February 15-18, 2009 Washington State Convention Center Seattle ...

EFFICIENT OXYGENATION FOR SUSTAINABLE AQUACULTURE
Dennis L. Mast, PhD
Clean Water Scientific, Inc
1121 Situs Court, Suite 120
Raleigh, NC 27606 USA
dmast@cleanwaterscientific.com
The technology made for Efficient Oxygenation is a device known as the “Add-o-mizer” and is specifically made for dissolving
gas into liquid. The Add-o-mizer is comprised of a pressure vessel or column for receiving a gas-entrained liquid via an inlet
and for injecting the gas-entrained liquid via a riser into a headspace of the vessel. A flow director is disposed in an upper portion
of the vessel or column to form a swirling flow path extending into a liquid pool in a lower portion of the vessel or column.
An outlet is provided to direct the liquid away from the vessel or column into a non-pressurized body of water
As the processed effluent is sufficiently supersaturated with oxygen, excess dissolved gas will flash to vapor or micron sized
bubbles upon return to the non-pressurized tank or basin. By controlling the level of super saturation, the size of these “microbubbles”
can be controlled to less than 5 microns in diameter - 0.005 millimeters! Slow rise rates of 0.2 to 0.8 cm/sec combined
with a surface-to-volume ration more than 1000 times higher than that for fine bubble diffusers. This makes microbubbles a
very efficient mechanism of oxygenation with minimal operating and maintenance costs.
The system under pressure can achieve dissolved oxygen (DO) levels far greater than possible with a mechanical aerator in an
open basin. The Add-o-mizer aerates by dissolving the feed gas into the water under pressure. This often makes aerating with
air, rather than oxygen, very cost effective.
Other types of aeration systems operate at relatively low efficiencies. As a result, air must be supplied in great excess in order
to ensure adequate dissolution of oxygen. With a (generous) oxygen transfer efficiency of 15%, a blower system must pump
374 cubic feet of air into water to dissolve 1 pound of oxygen. In order to dissolve the same 1 pound of oxygen into water, the
technology only needs to inject 11 cubic feet of air.
Benefits of this technology are efficient oxygenation, less feed requirements, shorter maturation cycles and healthier aquaculture
by using ambient air instead of being required to use liquid oxygen. If necessary, the tank/pond water can be sanitized
following each cycle/harvest without the need to replace all of the water by using the Add-o-mizer along with ozone as the gas
being entrained into the liquid.
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