Water Quality Assessment and Aeration Optimization of Wastewater Aeration Tanks Based on CFD Coupled with the ASM2 Model

Abstract

High energy consumption and low aeration efficiency remain significant challenges in wastewater treatment. This study introduces a computational method that integrates the activated sludge model with Fluent (2021) to comprehensively simulate the internal operations of aeration tanks, enabling accurate modeling of biochemical mass transfer processes. Hydraulic retention times were analyzed using streamlined patterns, while low-velocity flow regions were identified across cross-sectional planes. The study systematically evaluated key water quality indicators, including dissolved oxygen, chemical oxygen demand (COD), total phosphorus (TP), total nitrogen (TN), and ammonium nitrogen (NH4+-N), across the aeration tank. A novel metric was proposed to quantify purification efficiency per unit aeration volume. Four optimized aeration schemes were designed and tested, incorporating microbubble aeration to improve flow dynamics. The optimized schemes achieved a 28% reduction in aeration energy while maintaining purification efficiency losses for COD, TP, TN, and NH4+-N below 8%. An alternative scheme reduced aeration volume by 16%, limiting efficiency losses to 5.5%. This work offers practical insights into optimizing wastewater treatment systems, providing data-driven strategies for enhancing energy efficiency and meeting stringent effluent standards.