Next generation membrane modules and reactors
Researchers at CTET use the state-of-the-art technology, Computational Fluid Dynamics (CFD) together with Mechanical Structural Analysis and advanced characterisation techniques to create membrane modules with low energy consumption and low fouling potential.
Our technologies
CFD Modelling of Membrane Bioreactors
Led by Dr Xuefei Liu and Dr Yuan Wang, researchers at UNSW and CTET have developed a variety of computational methods to the analysis of complex two-phase and three-phase flow in municipal scale membrane bioreactors (MBR). Since 2006, the team has developed Computational Fluid Dynamics (CFD) models to predict the hydrodynamics and mixing in full scale reactors (macro-scale simulations), to optimise the flow and aeration patterns in the membrane filtration zone (meso-scale simulations), and to quantify the aeration induced lateral fibre movement on membrane surface shear stress and filtration flux (micro-scale simulations). The CFD models developed were based on the commercial CFD package Ansys Fluent/Ansys CFX, incorporating with self-developed code to describe the rheological behaviour of activated sludge, and porous media model to account for the flow resistance caused by the full scale hollow fibre membrane module to the three-dimensional fluid flow.
Prediction of the hydrodynamics and mixing in full scale reactors (Macro-scale Simulations)
MBRs are mostly designed around biokinetic and membrane fouling considerations, even though the mixing within an MBR system is of critical importance to the performance of the system. Mixing can affect both the efficiency of nutrient removal in the bioreactor and the settling of the sludge. Good mixing promotes the transfer of substrates and theat to the microorganisms and ensures the effective use of the entire reactor volume. Three-dimensional CFD models have been developed to model the overall mixing for a 2MLD hollow fibre MBR in Sydney and a 5MLD flat sheet MBR in South Australia.
Optimisation of membrane module design and aeration patterns (Meso-scale simulations)
Commercial MBRs are available in different configurations based on membrane orientation, aerator aperture size, aerator position and free volume between membrane modules and tank walls. The overarching design goal is to create a spatially uniform velocity gradient in the filtration zone to limit localised fouling and promote even distribution of filtrate flux over all the available membrane area. However, in the absence of performance data collected under controlled conditions, it is difficult to assess which design achieves the highest surface shear while simultaneously optimising footprint of the filtration zone and power input for the aeration system. This can be attributed to the complex conditions in the filtration zone and the interdependence of the effect of each design variable on bubble induced shear.
The objective of this project was to evaluate which combination of features of the hollow fibre membrane module, filtration tank, and aeration system that can achieve higher and more homogeneous shear in the filtration zone at the same aeration energy input. A Computational Fluid Dynamics (CFD) approach using rheological and porous media sub-models was used to simulate pressure drop across the hollow fibre membrane bundle for a range of conditions that are relevant for application of MBR’s in municipal wastewater.
Capacitive Deionization (CDI)
When a voltage is applied across two electrodes, cations are attracted to the cathode and anions to the anode, resulting in the charged species being removed from solution. A novel CDI system driven by solar energy has been developed by UNSW to remove salts and other contaminants from water.
Projects
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Researchers from CTET have extensive experiences in implementing Computational Fluid Dynamics (CFD) together with other process simulation tools and advanced experimental characterisation techniques to optimise the designs of various processes. In a recent project, the CTET team used both numerical modelling methods and experimental approaches to optimise and improve the design of a full-scale activated sludge (CAS) tank designed by a local partner in Yixing. The distribution of dissolved oxygen in the CAS tank was improved such that effective simultaneous aerobic and anoxic digestion could be achieved. Simulation results together with an economic analysis report prepared by CTET provided its partner with clear direction with regard to the optimization of equipment and plant design.
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Multi-stage RO treatment technology is widely used in coal mine water desalination to achieve water recoveries of greater than 95%. The composition of the concentrated stream changes significantly throughout the process leading to different contamination challenges for the RO membranes that are typically used. Collaborating with industry partners, CTET combines membrane autopsy techniques, CFD simulation technology and process design to optimise the process design and operation of the multistage ro systems used.
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Multi-stage RO treatment technology is widely used in coal mine water desalination to achieve water recoveries of greater than 95%. The composition of the concentrated stream changes significantly throughout the process leading to different contamination challenges for the ro membranes that are typically used. Collaborating with industry partners, CTET combines membrane autopsy techniques, CFD simulation technology and process design to optimise the process design and operation of the multistage ro systems used.
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UNSW CTET has been working together with the partner to conduct a pre-test to evaluate the performance of a CFD model developed in CTET in predicting the hydraulic performance of a lab-scale cross-flow RO cell operated in the partner's lab. A 3D CFD model was built using the modelling method developed in UNSW CTET to simulate the RO performance based on the geometry of a lab-scale cross-flow RO cell provided by Suez. A less than 4% error was achieved between the modelling and experimental results, indicating the high accuracy of the model in estimating the distribution of flow and salt concentration in the lab-scale RO cell. The use of a concentrate side spacer was found to significantly minimise concentration polarisation, contributing to higher permeate flow at high feed concentration. This model, in combination with a series of CFD models developed by UNSW CTET, can be used to estimate the distribution of flow and the concentration of multivalent inorganic salts in RO elements ranging from lab-scale to full-scale with various configurations.
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Since 2006, research team led by Dr Yuan Wang and Professor Greg Leslie at UNSW UNESCO Centre for Membrane Science & Technology (UCMST) have developed a wide range of mathematical models covering different aspects of membrane separation processes (see figure below), including microfiltration, ultrafiltration, nanofiltration, reverse osmosis.
- EU project AMEDEUS (“Accelerate Membrane Development for Urban Sewage Purification, 2006 - 2009)
- ARC Linkage Project “Optimisation of nutrient removal, membrane fouling and excess sludge dewatering in hybrid coagulation/submerged membrane bioreactor (SMBR) treatment of wastewaters” (ARC LP 100100056, 2010 – 2014)
- CFD models to assess sludge rheology on membrane surface shear
- CFD models to optimise membrane module design for submerged hollow fibre MBRs
- Membrane fouling in industrial anaerobic membrane bioreactors (AnMBRs) (collaborative research with University of Queensland) Integrated CFD with fouling model for anaerobic MBR for slaughterhouse wastewater treatment
- Development of membrane distillation (MD)/membrane crystallization (MC) systems (ARC discovery project, 2013 – 2016)
- Design of anaerobic membrane bioreactors using Computational Fluid Dynamics (collaborative research with Abengoa Research Spain) (2015)
- Development of mobile groundwater desalination systems (project funded by Tata Trust India) (2016 – 2018)
- Development of new generations of membrane module - Project with Beijing Origin Water through UNSW Torch Program (2016 - 2019)