The most important part of a membrane photobioreactor set up is the connection of the membrane device to the photobioreactor, because it affects the CO2 supply and microalgae productivity. The CO2 gas can be saturated using a water column (Ferreira et al. 1998) or a gas mixer (Cheng et al. 2006; Fan et al. 2007). Each open­ing between the CO2 tube and the membrane fittings of the system must be sealed with rubber caps and tape to avoid gas releases to the surroundings and gas exchanges between the system and the surrounding air. The CO2 value can be measured directly by a CO2 meter or integrated with a chromatography system for direct measurement of DO and CO2 (Cheng et al. 2006; Fan et al. 2007). The indirect method is mea­sured by stoichiometric equation of pH value and NaOH solution (Carvalho and Malcata 2001; Fan et al. 2008).