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The effect of seed sludge on the selection of a photo-EBPR system

Carvalho, V.C.F., Freitas, E.B., Fradinho, J.C., Reis, M.A.M., Oehmen, A.
New biotechnology 2019 v.49 pp. 112-119
acetates, activated sludge, air, autotrophs, microorganisms, oxygen, phosphorus, photophase, photosynthesis, propionic acid, scotophase, wastewater treatment
The phototrophic-enhanced biological phosphorus removal system (photo-EBPR) was recently proposed as an alternative photosynthetic process to conventional phosphorus removal. Previous work showed the possibility of obtaining a photo-EBPR system starting from a culture already enriched in polyphosphate accumulating organisms (PAOs). The present work evaluated whether the same could be achieved starting from conventional activated sludge. A sequencing batch reactor inoculated with sludge from a wastewater treatment plant (WWTP) was fed with a mixture of acetate and propionate (75%:25%) and subjected to dark/light cycles to select a photo-EBPR system containing PAOs and photosynthetic organisms, the oxygen providers for the system. The results showed that it is possible to obtain a photo-EBPR system starting from a WWTP sludge, although the process is slower than when started with a sludge already enriched in PAOs. After 15 days of operation, the system could remove 60 ± 2 mg-P/L of phosphorus (approximately 67% of the concentration at the end of dark period) in the light period, from which 13 ± 1 mg-P/L was removed during the phase without external air supply. These results indicate that a photo-EBPR system can be obtained independently of the seed sludge initially used, provided that a suitable operating strategy is implemented, i.e. by imposing conditions that favour the growth and coexistence of PAOs and photosynthetic microorganisms.