The present study addresses the behavior of gases in cultivation media as an essential factor to develop the relationship between the microorganisms that are present in the same environment. This relationship was explained via mass transfer of those gases to be a reasonable driving force in changing biological trends. Stripping and dissolution of oxygen and carbon dioxide in water and dairy wastewater were investigated in this study. Bubble column bioreactor under thermal control system was constructed and used for these processes. The experimental results showed that the removal of gases from the culture media requires more time than the dissolution. For example, the volumetric mass transfer coefficient for the removal of oxygen is 1.67 min-1 while the volumetric mass transfer coefficient for dissolution the same gas is 3.18 min-1. The same thing occurred with carbon dioxide, where the data showed that the volumetric mass transfer coefficient of the dissolution of CO2 is 0.66 min-1 while the volumetric mass transfer coefficient for removal process is 0.374 min-1. However, the two processes (dissolution and removal) with CO2 take more time than that with O2. Therefore, the production of gases due to metabolic processes in bacteria or microalgae remains in culture’s media for a certain period even if that media is sparged by air. Thus, this will give enough time for both microorganisms to consume those gases.
Keywords: Bioreactor, mass transfer, microalgae, aerobic bacteria
