Fine-Pore Diffuser Studies in BNR Wastewater: Performance Variation and Effects on Energy Footprint

Abstract

Fine-pore diffusers are the most common aeration system in municipal wastewater treatment plants. Fouling is inevitable and inexorable for all types of fine-pore diffusers, and is dependent on process layout, water quality, diffuser type, and time in operation, but independent of diffuser make and model. The decline in diffuser performance, resulting in increased aeration energy footprint is reflected onto the standard oxygen transfer efficiency (SOTE, ratio of oxygen transferred to the wastewater per unit oxygen blown by the aeration system, at standard conditions, %) and the net head loss across the membrane due the friction through the orifices, also known as dynamic wet pressure or DWP. In process water, the α factor is introduced to correct for the effects of wastewater, defining αSOTE(%). These parameters vary inevitably due to the fouling phenomena, with DWP increasing with time and SOTE decreasing. To account for the effects of fouling, a fouling factor F is introduced. Previously, we showed that the DWP increase is different for different materials, indicating different material properties and response with time in operation. Another indicator of diffuser performance is hence the pressure factor Ψ (ratio of DWP for used and new diffusers). This paper presents our 2-year diffuser study results and discusses the implications of our results on aeration energy footprint.