Uptake pathway and continuous removal of nitric oxide from flue gas using microalgae

Nitric oxide (NO), a major constituent of NO, in fossil fuel flue gas, can be removed by the microalga, Dunaliella tertiolecta, in a bubble-column-typ e bioreactor. The uptake pathway of NO was investigated, and it was found t hat little NO was oxidized in the medium before its uptake by algal cells a nd that NO mostly permeated directly into the cells by diffusion based on t he mass balance of nitrogen and the change in nitrate and nitrite concentra tion in the medium in batch culture. For further application of this system , it is necessary to remove NO over a long duration, and the stability of N O removal is important. NO removal rate of about 50-60% could be maintained stably for 15 days in continuous culture under the light condition. Becaus e the consumption of nitrate was reduced by the amount of taken NO, NO rath er than nitrate is preferentially utilized as a nitrogen source for cell gr owth. Therefore, this algal system is useful for continuous NO removal and production of algal biomass using NO as a nitrogen source. (C) 2001 Elsevie r Science B.V. All rights reserved.