The 2017 summer field trials focused on the utilisation of the airlift pump in aquaculture settings. The purpose of these field trials was to test the pumps in different environments and observe their performance in water circulation as well as aeration.
Aqua-Cage Fisheries located in Parry Sound, Ontario; is a fish farm that implements an open net approach to producing fish. This method includes growing fish inside nets that are then dropped into a lake. In the winter months, the cages are tied to the shore where de-icer blades are used to keep the area used from icing over. Whereas in the summer, the cages are moved further into Georgian bay lake where the nets are dropped further down and more fish are added into the nets. This approach allows the fish to grow in an open lake atmosphere rather than a more controlled setting such as raceways or recirculating tanks.
The airlift pump application in this setting was to see how effective the pump could be for de-icing applications in the winter time, while testing its upwelling performance for the summer season. The pumps would deposit the water at a velocity that would deter the ice from forming on the surface of the lake, while pumping water from deeper in the lake to the surface. This trip was conducted in the month of June of 2017, and so the upwelling application was tested, but the water velocity at the exit elbow and the surface water velocity was also recorded for later studies. The airlift pumps used were the 4-inch and 6-inch pumps, with varying suction lengths to study its effect.
Lyndon Fish Hatcheries
Lyndon Fish Hatcheries in the town of New Dundee, Ontario is a trout farm that produces trout eggs and fingerlings. The farm currently contains 52 tanks with 4 different systems of maintaining their fish. The owner, Clarke, is interested in implementing the new airlift pumps in 17 out of the existing 52 tanks. The 4 different arrangements currently in place include the circular tanks, the smaller tanks for hatcheries and 2 raceways, one with baffles and the other without. This field trial occurred in the month of July 2017 where the airlift system was implemented and tested in the circular tanks and the segmented raceway.
The current system in the circular tanks consists of 2 inflow pipes, an air stone system and a central drain. The air stone is located 20” beneath the water level and a liquid oxygen tube is used to supply oxygen to the tank. By placing two 4” airlift pumps in this system, a more efficient method of providing proper water circulation and aeration can be achieved. As for the segmented raceways, they operate using an inlet to provide flow, where the baffles are then used to increase the velocity. When the flow rate is lower than desired, two carry pumps are used to pump water from the exit of the raceway back to the start. However, the carry pump usage has been reduced due to unwanted solid waste being pumped through out the raceway. This is where the installation of an airlift pump can provide the proper strength to maneuver the raceway water as needed.
McMillan Pitts is a gravel mining bed that has been adapted to a manmade lake located in Aberfoyle which is a 20 minute drive from the University of Guelph’s campus. The McMillian construction company has taken advantage of this and established a rainbow trout aquaculture facility with high grade equipment and blowers. The McMillian Company have allowed the Gryph Energy team to run experiments to capture data on the performance of the airlift pumps and the affects of raceway setups for aquaculture. The pumps located at the lake are tested improved air injection airlift pumps that have axial and radial air injection. This technology is patented by our team leader Dr. Wael Ahmed.
The Pitts have 6 larger raceways and recently installed two smaller raceways. Two frames were built for two different types of testing. A frame built for performance testing and a frame built for raceway velocity testing. For performance the 2”, 4”, 6”, and 8” airlift pumps were tested all at the same submergence ratio of 0.85 and the same total length of 82”. The aim for the performance data collecting is to compare the effect of the diameter of the airlift pump under the exact same conditions. Water was collected, weighted and timed of collection was recorded. A minimum to maximum possible range of air flow rates were injected into the axial and radial injectors and data was collected multiple times for each run tested. The limiting factors for the maximum airflow rate possible were the blowers and the pressure drop from the lines. The data collected from these test were also compared to a theoretical model for airlift performance.