Higher efficiency of CO2 injection into seawater by a venturi than a conventional diffuser system.

Mass production of microalgae generally requires the injection of CO(2) into open ponds or photo-bioreactors. The present study compares the CO(2) injection efficiency into seawater of a porous stone air diffuser and a venturi. CO(2) was injected at flow rates of 400, 700 and 1000 standard mL/min and 4, 7 and 10 standard L/min into a small and a large pond, respectively until the pH decreased from 7.8 to 6.8. No significant differences in CO(2) injection efficiency between the three CO(2) flow rates (p>0.05) were observed; however, CO(2) injection efficiency with venturi was about 100% (p<0.05) higher than that of the air diffuser. Therefore, it is possible to both reduce the cost and increase the effectiveness of CO(2) dissolution in seawater by using venturi operated at a lower flow rate, i.e. 400 standard mL/min in a small pond and 4 standard L/min in a large pond.