The Coupled Effect of Light and Iron on the Photogranulation Phenomenon.

Cyanobacteria occasionally self-immobilize and form spherical aggregates. This photogranulation phenomenon is central for oxygenic photogranules, which present potential for aeration-free and net-autotrophic wastewater treatment. Light and iron are tightly coupled via photochemical cycling of Fe, suggesting that phototrophic systems continually respond to their combined effects.

Photogranulation in a Hydrostatic Environment Occurs with Limitation of Iron.

Filamentous cyanobacteria are an essential element of oxygenic photogranules for granule-based wastewater treatment with photosynthetic aeration. Currently, mechanisms for the selection of this microbial group and their development in the granular structure are not well understood. Here, we studied the characteristics and fate of iron in photogranulation that proceeds in a hydrostatic environment with an activated sludge (AS) inoculum.