Design and optimization of a novel airlift-driven sloping raceway pond with numerical and practical experiments

A novel airlift-driven sloping raceway pond (ALSRWP) was proposed in this study. In order to increase the mixing degree and decrease the energy consumption, airlifting system and the sloping channels were combined. CFD (computational fluid dynamics) was used to simulate the mixing and light regime in the ponds. The hydrodynamic characteristic of three types of ALSRWPs and the control that is a conventional raceway pond (RWP) was compared in detail. The results showed that the ALSRWP fitted with airlifting system and sloping channels (1.55°) increased the average fluid velocity, promoted the velocity along the light attenuation direction, reduced the energy consumption, and significantly eliminated the dead zone compared with the conventional RWP. Lastly, three trials of cultivation experiments with Chlorella pyrenoidosa were conducted. The results showed that the dry cell weight in type III ALSRWP was 27.14% (0.89 g L− 1) higher than that in the control pond (0.70 g L− 1). In addition, and Pa (biomass areal productivity) in type III ALSRWP (10.52 g m− 2 d− 1) was 37.34% higher compared with that in the control pond (7.66 g m− 2 d− 1), indicating that type III ALSRWP could produce more biomass than others ponds under the same culture condition.