Euler-Lagrange Computational Fluid Dynamics simulation of a full-scale unconfined anaerobic digester for wastewater sludge treatment

摘要

Highlights•For the first time, an Euler-Lagrange CFD model is applied to model a full-scale gas-mixed anaerobic digester.•Mixing is assessed through a novel, multi-faced approach.•The influence of sludge pseudoplasticity in mixing quality is discussed for the first time.•Mixing input power can be reduced without compromising mixing in the setup taken into account.•A strategy to mitigate sludge pseudoplasticitys effect on mixing quality is proposed for the first time.AbstractFor the first time, an Euler-Lagrange model for Computational Fluid Dynamics (CFD) is used to model a full-scale gas-mixed anaerobic digester. The design and operation parameters of a digester from a wastewater treatment works are modelled, and mixing is assessed through a novel, multi-facetted approach consisting of the simultaneous analysis of (i) velocity, shear rate and viscosity flow patterns, (ii) domain characterization following the average shear rate value, and (iii) concentration of a non-diffusive scalar tracer. The influence of sludge’s non-Newtonian behaviour on flow patterns and its consequential impact on mixing quality were discussed for the first time. Recommendations to enhance mixing effectiveness are given: (i) a lower gas mixing input power can be used in the digester modelled within this work without a significant change in mixing quality, and (ii) biogas injection should be periodically switched between different nozzle series placed at different distances from the centre.