Conventional Batch Reactor Research Articles

Dynamics of the activated sludge in a newly-defined green bio-sorption reactor (GBR)

When upgrading an aging wastewater treatment plant (WWTP), the sludge management line is always out of consideration in terms of cost and easy-operation. This study presented the dynamics of the sludge when upgrading a conventional sequencing batch reactor (SBR) to green bio-sorption reactor (GBR) by embedding alum sludge-based constructed wetland (AlCW). The aluminum (Al(III)) content in the effluent and the resultant impact on organisms were also evaluated. The results showed that the Al(III) residues was at an acceptable level (<0.2 mg/L). The AlCW and its leachate Al(III) did not pose any detrimental impact on the activity of heterotrophic organisms and the nitrifiers whereas the activity of the polyphosphate accumulating organisms was completely suppressed and eliminated out of the reactor. In addition, the Al(III) hydroxides and natural organic matter promoted the flocculation of activated sludge flocs by complexation with the extracellular polymeric substances. As a result, the larger and compact activated sludge led to an increase of the settling velocity and the dewatering efficiency while deteriorating the sludge compressibility (sludge volume index of 150 mL/g). Interestingly, this laboratory-scale GBR was verified to be a promising alternative to upgrade the ageing WWTPs simultaneously with an improvement of the dewatering properties of the activated sludge.

A chloride-radical-mediated electrochemical filtration system for rapid and effective transformation of ammonia to nitrogen

Water contamination from ammonia has recently became a global concern. Herein, a chloride-radical-mediated electrochemical filtration system has been developed towards effective and rapid conversion of ammonia to nitrogen (N2). This continuous-flow system consists of a nanoscale tin oxide modified carbon nanotube (SnO2-CNT) anode and a Pd−Cu co-modified Ni foam (Pd−Cu/NF) cathode. The SnO2-CNT anode enables the Cl− oxidation to a chloride radical (Cl) at a proper anode potential (e.g., 2.5 V vs. Ag/AgCl) without severe self-oxidation. The macro-porous Pd−Cu/NF cathode further reduces anodic by-products (e.g., NO3− and NO2−) to N2. EPR and scavenging tests indicate that Cl was the dominant radical specie responsible for ammonia conversion. Anode potentials, chloride concentration, flow rate and solution pH were identified as key parameters affecting the overall conversion performance. The proposed continuous-flow system showed enhanced conversion kinetics as compared to the conventional batch reactor due to the convectively enhanced mass transport. This study provides new insight for the rational design of advanced continuous-flow systems towards ammonia decontamination from water bodies.

Safe and Scalable Aerobic Oxidation by 2-Azaadamantan-2-ol (AZADOL)/NOx Catalysis: Large-Scale Preparation of Shi’s Catalyst

A method for safe and scalable aerobic alcohol oxidation using 2-azaadamantan-2-ol (AZADOL), an azaadamantane-type hydroxylamine catalyst, with a NOx cocatalyst in a conventional batch reactor has been developed. The use of 2 mol % AZADOL and 10 mol % NaNO2 was determined to promote aerobic alcohol oxidation quantitatively within a reasonable time (8 h). Safety is ensured by controlling the reaction temperature below the flash point of the acetic acid solvent. The robustness of the developed method is demonstrated by the 500 g scale oxidation of diacetone fructose into Shi’s catalyst for asymmetric epoxidation.

The effect of Cu–Zn distribution in zincian malachite on the formation of individual CuO and ZnO particles

Cu–Zn distribution in zincian malachite was regulated in preparation process, and its effect on the formation of CuO and ZnO during the thermal decomposition was investigated. In the HRTEM images, there are obvious individual particles comprised of pure CuO or ZnO in the calcined samples prepared by conventional batch reactor (BR), whereas no pure particle appears in the samples prepared by microchannel reactor (MR). The fraction of Zn2+ incorporating into malachite and the relevance between Cu and Zn confirmed MR precursors were more homogeneous than BR precursors. The TGA/DTG curves showed the uniform distribution caused more interfaces and stronger interaction between Cu and Zn, which could depress the formation of individual CuO and ZnO particles. The combined effects of non-uniform distribution and thermodynamics de-mixing lead to the appearance of CuO and ZnO particles. The result illustrates how the Cu–Zn distribution acts on the thermal decomposition and affects catalyst structure.

Influence of mixed feeding rate in a conventional SBR on biological P-removal and granule stability while treating different industrial effluents.

In this study, the influence of the anaerobic mixed feeding rate on granule stability and reactor performance in a conventional sequencing batch reactor (C-SBR) was investigated while treating various industrial wastewaters. A laboratory-scale SBR fed with malting wastewater rich in phosphorus was operated for approximately 250 days, which was divided into two periods: (I) mixed pulse feed and (II) prolonged mixed feed. Initially, no bio-P activity was observed. However, by lowering the feeding rate biological P-removal was rapidly established and no effect on the aerobic granular sludge (AGS) characteristics was observed. Additionally, to investigate the effect of the mixed feeding rate when treating an industrial effluent with low phosphorus content, i.e. brewery wastewater, a laboratory-scale reactor was operated for approximately 400 days applying different mixed feeding rates. Morphological and molecular analysis indicated that a low substrate concentration promoted the enrichment of anaerobic carbon storing filaments when fed with brewery wastewater. Findings suggest that a prolonged mixed feeding regime can be used as a tool to easily establish bio-P removal in a C-SBR system for the treatment of phosphorus-rich wastewaters. It should however be considered that under P-limiting conditions, enrichment of poly-P storing filaments may occur, possibly due to their higher substrate affinity under anaerobic conditions.

Immobilized lipase screening towards continuous-flow kinetic resolution of (±)-1,2-propanediol

Here, we report a flow chemistry approach for kinetic resolution of (±)-1,2-propanediol protected by trityl group using the packed-bed reactor filled with different immobilized enzymes. It was investigated the performance of 16 immobilized lipases, including commercial Lipozyme TL, Novozym 51032, Novozym 435 (N435) and lipases immobilized by our group. Based on the values of conversion and enantioseletivity, batch experiments were then translated to the continuous-flow environment. Continuous flow (CF) reactors allowed reaction time reduction, from 6 h in batch to 7 min, keeping the values of conversion (up to 50%) and selectivity (E value >200) during the reaction procedure using the commercial enzyme Novozym 435. In addition, continuous flow conditions increased the productivity of kinetic resolution 3 times when compared to conventional batch reactor, after its optimization.

Design of Sewage Treatment Plants for High-Density Urban Reclamation Land

The success of any coastal reclamation project depends strongly on a sound planning and design practices. Due to the land use limitations, sewage treatment plant (STP) of the reclamation land should be fully studied to save land and reduce its adverse effects on the environment. This research focuses on the selection of biological treatment process for a novel STP, as various pollutants of the sewage can be effectively removed via the biological process. The paper presents a design of the STP implemented in Johor as an example, to achieve the goal of ‘zero discharge’ in the reclaimed wetland. The domestic sewage is treated, recycled and reused in the artificial wetland as an ecological green water to achieve Class IIB standard (effluent quality). The novel STP design comprised of the Immobilized Aerobic Biofilm (BioAX) and Mass Bio System (MBS) was compared against the conventional Sequencing Batch Reactor (SBR) process. Combination BioAX + MBS process is advantageous due to significantly less land needed, lower power consumption and lower sludge generation. The system was demonstrated as a viable process to treat the sewage wastewater in the reclamation land to meet Class IIB discharge at a lower environmental footprint, saving up to 50 % of the area.

Nitrous oxide emissions of a mesh separated single stage deammonification reactor.

It is widely accepted that partial nitrification by ANAMMOX has the potential to become one of the key processes in wastewater treatment. However, large greenhouse gas emissions have been panobserved in many cases. A novel mesh separated reactor, developed to allow continuous operation of deammonification at smaller scale without external biomass selection, was compared to a conventional single-chamber deammonification sequencing batch reactor (SBR), where both were equally-sized pilot-scale reactors. The mesh reactor consisted of an aerated and an anoxic zone separated by a mesh. The resulting differences in the structure of the microbial community were detected by next-generation sequencing. When both systems were operated in a sequencing batch mode, both systems had comparable nitrous oxide emission factors in the range of 4% to 5% of the influent nitrogen load. A significant decrease was observed after switching from sequencing batch mode to continuous operation.

Constructing a Continuous Flow Bioreactor Based on a Hierarchically Porous Cellulose Monolith for Ultrafast and Nonstop Enzymatic Esterification/Transesterification

Continuous flow bioreactors have received increasing attention due to their automated high-throughput continuous processing. Cellulose acetate (CA), which is eco-friendly, renewable, and easily accessed, was made into monoliths with interconnected macropores and mesopores on the skeleton by the method of thermally induced phase separation (TIPS). A continuous flow bioreactor was prepared by the immobilization of lipase on the skeleton of CA monolith (CA-MN). Benefiting from the hierarchical structure, the monolith skeletons with mesopores (15.6 nm) serve as a suitable space for lipase immobilization, and the interconnected macropores (3–5 μm) with controllable permeability make the accommodated lipase more accessible to the substrates. Based on this monolithic bioreactor, an ultrafast continuous esterification/transesterification method with more than 90% conversion was developed. Compared to conventional batch reaction modes, the kinetic parameter Vm/Km increased by 66.4-fold, and the catalysis effect (C...

Continuous-Flow Microreactors for Polymer Synthesis: Engineering Principles and Applications.

Polymerization is widely involved in the fabrication of high-performance materials. With its advantages, microreactors are typically applied to reaction processes which are limited by transport properties of conventional batch reactors. As demonstrated in this review, numerous polymerization processes are suitable to be conducted in microreactors with showing excellent polymerization performance (e.g., precisely controllable molecular weights and structures of polymer products). However, distinctive differences between polymerization processes and small-molecular reaction systems can be easily expected since fluid physical properties vary significantly during the polymerization. Herein, we firstly clearly describe the engineering principles such as mass transport phenomena and energy dissipation related to polymerization processes in microreactors, and then give a great deal of application examples (classified as homogeneous polymerization, heterogeneous polymerization, and photopolymerization) through which readers indeed can further understand these relevant principles. Finally, the remaining challenges associated with the application of microreactor technology for polymerization processes and remarking conclusions are presented.

Rational Design of High-Performance Continuous-Flow Microreactors Based on Gold Nanoclusters and Graphene for Catalysis

In this work, we rationally designed a high-performance microreactor system for continuous-flow catalysis. The membrane consists of ultrasmall gold nanoclusters (AuNCs) and two-dimensional graphene. The Au cores of the NCs act as catalysts, while their ligands have two functions: (1) protecting the Au cores to avoid agglomeration and (2) providing a well-defined surfactant assembly to disperse graphene in aqueous solution. Hydrogenation of 4-nitrophenol (4-NP) was employed as model reaction to evaluate catalytic activity. The catalytic membrane microreactor demonstrated excellent catalytic activity and stability, where complete 4-NP conversion was readily achieved via a single pass through the membrane. This desirable performance was maintained over 12 h of continuous operation, although a certain amount of organic buildup on the membrane was observed. The catalytic membrane microreactor outperforms conventional batch reactors due to its improved mass transport. 4-NP-spiked real water samples were also co...

Ligand-Free Nano-Au Catalysts on Nitrogen-Doped Graphene Filter for Continuous Flow Catalysis.

In this study, the authors rationally designed a high-performance catalytic filter for continuous flow catalysis. The catalytic filter consisted of ligand-free nanoscale gold (nano-Au) catalysts and nitrogen-doped graphene (N-rGO). The Au catalyst was fabricated in situ onto a pre-formed N-rGO support by the NaBH4 reduction of the Au precursor, and the size of the nano-Au was fine-tuned. A hydrothermal pretreatment of graphene oxide enriched nitrogen-containing species on the surface of two-dimensional graphene supports and enhanced the affinity of Au precursors onto the support via electrocatalytic attraction. The nano-Au catalysts acted as high-performance catalysts, and the N-rGO acted as ideal filter materials to anchor the catalysts. The catalytic activity of the as-designed catalytic filter was evaluated using 4-nitrophenol (4-NP) hydrogenation as a model catalytic reaction. The catalytic filters demonstrated superior catalytic activity and excellent stability, where a complete 4-nitrophenol conversion was readily achieved via a single pass through the catalytic filter. The as-fabricated catalytic filter outperformed the conventional batch reactors due to evidently improved mass transport. Some key operational parameters impacting the catalytic performance were identified and optimized. A similar catalytic performance was also observed for three 4-nitrophenol spiked real water samples (e.g., surface water, tap water, and industrial dyeing wastewater). The excellent catalytic activity of the nano-Au catalysts combined with the two-dimensional and mechanically stable graphene allowed for the rational design of various continuous flow catalytic membranes for potential industrial applications.

Application of a micro-meso-structured reactor (NETmix) to promote photochemical UVC/H2O2 processes - oxidation of As(iii) to As(v).

A micro-meso-structured reactor (NETmix) was used for the first time to promote photochemical UVC/H2O2 processes. The NETmix photoreactor consists of a network of chambers and channels, where the liquid flows, sealed with a quartz slab with high UVC transparency. Due to the small size of channels and chambers, the NETmix presents a uniform irradiance through the entire reactor depth, short molecular diffusion distances and large specific interfacial areas, maximizing the pollutant/oxidant contact. In this study, the NETmix photoreactor was evaluated for As(iii) oxidation to As(v) using a photochemical UVC/H2O2 system. The effect of the UVC lamp power (4, 6 or 11 W), the number of UVC lamps (2 or 3 lamps) and the UVC lamp layout (parallel or perpendicular to the flow direction) was evaluated, in order to ensure uniform irradiation of the entire reaction mixture. The optimum H2O2 concentration for each light distribution system was also evaluated. At the best configuration, 3 lamps of 11 W positioned parallel to the flow direction, total As(iii) oxidation ([As(iii)]0 = 1.33 × 10-2 mM) was achieved in 15 min with an absorbed photon flux density of 1.9 × 10-1 einstein per m3 per s. Significant differences were highlighted between the photon flux actually received in the photoreactor and the radiant power emitted by the lamp. A kinetic model able to represent the As(iii) oxidation employing UVC radiation and H2O2 in a micro-meso-structured reactor was presented. The photochemical space time yield (PSTY) values obtained for the micro-meso-structured reactor are higher than for conventional batch reactors, showing that the NETmix technology can be a good solution for application in photochemical processes.

Feed distribution based on sensing ammonium concentration after sub-feeding to achieve target effluent nitrogen concentration in sequencing batch reactors

Conventional sequencing batch reactors (SBRs) have been developed based on nitrogen removal efficiency rather than the effluent nitrogen concentration as a design factor. The purpose of this study was to achieve the target effluent total nitrogen (TN) concentration regardless of the influent nitrogen concentration at 10 m3 pilot SBR. The desired nitrogen removal efficiency was achieved by distributing the influent one to four times in one cycle, but effluent TN concentration fluctuated as the influent nitrogen concentration varied. To achieve the target effluent TN concentration, the residual ammonia concentration after sub-feeding was adjusted to the target nitrogen concentration based on real-time ammonia sensing. When the residual ammonia concentration after sub-feeding was set at 10 or 5 mg NH4+-N L−1, the effluent TN concentration was 9.3 ± 0.6 or 4.6 ± 0.3 mg L−1, respectively, regardless of the influent TN concentration. Furthermore, complete nitrification was achieved under low temperature, from 7.2 to 13.1 °C, by controlling the aeration phase end point based on the real-time ammonia sensing. However, when the residual nitrate concentration was adjusted to a low level, the total phosphorus (TP) removal efficiency was high owing to an increase of phosphate release activity by polyphosphate accumulating organisms.

An Immobilized-Dirhodium Hollow-Fiber Flow Reactor for Scalable and Sustainable C-H Functionalization in Continuous Flow.

A scalable flow reactor is demonstrated for enantioselective and regioselective rhodium carbene reactions (cyclopropanation and C-H functionalization) by developing cascade reaction methods employing a microfluidic flow reactor system containing immobilized dirhodium catalysts in conjunction with the flow synthesis of diazo compounds. This allows the utilization of the energetic diazo compounds in a safe manner and the recycling of the dirhodium catalysts multiple times. This approach is amenable to application in a bulk-scale synthesis employing asymmetric C-H functionalization by stacking multiple fibers in one reactor module. The products from this sequential flow-flow reactor are compared with a conventional batch reactor or flow-batch reactor in terms of yield, regioselectivity, and enantioselectivity.

An Immobilized‐Dirhodium Hollow‐Fiber Flow Reactor for Scalable and Sustainable C−H Functionalization in Continuous Flow

AbstractA scalable flow reactor is demonstrated for enantioselective and regioselective rhodium carbene reactions (cyclopropanation and C−H functionalization) by developing cascade reaction methods employing a microfluidic flow reactor system containing immobilized dirhodium catalysts in conjunction with the flow synthesis of diazo compounds. This allows the utilization of the energetic diazo compounds in a safe manner and the recycling of the dirhodium catalysts multiple times. This approach is amenable to application in a bulk‐scale synthesis employing asymmetric C−H functionalization by stacking multiple fibers in one reactor module. The products from this sequential flow–flow reactor are compared with a conventional batch reactor or flow–batch reactor in terms of yield, regioselectivity, and enantioselectivity.

Stable Immobilization of Size‐Controlled Bimetallic Nanoparticles in Photonic Crystal Fiber Microreactor

AbstractThe possibility of immobilizing ex situ‐synthesized colloidal bimetallic nanoparticles (NPs) of well‐defined characteristics inside hollow core photonic crystal fiber (HC‐PCF) microreactors is demonstrated. With the developed method, PtNi clusters remain strongly attached to the fiber core and can be used as active catalysts for the hydrogenation of an azobenzene dye. The study revealed that optical transmission exhibits a size‐dependent behavior, i.e., smaller NPs bring in less optical signal loss. Sufficient light transmission was achieved for all particle sizes. Furthermore, with these catalytic PCF microreactors, kinetic data can be obtained with a much lower amount of precious metals compared to a conventional batch reactor, opening a new pathway for in situ catalyst screening.

Precise Synthesis of Well-Defined Inorganic-Organic Hybrid Particles.

Synthesis of hybrid particles toward precisely designed hierarchical nanoarchitectures is summarized. In order to satisfy the demands for a variety of materials' performances, the selection of materials, composition and synthesis is carefully done. Flow reactors are one of the useful synthetic means to prepare hybrid materials, especially those with hierarchically and precisely designed multi-components hybrid particles, owing to the efficient mixing and heat exchange in the reactor as well as its connectable (both parallel and sequential) feature. In this review article, after the summary of the preparation of hybrids based on oxides and organics through conventional batch reactors, the application of flow reactors to the preparation of various hybrid particles is introduced to highlight the present status and future possibility of the flow reactor synthesis.

Utilization of Stop-flow Micro-tubing Reactors for the Development of Organic Transformations

A new reaction screening technology for organic synthesis was recently demonstrated by combining elements from both continuous micro-flow and conventional batch reactors, coined stop-flow micro-tubing (SFMT) reactors. In SFMT, chemical reactions that require high pressure can be screened in parallel through a safer and convenient way. Cross-contamination, which is a common problem in reaction screening for continuous flow reactors, is avoided in SFMT. Moreover, the commercially available light-permeable micro-tubing can be incorporated into SFMT, serving as an excellent choice for light-mediated reactions due to a more effective uniform light exposure, compared to batch reactors. Overall, the SFMT reactor system is similar to continuous flow reactors and more superior than batch reactors for reactions that incorporate gas reagents and/or require light-illumination, which enables a simple but highly efficient reaction screening system. Furthermore, any successfully developed reaction in the SFMT reactor system can be conveniently translated to continuous-flow synthesis for large scale production.

Utilization of Stop-flow Micro-tubing Reactors for the Development of Organic Transformations.

A new reaction screening technology for organic synthesis was recently demonstrated by combining elements from both continuous micro-flow and conventional batch reactors, coined stop-flow micro-tubing (SFMT) reactors. In SFMT, chemical reactions that require high pressure can be screened in parallel through a safer and convenient way. Cross-contamination, which is a common problem in reaction screening for continuous flow reactors, is avoided in SFMT. Moreover, the commercially available light-permeable micro-tubing can be incorporated into SFMT, serving as an excellent choice for light-mediated reactions due to a more effective uniform light exposure, compared to batch reactors. Overall, the SFMT reactor system is similar to continuous flow reactors and more superior than batch reactors for reactions that incorporate gas reagents and/or require light-illumination, which enables a simple but highly efficient reaction screening system. Furthermore, any successfully developed reaction in the SFMT reactor system can be conveniently translated to continuous-flow synthesis for large scale production.