating these minute defects. The study explores non-dispersive fundamental torsional guided (T(0,1)) waves, particularly their influence on minor defect detection in stainless steel pipes. Both finite element simulations and experimental trials reveal that reflection coefficients, indicative of defect presence, rapidly escalate from 64 to 128 kHz. The optimal frequency for minor defect detection lies between 128 and 180 kHz. A significant finding from the circumferential distribution spectrum and angle profile reveals pipe diameter's dominant influence on the reflection energy distribution concentration. Furthermore, this highlights the unique ability of T(0,1) guided waves to precisely locate defects in the circumferential direction within large-diameter pipes over long distances. The results underscore the promising potential of UGWs testing in complex pipelines of fusion reactors.

How efficiently does a metabolically enhanced system with denitrifying anaerobic methane oxidizing microorganisms remove antibiotics?

In this work, the novel N-damo (Nitrite dependent anaerobic methane oxidation) process was investigated at high biomass activities for its potential to remove simultaneously nitrite and methane, as well as selected antibiotics commonly found in sewage in trace amounts. For this purpose, two MBRs were operated at three high nitrite loading rates (NLRs), namely 76 ± 9.9, 161.5 ± 11.4 and 215.2 ± 24.2 mg N–NO⁻2 L−1 d−1, at long-term operation. The MBRs performance achieved a significantly high nitrite removal activity for an N-damo process (specific denitrifying activity of up to 540 mg N–NO⁻2 g−1 VSS d−1), even comparable to heterotrophic denitrification values. In this study, we have implemented a novel operational strategy that sets our work apart from previous studies with similar bioreactors. Specifically, we have introduced Cerium as a trace element in the feeding medium, which serves as a key differentiating factor. It allowed maintaining a stable reactor operation at high NLRs. Microbial community composition evidenced that both MBRs were dominated with N-damo bacteria (67–87% relative abundance in period III and I, respectively). However, a decrease in functional N-damo bacteria (Candidatus Methylomirabilis) abundance was observed during the increase in biomass activity and concentration, concomitantly with an increase of the other minor families (Hypomicrobiaceae and Xanthobacteraceae). Most of the selected antibiotics showed high biotransformation such as sulfamethoxazole, trimethoprim, cefalexin and azithromycin, whereas others such as roxithromycin and clarithromycin were only partially degraded (20–35%). On the contrary, ciprofloxacin showed almost no removal. Despite the metabolic enhancement, no apparent increase on the antibiotic removal was observed throughout the operation, suggesting that microbiological composition was of greater influence than its primary metabolic activity on the removal of antibiotics.

Design, Heat Transfer, and Visualization of the Milli-Reactor by CFD and ANN

This paper proposes a milli-reactor design method incorporating reactor runaway criteria. Based on Computational Fluid Dynamic (CFD) simulation, neural networks are applied to obtain the optimal reactor structure according to the target reaction requirements. Varma’s theory, the critical Nusselt number for stable operation of the flow reactor, is derived. Inserts of the multi-blade structure are designed and investigated to enhance mixing and heat transfer performance. The flow field and heat transfer capacities are obtained by CFD calculations in the range of Re 50–1800. The internal components increase the heat transfer performance up to 21 times, and the pressure drop up to 16 times. The inclined angle of the blade is recommended to be 45°, which can effectively improve heat transfer without generating excessive pressure drop. By partial least squares regression (PLS) analysis, Re and the number of blades are the most critical factors affecting heat transfer, and the five blades and smaller tilt angles are recommended. The CFD calculation results are in good agreement with the Particle Image Velocimetry (PIV) experimental results.

Treatment of phenols and NH3–N with activated carbon and polyurethane carrier in biological enrichment reactor

Coal pyrolysis wastewater contains a large number of phenols, ammonia, and various monocyclic and polycyclic aromatic compounds. In the study, activated carbon (AC) or polyurethane (PU) suspension carriers were comprehensively compared from efficiency, influencing factors, extracellular polymeric substances, and microbial population distribution to explore the suitable carrier in biological enrichment reactor the treatment of coal pyrolysis wastewater. In the start-up stage, the treatment effect of COD and total phenol (TPh) in the PU group (COD 86%, TPh 75%) was lower than that of the AC group (COD 94%, TPh 88%). However, with the loading of biofilm on PU, the treatment effects in the PU group began to improve. When COD was approximately 1000 mg/L and TPh was 500 mg/L, both the AC group and PU group showed sound treatment effects on COD (≥87%) and TPh (∼99%). Moreover, the PU group showed a higher removal effect of NH3–N (32.22%) and TN (30.85%). HRT should be 24 h to ensure partial degradation of organic matter and save carbon source dosage of the subsequent A/O treatment unit. Moreover, it had a removal effect on NH3–N and TN, which could effectively reduce the load of the subsequent multistage A/O treatment unit. The dominant functional bacteria in the AC and PU groups included Acidovorax, Alicycliphilus, Chryseobacterium, Rhodanobacter, and Thermomonas. Acidovorax, Alicycliphilus, and Chryseobacterium were the main functional bacteria involved in TPh and COD degradation. AC was suitable for rapidly reducing the concentration of pollutants or dealing with sudden increases in pollutants, while PU was more conducive to the long-term and stable operation of the biological enrichment reactor.

Performance of tungsten nitride compound surfaces to resist sputtering under intense irradiation in nuclear fusion reactors

The formation of tungsten nitride (WNx) films has been experimentally detected on the surface of tungsten divertors in fusion reactors after seeding cooling systems using nitrogen, and hence the sputtering resistance of the WNx film is crucial for the stable operation of the fusion reactor. By performing first-principles calculations, we investigated the sputtering resistance of W2N1, W1N1, and W2N3 surfaces, respectively. It was found that the tungsten nitride surfaces have good sputtering resistance. Especially, the sputtering resistance of the nitrogen-rich (001) surface of W1N1 is better than that of pure tungsten. However, hydrogenation at surface N atoms will weaken the chemical bonds between the N atoms and their own nearest-neighbors in the surface, facilitating the escape of the N atoms from the irradiated surface, even forming ammonia molecules. Our efforts not only reveal the performance of sputtering resistance of WNx surfaces, but also show the influence of hydrogen on the sputtering-resistant properties of WNx, which are valuable for assessing the state and stability of WNx films on divertor surfaces.

Optimization analysis of HTR-PM600 fresh fuel transport container under multiple impact loading conditions

Reliable transportation of Spherical Fuel Element (SFE) is vital for the stable operation of a High-Temperature Reactor (HTR) power plant. As a solution, Tsinghua University has developed the HTR-PM600 transport container, for transporting the inner storage canister and the SFEs. However, the cost of fabrication and transportation has been a major obstacle for the implementation of it. Thus, one of the most feasible methods is to make a lightweight design. Accordingly, this present study aims to investigate and optimize the lightweight and safety performance of the HTR-PM600 transport container under multiple impact loading conditions. In this study, the parametric study is conducted to reveals the effect of the thickness of HTR-PM600 transport container components under multiple impact loading conditions. On the basis, the ε-Constraint method coupled with the Taguchi method is utilized to explore the optimal design of HTR-PM600 transport container for multi-objective optimization for lightweight and safety performance, which is verified through a comparison between the initial and optimal design. The optimal design presents a superior safety performance and a 15.7% improvement on lightweight under multiple impact loading conditions.

Research for axial power distribution control of a space nuclear reactor based on nonlinear model

During the operating process of a space nuclear reactor, once the local overload of heat energy occurs in the core, the corresponding fuel elements would be damaged and the lifespan of the reactor would be seriously reduced. In fact, the heat flux at any point in the core is proportional to the neutron flux density. A sufficiently flat axial neutron flux density distribution can protect the fuel assembly from frequent load changes. It is so clear that the axial power distribution control is crucial for the safe and stable operation of the space nuclear reactor. However, the space nuclear reactor is a distributed parameter system, which brings great challenges to the traditional lumped parameter control methods. In this paper, a distributed parameter control method is proposed to suppress the initial neutron flux peaks and realize the exponential stability of the neutron flux distribution control system. First of all, the spatiotemporal model of the reactor core based on the neutron diffusion equation is established. Then, the stability analysis of the control law for the neutron flux distributed parameter control problem is performed by constructing the Lyapunov function. The optimization technique based on the spatial differential linear matrix inequality is used to approximate the solution of the suboptimal integral control law. The control law is implemented by rotating drum, and the flat distribution of the axial power of the core is realized by the distributed parameter control. Finally, the numerical results are provided to validate the feasibility of the proposed control scheme.

Module coordination control of multi-modular lead-based reactor systems

The multi-modular reactor, which connects multiple reactor units to drive a single turbine, is considered to be an innovation in the nuclear energy system. Since multiple reactor units are coupled together by the common secondary loop, the load change of any reactor will affect its own coolant temperature, and also the power of other reactor units. It is obviously that module coordinated control is significant for the safe and stable operation of the multi-modular reactor, which induces the necessity of the study in module coordination. Motivated by this, this paper proposes the method of decoupling between each module to realize the coordinated control of the multi-modular reactor. An operation and control simulation of the multi-modular lead-based reactor based on the China lead-based research reactor (CLEAR-I) is performed. The frequency domain identification method combined with the multivariable frequency response method is proposed to realize the effective decoupling of the system. The purpose of this method is to reduce the complexity of the control system design and make full use of the computer aided design technology. The transfer function matrix of the system is identified through the frequency response experiments. The pseudo diagonal dominance method is adopted to develop the constant diagonal dominant compensation matrix for the inverse transfer function, and then the inverse Nyquist array (INA) method is adopted to design controller for the compensated system. The design of the multiple-input multiple-output system is simplified to a series of single-variable system designs. The numerical results show the feasibility and satisfactory control performance.

Impact of operational conditions on methane yield and microbial community composition during biological methanation in in situ and hybrid reactor systems

BackgroundBiogas can be upgraded to methane biologically by adding H2 to biogas reactors. The process is called biological methanation (BM) and can be done in situ in a regular biogas reactor or the biogas can be transferred to a separate ex situ upgrading reactor. The hybrid BM concept, a combination of in situ and ex situ BM, has received little attention, and only a few studies have been reported. The hybrid BM has the advantage of resolving the issue of pH increment during in situ BM, while the size of the ex situ BM reactor could be reduced.ResultsIn this study, the efficiency of in situ and hybrid biological methanation (BM) for upgrading raw biogas was investigated. The hybrid BM system achieved a CH4 yield of 257 mL gVS−1 when degrading a feedstock blend of manure and cheese waste. This represented an increase in methane yield of 76% when compared to the control reactor with no H2 addition. A 2:1 H2:CO2 ratio resulted in stable reactor performance, while a 4:1 ratio resulted in a high accumulation of volatile fatty acids. H2 consumption rate was improved when a low manure–cheese waste ratio (90%:10%) was applied. Furthermore, feeding less frequently (every 48 h) resulted in a higher CH4 production from CO2 and H2. Methanothermobacter was found to dominate the archaeal community in the in situ BM reactor, and its relative abundance increased over the experimental time. Methanosarcina abundance was negatively affected by H2 addition and was nearly non-existent at the end of the experiment.ConclusionsOur results show that hybrid BM outperforms in situ BM in terms of total CH4 production and content of CH4 in the biogas. In comparison to in situ BM, the use of hybrid BM increased CH4 yield by up to 42%. Furthermore, addition of H2 at 2:1 H2:CO2 ratio in in situ BM resulted in stable reactor operation.

Evolution and fluidization behaviors of wet agglomerates based on formation-fragmentation competition mechanism

When the liquid is injected into a gas-solid fluidized bed, particles are easily wetted and prone to form liquid bridges among them, further leading to particle agglomeration. Wet particle agglomeration induced by liquid bridge is dynamic and unstable, and its evolution behavior affects the stable operation of fluidized bed reactor. Therefore, based on the formation-fragmentation competition mechanism, a wet agglomeration evolution model is proposed to predict the evolution characteristics of wet agglomerates under different conditions. Furthermore, a modified drag force model which attributed the effect of wet agglomerates into the drag force was established and applied to the CFD simulation of a fluidized bed with wet agglomerates under the liquid spray-evaporation equilibrium state. Meanwhile, the particle image velocimetry (PIV) technology is applied in this work, and it was found that the vertical solid velocity simulated by CFD is in good agreement with the PIV measurement results.

Performance and Microbial Community Analysis of an Electrobiofilm Reactor Enhanced by Ferrous-EDTA.

The biological reduction of ferrous ethylenediaminetetraacetic acid (EDTA-FeII-NO and EDTA-FeIII) is an important process in the integrated electrobiofilm reduction method, and it has been regarded as a promising alternative method for removing NOx from industrial boiler flue gas. EDTA-FeII-NO and EDTA-FeIII are crucial substrates that should be biologically reduced at a high rate. However, they inhibit the reduction processes of one another when these two substrates are presented together, which might limit further promotion of the integrated method. In this study, an integrated electrobiofilm reduction system with high reduction rates of EDTA-FeII-NO and EDTA-FeIII was developed. The dynamic changes of microbial communities in the electrobiofilms were mainly investigated to analyze the changes during the reduction of these two substrates under different conditions. The results showed that compared to the conventional chemical absorption-biological reduction system, the reduction system exhibited better performance in terms of resistance to substrate shock loading and high microbial diversities. High-throughput sequencing analysis showed that Alicycliphilus, Enterobacteriaceae, and Raoultella were the dominant genera (>25% each) during the process of EDTA-FeII-NO reduction. Chryseobacterium had the ability to endure the shock loading of EDTA-FeIII, and the relative abundance of Chryseobacterium under abnormal operation conditions was up to 30.82%. Ochrobactrum was the main bacteria for reducing nitrate by electrons and the relative abundance still exhibited 16.11% under shock loading. Furthermore, higher microbial diversity and stable reactor operation were achieved when the concentrations of EDTA-FeII-NO and EDTA-FeIII approached the same value (9 mmol·L−1).

Engineered methanotrophic syntrophy in photogranule communities removes dissolved methane

The anaerobic treatment of wastewater leads to the loss of dissolved methane in the effluent of the treatment plant, especially when operated at low temperatures. The emission of this greenhouse gas may reduce or even offset the environmental gain from energy recovery through anaerobic treatment. We demonstrate here the removal and elimination of these comparably small methane concentrations using an ecologically engineered methanotrophic community harbored in oxygenic photogranules. We constructed a syntrophy between methanotrophs enriched from activated sludge and cyanobacteria residing in photogranules and maintained it over a two-month period in a continuously operated reactor. The novel community removed dissolved methane during stable reactor operation by on average 84.8±7.4% (±standard deviation) with an average effluent concentration of dissolved methane of 4.9±3.7 mg CH4∙l−1. The average methane removal rate was 26 mg CH4∙l−1∙d−1, with an observed combined biomass yield of 2.4 g VSS∙g CH4−1. The overall COD balance closed at around 91%. Small photogranules removed methane more efficiently than larger photogranule, likely because of a more favorable surface to volume ratio of the biomass. MiSeq amplicon sequencing of 16S and 23S rRNA revealed a potential syntrophic chain between methanotrophs, non-methanotrophic methylotrophs and filamentous cyanobacteria. The community composition between individual photogranules varied considerably, suggesting cross-feeding between photogranules of different community composition. Methanotrophic photogranules may be a viable option for dissolved methane removal as anaerobic effluent post-treatment.

Application of evaporation cooling in a microstructured packed bed reactor for decentralized CO2 methanation

The objective of this work is the detailed analysis of the performance of an advanced packed-bed reactor with evaporation cooling structure and 1.5 (STP) m3 h−1 reactant throughput. Application of pressurized water as the cooling medium enables stable reactor operation within a safe temperature window at extremely high space-time yield (∼ 1000 m3CH4/m3reactorh, ∼ 18,000 m3CH4/m3reaction-volumeh). The performance of the reactor regarding its axial temperature profile and product quality under different process conditions such as water coolant flow rate distribution and pressure in cooling passages is evaluated in detail. The feed throughput and composition influence on reactor performance during start-up, steady-state and transient operational conditions for a technical methanation plant are investigated. For reactor description purposes and computing the heat transfer coefficient, a cascade model of perfectly mixed CSTRs is implemented. The modelling results predict the experimental data very well regarding the temperature profile and product composition.

Experimental investigation on control of temperature asymmetry and nonuniformity in a pilot scale thermal flow reversal reactor

Temperature asymmetry along flow direction and nonuniformity vertical to flow direction have been the prominent obstacles to the stable operation of thermal flow reversal reactor (TFRR) devices in industry. However, the relevant investigations are sorely lacking especially through the experiment method due to the limitation of laboratory test conditions. In this study, temperature asymmetry and nonuniformity for extra lean CH4/air combustion (feed methane concentration below 1 vol%) in a pilot TFRR were investigated experimentally. The effects of the preheating process and feed methane concentration were investigated. The switching time of 120 s and feed rate of 400 m3/h were determined for the preheating process. In the transition period between preheating completion and cyclic steady state achievement, the operation pattern with preheater off was beneficial to heat storage. Stable combustion for minimum feed methane concentration of 0.2 vol% was confirmed in the experiment. When feed methane concentration was decreased from 0.8 vol% to 0.2 vol%, higher feed methane concentration was easier to intensify temperature nonuniformity. To restrain the increase of temperature asymmetry and nonuniformity, an electronically controlled adjustment was adopted. Valve opening ratio could be monitored to obtain more equivalent average temperature values of two sections of the packed bed. A 55-min process and a 116-min process were picked out from the cyclic steady-state period to eliminate temperature nonuniformity through adjusting valve opening ratio. As a result, the gaps in the high-temperature section width of two sections get narrowed and the average temperature of two sections is almost the same. The switching time ratio could be regulated to shift high-temperature cores of two sections to middle height position. A 58 min long process was selected with a switch time ratio of 1.25 and the temperature center height of both two sections dropped obviously. Synchronous adjustment of the valve opening ratio and the switching time ratio accelerated the adjustment process and double effects could be acquired in the meantime. A 36-min long process and a 28-min long process are chosen for simultaneous adjustment. The average temperature of two sections reach good agreement in the end and the temperature center height of two sections both drop obviously. This work is beneficial to the development of TFRR for better dealing with ventilation air methane and other lean gaseous fuel streams.

Impact of thiocyanate on the reformation of aerobic granules from the disintegrated granules treating phenol-contained wastewater along with the recovery of nitritation efficiency

The focus of the study was to evaluate the effect of thiocyanate (SCN−) addition on the reformation of the aerobic granules after its disintegration along with the pollutants degradation profile and nitritation recovery in a sequencing batch reactor (SBR). Granules were cultivated with phenol (400 mg L-1) and ammonia-nitrogen (NH4+-N) (100 mg L-1) in an SBR. After 75 days of stable reactor operation with volatile suspended solids, granule size, and extracellular polymeric substances (EPS) of 3.67 g L-1, 1202.03 ± 487.78 μm, and 78.23 mg gVSS-1, respectively, the granules started to deteriorate, and disintegration continued up to 84th day. Then reformation of disintegrated granules was observed after the gradual addition of SCN− (10−340 mg L-1). The size of granules increased to 1819.87 ± 43.44 μm along with higher EPS (101.45 ± 1.06 mg gVSS-1) and recovery of nitritation efficiency. A signification impact was observed in granule characteristics (sludge volume index and granule settling velocity of 26.31 ± 0.80 mL gTSS-1 and 57.32 ± 0.96 m h-1, respectively) because of microbial aggregation caused by sticky EPS secretion. It was found that SCN− played an important role in the granule reformulation by provoking the secretion of EPS, a very high binding capacity substance.

Application of the Anammox in China-A Review.

Anaerobic ammonia oxidation (anammox) has been one of the most innovative discoveries for the treatment of wastewater with high ammonia nitrogen concentrations. The process has significant advantages for energy saving and sludge reduction, also capital costs and greenhouse gases emissions are reduced. Recently, the use of anammox has rapidly become mainstream in China. This study reviews the engineering applications of the anammox process in China, including various anammox-based technologies, selection of anammox reactors and attempts to apply them to different wastewater treatment plants. This review discusses the control and implementation of stable reactor operation and analyzes challenges facing mainstream anammox applications. Finally, a unique and novel perspective on the development and application of anammox in China is presented.