A process of growing a culture of cyanobacteria or algae using chitin or chitosan as a source of nitrogen for photosynthetic growth is described. This process can be used to remove pollutants from nitrogen-deficient natural waters or wastewaters including buchu mercaptan production wastewater. Biomass that results from photosynthetic growth on chitin can be used, either as whole cells or the isolated components of the cells, for a large variety of commercial purposes.