Maritech CV

Even though low-power ultrasound generates less intense cavitation compared to high-power ultrasound, it still has notable applications in water purification.

Effects of Low-Power Ultrasonic Cavitation in Water Treatment

Ultrasonic cavitation occurs when sound waves create microbubbles in a liquid, which then collapse violently, producing localized high temperatures and pressures. Even at lower power levels, this process contributes to water treatment through several mechanisms:

1. Physical Effects

• Microstreaming & Shear Forces: The collapse of cavitation bubbles generates strong microstreams and localized turbulence, which enhance mass transfer and disrupt contaminants.
• Surface Cleaning: Low-power ultrasound can help detach biofilms and foulants from surfaces, reducing scaling and improving the efficiency of filtration systems.
• Particle Aggregation & Flocculation: Cavitation promotes the collision and aggregation of suspended particles, improving sedimentation and filtration.

2. Chemical Effects

• Radical Formation: While less pronounced than in high-power ultrasound, low-power cavitation can still produce reactive oxygen species (ROS), such as hydroxyl radicals (•OH), which help in breaking down organic pollutants.
• Enhanced Dissolution & Gas Exchange: Improves the dissolution of gases (e.g., oxygen) in water, aiding in oxidative degradation and biological treatment.

Applications of Low-Power Ultrasonic Cavitation in Water Treatment

Even at ≤40W, ultrasound can be effectively used in various water treatment applications:

1. Disinfection & Biofilm Control

• Low-power ultrasound helps in breaking microbial cell membranes, making bacteria and viruses more susceptible to disinfection by conventional methods (e.g., chlorine, UV).
• It can also prevent biofilm formation in pipes and filtration systems, reducing maintenance costs.

2. Turbidity Reduction & Flocculation Enhancement

• The shear forces from cavitation aid in the aggregation of fine particles, improving sedimentation and filtration.
• It enhances the effectiveness of coagulants, reducing the need for high doses of chemicals.

3. Removal of Organic Pollutants

• Cavitation-driven hydroxyl radicals help degrade organic contaminants, including pesticides, pharmaceuticals, and industrial waste.
• It can be used in combination with advanced oxidation processes (AOPs) for improved pollutant breakdown.

4. Heavy Metal Removal

• Ultrasonic cavitation aids in the formation of metal hydroxides, facilitating the precipitation of heavy metals like lead (Pb), cadmium (Cd), and arsenic (As).

5. Algae & Cyanobacteria Control

• Low-power ultrasound disrupts algal cells and prevents their proliferation in water bodies, making it useful for pond, lake, and reservoir management.

6. Aeration & Oxygenation

• Improves oxygen dissolution in water, which enhances biological treatment in wastewater systems (e.g., activated sludge process).

Limitations

• Lower efficiency compared to high-power ultrasound: Some contaminants may require prolonged exposure or combination with other treatment methods.
• Limited radical production: May need to be combined with chemical oxidants for effective organic degradation.
• Energy consumption: Even low-power ultrasound requires a continuous energy input, which may limit large-scale applications.

Conclusion

Low-power ultrasound can effectively enhance water treatment through cavitation-induced physical and chemical effects. While not as aggressive as high-power ultrasound, it still plays a valuable role in disinfection, biofilm removal, particle aggregation, organic pollutant breakdown, and aeration.

Its effectiveness can be improved when combined with other treatment processes like coagulation, oxidation, or biological methods, and that is our speciality.