Exploring the maximum nitrite production rate through the granular sludge-type reactor to match the needs of anammox process realizing efficient nitrogen removal

The reliable and efficient nitrite production rate (NPR) through nitritation process is the prerequisite for the efficient running of subsequent processes, like the anammox process and the nitrite shunt. However, there has been scant research on stable and productive nitritation process in recent years. In this study, at a stable hydraulic retention time of 12.0 h and with precise and strict DO control, the upper limit of the NPR was initially investigated using a continuous-flow granular sludge reactor. The NPR of 1.69 kg/m3/d with a nitrite production efficiency of 81.97% was finally achieved, which set a record until now in similar research. The median sludge particle size of 270.0 μm confirmed the development of clearly defined granular sludge. The genus Nitrosomonas was the major ammonium oxidizing bacteria. In conclusion, this study provides valuable insights for the practical application of the effective nitritation process driving subsequent nitrogen removal processes.

Prandtl and Ohnesorge numbers dependent of ultrasonic horn energy in Newtonian liquid under batch and continuous flow

The level of knowledge on the non-thermal contribution of ultrasonic wave's energy to perform physico-chemical phenomena is one of the bottlenecks for the commercialization purposes. Under constant nominal power of transducer (Pn), the input electrical power (Pin) is less and sensitive to the medium's physical properties. This study attempts to assess the conversion of acoustic to thermal power experimentally and numerically using COMSOL Multiphysis@ for a 24 kHz horn-type sonicator through a medium without any sono-chemical effect. Single- and homogeneous two-phase Newtonian mixtures of sunflower oil and water (o/w) with a relatively wide range of density (914-998 kg/m3) and viscosity (0.5-63.5 mPa.s) were irradiated in a lab-scale vessel (1 L) under batch and continuous flow configuration. The direct influence of Pn (80-400 W) and o/w ratio (0-1) on temperature rise and subsequent thermo-physical properties of liquid and the indirect influence on Pin and thermal energy conversion (TEC) were investigated employing calorimetric method. A new engineering concept including a power factor correlation was proposed and validated for prediction of Pin as a function of liquid space velocity (ϑ), temperature, Prandtl (Pr) and Ohnesorge (Oh) dimensionless groups. The results showed that under constant temperature and Pn, increasing Pr and Oh increased Pin with a similar trend for both modes of operation. An increase in temperature directly led to a decrease in Pin with a power factor closed to "-1". The Pin in continuous flow was higher compared to batch configuration at similar temperature, liquid properties, and Pn. This effect was more significant with increasing ϑ. An increase in ϑ at constant Pn led to a decrease in the inlet/outlet temperature difference in continuous flow and an increase in Pin. Increasing Pn resulted in higher TEC for both configurations; however, TEC was relatively lower in continuous flow than batch configuration indicating more efficient sonication in continuous flow.

Pickering emulsion biocatalysis: Bridging interfacial design with enzymatic reactions

Non-homogeneous enzyme-catalyzed systems are more widely used than homogeneous systems. Distinguished from the conventional biphasic approach, Pickering emulsion stabilized by ultrafine solid particles opens up an innovative platform for biocatalysis. Their vast specific surface area significantly enhances enzyme-substrate interactions, dramatically increasing catalytic efficiency. This review comprehensively explores various aspects of Pickering emulsion biocatalysis, provides insights into the multiple types and mechanisms of its catalysis, and offers strategies for material design, enzyme immobilization, emulsion formation control, and reactor design. Characterization methods are summarized for the determination of drop size, emulsion type, interface morphology, and emulsion potential. Furthermore, recent reports on the design of stimuli-responsive reaction systems are reviewed, enabling the simple control of demulsification. Moreover, the review explores applications of Pickering emulsion in single-step, cascade, and continuous flow reactions and outlines the challenges and future directions for the field. Overall, we provide a review focusing on Pickering emulsions catalysis, which can draw the attention of researchers in the field of catalytic system design, further empowering next-generation bioprocessing.

Fabrication and characterization of microporous soft templated photoactive 3D materials for water disinfection in batch and continuous flow

Water cleaning can be provided in batch mode or in continuous flow. For the latter, some kind of framework must withhold the cleaning agents from washout. Porous structures provide an ideal ratio of surface to volume for optimal access of the water to active sites and are able to facilitate rapid and efficient fluid transport to maintain a constant flow. When functionalized with suitable photoactive agents, they could be used in solar photocatalytic disinfection. In this study, we have used the sugar cube method to fabricate PDMS-based materials that contain three different classes of photosensitizers that differ in absorption wavelength and intensity, charge as well as in ability to generate singlet oxygen. The obtained sponges are characterized by scanning electron microscopy and digital microscopy. Archimede's method was used to measure porosity and density. We show that the materials can absorb visible light and generate Reactive Oxygen Species (ROS) that are required to kill bacteria. The disinfection ability was tested by examining how irradiation time and operation mode (batch vs. flow) contribute to the performance of the material. The current strategy is highly adaptable to other (medium) pressure-driven flow systems and holds promising potential for various applications, including continuous flow photoreactions.

Effects of the low-speed continuous infusion catheter technique on double-lumen central venous catheters: A randomized controlled trial

BACKGROUND

Central venous catheters are widely used in clinical practice, and the incidence of central venous catheter occlusion is between 25 % and 38 %. The turbulence caused by the pulsatile flushing technique is harmful to the vascular endothelium and may lead to phlebitis. The low-speed continuous infusion catheter technique is a new type of continuous infusion that ensures that the catheter is always in a keep-vein-open state by continuous low-speed flushing; hence, avoiding the problem of catheter occlusion.

OBJECTIVE

To investigate the effectiveness of the low-speed continuous infusion catheter technique and the routine care of double-lumen central venous catheters.

DESIGN

This was a prospective, randomized, controlled, open-label trial.

SETTING

Patients were recruited from 14 medical institutions in China between February and June 2023.

PARTICIPANTS

In total, 251 patients were recruited, with 125 in the intervention group and 126 in the control group.

METHODS

Patients who used double-lumen central venous catheters for infusion treatment were selected, and those who met the sampling criteria were randomly divided into intervention and control groups using the random envelope method. The intervention group used the low-speed continuous infusion catheter technique to maintain catheter patency, whereas the control group used routine care with a trial period of 7 days. The primary outcome was the occlusion rate. The secondary outcomes included nursing satisfaction and complication rates of the two groups.

RESULTS

After 7 days, the rate of catheter occlusion was 28.0 % (35/125, 95 % confidence interval (CI):0.203, 0.367) in the intervention group and 53.97 % (68/126, 95 % CI: 0.449-0.629) in the control group, with a statistically significant difference (χ2 = 17.488, p < 0.001); at 3 days of intervention, the rate of catheter blockage was 8.0 % (10/125, 95 % CI: 0.039-0.142) in the intervention group and 23.8 % (30/126, 0.167-0.322) in the control group, with a statistically significant difference (χ2 = 11.707, p < 0.001). Nurse satisfaction was significantly higher in the intervention group (115/125, 92.0 %, 95 % CI: 0.858-0.961) than in the control group (104/126, 82.54 %, 95 % CI: 0.748-0.887) (χ2 = 5.049, p = 0.025). There were no statistically significant complication rates in either group (p = 0.622).

CONCLUSION

The low-speed continuous infusion catheter technique helps maintain catheter patency, improves nurse satisfaction, and provides a high level of safety.

REGISTRATION

Chinese Clinical Trial Registry (ChiCTR2200064007, www.chictr.org.cn). The first recruitment was conducted in February. https://www.chictr.org.cn/showproj.html?proj=177311.

Innovative determination of the specific anammox activity for anammox sludge from continuous flow reactors: A comparison between continuous flow test and batch test

A novel method for measuring specific anammox activity (SAA) was proposed based on continuous flow tests to accurately determine the SAA of anammox sludge from continuous flow reactors, resolving the challenges of inaccurate SAA assessment caused by substrate shock to anammox bacteria. Results showed SAA of expanded granular sludge bed sludge via batch tests (0.101 ± 0.018 g-N·g-VSS-1·d-1) was lower than continuous flow tests (0.206 ± 0.010 g-N·g-VSS-1·d-1) (p < 0.05), highlighting the impact of substrate shock. Conversely, SAA of sequencing batch reactor sludge assessed via batch tests (0.878 ± 0.008 g-N·g-VSS-1·d-1) was higher than continuous flow tests (0.809 ± 0.005 g-N·g-VSS-1·d-1) (p < 0.01), attributed to endogenous denitrification. The advantages of continuous flow tests over batch tests included milder feeding way, stricter anaerobic conditions, and minimal sampling impact on system. Our study contributes to more accurate measurements of SAA of anammox sludge from continuous flow reactors, favoring long-term robust operation of anammox reactors.

Application of an Oscillatory Plug Flow Reactor to Enable Scalable and Fast Reactions in Water Using a Biomass-Based Polymeric Additive

The utilization of water as a sustainable reaction medium has important advantages over traditional organic solvents. Hydroxypropyl methylcellulose has emerged as a biomass-based polymeric additive that enables organic reactions in water through hydrophobic effects. However, such conditions imply slurries as reaction mixtures, where the efficacy of mass transfer and mixing decreases with increasing vessel size. In order to circumvent this limitation and establish an effectively scalable platform for performing hydroxypropyl methylcellulose-mediated aqueous transformations, we utilized oscillatory plug flow reactors that feature a smart dimensioning design principle across different scales. Using nucleophilic aromatic substitutions as valuable model reactions, rapid parameter optimization was performed first in a small-scale instrument having an internal channel volume of 5 mL. The optimal conditions were then directly transferred to a 15 mL reactor, achieving a three-fold scale-up without re-optimizing any reaction parameters. By precisely fine-tuning the oscillation parameters, the system achieved optimal homogeneous suspension of solids, preventing settling of particles and clogging of process channels. Ultimately, this resulted in a robust and scalable platform for performing multiphasic reactions under aqueous conditions.

Full-scale upgrade activated sludge to continuous-flow aerobic granular sludge: Implementing microaerobic-aerobic configuration with internal separators

Aerobic granular sludge (AGS) has been successfully used in sequencing batch reactors. However, their application to existing continuous-flow systems remains challenging. In this study, a novel microaerobic-aerobic configuration with internal separators was implemented in a full-scale municipal wastewater treatment facility with a nominal capacity of 2.5 × 104 m3 d-1. Sludge characteristics, pollutant removal and associated pathways, shifts in the microbial community, and underlying granulation mechanisms were investigated. Following a two-month operation period, the transition from flocculent-activated sludge to well-defined AGS with distinct boundaries and compact structures was successfully achieved. The average size of sludge increased from 31.9 to 138.5 μm, with granules larger than 200 μm constituting 28.9 % of the total sludge and SVI30 averaging 51.4 ± 8.2 mL g-1. The 95th percentile effluent COD, NH4+-N, and TN concentrations were 35.0, 1.2, and 13.3 mg L-1, respectively. The primary pathways for pollutant removal were identified as simultaneous nitrification, denitrification, and phosphorus removal within the microaerobic tanks. The enrichment of denitrifying phosphorus-accumulating organisms, including Hydrogenophaga, Accumulibacter, Azospira, Dechloromonas, and Pseudomonas, provides an essential microbial foundation. Furthermore, computational fluid dynamics modeling revealed that the incorporation of internal separators in aerobic tanks induced shifts in the flow pattern, transitioning from a single-circulation cell to multiple vortical cells. This alteration amplified the local velocity gradients, generating the required shear forces to drive granulation. Moreover, mass balance analysis revealed that the microaerobic and aerobic tanks operated under feast and famine conditions, respectively, creating a microbial selection pressure that favored granulation. This process eliminates the need for external clarifiers, resulting in a footprint reduction of 38.2 % and one-third energy savings for sludge reflux. This study offers valuable insights into the application of continuous-flow AGS to upgrade existing activated sludge systems with limited retrofitting requirements.

Construction of a stable S-scheme NiSnO3/g-C3N4 heterojunction on activated carbon fibre for the degradation of glyphosate in water under flow condition

Creating light-harvesting heterojunctions as a photocatalyst is critical for efficiently treating organics-laden wastewater. Yet the materials stabilization and limited reusability hinder their practical applications. In this study, an S-scheme heterojunction in the Sn-based perovskite and g-C3N4 (gCN) composite, supported on an activated carbon fiber (ACF) substrate, is developed for glyphosate (GLP) degradation under water under flow conditions. The reusable NiSnO3-gCN/ACF photocatalyst was synthesized using a simple wet impregnation and calcination method. The supported photocatalyst achieved 99% GLP-removal at 4 mL/min water flowrate and 1.25 g/m2 of photocatalyst loading in ACF. The photocatalyst showed a stable structure and repeat photocatalytic performance across 5 cycles despite prolonged visible light exposure under flow conditions. The materials stability is attributed to the effective dispersion of NiSnO3-gC3N4 in ACF, preventing the photocatalyst from elution in water flow. Radical trapping experiment revealed the superoxide and hydroxyl radicals as the primary reactive species in the GLP-degradation pathway. A plausible S-scheme mechanism was proposed for heterojunction formation, based on the high resolution deconvoluted spectra of X-ray photoelectron spectroscopy and the radical trapping experimental results. The inexpensive Sn-based perovskite synthesized in this study is indicated as an alternative to Ti-based perovskites for wastewater remediation application.

Polarisation and rheology characterisation of monoolein/water liquid crystal dynamical behaviour during high-viscosity injector extrusion

HYPOTHESIS

The use of monoolein/water mixtures in serial crystallography experiments using high-viscosity injectors (HVI) results in significant departures from equilibrium behaviour. This is expected to include changes in phase, viscosity, and associated flow behaviour. It should be possible to detect these changes, in-situ, using a combination of polarisation and rheology characterisation techniques.

EXPERIMENTS

A systematic study was performed using monoolein, varying the water content to create a range of mixtures. Injection induced phase changes within the HVI flow were established using real-time cross-polarization measurements. Dynamic flow characteristics and viscosity was characterized by particle tracking and rheology.

FINDINGS

HVI injection induces deformation and phase changes within monoolein (MO)/water mixtures which can be detected through variations in the transmitted intensity during in-situ polarisation studies. The heterogeneity of the extruded sample results in a highly viscous cubic phase in the central region of the stream and a less viscous lamellar-rich phase at the edges adjacent to the walls. The extent of these variations depends on sample composition and injection conditions. Shear-thinning behaviour and increasing heterogeneity in the vicinity of the capillary walls under dynamic flow conditions. This is the first report observing injection induced dynamical behaviour in MO/water mixtures under realistic flow conditions.

Utilization of palm residues for biochar production using continuous flow pyrolysis unit

Biochar is a carbonaceous solid substance produced by heating biomass without using air. This research aimed to create and evaluate local carbonization pyrolysis using a screw conveyor and filtration equipment. Date palm frond (DPF) biochar was studied and tested at pyrolysis temperatures of 320, 390, and 460 °C, as well as feeding rates of 60, 90, and 120 kg/h. The physicochemical parameters of DPF biochar were evaluated using SEM and FTIR. When the pyrolysis temperature was raised from 320 to 450 °C, and the feed rates were reduced from 120 to 60 kg/h, the biochar yield of DPF and volatiles fell. At 460 °C and 60 kg/h, the maximum ash and fixed carbon content were 11.73 and 77.61 %, respectively. As the feed rate decreased and the temperature increased, the H and O values (1.96 and 2.62 %, respectively) of DPF biochar decreased considerably; the C and N values (83.60 and 0.24 %, respectively) trended in opposite directions. The BET surface area and pore volume increased as a result of the micropore surface area and volume at higher temperatures and lower feeding rates, but water holding capacity increased from 6.04 gwater/10 g at 320 °C to 6.78 gwater/10 g at 390 °C (60 kg/h). The results showed that the heating temperature increased and the feeding rate decreased; phosphorus) P(and magnesium (Mg) increased significantly, whereas the levels of potassium (K) and calcium (Ca) showed a non-significant increase. Furthermore, as the pyrolysis temperature increased, pH and EC increased from 7.90 to 10.96 and 2.91 to 4.25 dSm-1, respectively, while CEC declined; however, there were no significant changes in CEC. DPF biochar demonstrated enhanced macro porosity and surface area at 460 °C and 60 kg/h, making it acceptable for agricultural use as a soil supplement.

Nanoprecipitation through solvent-shifting using rapid mixing: Dispelling the Ouzo boundary to reach large solute concentrations

HYPOTHESIS

The addition of a non-solvent to a solute in good solvent solution leads to nanoprecipitation, which is the spontaneous formation of nanodomains. Yet, increasing solute concentration usually leads to the formation of macrodomains that quickly separate into a bulk phase, which is a severe process limitation. The corresponding concentration threshold, often termed as the Ouzo boundary, remains a mystery that could find its origin in the complex interplay between nanoprecipitation and mixing.

EXPERIMENTS

We performed a systematic investigation of nanoprecipitation thermodynamics and kinetics as well as its interplay with mixing hydrodynamics for the hexadecane-acetone-water system, in the presence of the non-ionic C16EO8 surfactant. The binodal curve and its underlying tie-lines were obtained using Raman spectroscopy, allowing the computation of the spinodal curve. Kinetics were probed using a continuous flow setup that combines two sequential rapid mixers. The impact of mixing efficiency was probed systematically by varying the oil concentration for respectively slow and rapid mixing, while the uncoupling from mixing and nanoprecipitation was quantified by modifying systematically the flow rate in a continuous flow approach.

FINDINGS

We elucidate the nature of the Ouzo boundary that marks the maximal solute concentration leading to nanoobjects. Rather than a thermodynamic boundary, as evidenced by its uncorrelation to the spinodal curve, it results from the coupling of nanoprecipitation and mixing when both processes occur within the same time range, leading to heterogeneous conditions and the escape of some objects to the macroscale. Increasing the solute concentration speeds up nanoprecipitation and thus requires increasingly faster mixing times to uncouple both processes. Accordingly, if the mixing efficiency is large enough, it is possible to dispel the Ouzo boundary and reach very large solute concentrations. Implementing rapid mixing strategies in continuous flow approaches is thus the solution to overcome the most stringent condition of nanoprecipitation and open the way to scale-up, while also providing efficient means to probe its fast mechanism. Overall, the simultaneous control of hydrodynamics and physical chemistry is thus key to boost up the Ouzo effect.

A continuous flow mode with a scalable tubular reactor for the green preparation of stable alkali lignin nanoparticles assisted by ultrasound

Lignin nanoparticles (LNPs) have become a hot topic recently because of their improved physicochemical properties and the excellent integration into various industrial sectors compared to lignin. However, the green large-scale production of stable LNPs severely restricts the high-value applications of LNPs. In this work, a simple and potentially scalable continuous-flow mode setup with a tubular flow reactor was designed for the green preparation of stable alkali LNPs assisted by ultrasound. When the flow rates of lignin solution and nitric acid solution were 8.00 mL/min and 2.67 mL/min respectively, and the length of the tube was 5.5 m, the average residence time of mixed solution was 62.2 s in the tubular reactor. Spheroid nanoparticles with an average size of 97.2 nm were obtained under this optimized condition. Furthermore, the results showed a better control of the mixing compared to the batch process, resulting in a homogeneous distribution of smaller particle sizes thus improving stability and UV-blocking properties. This is attributed to the better mixing and excellent mass transfer characteristics in the tube, which provides favorable conditions for the full contact and uniform dispersion of the mixed solution. More importantly, continuous flow mode makes it possible to prepare LNPs with excellent physicochemical properties on a large scale, which will bring great opportunities for the industrial production and application of LNPs.

Merger of Visible Light-Driven Chiral Organocatalysis and Continuous Flow Chemistry: An Accelerated and Scalable Access into Enantioselective α-Alkylation of Aldehydes

The electron donor-acceptor complex-enabled asymmetric photochemical alkylation strategy holds potential to attain elusive chiral α-alkylated aldehydes without an external photoredox catalyst. The photosensitizer-free conditions are beneficial concerning process costs and sustainability. However, lengthy organocatalyst preparation steps as well as limited productivity and difficult scalability render the current approaches unsuitable for synthesis on enlarged scales. Inspired by these limitations, a protocol was developed for the enantioselective α-alkylation of aldehydes based on the synergistic combination of visible light-driven asymmetric organocatalysis and a controlled continuous flow reaction environment. With the aim to reduce process costs, a commercially available chiral catalyst has been exploited to achieve photosensitizer-free enantioselective α-alkylations using phenacyl bromide derivates as alkylating agents. As a result of elaborate optimization and process development, the present flow strategy furnishes an accelerated and inherently scalable entry into enantioenriched α-alkylated aldehydes including a chiral key intermediate of the antirheumatic esonarimod.

Coupling physical selection with biological selection for the startup of a pilot-scale, continuous flow, aerobic granular sludge reactor without treatment interruption

This study removes two technical constraints for transitioning full-scale activated sludge infrastructure to continuous flow, aerobic granular sludge (AGS) facilities. The first of these is the loss of treatment capacity as a result of the rapid washout of flocculent sludge inventory and in turn the potential loss of nitrification during initial AGS reactor startup. The second is the physical selector design which currently is limited to either the complex sequencing batch reactor selection or sidestream hydrocyclones. Briefly, real wastewater data collected from this study suggested that by increasing the surface overflow rate (SOR) of an upflow clarifier to 10 m h ^- 1, the clarifier can be taken advantage of as a physical selector to separate flocculant sludge from AGS. Redirecting the physical selector underflow and overflow sludge to the feast and famine zones of a treatment train, respectively, can create a biological selection that not only promotes AGS formation but also safeguards the effluent quality throughout the AGS reactor startup period. This study provides a novel concept for economically implementing continuous flow AGS within existing full-scale, continuous flow treatment trains.

Recent Advances in the Multistep Continuous Preparation of Apis and Fine Chemicals

Over the last two decades, with the advent of continuous flow technologies, continuous processes have emerged as a major area in organic synthesis. In this context, continuous flow processes have been increasing in the preparation of Active Pharmaceutical Ingredients (APIs) and fine chemicals, such as complex synthetic intermediates, agrochemicals, and fragrances. Thus, the development of multi-step protocols has attracted special interest from the academic and industrial chemistry communities. In addition to the beneficial aspects intrinsically associated with continuous processes (e.g., waste reduction, optimal heat transfer, improved safety, and the possibility to work under harsh reaction conditions and with more dangerous reagents), these protocols also allow a rapid increase in molecular complexity. Moreover, in telescoped multi-step processes, isolation and purification steps are generally avoided or, if necessary, carried out in-line, presenting an important economy of time, solvents, reagents, and labor. Last, important synthetic strategies such as photochemical and electrochemical reactions are compatible with flow processes and are delivering relevant advances to the synthetic approaches. In this review, a general overview of the fundamentals of continuous flow processes is presented. Recent examples of multi-step continuous processes for the preparation of fine chemicals, including telescoped and end-to-end processes, are discussed, pointing out the possible advantages and/or limitations of each of these methodologies.

Achieving robust nitritation in a modified continuous-flow reactor: From micro-granule cultivation to nitrite-oxidizing bacteria elimination

In this study, a modified continuous-flow nitrifying reactor was successfully operated for rapid cultivation of micro-granules and achieving robust nitritation. Results showed that sludge granulation with mean size of ca. 100 µm was achieved within three weeks by gradually increasing settling velocity-based selection pressure from 0.48 to 0.9 m/hr. Though Nitrospira like nitrite-oxidizing bacteria (NOB) were enriched in the micro-granules with a ratio between ammonia-oxidizing bacteria (AOB) and NOB of 5.7%/6.5% on day 21, fast nitritation was achieved within one-week by gradually increasing of influent ammonium concentration (from 50 to 200 mg/L). Maintaining ammonium in-excess was the key for repressing NOB in the micro-granules. Interestingly, when the influent ammonium concentration switched back to 50 mg/L still with the residual ammonium of 15-25 mg/L, the nitrite accumulation efficiency increased from 90% to 98%. Experimental results suggested that the NOB repression was intensified by both oxygen and nitrite unavailability in the inner layers of micro-granules. Unexpectedly, continuous operation with ammonium in excess resulted in overproduction of extracellular polysaccharides and overgrowth of some bacteria (e.g., Nitrosomonas, Arenimonas, and Flavobacterium), which deteriorated the micro-granule stability and drove the micro-granules aggregation into larger ones with irregular morphology. However, efficient nitritation was stably maintained with extremely high ammonium oxidation potential (> 50 mg/g VSS/hr) and nearly complete washout of NOB was obtained. This suggested that smooth and spherical granule was not a prerequisite for achieving NOB wash-out and maintaining effective nitritation in the granular reactor. Overall, the micro-granules exhibited a great practical potential for high-rate nitritation.

Analyzing the impact of pulsatile flow on drug release from a single strut of a drug-eluting stent

In this study, in-vitro experiments were performed to investigate the drug release from a single strut of a drug-eluting stent with respect to the systolic-diastolic flow and the continuous flow. Regarding, a test bench comprising a single strut and agarose gel as an arterial wall model was designed. The model chosen represents a large-scaled strut of a stent, to limit the effect of the geometrical shape of the stents on the drug release results. The comparison is carried out between two continuous flow rates and a systolic-diastolic flow pattern varying between these two flow rates, with a frequency of 70 beats per minute. The stent model is a polylactic-co-glycolic acid film (50:50) loaded with 10 % diclofenac sodium. A compartment of agarose gel (1 %) and a phosphate-buffered saline solution at 37 °C are employed to mimic the arterial wall and the blood, respectively. Our results show the importance of flow type on the drug release from the stent and distribution of drug in the hydrogel, such that the pulsatility promotes an increase in the quantity of drug absorbed into the hydrogel.

Persulfate-enhanced continuous flow three-dimensional electrode dynamic reactor for treatment of landfill leachate

Compared with sequencing batch reactor, continuous flow dynamic reactors are more conducive to promotion and application. In this study, the ability of a three-dimensional (3D) electrode dynamic reactor to remove pollutants in the landfill leachate was investigated, in which landfill leachate entered through continuous flow. Either increased of current density or the decreased of flow rate was conducive to the removal of pollutants. The optimal process parameters for current density and flow rate were 16 mA cm^-2 and 0.75 L h^-1, respectively. When the current density was constant at 16 mA cm^-2 and the flow rate was kept at 0.75 L h^-1, 60.02% of total organic carbon (TOC), 96.50% of chroma, 64.98% of chemical oxygen demand (COD) and 99.46% of ammonia nitrogen (NH₃-N) were removed. The characteristic peaks of refractory organic pollutants were reduced by 97.95%. After the reaction, the biological oxygen demand (BOD)/COD was increased from 0.24 to 0.32. As one of the emerging trace organics in landfill leachate, 85.90% of ibuprofen (IBU) was removed. The results showed that the 3D electrode dynamic reactor constructed in this study could reduce the TOC, refractory trace organic pollutant, NH₃-N and chroma in the landfill leachate. The 3D electrode dynamic reactor constructed in this research has application potential in the field of landfill leachate treatment.

Efficient peroxymonosulfate activation of immobilized Fe-N-C catalyst on ceramsite for the continuous flow removal of phenol

Nowadays, developing environmentally friendly catalysts with both low cost and high efficiency was still a challenge in actual organic wastewater purification. Herein, the Fe-N-C catalyst was successfully immobilized on solid waste derived ceramsite for efficient degradation of phenol under continuous flow conditions by activating peroxymonosulfate (PMS). After the introduction of ceramsite, the microstructure of Fe-N-C catalyst was changed from granular structure to worm-like structure, promoting the dispersion of the nanoscale catalyst and providing more reactive sites. Therefore, the phenol removal rate and mineralization rate of the obtained 0.5FNNC within 30 min were up to 96.79% and 71.79%, respectively. In addition, the degradation rate of the optimal composite (0.5FNNC)/PMS system was about 4.06 times higher than that of bare Fe-N-C/PMS system. Intriguingly, the Fe ion leaching from 0.5FNNC during the degradation reaction was significantly lower than bare Fe-N-C owing to the strong catalyst-support chemical bonding. Based on electron paramagnetic resonance, quenching experiments, X-ray photoelectron spectroscopy analysis and electrochemical analysis, it was indicated that the non-radical processes (¹O₂ and high valent iron-oxo species) should be responsible for the phenol degradation. Meanwhile, the possible phenol degradation pathways were proposed, and the intermediates were evaluated for ecotoxicity by ECOSAR. Finally, a preliminary economic analysis of this process was carried out. Overall, this work would provide a new strategy for the construction of ceramsite based multi-pore composite catalysts and the large-scale application of persulfate oxidation technology in organic wastewater treatment.

Bioremediation on a chip: A portable microfluidic device for efficient screening of bacterial biofilm with polycyclic aromatic hydrocarbon removal capacity

Polycyclic aromatic hydrocarbons (PAHs) are pollutants of critical environmental and public health concern and their elimination from contaminated sites is significant for the environment. Biodegradation studies have demonstrated the ability of bacteria in biofilm conformation to enhance the biodegradation of pollutants. In this study, we used our newly developed microfluidic platform to explore biofilm development, properties, and applications of fluid flow, as a new technique for screening PAHs-degrading biofilms. The optimization and evaluation of the flow condition in the microchannels were performed through computational fluid dynamics (CFD). The formation of biofilms by PAHs-degrading bacteria Pseudomonas sp. P26 and Gordonia sp. H19, as pure cultures and co-culture, was obtained in the developed microchips. The removal efficiencies of acenaphthene, fluoranthene and pyrene were determined by HPLC. All the biofilms formed in the microchips removed all tested PAHs, with the higher removal percentages observed with the Pseudomonas sp. P26 biofilm (57.4% of acenaphthene, 40.9% of fluoranthene, and 28.9% of pyrene). Pseudomonas sp. P26 biofilm removed these compounds more efficiently than planktonic cultures. This work proved that the conformation of biofilms enhances the removal rate. It also provided a new tool to rapid and low-cost screen for effective pollutant-degrading biofilms.

Continuous antibiotic attenuation in algal membrane photobioreactor: Performance and kinetics

The attenuation of 10 mixed antibiotics along with nutrients in a continuous flow mode by four freshwater microalgae (Haematococcus pluvialis, Selenastrum capricornutum, Scenedesmus quadricauda, and Chlorella vulgaris) was examined in membrane photobioreactors (MPBRs). At lab-scale, consistent removal of both antibiotic and nutrient was shown by H. pluvialis and S. quadricauda, respectively. The system exhibited better performance with enhanced removal at HRT 24 h compared to 12 h and 48 h. The highest removal efficiency of antibiotics was observed in H. pluvialis MPBR, with the mean antibiotic removal values of 53.57%- 96.33%. Biodegradation was the major removal pathway of the antibiotics in the algal-MPBR (AMPBR), while removal by bioadsorption, bioaccumulation, membrane rejection, and abiotic was minor. Then, the bacterial feature was studied and showed significant influence from system hydrodynamics. The kinetics of continuous flow antibiotic removal followed Stover-Kincannon and Grau second-order models, which revealed great potential of AMPBR to withstand antibiotic load. The latter coupled with the computational fluid dynamic simulation was successfully applied for the residual antibiotic prediction and potential system optimization. Overall, these results provide an important reference for continuous flow antibiotic removal using AMPBR.

Application of titanium dioxide immobilized on a cellulosic material for the photocatalytic degradation of Acid Black 24 dye in a continuous flow cascade reactor

The aim of this work is the study of the photocatalytic degradation of Acid Black 24 dye (AB24), in a continuous flow cascade reactor, using titanium dioxide (TiO2) immobilized on a cellulosic material. The results obtained demonstrated a synergistic effect of the two phenomena adsorption and photocatalysis. The effects of various parameters that affect the dye removal efficiency were investigated. The best photocatalytic degradation yield of AB24 molecules is obtained in acidic medium because of the strong attraction between the positively charged catalyst and the anionic dye molecules. The optimum times for obtaining the best yields depend on the initial concentration of the dye, the volume of the treated solution, and the feed rate of the reactor. In addition, reusing the catalytic material several times is technically possible; this can decrease the cost of treatment for a possible industrial scale application.

Quantitative assessment of regional lung ventilation in emphysematous mice using hyperpolarized 129Xe MRI with a continuous flow hyperpolarizing system

BACKGROUND

Lung ventilation function in small animals can be assessed by using hyperpolarized gas MRI. For these experiments a free breathing protocol is generally preferred to mechanical ventilation as mechanical ventilation can often lead to ventilation lung injury, while the need to maintain a gas reservoir may lead to a partial reduction of the polarization.

PURPOSE

To evaluate regional lung ventilation of mice by a simple but fast method under free breathing and give evidence for effectiveness with an elastase instilled emphysematous mice.

ANIMAL MODEL

Emphysematous mice.

MATERIALS AND METHODS

A Look-Locker based saturation recovery sequence was developed for continuous flow hyperpolarized (CF-HP) ¹²⁹Xe gas experiments, and the apparent gas-exchange rate, k', was measured by the analysis of the saturation recovery curve.

RESULTS

In mice with elastase-induced mild emphysema, reductions of 15-30% in k' values were observed as the results of lesion-induced changes in the lung.

DATA CONCLUSION

The proposed method was applied to an emphysematous model mice and ventilation dysfunctions have been approved as a definite decrease in k' values, supporting the usefulness for a non-invasive assessment of the lung functions in preclinical study by the CF-HP ¹²⁹Xe experiments.

Microwave-assisted continuous flow phytosynthesis of silver nanoparticle/reduced graphene oxide composites and related visible light catalytic performance

The creation of an environmentally friendly synthesis method for silver nanomaterials (AgNPs) is an urgent concern for sustainable nanotechnology development. In the present study, a novel straightforward and green method for the preparation of silver nanoparticle/reduced graphene oxide (AgNP/rGO) composites was successfully developed through the combination of phytosynthesis, continuous flow synthesis and microwave-assistance. Oriental persimmon (Diospyros kaki Thunb.) extracts were used as both plant reducing and capping agents for fast online synthesis of AgNP/rGO composites. The experimental parameters were optimized and the morphologies of the prepared materials were investigated. The characterization results reveal that spherical AgNPs were quickly synthesized and uniformly dispersed on rGO sheets using the proposed online system. Fourier transform infrared spectroscopy analysis confirmed that phenols, flavonoids, and other substances in the plant extracts played a decisive role in the synthesis of AgNP/rGO composites. Using sodium borohydride (NaBH₄) degradation of p-nitrophenol (4-NP) as a model, the catalytic activity of the prepared AgNP/rGO materials was evaluated. The complete degradation of 4-NP was achieved within 12 min through the use of AgNP/rGO materials, and the composite had a much better catalytic activity than the bare AgNPs and rGO had. Compared with the conventional chemical method, our online method is facile, fast, cost-efficient, and environmentally friendly.

Enhanced nutrient removal from mainstream sewage via denitrifying dephosphatation, endogenous denitrification and anammox in a novel continuous flow process

It is a challenging subject to realize nitrogen and phosphorus elimination synchronously from limited-carbon sewage through conventional biological processes. Herein, a novel continuous flow anaerobic/oxic/anoxic/oxic (AOA-O) process, which integrated denitrifying dephosphatation, endogenous denitrification and anammox in the anoxic zone, was developed to enhance nutrient elimination from low carbon/nitrogen sewage (3.4 in average). After the long-term operation (280 days), a satisfactory nutrient removal performance (effluent PO43--P: 0.2 mg P/L, total inorganic nitrogen (TIN):8.9 mg N/L) was obtained. Mass balance indicated that anammox contributed to 26.1% TIN removal and denitrifying dephosphatation contributed to 25.6% phosphorus removal, respectively. The cooperation of anammox bacteria retained in biofilms and endogenous denitrifying bacteria in flocculent sludge was responsible for the enhanced nutrient removal in the anoxic zone. Dechloromonas carried out phosphorus uptake both under oxic conditions and anoxic conditions. This study can broaden the application prospect of mainstream anammox.

Deposition of CaFe2O4 and LaFeO3 perovskites on polyurethane filter: A new photocatalytic support for flowthrough degradation of tetracycline antibiotic

The immobilization of powder catalysts on substrates has been the subject of increasing interest in the field of photocatalysis. For the first time, highly efficient LaFeO₃ and CaFe₂O₄ perovskites were hydrothermally deposited on polyurethane filters (LFO/PU, CFO/PU). Furthermore, the photo-Fenton catalytic decomposition of tetracycline antibiotic by the new catalyst filters was explored under visible light irradiation. The structural, optical, and morphological characteristics of the photo-active filters were investigated using Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM-EDS), X-ray diffraction (XRD), UV-visible diffusion spectra (UV-vis DRS), X-Ray fluorescence (XRF), and thermogravimetric/dynamic thermal analyses (TG-DTG). The decomposition studies were conducted in both batch and micro-flow reactor systems. The effects of solution pH, reactive species, and water type on the reaction mechanism were examined. It was found that the photo-Fenton degradation of tetracycline improved when the perovskite proportions on the filter were increased; the removal rates reached 94% and 80% forLFO/PU and CFO/PU, respectively. The high degradation performance obtained in lake (∼71%) and seawater (∼76%) demonstrated the great potential of photo-active catalyst filters, and their excellent stability was confirmed by reusability tests. In the continuous flow system, the photocatalytic filters kept the degradation rate stable at 83% and 44% after 7 h of examination forLFO/PU and CFO/PU, respectively. These results suggest that the as-prepared catalytic filters may be suitable for industrial photocatalytic applications.

A low-cost push-pull syringe pump for continuous flow applications

Syringe pumps are very useful tools to ensure a constant and pulsation-free flow rate, however usability is limited to batch processes. This article shows an open-source method for manufacturing a push pull syringe pump, valid for continuous processes, easy to build, low-cost and programmable. The push-pull syringe pump (PPSP) is driven by an Arduino nano ATmega328P which controls a NEMA 17 in microstepping via the A4988 stepper driver. The Push-Pull Syringe Pump setup is configurable by means of a digital encoder and an oled screen programmed using C ++. A PCB was designed and built to facilitate the assembly of the device. The continuous flow is guaranteed by four non-return valves and a dampener, which has been sized and optimized for use on this device. Finally, tests were carried out to evaluate the flow rates and the linearity of the flow. The device is achievable with a cost of less than 100 €.

New dynamic microreactor system to mimic biofilm formation and test anti-biofilm activity of nanoparticles

Microbial biofilms are composed of surface-adhered microorganisms enclosed in extracellular polymeric substances. The biofilm lifestyle is the intrinsic drug resistance imparted to bacterial cells protected by the matrix. So far, conventional drug susceptibility tests for biofilm are reagent and time-consuming, and most of them are in static conditions. Rapid and easy-to-use methods for biofilm formation and antibiotic activity testing need to be developed to accelerate the discovery of new antibiofilm strategies. Herein, a Lab-On-Chip (LOC) device is presented that provides optimal microenvironmental conditions closely mimicking real-life clinical biofilm status. This new device allows homogeneous attachment and immobilization of Pseudomonas aeruginosa PA01-EGFP cells, and the biofilms grown can be monitored by fluorescence microscopy. P. aeruginosa is an opportunistic pathogen known as a model for drug screening biofilm studies. The influence of flow rates on biofilms growth was analyzed by flow simulations using COMSOL® 5.2. Significant cell adhesion to the substrate and biofilm formation inside the microchannels were observed at higher flow rates > 100 µL/h. After biofilm formation, the effectiveness of silver nanoparticles (SNP), chitosan nanoparticles (CNP), and a complex of chitosan-coated silver nanoparticles (CSNP) to eradicate the biofilm under a continuous flow was explored. The most significant loss of biofilm was seen with CSNP with a 65.5% decrease in average live/dead cell signal in biofilm compared to the negative controls. Our results demonstrate that this system is a user-friendly tool for antibiofilm drug screening that could be simply applied in clinical laboratories.Key Points• A continuous-flow microreactor that mimics real-life clinical biofilm infections was developed.• The antibiofilm activity of three nano drugs was evaluated in dynamic conditions.• The highest biofilm reduction was observed with chitosan-silver nanoparticles.

Degradation of 1,4-dioxane by biochar activating peroxymonosulfate under continuous flow conditions

1,4-Dioxane degradation under both batch-scale and column experiments has been investigated within the biochar activated peroxymonosulfate (PMS) system for in-situ remediation of 1,4-dioxane contaminated groundwater. In case of the batch experiments, the 1,4-dioxane degradation efficiencies were significantly increased with the increased biochar pyrolysis temperatures. The optimized 1,4-dioxane degradation efficiency at 89.2% was achieved with 1.0 g L^-1 of biochar (E800) and 8.0 mM PMS. In the absence of PMS, the breakthrough rates of 1,4-dioxane in biochar packed column experiments under the dynamic flow conditions were relatively slow compared with those in sand packed columns. Simultaneously, based on the integrated areas (IA) from the 1,4-dioxane breakthrough curves, the degradation efficiency at 70.2% was estimated in biochar packed column (W_E800:W_Sand = 1:9) under continuous injections of 16.0 mM PMS. Electron paramagnetic resonance (EPR) indicated that hydroxyl, sulfate and superoxide radicals were generated within the biochar/PMS systems and alcohol quenching experiments suggested that the dominated hydroxyl and sulfate radicals were responsible for 1,4-dioxane degradation. The findings of this study suggested that the biochar activated PMS system is a promising and cost-effective strategy for the remediation of 1,4-dioxane contaminated groundwater.

Continuous-Flow Synthesis of N-Methylated Peptides via Generation of an Acyl N-Methylimidazolium Cation

A detailed protocol is described for the continuous-flow synthesis of N-methylated peptides. N-Methylated peptides are very important class of bioactive compounds compared with normal peptides because they can enhance oral bioavailability, cell membrane permeability, and stability against enzymatic degradation. In our developed flow synthesis, a variety of N-methylated dipeptides is obtained in high yields without severe racemization from equivalent amounts of amino acids. The addition of a strong Brønsted acid is critical to generate the highly reactive N-methylimidazolium cation species to accelerate the amidation. The developed approach enabled the synthesis of a bulky peptide with a higher yield in a shorter amount of time compared with the results of conventional amidation.

3D printed ceramics as solid supports for enzyme immobilization: an automated DoE approach for applications in continuous flow

In recent years, 3D printing has emerged in the field of chemical engineering as a powerful manufacturing technique to rapidly design and produce tailor-made reaction equipment. In fact, reactors with complex internal geometries can be easily fabricated, optimized and interchanged in order to respond to precise process needs, such as improved mixing and increased surface area. These advantages make them interesting especially for catalytic applications, since customized structured bed reactors can be easily produced. 3D printing applications are not limited to reactor design, it is also possible to realize functional low cost alternatives to analytical equipment that can be used to increase the level of process understanding while keeping the investment costs low. In this work, in-house designed ceramic structured inserts printed via vat photopolymerization (VPP) are presented and characterized. The flow behavior inside these inserts was determined with residence time distribution (RTD) experiments enabled by in-house designed and 3D printed inline photometric flow cells. As a proof of concept, these structured inserts were fitted in an HPLC column to serve as solid inorganic supports for the immobilization of the enzyme Phenolic acid Decarboxylase (bsPAD), which catalyzes the decarboxylation of cinnamic acids. The conversion of coumaric acid to vinylphenol was chosen as a model system to prove the implementation of these engineered inserts in a continuous biocatalytic application with high product yield and process stability. The setup was further automated in order to quickly identify the optimum operating conditions via a Design of Experiments (DoE) approach. The use of a systematic optimization, together with the adaptability of 3D printed equipment to the process requirements, render the presented approach highly promising for a more feasible implementation of biocatalysts in continuous industrial processes. Graphical abstract.

Supplementary Information

The online version contains supplementary material available at 10.1007/s41981-021-00163-4.

Nitrate removal from groundwater using a batch and continuous flow hybrid Fe-electrocoagulation and electrooxidation system

During the last two decades nitrate contaminated groundwater has become an extensive worldwide problem with wide-reaching negative effects on human health and the environment. In this study, a combination of electrocoagulation (EC) and electrooxidation (EO) was studied as a denitrification process to efficiently remove nitrates and ammonium (a by-product produced during EC) from real polluted groundwater. Initially, EC experiments under batch operating mode were performed using iron electrodes at different applied current density values (20-40 mA cm^-2). Nitrate percentage removal of 100 % was recorded, however high ammonium concentrations were performed (4.5-6.5 mg NH₄⁺-Ν L^-1). Therefore, a continuous flow system was examined for the complete removal of both nitrates and EC-generated ammonium cations. The system comprised an EC reactor, a settling tank and an EO reactor. The applied current densities to the EC process were the same as those in the batch experiments, while the volumetric flow rates were 4, 6 and 8 mL min^-1. Regarding the current density of the EO process was kept constant at the value of 75 mA cm^-2. The percentage nitrate removal recorded during the EC process ranged between 52.0 and 100 %, while the NH₄⁺-N concentration at the outlet of the EO reduced significantly (53-100 %) depending on the applied current density and the volumetric flow rate. Also, the dissolved iron concentration in the treated water was always below the legislated limit of 0.2 mg L^-1 (up to 0.027 mg L^-1). These results indicate that the proposed hybrid system is capable of denitrifying real nitrate contaminated groundwater without generating toxic by-products, therefore making the water suitable for human consumption.

Recent advances in continuous flow synthesis of heterocycles

In the current scenario, flow chemistry is emerging as a significant technology in the field of organic synthesis. This miniaturized protocol including microreactors facilitates excellent heat transfer, low solvent wastage, lesser reaction time, a safer environment for reagent handling and appreciable yields of desired products. Thus, this "enabling technology" has a great scope in the synthesis and preparation of a variety of heterocycles that require toxic reagents as starting materials. This review discusses the recent advances (2020-2021) in continuous flow strategy for synthesis and derivatization of variety of heterocyclic entities, of different ring size, using different approaches. This also highlights the advantages of different combined techniques like Microwave assisted heating, electrochemical flow cell, LED light source, NMR and FT-IR analysis, etc., that enables utilization of various mechanisms and real-time monitoring of reactions leading to improved results.

Controlling nanoparticle formation from the onset of nucleation through a multi-step continuous flow approach

HYPOTHESIS

Metallic nanoparticles of various shapes and sizes can be synthesised through a diversity of bottom-up pathways, such as precipitation induced by chemical reduction. Varying composition, by adjusting concentrations or adding/replacing species, is the predominant strategy to tune nanoparticles structures. However, controlling time down to the onset of precipitation, nucleation, should also provide a powerful means to control nanostructuration.

EXPERIMENTS

We perform sequential reagent additions with a time resolution down to the millisecond. We use a millifluidic continuous flow setup consisting of tangential mixers in series, which allows flow rates up to dozens of litres per hour. We systematically vary both addition order and delay for each reagent involved in the synthesis of silver nanoplates. The resulting dispersions are compared using UV-visible spectroscopy, transmission electron microscopy and small-angle X-ray scattering.

FINDINGS

We show that synthesis pathways differing only in the order of sub-second additions lead to drastically different synthetic outcomes. Silver nanoparticles of different shapes and sizes, displaying an array of plasmonic colours, are synthesised at the same final composition by tuning the composition pathways along time. Our results unlock a previously inaccessible portion of the space of parameters, which will lead to an enhanced structural diversity, control and understanding of nanoparticles syntheses.

Partitioning of nutrient removal contribution between granules and flocs in a hybrid granular activated sludge system

Sludge granulation in continuous-flow systems is an emerging technology to intensify existing activated sludge infrastructure for nutrient removal. In these systems, the nutrient removal contributions and partitioning of microbial functions between granules and flocs can offer insights into process implementations. To this end, a reactor system that simulates the continuous-flow environment using an equal amount of initial granule and floc biomass was investigated. The two operational strategies for maintaining granule growth in the continuous-flow system were (a) the higher solids retention time (SRT) for the granules versus flocs, as well as (b) selective feeding of carbon to the granules. The SRT of the large granule fractions (>425 µm, LG) and floc/small granule fractions (<425 µm, FSG) were controlled at 20 and 2.7-6.0 days, respectively. Long term operation of the hybrid granule/floc system achieved high PO₄^3- and NH₄⁺ removal efficiencies. Higher polyphosphate-accumulating organisms (PAO) activity was observed in the FSG than LG, while ammonia-oxidizing bacteria (AOB) activities were similar in the two biomass fractions. Nitrite shunt was observed in the FSG, possibly due to out-competition by the high NOB activity in LG. More importantly, washing out the FSG caused a reduction in LG's AOB and PAO activity, indicating a possible dependency of LG on FSG for maintaining its nutrient removal capacity. Our findings highlighted the partitioning and potential competition/cooperation of key microbial functional groups between LG and FSG, facilitating nutrient removal in a hybrid granular activated sludge system, as well as implications for practical application of the treatment platform.

Vasoplegia from Continuous Flow Left Ventricular Assist Devices

PURPOSE OF REVIEW

The contribution of continuous flow left ventricular assist devices (c-LVAD) to vasoplegic syndrome and postoperative outcomes after orthotopic heart transplant (OHT) is contested in the literature. A standardized definition of vasoplegic syndrome (VS) is needed to better recognize and manage vasoplegic shock.

RECENT FINDINGS

Vasoplegic syndrome occurs after orthotopic heart transplant more frequently than after other surgeries requiring cardiopulmonary bypass. c-LVADs lead to small vessel endothelial dysfunction and desensitized adrenal receptors; however, their contribution to the development of vasoplegia is debated in clinical studies. Pulsatility may mitigate vascular dysfunction resulting from long-term continuous flow, and should be further explored in the clinical setting when considering risk factors for vasoplegic syndrome. The incidence of vasoplegic syndrome after orthotopic heart transplant is rising with the increasing use of c-LVAD bridge to therapy. Robust clinical studies are needed to advance our understanding and approach to mitigating VS after OHT.

Comparing the Effects of Pulsatile and Continuous Flushing on Time and Type of Peripheral Intravenous Catheters Patency: A Randomized Clinical Trial

Introduction: Peripheral intravenous catheters (PICs) patency techniques such as flushing are being developed. According to some studies, flushing can be used continuously or in pulsatile forms. This study aimed to compare the effects of pulsatile flushing (PF) and continuous flushing (CF) on time and type of PICs patency. Methods: In this double-blind randomized clinical trial, 71 patients were randomly assigned into two groups of PF (n=35) and CF (n=36). The PF protocol was performed as successive injections of 1 mL normal saline (N/S) per second (sec) with a delay of less than 1 sec until the completion of 5 mL of solution. However, CF protocol was performed by injecting 5 mL N/S within 5 sec without any delay before and after each medicine administration. Data related to the time and type of PICs patency were collected using a patency checklist every 12 hours (h) up to 96 h. The statistical analysis was done by R statistical software (Version 3.5.1). Results: The results showed that the number of PICs remaining open was not significantly different between PF and CF groups during 96 h. The highest number of PICs excluded from the study was related to the time of 96 h as a result of partial patency in the two groups. Conclusion: There was no difference between CF and PF regarding the time and type of PICs patency. Thus, both techniques can be used to maintain the catheter patency.

Application of aerobic kenaf granules for biological nutrient removal in a full-scale continuous flow activated sludge system

Aerobic granular sludge (AGS) is a biofilm technology that offers more treatment capacity in comparison to activated sludge. The integration of AGS into existing continuous-flow activated sludge systems is of great interest as process intensification can be achieved without the use of plastic-based biofilm carriers. Such integration should allow good separation of granules/flocs and ideally with minor retrofitting, making it an ongoing challenge. This study utilized an all-organic media carrier made of porous kenaf plant stalks with high surface areas to facilitate biofilm attachment and granule development. A 5-stage Bardenpho plant was upgraded with the addition of kenaf media and a rotary drum screen to retain the larger particles from the secondary clarifier underflow whereas flocs were selectively wasted. Startup took 5 months with a sludge volume index (SVI) reduction from >200 to 50 mL g^-1. Most of the kenaf granules fell in the size range of 600-1400 μm and had a clear biofilm layer. The wet biomass density, SVI₃₀, and SVI₃₀/SVI₅ of the kenaf granules were 1035 g L^-1, 30.6 mL g^-1, and 1.0, respectively, which met the standards of aerobic granules. Improved stability of biological phosphorus removal performance enabled a 25% reduction in sodium aluminate usage. Microbial activities of kenaf granules were compared with aerobic granules, showing comparable N and P removal rates and presence of ammonium-oxidizing bacteria and polyphosphate-accumulating organisms in the outer 50-60 μm layer of the granule. This work is the first viable example for integrating fully organic biofilm particles in existing continuous-flow systems.

Impact of tricuspid regurgitation on late right ventricular failure in left ventricular assist device patients ~can prophylactic tricuspid annuloplasty prevent late right ventricular failure? ~

Background

In this study, we evaluated the prevalence of tricuspid regurgitation (TR) worsening in patients with left ventricular assist devices (LVADs) and its impact on late right ventricular (RV) failure.

Methods

We enrolled 147 patients of the 184 patients who underwent continuous-flow LVAD implantations from 2005 to March 2018. The prevalence of postoperative TR worsening and late RV failure were retrospectively evaluated.

Results

Concomitant tricuspid annuloplasty (TAP) was performed in 28 of 41 patients (68%) with preoperative TR greater than or equal to moderate (TR group) and in 23 of 106 patients (22%) with preoperative TR less than or equal to mild (non-TR group). Regarding the TR-free rates, despite receiving or not receiving concomitant TAP, there was no significant difference between the 2 groups (TR group: p = 0.37; non-TR group: p = 0.42). Of the 9 patients with postoperative TR greater than or equal to moderate, late RV failure developed in 3 patients, with TR worsening after RV failure in each case. During follow-up, 16 patients (11%) had late RV failure. As for the late RV failure-free rates, despite receiving or not receiving concomitant TAP, there was no significant difference between the 2 groups (TR group: p = 0.37; non-TR group: p = 0.96).

Conclusions

TR prognosis was preferable regardless of a patient receiving concomitant TAP; however, the presence of postoperative TR seemed to unrelated to late RV failure. Prophylactic TAP might not be necessary to prevent late RV failure.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13019-021-01492-0.

Synthesis of Quaternary Spirooxindole 2H-Azirines under Batch and Continuous Flow Condition and Metal Assisted Umpolung Reactivity for the Ring-Opening Reaction

An efficient and new approach for the synthesis of spirooxindole 2H-azirines via intramolecular oxidative cyclization of 3-(amino(phenyl)methylene)-indolin-2-one derivatives in the presence of I₂ and Cs₂ CO₃ under batch/continuous flow is described. This method is mild and facile to synthesize a variety of spirooxindole 2H-azirines derivatives in gram-scale. Furthermore, we have synthesized spiroaziridine derivatives from spirooxindole 2H-azirines derivatives via addition of Grignard reagent. In addition, we discloses an metal assisted attack of Grignard nucleophile at N-centre rather than C- of the spirooxindole 2H-azirines, which concurrently underwent ring opening of transient aziridines to afford N-substituted Z-3-(aminophenyl)indolin-2-one. A plausible mechanism for azirination and ring-opening reaction is also presented.

Acute Response of Human Aortic Endothelial Cells to Loss of Pulsatility as Seen during Cardiopulmonary Bypass

Cardiopulmonary bypass (CPB) results in short-term (3-5 h) exposure to flow with diminished pulsatility often referred to as "continuous flow". It is unclear if short-term exposure to continuous flow influences endothelial function, particularly, changes in levels of pro-inflammatory and pro-angiogenic cytokines. In this study, we used the endothelial cell culture model (ECCM) to evaluate if short-term (≤5 h) reduction in pulsatility alters levels of pro-inflammatory/pro-angiogenic cytokine levels. Human aortic endothelial cells (HAECs) cultured within the ECCM provide a simple model to evaluate endothelial cell function in the absence of confounding factors. HAECs were maintained under normal pulsatile flow for 24 h and then subjected to continuous flow (diminished pulsatile pressure and flow) as observed during CPB for 5 h. The ECCM replicated pulsatility and flow morphologies associated with normal hemodynamic status and CPB as seen with clinically used roller pumps. Levels of angiopoietin-2 (ANG-2), vascular endothelial growth factor-A (VEGF-A), and hepatocyte growth factor were lower in the continuous flow group in comparison to the pulsatile flow group whereas the levels of endothelin-1 (ET-1), granulocyte colony stimulating factor, interleukin-8 (IL-8) and placental growth factor were higher in the continuous flow group in comparison to the pulsatile flow group. Immunolabelling of HAECs subjected to continuous flow showed a decrease in expression of ANG-2 and VEGF-A surface receptors, tyrosine protein kinase-2 and Fms-related receptor tyrosine kinase-1, respectively. Given that the 5 h exposure to continuous flow is insufficient for transcriptional regulation, it is likely that pro-inflammatory/pro-angiogenic signaling observed was due to signaling molecules stored in Weible-Palade bodies (ET-1, IL-8, ANG-2) and via HAEC binding/uptake of soluble factors in media. These results suggest that even short-term exposure to continuous flow can potentially activate pro-inflammatory/pro-angiogenic signaling in cultured HAECs and pulsatile flow may be a successful strategy in reducing the undesirable sequalae following continuous flow CPB.

Evaluation of a continuous flow microbial fuel cell for treating synthetic swine wastewater containing antibiotics

Microbial fuel cell (MFC) systems are promising technologies for wastewater treatment and renewable energy generation simultaneously. Performance of a double-chamber microbial fuel cell (MFC) to treat synthetic swine wastewater containing sulfonamide antibiotics (SMs) was evaluated in this study. The MFC was operated in continuous modes at different conditions. Results indicated that the current was successfully generated during the operation. The performance of MFC under the sequential anode-cathode operating mode is better than that under the single continuous running mode. Specifically, higher removal efficiency of chemical oxygen demand (>90%) was achieved under the sequential anode-cathode operating mode in comparison with that in the single continuous mode (>80%). Nutrients were also be removed in the MFC's cathode chamber with the maximum removal efficiency of 66.6 ± 1.4% for NH₄⁺-N and 32.1 ± 2.8% for PO₄^3--P. Meanwhile, SMs were partly removed in the sequential anode-cathode operating with the value in a range of 49.4%-59.4% for sulfamethoxazole, 16.8%-19.5% for sulfamethazine and 14.0%-16.3% for sulfadiazine, respectively. SMs' inhibition to remove other pollutants in both electrodes of MFC was observed after SMs exposure, suggesting that SMs exert toxic effects on the microorganisms. A positive correlation was found between the higher NH₄⁺-N concentration used in this study and the removal efficiency of SMs in the cathode chamber. In short, although the continuous flow MFC is feasible for treating swine wastewater containing antibiotics, its removal efficiency of antibiotics requires to be further improved.

Phenotyping of Stable Left Ventricular Assist Device Patients Using Noninvasive Pump Flow Responses to Acute Loading Transients

BACKGROUND

Although it has been established that continuous flow left ventricular assist devices are sensitive to loading conditions, the effect of acute load and postural changes on pump flow have not been explored systematically.

METHODS AND RESULTS

Fifteen stable outpatients were studied. Patients sequentially transitioned from the seated position to supine, passive leg raise, and standing with transition effects documented. A modified Valsalva maneuver, consisting of a forced expiration with an open glottis, was performed in each position. A sustained, 2-handed handgrip was performed in the supine position. The pump flow waveform was recorded continuously and left ventricular end-diastolic diameter measured during each stage using transthoracic echocardiography. Transitioning from seated to supine posture produced a significant increase in the flow and the ventricular end-diastolic diameter, consistent with an increased preload. The transition from supine to standing produced a transient increase in the mean flow and decreased the flow pulsatility index. At steady state, these changes were reversed with a decrease in the mean and trough flow and increased pulsatility index, consistent with venous redistribution and possible baroreflex compensation. Four distinct patterns of standing-induced flow waveform effects were identified, reflecting varying preload, afterload, and individual compensatory effects. A sustained handgrip produced a significant decrease in flow and increase in flow pulsatility across all patients, reflecting an increased afterload pressure. A modified Valsalva maneuver produced a decrease in the flow pulsatility while seated, supine, and standing, but not during leg raise. Five patterns of pulsatility effect during Valsalva were observed: (1) minimal change, (2) pulsatility recovery, (3) rapid flatline, (4) slow flatline with delayed flow recovery, and (5) primary suction.

CONCLUSIONS

Acute disturbances in loading conditions produce heterogeneous pump flow responses reflecting their complex interactions with pump and ventricular function as well as reflex compensatory mechanisms. Differences in responses and individual variabilities have significant implications for automated pump control algorithms.

Feast/famine ratio determined continuous flow aerobic granulation

Plug flow reactors (PFRs) made of multiple completely stirred tank reactors (CSTRs) in series were used to cultivate aerobic granules in real domestic wastewater. Theoretically, changing the number of CSTR chambers in series will change the nature of plug flow, and thus alter the pattern of the feast/famine condition and impact the aerobic granulation progress. Therefore, PFRs were operated in 4-, 6-, and 8-chamber mode under the same gravity selection pressure (a critical settling velocity of 9.75 m h^-1) and hydraulic retention time (6.5 h) until steady states were reached to evaluate the effect of the feast/famine condition on continuous flow aerobic granulation. The sludge particle size, circularity, settleability, specific gravity, zone settling velocity, and extracellular polymeric substance contents were analyzed to evaluate the role that a feast/famine regime plays in aerobic granulation. It was found that aerobic granulation failed whenever the feast/famine ratio was greater than 0.5. The results support a conclusion that the feast/famine condition is likely a prerequisite for continuous flow aerobic granulation.

Response of bioaerosol cells to photocatalytic inactivation with ZnO and TiO2 impregnated onto Perlite and Poraver carriers

Bioaerosols are airborne microorganisms that cause infectious sickness, respiratory and chronic health issues. They have become a latent threat, particularly in indoor environment. Photocatalysis is a promising process to inactivate completely bioaerosols from air. However, in systems treating a continuous air flow, catalysts can be partially lost in the gaseous effluent. To avoid such phenomenon, supporting materials can be used to fix catalysts. In the present work, four photocatalytic systems using Perlite or Poraver glass beads impregnated with ZnO or TiO₂ were tested. The inactivation mechanism of bioaerosols and the cytotoxic effect of the catalysts to bioaerosols were studied. The plug flow photocatalytic reactor treated a bioaerosol flow of 460 × 1 0⁶ cells/m³ _air with a residence time of 5.7 s. Flow Cytometry (FC) was used to quantify and characterize bioaerosols in terms of dead, injured and live cells. The most efficient system was ZnO/Perlite with 72% inactivation of bioaerosols, maintaining such inactivation during 7.5 h due to the higher water retention capacity of Perlite (2.8 mL/g_Perlite) in comparison with Poraver (1.5 mL/g_Perlite). However, a global balance showed that TiO₂/Poraver system triggered the highest level of cytotoxicity to bioaerosols retained on the support after 96 h with 95% of dead cells. SEM and FC analyses showed that the mechanism of inactivation with ZnO was based on membrane damage, morphological cell changes and cell lysis; whereas only membrane damage and cell lysis were involved with TiO₂. Overall, results highlighted that photocatalytic technologies can completely inactivate bioaerosols in indoor environments.

ELECTRONIC SUPPLEMENTARY MATERIAL

Supplementary material is available in the online version of this article at 10.1007/s11783-020-1335-9 and is accessible for authorized users.

A High-Yielding Synthesis of EIDD-2801 from Uridine

A simple reordering of the reaction sequence allowed the improved synthesis of EIDD-2801, an antiviral drug with promising activity against the SARS-CoV-2 virus, starting from uridine. Compared to the original route, the yield was enhanced from 17 % to 61 %, and fewer isolation/purification steps were needed. In addition, a continuous flow procedure for the final acetonide deprotection was developed, which proved to be favorable toward selectivity and reproducibility.

Detailed mechanism and impact of new-onset late right heart failure during LVAD support

Not applicable.

Flocs in disguise? High granule abundance found in continuous-flow activated sludge treatment plants

To date, high performance of full-scale aerobic granular sludge (AGS) technology has been demonstrated on a global scale. Its further integration with existing continuous flow activated sludge (CFAS) treatment plants is the next logical step. All granular sludge reactors operated in sequencing batch reactors (SBR) mode with anaerobic feeding conditions select for growth of phosphorus and glycogen accumulating organisms (PAO and GAO, respectively), which are known to enhance sludge settling characteristics. Therefore, we hypothesized that AGS are commonly present at full-scale CFAS processes with enhanced biological phosphorus removal (EBPR) and low sludge volume index (SVI). This hypothesis was confirmed at 13 EBPR plants, where granules were found present (at plants where SVI was lower than 100 ml/g) with a strong correlation between high granule abundance and low SVI. A wide range of granule abundance was found among the plants, ranging from 0.5% to as high as 80%. Evaluations of the EBPR plant process configurations showed that high granule abundances may be related to selector design features such as high anaerobic food to mass (F/M) ratios, unmixed in-line fermentation, and high influent soluble COD fraction. Granules were also observed at a non-EBPR plant with an aerobic selector receiving high F/M feeds. Quantitative PCR and 16S rRNA gene sequencing analyses revealed higher relative gene abundance of Accumulibacter PAO and Competibacter GAO in the granules over flocs, as well as a correlation between granule abundance and some possible EPS producers such as Flavobacterium and Competibacter. Our results indicated that process configurations that select for slow-growing or EPS-producing heterotrophs play an important role for granule formation in full-scale CFAS systems as previously shown in SBR configurations.

Performance of a continuous stirred tank bioreactor employing an immobilized actinobacteria mixed culture for the removal of organophosphorus pesticides

In this study, we evaluated polyurethane foam (PF), volcanic rock (VR), and a modified plastic cap (MPC) as supports for the immobilization of organophosphorus (OP) pesticide-degrading actinobacterial strains. The colonization and activity of four streptomycetes were favoured by PF, which was selected as the carrier to use in a continuous stirred tank bioreactor (CSTR) that can be operated at increasing inflows of a pesticide mixture that contains the insecticides chlorpyrifos (CP) and diazinon (DZ). Our results demonstrate that the CSTR can be operated at flow rates of 10 and 40 mL h^-1 with greater than 85% removal of the pesticides in the short term. A significant decrease in the efficiency of CP removal was observed at the highest inflows into the reactor. The CP and DZ loading rates in the bioreactor ranged from 0.44 to 1.68 mg L^-1 h^-1 and from 0.50 to 2.17 mg L^-1 h^-1, respectively. Although the treated wastewater exhibited moderate toxicity for Raphanus sativus, a bioreactor inoculated with a mixed culture formed by Streptomyces spp. strains AC5, AC9, GA11 and ISP13 may provide an effective biotechnological strategy for the reduction of OP pesticide residues produced during agronomic and manufacturing practices and therefore prevent environmental pesticidal pollution.