Skip to main content
ARS Home » Southeast Area » Stuttgart, Arkansas » Harry K. Dupree Stuttgart National Aquaculture Research Cntr » Research » Publications at this Location » Publication #228572
Title: The evaluation of oxygen and carbon dioxide transfer associated with airlifts in recirculating aquaculture systems

Author
item HEARN, RYAN - LSU
item Pfeiffer, Tim
item MALONE, RONALD - LSU

Submitted to: International Conference on Recirculating Aquaculture
Publication Type: Abstract Only
Publication Acceptance Date: 6/1/2008
Publication Date: 7/25/2008
Citation: Hearn, R.A., Pfeiffer, T.J., Malone, R.F. 2008. The evaluation of oxygen and carbon dioxide transfer associated with airlifts in recirculating aquaculture systems. Proceedings of the 7th International Conference on Recirculating Aquaculture. p.129-136.

Interpretive Summary: Airlifts in recirculating aquaculture systems (RAS) provide aeration, degasification, and water circulation. They allow the simplification of systems if designed properly, can reduce the capital costs, and minimize operation and maintenance associated with centrifugal pumping systems. To assist the utilization of an airlift with RAS the aeration and degasification capabilities for various size airlifts on loaded and non-loaded systems were evaluated. With these transfer rates known, the decision of supplemental gas aeration/removal requirements for aquaculture reuse systems can be made if needed. Under low head conditions, transfer rates for oxygen and carbon dioxide were measured for commonly sized PVC pipes ranging from 10.2 to 20.3-cm. In addition to various pipe sizes, parameters such as gas:liquid ratios, lift:submergence ratios, and flow rates were also manipulated for each airlift pipe size to evaluate their performance for gas transfer rates along with efficiency. Single airlift systems were implemented on 7.8m3 tanks, approximately 3-m in diameter and 1.2-m deep. Open tubing airlift units were constructed for each filter/tank combination and supplied with air from a regenerative blower for water movement through the filters. The system was designed to limit head loss conditions to a range from 15.2 to 45.7-cm. Data for this system indicates oxygen mass transfer rates ranging from 0.01 to 0.09 kg O2/hr based on airlift pipe. The CO2 transfer data is currently being evaluated.

Technical Abstract: Airlifts in recirculating aquaculture systems (RAS) provide aeration, degasification, and water circulation. They allow the simplification of systems, and if designed properly, can reduce the capital costs and minimize operation and maintenance associated with alternative pumping systems. In order to further assist the simplification of an airlift associated RAS, this research, based on ASCE standards, sought to evaluate the aeration and degasification capabilities for various size airlifts on loaded and non-loaded systems. With the ability to determine these rates, the decision of supplemental gas aeration/removal requirements for aquaculture reuse systems can be made if needed. Under low head conditions, aeration and stripping rates for oxygen and carbon dioxide were measured for commonly sized PVC pipes ranging from 10.2 to 20.3-cm. In addition to various pipe sizes, parameters such as gas:liquid ratios, lift:submergence ratios, and flow rates were also manipulated for each airlift pipe size to evaluate their performance for gas transfer rates along with efficiency. Concurrent single airlift systems were implemented on 7.8m3 tanks, approximately 3-m in diameter and 1.2-m deep. Open tubing airlift units were constructed for each filter/tank combination and supplied with air from a regenerative blower for recirculating water movement through the filters. The system was designed to mimic head loss conditions that are seen with PolyGeyser® biofilters, ranging from 15.2 to 45.7-cm. Data for this system indicates oxygen mass transfer rates ranging from 0.01 to 0.09 kg O2/hr based on airlift pipe.