es0c07374_si_001.pdf (571.79 kB)
Photogranulation in a Hydrostatic Environment Occurs with Limitation of Iron
journal contribution
posted on 2021-07-13, 19:15 authored by Abeera
A. Ansari, Arfa A. Ansari, Ahmed S. Abouhend, Joseph G. Gikonyo, Chul ParkFilamentous 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. We found that the level of Fe in
bulk liquids (FeBL) sharply increased due to the decay
of the inoculum but quickly diminished along with the bloom of microalgae
and the advent of the oxic environment. Iron linked with extracellular
polymeric substances (FeEPS) continued to decline but reached
steady low values, which occurred along with the appearance of granular
structure. Strong negative correlations were found between FeEPS and the pigments specific for cyanobacteria. Spectroscopies
revealed the presence of amorphous ferric oxides in pellet biomass,
which seemed to remain unaltered during the photogranulation process.
These results suggest that the availability of FeEPS in
AS inoculumsafter algal bloomselects cyanobacteria,
and the limitation of this Fe pool becomes an important driver for
cyanobacteria to granulate in a hydrostatic environment. We therefore
propose that the availability of iron has a strong influence on the
photogranulation process.