DAF wastewater treatment explained

Wastewater Treatment Plant

Dissolved Air Flotation (DAF) is a wastewater treatment process used in a wide variety of industries to treat industrial wastewater, to remove contaminants such as solids, fats and oils.

 

The DAF process involves dissolving air under pressure in a vessel, then releasing the air at atmospheric pressure into the DAF flotation tank.

 

Once the air is released, tiny air bubbles form and bond with the suspended matter, causing it to float to the surface. Once surfaced, this matter can be easily removed with a skimming device.

DAF Unit and Recycle System

Process

In the DAF process, untreated water is often fed into a chemical mix tank where it is treated with coagulants and flocculants to concentrate small particles into bigger clusters.

 

From the chemical reaction tank, the water passes through to the flotation tank where it is clarified.

 

Some of the clarified water leaving the flotation tank is pumped into an air vessel with compressed air, which dissolves the air into the water phase.

This ‘dissolved air’ water stream is then recycled back into the front of the flotation tank, flowing through a pressure reduction valve just as it enters the front of the float tank. This causes the air to be released in tiny bubbles, which form on the surface of any suspended matter in the wastewater and bond with them.

 

SWA Water’s DAF units employ a unique pressure air saturation pipe to create microfine air bubbles, which enhance the separation of solids, fats and oils from the water phase.

 

These bubbles eventually cause the matter to float to the surface, where it forms an easily removable layer of froth and leaves the treated and froth-free water to flow out of the flotation tank.

Wastewater Treatment Equipment

SWA Water’s DAF units

SWA Water has built hundreds of compact and highly efficient DAF units to suit every size factory, with more than 20 built in the past two years alone.

 

Our DAF units are suitable for a wide range of applications, including food, dairy, biodiesel, automotive, pharmaceutical, cosmetics and oil refineries.

 

Our compact DAF units not only require less space but yield a higher solids content in the sludge.

Importantly, our dissolved air system creates micro-fine flotation air bubbles using the unique SWA pressure air saturation pipe, allowing the separation of neutral density and heavy particles. Our DAF units are also capable of removing insoluble particles and oil/grease from a carrier water phase.

 

The DAF units are made with ease of use in mind, with DAF tanks, air saturators and pipework that are easy to drain and clean. Sampling valves offer easy and safe sample collection, weir plates are easily adjusted, and the pH probes are easily accessed, making every part of the process simple and easy.

 

We know that each of our clients will have different needs, so we offer design flexibility, full treatment integration and factory-made units from 1m3/h up to 500 m3/h, with larger units able to be constructed on-site.

SWA Water’s range

With their conservative design and superior materials, SWA’s DAF wastewater treatment units are known for their reliable and consistent performance and user-friendly operation and maintenance.

 

SWA Water offers a range of DAF units, in a variety of materials. With an array of customising options available, our DAF units are suitable for almost any industry.

Wastewater Treatment Equipment

Range of DAF units:

 

  • Industrial effluent treatment
  • Sludge thickening
  • Potable (drinking) water
  • Co-current and counter-current

 

Materials available:

 

  • Epoxy painted carbon steel
  • Stainless steel SS304 or SS316
  • Duplex or super duplex stainless steel tank bodies
  • Concrete tank bodies (constructed on-site)
Man walking at the Wastewater treatment Plant

Customising options:

 

  • Top and bottom scrapers
  • Integral reaction tanks
  • Screw conveyors
  • Totally enclosed and gas blanketed
  • Walkways
  • Scraper washing systems
  • Chemical treatment to enhance performance
  • Explosion-proof electrics

 

SWA also has a range of DAF units integrated with CPI Oil Separators, used in applications with high free oil and high suspended solids loadings, and where a very high-quality treated effluent is required (down to < 1 mg/l free oil).

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