Sustainable removal of micropollutant from wastewater via sonochemical degradation with techno economic analysis and life cycle assessment

Thesis

Conventional wastewater treatment often fails to remove persistent antibiotic micropollutants like tetracycline, which spread antimicrobial resistance. This thesis comprehensively develops, optimizes, and benchmarks advanced oxidation processes (AOPs) for the eco-friendly degradation of these contaminants.

The work begins with the design and experimental validation of a novel sono-reactor system that utilizes TiO2 fractured nanoshells to enhance acoustic cavitation and radical generation. Through a detailed parametric investigation—including reaction time, acoustic pressure, pH, catalyst loading, and hybrid conditions—rapid tetracycline degradation was achieved (100% degradation from 5 mg/L in 5 minutes).

In the second phase, a process-level environmental evaluation was conducted using life cycle assessment to compare different experimental scenarios. It was found that while sono-based systems excelled in operational performance, they incurred high electricity-related emissions under current UK grid conditions. However, under projected 2050 green electricity scenarios, the environmental burden shifted toward catalyst synthesis. An improved continuous-flow system employing metal foam instead of synthesized nanoparticles was proposed, resulting in a significant reduction in CO2 emissions.

The third research phase expanded the analysis to a comparative LCA and techno-economic assessment (TEA) of five representative AOP technologies: sono-, photo-, sonophoto-, Fenton-, and electrochemical processes. The results showed that electricity usage (up to 83%) and catalyst synthesis (up to 98%) were dominant contributors to environmental impact. The sono-based method offered superior operational performance but high emission due to massive electricity consumption, while conventional Fenton processes exhibited low emission under present conditions (1.2 vs 0.478 kg-CO2/L).

By integrating experimental innovation with environmental and economic evaluation, this thesis provides a novel framework for guiding the development of AOP technologies for their effectiveness in pollutant degradation and life cycle sustainability. The outcomes emphasize a crucial shift in research perspective—from prioritizing performance alone to making environmentally-informed decisions in the design and implementation of future water treatment systems.

Authors: Zong, Z

• DOI: 10.5287/ora-7rrqq4j92
• Type of award: DPhil
• Level of award: Doctoral
• Awarding institution: University of Oxford
• Language: English
• Keywords: advanced oxidation processes; tetracycline degradation; techno-economic analysis; life cycle assessment
• Subjects: Environmental engineering; Chemical engineering