The growth of as influenced by high CO and low O in flue gas from a silicomanganese smelter.

The aim of this study was to find an inexpensive and environmentally friendly CO source for growing the hydrogen-producing microalgae . The effect of different flue gas concentrations from a silicomanganese smelter on the growth of these algae at a photon flux density of 200 μmol photons m s applied 24 h day was studied. First, the algae were grown in a laboratory at 1.2, 6.8 and 17.1 % (/) pure CO gas mixed with fresh air. After 5 days of growth, the dry biomass per litre algal culture was slightly higher (17 %) at 6.8 % CO as compared to at 1.2 % CO. A further increase to 17.1 % CO decreased the biomass by about 40 %. Then, the flue gas from a silicomanganese smelter was used as a CO source for growing the algae. The flue gas was characterized by a high CO concentration (about 17 % /), low oxygen concentration (about 4 %), about 100 ppm NO and 1 ppm SO. The culture medium bubbled with undiluted flue gas contained about 490 mg L dissolved CO and 4.0 mg L dissolved O, while the lowest flue gas concentration contained about 280 mg L CO and 7.1 mg L O. Undiluted flue gas (17.4 % CO) decreased the biomass of the algae by about 40 % as compared with 4.8 % pure CO gas or flue gas diluted to a concentration of 6.3 % CO. Flue gas diluted to give 10.0 % CO gave less reduction in the growth of the algae (22 %). It was concluded that the high CO concentration itself caused the growth reduction and not the air pollutants, and the very low O concentrations in the growth medium could not counteract this negative effect.