Aquaculture Magazine

February / March 2014

RK2: Skimmers as an option for Aquaculture Filters

Protein fractionators or “skimmers” as they are commonly called, when used in raising fish or shrimp will remove suspended particulates, organics, protein waste and yellow tints in the water.

At the same time protein fractionation (skimming) will lower the amount of bacteria and pathogens and increase the amount of oxygen. Traditional aquaculture filters, such as pressurized sand filters or cartridge filters remove particulates but do not remove protein waste and can actually increase the amount of bacteria and pathogens.

Water that is filtered through traditional filters is constantly running through the trapped bacteria and protein wastes. This is much like coffee filter, allowing bacteria, dissolved organics, and tints to return back to the holding system. The media in the filter functions as a bio-filter, promoting bacteria, which in turn removes oxygen. A result of this is that the discharge from these filters is generally loaded with bacteria and dissolved organics, and has reduced oxygen content.

The way a fractionator works is simple and highly effective. Air (and ozone) is injected into the bottom of the fractionator as tiny bubbles. The dirty water enters the top of the fractionator and exits out the bottom of the tank. As the tiny bubbles rise from the bottom they strip the organic waste and bacteria from the dirty water traveling downwards creating foam on the surface of the water. This foam loaded with unwanted waste is ejected from the cone section of the fractionator. Once in the clear collection top, it is washed away with the auto rinse system, keeping the riser area clean and prevents the foam from drying and inhibiting the foam removal process.

The use of ozone improves the fractionation process in a number of ways. Ozone oxidizes (or breaks down), many harmful pathogens, bacteria and virus’ allowing them to be easily removed by the fractionator. Ozone is very effective in removing color from the water, creating crystal clear water. When used in fractionation it will dramatically increase oxygen concentration. Ozone used in appropriate amounts for live holding systems is very safe.

The fractionation and ozone combination is extremely effective and available for a  variety of applications. Grow out tanks and those with heavy bio-loads become remarkably cleaner. Clean systems, such as larval or holding tanks become crystal clear. Protein fractionation with ozone is excellent for systems with heavy mucous concentrations, such as closed systems or semi open lobster, fish, shrimp and shellfish holding. Other applications include clean out, grow-out, aquaculture wastewater treatment as well as filtration of incoming water for open or semi-open systems.

The protein fractionation process increases water clarity and oxygen concentration, and also destroys and removes harmful pathogens. Therefore, appetite, stocking densities, feed and growth rates are all improved. Allowing for better animal health and improved product flavor.

Used in Aquaculture in the USA, Europe and Australia, as well as most major public aquariums worldwide, protein fractionators are a proven to be effective source of filtration for seawater, freshwater and brackish water systems, and are available in flow rates ranging from 10-2000 GPM.

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