Stirring-induced vortex augmented ultrasonic cavitation for algae inactivation

Area of Science:

• Environmental Science
• Chemical Engineering
• Water Treatment

Background:

• Ultrasonication (US) is an eco-friendly, chemical-free method for algae removal.
• Standalone US application faces limitations due to low energy efficiency and weak cavitation effects.

Purpose of the Study:

• To investigate the synergistic effects of combining mechanical stirring with US for enhanced algae removal.
• To improve cavitation dynamics and reactive oxygen species (ROS) production for more effective algal treatment.

Main Methods:

• In situ measurements of cavitation pressure and ROS concentrations (hydroxyl radicals, superoxide radicals, singlet oxygen).
• Comparative analysis of algal physiological responses (photosynthesis, oxidative stress, cellular integrity, metabolism) under US alone versus combined US and stirring.
• Hydrodynamic field analysis to understand energy distribution and bubble dynamics.

Main Results:

• Combined system showed 1.71 times higher cavitation pressure than US alone.
• ROS concentrations were significantly amplified: hydroxyl radicals (84x), superoxide radicals (7x), and singlet oxygen (18x) compared to US alone.
• Combined treatment led to pronounced algal functional impairments, including disrupted photosynthesis, increased oxidative stress, compromised cellular integrity, and metabolic dysfunction.

Conclusions:

• Mechanical stirring synergistically enhances US efficacy by optimizing energy distribution and intensifying cavitation.
• The enhanced hydrodynamic field amplifies ROS production, leading to severe algal damage.
• This combined approach presents a scalable and sustainable solution for algal bloom mitigation.