Modeling of a Pilot Wastewater Treatment Plant Operated With Variable Inflows

The nitrification-denitrification process was studied on suspended activated sludge in a CSTR pilot plant of 15 litres. The system was operated in the single sludge mode and was fed with artificial wastewater. The experiments were carried out under steady and non-steady-state operational conditions in order to assess the reliability of mathematical simulations based on a modified ASM1 model that was successfully calibrated at the starting steady-state conditions. The dynamic model predictions and the measured responses of the real process yielded the initial values when the initial steady-state operational conditions were restored after stepped changes in the input flow. Although relatively good correlations were obtained between the experimental data and the model predictions, in some cases large differences were observed under non-steady-state operational conditions. This reflects the discrepancy between the complex nature of the real activated sludge processes and the model’s macroscopic descriptions of these processes

Separation and purification of biomacromolecules based on microfluidics

Separation and purification of biomacromolecules either in biopharmaceuticals and fine chemicals manufacturing, or in diagnostics and biological characterization, can substantially benefit from application of microfluidic devices. Small volumes of equipment, very efficient mass and heat transfer together with high process control result in process intensification, high throughputs, low energy consumption and reduced waste production as compared to conventional processing. This review highlights microfluidics-based separation and purification of proteins and nucleic acids with the focus on liquid-liquid extractions, particularly with biocompatible aqueous two-phase systems, which represent a cost-effective and green alternative. A variety of microflow set-ups are shown to enable sustainable and efficient isolation of target biomolecules both for preparative, as well as for analytical purposes.publishe

Characterization of an enzymatic packed-bed microreactor : experiments and modeling

AbstractA micro packed-bed reactor (µPBR) based on two-parallel-plates configuration with immobilized Candida antarctica lipase B in the form of porous particles (Novozym® 435) was theoretically and experimentally characterized. A residence time distribution (RTD) within µPBRs comprising various random distributions of particles placed in one layer was computationally predicted by a mesoscopic lattice Boltzmann (LB) method. Numerical simulations were compared with measurements of RTD, obtained by stimulus-response experiment with a pulse input using glucose as a tracer, monitored by an electrochemical glucose oxidase microbiosensor integrated with the reactor. The model was validated by a good agreement between the experimental data and predictions of LB model at different conditions. The developed µPBR was scaled-up in length and width comprising either a single or two layers of Novozym® 435 particles and compared regarding the selected enzyme-catalyzed transesterification. A linear increase in the productivity with the increase in all dimensions of the µPBR between two-plates demonstrated very efficient and simple approach for the capacity rise. Further characterization of µPBRs of various sizes using the piezoresistive pressure sensor revealed very low pressure drops as compared to their conventional counterparts and thereby great applicability for production systems based on numbering-up approach.Abstract A micro packed-bed reactor (µPBR) based on two-parallel-plates configuration with immobilized Candida antarctica lipase B in the form of porous particles (Novozym® 435) was theoretically and experimentally characterized. A residence time distribution (RTD) within µPBRs comprising various random distributions of particles placed in one layer was computationally predicted by a mesoscopic lattice Boltzmann (LB) method. Numerical simulations were compared with measurements of RTD, obtained by stimulus-response experiment with a pulse input using glucose as a tracer, monitored by an electrochemical glucose oxidase microbiosensor integrated with the reactor. The model was validated by a good agreement between the experimental data and predictions of LB model at different conditions. The developed µPBR was scaled-up in length and width comprising either a single or two layers of Novozym® 435 particles and compared regarding the selected enzyme-catalyzed transesterification. A linear increase in the productivity with the increase in all dimensions of the µPBR between two-plates demonstrated very efficient and simple approach for the capacity rise. Further characterization of µPBRs of various sizes using the piezoresistive pressure sensor revealed very low pressure drops as compared to their conventional counterparts and thereby great applicability for production systems based on numbering-up approach

Bijel-based mesophotoreactor with integrated carbon nitride for continuous-flow photocatalysis

The integration of continuous-flow technologies with heterogeneous photocatalysis has recently emerged as a promising strategy for the development of sustainable processes. Although conventional packed bed reactors have been extensively utilized in industrial catalytic applications, they face challenges related to energy transfer in the photocatalytic systems. This study presents an innovative approach to address this issue by integrating heterogeneous photocatalysts with an organic polymer, leading to the fabrication of a mesophotoreactor featuring a bijel-based structural configuration. This novel strategy involves hybridizing polypentadecalactone and in situ confining of carbon nitride in a bicontinuous porous mesoarchitecture. The structural and physicochemical properties of the resulting catalytic composite material are evaluated through an array of characterization methods, affirming the successful integration of carbon nitride within the overall structure. The unique bicontinuous porous architecture of the composite and its suitability for industrial applications is verified, as exemplified by its exceptional efficiency in the photodegradation of methylene blue (>99 %) under flow conditions and remarkable stability up to three reaction cycles. A mathematical model is developed to describe continuous photocatalytic processes occurring in the novel tubular mesophotoreactor, with a specific focus on the degradation of the methylene blue dye. This model is successfully validated, leading to results in agreement with the experimental measurements. Additionally, fluid dynamics simulations demonstrate that the mesophotoreactor design allows for the effective diffusion of light through its channels, resulting in higher irradiation levels compared to conventional systems such as packed bed reactors. The innovative design of the catalytic reactor presented in this work offers a versatile and efficient alternative to the conventional heterogeneous systems, significantly broadening the range of applications for photocatalytic processes

Lattice Boltzmann modeling-based design of a membrane-free liquid-liquid microseparator

The benefits of continuous processing and the challenges related to the integration with efficient downstream units for end-to-end manufacturing have spurred the development of efficient miniaturized continuously-operated separators. Membrane-free microseparators with specifically positioned internal structures subjecting fluids to a capillary pressure gradient have been previously shown to enable efficient gas-liquid separation. Here we present initial studies on the model-based design of a liquid-liquid microseparator with pillars of various diameters between two plates. For the optimization of in silico separator performance, mesoscopic lattice-Boltzmann modeling was used. Simulation results at various conditions revealed the possibility to improve the separation of two liquids by changing the geometrical characteristics of the microseparator

Model-based design of continuous biotransformation in a microscale bioreactor with yeast cells immobilized in a hydrogel film

Miniaturized flow reactors with immobilized biocatalysts offer enormous potential for process intensification. They enable long-term use of biocatalysts, continuous operation that significantly outperforms batch processes, and efficient mass and heat transfer that results in highly controlled reaction conditions. Despite their increasing use in biocatalytic processes, optimization of reactor design and operating conditions based on mathematical description is very rare. This work aims to fill this gap by developing and validating a mathematical model for the continuous biotransformation process in a microreactor between two plates with immobilized whole cells in hydrogel layers on the bottom and top of the reactor. A biocatalytic production of L-malic acid by fumaric acid hydration using permeabilized Saccharomyces cerevisiae whole cells was used as a model reaction. The diffusivity of substrate and product in a liquid phase and in a copolymeric hydrogel layer and the reaction kinetic parameters considering the Michaelis-Menten kinetics of the reversible enzymatic reaction were estimated in initial batch experiments. The results obtained in a continuously operated microbioreactor with immobilized whole cells at different fumaric acid concentrations and flow rates were in excellent agreement with the predictions of the developed mathematical model comprising transport phenomena and reaction kinetics. Based on the validated model and using time-scale analysis with characteristic times, the optimal process and operating conditions for the developed microbioreactor system were determined. The model predicts an equilibrium conversion of fumaric acid at the highest inlet concentration tested when using a liquid height of 200 μm and a hydrogel thickness on both sides of the channel of 400 μm at a residence time of 30 min

A lattice Boltzmann study of 2D steady and unsteady flows around a confined cylinder

In this work, the lattice Boltzmann (LB) method was applied to simulate incompressible steady and unsteady low Reynolds number (Re) flows around a confined cylinder. In the LB method, different collision models (Bhatnagar–Gross–Krook model, two-relaxation-time model, multi-relaxation-time model, and entropic lattice Boltzmann model) and a regularization model were used, and the results were compared. Numerical results pertaining to a two-dimensional flow around a cylinder are reported and compared with numerical and experimental data available in the literature. The results agree with the predictions made from the literature. A correlation for Strouhal number (St) for 55 ≤ Re ≤ 300 is suggested