Metabolic-fluid dynamics model construction and scale-down design for an industrial penicillin chrysogenum fermentation with combined dissolved oxygen and glucose concentration dynamics

This study focuses on the metabolic impacts of simultaneous glucose and oxygen concentration gradients on penicillin production in an industrial-scale fermentor, using the computational fluid dynamics-cellular reaction dynamics approach. Inclusion of oxygen-coupling considerably impacts the glucose uptake and resulting penicillin productivity...

Optimising flow and mixing in a full-scale gas-mixed anaerobic digester by integrating sludge rheological data using computational fluid dynamics

Gas-mixing is commonly applied in anaerobic digesters, yet the resulting flow and hydraulic mixing are difficult to evaluate because of limited full-scale experimental data and uncertainties in integrating sludge rheological data. This study used computational fluid dynamics (CFD) to assess the impact of treated sludge rheology on flow and...

Characterisation of Sludge Rheology and Sludge Mixing in Gas-mixed Anaerobic Digesters

Excess sludge handling is as important as treating the wastewater in determining the operational performance and costs in modern municipal wastewater treatment plants (WWTPs). In practice, excess sludge handling is widely implemented using anaerobic digestion (AD), in which the organic matter inside the sludge is not only stabilised and partly...

Impacts of shearing and temperature on sewage sludge: Rheological characterisation and integration to flow assessment

Accurate rheological characterisation of sewage waste activated sludge (WAS) is of high importance for downstream processing related to optimised sludge pumping and mixing, assessment of energy demands and overall process design. However, to elaborate rheological behaviour is often challenging under dynamic operational conditions in practice....

Characterising the two-phase flow and mixing performance in a gas-mixed anaerobic digester: Importance for scaled-up applications

This study aimed to characterise the gas-liquid flow and mixing behaviour in a gas-mixed anaerobic digester by improving phase interaction modelling using Computational Fluid Dynamics (CFD). A 2D axisymmetric model validated with experimental data was set up using an Eulerian-Eulerian method. Uncertainty factors, including bubble size, phase...

Experimental and mathematical characterisation of the rheological instability of concentrated waste activated sludge subject to anaerobic digestion

For a proper operational performance assessment of excess sewage sludge digesters in practice, a better understanding of waste activated sludge (WAS) rheological behaviour is important, especially regarding the low-shear and poor mixing zones in anaerobic digesters. The potential rheological instability of WAS with different total solids (TS)...

Multiple transitions in rotating turbulent Rayleigh-Bénard convection

Sharp transitions between potentially different turbulent states are unexpected because one might think that they should be washed out by the prevailing intense fluctuations and short coherence lengths and times. Contrary to this expectation, we found a sequence of such transitions in turbulent rotating Rayleigh-Bénard convection as the rotation...