Foam Fractionation

A foam fractionator, also called a protein skimmer, removes dissolved and fine particulate organics from the water by adsorbing them onto fine air bubbles before they break down; it is sized on organic load rather than system volume.

It is one of the few processes that removes dissolved organics from the water entirely, rather than converting them into something else.

Where it’s used

Marine aquarium and zoo exhibits. Marine aquaculture and broodstock systems. Quarantine and holding. Anywhere with a high organic load and a saltwater environment.

Freshwater is the important limitation. Fractionation depends on stable fine bubbles, and seawater’s ionic strength is what makes those bubbles hold. In freshwater the process is substantially less effective. A fractionator specified on a freshwater system is usually a specification error worth catching early.

Why specification matters

Sizing follows organic load, not system volume. A heavily stocked exhibit needs far more fractionation than a lightly stocked one of the same volume. Feed input is the better proxy. Fractionators sized on volume alone are routinely undersized on the systems that need them most.

Contact time and bubble quality are the performance drivers. Column height, injection method, and air-to-water ratio determine how much contact happens. Venturi injection, downdraft, and spray injection designs achieve this differently and have different footprints and energy profiles.

Ozone is frequently injected here. The contact column is an efficient place to introduce ozone, which improves both fractionation and oxidation. It also means the fractionator becomes part of the ozone system, with all the material compatibility and residual control requirements that carries. This integration is often missed when the two are priced separately.

Waste collection needs a destination. Skimmate is concentrated organic waste. It needs a collection vessel, drainage, and cleaning access. This falls between trades more often than it should.

Height is a real constraint. Fractionators are tall. Equipment rooms with limited ceiling height rule out designs that would otherwise be the right choice. This is a constructability question worth answering before the equipment is bought.

How SIVAT helps

We size fractionation against organic loading rather than volume alone, confirm the application is one where fractionation performs, and check that ozone integration and skimmate handling are in someone’s scope.

We also check that the unit fits the room as drawn.

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Common questions

What does a foam fractionator remove?

Dissolved organic compounds, before they break down into ammonia and load the biological filter. Air injected into a contact column collects surface-active compounds on the bubbles, which carry them into a collection cup as foam.

Does foam fractionation work in fresh water?

Its effectiveness depends on water chemistry, and it is markedly more efficient in seawater than in fresh water. Freshwater systems generally rely on other means of organic control.

How is a fractionator sized?

On organic load rather than system volume. Two systems of identical volume with different stocking and feeding regimes need different fractionators.