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Based on: Industry Standards and Best Practices

Languages: English

Sample Transcript

Dissolved air flotation, or DAF, is a water treatment process that removes suspended solids from water using air. This separation is achieved by dissolving air into water under pressure and then releasing the air at atmospheric pressure in a flotation tank. The released air forms tiny bubbles which adhere to the suspended solids in the water causing the solids to float to the surface where they can be removed by a skimming mechanism. Chemicals can be added to the feed water to improve solids removal. The DAF process can be used to clarify fresh water, processed water, and waste water so that it is suitable for use or discharge. In some cases, the solids are collected for reuse. Common applications include clarification of municipal water and waste water and process water in paper making operations.

Dissolved Air Flotation (DAF) Systems

Training Time: 15 minutes

Dissolved air flotation (DAF) is a water treatment process that removes suspended solids from water using air. This separation is achieved by dissolving air into water under pressure, and then releasing the air at atmospheric pressure in a flotation tank. This module will describe common applications of the dissolved air flotation (DAF) process and the main steps of the DAF process.

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Training Content + Interactive Quizzes

Fiber particles, microflocs and flocs of fibers collect on rising air bubbles in DAF separation clarifiers

Separated material collects on the surface of DAF clarifiers and is skimmed to one end for disposal

Sometimes the feed stream to a DAF clarifier is prescreened to remove the larger sized particulate material

Learning Objectives

  • Describe common applications of the Dissolved Air Flotation (DAF) process
  • Describe the main steps of the DAF process
  • Describe the equipment utilized in a DAF system
  • Identify chemicals commonly used as coagulants and flocculants in DAF systems
  • Describe coagulant and flocculant chemicals used in DAF systems
  • Identify hazards associated with DAF system
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Dissolved Air Flotation (DAF) Systems FAQs

How are tiny fiber fines removed from suspension in a dissolved air flotation system?
Tiny fibers attach to small air bubbles and are carried to the surface of the DAF clarifier.

What types of chemicals are added to the DAF process to assist in particle separation?
Coagulants and flocculants can be added to DAF units in order to increase their separation efficiency.

What is the purpose of prescreening ahead of DAF units?
Prescreening the feed stream to a DAF unit reduces the solids loading on the unit.

Where in the DAF unit is new feed added?
Incoming feed is released at the bottom of the unit, giving a chance for dissolved air bubbles to form and collect suspended particles as they rise.

What happens to the separated material that floats to the top of a DAF unit?
Separated material is skimmed from the surface of the DAF unit. If the unit is treating paper machine white water the float may be recycled.

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