Maggie Ntombifuthi Bingo (she/her), NexSys PhD researcher based at the University of Galway, is working on a project entitled ‘Experimental evaluation of air entrainment using liquid plunging jets’. We caught up with her in this Q&A.
Photo of Maggie Ntombifuthi Bingo
What is your NexSys research about and what are you working on at the moment?
Liquid jets striking the surface of a pool are often encountered in nature in the form of breaking waves and waterfalls. Plunging jets are extensively used across industries, including water and wastewater treatment, stormwater management, chemical reactors, and in hydraulic structures such as spillways and weirs. In many of these engineering applications, the characteristics and fluid dynamics of air entrainment are of utmost importance in the design and operation of infrastructure.
Given the widespread use of liquid plunging jets, advancing our understanding of the factors that influence air entrainment enables improved infrastructure design and operation. For my study, a liquid plunging jet system has been constructed to investigate how bubble dynamics and dissolved oxygen evolution are influenced by fluid properties (i.e. viscosity) and flow conditions.
How did you become interested in this research field?
In 2017, the Western Cape Province in South Africa, which is where I am from, experienced the worst drought ever since 1904. As a result, the City of Cape Town gradually enforced six levels of water restrictions on a population of approximately 3.8 million to control usage and avoid “day zero,” whereby the supply capacity would fall below the critical level of 13%. A household of four (parents and two children) was forced to reduce their household water consumption from 540L to 280L per day, approximately 135L to 70L per person per day. This is less than the (opens in a new window)133 L per person average daily water consumption reported for Ireland in 2019.
This experience triggered my interest in water and wastewater treatment. This led to me pursuing a Master of Engineering qualification focusing on the wastewater treatment of poultry slaughterhouse wastewater. My research evaluated the performance of a laboratory-scale integrated multi-stage poultry slaughterhouse wastewater treatment system.
Working in higher education, I understood that I would have to achieve a PhD in order to transition from a technical position to an academic position. Thus, I was looking for a PhD project that was within my research interest, water and wastewater treatment. I was also attracted by the vast experience of the supervisors overseeing this project, and the idea of living in another country and having new experiences.
What is one interesting finding from your research people may not know about?
An interesting finding from my research is how liquid viscosity (thickness and stickiness) and surface tension (how the surface of the liquid stretches or contracts) can significantly change how air gets entrained by liquid plunging jets. Many people think that the amount of air mixed in is only controlled by how fast or forcefully the water falls, but that’s not the whole story. For example, thicker liquids, like syrup compared to water, tend to create smoother, more stable shapes when they hit the surface of a receiving pool, while thinner liquids create more splashing and bubbles. This matters because air bubbles in water play an important role in nature and engineering—helping fish breathe, improving water treatment, and even reducing damage to structures by softening the impact of fast-moving water. Understanding these hidden effects helps engineers design better systems for everything from dams to wastewater treatment plants.
What is the wider relevance of your research to the energy transition?
An improved understanding of air/water interactions can become important for designing future infrastructure against changing rainfall patterns. Thus, using liquid plunging jet experimental systems is very useful for studying these interactions.
What is something people may find surprising about you?
I am a very talented sketch artist. In high school, I actually wanted to study graphic design, but my mom convinced me to study chemical engineering. During the Covid lockdown, I was commissioned to sketch a portrait for a wedding anniversary gift.
