Views: 888 Author: Yosun Publish Time: 2024-11-14 Origin: Site
Dissolved air flotation (DAF) is a solid-liquid separation equipment through the micro-bubbles generated by the equipment and the contact of suspended matter in the sewage, so that the suspended matter quickly floated to the surface of the sewage to remove suspended matter in the water (including oil and grease and other fine particles that do not dissolve in water).
The feed water to the dissolved air tanks is usually flocculated with PAC or PAM flocculants to aggregate the particles into larger clusters.A portion of the clarified wastewater leaving the tank is pumped into a small pressure vessel (called a dissolved air tank) into which compressed air is also introduced. This results in the pressurized wastewater being fused with air. The water is circulated to the front of the float tank and flows through a pressure reducing valve as it enters the front of the float tank causing the air to be released in the form of tiny bubbles.The bubbles attach to the particles and as more bubbles form, the lift of the bubbles eventually overcomes gravity. This causes the suspended material to float to the surface, forming a foam layer which is then removed by the skimmer. Foam-free water leaves the float tank as a clarified effluent from the DAF unit.Some DAF design parallel plate packing to provide more separation surface, thus increasing the separation efficiency of the unit.
DAF is commonly used for drinking water supply that is particularly susceptible to single-cell pollutants, as well as for low turbidity and high color supply.After flocculation, the flocculated water flows into the DAF tank, and the air release device at the bottom of the tank instantly releases a large number of tiny bubbles, which adhere to the flocs and form floating suspended solids. Remove suspended solids from the surface using a scraper and pump clarified water from the bottom of the DAF tank.
The term "atmospheric" in the context of DAF typically refers to the release of the dissolved air at atmospheric pressure (after it has been pressurized in the system). This is a key part of the process, as it causes dissolved air to form microbubbles, which is crucial for the flotation process.
To summarize:
DAF uses dissolved air that is released at atmospheric pressure to generate microbubbles.
These microbubbles attach to particles, making them float and separate from the treated water.
This process is very effective for treating water that contains fine, emulsified oils or other difficult-to-remove contaminants.
Efficient solid Removal: The DAF system can effectively remove suspended solids and oil, even at low concentrations.
Compact design: They are usually more compact and require less space than other separation technologies such as sedimentation tanks.
High performance: The DAF system can process water with relatively high solid concentration and provide fast processing time.
Chemical use: In some cases, coagulants or flocculants can be added to enhance the flotation process, but in many cases, the system can operate without chemicals.
High operating costs: DAF systems are efficient, but they may be energy intensive, especially in generating bubbles and maintaining flotation processes.
Sludge disposal: The discharged sludge may be a difficult to treat waste stream that requires further treatment with other technologies or equipment.
Maintenance requirements: Components such as air compressors, pumps, and oil skimmers require regular maintenance to ensure reliable operation.
Wastewater treatment: DAF is commonly used to treat industrial and municipal wastewater by removing difficult to treat suspended large particulate solids and oils.
Drinking water purification treatment: Used in many large drinking water treatment plants, it can efficiently reduce the turbidity of water, remove organic matter and various algae contained in water.
Food and beverage processing: Used for wastewater containing a large amount of oil and fat generated during meat production and processing, dairy processing, and other processes
Classification of dissolved air flotation
There are three common types of air flotation machines: dissolved air flotation, vortex air flotation, and shallow air flotation. Dissolved air flotation machines are divided into two types based on water flow: horizontal flow and vertical flow. Many people don't know which type of air flotation machine to choose, and what are the differences based on the classification of air flotation machines? Here is a brief introduction:
QF Shallow Air Flotation
Layer air flotation is cylindrical, compact and shallow pool. Air bubbles are generated in the same way as dissolved air flotation machines, mainly because of their different shapes and structures.Shallow air flotation machines are widely used for the purification of various types of sewage and drinking water generated in daily life, as well as the pretreatment and deep treatment of industrial wastewater. It is mainly used for:(1) Desalination of seawater, (2) Removal of algae and reduction of turbidity in urban water or tap water, (3) Recovery of useful substances from wastewater, and (4) Petroleum and chemical industries. Wastewater treatment systems for industries such as textiles, printing and dyeing, slaughtering, papermaking, food, electricity, leather making, and steel.
SDAF Dissolved Air Flotation
The main structure of the vortex air flotation machine is: aeration device, air flotation device, chain scraper, and solid discharge machine. The shape is rectangular, and the bubbles are produced by the aeration head. Less investment, low price, but the effect is slightly inferior to the other two. The water quality requirements of the effluent are not high, you can choose the vortex concave air flotation machine.
Advection Pressurized Dissolved Air Flotation
Dissolved gas way for pressurized jet (internal not easy to clog), this kind of air flotation is currently more widely used in the country, the structure is also relatively simple, the site operation and installation is relatively simple, applicable to all types of industrial wastewater and municipal wastewater pre-treatment and part of the follow-up treatment.
Each type of DAF system is designed to optimize specific factors such as air bubble size, flotation time, and solids separation, depending on the application and the nature of the contaminants. Selection of the right type depends on factors like the water quality, flow rate, and space constraints.
