How does a DAF System Work?

Sep 5
14:24

2012

Bob B. Hamilton

Bob B. Hamilton

  • Share this article on Facebook
  • Share this article on Twitter
  • Share this article on Linkedin

The main purpose of a DAF or Dissolved Air Flotation system is to remove pollutants from water. This may include grease, oil, fats and colloids such as polymer latex, clay and silica particles. Read on to learn more about DAF Systems.

mediaimage
The main purpose of a DAF or Dissolved Air Flotation system is to remove pollutants from water. This may include grease,How does a DAF System Work?  Articles oil, fats and colloids such as polymer latex, clay and silica particles. The systems are commonly used in industrial settings; for example, chemical plants, paper mills, refineries and for overall water treatment. The process reduces chemical oxygen demand (COD).

The Process
The system works by sending part of the polluted water from the DAF tank into a air drum along with compressed air. The waste water is flooded with pressurized air and then re-circulated to the front of the tank where it passes through a pressure reduction valve. This creates minute bubbles as air is released from the water. These tiny bubbles attach themselves to the waste and it floats to the top of the water where it can be removed.

DAF systems are outfitted with a skimmer. This aids in removing the solid waste that floats to the top of the water. The ‘float’ is moved to a sludge hopper and from there it goes to another part of the system where it is processed. This processing method typically includes removal using a chain with flights or paddles and may also utilize a floor scraper. The solids are then collected for disposal.

DAF vs. Chemicals
Before DAF systems, the only way of treating wastewater was with chemicals. Coagulation was one method. This involves adding aluminum salts or iron to the water. When these chemicals are added they produce a positive charge neutralizing the negative charge of the pollutants in the water. This causes them to coagulate or bind together. This process is also known as flocculation. Large particles in the water generally sink to the bottom.

Although this method can remove many pollutants from water, it will generally retain germs. The coagulation method is thought to remove only between 27% and 84% of the bacteria present in water. After this method is used to remove substances from the water – especially in water treatment plants – a second step must be used. Adding chlorine is generally the second step for disinfecting the water as coagulation alone does not make it safe to drink.

The use of a DAF system is beneficial for the maximum removal of solids and reduces the amount of chemicals needed. The systems also provide a variety of other advantages including the reduction or elimination of odors, cloudiness and the presence of heavy metals.