Views: 888 Author: Yosun Publish Time: 2025-11-14 Origin: Site
Oil–water separation is a critical process in various industrial applications, particularly in petrochemical plants, food processing, metal finishing, and wastewater treatment plants. The presence of oil in water can cause severe environmental pollution and disrupt biological treatment systems. Therefore, effective separation techniques are required to remove oil and suspended solids from waste streams. Among these methods, Dissolved Air Flotation (DAF) has emerged as one of the most efficient and space-saving technologies available.
Oil and water are immiscible liquids, meaning that they do not mix naturally. In industrial wastewater, however, oils can exist in free, emulsified, or dissolved form. Traditional settling tanks can remove large oil droplets, but finer or emulsified oils require advanced separation processes. The goal is to ensure that treated water meets discharge regulations or is suitable for recycling.
Dissolved Air Flotation (DAF) is a physical-chemical separation process that removes suspended solids, oil droplets, and other contaminants by attaching them to microbubbles. When pressurized air is dissolved in water and then released at atmospheric pressure, tiny bubbles are formed. These microbubbles attach to the surface of oil droplets and particles, reducing their density and causing them to float to the surface.
Pressurization: A portion of the clean effluent is saturated with air at high pressure.
Release: The saturated water is released into the flotation tank, forming microbubbles.
Attachment: The bubbles attach to oil droplets and solids, causing them to float.
Skimming: A mechanical skimming device continuously removes the floated sludge from the surface.
Clarified Water Outlet: Treated water is discharged from the bottom of the tank for further treatment or reuse.
High efficiency in removing oil and suspended solids
Compact design, ideal for facilities with limited space
Low operational cost and minimal maintenance
Suitable for a wide range of industries, from food processing to petrochemical
Produces clear effluent that meets regulatory discharge standards
Separating hydrocarbons and emulsified oils is essential before biological treatment or discharge. DAF systems are widely used here due to high oil and grease content in effluent streams.
DAF is used to separate fats, oils, and grease (FOG) from wastewater generated during meat processing, dairy production, and vegetable oil refining.
Cutting fluids and lubricants often contaminate process water. DAF helps remove these contaminants before recycling water or discharging it safely.
DAF is also used as a primary clarification method to remove algae, scum, and surface oils produced during warm seasons.
The performance of a DAF system depends on several design parameters, including:
Air-to-solids ratio
Bubble size (20–100 μm is ideal)
Hydraulic loading rate
Chemical coagulant and flocculant dosage
Skimmer speed and sludge removal frequency
Proper chemical conditioning is critical for emulsified oil removal. Coagulants such as alum or polymer flocculants are often added to increase particle size and enhance floatation.
DAF systems can reduce oil and grease concentrations from over 200 mg/L down to less than 10 mg/L, depending on influent conditions. The clarified effluent can be discharged safely or sent to secondary treatment systems for reuse in cooling towers or cleaning processes.
