At the end of this module, you will be able to:
- 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
The following key questions are answered in this module:
Where are dissolved air flotation (DAF) systems used?
Common applications include clarification of municipal water and wastewater, and process water for tissue and papermaking operations.
What is done with the solids that are collected by a tissue machine DAF system?
They can be collected for re-use in the process, or sewered.
Is there a particular order in which coagulants and flocculants should be added?
Yes, coagulants should be added first, and then flocculants. The chemicals, addition rates, locations, and order should be carefully considered and jar tests can help determine the most effective process.
Where is the dissolved air added to the feed water to a flotation tank?
Compressed air is typically injected into a recirculated and pressurized water stream, that is mixed with the feed water to the flotation tank.
What is the difference between large rectangular flotation tanks and tall circular ones?
Rectangular units provide more retention time, while circular units use less space and can handle larger flows.
Below is a transcript of the video sample provided for this module:
Dissolved air floatation 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 floatation 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, process water, and wastewater 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 wastewater and process water in tissue and papermaking operations.
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