(322e) Use of Sodium Bicarbonate for Efficient Carbon and Water Management for Autotrophic Microalgae Cultivation in Open Pond System

Dissolved inorganic carbon including carbon dioxide(aq) and bicarbonate ion (HCO₃^-) is an essential carbon source for the autotrophic growth of microalgae.  However, the use of CO₂ gas only cannot provide a sufficient amount of dissolved inorganic carbon concentrations in a narrow pH window suitable for the growth.  In this study, sodium bicarbonate was used to increase dissolved inorganic carbon concentrations in conjunction with CO₂ gas.  Added CO₂ gas was able to suppress the increased pH values as a result of bicarbonate ion uptake and to supply additional dissolved inorganic carbon.  The fates of inorganic carbon and sodium ion were studied by taking mass balances for the two components.  The effects of sodium ion on CO₂ gas absorption and algal productivity will be presented for sustainable water reuse and autotrophic microalgal culture in a typical open pond system.  A preliminary economic analysis of the use of sodium bicarbonate based on the experimental results will also be presented.