Non-Thermal Plasma-Based Inactivation of Bacteria in Water using a Microfluidic Reactor
Laila Patinglag a, Louise Melling a, Kathryn Whitehead a, David Sawtell a, Alex Iles b, Kirsty Shaw a
a Manchester Metropolitan University, Chester Street, Manchester, United Kingdom
b University of Hull
Proceedings of Emerging Investigators in Microfluidics Conference (EIMC)
Online, Spain, 2021 July 20th - 21st
Organizers: Adrian Nightingale, Darius Rackus and Claire Stanley
Poster, Kirsty Shaw, 039
Publication date: 5th July 2021
ePoster: 

Waterborne infections, caused by opportunistic microorganisms, can be hugely detrimental to human health, particularly with a rise in the presence of multi-drug resistant bacteria [1]. Typical water treatments include the use of chemical disinfectants or physical filters but these have potential limitations in the production of toxic by-products, inefficiency at removing certain pathogens, and biofilm formation [2]. Non-thermal plasmas have gained significant interest as an effective treatment technology for economical and safe chemical-free disinfection of water, due to the formation of several reactive species such as hydrogen peroxide, ozone and hydroxyl radicals, in addition to producing ultra-violet (UV) radiation, which may inactivate bacteria [3]. Previous macroscale studies have shown effective reduction in bacterial numbers but are limited by mass transport and fluid control [4]. Here we present a microfluidic plasma reactor, using a dielectric barrier discharge in a gas-liquid phase annular flow regime, which is capable of reducing water treatment times from minutes/hours to just seconds. Microbiological analysis of water inoculated with antibiotic-resistant Escherichia coli and Pseudomonas aeruginosa was carried out before and after plasma treatment. Using air as the carrier gas, effective disinfection of water was achieved with both E. coli and P. aeruginosa with decreasing bacterial viability as residence time in the plasma increased. After 5 seconds of residence time in the plasma region, full inactivation of both bacteria (108 CFU/mL maximum number of each bacteria treated) as monoculture and mixed culture was achieved. Scanning electron microscopy revealed changes in cell morphology, while live/dead assays indicated that the membranes of the cells had been damaged following plasma treatment. Thereby demonstrating the potential for such microfluidic plasma reactors to be used in the rapid yet effective disinfection of microbially contaminated water.

LP received a Faculty of Science and Engineering Ph.D. Studentship funded by Manchester Metropolitan University. The authors would like also like to thank Hayley Andrews for the SEM images.

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