Carbon and Nitrogen as Regulators of Algal Growth

Continuous flow algal cultures were grown under three different growth conditions using secondary sewage treatment plant effluent as the growth medium. The only variable within each run was the hydraulic residence time. The concentrations of growth regulating nutrients were varied between the runs so that comparisons of the algal mass, composition, nutrient uptake, and genera could be made. The importance of CO₂ availability of algal growth was also studied. The second phase of the study was a batch culture study in which the same growth medium was used as in Phase I. The objective of Phase 2 was to investigate significant similarities and differences between continuous and batch culture growth under otherwise similar growth conditions. Carbon dioxide enriched conditions produced as much as 10 times the algal mass as CO₂ deficient conditions. Algal blooms dominated by blue-green algae were found to be the result of a successional change from green to blue-green algae under CO₂ enriched, nitrogen limited conditions. In the batch culture study algae exhibited a luxuriant nitrogen uptake.