Enhancing wastewater treatment efficiency through Venturi-assisted confined-tube aeration

The most efficient municipal wastewater treatment method is the activated sludge process, which consumes 1-2% of all electricity generated in the USA. The vast majority of this energy is consumed in the aeration process, where oxygen-rich water is required so that microorganisms can grow, multiply, and consume organic matter in the waste stream. Most new facilities use bubble diffusers, where air is forced through small membranes at the bottom of deep basins, creating tiny bubbles which slowly rise to the surface, transferring oxygen in the process.

The authors have developed a novel system which makes use of water pumps instead of compressors or blowers to deliver air to the wastewater stream. This device delivers high-pressure wastewater to a Venturi injector, which naturally draws air in at a constricted throat and sends the bubbly multiphase mixture to a coiled tube with a horizontal axis of rotation. The coiled tube exists to provide residence time for bubbles to transfer oxygen to water while reducing bubble coalescence widely observed in horizontal pipes. This work outlines recent computational efforts utilizing a discrete bubble model to predict aeration efficiency in such systems, with the goal of reducing energy usage in wastewater treatment.