Views: 888 Author: Yosun Publish Time: 2025-07-15 Origin: Site
A dissolved air flotation system (DAF) is one of the most widely used technologies in modern wastewater treatment, particularly for the effective removal of oils and greases. It provides an efficient and compact solution for separating suspended solids and insoluble organic matter from contaminated water streams. The technology is based on micro-bubble flotation, where air is dissolved into water under pressure and then released at atmospheric pressure to form tiny bubbles that adhere to impurities.
This method has proven especially useful in treating industrial effluents from food processing, petrochemical production, metal finishing, and municipal wastewater treatment plants. Our company manufactures and supplies robust DAF systems tailored for high-performance oil and grease removal in diverse applications.
Oils and greases (O&G) in wastewater originate from several industrial sources such as cooking oil, lubricants, fats, tars, and hydrocarbons. When discharged into treatment plants or natural water bodies, these substances:
Form surface films that prevent oxygen transfer
Interfere with biological treatment systems
Cause blockages in pipelines and pumps
Lead to unpleasant odors and environmental pollution
In many regions, strict discharge regulations set maximum allowable limits for oils and greases. Failure to meet these standards can result in environmental fines or plant shutdowns. This makes dissolved air flotation systems a vital tool for facilities needing to comply with effluent standards and maintain process efficiency.
The DAF system begins with a pressurized saturation tank where clean water is infused with compressed air. When this mixture is released into the flotation tank, the air comes out of solution as microscopic bubbles. These bubbles attach to oil droplets, grease particles, and fine suspended solids, increasing their buoyancy and causing them to float to the surface.
A skimmer mechanism then removes the floating sludge, while clarified water exits from the bottom or through a weir system. The process often incorporates chemical treatment to improve performance. Coagulants and flocculants are added upstream to bind fine particles and emulsified oils, forming larger aggregates that are easier to float.
To effectively remove oils and greases, a DAF system must include:
Pressurized air saturation system: Produces fine bubbles for effective attachment to light, hydrophobic contaminants.
Inlet mixing zone: Ensures even distribution of chemicals and bubbles.
Flotation tank: Designed to promote laminar flow and extended retention time for improved separation.
Surface skimmer: Mechanized scrapers that collect the floated sludge continuously.
Sludge hopper and pump: Transfers thickened sludge to further treatment or dewatering units.
Control panel with sensors: Enables precise adjustment of recycle rate, air pressure, and sludge discharge.
Our systems are fully modular, customizable in size and flow capacity, and include corrosion-resistant materials such as stainless steel for long-term operation in oily environments.
When it comes to handling wastewater containing oils and greases, the dissolved air flotation system offers clear advantages over traditional gravity separation methods:
High removal efficiency: Can remove up to 95–99% of free and emulsified oils with proper chemical pre-treatment.
Compact footprint: Ideal for space-limited installations.
Fast reaction time: Clarification achieved within 15–30 minutes.
Low energy demand: Compared to thermal or biological O&G removal systems.
Adaptability: Works well with varying O&G concentrations and flow rates.
Improved sludge handling: Produces float with lower water content, reducing sludge volume.
These benefits make DAF systems the preferred choice for industries with high-fat or oily wastewater discharge.
DAF units designed for oil and grease separation are commonly found in:
Meat and poultry processing: Where animal fats and proteins must be removed.
Dairy and cheese production: Which generate high concentrations of butterfat and milk solids.
Petroleum refineries and car washes: Where mineral oils and fuels enter the wastewater stream.
Industrial kitchens and food courts: Often discharge emulsified oils requiring pre-treatment before municipal discharge.
Textile manufacturing: Where lubricants and dye carriers must be separated from rinse water.
In each of these cases, DAF helps stabilize downstream biological treatment systems and ensures effluent compliance.
Emulsified oils are often the most challenging to remove. They do not float easily and resist separation due to surfactants or detergents present in the water. To address this, the DAF system is often paired with chemical treatment:
Coagulants (such as aluminum sulfate or ferric chloride) neutralize the electrical charge of particles.
Flocculants (such as polyacrylamide) bind the particles into larger flocs.
pH control enhances chemical reaction and bubble adhesion.
Our DAF systems are equipped with pre-treatment tanks, static mixers, and automatic dosing pumps to ensure reliable and consistent performance, even for complex emulsified oil scenarios.
Using a dissolved air flotation system for oils and greases management not only ensures regulatory compliance but also brings environmental and operational benefits:
Reduces downstream chemical usage in tertiary treatment
Improves efficiency of biological and membrane systems
Decreases odor generation and grease buildup in sewers
Enhances the potential for water reuse or recycling
By lowering pollutant loads early in the treatment process, DAF acts as a preventive measure, reducing the need for corrective interventions downstream.
