Types Of Aeration
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Perhaps the most common systems available include diffuser systems and fountains.  Diffusers work by introducing oxygen into the water through bubbles that rise up through the water from the lake bottom.  Unfortunately, according to Thomas Lawson, author of Fundamentals of Aquacultural Engineering, diffused aeration has not proven terribly effective in shallow lakes because the contact time of the air bubbles with the water is not great enough for sufficient oxygen transfer.1 

Fountains introduce dissolved O2 by creating oxygen transfer when water from the fountain hits the lake surface.  Though the most aesthetically attractive of the systems mentioned, fountain aeration is perhaps the least effective.  This is because water moving through the fountain system is taken from the top, healthiest layer and falls back into the same top layer.  Because the water is not redistributed, the depleted bottom layer is not affected.  

New on the horizon is a system call the venturi. The venturi aeration system causes a pressure differential that forms a vacuum, sucking air from the atmosphere into water captured from the lake bottom, mixed and pushed out at the surface level.  According to research, this helps, not only aerate depleted water, but also helps circulate the stratified layers.  The results indicate that venturi systems have a higher air and liquid injection efficiency compared to other aeration system. 2

Though nature has it own unique way of handling the distribution of oxygen within an aquatic system, sometime we find a little assistance is required when Mother Nature needs a helping hand.

 

	Diffuser	Fountain	Venturi
Power Requirements	6-12 amps	6-14 amps	3.3 amps
Oxygen Transfer Eff. 3	1.2-2.0	1.2	2.0-3.3
Rated Depth	8 feet min	Surface	1 to 20 feet
Coverage Area **	1/2 to 1 acre ft*	1/2 to 1 acre ft*	4 acre feet
Elec 24 hr .12 kwh	$1.90 - $3.80	$1.90 - $4.44	$1.05

** The oxygen transfer efficiency (OTE) of a diffuser system is a function of its depth in the ponds. Typically, an OTE of about 1.6% per foot of depth is found for fine bubble diffusers in a pond setting. For a lagoon with ten feet of depth, a transfer efficiency of about 16% could be expected. This means that 16% of the air added at a depth of ten feet will actively be transferred into the water while 84% will be excess and will bubble to the surface.

*Based on depth, shape and size of water body. Estimated from Kasco Marine
1 acre foot = 1 acre pond 1 foot deep.

1.  Lawson, Thomas B.. Fundamentals of Aquacultural Engineering. First Edition. New York: Chapman & Hall, Inc., 1997. pg. 283-284.

2.  Baylar, Ahmet, Fahri Ozkan, Mualla Ozturk. "Experimental investigations of air and liquid injection by venturi tubes." Water and Environment Journal. v.20 no.3. (2006) pg. 114-22.

3. Colt and Orwicz (1991)

4.D.E.P. Maine

Art Of Juggling Oxygen© - Shelly Steck