THE EFFECT OF SCREEN SIZES AND CULVERT WATER RETURN AREA ON PUMPING PERFORMANCE OF A PADDLEWHEEL WATER CIRCULATOR IN A SPLIT-POND TEST SYSTEM

The split pond system (SPS) has a similar concept to that of the partitioned aquaculture system (PAS), but its configuration is simpler. The SPS consists of two uneven sections divided by an earthen levee, and confines fish in the smaller section that typically comprises 15-20% of the total pond area. The remaining area functions as a large algal growth basin that provides oxygen production and waste treatment. Two water pathways equipped with screens connect these two pond sections, and a paddlewheel or other pumping device actively circulates water between the two sections. This SPS configuration enables farmers to have more flexibility in terms of culture management. Water mixing and circulation by pumping devices likely enhances carrying capacity of the split pond allowing for higher productivity. Thus, the system has become increasingly popular with farmers raising hybrid catfish in the US. Catfish yields from the SPS can range between 15,000 and 20,000 kg/ha, which is twice the yield obtained from traditional ponds. The use of SPS in the catfish industry has also sparked interest by other aquaculture sectors including: baitfish, shrimp, and largemouth bass producers. Utilizing SPS for the production of various species requires special design considerations in order to correctly implement the technology to meet each producer's specific needs. In general, characterization of how various design decisions, such as the size of water return culverts and various screen sizes, affect the operational efficiency of SPS would aid in their future design and implementation. This study aims to evaluate the effect of various culvert (culvert cross sectional area) and screen sizes (screen open area) on the pumping performance of a paddlewheel water circulator in a test SPS.

Two 0.1 ha ponds were retrofitted at the Aquaculture Research Station at the University of Arkansas at Pine Bluff with a slow rotating paddle wheel attached to a culvert (1.2 m diameter) and two culverts (1.2 m diameter) for return flow. Each set of culverts was attached to a screen box allowing for the insert and removal of various screen sizes for testing (0.64 x 0.64 cm, 2.54 x 1.27 cm, and 2.54 x 5.08 cm: 87, 76, and 74 % open area). Sets of baffles were constructed allowing for constriction and testing of various areas for return flow (0.28, 1.17, 1.45, and 2.34 m²). Each screen size and return culvert area was tested 24 times independently at 1, 3, 5, and 7 rpm while recording the following parameters: power consumption, water flow rate, and water head build up. The results of this study will give insight into the effects of screen size and culvert sizes for return water flow for consideration when designing future SPS. Initial results indicate that larger open areas in both screen and culvert sizes preformed more favorably with respect to power consumption, water flow rate and water head build. Detailed analysis of engineering data is currently ongoing.