Productivity, CO sub(2)/O sub(2) exchange and hydraulics in outdoor open high density microalgal (Chlorella sp.) photobioreactors operated in a Middle and Southern European climate

摘要

Two variants of open photobioreactors were operated at surface-to-volume ratios up to 170 m super(-1). The mean values for July and September obtained for photobioreactor PB-1 of 224 m super(2) culture area (length 28 m, inclination 1.7%, thickness of algal culture layer 6 mm), operated in Trebon (49 super([compfn])N), Czech Republic, were: net areal productivity, P sub(net) = 23.5 and 11.1 g dry weight (DW) m super(-2) d super(-1); net photosynthetic efficiency (based on PAR - Photosynthetic Active Radiation), eta = 6.48 and 5.98%. For photobioreactor PB-2 of 100 m super(2) culture area (length 100 m, inclination 1.6%, thickness of algal culture layer 8 mm) operated in Southern Greece (Kalamata, 37 super([compfn])N) the mean values for July and October were: P sub(net) = 32.2 and 18.1 g DW m super(-2) d super(-1), eta = 5.42 and 6.07%. The growth rate of the alga was practically linear during the fed-batch cultivation regime up to high biomass densities of about 40 g DW L super(-1), corresponding to an areal density of 240 g DW m super(-2) in PB-1 and 320 g DW m super(-2) in PB-2. Night biomass loss (% of the daylight productivity, P sub(L)) caused by respiration of algal cells were: 9-14% in PB-1; 6.6-10.8% in PB-2. About 70% of supplied CO sub(2) was utilized by the algae for photosynthesis. The concentration of dissolved oxygen (DO) increased from about 12 mg L super(-1) at the beginning to about 35 mg L super(-1) at the end of the 100 m long path of suspension flow in PB-2 at noon on clear summer days. Dissipation of hydraulic energy and some parameters of turbulence in algal suspension on culture area were estimated quantitatively.