Foam Fractionators / Protein Skimmers

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What Is Foam Fractionators / Protein Skimmers?

A foam fractionator is a fine particle method of filtration which coagulates finer particles using fine bubbles to concentrate into foam on the surface of a water body which can easily be removed. They are also known as protein skimmers. This is sometimes seen in nature on beaches during wild weather or a storm particularly after heavy rain, where the churning waves produce the same foam as the waste from the foam fractionator. This foam is generally not safe to play in!!

How They Operate

Dirty water is introduced to the top of the reaction chamber via pump or gravity fall. This travels downward to the outlet at the bottom. A side loop pump introduces air or air + ozone into the base of the chamber via a venturi injector. These two loops create a counter current of water flow down and fine air bubbles upwards. As the air bubble rise through the column, it attracts fine particles to the bubbles and becomes more concentrated as it rises to the top cup. The foam overflows into the cup (as per picture) and collects here until an automatic backwash of water spays cleans and empties the dirty foam to waste. Clean water exits through the bottom of the unit and through the side riser via gravity.

System Position
Foam Fractionators are flexible in their positioning. Normally they are used as the primary filtration in low intensity/ low feed systems (such as research, life support or aquarium systems). Alternatively, they can be positioned after primary filtration (such as drumfilters) on more intensive saltwater recirculating aquaculture systems.
Sizing
To size a foam fractionator, we require several pieces of information:
  • Salt or freshwater system
  • Type of system and intensity (feed, biomass etc)
  • System Flow Rate
  • Min and Max exchange rate of system volume per hour
The exchange rate is dependent on what the system is being used for: