Date of Award

August 2024

Degree Type

Thesis

Degree Name

Master of Science

Department

Engineering

First Advisor

Ryochi S Amano

Committee Members

Yongjin Sung, Qian Liao

Keywords

best operating point, bubble size, membrane diffuser, oxygen transfer, spar mixer, wastewater aeration

Abstract

Wastewater aeration plays a critical step in reducing the environmental harms associated with anthropogenic waste. Aeration energy costs are estimated between 45-75% or 30-76% of total process costs. [1, 2] Here, we demonstrate a surface-mounted rotating diffuser (i.e. spar mixer, gas-inducing impeller) intended to augment existing bottom-mounted membrane diffuser arrays. Low-cost materials (PVC pipe, carbon fiber epoxy composite) are combined into a spar mixer which produces smaller bubbles while using less power and achieving faster oxygen transfer rates than a membrane diffuser. Spar mixer variants are explored, and their performance ranked according to the ratio of oxygen transfer kinetics versus power consumption. Best operating points (BOP) are benchmarked across variants including square-ends, notches and slots, all of which outperform a membrane diffuser in a controlled laboratory setting. By decoupling local oxygen transfer from global mixing, this spar mixer approach augments operational aeration tanks - cost-effectively expanding capacity with minimal downtime.

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