It is used to remove suspended solids from waste water. These solids float after being attached to small air bubbles. The process is simple. Air is dissolved in water under pressure. Then the pressure is released. Small bubbles form and rise. The bubbles stick to solids. Solids and bubbles float to the top. A skimming device removes them.
The system is used in treatment plants.
It works with domestic and industrial wastewater. It is good for removing particles that do not settle easily. These particles include oil, grease, and fine solids. In food factories or oil refineries, the water has many light materials. These materials float better than sink. So the DAF system is helpful here.
Before the air is added, chemicals are used. Coagulants and flocculants help the particles join together. Then it is easier for air bubbles to lift them. The water is pumped through a pressure tank. Air is added. The water becomes saturated with air. When it enters the flotation tank, the pressure drops. The air leaves the water as bubbles. The bubbles move up and carry particles to the surface.
The surface layer contains the waste. It is removed by a skimming blade. The clean water goes to the bottom and flows out. Some of this water is recycled. It goes back to the pressure tank to help create bubbles again. This cycle repeats.
This method is used in many treatment systems.
It is used before biological treatment. It is used in systems that treat domestic wastewater and industrial wastewater. It can be used in desalination plants to protect reverse osmosis membranes. Algae and fine solids are removed first.
A DAF system helps lower oxygen demand.
It reduces biochemical oxygen demand (BOD) and chemical oxygen demand (COD). These are important because too much BOD means too much organic matter. It harms fish and plants. With less BOD, water is safer.
The DAF unit is often compact. It fits into small spaces.
It can treat high flow or low flow, depending on the design. Some systems are round. Some are rectangular. Round units take less time. Rectangular ones take longer.
In some cases, nitrogen gas is used instead of air. This is done in oil and gas fields. Using nitrogen avoids explosion risks. These are called dissolved gas flotation systems.
The sludge removed by skimming may need dewatering. This is done with a filter press or screw press. The goal is to remove water from the sludge. The dry solids are easier to manage. This reduces waste disposal cost.
A dissolved air flotation system is flexible.
It treats water before it enters rivers or is reused. It can handle different types of suspended solids. It is often used with other treatment steps. It works well in systems that remove oil, grease, or organic solids.
In water treatment plants, DAF systems are common. They help produce clarified water. This water can meet environmental standards. It can be used again or safely released.
