Dissolved Air Flotation
Dissolved air flotation (DAF) is a core physico-chemical pretreatment and advanced treatment technology, demonstrating exceptional removal efficiency for pollutants such as colloidal dyes, hydrophobic pigments, fiber oils, pretreatment greases, and suspended organic matter with poor biodegradability present in wastewater.
Working Principle
The principle involves generating a large number of fine bubbles (20-50 microns) through a dissolved air system. These bubbles efficiently adhere to pollutant flocs (such as dye molecules, colloids, and oils) formed after chemical coagulation, creating a "bubble-floc aggregate." This aggregate has an overall density lower than water, allowing for rapid flotation and separation.
In the textile dyeing industry, its core functions are highly efficient decolorization, oil removal, and COD reduction, demonstrating particularly significant effectiveness for light, colloidal pollutants that are difficult to remove by natural sedimentation.
Fine Bubbles
20-50 microns
20-50 microns
Decolorization
Oil Removal
COD Reduction
Design & Operational Features
Synergy with Chemical Coagulation
The efficiency of DAF heavily relies on preceding chemical coagulation. Targeted dosing of coagulants (PAC, PFS) and flocculants (PAM) destabilizes hydrophilic dyes and colloids, forming hydrophobic flocs easily adhered to by bubbles.
Precise Control of Key Parameters
Dissolved air pressure, recycle ratio, bubble size, and release system uniformity are crucial for separation efficiency. Surface loading rate is typically designed between 5-12 m³/(m²·h).
Adapting to Water Quality Fluctuations
Adapts well to water quality and quantity fluctuations from batch production in textile dyeing. Features quick startup and flexible operation.
Float Sludge Characteristics & Management
Float sludge has low moisture content (<97%) and small volume, but contains high concentrations of dyes and chemicals. Requires proper collection and dewatering treatment.
DAF Application Scenarios
Mainstream Pretreatment
Suitable for pretreatment of medium to dark-colored, high-concentration wastewater containing hydrophobic dyes
(disperse dyes, sulfur dyes, vat dyes), serving as an efficient primary physico-chemical treatment unit.
Advanced Post-Biological Treatment
Installed after biological treatment units, it serves as a safeguard process for advanced decolorization and removal of residual COD,
ensuring stable compliance of effluent color and SS.
Pretreatment for Specific Process Wastewater
Used for separate pretreatment of high-concentration, refractory wastewater streams such as
desizing wastewater and alkali reduction wastewater, significantly reducing their load before integration into the comprehensive treatment system.
Core Advantages
01
Exceptional Decolorization & Oil Removal
Achieves color removal rate of 80%-95%, one of the key technologies for solving the "color" problem, while also effectively removing oils that affect biological treatment.
02
Excellent & Stable Effluent Quality
Effluent has very low suspended solids and turbidity, providing high-quality, stable influent conditions for subsequent membrane filtration or biological treatment.
03
Significant Load Reduction
Effectively removes high molecular weight, poorly biodegradable colloidal organic matter, reducing shock load and treatment difficulty for subsequent biological units.
04
Small Footprint & Broad Adaptability
Relatively small footprint — particularly suitable for upgrading existing sedimentation processes or for situations with limited land availability.
The dissolved air flotation (DAF) unit is a powerful tool for tackling decolorization challenges and efficiently pretreating high-concentration, refractory wastewater. By removing a substantial portion of the pollutant load through physicochemical means before biological treatment, it serves as a core component for ensuring the stable operation of the entire treatment system and achieving compliance with discharge or reuse standards. Its effective synergy with the "coagulation" process is the critical technical factor determining the success of its performance.