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ARS Home » Southeast Area » Stuttgart, Arkansas » Harry K. Dupree Stuttgart National Aquaculture Research Cntr » Research » Publications at this Location » Publication #228583
Title: Sidewall-box airlift pump provides large flows for aeration, CO2 stripping, and water rotation in large dual-drain circular tanks

Author
item SUMMERFELT, STEVEN - FRESHWATER INSTITUTE
item Pfeiffer, Tim

Submitted to: International Conference on Recirculating Aquaculture
Publication Type: Abstract Only
Publication Acceptance Date: 6/1/2008
Publication Date: 7/25/2008
Citation: Summerfelt, S.T., Pfeiffer, T.J. 2008. Sidewall-box airlift pump provides large flows for aeration, CO2 stripping, and water rotation in large dual-drain circular tanks. Proceedings of the 7th International Conference on Recirculating Aquaculture. p.374-377.

Interpretive Summary: Conventional gas transfer technologies for aquaculture systems occupy a large amount of space, require a considerable capital investment, and can contribute to high electricity demand. In addition, diffused aeration in a circular culture tank can interfere with the hydrodynamics of water rotation and the speed and efficiency of solids fractionation to the tank’s bottom-center drain. Through a modification of traditional airlift design, a sidewall airlift pump attached to the 1.2 m tall fiberglass wall panel of a 3.7 m diameter circular tank was used to create a simple partial reuse system that was found to support rainbow trout (Oncorhynchus mykiss) at commercial densities (i.e., 80 kg/m3) and at a feed rate of 1% body weight per day without using supplementary oxygen beyond that supplied by the makeup water. Air was supplied with a 1/3 hp blower through three course-bubble cap diffusers at a submergence depth of 3 feet. The airlift pump generated approximately 440 gal/min of water flow and increased the water level at the top of the up-welling chamber by approximately 2 inches. Each pass through the airlift added 0.54 mg/L dissolved oxygen (O2) to the water while removing 1.6 mg/L dissolved carbon dioxide (CO2). Dissolved O2 and CO2 were maintained within the tank at 7.0 mg/L and 18 mg/L, respectively at a feeding rate of 8 kg/day.

Technical Abstract: Conventional gas transfer technologies for aquaculture systems occupy a large amount of space, require a considerable capital investment, and can contribute to high electricity demand. In addition, diffused aeration in a circular culture tank can interfere with the hydrodynamics of water rotation and the speed and efficiency of solids fractionation to the tank’s bottom-center drain. Through a modification of traditional airlift design, a new high water flow and low lift method of gas exchange was developed to address these important issues as well as to provide the impulse force for water rotation in circular tanks. A sidewall airlift pump attached to the 1.2 m tall fiberglass wall panel of a 3.7 m diameter circular tank was used to create a simple partial reuse system that was found to support rainbow trout (Oncorhynchus mykiss) at commercial densities (i.e., 80 kg/m3) and at a feed rate of 1% body weight per day without using supplementary oxygen beyond that supplied by the makeup water. Air was supplied with a 0.25 kW (1/3 HP) blower through three course-bubble cap diffusers at a submergence depth of 0.95 m, i.e., at the base of the airlift chamber. Water velocity measurements indicate that the airlift pump generated 1.7 m3/min (440 gal/min) of water flow as it increased the water level at the top of the up-welling chamber by approximately 5 cm. Each pass through the airlift added 0.54 mg/L dissolved oxygen (O2) to the water while removing 1.6 mg/L dissolved carbon dioxide (CO2). Dissolved O2 and CO2 were maintained within the tank at 7.0 mg/L and 18 mg/L, respectively. At a feeding rate of 8 kg/day, it was calculated that 0.29 kg O2/kg feed was being consumed by fish respiration. This oxygen use is within the accepted range of 0.25-0.35.