SRT-Dependent Phototrophic Growth and Population Changes in Chemostat Cultivation Using Wastewater
There is a renewed interest in using algae for wastewater polishing and treatment in recent years.
Because solids retention time (SRT) is a key design and operating parameter in bioreactor
operation, this research determined the effect of SRT on phototrophic growth and microbial
population dynamics in continuous flow chemostat systems. There was a unique feature of
phototrophic growth that differed from chemotrophic growth in chemostat. It was found that the
phototrophic biomass concentration increased proportionally as SRT increased from 3 to 9 d.
Regardless of the change in SRT, a step function model was successfully applied with the
predicted phototrophic production rate of 4.5 ± 0.9 g m-2 d-1 at the light intensity of 68.5 μmol m-2
s-1. Even though the continuous flow systems were initially seeded with a 1:1 mixture of green
algae and cyanobacteria, Chlorella vulgaris always dominated (98%) in the continuous flow
chemostat systems under steady-state conditions.
Keywords: Chlorella vulgaris; Microcystis aeruginosa; phototrophic growth; solids retention
time; continuous flow systems; chemostat