A NEW TUBULAR REACTOR FOR MASS-PRODUCTION OF MICROALGAE OUTDOORS

A novel reactor for outdoor production of microalgae is described. Air-lift is used for circulation of the culture in transparent tubes lying on the ground and interconnected by a manifold. Dissolved O2 is removed through a gas-separator placed 2.0 m above the tubes and water-spray is used for cooling. The manifold permits short-run durations between leaving the gas separator and re-entering it, preventing thereby damaging accumulation of dissolved oxygen. Day temperature control in summer is attained using water-spray. In winter, temperature in the tubes rises rapidly in the morning, as compared to an open raceway even if placed in a greenhouse. The number of hours along which optimal temperature prevails in the culture throughout the year increased significantly. Very high daily productivity computed on a volumetric basis (e.g. 550 mg dry wt l - 1 culture) was obtained and preliminary observations indicate that a significantly higher output, e.g. 1500 mg dry wt l - 1 d - 1, is attainable. Much more research is required to assess the year-round, sustained productivity attainable in this reactor.