Effect of aeration rates on hydraulic characteristics and pollutant removal in an up-flow biological aerated filter

Abstract

Biological aerated filters (BAFs) are an effective biological treatment technology for pollutant removal in municipal wastewater secondary treatment. However, one potential drawback of the BAF system is the need for an appropriate level of aeration. The appropriate level of aeration can reduce the energy consumption of the BAF system and improve wastewater treatment efficiency. In this study, an up-flow BAF reactor was established to study the effect of aeration rates on pollutant removal, hydraulic characteristics, dissolved oxygen (DO), and the microbial community. A computational fluid dynamics (CFD) model that combined the Euler–Euler model, porous media model and turbulence model was used to simulate the flow behaviour under a gas–liquid–solid three-phase system at aeration rates ranging from 40 L h⁻¹ to 90 L h⁻¹. The biofilm microbial community was analysed using high-throughput sequencing technology. The increase in the aeration rate reduced nitrogen removal and increased total phosphorus (TP) removal. The simulation results showed that the gas–liquid two phase velocity in the filter media layer exhibited an increasing trend with the aeration rates. The lower DO concentration at an aeration rate of 65 L h⁻¹ showed that the condition could improve the abundance and activity of the microbes. Planctomycetes, Nitrospirae and Proteobacteria were classified as nitrogen and phosphorus removing bacteria and were detected in all samples in the up-flow BAF. These results demonstrated that an aeration rate of 65 L h⁻¹ improved the pollutant removal efficiency by forming suitable DO and microbial community distributions. Optimizing the aeration rate can achieve efficient pollutant removal from the perspective of the flow field in an up-flow BAF.