The rate at which water flows through a floating raceway is critical to its function. Flow rate supports water quality by transporting dissolved oxygen into the raceway and removing waste. Flow rate may vary with design of the water-moving device and the use of screens. Screens ensure fish retention, but also create resistance to flow.
Three Superior Raceway Model 11000 floating raceways were installed in a 0.8 ha pond. Three types of devices were tested: grid airlift (GAL), aerator motor with propeller (AMP), and slow rotational paddlewheel (SRP). Trial 1 was conducted to obtain flow rate and energy consumption for each device pushing water through the raceway without screens in place. Trial 2 was conducted to measure the influence of mesh size (% open) on flow rate for devices tested in trial 1.
Screens (1.2m x 1.8 m) were placed at the inlet and outlet of each raceway. Screen mesh was rated by the percentage of open area: 100% (no screen), 80.8%, 76.4%, 73.8%, and 68% (1/2 inch mesh). Regression analysis of screen mesh and flow rate revealed R2 values of 0.94, 0.92 for GAL and AMP, respectively.