How does the ultrasonic homogenizer devices sterilize wastewater?

How does the ultrasonic homogenizer devices sterilize wastewater?

The core sterilization mechanism of ultrasonic sonochemical devices in wastewater treatment is to utilize the sonochemical effect induced by ultrasound (especially the cavitation effect and its derived physical and chemical reactions) to disrupt microbial structures and inactivate their functions through multiple synergistic mechanisms. Compared to conventional ultrasonic homogenization devices, sonochemical devices emphasize the coupling of ultrasound and chemical processes, resulting in superior sterilization efficiency and applicability. The specific mechanisms are as follows:

1. The Core Driving Role of the Cavitation Effect
When high-frequency sound waves (typically 20kHz to 1MHz) emitted by ultrasonic sonochemical devices propagate through water, the periodic vibrations of the liquid generate countless tiny "cavitation bubbles" (bubbles containing gas or vapor). These bubbles rapidly expand under pressure fluctuations and then violently collapse (cavitation), forming the basis of sterilization.

Mechanical destruction: The intense shock waves (pressures reaching thousands of atmospheres) and high-speed microjets (speeds exceeding 100m/s) released instantly by the collapse of cavitation bubbles directly impact the cell membranes, cell walls, or viral capsids of microorganisms (such as bacteria, viruses, and algae), causing them to physically rupture. For example, when the peptidoglycan cell wall of bacteria is punctured, intracellular substances leak out; when the protein capsid of a virus is ripped apart, genetic material (DNA/RNA) is exposed and inactivated.

Local extreme environment: When a cavitation bubble collapses, it creates instantaneous high temperatures (5000K, approximately 4727°C) and high pressures (thousands of atmospheres), sufficient to directly "incinerate" microorganisms or damage their biomacromolecules (such as protein denaturation and nucleic acid chain breakage), rendering them unable to metabolize and reproduce. 2. Oxidative Effects of Active Species Generated by Sonochemical Processes

The extreme conditions of cavitation bubble collapse trigger the fragmentation and reaction of molecules in the water, generating a large number of highly oxidizing active species. This is the key chemical mechanism of sonochemical sterilization:

Hydroxy radicals (OH): Hydrogen molecules are broken down under high temperature and pressure to produce OH (with a redox potential of 2.8V, stronger than ozone and chlorine). These free radicals can:
Oxidize lipids (such as unsaturated fatty acids) in microbial cell membranes, disrupting membrane permeability and integrity;
Attack proteins (destroying amino acid structures) and nucleic acids (breaking DNA/RNA chains) within cells, inhibiting enzyme activity and genetic information transmission.
Other active species: If dissolved oxygen or oxidants (such as H₂O₂ or ozone) are present in the water, the cavitation effect promotes the generation of OH₂⁻ (superoxide anion) and H₂O₂, synergistically enhancing the oxidative sterilization effect.

3. Enhanced Sonochemical Synergistic Effects
The sterilization efficiency of sonochemical devices is often enhanced through synergistic effects, which is their core advantage over conventional ultrasonic devices:

Synergy with Chemical Agents: Ultrasound can enhance the decomposition of oxidants (such as H₂O₂ and ClO₂), promoting the production of more active species (for example, H₂O₂ is more easily decomposed into OH under ultrasound). Furthermore, the mechanical action of ultrasound allows agents to more easily penetrate microbial membranes, improving oxidation efficiency.
Synergy with Physical Methods: For example, when combined with ultraviolet (UV) radiation, ultrasound disrupts microbial structure, allowing UV radiation to more easily penetrate and damage nucleic acids. Combining with magnetic fields can enhance the cavitation effect and increase local energy density.

4. Targeted Inactivation of Different Microorganisms
Bacteria: The cell wall (peptidoglycan layer) and cell membrane are damaged by mechanical impact, while OH oxidizes membrane proteins, leading to leakage of intracellular substances and disruption of metabolism.
Viruses: The protein capsid is ruptured, and the internal nucleic acids (DNA/RNA) are destroyed by high temperatures or OH, rendering them incapable of infection. Algae: Cell walls and chloroplasts are destroyed, chlorophyll decomposes, and OH oxidizes metabolic enzymes, inhibiting photosynthesis and reproduction.
Drug-resistant microorganisms: Microorganisms resistant to traditional disinfection (e.g., chlorine) (e.g., Cryptosporidium) can still be effectively inactivated due to the non-specific physical destruction of ultrasound.
Summary
Ultrasonic sonochemical equipment achieves efficient sterilization through mechanical destruction via cavitation, physical inactivation in localized extreme environments, and chemical oxidation of active species, combined with synergistic effects from other technologies. Its core principle is to convert ultrasonic energy into physical impact and chemical oxidation. It offers zero secondary pollution, broad spectrum efficiency, and strong adaptability. It is particularly suitable for applications sensitive to disinfection byproducts or for treating complex wastewater (e.g., wastewater containing drug-resistant bacteria or high turbidity).

IV. Comparative Advantages over Traditional Sterilization Technologies
Compared to traditional methods such as chlorine disinfection and UV disinfection, ultrasonic homogenization sterilization offers the following advantages:

No secondary pollution: No chemical agents (such as chlorine) are required, and the production of disinfection byproducts (such as chloroform and other carcinogens) is avoided.

Broad-spectrum: Effective against bacteria, viruses, fungi, and algae, with particular effectiveness against chlorine-resistant microorganisms (such as Cryptosporidium and Giardia).

Synergy: Can be combined with other technologies (such as ozone and H₂O₂) to enhance cavitation and free radical generation, improving sterilization efficiency.

Summary: Ultrasonic homogenization utilizes the triple effects of mechanical impact generated by cavitation, extreme heat and pressure, and free radical oxidation to physically and chemically destroy the structure and function of microorganisms, achieving highly effective sterilization. Its core principle is to transform ultrasonic energy into a destructive force against microorganisms. This makes it particularly suitable for wastewater treatment applications involving microorganisms that are sensitive to disinfection byproducts or difficult to inactivate.