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Greg Leslie - One of the best experts on this subject based on the ideXlab platform.

  • numerical simulation of bubble induced shear in Membrane bioreactors effects of mixed liquor rheology and Membrane Configuration
    Water Research, 2015
    Co-Authors: Xuefei Liu, Yuan Wang, David T Waite, Greg Leslie
    Abstract:

    Abstract A CFD model, incorporating an empirically determined rheology model and a porous media model, was developed to simulate bubble induced surface shear in Membrane bioreactors configured with hollow fibre Membranes with outer diameters ranging from 1.3 to 2.4 mm, arranged in vertically orientated modules with packing density from 200 to 560 m2/m3. The rheology model was developed for mixed liquor suspended solids (MLSS) concentrations of 3 to 16 gL−1 in the presence and absence of coagulant (generated by addition of a ferrous salt) for shear rates ranging from 0 to 500 s−1. Experimentally determined particle relaxation times for the biological flocs in the mixed liquor, both in the absence and presence of iron, were negligible, consistent with an environment where positive buoyancy forces were greater than negative settling forces thereby allowing the sludge mixture to be modelled as a single continuous phase. The non-Newtonian behaviour of the mixed liquor was incorporated into the CFD simulations using an Ostwald-de Waele rheology model. Interactions between mixed liquor and hollow fibre Membranes of different fibre size and packing density were described using a porous media model that was calibrated by empirical measurement of inertial loss coefficients over a range of viscosities (0.8 × 10−3 to 2.1 × 10−3 Pa.s) and velocities (0 to 0.35 m/s) typically encountered in full scale MBRs. Experimental results indicated that addition of iron salts resulted in an increase in MLSS and sludge viscosity. Shear stress is affected by both velocity and viscosity. The increase in sludge viscosity resulted in an increase in resistance to flow through the hollow fibre Membrane bundles and, as a result, decreased the liquid flow velocities. CFD simulations provided insight on the effects of point of coagulant addition and MLSS concentration on bubble-induced shear over a range of industrially relevant conditions. A 12% increase in shear stress was observed when ferrous salts were added to the Membrane filtration zone compared to addition to the primary anoxic zone. The presence of iron salts also improved the distribution of shear stress especially at the lower zone of the Membrane module. The CFD models developed here were validated using Particle Image Velocimetry (PIV) with the average difference between simulated liquid velocities and PIV measured velocities found to be 5.5%.

  • computational fluid dynamics cfd analysis of Membrane reactors modelling of Membrane bioreactors for municipal wastewater treatment
    Handbook of Membrane Reactors#R##N#Fundamental Materials Science Design and Optimisation, 2013
    Co-Authors: Yuan Wang, T D Waite, Greg Leslie
    Abstract:

    Abstract: Computational methods provide invaluable insight to the analysis of complex two-phase and three-phase flow in municipal-scale Membrane bioreactors. This capacity to simulate air, liquid and solid movement is an invaluable contribution to the design process. The following chapter provides an overview of Membrane bioreactor (MBR) design, computational fluid dynamics (CFD) theory and modelling techniques for two-phase and three-phase flow. Topics include the effect of reactor geometry and Membrane Configuration on turbulence, the accumulation of solids, energy consumption and the efficiency of aeration. Emphasis is placed on the importance of model calibration and validation and the outlook for future work.

  • evaluation of full scale Membrane bioreactor mixing performance and the effect of Membrane Configuration
    Journal of Membrane Science, 2010
    Co-Authors: M Brannock, Yuan Wang, Greg Leslie
    Abstract:

    The design and optimisation of MBR units require knowledge of the biokinetics, fouling potential and mixing. Although the mixing within an MBR system is of critical importance to the performance, MBRs are mainly designed on the basis of biokinetics and fouling potential of the treatment system while assuming the hydrodynamic characteristics. One method to characterise the mixing is the residence time distribution (RTD). In this work, tracer studies using lithium chloride were performed to acquire RTD profiles of two full-scale MBR systems with different Membrane Configurations (flat sheet and hollow fibre). Analysis of the RTD profiles indicated that that both MBRs, including their respective filtration tanks, are very close to completely mixed. The mixing energy per volume of permeate used by the hollow fibre Membrane vessel was lower than that of flat sheet module MBR; both in terms of whole MBR energy usage and Membrane blower only energy usage. Hence, it is possible to conclude that the flat sheet MBR, per square metre of Membrane, in this case, requires more energy to achieve a similar degree of mixing.

  • Evaluation of Membrane bioreactor performance via residence time distribution: effects of Membrane Configuration and mixing.
    Water Science and Technology, 2008
    Co-Authors: Yuan Wang, M Brannock, Greg Leslie
    Abstract:

    Unlike conventional wastewater treatment systems that have a single effluent discharge point, Membrane bioreactors (MBR) may have multiple extraction points resulting from the location of the Membrane element in the reactor. This leads to multiple residence time distributions for an MBR system. One method to characterise the mixing is based on the concept of residence time distribution (RTD). A set of RTDs were generated using the conservative tracer, lithium chloride, for pilot plant MBRs with capacity up to 300 m 3 /day. Flat sheet and hollow fibre pilot plant MBR systems were operated in parallel on primary effluent collected at the Bedok Water Reclamation Plant in the republic of Singapore. Analysis of the RTD profiles indicated that Membrane geometry did not impact on the kinetic conversion associated with nitrification because both MBRs were in well mixed conditions. However, the energy required to achieve perfect mixing with a hollow fibre module MBR, as defined by the velocity gradient, was lower than that with a flat sheet module MBR. The implication is that energy input associated with reactor mixing will depend on the Configuration of the Membrane. The difference in energy requirements between flat sheets and hollow fibres is such that careful consideration should be given to Membrane selection in larger municipal installations.

Lara Fernandezcerezo - One of the best experts on this subject based on the ideXlab platform.

  • an ultra scale down method to investigate monoclonal antibody processing during tangential flow filtration using ultrafiltration Membranes
    Biotechnology and Bioengineering, 2019
    Co-Authors: Lara Fernandezcerezo, Andrea C M E Rayat, Alex Chatel, Jennifer M Pollard, Gary J Lye, M Hoare
    Abstract:

    The availability of material for experimental studies is a key constraint in the development of full-scale bioprocesses. This is especially true for the later stages in a bioprocess sequence such as purification and formulation, where the product is at a relatively high concentration and traditional scale-down models can require significant volumes. Using a combination of critical flow regime analysis, bioprocess modelling and experimentation, ultra scale-down (USD) methods can yield bioprocess information using only millilitre quantities prior to embarking on highly demanding full-scale studies. In this study the performance of a pilot-scale tangential flow filtration (TFF) system based on a Membrane flat-sheet cassette using pumped flow was predicted by devising an USD device comprising a stirred cell using a rotating disc. The USD device operates with just 2.1 cm2 of Membrane area and for example just 1.7 mL of feed for diafiltration studies. The novel features of the design involve optimisation of the disc location and the Membrane Configuration to yield an approximately uniform shear rate. This is as characterised using computational fluid dynamics for a defined layer above the Membrane surface. A pilot-scale TFF device operating at ~500-fold larger feed volume and Membrane area was characterised in terms of the shear rate derived from flow rate-pressure drop relationships for the cassette. Good agreement was achieved between the USD and TFF devices for the flux and resistance values at equivalent average shear rates for a monoclonal antibody diafiltration stage. This article is protected by copyright. All rights reserved.

M Hoare - One of the best experts on this subject based on the ideXlab platform.

  • an ultra scale down method to investigate monoclonal antibody processing during tangential flow filtration using ultrafiltration Membranes
    Biotechnology and Bioengineering, 2019
    Co-Authors: Lara Fernandezcerezo, Andrea C M E Rayat, Alex Chatel, Jennifer M Pollard, Gary J Lye, M Hoare
    Abstract:

    The availability of material for experimental studies is a key constraint in the development of full-scale bioprocesses. This is especially true for the later stages in a bioprocess sequence such as purification and formulation, where the product is at a relatively high concentration and traditional scale-down models can require significant volumes. Using a combination of critical flow regime analysis, bioprocess modelling and experimentation, ultra scale-down (USD) methods can yield bioprocess information using only millilitre quantities prior to embarking on highly demanding full-scale studies. In this study the performance of a pilot-scale tangential flow filtration (TFF) system based on a Membrane flat-sheet cassette using pumped flow was predicted by devising an USD device comprising a stirred cell using a rotating disc. The USD device operates with just 2.1 cm2 of Membrane area and for example just 1.7 mL of feed for diafiltration studies. The novel features of the design involve optimisation of the disc location and the Membrane Configuration to yield an approximately uniform shear rate. This is as characterised using computational fluid dynamics for a defined layer above the Membrane surface. A pilot-scale TFF device operating at ~500-fold larger feed volume and Membrane area was characterised in terms of the shear rate derived from flow rate-pressure drop relationships for the cassette. Good agreement was achieved between the USD and TFF devices for the flux and resistance values at equivalent average shear rates for a monoclonal antibody diafiltration stage. This article is protected by copyright. All rights reserved.

Andre Faaij - One of the best experts on this subject based on the ideXlab platform.

  • techno economic comparison of combined cycle gas turbines with advanced Membrane Configuration and monoethanolamine solvent at part load conditions
    Energy & Fuels, 2017
    Co-Authors: Mijndert Van Der Spek, Davide Bonalumi, Giampaolo Manzolini, Andrea Ramirez, Andre Faaij
    Abstract:

    This work compares the part load techno-economic performance of CO2 capture from a combined cycle gas turbine (CCGT) using a Membrane Configuration with selective CO2 recycle and using monoethanolamine (MEA) solvent, under the assumption of flexible power plant dispatch. This is the first time that the techno-economic performance of CO2 capture technologies is compared assuming a flexible dispatch profile, and the assessment was done using a comprehensive, new, part load assessment approach. Analyzing the part load performance of CO2 capture and storage (CCS) technologies is relevant because of significant changes in our power systems, dramatically reducing the utilization of thermal power plants. The technical performance of the Configurations with and without CCS was simulated at steady state, at operating points between maximum continuous rating (100% gas turbine loading) and minimum stable load (35% gas turbine loading). The performance at these operating points was then aggregated into weighted avera...

Taishung Chung - One of the best experts on this subject based on the ideXlab platform.

  • effects of additives on dual layer hydrophobic hydrophilic pvdf hollow fiber Membranes for Membrane distillation and continuous performance
    Chemical Engineering Science, 2012
    Co-Authors: Felinia Edwie, May May Teoh, Taishung Chung
    Abstract:

    Abstract The advantages of the implementation of dual-layer hydrophobic–hydrophilic hollow fiber Membranes for Membrane distillation (MD) have been highlighted in this work. The effects of incorporating methanol as a non-solvent additive and self-synthesized fluorinated silica (FSi) particles as a hydrophobic modifier on the resultant Membrane morphology and MD performance were investigated. Employing a 3.5 wt% sodium chloride solution at 80 °C, the highest direct contact Membrane distillation (DCMD) flux of 83.40±3.66 kg/(m 2  h) and separation factor higher than 99.99% were attained for the Membrane spun with methanol additive. Moreover, the stability of the dual-layer hydrophobic–hydrophilic hollow fiber Membrane has been demonstrated through continuous DCMD experiments for 5 days. The separation factor was maintained higher than 99.99% for the Membrane spun with methanol additive, verifying the suitability of the dual-layer hydrophobic–hydrophilic hollow fiber Membrane Configuration for desalination processes. The morphological transformation of the outer Membrane surface from a porous agglomerated globule structure into a denser interconnected globule structure may be accounted for by the stability improvement of the Membrane spun with methanol additive. On the other hand, it was found that an enhanced hydrophobicity of the Membrane spun with FSi particles did not result in an improvement of the Membrane stability. The existence of the hydrophilic hydroxyl group on the FSi particle surface may favor the occurrence of Membrane wetting.

  • dual layer pvdf ptfe composite hollow fibers with a thin macrovoid free selective layer for water production via Membrane distillation
    Chemical Engineering Journal, 2011
    Co-Authors: May May Teoh, Taishung Chung
    Abstract:

    Abstract In this study, the polyvinylidene fluoride (PVDF)/polytetrafluoroethylene (PTFE) composite is used to fabricate hollow fiber Membranes for seawater desalination via direct contact Membrane distillation (DCMD) application. The incorporation of PTFE particles in the formulated dope solution can efficiently suppress the formation of macrovoids and enhance the outer surface hydrophobicity. Dual-layer hollow fibers with a desirable macrovoid-free morphology and a relatively thin (13 ± 2 μm) outer-layer can be obtained via blending 30 wt% of PTFE particles in the outer-layer dope. The resultant dual-layer hollow fiber (DL-30) displays a moderately high contact angle of 114.5° and porosity of 81.5%. Compared to the single-layer hollow fiber with 30 wt% (SL-30) PFTE particles, the DL-30 fiber exhibits a flux enhancement of approximately 24% that is contributed to the reduction in inner-layer mass transfer resistance. Dual layer Membrane Configuration with a lower wall thickness as well as larger outer and inner diameters provides even higher water vapor transport is potentially suitable for desalination. Both single- and dual-layer PVDF/PTFE hollow fiber Membranes reveal good long-term stability of up to 100 h of continuous testing. By utilizing the state-of-the-art dual-layer spinning technology, hollow fiber Membranes with better performance (i.e. enhanced flux) and morphology (i.e. macrovoid-free) can be tailored.