An investigation of the mechanisms at the interaction between cavitation bubbles and contaminants

Project Information

CABUM

Grant agreement ID: 771567

DOI

10.3030/771567

Project closed

EC signature date 6 April 2018

Start date 1 July 2018

End date 31 March 2024

Funded under

• EXCELLENT SCIENCE - European Research Council (ERC)

Total cost

€ 1 904 565,00

EU contribution

€ 1 904 565,00

Coordinated by

UNIVERZA V LJUBLJANI
Slovenia

Periodic Reporting for period 4 - CABUM (An investigation of the mechanisms at the interaction between cavitation bubbles and contaminants)

Reporting period: 2023-01-01 to 2024-03-31

Summary of the context and overall objectives of the project

The CABUM project explores the phenomenon of cavitation, where bubbles appear in a liquid in case of a sudden decrease in pressure, which later collapse in a higher pressure area. It is a process that until recently was considered undesirable, because it causes noise, vibration and erosion in water machines. In recent years, however, under specific conditions, it has started to be used for the cleaning of surfaces, improvement of chemical processes, waste water treatment, and elsewhere.
The idea behind the CABUM project is based on the lessons we learned from the multi-year cooperation with the business sector. Clearly, gaps in the knowledge of the physical background of cavitation have been shown, which limit the introduction of this technology into advanced industrial processes.
The 5-year long project pursues a better understanding of the physical background of the phenomenon of cavitation, which could be used in the future for the environmentally friendly cleaning of drinking and waste water.

Work performed from the beginning of the project to the end of the period covered by the report and main results achieved so far

During the the project, we have deepened the basic understanding of cavitation in interaction with contaminants as well worked in on a more applied level which paved the path to commercialization of the technology.
One of the most ambitious goals of CABUM was to observe single bubbles in interaction with bacteria. We presented a method to study bubble-bacteria interaction on a nano- to microscale resolution in both space and time. We published a study of the effects of hydrodynamic cavitation on the inactivation of bacteriophage phi6, an enveloped virus used as a SARS-CoV-2 surrogate. Going deeper into the physics of the interaction we studied microbubbles near rod shaped structures that resemble bacteria geometry.
All the objectives of the action were successfully achieved - we improved the improve the temporal and spatial resolution of the experiments, determined when and how bacteria die when they are exposed to cavitation and concluded on the effects of bubbles have on viruses. Also we scaled up the process and developed a cavitation reactor which can efficiently treat large quantities of wastewater.

Progress beyond the state of the art and expected potential impact (including the socio-economic impact and the wider societal implications of the project so far)

Progress beyond the state of the art in several areas was achieved. Among other:
1. We developed a methodology which enables time resolved visualization of the shock waves in cavitating flows. These were predicted by simulations but never before visualized experimentally. Moreover, the methodology also enables to determine the magnitude of the pressure peaks.
2. We have amended the methodology for determining the radical production in cavitation. We found that the existing methodology, which was routinely used by researchers, significantly influences the cavitation dynamics, hence the results are not reliable.
3. Using numerical simulations we have pinpointed several candidates for the mechanical mechanisms, which could contribute most to the aggressive nature of cavitation against bacteria.
4. We have designed several, robust, test facilities, which enable studies at demanding conditions – high pressures, high temperatures, low temperature, aggressive fluids etc.. This confirms our group as the leader in the filed of cavitation exploitation studies.
5. We have identified the dominant mechanism of bacteria eradication by cavitation.
6. We have identified the dominant mechanism of virus inactivation by cavitation.
7. We have discovered a new mechanism of cavitation shedding.
8. We have discovered that the chemical activity of cavitation is related to single bubble dynamics.
9. We have discovered a new type of cavitation bubble collapse in broken symmetry conditions.
10. We have made the first observations of bubble bacteria interaction.
11. We have scaled up the process to develop a cavitation which efficiently treats water (in the scope of ERC PoC project CAVIPHY).

The idea behing the ERC CoG CABUM project