Design of an airlift loop bioreactor and pilot scales studies with fluidic oscillator induced microbubbles for growth of a microalgae Dunaliella salina

This study was conducted to test the feasibility of growing microalgae on steel plant exhaust gas, generated from the combustion of offgases from steel processing, which has a high CO2 content. Two field trials of batch algal biomass growth, mediated by microbubble transfer processes in an airlift loop bioreactor showed only steady growth of biomass with 100% survival rate. The gas analysis of CO2 uptake in the 22001 bioreactor showed a specific uptake rate of 0.1 g/L/h, an average 14% of the CO2 available in the exhaust gas with a 23% composition of CO2. This uptake led to a steady production of chlorophyll and total lipid constituency in the bioreactor, and an accelerating exponential growth rate of biomass, with a top doubling time of 1.8 days. The gas analysis also showed anti-correlation of CO2 uptake and O-2 production, which along with the apparent stripping of the O-2 to the equilibrium level by the microbubbles, strongly suggests that the bioreactor is not mass transfer limited, nor O-2 inhibited. Removing O-2 inhibition results in high growth rates and high density of biomass. (C) 2011 Elsevier Ltd. All rights reserved.