Pumping performance of a modified commercial paddlewheel aerator for split-pond aquaculture systems.

摘要

The split-pond aquaculture system consists of a small fish holding basin that is connected to a waste treatment lagoon by two conduits. Split ponds require large water volumes circulated between the two basins (10,000-20,000 gal/min for 5-10-acre ponds) to remove fish waste and provide oxygenated water to the fish. Farmers producing ictalurid catfish in the USA have rapidly adopted this new technology to improve production efficiency. The original split-pond design used large, slow-rotating paddlewheels to circulate water; in this study, we evaluated paddlewheel aerators as pumps for split ponds. Pumping performance was evaluated at rotational speeds of 25-66 rotations/min and paddle submergence depths of 4.0, 6.8, and 9.5 in. Water flow rates ranged from 8,240 to 25,069 gal/min. Flows increased with increasing rotational speed and paddle submergence depth. Power input varied directly with flow rate and ranged from 1.08 to 8.28 hp. Water discharge per unit power input (i.e., pumping efficiency) ranged from 3,026 to 10,824 gal.min-1.hp-1; pumping efficiency decreased as water flow rate increased and as paddle submergence depth decreased. Placement of the paddlewheel at the channel inlet (with water being pushed through the channel) produced flow rates three times greater than placement at the outlet (with water being pulled through the channel). Our results show that commercial paddlewheel aerators can be modified, operated, and located to provide the water flows needed in commercial-sized split ponds. Although they are more expensive to operate than slow-rotating paddlewheels (which are specifically designed as water pumps), paddlewheel aerators offer the advantages of lower investment cost, greater availability, and easy maintenance. Long-term studies are underway to compare operational issues and costs associated with the use of various pump types, including paddlewheel aerators, in split-pond aquaculture.