Numerical modelling of oxygen mass transfer in diffused aeration systems: A CFD-PBM approach

Mohan, RT and Kumar, MSM and Rao, L (2021) Numerical modelling of oxygen mass transfer in diffused aeration systems: A CFD-PBM approach. In: Journal of Water Process Engineering, 40 .

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Abstract

The diffused aeration process is the most energy-intensive operation of bioreactor treatment, amounting to 45�75 of the plant energy costs. To improve its efficiency, it is essential to measure the oxygen transfer rate from the aerators to wastewater. In this study, a multiphase mixture computational fluid dynamics (CFD) model is developed using k-ε turbulence closure equations along with a discrete population balance model (PBM) add-on with specific bubble classes, to predict the oxygen mass transfer. The transfer of oxygen species from air to water is modeled using the species transport model. The PBM is used to analyze the formation, growth, breakage, and coalescence of air bubbles. The validated model is then extended for sensitivity analysis for a diffused aeration system in a bench-scale aeration tank. Results show that, the volumetric oxygen mass transfer coefficient increases by 15 , with a decrease of air bubble size by 10 . The air bubbles have a wider distribution, with a larger diameter near the bottom of the bioreactor and a narrow distribution with a smaller bubble size at the top. Results show that, in the bioreactor, the dissolved oxygen concentration reaches the equilibrium or saturation value when the height by breadth ratio is 2.5 and does not increase further with increase in height of the water column. Also, the air bubble size of 6 mm was the efficient bubble size for a fixed airflow rate of 1.45 m3 h�1. © 2021 Elsevier Ltd

Item Type:	Journal Article
Publication:	Journal of Water Process Engineering
Publisher:	Elsevier Ltd
Additional Information:	The copyright for this article belongs to Elsevier Ltd.
Keywords:	Bioreactor; Computational fluid dynamics; Diffused aeration system; Oxygen mass transfer; Population balance model
Department/Centre:	Division of Interdisciplinary Sciences > Interdisciplinary Centre for Water Research Division of Mechanical Sciences > Centre for Sustainable Technologies (formerly ASTRA) Division of Mechanical Sciences > Civil Engineering
Date Deposited:	23 Dec 2021 10:51
Last Modified:	24 Dec 2021 06:35
URI:	http://eprints.iisc.ac.in/id/eprint/67922

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