Tingting Liu | ALES Graduate Seminar

A graduate exam seminar is a presentation of the student’s final research project for their degree.
This is an ALES MSc Final Exam Seminar by Tingting Liu. This seminar is open to the general public to attend.
Thesis Topic: Inactivation of Escherichia coli Using Electrochemical Disinfection with KIO4

MSc with Dr. Michael Gaenzle

Seminar Abstract:

Electrochemical disinfection of water has drawn attention in recent years as an alternative for conventional chlorine-based water treatment, due to the generation of toxic disinfection by- products (DBP) during chlorination, and increased antibiotics resistant, chlorine resistant and virulent E. coli strains found in chlorine treated wastewater. This study aims to investigate the stress factors involved in electrochemical disinfection using KIO4 as an experimental oxidizing reagent for bacteria inactivation. H2O2 and NaClO were selected as reference reagents. E. coli mutants lost specific genetic functions against environmental stress, or with addition of locus of heat resistance (LHR) were selected as tools for evaluation of this treatment method. E. coli strains were treated with oxidative stress and pH stress, separately or combined, to observe their patterns of behaviour. The results were then compared to electrochemical treatment. Reactive oxygen species (ROS) generated in each experiment group was measured using corresponding fluorescent probes. It was found that levels of oxidative compounds generated by KIO4 depended on the pH. In addition, shift in pH enhanced the effect of KIO4 when disinfecting E. coli, especially in alkaline pH. During electrochemical disinfection, electro-generated H2O2 by KIO4 was higher on the cathode chamber compared to that of anode, which resulted in higher inactivation of E. coli on the cathode. Chromosomally integrated LHR-positive mutant was found to have protective effect against alkaline stress. Current research provides supportive evidence that KIO4 catalyzes the generation of reactive oxidative components such as •OH, 1O2 and H2O2 that can inactivate E. coli and facilitate the process of electrochemical disinfection.