english Core Principle of Color Removal
The key to color removal in dissolved air flotation is converting soluble or colloidal colored substances in water into a form that can be carried by air bubbles. Color in wastewater often comes from dye molecules, organic pigments, or metal ion complexes.
These substances often exist in the form of tiny particles or colloids, making them difficult to separate through natural sedimentation. Dissolved air flotation involves adding flocculants, causing the colored substances to react with the flocculants to form flocs.
Simultaneously, the tiny bubbles generated by the system tightly bind to the flocs, carrying them rapidly to the surface, thereby separating the colored substances from the water and reducing color.
Applicable Color Substances
Dissolved air flotation has varying effectiveness for different types of color substances and is more suitable for wastewater containing colloidal or suspended colored substances.
- Disperse dyes and reactive dyes in printing and dyeing wastewater
- Natural pigments in food processing wastewater
These substances easily bind to flocs formed by flocculants, which are then captured and separated by air bubbles.
However, for highly soluble, small-molecule colored substances that are difficult to form flocs, DAF alone is limited in effectiveness and requires synergistic treatment with other processes.
Process Optimization for Improving Color Removal
The color removal capability of DAF can be significantly improved by optimizing process parameters:
- Flocculant selection: Appropriately select the type and dosage of flocculant to ensure sufficient flocculation of colored substances, forming flocs of appropriate size and density
- Air system optimization: Adjust the dissolved air pressure and reflux ratio to generate sufficient and uniform microbubbles, enhancing the adhesion of bubbles to flocs
- pH control: Control the pH value to ensure that colored substances react more readily with the flocculant under suitable acidic and alkaline conditions, reducing the solubility stability of colored substances
These optimizations further improve separation efficiency and color removal performance.
Removal Performance in Practical Applications
The effectiveness of DAF for color removal has been demonstrated in actual wastewater treatment scenarios.
In wastewater treatment in industries such as:
- Printing and dyeing
- Papermaking
- Chemical engineering
DAF can significantly reduce wastewater color. DAF is often used as a pretreatment or advanced treatment unit to reduce the load on subsequent processes.
