Annular Reactor Research Articles

Formation of odorant haloanisoles and variation of microorganisms during microbial O-methylation in annular reactors equipped with different coupon materials

Taste and odor (T & O) issues in drinking water have become serious problems which cannot be ignored by customers. Several studies have confirmed that microbes in water can biotransform halophenols (HPs) to haloanisoles (HAs) with earthy and musty flavors via microbial O-methylation. In this paper, the formation of 2-chloroanisole (2-CA), 2,4-dichloroanisole (2,4-DCA), 2,4,6-trichloroanisole (2,4,6-TCA), 2,3,6-trichloroanisole (2,3,6-TCA) and 2,4,6-tribromoanisole (2,4,6-TBA), and the microbial variation during the microbial O-methylation were investigated in annular reactors (ARs) with three coupon materials. For precursors, 42.5% of 2-CP and 68.9% of 2,4-DCP decayed during the reaction. Among the five HAs, the formation rate constant followed an order of 2,4,6-TCA > 2-CA > 2,4,6-TBA > 2,4-DCA ~ 2,3,6-TCA, while [HA]max followed a totally opposite one. The simulated flow velocity had no significant effect (p > 0.05) on HA formation. Ductile iron (DI) AR could produce more HAs than stainless steel (SS) and polyvinyl chloride (PVC) ARs. The final HA molar concentration followed an order of 2,3,6-TCA > 2,4-DCA > 2,4,6-TBA ~ 2,4,6-TCA > 2-CA, which might be explained by multiple factors including HP's dissociation degree, halogen atom's steric hindrance and specificity of HP O-methyltransferases. During the reaction, the microbial biomass dramatically increased 6.8–9.0 times in bulk water but dropped significantly on coupon biofilms. The effect of HPs significantly changed the bacterial communities on coupon in terms of composition and diversity, and declined the relative abundance of HA-producing bacteria, while fungi and their HA-producing genus showed better resistance ability towards HPs. By using Pearson correlation analysis, a significant correlation (p = 0.0003) was found between [HA]max and initial coupon biofilm biomass. Finally, a linear relationship was established between initial total biomass and HA formation potential.

Numerical simulation of the disinfection performance in an annular reactor with different internal configurations

The flow, radiation intensity and concentration of microorganisms in three UV reactors are simulated using an integrated mathematical model for UV disinfection. All governing equations are solved using the commercial CFD software ANSYS Fluent. The effect of internal configuration on the disinfection level in the reactor is discussed in detail. There exists a relatively strong recirculation in the lower part of the U-type reactor. The two baffled reactors improve the mixing of microorganisms. The longitudinal baffled reactor can achieve the highest disinfection level. It is recommended that the arrangement of baffle should produce a longer flow path.

CaRMeN: An Improved Computer-Aided Method for Developing Catalytic Reaction Mechanisms

The software tool CaRMeN (Catalytic Reaction Mechanism Network) was exemplarily used to analyze several surface reaction mechanisms for the combustion of H2, CO, and CH4 over Rh. This tool provides a way to archive and combine experimental and modeling information as well as computer simulations from a wide variety of sources. The tool facilitates rapid analysis of experiments, chemical models, and computer codes for reactor simulations, helping to support the development of chemical kinetic models and the analysis of experimental data. In a comparative study, experimental data from different reactor configurations (channel, annular, and stagnation flow reactors) were modeled and numerically simulated using four different catalytic reaction mechanisms from the literature. It is shown that the software greatly enhanced productivity.

Selecting the best piping arrangement for scaling-up an annular channel reactor: An experimental and computational fluid dynamics study

This study is focused on the selection of the best piping arrangement for a pilot scale annular channel reactor intended for the remediation of waters and wastewaters. Two annular channel reactors composed of a single UV lamp and distinct piping arrangements were considered: (i) a novel reactor with tangential inlet/outlet pipes – the FluHelik reactor, and (ii) a conventional Jets reactor. These two reactors were manufactured at lab scale and characterized in terms of residence time distribution (RTD), radiant power and ability to degrade aqueous solutions spiked with a model compound – 3-amino-5-methylisoxazole (AMI) – by H2O2/UVC and UVC processes. Computational fluid dynamics (CFD) simulations were used to assess the hydrodynamics, RTD and UV radiation intensity distribution of both reactors at pilot scale. In general, experimental results at lab scale revealed quite similar RTDs, radiant powers and AMI degradation rates for both reactors. On the other hand, CFD simulations at pilot scale revealed the generation of a helical motion of fluid around the UVC lamp in the FluHelik reactor, inducing: (i) a longer contact time between fluid particles and UV light, (ii) more intense dynamics of macromixing as a result of larger velocity gradients, turbulent intensities and dispersion of RTD values around the peak, and (iii) a more homogeneous UV radiation distribution. In addition, the design of the FluHelik reactor can favor the implementation of various reactors in series, promoting its application at industrial scale. The FluHelik reactor was chosen for scaling-up. A pre-pilot scale treatment unit containing this reactor was constructed and its feasibility was proven.

Spatially resolved abundances of antibiotic resistance genes and intI1 in wastewater treatment biofilms.

Attached growth bioprocesses that use biofilms to remove organic matter or nutrients from wastewater are known to harbor antibiotic resistance genes (ARGs). Biofilms in these processes are spatially heterogeneous, but little is known about depth stratification of ARGs in complex, mixed culture biofilms. To address this knowledge gap, we used an experimental approach combining cryosectioning and quantitative polymerase chain reaction to quantify the spatial distribution of three ARGs (sul1, ermB, and qnrS) and the class 1 integron-integrase gene intI1 in biofilms from a lab-scale rotating annular reactor fed with synthetic wastewater. We also used high throughput 16S ribosomal RNA (rRNA) gene sequencing to characterize community structure with depth in biofilms. The ARG sul1 and the integron-integrase gene intI1 were found in higher abundances in upper layers of biofilm near the fluid-biofilm interface than in lower layers and exhibited significant correlations between the distance from substratum and gene abundances. The genes ermB and qnrS were present in comparatively low relative abundances. Microbial community structure varied significantly by date of sampling and distance from the substratum. These findings highlight the genetic and taxonomic heterogeneity with distance from substratum in wastewater treatment biofilms and show that sul1 and intI1 are particularly abundant near fluid-biofilm interfaces where cells are most likely to detach and flow into downstream portions of treatment systems and can ultimately be released into the environment through effluent.

Study of an Annular Photoreactor with Tangential Inlet and Outlet. II. The UV/H2O2 Reactive Flow

AbstractThe concentration profiles of species involved in the degradation of phenol by an advanced oxidation process (AOP) are modeled by a computational fluid dynamics tool in an annular reactor whose fluid dynamics was the object of a previous study. The reactive flow was fully described together with the radiation field and the kinetic model, which encompasses large kinetic constants such as 1010 L mol−1s−1. Phenol degradation can be simulated by using relaxation factors of at least 1012 kg m−3s−1. The hydroxyl radical concentration profile depends on the radiation field, assessed by the discrete ordinate and the discrete transfer methods. Phenol can be completely degraded along the reactor. A centrifugal effect was observed, with higher concentrations of degradation products along the inner wall at the reactor outlet.

Degradation of thiophanate-methyl fungicide by photo-Fenton process using lab-scale annular and solar tubular reactors

In this work, thiophanate-methyl fungicide was degraded by the homogeneous photo-Fenton process using lab-scale annular and solar tubular reactors. A UV light was used as artificial irradiation source in the lab-scale reactor. The influence of hydrogen peroxide (H2O2) dosage and initial pollutant concentration on the process efficiency was investigated. Degradation efficiency of thiophanate-methyl fungicide was monitored by measuring the total organic carbon (TOC). The results revealed that the variable H2O2 dosage showed remarkable effect on the process efficiency, whereas the fungicide concentration showed little influence. Both reactors showed similar efficiencies, reaching a fungicide mineralisation of 80% at 120 min of reaction time. Therefore, both reactors demonstrate to be effective on the thiophanate-methyl degradation from aqueous solution.

Degradation of thiophanate-methyl fungicide by photo-Fenton process using lab-scale annular and solar tubular reactors

Degradation of thiophanate-methyl fungicide by photo-Fenton process using lab-scale annular and solar tubular reactors

Photogeneration of N-Heterocyclic Carbenes: Application in Photoinduced Ring-Opening Metathesis Polymerization.

We report a method to generate the N-heterocyclic carbene (NHC) 1,3-dimesitylimidazol-2-ylidene (IMes) under UV-irradiation at 365 nm to characterize IMes and determine the corresponding photochemical mechanism. Then, we describe a protocol to perform ring-opening metathesis polymerization (ROMP) in solution and in miniemulsion using this NHC-photogenerating system. To photogenerate IMes, a system comprising 2-isopropylthioxanthone (ITX) as the sensitizer and 1,3-dimesitylimidazolium tetraphenylborate (IMesH+BPh4-) as the protected form of NHC is employed. IMesH+BPh4- can be obtained in a single step by anion exchange between 1,3-dimesitylimidazolium chloride and sodium tetraphenylborate. A real-time steady-state photolysis setup is described, which hints that the photochemical reaction proceeds in two consecutive steps: 1) ITX triplet is photo-reduced by the borate anion and 2) subsequent proton transfer takes place from the imidazolium cation to produce the expected NHC IMes. Two separate characterization protocols are implemented. Firstly, CS2 is added to the reaction media to evidence the photogeneration of NHC through formation of the IMes-CS2 adduct. Secondly, the amount of NHC released in situ is quantified using acid-base titration. The use of this NHC photo-generating system for the ROMP of norbornene is also discussed. In solution, a photopolymerization experiment is conducted by mixing ITX, IMesH+BPh4-, [RuCl2(p-cymene)]2 and norbornene in CH2Cl2, then irradiating the solution in a UV reactor. In a dispersed medium, a monomer miniemulsion is first formed then irradiated inside an annular reactor to produce a stable poly(norbornene) latex.

Scaling Up UV-Mediated Intramolecular Photodehydro-Diels–Alder Reactions Using a Homemade High-Performance Annular Continuous-Flow Reactor

Here we present a self-made annular continuous-flow reactor that can be used in the UV/vis range in an internal numbering-up manner. As a model reaction, we chose a powerful batch-scale-limited benzoannelation method, namely, an intramolecular photodehydro-Diels–Alder (IMPDDA) reaction. The scale-up potential of this particular photochemical benchmark reaction toward the preparation of macrocylic (1,7)naphthalenophanes by variation of selected flow parameters is presented.

A novel kinetic model to estimate the agglomerate diameter formed by nano-sized Titania in emulsion region of AFBPR

To predict the agglomerate diameter formed by nano-sized Titania powders (P25) in emulsion region of annular fluidization bed photocatalytic reactor (AFBPR), a kinetic model was developed based on an assumption of a target molecule only reacts on the active site of an agglomerate in illumination field. The results indicated that the agglomerate diameter was a function of bed voidage and gas velocity for a given photocatalytic oxidation. It was obvious that the agglomerate diameter decreased with increasing bed voidage, and decreased along the heighten of fluidized bed, which were confirmed by the experimental results. The agglomerate size decreased with gas velocity increased, validated by the estimated data of force model. Finally, the veracity of kinetic model was validated by variation of gaseous compound types and their concentrations, which suggested that this kinetic model was feasible for photocatalytic oxidation of gaseous pollutants. This investigation highlights the novel method to describe the relationship between agglomerate diameter distribution formed in emulsion region of AFBPR and photocatalytic reactivity.

Steam conversion of C2-C4 alkanes in a microchannel reactor

Steam reforming of C2-C4 alkanes was studied in annular catalytic reactor under atmospheric pressure over Rh-(La2O3, BaO)-Al2O3 catalysts. Effects of temperature have been compared for different residence time. Concentrations of the products of chemical reactions in the outlet gas mixture are measured at different temperatures of reactor. It was found that the catalyst has good performance and provide equilibrium product distribution at GHSV = 30000–55000 h−1.

Effects of chlorination/chlorine dioxide disinfection on biofilm bacterial community and corrosion process in a reclaimed water distribution system

In this work, reclaimed water treated with sodium hypochlorite (NaClO) or chlorine dioxide (ClO2) at 1, 2, and 4 mg/L was operated successively for 30 days respectively, in annular reactors with new cast iron coupons, corresponding to stages I (days 0–30), II (days 31–60), and III (days 61–90). The Illumina HiSeq 2500 sequencing platform was used to analyze the bacterial community composition, scanning electron microscopy and X-ray diffraction analyses were conducted to characterize corrosion scales, and the weight loss method was served to determine the general corrosion rate. Results reveal the precise disinfection effect on biofilm bacteria to be dose dependent and species specific. In stage I, disinfection caused a reduction in the number of operational taxonomic units, but, had little effect on biofilm composition. In stage II, NaClO and ClO2 induced a reduction of Proteobacteria proportion, but increased the dominance of Firmicutes; the diminished Proteobacteria in NaClO test mainly included Gammaproteobacteria, while, that in ClO2 test mainly included the Gammaproteobacteria and Betaproteobacteria. In stage III, Firmicutes presented a certain resistance to NaClO and ClO2 as the accumulation of corrosion scales. Results also indicated that disinfection enhanced the corrosion process, and the promoting effect of ClO2 was more pronounced than that of NaClO. Moreover, this promoting effect was more obvious in stage I than that in the latter two stages. The strong oxidization effect associated with disinfection in stage I was the dominant factor promoting corrosion, whereas, the bacterial community also played a crucial role in stages II and III.

Multi-Parameter Laser Imaging Reveals Complex Microscale Biofilm Matrix in a Thick (4,000 μm) Aerobic Methanol Oxidizing Community

Although methanol has frequently been used as an inexpensive supplementary carbon source to support treatment processes, knowledge of the resultant microbial biofilms, their 3D architecture, microenvironments, exopolymer chemistry and populations remains limited. We supplied methanol as a supplementary carbon source to biofilms developing in rotating annular reactors. Analysis of circulation waters (1.0 l d−1) indicated that dissolved organic carbon was reduced by 25%, NO3-nitrogen by 95%, and total phosphorus by 70%. Analyses of populations using culture based techniques and fluorescence in situ hybridization indicated enrichment of nitrifiers, denitrifiers, and methylotrophic bacteria relative to reference biofilms not receiving methanol. The biofilms that developed were up to 4,000 μm thick. Staining with fluor conjugated lectins in combination with nucleic acid stains, revealed the presence of discrete bacterial cells inside complex globular polymeric structures. These structures were in turn surrounded by an interstitial polymer containing a variety of bacterial cell types. The globular structures bound FITC-conjugated lectins, from Canavalia ensiformis and Ulex europeaus. The FITC-lectin of Phaseolus vulgaris bound the surface of the globular structures and more generally within the matrix. Chemical analyses of the polymer paralleled the results of lectin analyses indicating that the dominant neutral sugars were glucose, galactose, mannose, rhamnose, with fucose and ribose as minor constituents. Amino sugars were not detected. Dual channel imaging with pH sensitive probes indicated that pH gradients from pH 4 to 7 occurred across the globular microcolonies. Critically for the maintenance of aerobic conditions throughout the thick biofilm it was extensively penetrated by a fine fissure network revealed by the location of fluorescent latex microbeads as detected by confocal laser scanning microscopy. Microelectrode studies confirmed the absence of any detectable Eh gradients within the biofilm. However, mobility of various size-fractionated fluorescent probes indicated that the basal region was only penetrated by the lowest molecular weight probes with a hydrated radius of 2.2 nm or less. These observations indicate the selection of a unique, thick (>4,000 μm) microbial community in which a self-organized architecture promotes the maintenance of optimal conditions and metabolism throughout the biofilm community.

Fabrication of the annular photocatalytic reactor using large-sized freestanding titania-silica monolithic aerogel as the catalyst for degradation of glyphosate

A facile one pot method has been applied to fabricate large-sized freestanding titania-silica monolithic aerogels (TSMA). The obtained TSMA was characterized by scanning electron micrograph (SEM), Energy dispersive spectrometer (EDS), X-ray powder diffraction (XRD) and nitrogen adsorption measurements. SEM results show the TSMA has bicontinuous inner structure and large macropores (through-pores), which are favorable for the liquid infiltration. XRD results demonstrate the TSMA is anatase and nitrogen adsorption results reveal its high specific surface area of 445.9 m2/g. To maximize the catalytic activity of the as-prepared TSMA, an annular photocatalytic reactor has been specially designed and fabricated. With the apparatus, the as-prepared TSMA exhibited outstanding catalytic performance, which degraded glyphosate completely within 180 min of photocatalytic reaction. The kinetic rate (k value) of the photocatalytic reaction reaches 0.0242 min−1. Ion chromatography results indicate that glyphosate was mainly mineralized to inorganic ions such as PO43− and NO3−, etc.

Photocatalytic treatment of petroleum industry wastewater using recirculating annular reactor: comparison of experimental and modeling

In this study, the treatment of petroleum wastewater has been investigated by applying heterogeneous photocatalytic process using a recirculating annual reactor. An attempt has been made to study the effect of operating parameters such as TiO2 load, initial concentration of the pollutant, emitted photonic flux, and pH of the solution. The degradation efficiency of toluene and benzene, as target molecules, was studied. In fact, result showed that the toluene is better degraded alone than when it is in a mixture. The rate of elimination of toluene separately was 89.5%, while it was 76.19 and 79.55% in the binary (toluene/benzene) and the ternary mixtures (toluene/benzene/xylene), respectively. Moreover, the mineralization of the solution decreased more rapidly when toluene was pure with a rate of 83.13% compared to binary and ternary mixtures. A mathematical model is proposed taking into account the parameters influencing the process performances. The mass transfer step, the degradation, and the mineralization kinetics of the pollutants were defined as model parameters. To build the model, mass balances are written in bulk region and catalyst phase (solid phase). The degradation mechanism on solid phase is divided in two stages. Firstly, the removal of toluene gives an equivalent intermediate (EI). Secondly, EI is oxidized into carbon dioxide (CO2). This approach gives a good agreement between modeling and empirical data in terms of degradation and mineralization. It also allows for the simulation of toluene kinetics without knowing the plausible chemical pathway. A satisfactory fit with experimental data was obtained for the degradation and mineralization of toluene.

Comparative Evaluation of OpenFOAM® and ANSYS® Fluent for the Modeling of Annular Reactors

AbstractA three‐dimensional numerical model was solved for a turbulent incompressible steady flow and the discrepancies and similarities between the software OpenFOAM® and ANSYS® Fluent on the flow modeling were analyzed. The evaluation was performed for the meshing, setup, and simulation step of the modeling process. Outcomes were contrasted with experimental data to validate the fluid flow obtained with both softwares. With this aim, an experimental pulse‐response technique was applied to obtain the residence time distribution (RTD) curve to be compared with the RTD curves achieved from the modeling. Additionally, images of the tracer transport in the experimental reactor were taken, showing good agreement with the computational fluid dynamics (CFD) predictions.

Effects of phosphate-enhanced ozone/biofiltration on formation of disinfection byproducts and occurrence of opportunistic pathogens in drinking water distribution systems

The effects of ozone-biologically activated carbon (O3-BAC) treatment with various phosphate doses (0, 0.3 or 0.6 mg/L) were investigated on the formation of disinfection by-products (DBPs) and occurrence of opportunistic pathogens (OPs) in drinking water distribution systems (DWDSs) simulated by annular reactors (ARs). It was found that the lowest DBPs and the highest inactivation of OPs such as Mycobacterium spp., Mycobacterium avium, Aeromonas spp., Pseudomonas aeruginosa and Hartmanella vermiformis, occurred in the effluent of the AR with 0.6 mg/L phosphate addition. Based on the results of different characterization techniques, for the AR with 0.6 mg/L phosphate-enhanced O3-BAC treatment, dissolved organic carbon in the influent exhibited the lowest concentration and most stable fraction due to the improved biodegradation effect. Moreover, the total amount of suspended extracellular polymeric substances (EPS) in the bulk water of the AR decreased greatly, resulting in the lowest chlorine consumption and DBPs formation in the AR. In Fourier transform infrared spectra of the suspended EPS, the amide II band (1600-1500 cm−1) disappeared and the protein/polysaccharide ratio decreased remarkably, indicating the destruction of protein and a decrease in hydrophobicity. Moreover, β-sheets and α-helices in the protein secondary structures were degraded while the random coils increased sharply as phosphate addition increased to 0.6 mg/L, inhibiting microbial aggregation and hence weakening the chlorine-resistance capability. Thus, most of the OPs in suspended biofilms were more easily inactivated by residual chlorine, resulting in the lowest OPs occurrence in the effluent of the AR. Our findings indicated that enhancing the efficiency of the BAC filter by adding phosphate is a promising method for improving water quality in DWDSs.

The sensitization effect of waste toner powder in the photocatalytic degradation of surfactant sodium dodecylbenzene sulfonate over immobilized TiO2–chitosan layer under UVC and solar irradiation

The application of dye sensitized photocatalysis for the degradation of surfactant in the model wastewater has been studied. The aim was to explore the possibility of the photocatalytic activity enhancement by introducing the waste toner powder in the photocatalytic films. The development and a partial characterization of the supported catalyst were described within this study. Waste toner and commercial TiO2 powder (AEROXIDE® P25) were integrated within the matrix of chitosan molecules as a thin layer films. The developed films contain the high amount of the TiO2 (approx. 90%) which structure appeared to be intact. The efficiency of the photocatalytic films for the oxidation of the anionic surfactant dodecylbenzene sulfonate (SDBS) has been evaluated. Preliminary experiments were performed in an annular batch reactor using UVC lamp. Photocatalytic films were supported on the glass, stainless steel and waste offset printing plates. Support was made in a form of plates or rings. Further experiments were performed under artificial and natural solar irradiation whereby photocatalytic films were fixed at the bottom of reaction cell (boat shaped flow reactor). In order to estimate the reaction rate constant for SDBS degradation over irradiated photocatalytic films and to evaluate the effects of photon absorption under different irradiation conditions, a detailed kinetic model was developed. The sensitization effect of the components in toner powder due to the visible light absorption for the photocatalytic oxidation of SDBS under solar irradiation was quantified.

Turbulence accelerates the growth of drinking water biofilms

Biofilms are found at the inner surfaces of drinking water pipes and, therefore, it is essential to understand biofilm processes to control their formation. Hydrodynamics play a crucial role in shaping biofilms. Thus, knowing how biofilms form, develop and disperse under different flow conditions is critical in the successful management of these systems. Here, the development of biofilms after 4 weeks, the initial formation of biofilms within 10 h and finally, the response of already established biofilms within 24-h intervals in which the flow regime was changed, were studied using a rotating annular reactor under three different flow regimes: turbulent, transition and laminar. Using fluorescence microscopy, information about the number of microcolonies on the reactor slides, the surface area of biofilms and of extracellular polymeric substances and the biofilm structures was acquired. Gravimetric measurements were conducted to characterise the thickness and density of biofilms, and spatial statistics were used to characterise the heterogeneity and spatial correlation of biofilm structures. Contrary to the prevailing view, it was shown that turbulent flow did not correlate with a reduction in biofilms; turbulence was found to enhance both the initial formation and the development of biofilms on the accessible surfaces. Additionally, after 24-h changes of the flow regime it was indicated that biofilms responded to the quick changes of the flow regime. Overall, this work suggests that different flow conditions can cause substantial changes in biofilm morphology and growth and specifically that turbulent flow can accelerate biofilm growth in drinking water.