Scaling-up of oxygenic photogranular system in selective-CSTR

The light driven oxygenic photogranule process presents potential aeration free wastewater treatment. Earlier attempts to scale up OPG in larger and deeper sequencing batch reactors were found difficult due to reduced light availability arising from slug entries of turbid wastewater and the accumulation of light-attenuating small biomass. Here, we investigated the use of surface-lit 120 L selective continuous stirred-tank reactors with an internal settler to treat municipal wastewater. The internal settler was deployed to continuously remove small, slow-settling biomass and enhance light availability within the reactor. This continuous-flow OPG system achieved mean effluent TSS of 32 ± 22 mg/L and soluble COD of 31 ± 14 mg/L. A similar reactor operated for 154 days had mean effluent TSS of 28 ± 24 mg/L and soluble COD of 38 ± 17 mg/L. More notably, granulation was maintained and propagated during the operation. Overall, high yields, 0.98 and 0.81 gCOD produced/gCOD consumed were achieved for reactor R1 and R2, respectively.